liu.seSearch for publications in DiVA
Change search
Refine search result
1234567 1 - 50 of 334
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Rows per page
  • 5
  • 10
  • 20
  • 50
  • 100
  • 250
Sort
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
  • Standard (Relevance)
  • Author A-Ö
  • Author Ö-A
  • Title A-Ö
  • Title Ö-A
  • Publication type A-Ö
  • Publication type Ö-A
  • Issued (Oldest first)
  • Issued (Newest first)
  • Created (Oldest first)
  • Created (Newest first)
  • Last updated (Oldest first)
  • Last updated (Newest first)
  • Disputation date (earliest first)
  • Disputation date (latest first)
Select
The maximal number of hits you can export is 250. When you want to export more records please use the Create feeds function.
  • 1.
    Abidin, Aysajan
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Pacher, Christoph
    Austrian Institute of Technology, Austria.
    Lorünser, Thomas
    Austrian Institute of Technology, Austria.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Peev, Momtchil
    Austrian Institute of Technology, Austria.
    Quantum cryptography and authentication with low key-consumption2011In: Proceedings of SPIE - The International Society for Optical Engineering, 2011, p. 818916-Conference paper (Refereed)
    Abstract [en]

    Quantum Key Distribution (QKD - also referred to as Quantum Cryptography) is a technique for secret key agreement. It has been shown that QKD rigged with Information-Theoretic Secure (ITS) authentication (using secret key) of the classical messages transmitted during the key distribution protocol is also ITS. Note, QKD without any authentication can trivially be broken by man-in-the-middle attacks. Here, we study an authentication method that was originally proposed because of its low key consumption; a two-step authentication that uses a publicly known hash function, followed by a secret strongly universal2 hash function, which is exchanged each round. This two-step authentication is not information-theoretically secure but it was argued that nevertheless it does not compromise the security of QKD. In the current contribution we study intrinsic weaknesses of this approach under the common assumption that the QKD adversary has access to unlimited resources including quantum memories. We consider one implementation of Quantum Cryptographic protocols that use such authentication and demonstrate an attack that fully extract the secret key. Even including the final key from the protocol in the authentication does not rule out the possibility of these attacks. To rectify the situation, we propose a countermeasure that, while not informationtheoretically secure, restores the need for very large computing power for the attack to work. Finally, we specify conditions that must be satisfied by the two-step authentication in order to restore informationtheoretic security.

  • 2.
    Aguilar, Edgar A.
    et al.
    Univ Gdansk, Poland.
    Farkas, Mate
    Univ Gdansk, Poland.
    Martinez, Daniel
    Univ Concepcion, Chile.
    Alvarado, Matias
    Univ Concepcion, Chile.
    Carine, Jaime
    Univ Concepcion, Chile.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering. Univ Concepcion, Chile.
    Barra, Johanna F.
    Univ Concepcion, Chile.
    Canas, Gustavo
    Univ Bio Bio, Chile.
    Pawlowski, Marcin
    Univ Gdansk, Poland.
    Lima, Gustavo
    Univ Concepcion, Chile.
    Certifying an Irreducible 1024-Dimensional Photonic State Using Refined Dimension Witnesses2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 23, article id 230503Article in journal (Refereed)
    Abstract [en]

    We report on a new class of dimension witnesses, based on quantum random access codes, which are a function of the recorded statistics and that have different bounds for all possible decompositions of a high-dimensional physical system. Thus, it certifies the dimension of the system and has the new distinct feature of identifying whether the high-dimensional system is decomposable in terms of lower dimensional subsystems. To demonstrate the practicability of this technique, we used it to experimentally certify the generation of an irreducible 1024-dimensional photonic quantum state. Therefore, certifying that the state is not multipartite or encoded using noncoupled different degrees of freedom of a single photon. Our protocol should find applications in a broad class of modern quantum information experiments addressing the generation of high-dimensional quantum systems, where quantum tomography may become intractable.

    Download full text (pdf)
    fulltext
  • 3.
    Alarcon, Alvaro
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Argillander, Joakim
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Lima, G.
    Univ Concepcion, Chile; Univ Concepcion, Chile.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Few-Mode-Fiber Technology Fine-tunes Losses in Quantum Communication Systems2021In: Physical Review Applied, E-ISSN 2331-7019, Vol. 16, no 3, article id 034018Article in journal (Refereed)
    Abstract [en]

    A natural choice for quantum communication is to use the relative phase between two paths of a single photon for information encoding. This method was nevertheless quickly identified as impractical over long distances, and thus a modification based on single-photon time bins has become widely adopted. It, how-ever, introduces a fundamental loss, which increases with the dimension and limits its application over long distances. Here solve this long-standing hurdle by using a few-mode-fiber space-division-multiplexing platform working with orbital-angular-momentum modes. In our scheme, we maintain the practicability provided by the time-bin scheme, while the quantum states are transmitted through a few-mode fiber in a configuration that does not introduce postselection losses. We experimentally demonstrate our proposal by successfully transmitting phase-encoded single-photon states for quantum cryptography over 500 m of few-mode fiber, showing the feasibility of our scheme.

  • 4.
    Alarcon, Alvaro
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Argillander, Joakim
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Spegel-Lexne, Daniel
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Dynamic generation of photonic spatial quantum states with an all-fiber platform2023In: Optics Express, E-ISSN 1094-4087, Vol. 31, no 6, p. 10673-10683Article in journal (Refereed)
    Abstract [en]

    Photonic spatial quantum states are a subject of great interest for applications in quantum communication. One important challenge has been how to dynamically generate these states using only fiber-optical components. Here we propose and experimentally demonstrate an all-fiber system that can dynamically switch between any general transverse spatial qubit state based on linearly polarized modes. Our platform is based on a fast optical switch based on a Sagnac interferometer combined with a photonic lantern and few-mode optical fibers. We show switching times between spatial modes on the order of 5 ns and demonstrate the applicability of our scheme for quantum technologies by demonstrating a measurement-device-independent (MDI) quantum random number generator based on our platform. We run the generator continuously over 15 hours, acquiring over 13.46 Gbits of random numbers, of which we ensure that at least 60.52% are private, following the MDI protocol. Our results show the use of photonic lanterns to dynamically create spatial modes using only fiber components, which due to their robustness and integration capabilities, have important consequences for photonic classical and quantum information processing.(c) 2023 Optica Publishing Group under the terms of the Optica Open Access Publishing Agreement

    Download full text (pdf)
    fulltext
  • 5.
    Alarcon, Alvaro
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering. Univ Concepcion, Chile.
    Gonzalez, P.
    Univ Concepcion, Chile.
    Carine, J.
    Univ Concepcion, Chile; Univ Catolica Santisima, Chile.
    Lima, G.
    Univ Concepcion, Chile.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Polarization-independent single-photon switch based on a fiber-optical Sagnac interferometer for quantum communication networks2020In: Optics Express, E-ISSN 1094-4087, Vol. 28, no 22, p. 33731-33738Article in journal (Refereed)
    Abstract [en]

    An essential component of future quantum networks is an optical switch capable of dynamically routing single photons. Here we implement such a switch, based on a fiber-optical Sagnac interferometer design. The routing is implemented with a pair of fast electro-optical telecom phase modulators placed inside the Sagnac loop, such that each modulator acts on an orthogonal polarization component of the single photons, in order to yield polarization-independent capability that is crucial for several applications. We obtain an average extinction ratio of more than 19 dB between both outputs of the switch. Our experiment is built exclusively with commercial off-the-shelf components, thus allowing direct compatibility with current optical communication systems. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

    Download full text (pdf)
    fulltext
  • 6.
    Alpat, B.
    et al.
    Ist Nazl Fis Nucl, Italy; Sabanci Univ, Turkey.
    Gulgun, M.A.
    Sabanci Univ, Turkey.
    Corapcioglu, G.
    Sabanci Univ, Turkey.
    Yildizhan Özyar, Melike
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Di Lazzaro, P.
    ENEA, Italy.
    Murra, D.
    ENEA, Italy.
    Kaplanoglu, T.
    Maprad Srl, Italy.
    Postolache, V
    Maprad Srl, Italy.
    Mengali, S.
    Consorzio CREO, Italy.
    Simeoni, M.
    Consorzio CREO, Italy.
    Urbani, A.
    Consorzio CREO, Italy.
    Testing of substrates for flexible optical solar reflectors: irradiations of nano-hybrid coatings of polyimide films with 20 keV electrons and with 200-400 nm ultraviolet radiation2019In: Journal of Instrumentation, ISSN 1748-0221, E-ISSN 1748-0221, Vol. 14, article id T06003Article in journal (Refereed)
    Abstract [en]

    In the frame of a project aimed at developing a new type of optical solar reflectors we present the scientific and technological issues addressed during irradiations of nano-hybrid coatings on polyimide films by using 20 keV electron beam from a modified use of Scanning Electron Microscope (SEM) and with ultraviolet (UV) dose equal to 300 space-equivalent Sun hours. Details of a new approach to use SEM for low energy electron irradiations and of a new UV irradiation setup are given.

  • 7.
    Andersson, Conny
    Linköping University, Department of Electrical Engineering, Vehicular Systems. Linköping University, Faculty of Science & Engineering.
    Design of the Modelica Library VehProLib with Non-ideal Gas Models in Engines2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This thesis covers the reconstruction and the redesign of the modeling library VehProLib,which is constructed in the modeling language Modelica with help of the modeling toolWolfram SystemModeler. The design choices are discussed and implemented. This thesisalso includes the implementation of a turbocharger package and an initial study of the justificationof the ideal gas law in vehicle modeling. The study is made with help of Van derWaals equation of states as a reference of non-ideal gas model. It will be shown that for themean-value-engine-model, the usage of ideal gas law is justified.

    Download full text (pdf)
    Design_of_the_Modelica_Library_VehProLib_with_Non-ideal_Gas_Models_in_Engines
  • 8. Order onlineBuy this publication >>
    Andersson, Mike
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    SiC based field effect sensors and sensor systems for combustion control applications2007Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Increasing oil prices and concerns about global warming have reinforced the interest in biofuels for domestic and district heating, most commonly through combustion of solid biomass like wood logs, hog fuel and pellets. Combustion at non-optimal conditions can, however, lead to substantial emissions of noxious compounds like unburned hydrocarbons, carbon monoxide, and nitrogen oxides as well as the generation of soot.

    Depending on the rate of combustion more or less air is needed per unit time to completely oxidize the fuel; deficiency of air leading to emissions of unburned matter and too much of excess air to slow combustion kinetics and emissions of mainly carbon monoxide. The rate of combustion is influenced by parameters like fuel quality – moisture and ash content etc. – and in what phase the combustion takes place (in the gas phase through combustion of evaporated substances or on the surface of char coal particles), none of which is constant over time.

    The key to boiler operation, both from an environmental as well as a power to fuel economy point of view, is thus the careful adjustment of the air supply throughout the combustion process. So far, no control schemes have been applied to small-scale combustors, though, mainly due to the lack of cheap and simple means to measure basic flue gas parameters like oxygen, total hydrocarbon, and carbon monoxide concentrations.

    This thesis reports about investigations on and characterization of silicon carbide (SiC) based Metal Insulator Semiconductor (MIS) field effect gas sensors regarding their utility in emissions monitoring and combustion control applications as well as the final development of a sensor based control system for wood fired domestic heating systems.

    From the main sensitivity profiles of such sensor devices, with platinum (Pt) and iridium (Ir) as the catalytic metal contacts (providing the gas sensing ability), towards some typical flue gas constituents as well as ammonia (NH3), a system comprising four individual sensors operated at different temperatures was developed, which through the application of Partial Least Squares (PLS) regression, showed good performance regarding simultaneous monitoring of propene (a model hydrocarbon) and ammonia concentrations in synthetic flue gases of varying content. The sensitivity to CO was, however, negligible. The sensor system also performed well regarding ammonia slip monitoring when tested in real flue gases in a 5.6 MW boiler running SNCR (Selective Non-Catalytic reduction of nitrogen oxides with ammonia).

    When applied to a 200 kW wood pellet fuelled boiler a similar sensor system was, however, not able to follow the flue gas hydrocarbon concentration in all encountered situations. A PCA (Principal Components Analysis) based scheme for the manipulation of sensor and flue gas temperature data, enabling monitoring of the state of combustion (deficiency or too much of excess air), was however possible to develop. The discrepancy between laboratory and field test results was suspected and later on shown to depend on the larger variation in CO and oxygen concentrations in the flue gases as compared to the laboratory tests.

    Detailed studies of the CO response characteristics for Pt gate MISiC sensors revealed a highly non-linear sensitivity towards CO, a large response only encountered at high CO/O2 ratios or low temperatures. The response exhibits a sharp switch between a small and a large value when crossing a certain CO/O2 ratio at constant operating temperature, correlated to the transition from an oxygen dominated to an almost fully CO covered Pt surface, originating from the difference in adsorption kinetics between CO and O2. Indications were also given pointing towards an increased sensitivity to background hydrogen as being the mediator of at least part of the CO response. Some general characteristics regarding the response mechanism of field effect sensors with differently structured metal contacts were also indicated.

    The CO response mechanism of Pt metal MISiC sensors could also be utilized in developing a combustion control system based on two sensors and a thermocouple, which when tested in a 40 kW wood fired boiler exhibited a good performance for fuels with extremely low to normal moisture content, substantially decreasing emissions of unburned matter.

    List of papers
    1. Investigations on the possibilities of a MISiCFET sensor system for OBD and combustion control utilizing different catalytic gate materials
    Open this publication in new window or tab >>Investigations on the possibilities of a MISiCFET sensor system for OBD and combustion control utilizing different catalytic gate materials
    Show others...
    2004 (English)In: Topics in catalysis, ISSN 1022-5528, E-ISSN 1572-9028, Vol. 30-31, no 1, p. 365-368Article in journal (Refereed) Published
    Abstract [en]

    Different catalytic materials, like Pt and Ir, applied as gate contacts on metal insulator silicon carbide field effect transistors — MISiCFET—facilitate the manufacture of gas sensor devices with differences in selectivity, devices which due to the chemical stability and wide band gap of SiC are suitable for high temperature applications. The combination of such devices in a sensor system, utilizing multivariate analysis/modeling, have been tested and some promising results in respect of monitoring a few typical exhaust and flue gas constituents, in the future aiming at on board diagnostics (OBD) and combustion control, have been obtained.

    Keywords
    platinum, iridium, sensor system, field effect sensors, SiC, OBD, combustion control, car exhaust, flue gases
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13092 (URN)10.1023/B:TOCA.0000029776.18603.74 (DOI)
    Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2017-12-13Bibliographically approved
    2. On the applicability of MISiCFET gas sensors regarding ammonia slip monitoring in small-scale boilers running SNCR
    Open this publication in new window or tab >>On the applicability of MISiCFET gas sensors regarding ammonia slip monitoring in small-scale boilers running SNCR
    2007 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    Gas sensitive Metal Insulator Silicon Carbide Field Effect Transistor – MISiCFET – devices have shown good possibilities of realizing sensors for high temperature applications. One such application could be the monitoring of ammonia slip from boilers running SNCR – Selective Non-Catalytic Reduction of nitrogen oxides (NOx) with ammonia (NH3). In this study a number of MISiCFET gas sensors operated at different temperatures and with both platinum (Pt) and iridium (Ir) as the gate contact have been tested for their ability to detect and quantify ammonia slip in flue gases from a 5.6 MW wood fired boiler during a test of a new SNCR-system. The individual sensors have been evaluated and compared to each other for the sensitivity towards NH3 and possible cross-sensitivities to other flue gas species through the comparison of the sensor signals with the signals from analytical instruments like FTIR – Fourier Transform Infrared spectroscopy – for nitrogen oxides (NO + NO2), NH3, and carbon monoxide (CO) and an FID – Flame Ionization Detector – for the Total Hydrocarbon Concentration (THC). The ability of a combination of sensors to provide extra or more accurate information about the NH3 concentration was also evaluated through the construction and validation of a Partial Least Squares – PLS – regression model based on all the sensor signals. Under the assumption that the sensors’ responses follow a logarithmic dependence on NH3 concentration the results regarding  ammonia slip quantification were promising both for a single Ir sensor and for the system based on all sensors. There is still a question mark for the long-term stability of the devices in real flue gases, however.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13093 (URN)
    Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2016-09-01Bibliographically approved
    3. SiC-FE gas sensor based combustion control in domestic heating systems, characteristics and utility
    Open this publication in new window or tab >>SiC-FE gas sensor based combustion control in domestic heating systems, characteristics and utility
    Show others...
    2007 (English)Manuscript (preprint) (Other academic)
    Abstract [en]

    SiC based field effect gas sensors have been evaluated for future possible use in combustion control schemes for domestic heating systems. Emphasis has been on the possibility to monitor the state of combustion and follow the development of the combustion process from an emissions point of view and to determine its cause. The sensor signals have been compared to true emissions data – CO and total hydrocarbon concentration – as obtained by an IR spectrometer and a flame ionization detector (FID) as well as flue gas concentration of oxygen as obtained by a paramagnetic cell. The sensor characteristics have been evaluated using multivariate statistics and the results suggest that, by using the signals from one or more SiC-based field effect sensors and a thermocouple, it seems possible to provide a rough picture of the state of combustion applicable to a control scheme in order to reduce emissions and increase the power to fuel economy.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13094 (URN)
    Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2016-09-01Bibliographically approved
    4. On the CO response mechanism of SiC based field effect gas sensors
    Open this publication in new window or tab >>On the CO response mechanism of SiC based field effect gas sensors
    (English)Manuscript (Other academic)
    Abstract [en]

    The response characteristics of Metal Insulator Silicon Carbide (MISiC) field effect sensor devices, with platinum (Pt) as the metal contact, towards carbon monoxide (CO) at varying oxygen (O2) concentrations and over a wide range of temperatures have been investigated in detail at atmospheric pressure. The influence of hydrogen (H2) on the CO response was also studied. Sensor devices with thin, porous as well as dense, homogeneous Pt films on top of both silicon dioxide (SiO2) and magnesium oxide (MgO) as insulator materials were investigated in this study. The reaction products generated on the sensor surfaces were also monitored with a mass spectrometer connected to the gas flow just downstream of the sensor location and the results compared to CO oxidation characteristics over Pt/SiO2 and to some extent Pt/MgO catalysts as reported in literature. By correlating the response characteristics of these devices with CO2 formation and hydrogen consumption on the sensor surfaces, strong indications for a CO response mechanism involving a CO induced increased sensitivity to background hydrogen have been obtained, this mechanism being hypothesized to be the only one behind the CO sensitivity of devices with dense Pt metal contacts. The results also give further support to the idea that also other processes than an increased sensitivity to background hydrogen contribute to the CO response of sensor devices with a porous platinum film as the metal contact, one candidate being the removal of oxygen anions from the surface of exposed oxide areas through the oxidation reaction with CO.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-13095 (URN)
    Note

    This manuscript was never submitted to a journal and will not be published.

    Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2016-06-14Bibliographically approved
    5. On the response mechanism of SiC based field effect gas sensors towards non-hydrogen containing species and specifically NO
    Open this publication in new window or tab >>On the response mechanism of SiC based field effect gas sensors towards non-hydrogen containing species and specifically NO
    (English)Manuscript (Other academic)
    Abstract [en]

    The response characteristics of Metal Insulator Silicon Carbide (MISiC) field effect sensor devices, with platinum (Pt) as the metal contact, towards nitrogen oxide (NO) for both low as well as relatively high background oxygen (O2) concentrations and different temperatures have been investigated at atmospheric pressure. Devices with both porous and dense Pt metal gate contacts have been investigated and the results seem to confirm the theories and results from earlier measurements regarding the requirement of porous metal films for the existence of a response to NO for this kind of sensor device. The results also suggest that no NO induced increased sensitivity to background hydrogen exists, at least it does not play any role in the observed NO sensitivity, as opposed to what has been suggested in the case of CO. The obtained results are also discussed in relation to some of the proposed sensing mechanisms for non-hydrogen containing substances and in comparison to NO reduction characteristics on Pt/SiO2 catalysts, as reported in literature. The results further give some indications about also some other process/ processes being important for the response of SiC based field effect sensors towards NO than just adsorption/desorption.

    National Category
    Physical Sciences
    Identifiers
    urn:nbn:se:liu:diva-13096 (URN)
    Note

    This manuscript was never submitted to a journal and will not be published.

    Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2016-06-14Bibliographically approved
    6. A novel sensor system based on gas sensitive MISiCFET devices for combustion control in small-scale wood fired boilers
    Open this publication in new window or tab >>A novel sensor system based on gas sensitive MISiCFET devices for combustion control in small-scale wood fired boilers
    Show others...
    2007 (English)Article in journal (Refereed) Submitted
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-13097 (URN)
    Available from: 2008-04-01 Created: 2008-04-01 Last updated: 2014-01-09
    Download full text (pdf)
    FULLTEXT01
    Download (pdf)
    COVER01
  • 9.
    Andersson, Olof
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Kemerink, Martijn
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering. Heidelberg Univ, Germany.
    Enhancing Open-Circuit Voltage in Gradient Organic Solar Cells by Rectifying Thermalization Losses2020In: Solar RRL, E-ISSN 2367-198X, Vol. 4, no 12, article id 2000400Article in journal (Refereed)
    Abstract [en]

    In virtually all solar cells, including optimized ones that operate close to the Shockley-Queisser (SQ) limit, thermalization losses are a major, efficiency-limiting factor. In typical bulk heterojunction organic solar cells, the loss of the excess energy of photocreated charge carriers in the disorder-broadened density of states is a relatively slow process that for commonly encountered disorder values takes longer than the charge extraction time. Herein, it is demonstrated by numerical modeling that this slow relaxation can be rectified by means of a linear gradient in the donor:acceptor ratio between anode and cathode. For experimentally relevant parameters, open-circuit voltage (VOC) enhancements up to approximate to 0.2 V in combination with significant enhancements in fill factor as compared to devices without gradient are found. The VOC enhancement can be understood in terms of a simple nonequilibrium effective temperature model. Implications for existing and future organic photovoltaics (OPV) devices are discussed.

    Download full text (pdf)
    fulltext
  • 10.
    Antunes, V. G.
    et al.
    Univ Paris Saclay, France; Univ Grenoble Alpes, France.
    Rudolph, M.
    Leibniz Inst Surface Engn IOM, Germany.
    Kapran, A.
    Acad Sci Czech Republ, Czech Republic.
    Hajihoseini, H.
    Univ Twente, Netherlands.
    Raadu, M. A.
    KTH Royal Inst Technol, Sweden.
    Brenning, Nils
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. KTH Royal Inst Technol, Sweden.
    Gudmundsson, J. T.
    KTH Royal Inst Technol, Sweden; Univ Iceland, Iceland.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    Minea, T.
    Univ Paris Saclay, France.
    Influence of the magnetic field on the extension of the ionization region in high power impulse magnetron sputtering discharges2023In: Plasma sources science & technology, ISSN 0963-0252, E-ISSN 1361-6595, Vol. 32, no 7, article id 075016Article in journal (Refereed)
    Abstract [en]

    The high power impulse magnetron sputtering (HiPIMS) discharge brings about increased ionization of the sputtered atoms due to an increased electron density and efficient electron energization during the active period of the pulse. The ionization is effective mainly within the electron trapping zone, an ionization region (IR), defined by the magnet configuration. Here, the average extension and the volume of the IR are determined based on measuring the optical emission from an excited level of the argon working gas atoms. For particular HiPIMS conditions, argon species ionization and excitation processes are assumed to be proportional. Hence, the light emission from certain excited atoms is assumed to reflect the IR extension. The light emission was recorded above a 100 mm diameter titanium target through a 763 nm bandpass filter using a gated camera. The recorded images directly indicate the effect of the magnet configuration on the average IR size. It is observed that the shape of the IR matches the shape of the magnetic field lines rather well. The IR is found to expand from 10 and 17 mm from the target surface when the parallel magnetic field strength 11 mm above the racetrack is lowered from 24 to 12 mT at a constant peak discharge current.

    The full text will be freely available from 2024-07-28 00:00
  • 11.
    Arabi, C. Mas
    et al.
    Univ Libre Bruxelles, Belgium.
    Parra-Rivas, P.
    Univ Libre Bruxelles, Belgium; Univ Leuven, Belgium.
    Hansson, Tobias
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Gelens, L.
    Univ Leuven, Belgium.
    Wabnitz, S.
    Sapienza Univ Rome, Italy; CNR INO, Italy; Novosibirsk State Univ, Russia.
    Leo, F.
    Univ Libre Bruxelles, Belgium.
    Localized structures formed through domain wall locking in cavity-enhanced second-harmonic generation2020In: Optics Letters, ISSN 0146-9592, E-ISSN 1539-4794, Vol. 45, no 20, p. 5856-5859Article in journal (Refereed)
    Abstract [en]

    We analyze the formation of localized structures in cavity-enhanced second-harmonic generation. We focus on the phase-matched limit, and consider that fundamental and generated waves have opposite signs of group velocity dispersion. We show that these states form due to the locking of domain walls connecting two stable homogeneous states of the system, and undergo collapsed snaking. We study the impact of temporal walk-off on the stability and dynamics of these localized states. (C) 2020 Optical Society of America

  • 12. Order onlineBuy this publication >>
    Armakavicius, Nerijus
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Study of novel electronic materials by mid-infrared and terahertz optical Hall effect2017Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Development of silicon based electronics have revolutionized our every day life during the last three decades. Nowadays Si based devices operate close to their theoretical limits that is becoming a bottleneck for further progress. In particular, for the growing field of high frequency and high power electronics, Si cannot offer the required properties. Development of materials capable of providing high current densities, carrier mobilities and high breakdown fields is crucial for a progress in state of the art electronics.

    Epitaxial graphene grown on semi-insulating silicon carbide substrates has a high potential to be integrated in the current planar device technologies. High electron mobilities and sheet carrier densities make graphene extremely attractive for high frequency analog applications. One of the remaining challenges is the interaction of epitaxial graphene with the substrate. Typically, much lower free charge carrier mobilities, compared to free standing graphene, and doping, due to charge transfer from the substrate, is reported. Thus, a good understanding of the intrinsic free charge carriers properties and the factors affecting them is very important for further development of epitaxial graphene.

    III-group nitrides have been extensively studied and already have proven their high efficiency as light sources for short wavelengths. High carrier mobilities and breakdown electric fields were demonstrated for III-group nitrides, making them attractive for high frequency and high power applications. Currently, In-rich InGaN alloys and AlGaN/GaN high electron mobility structures are of high interest for the research community due to open fundamental questions.

    Electrical characterization techniques, commonly used for the determination of free charge carrier properties, require good ohmic and Schottky contacts, which in certain cases can be difficult to achieve. Access to electrical properties of buried conductive channels in multilayered structures requires modification of samples and good knowledge of the electrical properties of all electrical contact within the structure. Moreover, the use of electrical contacts to electrically characterize two-dimensional electronic materials, such as graphene, can alter their intrinsic properties. Furthermore, the determination of effective mass parameters commonly employs cyclotron resonance and Shubnikov-de Haas oscillations measurements, which require long scattering times of free charge carriers, high magnetic fields and low temperatures.

    The optical Hall effect is an external magnetic field induced optical anisotropy in  conductive layers due to the motion of the free charge carriers under the influence of the Lorentz force, and is equivalent to the electrical Hall effect at optical frequencies. The optical Hall effect can be measured by generalized ellipsometry and provides a powerful method for the determination of free charge carrier properties in a non-destructive and contactless manner. In principle, a single optical Hall effect measurement can provide quantitative information about free charge carrier types, concentrations, mobilities and effective mass parameters at temperatures ranging from few kelvins to room temperature and above. Further, it was demonstrated that for transparent samples, a backside cavity can be employed to enhance the optical Hall effect.

    Measurement of the optical Hall effect by generalized ellipsometry is an indirect technique requiring subsequent data analysis. Parameterized optical models are fitted to match experimentally measured ellipsometric data by varying physically significant parameters. Analysis of the optical response of samples, containing free charge carriers, employing optical models based on the classical Drude model, which is augmented with an external magnetic field contribution, provide access to the free charge carrier properties.

    The main research results of the graduate studies presented in this licentiate thesis are summarized in the five scientific papers.

    Paper I. Description of the custom-built terahertz frequency-domain spectroscopic ellipsometer at Linköping University. The terahertz ellipsometer capabilities are demonstrated by an accurate determination of the isotropic and anisotropic refractive indices of silicon and m-plane sapphire, respectively. Further, terahertz optical Hall effect measurements of an AlGaN/GaN high electron mobility structures were employed to extract the two-dimensional electron gas sheet density, mobility and effective mass parameters. Last, in-situ optical Hall effect measurement on epitaxial graphene in a gas cell with controllable environment, were used to study the effects of environmental doping on the mobility and carrier concentration.

    Paper II. Presents terahertz cavity-enhanced optical Hall measurements of the monolayer and multilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed p-type doping for monolayer graphene with a carrier density in the low 1012 cm−2 range and a carrier mobility of 1550 cm2/V·s. For the multilayer epitaxial graphene, n-type doping with a carrier density in the low 1013 cm−2 range, a mobility of 470 cm2/V·s and an effective mass of (0.14 ± 0.03) m0 were extracted. The measurements demonstrate that cavity-enhanced optical Hall effect measurements can be applied to study electronic properties of two-dimensional materials.

    Paper III. Terahertz cavity-enhanced optical Hall effect measurements are employed to study anisotropic transport in as-grown monolayer, quasi free-standing monolayer and quasi free-standing bilayer epitaxial graphene on semi-insulating 4H-SiC (0001) substrates. The data analysis revealed a strong anisotropy in the carrier mobilities of the quasi freestanding bilayer graphene. The anisotropy is demonstrated to be induced by carriers scattering at the step edges of the SiC, by showing that the mobility is higher along the step than across them. The scattering mechanism is discussed based on the results of the optical Hall effect, low-energy electron microscopy, low-energy electron diffraction and Raman measurements.

    Paper IV. Mid-infrared spectroscopic ellipsometry and mid-infrared optical Hall effect measurements are employed to determine the electron effective mass in an In0.33Ga0.67N epitaxial layer. The data analysis reveals slightly anisotropic effective mass and carrier mobility parameters together with the optical phonon frequencies and broadenings.

    Paper V. Terahertz cavity-enhanced optical Hall measurements are employed to study the free charge carrier properties in a set of AlGaN/GaN high electron mobility structures with modified interfaces. The results show that the interface structure has a significant effect on the free charge carrier mobility and that the sample with a sharp interface between an AlGaN barrier and a GaN buffer layers exhibits a record mobility of 2332±73 cm2/V·s. The determined effective mass parameters showed an increase compared to the GaN value, that is attributed the the penetration of the electron wavefunction into the AlGaN barrier layer.

    List of papers
    1. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Open this publication in new window or tab >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Show others...
    2017 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed) Published
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
    National Category
    Physical Sciences Condensed Matter Physics Atom and Molecular Physics and Optics Ceramics
    Identifiers
    urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)000408756700015 ()
    Note

    Funding agencies: Swedish Research Council (VR) [2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486, 2014-04712]; Swedish foundation for strategic research (SSF) [FFL12-0181, RIF14-055]

    Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2023-12-28Bibliographically approved
    2. Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
    Open this publication in new window or tab >>Properties of two-dimensional electron gas in AlGaN/GaN HEMT structures determined by cavity-enhanced THz optical Hall effect
    Show others...
    2016 (English)In: Physica Status Solidi C-Current Topics in Solid State Physics, Vol 13 No 5-6, Wiley-VCH Verlagsgesellschaft, 2016, Vol. 13, no 5-6, p. 369-373Conference paper, Published paper (Refereed)
    Abstract [en]

    In this work we employ terahertz (THz) ellipsometry to determine two-dimensional electron gas (2DEG) density, mobility and effective mass in AlGaN/GaN high electron mobility transistor structures grown on 4H-SiC substrates. The effect of the GaN interface exposure to low-flow-rate trimethylaluminum (TMA) on the 2DEG properties is studied. The 2DEG effective mass and sheet density are determined tobe in the range of 0.30-0.32m0 and 4.3-5.5×1012 cm–2, respectively. The 2DEG effective mass parameters are found to be higher than the bulk effective mass of GaN, which is discussed in view of 2DEG confinement. It is shown that exposure to TMA flow improves the 2DEG mobility from 2000 cm2/Vs to values above 2200 cm2/Vs. A record mobility of 2332±61 cm2/Vs is determined for the sample with GaN interface exposed to TMA for 30 s. This improvement in mobility is suggested to be due to AlGaN/GaN interface sharpening causing the reduction of interface roughness scattering of electrons in the 2DEG.

    Place, publisher, year, edition, pages
    Wiley-VCH Verlagsgesellschaft, 2016
    Series
    Physica Status Solidi C-Current Topics in Solid State Physics, ISSN 1862-6351
    Keywords
    AlGaN/GaN HEMTs, THz ellipsometry, 2DEG properties, THz optical Hall effect
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-133135 (URN)10.1002/pssc.201510214 (DOI)000387957200045 ()
    Conference
    11th International Conference on Nitride Semiconductors (ICNS), Beijing, China, August 30-September 4. 2015
    Available from: 2016-12-12 Created: 2016-12-09 Last updated: 2023-12-28Bibliographically approved
    Download full text (pdf)
    Study of novel electronic materials by mid-infrared and terahertz optical Hall effect
    Download (pdf)
    omslag
    Download (jpg)
    presentationsbild
  • 13.
    Arnlind, Joakim
    Linköping University, Department of Mathematics, Algebra, Geometry and Discrete Mathematics. Linköping University, Faculty of Science & Engineering.
    Noncommutative Riemannian geometry of Kronecker algebras2024In: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 199, article id 105145Article in journal (Refereed)
    Abstract [en]

    We study aspects of noncommutative Riemannian geometry of the path algebra arising from the Kronecker quiver with N arrows. To start with, the framework of derivation based differential calculi is recalled together with a discussion on metrics and bimodule connections compatible with the *-structure of the algebra. As an illustration, these concepts are applied to the noncommutative torus where examples of torsion free and metric (Levi-Civita) connections are given. In the main part of the paper, noncommutative geometric aspects of (generalized) Kronecker algebras are considered. The structure of derivations and differential calculi is explored, and torsion free bimodule connections are studied together with their compatibility with hermitian forms, playing the role of metrics on the module of differential forms. Moreover, for several different choices of Lie algebras of derivations, non -trivial Levi-Civita connections are constructed. (c) 2024 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons .org /licenses /by /4 .0/).

  • 14.
    Arnlind, Joakim
    et al.
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Al-Shujary, Ahmed
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Kahler-Poisson algebras2019In: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 136, p. 156-172Article in journal (Refereed)
    Abstract [en]

    We introduce Kahler-Poisson algebras as analogues of algebras of smooth functions on Kahler manifolds, and prove that they share several properties with their classical counterparts on an algebraic level. For instance, the module of inner derivations of a Kahler-Poisson algebra is a finitely generated projective module, and allows for a unique metric and torsion-free connection whose curvature enjoys all the classical symmetries. Moreover, starting from a large class of Poisson algebras, we show that every algebra has an associated Kahler-Poisson algebra constructed as a localization. At the end, detailed examples are provided in order to illustrate the novel concepts. (C) 2018 Elsevier B.V. All rights reserved.

  • 15.
    Arnlind, Joakim
    et al.
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Tiger Norkvist, Axel
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Noncommutative minimal embeddings and morphisms of pseudo-Riemannian calculi2021In: Journal of Geometry and Physics, ISSN 0393-0440, E-ISSN 1879-1662, Vol. 159, article id 103898Article in journal (Refereed)
    Abstract [en]

    In analogy with classical submanifold theory, we introduce morphisms of real metric calculi together with noncommutative embeddings. We show that basic concepts, such as the second fundamental form and the Weingarten map, translate into the noncommutative setting and, in particular, we prove a noncommutative analogue of Gauss equations for the curvature of a submanifold. Moreover, the mean curvature of an embedding is readily introduced, giving a natural definition of a noncommutative minimal embedding, and we illustrate the novel concepts by considering the noncommutative torus as a minimal surface in the noncommutative 3-sphere. (c) 2020 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).

    Download full text (pdf)
    fulltext
  • 16.
    Arnlind, Joakim
    et al.
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, Faculty of Science & Engineering.
    Wilson, Mitsuru
    University of Western Ontario, Canada.
    On the Chern-Gauss-Bonnet theorem for the noncommutative 4-sphere2017In: JOURNAL OF GEOMETRY AND PHYSICS, ISSN 0393-0440, Vol. 111, p. 126-141Article in journal (Refereed)
    Abstract [en]

    We construct a differential calculus over the noncommutative 4-sphere in the framework of pseudo-Riemannian calculi, and show that for every metric in a conformal class of perturbations of the round metric, there exists a unique metric and torsion-free connection. Furthermore, we find a localization of the projective module corresponding to the space of vector fields, which allows us to formulate a Chern-Gauss-Bonnet type theorem for the noncommutative 4-sphere. (C) 2016 Elsevier B.V. All rights reserved.

  • 17.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Fernandez Del Rio, Lia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Åkerlind, Christina
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering. Swedish Def Research Agency FOI, Div Command and Control Syst, SE-58111 Linkoping, Sweden.
    Valyukh, Sergiy
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Mendoza-Galvan, A.
    CINVESTAV IPN, Mexico.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Landin, Jan
    Linköping University, Department of Physics, Chemistry and Biology, Ecology. Linköping University, Faculty of Science & Engineering.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    On the polarization of light reflected from beetle cuticle2017In: MATERIALS TODAY-PROCEEDINGS, ELSEVIER SCIENCE BV , 2017, Vol. 4, no 4, p. 4933-4941Conference paper (Refereed)
    Abstract [en]

    The use of Mueller matrices for studies of polarizing properties and cuticle structure of scarab beetles are partly reviewed. Specifically we show how the polarization of the reflected light can be quantified in terms of degree of polarization and ellipticity. It is also shown that sum decomposition of Mueller matrices reveals cuticle reflection characteristics in different spectral regions, e.g. in terms of mirrors and circular polarizers. With a differential decomposition of cuticle transmission Mueller matrices, we determine the spectral variation in the fundamental optical properties circular birefringence and dichroism. (C) 2017 Elsevier Ltd. All rights reserved.

  • 18.
    Arwin, Hans
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering.
    Magnusson, Roger
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering.
    Garcia-Caurel, Enric
    CNRS 91128 Palaiseau, France.
    de Martino, Antonello
    CNRS 91128 Palaiseau, FranceCNRS 91128 Palaiseau, France.
    Järrendahl, Kenneth
    Linköping University, Department of Physics, Chemistry and Biology, Applied Optics. Linköping University, Faculty of Science & Engineering.
    Ossikovski, Razvigor
    CNRS 91128 Palaiseau, France.
    Sum decomposition of Mueller matrices from beetle cuticles2015Conference paper (Other academic)
    Abstract [en]

    Spectral Mueller matrices are very rich in information about physical properties of a sample. We have recently shown that polarizing properties like ellipticity and degree of polarization can be extracted from a Mueller matrix measured on a beetle cuticle (exoskeleton). Mueller matrices can also be used in regression analysis to model nanostructures in cuticles. Here we present the use of sum decomposition of Mueller matrices from these depolarizing biological reflectors to explore the fundamental character of these reflectors. The objective is to decompose a Mueller matrix into well- defined ideal non-depolarizing matrices corresponding to mirrors, circular polarizers, halfwave retarders etc.Generally it is possible to decompose a measured depolarizing Mueller matrix M into four (or fewer) non-depolarizing matrices according to M=λ1M1+λ2M2+λ3M3+λ4M4, where λ1, λ2, λ3 and λ4 are eigenvalues of the covariance matrix of M. Two strategies for decomposition will be discussed. A Cloude decomposition will provide the eigenvalues and also the Mi’s although the latter will contain severe noise in some spectral regions. However, a major advantage with the Cloude decomposition is that the number of nonzero eigenvalues is directly obtained, i.e. the number of contributing Mi matrices. In an alternative decomposition, the Mi’s are assumed and the eigenvalues are found by regression analysis based on M. In the case with two non-zero eigenvalues we define a model Mueller matrix MD=αRM1+βRM2 with αR+βR=1. With αR as adjustable parameter, the Frobenius norm ||M-MD|| is minimized for each wavelength in the spectral range of M. For more complex structures, the regression can be extended by adding more matrices up to a total of four. Advantages with a regression approach are its simplicity and stability compared to a Cloude decomposition.Mueller-matrix spectra of beetle cuticles are recorded with a dual rotating compensator ellipsometer in the spectral range 400 – 900 nm at angles of incidence in the range 20 - 75°. The application of decomposition on biological reflectors is demonstrated on M measured on the beetle Cetonia aurata, which represents a narrow-band chiral Bragg reflector with two non-zero eigenvalues. A decomposition in an ideal mirror and a circular polarizer is feasible. In another example, the broad-band and gold-colored beetle Chrysina argenteola, we show that more than two eigenvalues can be nonzero, especially at oblique incidence, and additional matrices are involved.

    Download full text (pdf)
    fulltext
  • 19.
    Aschebrock, Thilo
    et al.
    University of Bayreuth, Germany.
    Armiento, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Kuemmel, Stephan
    University of Bayreuth, Germany.
    Challenges for semilocal density functionals with asymptotically nonvanishing potentials2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 7, article id 075140Article in journal (Refereed)
    Abstract [en]

    The Becke-Johnson model potential [A. D. Becke and E. R. Johnson, J. Chem. Phys. 124, 221101 ( 2006)] and the potential of the AK13 functional [R. Armiento and S. Kummel, Phys. Rev. Lett. 111, 036402 ( 2013)] have been shown to mimic features of the exact Kohn-Sham exchange potential, such as step structures that are associated with shell closings and particle-number changes. A key element in the construction of these functionals is that the potential has a limiting value far outside a finite system that is a system-dependent constant rather than zero. We discuss a set of anomalous features in these functionals that are closely connected to the nonvanishing asymptotic potential. The findings constitute a formidable challenge for the future development of semilocal functionals based on the concept of a nonvanishing asymptotic constant.

    Download full text (pdf)
    fulltext
  • 20. Order onlineBuy this publication >>
    Asker, Christian
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, The Institute of Technology.
    Effects of disorder in metallic systems from First-Principles calculations2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis, quantum-mechanical calculations within density-functional theory on metallic systems are presented. The overarching goal has been to investigate effects of disorder. In particular, one of the properties investigated is the bindingenergy shifts for core electrons in binary alloys using different theoretical methods. These methods are compared with each other and with experimental results. One such method, the so-called Slater-Janak transition state method relies on the assumption that the single-particle eigenvalues within density-functional theory are linear functions of their respective occupation number. This assumption is investigated and it is found that while the eigenvalues to a first approximation show linear behavior, there are also nonlinearities which can influence the core-level binding energy shifts.

    Another area of investigation has been iron based alloys at pressures corresponding to those in the Earth’s inner core. This has been done for the hexagonal close packed and face entered cubic structures. The effects of alloying iron with magnesium and nickel on the equation of state as well on the elastic properties have been investigated. The calculations have shown that the hexagonal close packed structure in FeNi is more isotropic than the face-centered cubic structure, and that adding Mg to Fe has a large impact on the elastic properties.

    Finally, the effects of disorder due to thermal motion of the atoms have been investigated through ab-initio molecular dynamics simulations. Within the limits of this method and the setup, it is found that the face-centered cubic structure of molybdenum can be dynamically stabilized at high temperature, leading to a metastable structure, on the average. The dynamical stabilization of face-centered cubic molybdenum also rendered it possible to accurately calculate the lattice stability relative to the body-centered cubic phase. Inclusion of temperature effects for the lattice stability using ab-initio molecular dynamics simulations resolves the disagreement between ab-initio calculations and thermochemical methods.

    List of papers
    1. Core-level shifts in fcc random alloys: A first-principles approach
    Open this publication in new window or tab >>Core-level shifts in fcc random alloys: A first-principles approach
    Show others...
    2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 6, p. 064203-Article in journal (Refereed) Published
    Abstract [en]

    First-principles theoretical calculations of the core-level binding-energy shift (CLS) for eight binary face-centered-cubic (fcc) disordered alloys, CuPd, AgPd, CuNi, NiPd, CuAu, PdAu, CuPt, and NiPt, are carried out within density-functional theory (DFT) using the coherent potential approximation. The shifts of the Cu and Ni 2p3∕2, Ag and Pd 3d5∕2, and Pt and Au 4f7∕2 core levels are calculated according to the complete screening picture, which includes both initial-state (core-electron energy eigenvalue) and final-state (core-hole screening) effects in the same scheme. The results are compared with available experimental data, and the agreement is shown to be good. The CLSs are analyzed in terms of initial- and final-state effects. We also compare the complete screening picture with the CLS obtained by the transition-state method, and find very good agreement between these two alternative approaches for the calculations within the DFT. In addition the sensitivity of the CLS to relativistic and magnetic effects is studied.

    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-12565 (URN)10.1103/PhysRevB.72.064203 (DOI)
    Note

    Original publication: W. Olovsson, C. Göransson, L. V. Pourovskii, B. Johansson and I. A. Abrikosov, Core-level shifts in fcc random alloys: A first-principles approach, 2005, Physical Review B, (72), 064203. Copyright: The America Physical Society, http://prb.aps.org/

    Available from: 2008-09-15 Created: 2008-09-15 Last updated: 2024-01-08
    2. Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems
    Open this publication in new window or tab >>Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems
    2005 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 72, no 13Article in journal (Refereed) Published
    Abstract [en]

    According to the so-called Janak’s theorem, the eigenstates of the Kohn-Sham Hamiltonian are given by the derivative of the total energy with respect to the occupation numbers of the corresponding one-electron states. The linear dependence of the Kohn-Sham eigenvalues on the occupation numbers is often assumed in order to use the Janak’s theorem in applications, for instance, in calculations of the core-level shifts in materials by means of the Slater-Janak transition state model. In this work first-principles density-functional theory calculations using noninteger occupation numbers for different core states in 24 different random alloy systems were carried out in order to verify the assumptions of linearity. It is found that, to a first approximation, the Kohn-Sham eigenvalues show a linear behavior as a function of the occupation numbers. However, it is also found that deviations from linearity have observable effects on the core-level shifts for some systems. A way to reduce the error with minimal increase of computational efforts is suggested.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-12559 (URN)10.1103/PhysRevB.72.134203 (DOI)
    Note

    Original publication: C. Göransson, W. Olovsson and I. A. Abrikosov, Numerical investigation of the validity of the Slater-Janak transition-state model in metallic systems, 2005, Physical Review B, (72), 134203. Copyright: The America Physical Society, http://prb.aps.org/

    Available from: 2008-09-15 Created: 2008-09-15 Last updated: 2024-01-08
    3. Core-level shifts in complex metallic systems from first principle
    Open this publication in new window or tab >>Core-level shifts in complex metallic systems from first principle
    2006 (English)In: Physica status solidi. B, Basic research, ISSN 0370-1972, E-ISSN 1521-3951, Vol. 243, no 11, p. 2447-2464Article in journal (Refereed) Published
    Abstract [en]

    We show that core-level binding energy shifts (CLS) can be reliably calculated within density functional theory. The scheme includes both the initial (electron energy eigenvalue) as well as final state (relaxation due to core-hole screening) effects in the same framework. The results include CLS as a function of composition in substitutional random bulk and surface alloys. Sensitivity of the CLS to the local chemical environment in the bulk and at the surface is demonstrated. A possibility to use the CLS for structural determination is discussed. Finally, an extension of the model is made for Auger kinetic energy shift calculations.

    Place, publisher, year, edition, pages
    Wiley, 2006
    Keywords
    71.15.-m, 71.23.-k, 79.20.Fv, 79.60.Dp, 79.60.Ht, 79.60.Jv
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-37239 (URN)10.1002/pssb.200642165 (DOI)34061 (Local ID)34061 (Archive number)34061 (OAI)
    Available from: 2009-10-10 Created: 2009-10-10 Last updated: 2024-01-08
    4. Elastic properties of Fe–Mn random alloys studied by ab initio calculations
    Open this publication in new window or tab >>Elastic properties of Fe–Mn random alloys studied by ab initio calculations
    Show others...
    2007 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 91, no 19, p. 191904-Article in journal (Refereed) Published
    Abstract [en]

    We have studied the influence of the Mn content on the elastic properties of Fe–Mn random alloys (space group of Fmm) using ab initio calculations. The magnetic effects in Fe–Mn alloys have a strong influence on the elastic properties, even above the Néel temperature. As the Mn content is increased from 5  to  40  at.  %, the C44 elastic constant is unaffected, while C11 and C12 decrease. This behavior can be understood based on the magnetovolume effect which softens the lattice. Since the amplitude of local magnetic moments is less sensitive to volume conserving distortions, the softening is not present during shearing.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-12567 (URN)10.1063/1.2807677 (DOI)
    Note
    Original publication: Denis Music, Tetsuya Takahashi, Levente Vitos, Christian Asker, Igor A. Abrikosov and Jochen M. Schneider, Elastic properties of Fe–Mn random alloys studied by ab initio calculations, 2007, Applied Physics Letters, (91), 191904. Copyright: The America Institute of Physics, http://www.aip.org/ Available from: 2008-09-15 Created: 2008-09-15 Last updated: 2024-01-08
    5. First-principles solution to the problem of Mo lattice stability
    Open this publication in new window or tab >>First-principles solution to the problem of Mo lattice stability
    2008 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 77, no 220102(R)Article in journal (Refereed) Published
    Abstract [en]

    The energy differences between the ground state body-centered structure and closed-packed face-centered structure for transition metals in the middle of the series show unusually large disagreements when they are obtained by the thermochemical approach based on the analysis of experimental data or by first-principles electronic structure calculations. Considering a typical example, the lattice stability of Mo, we present a solution to this long-standing problem. We carry out ab initio molecular dynamics simulations for the two phases at high temperature and show that the configurational energy difference approaches the value derived by means of the thermochemical approach. The main contribution to the effect comes from the modification of the canonical band structure due to anharmonic thermal motion at high temperature.

     

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-12560 (URN)10.1103/PhysRevB.77.220102 (DOI)
    Note
    Original publication: C. Asker, A. B. Belonoshko, A. S. Mikhaylushkin and I. A. Abrikosov, First-principles solution to the problem of Mo lattice stability, 2008, Physical Review B, (77), 220102(R). Copyright: The America Physical Society, http://prb.aps.org/Available from: 2008-09-15 Created: 2008-09-15 Last updated: 2024-01-08
    6. Elastic constants and anisotropy in FeNi alloys at high pressures from first-principles calculations
    Open this publication in new window or tab >>Elastic constants and anisotropy in FeNi alloys at high pressures from first-principles calculations
    2009 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 79, no 21, p. 214112-Article in journal (Refereed) Published
    Abstract [en]

    The single-crystal and polycrystalline elastic constants and the elastic anisotropy in face-centered cubic and hexagonal close-packed FeNi alloys have been investigated at ultrahigh pressures by means of first-principles calculations using the exact muffin-tin orbitals method and the coherent-potential approximation. Comparisons with earlier calculations for pure Fe and experimental results are presented and discussed. We show that Ni alloying into Fe increases slightly the density and has very little effect on bulk moduli. Moreover, the relative decrease in c(44) elastic constant is much stronger in the hcp phase than in the fcc one. It is found that the elastic anisotropy is higher for face-centered cubic than for the hexagonal close-packed structure of FeNi, even though the face-centered cubic phase has a higher degree of symmetry. The anisotropy in face-centered cubic structure decreases with increasing nickel concentration while a very weak increase is observed for the hexagonal close-packed structure.

    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-20159 (URN)10.1103/PhysRevB.79.214112 (DOI)
    Available from: 2009-09-01 Created: 2009-08-31 Last updated: 2024-01-08
    7. Equation of state and elastic properties of face-centered cubic FeMg alloy at ultrahigh pressures from first-principles
    Open this publication in new window or tab >>Equation of state and elastic properties of face-centered cubic FeMg alloy at ultrahigh pressures from first-principles
    2010 (English)In: Earth and Planetary Science Letters, ISSN 0012-821X, E-ISSN 1385-013X, Vol. 293, no 1-2, p. 130-134Article in journal (Refereed) Published
    Abstract [en]

    We have ca1culated the equation of state and elastic properties of face-centered cubic Fe and Fe-rich FeMg alloy at ultrahigh pressures from first principles using the Exact Muffin-Tin Orbitals method. The results show that adding Mg into Fe influences strongly the equation of state, and cause a large degree of softening of the elastic constants, even at concentrations as small as 1-2 at. %. Moreover, the e1astic anisotropy increases, and the effect is higher at higher pressures.

    Keywords
    Ab initio, Elasticity, equation of state, iron, magnesium, Earths inner core, Pressure
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-53906 (URN)10.1016/j.epsl.2010.02.032 (DOI)000277217100013 ()
    Note
    Original Publication: Christian Asker, U. Kargén, L. Dubrovinsky and Igor Abrikosov, Equation of state and elastic properties of face-centered cubic FeMg alloy at ultrahigh pressures from first-principles, 2010, Earth and Planetary Science Letters, (293), 1-2, 130-134. http://dx.doi.org/10.1016/j.epsl.2010.02.032 Copyright: Elsevier Science B.V., Amsterdam. http://www.elsevier.com/ Available from: 2010-02-11 Created: 2010-02-11 Last updated: 2024-01-08
    8. Electronic and atomic structure of Mo from high-temperature molecular dynamics simulations
    Open this publication in new window or tab >>Electronic and atomic structure of Mo from high-temperature molecular dynamics simulations
    (English)Manuscript (preprint) (Other (popular science, discussion, etc.))
    Abstract [en]

    By means of ab initio molecular dynamics (AIMD) simulations we carry out a detailed stdly of the electronic and atomic structure of Mo upon the thermal stabilization of its dynamically unstable face-centered cubic (fcc) phase, Wc calculate how the atomic positions, radial distribution function, and the ei<xtronic density of states of fcc Mo evolve with temperature. The results are compared with those for dynamically stable body-centered cubic (bcc) phase of Mo, as well as with bcc Zr, which is dynamically unstable at T = OK, but (in contrast to fcc Mo) becomes thermodynamically stable at high temperature, In particular, wc emphasize the difference between the local positions of atoms in the simulation boxes at a particular step of AIMD simulation and the average positions, around which the atoms vibrate, and show that the former are solcly responsible for the electronic properties of the material. WE observe that while the average atomic positions in fcc Mo correspond perfectly to the ideal structure at high temperature, the electronic structure of the metal calculated from AIMD differs substantially from the canonical shape of the density of states for the ideal fcc crystaL From a comparison of our results obtained for fcc Mo arid bcc Zr, we advocate the use of the electronic structure calculations, complemented with studies of radial distribution functions, as a sensitive test of a degree of the temperature induced stabilization of phases, which are dynamically unstable at T = OK.

    Identifiers
    urn:nbn:se:liu:diva-53779 (URN)
    Available from: 2010-02-03 Created: 2010-02-03 Last updated: 2024-01-08
    Download full text (pdf)
    Effects of disorder in metallic systems from First-Principles calculations
    Download (pdf)
    Cover
    Download (pdf)
    Errata
  • 21.
    Atthapak, Chayanon
    et al.
    Chulalongkorn Univ, Thailand; Minist Higher Educ Sci Res & Innovat, Thailand.
    Ektarawong, Annop
    Chulalongkorn Univ, Thailand; Minist Higher Educ Sci Res & Innovat, Thailand; Chulalongkorn Univ, Thailand.
    Pakornchote, Teerachote
    Chulalongkorn Univ, Thailand; Minist Higher Educ Sci Res & Innovat, Thailand.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Bovornratanaraks, Thiti
    Chulalongkorn Univ, Thailand; Minist Higher Educ Sci Res & Innovat, Thailand.
    Thermodynamic Stability Prediction of Triple Transition-Metal (Ti-Mo-V)3C2 MXenes via Cluster Correlation-Based Machine Learning2024In: Advanced Theory and Simulations, E-ISSN 2513-0390Article in journal (Refereed)
    Abstract [en]

    The representation of atomic configurations through cluster correlations, along with the cluster expansion approach, has long been used to predict formation energies and determine the thermodynamic stability of alloys. In this work, a comparison is conducted between the traditional cluster expansion method based on density functional theory and other potential machine learning models, including decision tree-based ensembles and multi-layer perceptron regression, to explore the alloying behavior of different elements in multi-component alloys. Specifically, these models are applied to investigate the thermodynamic stability of triple transition-metal ((Ti-Mo-V)(3)C-2 MXenes, a multi-component alloy in the largest family of 2D materials that are gaining attention for several outstanding properties. The findings reveal the triple transition-metal ground-state configurations in this system and demonstrate how the configuration of transition metal atoms (Ti, Mo, and V atoms) influences the formation energy of this alloy. Moreover, the performance of machine learning algorithms in predicting formation energies and identifying ground-state structures is thoroughly discussed from various aspects.

  • 22.
    Backman, Björn
    Linköping University, The Department of Physics, Chemistry and Biology.
    Future Upgrades of the LHC Beam Screen Cooling System2006Independent thesis Advanced level (degree of Magister), 20 points / 30 hpStudent thesis
    Abstract [en]

    The topic of this thesis concerns the LHC, the next large particle accelerator at CERN which will start operating in 2007. Being based on superconductivity, the LHC needs to operate at very low temperatures, which makes great demands on the cryogenic system of the accelerator. To cope with the heat loads induced by the particle beam, a beam screen cooled with forced flow of supercritical helium is used.

    There is an interest in upgrading the energy and luminosity of the LHC in the future and this would require a higher heat load to be extracted by the beam screen cooling system. The objective of this thesis is to quantify different ways to upgrade this system by mainly studying the effects of different pressure and temperatures levels as well as a different cooling medium, neon.

    For this a numerical program which simulates one-dimensional pipe flow was constructed. The frictional forces were accounted for by the empirical concept of friction factor. For the fluid properties, software using empirically made correlations was used. To validate the numerical program, a comparison with previous experimental work was done. The agreement with experimental data was good for certain flow configurations, worse for others. From this it was concluded that further comparisons with experimental data must be made in order to tell the accuracy of the mathematical model and the correlations for fluid properties used.

    When using supercritical helium, thermo-hydraulic instabilities may arise in the cooling loop. It was of special interest to see how well a numerical program could simulate and predict this phenomenon. It was found that the numerical program did not function for such unstable conditions; in fact it was much more sensitive than what reality is.

    For the beam screen cooling system we conclude that to cope with the increased heat loads of future upgrades, an increase in pressure level is needed regardless if the coolant remains helium, or is changed to neon. Increasing the pressure level also makes that the problems with thermo-hydraulic instabilities can be avoided. Of the two coolants, helium gave the best heat extraction capacity. Unlike neon, it is also possible to keep the present temperature level when using helium.

    Download full text (pdf)
    FULLTEXT01
  • 23.
    Bai, Yang
    et al.
    Beijing Univ Chem Technol, Peoples R China.
    Zhang, Ze
    Beijing Univ Chem Technol, Peoples R China.
    Zhou, Qiuju
    Xinyang Normal Univ, Peoples R China.
    Geng, Hua
    Capital Normal Univ, Peoples R China.
    Chen, Qi
    Beijing Univ Chem Technol, Peoples R China.
    Kim, Seoyoung
    Ulsan Natl Inst Sci & Technol UNIST, South Korea.
    Zhang, Rui
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Zhang, Cen
    Beijing Univ Chem Technol, Peoples R China.
    Chang, Bowen
    Beijing Univ Chem Technol, Peoples R China.
    Li, Shangyu
    Beijing Univ Chem Technol, Peoples R China.
    Fu, Hongyuan
    Beijing Univ Chem Technol, Peoples R China.
    Xue, Lingwei
    Beijing Univ Chem Technol, Peoples R China.
    Wang, Haiqiao
    Beijing Univ Chem Technol, Peoples R China.
    Li, Wenbin
    Zhengzhou Univ, Peoples R China; Zhengzhou Univ, Peoples R China.
    Chen, Weihua
    Zhengzhou Univ, Peoples R China; Zhengzhou Univ, Peoples R China.
    Gao, Mengyuan
    Tianjin Univ, Peoples R China.
    Ye, Long
    Tianjin Univ, Peoples R China.
    Zhou, Yuanyuan
    Hong Kong Baptist Univ, Peoples R China; Hong Kong Baptist Univ, Peoples R China.
    Ouyang, Yanni
    Hong Kong Baptist Univ, Peoples R China; Hong Kong Baptist Univ, Peoples R China.
    Zhang, Chunfeng
    Nanjing Univ, Peoples R China; Nanjing Univ, Peoples R China.
    Gao, Feng
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Yang, Changduk
    Ulsan Natl Inst Sci & Technol UNIST, South Korea.
    Li, Yongfang
    Chinese Acad Sci, Peoples R China.
    Zhang, Zhi-Guo
    Beijing Univ Chem Technol, Peoples R China.
    Geometry design of tethered small-molecule acceptor enables highly stable and efficient polymer solar cells2023In: Nature Communications, E-ISSN 2041-1723, Vol. 14, no 1, article id 2926Article in journal (Refereed)
    Abstract [en]

    With the power conversion efficiency of binary polymer solar cells dramatically improved, the thermal stability of the small-molecule acceptors raised the main concerns on the device operating stability. Here, to address this issue, thiophene-dicarboxylate spacer tethered small-molecule acceptors are designed, and their molecular geometries are further regulated via the thiophene-core isomerism engineering, affording dimeric TDY-alpha with a 2, 5-substitution and TDY-beta with 3, 4-substitution on the core. It shows that TDY-alpha processes a higher glass transition temperature, better crystallinity relative to its individual small-molecule acceptor segment and isomeric counterpart of TDY-beta, and amore stablemorphology with the polymer donor. As a result, the TDY-alpha based device delivers a higher device efficiency of 18.1%, and most important, achieves an extrapolated lifetime of about 35000 hours that retaining 80% of their initial efficiency. Our result suggests that with proper geometry design, the tethered small-molecule acceptors can achieve both high device efficiency and operating stability.

    Download full text (pdf)
    fulltext
  • 24.
    Beaulieu, Luc
    et al.
    Centre hospitalier universitaire de Québec, Canada and Université Laval, Québec, Canada .
    Carlsson Tedgren, Åsa
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Carrier, Jean-François
    Centre hospitalier de l’Université de Montréal, Québec, Canada and Département de physique, Université de Montréal, Québec Canada .
    Davis, Stephen D.
    University of Wisconsin-Madison, USA and McGill University Health Centre, Montréal, Québec, Canada .
    Mourtada, Firas
    Helen F. Graham Cancer Center, Christiana Care Health System, Newark, Delaware, USA.
    Rivard, Mark J.
    Tufts University School of Medicine, Boston, Massachusetts, USA.
    Thomson, Rowan M.
    Carleton University, Ottawa, Ontario, Canada.
    Verhaegen, Frank
    Maastricht University Medical Center, the Netherlands and McGill University Health Centre, Montréal, Québec, Canada .
    Wareing, Todd A.
    Transpire Inc., Gig Harbor, Washington, USA.
    Williamson, Jeffrey F.
    Virginia Commonwealth University, Richmond, USA.
    Report of the Task Group 186 on model-based dose calculation methods in brachytherapy beyond the TG-43 formalism: Current status and recommendations for clinical implementation2012In: Medical physics (Lancaster), ISSN 0094-2405, Vol. 39, no 10, p. 6208-6236Article in journal (Refereed)
    Abstract [en]

    The charge of Task Group 186 (TG-186) is to provide guidance for early adopters of model-based dose calculation algorithms (MBDCAs) for brachytherapy (BT) dose calculations to ensure practice uniformity. Contrary to external beam radiotherapy, heterogeneity correction algorithms have only recently been made available to the BT community. Yet, BT dose calculation accuracy is highly dependent on scatter conditions and photoelectric effect cross-sections relative to water. In specific situations, differences between the current water-based BT dose calculation formalism (TG-43) and MBDCAs can lead to differences in calculated doses exceeding a factor of 10. MBDCAs raise three major issues that are not addressed by current guidance documents: (1) MBDCA calculated doses are sensitive to the dose specification medium, resulting in energy-dependent differences between dose calculated to water in a homogeneous water geometry (TG-43), dose calculated to the local medium in the heterogeneous medium, and the intermediate scenario of dose calculated to a small volume of water in the heterogeneous medium. (2) MBDCA doses are sensitive to voxel-by-voxel interaction cross sections. Neither conventional single-energy CT nor ICRU∕ICRP tissue composition compilations provide useful guidance for the task of assigning interaction cross sections to each voxel. (3) Since each patient-source-applicator combination is unique, having reference data for each possible combination to benchmark MBDCAs is an impractical strategy. Hence, a new commissioning process is required. TG-186 addresses in detail the above issues through the literature review and provides explicit recommendations based on the current state of knowledge. TG-43-based dose prescription and dose calculation remain in effect, with MBDCA dose reporting performed in parallel when available. In using MBDCAs, it is recommended that the radiation transport should be performed in the heterogeneous medium and, at minimum, the dose to the local medium be reported along with the TG-43 calculated doses. Assignments of voxel-by-voxel cross sections represent a particular challenge. Electron density information is readily extracted from CT imaging, but cannot be used to distinguish between different materials having the same density. Therefore, a recommendation is made to use a number of standardized materials to maintain uniformity across institutions. Sensitivity analysis shows that this recommendation offers increased accuracy over TG-43. MBDCA commissioning will share commonalities with current TG-43-based systems, but in addition there will be algorithm-specific tasks. Two levels of commissioning are recommended: reproducing TG-43 dose parameters and testing the advanced capabilities of MBDCAs. For validation of heterogeneity and scatter conditions, MBDCAs should mimic the 3D dose distributions from reference virtual geometries. Potential changes in BT dose prescriptions and MBDCA limitations are discussed. When data required for full MBDCA implementation are insufficient, interim recommendations are made and potential areas of research are identified. Application of TG-186 guidance should retain practice uniformity in transitioning from the TG-43 to the MBDCA approach.

  • 25.
    Belicev, P. P.
    et al.
    University of Belgrade, Serbia.
    Gligoric, G.
    University of Belgrade, Serbia.
    Maluckov, A.
    University of Belgrade, Serbia.
    Stepic, M.
    University of Belgrade, Serbia.
    Johansson, Magnus
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Localized gap modes in nonlinear dimerized Lieb lattices2017In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 96, no 6, article id 063838Article in journal (Refereed)
    Abstract [en]

    Compact localized modes of ring type exist in many two-dimensional lattices with a flat linear band, such as the Lieb lattice. The uniform Lieb lattice is gapless, but gaps surrounding the flat band can be induced by various types of bond alternations (dimerizations) without destroying the compact linear eigenmodes. Here, we investigate the conditions under which such diffractionless modes can be formed and propagated also in the presence of a cubic on-site (Kerr) nonlinearity. For the simplest type of dimerization with a three-site unit cell, nonlinearity destroys the exact compactness, but strongly localized modes with frequencies inside the gap are still found to propagate stably for certain regimes of system parameters. By contrast, introducing a dimerization with a 12-site unit cell, compact (diffractionless) gap modes are found to exist as exact nonlinear solutions in continuation of flat band linear eigenmodes. These modes appear to be generally weakly unstable, but dynamical simulations show parameter regimes where localization would persist for propagation lengths much larger than the size of typical experimental waveguide array configurations. Our findings represent an attempt to realize conditions for full control of light propagation in photonic environments.

    Download full text (pdf)
    fulltext
  • 26.
    Belonovski, Alexey V
    et al.
    St Petersburg Acad Univ, Russia.
    Levitskii, Iaroslav V
    ITMO Univ, Russia; Ioffe Inst, Russia.
    Morozov, Konstantin M.
    ITMO Univ, Russia.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kaliteevski, Mikhail A.
    St Petersburg Acad Univ, Russia; ITMO Univ, Russia; Ioffe Inst, Russia.
    Weak and strong coupling of photons and excitons in planar meso-cavities2020In: Optics Express, E-ISSN 1094-4087, Vol. 28, no 9, p. 12688-12698Article in journal (Refereed)
    Abstract [en]

    The interaction of an exciton and cavity modes is considered in planar meso-cavities, which have lateral sizes corresponding to few wavelengths. In meso-cavities, the frequency interval between the optical modes is comparable or smaller than the value of the Rabi splitting between the exciton and the optical modes. The Hamiltonian of the interaction between the exciton and the cavity modes is constructed, and it is shown that such an interaction between the cavity modes and the exciton can occur both in weak and in strong coupling regimes. The latter case can be accompanied by a pronounced splitting of the emission peaks as shown for modelled meso-cavities of triangular, square and hexagonal shapes, where it is demonstrated that Q-factors for the adjacent cavity modes as well as the strength of interaction with excitons can differ by few orders of magnitude. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

    Download full text (pdf)
    fulltext
  • 27.
    Belonovski, Alexey V
    et al.
    St Petersburg Acad Univ, Russia; ITMO Univ, Russia.
    Morozov, Konstantin M.
    ITMO Univ, Russia.
    Girshova, Elizaveta I
    St Petersburg Acad Univ, Russia; ITMO Univ, Russia.
    Pozina, Galia
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, Faculty of Science & Engineering.
    Kaliteevski, Mikhail A.
    St Petersburg Acad Univ, Russia; ITMO Univ, Russia.
    Quantum analysis of luminescence of an exciton in a meso-cavity2021In: Optics Express, E-ISSN 1094-4087, Vol. 29, no 13, p. 20724-20734Article in journal (Refereed)
    Abstract [en]

    Interaction of cavity modes with an exciton in a meso-cavity (the structure supporting several cavity modes separated by an energy interval comparable to Rabi-splitting of an exciton and cavity modes) has been analyzed using a quantum-mechanical approach. Simultaneous interaction of an exciton and several cavity modes results in few novel effects such as ladder-like increase of the exciton population in the system, quantum beating and non-monotonic dependence of the ground polariton state in the system on the pumping. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

    Download full text (pdf)
    fulltext
  • 28.
    Berggren, Karl
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, The Institute of Technology.
    A high sensitivity imaging detector for the study of the formation of (anti)hydrogen2013Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    AEGIS (Antimatter Experiment, Gravity, Interferometry and Spectroscopy) isan experiment under development at CERN which will measure earth's gravitationalforce on antimatter. This will be done by creating a horizontal pulsedbeam of low energy antihydrogen, an atom consisting of an antiproton anda positron. The experiment will measure the vertical de ection of the beamthrough which it is possible to calculate the gravitational constant for antimatter.To characterise the production process in the current state of the experimentit is necessary to develop an imaging detector for single excited hydrogenatoms. This thesis covers the design phase of that detector and includes studiesand tests of detector components. Following literature studies, tests and havingdiscarded several potential designs, a baseline design was chosen. The suggesteddetector will contain a set of ionising rings followed by an electron multiplyingmicrochannel plate, a light emitting phosphor screen, a lens system and nallya CCD camera for readout. The detector will be able to detect single hydrogenatoms, measure their time of ight as well as being able to image electronplasmas and measure the time of ight of the initial particles in such a plasma.Tests were made to determine the behaviour of microchannel plates at the lowtemperatures used in the experiment. Especially, the resistance and multiplicationfactor of the microchannel plates have been measured at temperaturesdown to 14 K.

    Download full text (pdf)
    Master's thesis Karl Berggren
  • 29.
    Berggren, Karl-Fredrik
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Tellander, Felix
    Lund Univ, Sweden.
    Yakymenko, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Basic modelling of transport in 2D wave-mechanical nanodots and billiards with balanced gain and loss mediated by complex potentials2018In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, no 20, article id 204003Article in journal (Refereed)
    Abstract [en]

    Non-Hermitian quantum mechanics with parity-time (PT) symmetry is presently gaining great interest, especially within the fields of photonics and optics. Here, we give a brief overview of low-dimensional semiconductor nanodevices using the example of a quantum dot with input and output leads, which are mimicked by imaginary potentials for gain and loss, and how wave functions, particle flow, coalescence of levels and associated breaking of PT symmetry may be analysed within such a framework. Special attention is given to the presence of exceptional points and symmetry breaking. Related features for musical string instruments and wolf-notes are outlined briefly with suggestions for further experiments.

    Download full text (pdf)
    fulltext
  • 30.
    Berghofer, Philipp
    et al.
    Department of Philosophy, University of Graz, Austria.
    Goyal, Philip
    Department of Physics, University at Albany, Albany, USA.
    Wiltsche, Harald
    Linköping University, Faculty of Arts and Sciences. Linköping University, Department of Culture and Society, Division of Philosophy, History, Arts and Religion.
    Husserl, the mathematization of nature, and the informational reconstruction of quantum theory2021In: Continental philosophy review, ISSN 1387-2842, E-ISSN 1573-0611, Vol. 54, no 4, p. 413-436Article in journal (Refereed)
    Abstract [en]

    As is well known, the late Husserl warned against the dangers of reifying and objectifying the mathematical models that operate at the heart of our physical theories. Although Husserl’s worries were mainly directed at Galilean physics, the first aim of our paper is to show that many of his critical arguments are no less relevant today. By addressing the formalism and current interpretations of quantum theory, we illustrate how topics surrounding the mathematization of nature come to the fore naturally. Our second aim is to consider the program of reconstructing quantum theory, a program that currently enjoys popularity in the field of quantum foundations. We will conclude by arguing that, seen from this vantage point, certain insights delivered by phenomenology and quantum theory regarding perspectivity are remarkably concordant. Our overall hope with this paper is to show that there is much room for mutual learning between phenomenology and modern physics.

    Download full text (pdf)
    fulltext
  • 31.
    Bergstedt, Mikael
    Linköping University, The Department of Physics, Chemistry and Biology.
    Theoretical investigation of the first-order hyperpolarizability in the two-photon resonant region2007Independent thesis Advanced level (degree of Magister), 10 points / 15 hpStudent thesis
    Abstract [en]

    Time-dependent density functional theory calculations have been carried out to determine the complex first-order hyperpolarizability in the two-photon resonance region of the molecule IDS-Cab. Calculations show that three strongly absorbing states, in the ultraviolet region, are separated to the extent that no significant interference of the imaginary parts of the tensor elements of the first-order hyper-polarizability occurs. Consequently, and in contrast to experimental findings [27], no reduced imaginary parts of the first-order hyperpolarizability in the two-photon resonant region can be seen.

    Download full text (pdf)
    FULLTEXT01
  • 32.
    Bian, Qingzhen
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ma, Fei
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Chen, Shula
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Wei, Qi
    Institute of Applied Physics and Materials Engineering, University of Macau, Macau SAR, China.
    Su, Xiaojun
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Buyanova, Irina A
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ponseca, Carlito S.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Linares, Mathieu
    Department of Theoretical Chemistry and Biology, KTH Royal Institute of Technology, Stockholm, Sweden.
    Karki, Khadga J.
    Division of Chemical Physics, Lund University, 22100, Lund, Sweden.
    Yartsev, Arkady
    Division of Chemical Physics, Lund University, Lund, Sweden.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Vibronic coherence contributes to photocurrent generation in organic semiconductor heterojunction diodes2020In: Nature Communications, E-ISSN 2041-1723, Vol. 11, no 1, article id 617Article in journal (Refereed)
    Abstract [en]

    Charge separation dynamics after the absorption of a photon is a fundamental process relevant both for photosynthetic reaction centers and artificial solar conversion devices. It has been proposed that quantum coherence plays a role in the formation of charge carriers in organic photovoltaics, but experimental proofs have been lacking. Here we report experimental evidence of coherence in the charge separation process in organic donor/acceptor heterojunctions, in the form of low frequency oscillatory signature in the kinetics of the transient absorption and nonlinear two-dimensional photocurrent spectroscopy. The coherence plays a decisive role in the initial ~200 femtoseconds as we observe distinct experimental signatures of coherent photocurrent generation. This coherent process breaks the energy barrier limitation for charge formation, thus competing with excitation energy transfer. The physics may inspire the design of new photovoltaic materials with high device performance, which explore the quantum effects in the next-generation optoelectronic applications.

    Download full text (pdf)
    fulltext
  • 33.
    Blake, Jolie C.
    et al.
    Chalmers Univ Technol, Sweden.
    Rossi, Stefano
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Jonsson, Magnus
    Linköping University, Department of Science and Technology, Laboratory of Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Dahlin, Andreas
    Chalmers Univ Technol, Sweden.
    Scalable Reflective Plasmonic Structural Colors from Nanoparticles and Cavity Resonances - the Cyan-Magenta-Yellow Approach2022In: Advanced Optical Materials, ISSN 2162-7568, E-ISSN 2195-1071, Vol. 10, no 13, article id 2200471Article in journal (Refereed)
    Abstract [en]

    Plasmonic metasurfaces for color generation are emerging as important components for next generation display devices. Fabricating bright plasmonic colors economically and via easily scalable methods, however, remains difficult. Here, the authors demonstrate an efficient and scalable strategy based on colloidal lithography to fabricate silver-based reflective metal-insulator-nanodisk plasmonic cavities that provide a cyan-magenta-yellow (CMY) color palette with high relative luminance. With the same basic structure, they exploit different mechanisms to efficiently produce a complete subtractive color palette. Finite-difference time-domain simulations reveal that these mechanisms include gap surface plasmon modes for thin insulators and hybridized modes between disk plasmons and Fabry-Perot modes for thicker systems. To produce yellow hues, they take advantage of higher-energy gap surface plasmon modes to allow resonance dips in the blue spectral region for comparably large nanodisks, thereby circumventing difficult fabrication of nanodisks less than 80 nm. It is anticipated that incorporation of these strategies can reduce fabrication constraints, produce bright saturated colors, and expedite large-scale production.

    Download full text (pdf)
    fulltext
  • 34.
    Blaszak, Maciej
    et al.
    Adam Mickiewicz Univ, Poland.
    Szablikowski, Blazej m.
    Adam Mickiewicz Univ, Poland.
    Marciniak, Krzysztof
    Linköping University, Department of Science and Technology, Physics, Electronics and Mathematics. Linköping University, Faculty of Science & Engineering.
    Stäckel representations of stationary Kdv systems2023In: Reports on mathematical physics, ISSN 0034-4877, E-ISSN 1879-0674, Vol. 92, no 3, p. 323-346Article in journal (Refereed)
    Abstract [en]

    In this article we study Stackel representations of stationary KdV systems. Using Lax formalism we prove that these systems have two different representations as separable Stackel systems of Benenti type, related with different foliations of the stationary manifold. We do it by constructing an explicit transformation between the jet coordinates of stationary KdV systems and separation variables of the corresponding Benenti systems for arbitrary number of degrees of freedom. Moreover, on the stationary manifold, we present the explicit form of Miura map between both representations of stationary KdV systems, which also yields their bi-Hamiltonian formulation.

    The full text will be freely available from 2025-12-30 15:58
  • 35.
    Bosser, Lennart
    et al.
    Swedish Def Res Agcy, Sweden.
    Bosser, John Daniel
    Chalmers Univ Technol, Sweden.
    Target echo calculations using the OpenGL graphics pipeline2021In: Applied Acoustics, ISSN 0003-682X, E-ISSN 1872-910X, Vol. 181, article id 108133Article in journal (Refereed)
    Abstract [en]

    This paper presents a novel approach to using modern graphics card capabilities for predicting the hydroacoustic target echo strength of an object. The key feature of this method is to inject code in the fragment shader stage of the OpenGL graphics pipeline, in effect transforming the optics reflection problem of computer graphics to an acoustic reflection problem. This is exemplified with the simple situation of an acoustically hard body and the monostatic detection case. Numerical accuracy is compared with Kirchhoff theory for simple bodies. Some suggestions for further work are proposed. (C) 2021 Elsevier Ltd. All rights reserved.

  • 36. Order onlineBuy this publication >>
    Bouhafs, Chamseddine
    Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
    Structural and Electronic Properties of Graphene on 4H- and 3C-SiC2016Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Graphene is a one-atom-tick carbon layer arranged in a honeycomb lattice. Graphene was first experimentally demonstrated by Andre Geim and Konstantin Novoselov in 2004 using mechanical exfoliation of highly oriented pyrolytic graphite (exfoliated graphene flakes), for which they received the Nobel Prize in Physics in 2010. Exfoliated graphene flakes show outstanding electronic properties, e.g., very high free charge carrier mobility parameters and ballistic transport at room temperature. This makes graphene a suitable material for next generation radio-frequency and terahertz electronic devices. Such applications require fabrication methods of large-area graphene compatible with electronic industry. Graphene grown by sublimation on silicon carbide (SiC) offers a viable route towards production of large-area, electronic-grade material on semi-insulating substrate without the need of transfer. Despite the intense investigations in the field, uniform wafer-scale graphene with very high-quality that matches the properties of exfoliated graphene has not been achieved yet. The key point is to identify and control how the substrate affects graphene uniformity, thickness, layer stacking, structural and electronic properties. Of particular interest is to understand the effects of SiC surface polarity and polytype on graphene properties in order to achieve large-area material with tailored properties for electronic applications. The main objectives of this thesis are to address these issues by investigating the structural and electronic properties of epitaxial graphene grown on 4HSiC and 3C-SiC substrates with different surface polarities. The first part of the thesis includes a general description of the properties of graphene, bilayer graphene and graphite. Then, the properties of epitaxial graphene on SiC by sublimation are detailed. The experimental techniques used to characterize graphene are described. A summary of all papers and contribution to the field is presented at the end of Part I. Part II consists of seven papers.

    List of papers
    1. Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
    Open this publication in new window or tab >>Structural properties and dielectric function of graphene grown by high-temperature sublimation on 4H-SiC(000-1)
    Show others...
    2015 (English)In: Journal of Applied Physics, ISSN 0021-8979, E-ISSN 1089-7550, Vol. 117, no 8, p. 085701-Article in journal (Refereed) Published
    Abstract [en]

    Understanding and controlling growth of graphene on the carbon face (C-face) of SiC presents a significant challenge. In this work, we study the structural, vibrational, and dielectric function properties of graphene grown on the C-face of 4H-SiC by high-temperature sublimation in an argon atmosphere. The effect of growth temperature on the graphene number of layers and crystallite size is investigated and discussed in relation to graphene coverage and thickness homogeneity. An amorphous carbon layer at the interface between SiC and the graphene is identified, and its evolution with growth temperature is established. Atomic force microscopy, micro-Raman scattering spectroscopy, spectroscopic ellipsometry, and high-resolution cross-sectional transmission electron microscopy are combined to determine and correlate thickness, stacking order, dielectric function, and interface properties of graphene. The role of surface defects and growth temperature on the graphene growth mechanism and stacking is discussed, and a conclusion about the critical factors to achieve decoupled graphene layers is drawn. (C) 2015 AIP Publishing LLC.

    Place, publisher, year, edition, pages
    American Institute of Physics (AIP), 2015
    National Category
    Condensed Matter Physics
    Identifiers
    urn:nbn:se:liu:diva-117253 (URN)10.1063/1.4908216 (DOI)000351132500070 ()
    Note

    Funding Agencies|Marie Curie actions [264613-NetFISiC]; Swedish Research Council (VR) [2011-4447, 2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486]; Swedish foundation for strategic research (SSF) [FFL12-0181]; FP7 EU project Nano-Rf [FP7-ICT-2011-8]; French ANR under the Grafonics Project [ANR-10-NANO-0004]; European Union Seventh Framework Programme under Graphene Flagship [604391]; Knut and Alice Wallenbergs foundation

    Available from: 2015-04-22 Created: 2015-04-21 Last updated: 2023-12-28
    2. Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Open this publication in new window or tab >>Cavity-enhanced optical Hall effect in epitaxial graphene detected at terahertz frequencies
    Show others...
    2017 (English)In: Applied Surface Science, ISSN 0169-4332, E-ISSN 1873-5584, Vol. 421, p. 357-360Article in journal (Refereed) Published
    Abstract [en]

    Cavity-enhanced optical Hall effect at terahertz (THz) frequencies is employed to determine the free charge carrier properties in epitaxial graphene (EG) with different number of layers grown by high-temperature sublimation on 4H-SiC(0001). We find that one monolayer (ML) EG possesses p-type conductivity with a free hole concentration in the low 1012 cmᅵᅵᅵ2 range and a free hole mobility parameter as high as 1550 cm2/Vs. We also find that 6 ML EG shows n-type doping behavior with a much lower free electron mobility parameter of 470 cm2/Vs and an order of magnitude higher free electron density in the low 1013 cmᅵᅵᅵ2 range. The observed differences are discussed. The cavity-enhanced THz optical Hall effect is demonstrated to be an excellent tool for contactless access to the type of free charge carriers and their properties in two-dimensional materials such as EG.

    Place, publisher, year, edition, pages
    Elsevier, 2017
    Keywords
    THz optical Hall effect, Epitaxial graphene, Free charge carrier properties
    National Category
    Physical Sciences Condensed Matter Physics Atom and Molecular Physics and Optics Ceramics
    Identifiers
    urn:nbn:se:liu:diva-132407 (URN)10.1016/j.apsusc.2016.10.023 (DOI)000408756700015 ()
    Note

    Funding agencies: Swedish Research Council (VR) [2013-5580]; Swedish Governmental Agency for Innovation Systems (VINNOVA) under the VINNMER international qualification program [2011-03486, 2014-04712]; Swedish foundation for strategic research (SSF) [FFL12-0181, RIF14-055]

    Available from: 2016-11-09 Created: 2016-11-09 Last updated: 2023-12-28Bibliographically approved
    Download full text (pdf)
    Structural and Electronic Properties of Graphene on 4H- and 3C-SiC
    Download (pdf)
    omslag
    Download (jpg)
    presentationsbild
  • 37.
    Brenning, Nils
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering. Univ Paris Saclay, France; KTH Royal Inst Technol, Sweden.
    Hajihoseini, Hamidreza
    Univ Iceland, Iceland.
    Rudolph, Martin
    Leibniz Inst Surface Engn IOM, Germany.
    Raadu, Michael A.
    KTH Royal Inst Technol, Sweden.
    Gudmundsson, Jon Tomas
    KTH Royal Inst Technol, Sweden; Univ Iceland, Iceland.
    Minea, Tiberiu M.
    Univ Paris Saclay, France.
    Lundin, Daniel
    Linköping University, Department of Physics, Chemistry and Biology, Plasma and Coating Physics. Linköping University, Faculty of Science & Engineering.
    HiPIMS optimization by using mixed high-power and low-power pulsing2021In: Plasma sources science & technology, ISSN 0963-0252, E-ISSN 1361-6595, Vol. 30, no 1, article id 015015Article in journal (Refereed)
    Abstract [en]

    The possibility to optimize a high-power impulse magnetron sputtering (HiPIMS) discharge through mixing two different power levels in the pulse pattern is investigated. Standard HiPIMS pulses are used to create the ions of the film-forming material. After each HiPIMS pulse an off-time follows, during which no voltage (or, optionally, a reversed voltage) is applied, letting the remaining ions in the magnetic trap escape towards the substrate. After these off-times, a long second pulse with lower amplitude, in the dc magnetron sputtering range, is applied. During this pulse, which is continued up to the following HiPIMS pulse, mainly neutrals of the film-forming material are produced. This pulse pattern makes it possible to achieve separate optimization of the ion production, and of the neutral atom production, that constitute the film-forming flux to the substrate. The optimization process is thereby separated into two sub-problems. The first sub-problem concerns minimizing the energy cost for ion production, and the second sub-problem deals with how to best split a given allowed discharge power between ion production and neutral production. The optimum power split is decided by the lowest ionized flux fraction that gives the desired film properties for a specific application. For the first sub-problem we describe a method where optimization is achieved by the selection of five process parameters: the HiPIMS pulse amplitude, the HiPIMS pulse length, the off-time, the working gas pressure, and the magnetic field strength. For the second sub-problem, the splitting of power between ion and neutral production, optimization is achieved by the selection of the values of two remaining process parameters, the HiPIMS pulse repetition frequency and the discharge voltage of the low-power pulse.

  • 38.
    Brolin, Gustav
    et al.
    Department of Medical Radiation Physics, Lund University, Sweden.
    Granerus, Göran
    Linköping University, Department of Medical and Health Sciences, Clinical Physiology. Linköping University, Department of Medical and Health Sciences, Cardiology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Center, Department of Clinical Physiology in Linköping.
    Olsson, Anna
    Linköping University, Department of Medical and Health Sciences, Radiation Physics. Linköping University, Faculty of Health Sciences.
    Edenbrandt, Lars
    Department of Clinical Sciences, Malmö, Lund University, Sweden.
    Ljungberg, Michael
    Department of Medical Radiation Physics, Lund University, Sweden.
    A new Method for Monte Carlo Simulations of Dynamic Scintillation Camera Imaging: 99mTc MAG3 Renography Studies2012Conference paper (Other academic)
  • 39.
    Brännvall, Marian
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Gambino, Davide
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Armiento, Rickard
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Alling, Björn
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    Machine learning approach for longitudinal spin fluctuation effects in bcc Fe at Tc and under Earth-core conditions2022In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 105, no 14, article id 144417Article in journal (Refereed)
    Abstract [en]

    We propose a machine learning approach to predict the shapes of the longitudinal spin fluctuation (LSF) energy landscapes for each local magnetic moment. This approach allows the inclusion of the effects of LSFs in, e.g., the simulation of a magnetic material with ab initio molecular dynamics in an effective way. This type of simulation requires knowledge of the reciprocal interaction between atoms and moments, which, in principle, would entail calculating the energy landscape of each atom at every instant in time. The machine learning approach is based on the kernel ridge regression method and developed using bcc Fe at the Curie temperature and ambient pressure as a test case. We apply the trained machine learning models in a combined atomistic spin dynamics and ab initio molecular dynamics (ASD-AIMD) simulation, where they are used to determine the sizes of the magnetic moments of every atom at each time step. In addition to running an ASD-AIMD simulation with the LSF machine learning approach for bcc Fe at the Curie temperature, we also simulate Fe at temperature and pressure comparable to the conditions at the Earth's inner solid core. The latter simulation serves as a critical test of the generality of the method and demonstrates the importance of the magnetic effects in Fe in the Earth's core despite its extreme temperature and pressure.

  • 40.
    Bugaev, K. A.
    et al.
    Bogolyubov Inst Theoret Phys, Ukraine; Taras Shevchenko Natl Univ Kyiv, Ukraine.
    Ivanytskyi, O. I.
    Bogolyubov Inst Theoret Phys, Ukraine; Univ Coimbra, Portugal.
    Grinyuk, B. E.
    Bogolyubov Inst Theoret Phys, Ukraine.
    Yakymenko, Iryna
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Physics. Linköping University, Faculty of Science & Engineering.
    BOSE-EINSTEIN CONDENSATION AS A DEPOSITION PHASE TRANSITION OF QUANTUM HARD SPHERES AND NEW RELATIONS BETWEEN BOSONIC AND FERMIONIC PRESSURES2020In: UKRAINIAN JOURNAL OF PHYSICS, ISSN 2071-0186, Vol. 65, no 11, p. 963-972Article in journal (Refereed)
    Abstract [en]

    We investigate the phase transition of Bose-Einstein particles with the hard-core repulsion in the grand canonical ensemble within the Van der Waals approximation. It is shown that the pressure of non-relativistic Bose-Einstein particles is mathematically equivalent to the pressure of simplified version of the statistical multifragmentation model of nuclei with the vanishing surface tension coefficient and the Fisher exponent tau(F) = 5/2, which for such parameters has the 1-st order phase transition. The found similarity of these equations of state allows us to show that within the present approach the high density phase of Bose-Einstein particles is a classical macro-cluster with vanishing entropy at any temperature which, similarly to the system of classical hard spheres, is a kind of solid state. To show this we establish new relations which allow us to identically represent the pressure of Fermi-Dirac particles in terms of pressures of Bose-Einstein particles of two sorts.

  • 41.
    Bugaev, K. A.
    et al.
    Bogolyubov Inst Theoret Phys, Ukraine.
    Sagun, V. V.
    Bogolyubov Inst Theoret Phys, Ukraine; Univ Lisbon, Portugal.
    Ivanytskyi, A. I.
    Bogolyubov Inst Theoret Phys, Ukraine.
    Yakimenko, Ivan P.
    Linköping University, Department of Physics, Chemistry and Biology. Linköping University, Faculty of Science & Engineering.
    Nikonov, E. G.
    JINR, Russia.
    Taranenko, A. V.
    Natl Res Nucl Univ MEPhI, Russia.
    Zinovjev, G. M.
    Bogolyubov Inst Theoret Phys, Ukraine.
    Going beyond the second virial coefficient in the hadron resonance gas model2018In: Nuclear Physics A, ISSN 0375-9474, E-ISSN 1873-1554, Vol. 970, p. 133-155Article in journal (Refereed)
    Abstract [en]

    We develop a novel formulation of the hadron resonance gas model which, besides a hard-core repulsion, explicitly accounts for the surface tension induced by the interaction between the particles. Such an equation of state allows us to go beyond the Van der Waals approximation for any number of different hard-core radii. A comparison with the Carnahan Starling equation of state shows that the new model is valid for packing fractions 0.2-0.22, while the usual Van der Waals model is inapplicable at packing fractions above 0.1-0.11. Moreover, it is shown that the equation of state with induced surface tension is softer than the one of hard spheres and remains causal at higher particle densities. The great advantage of our model is that there are only two equations to be solved and neither their number nor their form depend on the values of the hard-core radii used for different hadronic resonances. Such an advantage leads to a significant mathematical simplification compared to other versions of truly multi-component hadron resonance gas models. Using this equation of state we obtain a high-quality fit of the ALICE hadron multiplicities measured at the center-of-mass energy 2.76 TeV per nucleon and we find that the dependence of chi(2)/ndf on the temperature has a single global minimum in the traditional hadron resonance gas model with the multi-component hard-core repulsion. Also we find two local minima of chi(2)/ndf in the model in which the proper volume of each hadron is proportional to its mass. However, it is shown that in the latter model a second local minimum located at higher temperatures always appears far above the limit of its applicability. (C) 2017 Elsevier B.V. All rights reserved.

  • 42.
    Bunnfors, Kalle
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Imaging and Spectroscopic Mapping of Blood Cell Activity: Nanoparticles and Neutrophil Extracellular Traps2021Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Imaging and visualization of cell activity when exposed to nanomaterial are of main importance, when investigating biological response to a wide range of biomaterials from medical implants to smart nanoprobes. The ability to provide molecular and chemical information with spatial resolution in the region of sub-µm leads to increased insight and understanding of these biological challenges. Interdisciplinary collaborative effort may contribute and help solving urgent matters related to the challenges that we globally share. It is necessary to develop powerful tools such as analytical imaging techniques for addressing these urgent issues. This will increase our knowledge from the visualization on the cellular and subcellular level and help designing sustainable, personalized medical nanoprobes. In this thesis, the focus is to investigate the possibilities using the fluorescence microscopy, combined with surface analytical techniques delivering element specific information. 

    Neutrophils are the most abundant immune cell in our bodies. They scavenge the body for threats and are usually among the first ones to find intruders and start the inflammation process. They have several ways of handling a threat, the main three being degranulation, phagocytosis, and neutrophil extracellular traps (NETs). In short, degranulation where granules are released into the extracellular matrix, phagocytosis is the process when for example the bacteria in engulfed by the neutrophil and neutralized. The NETs are when the neutrophil decondense their DNA and throw it out as a net to physically trap the invader and together with reactive oxygen species, proteases, and other antimicrobial molecules. It has been observed that nanoparticles (NP) can trigger NETs and there have been some comparisons between different parameters such as size, geometry, and functionalization. 

    In this thesis we have explored how to measure neutrophil activity by a novel label free and noninvasive method (Paper 1). The NanoEsca, a combined XPS and PEEM instrument, is used to chemically map the neutrophils and NETs. We could clearly observe the NETs in PEEM and XPS mode. Quantum Dots (QDots, CdSe based) was used to trigger NETs. We track down the Quantum Dots with the element specific mapping. In the next paper we further explored how to extract new information with this advanced instrument that is traditionally is used for material- and surface science, and just recently deliver results in imaging and visualization within life sciences. Ultrathin slices of neutrophils where made special focus was given to the research work developing strategies to obtain and extract additional information from inside the neutrophils. These are pilot studies and show great potential to get chemical information in a label free way and is a good complement to fluorescence, SEM and TEM. We then made an in-depth investigation on the mechanisms how nanoparticles interact with neutrophils, with special focus on processes triggering NETs formation. Using QDots as a model system we could show that the NETs release is strongly dependent on the uptake of the nanoparticles. We used fluorescence and TEM to investigate where the QDots uptake and to identify the pattern where they finally end up. We clearly observed them inside vesicles in the inner part of the cell and even within the NETs structure giving proof that the uptake of QDots play an important role of the NETs formation. In the last paper we expanded the study and exposed the cells to Iron Oxide NPs (FeNP) Here we developed a strategy how to alternate the magnetic field control the direction of the NETs. We could manipulate live NETs with a magnetic field and made observations that parts of the NETs are static and some clearly mobile, still with an internal memory to find its initial structure just after release. TEM studies revealed that, like the QDots, the FeNP end up inside the NETs. In conclusion in this thesis work, detailed processes are explored on neutrophils and their NETs formation with new unconventional methods and how neutrophils and nanoparticles interact with respect to NETs. 

    List of papers
    1. New Tools for Imaging Neutrophils: Work Function Mapping and Element-Specific, Label-Free Imaging of Cellular Structures
    Open this publication in new window or tab >>New Tools for Imaging Neutrophils: Work Function Mapping and Element-Specific, Label-Free Imaging of Cellular Structures
    2021 (English)In: Nano letters (Print), ISSN 1530-6984, E-ISSN 1530-6992, Vol. 21, no 1, p. 222-229Article in journal (Refereed) Published
    Abstract [en]

    Photoemission electron microscopy and imaging X-ray photoelectron spectroscopy are today frequently used to obtain chemical and electronic states, chemical shifts, work function profiles within the fields of surface- and material sciences. Lately, because of recent technological advances, these tools have also been valuable within life sciences. In this study, we have investigated the power of photoemission electron microscopy and imaging X-ray photoelectron spectroscopy for visualization of human neutrophil granulocytes. These cells, commonly called neutrophils, are essential for our innate immune system. We hereby investigate the structure and morphology of neutrophils when adhered to gold and silicon surfaces. Energy-filtered imaging of single cells are acquired. The characteristic polymorphonuclear cellular nuclei divided into 2-S lobes is visualized. Element-specific imaging is achieved based on O 1s, P 2p, C 1s, Si 2p, and N is core level spectra, delivering elemental distribution with submicrometer resolution, illustrating the strength of this type of cellular morphological studies.

    Place, publisher, year, edition, pages
    American Chemical Society (ACS), 2021
    Keywords
    PEEM; imaging XPS; work function mapping; elemental imaging; neutrophils
    National Category
    Atom and Molecular Physics and Optics
    Identifiers
    urn:nbn:se:liu:diva-174157 (URN)10.1021/acs.nanolett.0c03554 (DOI)000611082000031 ()33263404 (PubMedID)
    Note

    Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University [SFO-Mat-LiU 2009-00971]; Swedish Research Council VRSwedish Research Council [2019-02409]; Knut and Alice Wallenberg Foundation KAWKnut & Alice Wallenberg Foundation [2014.0276]; CTS [CTS 18:399 19:379]; Centre in Nanoscience and Nanotechnology at LiTH (CeNano) at Linkoping University

    Available from: 2021-03-15 Created: 2021-03-15 Last updated: 2022-02-07
    2. Neutrophils Activated by Nanoparticles and Formation of Neutrophil Extracellular Traps: Work Function Mapping and Element Specific Imaging
    Open this publication in new window or tab >>Neutrophils Activated by Nanoparticles and Formation of Neutrophil Extracellular Traps: Work Function Mapping and Element Specific Imaging
    2019 (English)In: Analytical Chemistry, ISSN 0003-2700, E-ISSN 1520-6882, Vol. 91, no 21, p. 13514-13520Article in journal (Refereed) Published
    Abstract [en]

    Photoemission electron microscopy (PEEM) and imaging X-ray photoelectron spectroscopy (XPS) have over the years been powerful tools in classical surface physics and material sciences, and due to recent technological advances, their uses within other fields/disciplines are rapidly growing. Lately, the XPS/PEEM based elemental analysis and characterization in imaging mode, with exquisite spatial resolution and high sensitivity, has shown the potential to deliver new mechanistic insights in cell-biology/medicine. In this work, the aim was to visualize biological processes on the cellular level, with the additional dimension of topographical morphology and element specific information, mapping chemical composition and chemical states. This is hereby demonstrated by combined PEEM and imaging XPS investigation of neutrophils and their activation processes, where fluorescence microscopy commonly used in biology is used for benchmarking. Neutrophils are phagocytic cells and are vital components in the human immune system, with the fundamental role of fighting invading pathogens. They are capable of ingesting microorganisms or particles, and in order to capture and trap foreign objects, one of their strategies is to release nuclear DNA by the formation of extracellular web-like traps (NETs). Here, we report how neutrophils are triggered by controlled nanoparticle (NP) exposure. The neutrophils and NETs formation are imaged in the presence of NPs, and we report the elemental composition of single cells and the structure of NETs. Cellular uptake of nanoparticles is proven and the states just before and after NETs release are imaged, as well as visualization of the extraordinary capability for mass transport at distances 10 times or more than the size of the cell itself. This method paves the way for element specific imaging of biorelated cells on surfaces as well as nanoparticle tracking in the submicro- and nanoregions.

    Place, publisher, year, edition, pages
    AMER CHEMICAL SOC, 2019
    National Category
    Cell and Molecular Biology
    Identifiers
    urn:nbn:se:liu:diva-162325 (URN)10.1021/acs.analchem.9b02579 (DOI)000495469100028 ()31553180 (PubMedID)
    Note

    Funding Agencies|Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Swedish Research Council VRSwedish Research Council [621-2013-5357]; Knut and Alice Wallenberg Foundation KAWKnut & Alice Wallenberg Foundation [2014.0276]; Centre in Nanoscience and Nanotechnology at LiTH (CeNano) at Linkoping University; CTS [17:478, CTS 18:399]

    Available from: 2019-11-28 Created: 2019-11-28 Last updated: 2022-02-07
    3. Nanoparticle activated neutrophils-on-a-chip: A label-free capacitive sensor to monitor cells at work
    Open this publication in new window or tab >>Nanoparticle activated neutrophils-on-a-chip: A label-free capacitive sensor to monitor cells at work
    Show others...
    2020 (English)In: Sensors and actuators. B, Chemical, ISSN 0925-4005, E-ISSN 1873-3077, SENSORS AND ACTUATORS B-CHEMICAL, Vol. 313, article id 128020Article in journal (Refereed) Published
    Abstract [en]

    Neutrophil granulocytes are the most abundant white blood cells in mammals and vital components of the immune system. They are involved in the early phase of inflammation and in generation of reactive oxygen species. These rapid cell-signaling communicative processes are performed in the time frame of minutes. In this work, the activity and the response of neutrophil granulocytes are monitored when triggered by cerium-oxide based nanoparticles, using capacitive sensors based on Lab-on-a-chip technology. The chip is designed to monitor activation processes of cells during nanoparticle exposure, which is for the first time recorded on-line as alteration of the capacitance. The complementary metal oxide semiconductor engineering chip design is combined with low temperature co-fired ceramic, LTCC, packaging technology. The method is label free and gently measures cells on top of an insulating surface in a weak electromagnetic field, as compared to commonly used four-point probes and impedance spectroscopy electric measurements where electrodes are in direct contact with the cells. In summary, this label free method is used to measure oxidative stress of neutrophil granulocytes in real time, minute by minute and visualize the difference in moderate and high cellular workload during exposure of external triggers. It clearly shows the capability of this method to detect cell response during exposure of external triggers. In this way, an informationally dense non-invasive method is obtained, to monitor cells at work.

    Place, publisher, year, edition, pages
    Elsevier, 2020
    Keywords
    Complementary metal oxide semiconductor (CMOS); Low temperature co-fired ceramic (LTCC) packaging; Lab-on-a-chip; Neutrophil granulocytes; Capacitive sensor; Cerium oxide nanoparticles
    National Category
    Immunology
    Identifiers
    urn:nbn:se:liu:diva-165522 (URN)10.1016/j.snb.2020.128020 (DOI)000526287200022 ()2-s2.0-85082944740 (Scopus ID)
    Note

    Funding Agencies|Swedish Research CouncilSwedish Research Council [621-2013-5357, 2019-02409]; Swedish Government Strategic Research Area in Materials Science on Functional Mat erials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Knut and Alice Wallenberg FoundationKnut & Alice Wallenberg Foundation [2012.0083CTS 18: 399]; Centre in Nano Science and Nano technology at LiTH (CeNano) at Linkoping University; COST Action EuNetAir "European Network on New Sensing Technologies for Air-Pollution Control and Environmental Sustainability" [TD1105]; Academy of Finland (ClintoxNP project)Academy of Finland [268944]; TEKES (Chempack project) [1427/31/2010]

    Available from: 2020-05-06 Created: 2020-05-06 Last updated: 2022-02-16Bibliographically approved
  • 43.
    Buyanova, Irina A
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Photon upconversion promoted by defects in low-dimensional semiconductor nanostructures2018In: Defects in Advanced Electronic Materials and Novel Low Dimensional Structures / [ed] Jan Stehr, Irina Buyanova and Weimin Chen, UK: Elsevier, 2018, p. 189-210Chapter in book (Refereed)
    Abstract [en]

    The ability to convert several low-energy photons into a single higher-energy photon is of significant importance in diverse fields ranging from imaging and biological labeling to optoelectronics and photovoltaics. The possibility to realize this phenomenon on the nanoscale can provide an additional degree of freedom in engineering electronic properties of materials and would allow deliberate manipulation and optimization of the upconversion processes. The purpose of this chapter is to provide a review of physical mechanisms that govern the photon upconversion in semiconductor nanostructures. Taking into account a large number of comprehensive reviews on this topic, our main focus is on photon upconversion mediated by defects, which is far less explored so far but provides a viable and attractive alternative for achieving efficient photon upconversion without involving doping.

  • 44.
    Buyanova, Irina
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Chen, Weimin
    Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry. Linköping University, Faculty of Science & Engineering. Linköping University, Department of Physics, Chemistry and Biology, Functional Electronic Materials.
    Ishikawa, F.
    Ehime University, Japan.
    Tu, C. W.
    University of Calif San Diego, USA.
    Novel GaNAs and GaNP-based Nanowires - Promising Materials for Optoelectronics and Photonics2016In: 2016 IEEE 16TH INTERNATIONAL CONFERENCE ON NANOTECHNOLOGY (IEEE-NANO), IEEE , 2016, p. 38-41Conference paper (Refereed)
    Abstract [en]

    In this paper we review our recent results on optical properties of coaxial nanowires (NWs) based on dilute nitride alloys, such as GaAsN and GaNP. We show that these structures have a high structural and optical quality, and can potentially be used as polarized nano-scale light sources that emit linearly polarized light with the polarization direction perpendicular to the wire axis even in zincblende NWs of various diameters. We also demonstrate that, though the GaNxP1-x alloys have rather wide bandgap energies of 1.9 - 2.3 eV, the coaxial GaNP NWs absorb infrared light via two-step two-photon absorption.

  • 45.
    Bäckdahl, Thomas
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    Multipole moments of axisymmetric spacetimes2006Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis we study multipole moments of axisymmetric spacetimes. Using the recursive definition of the multipole moments of Geroch and Hansen we develop a method for computing all multipole moments of a stationary axisymmetric spacetime without the use of a recursion. This is a generalisation of a method developed by Herberthson for the static case.

    Using Herberthson’s method we also develop a method for finding a static axisymmetric spacetime with arbitrary prescribed multipole moments, subject to a specified convergence criteria. This method has, in general, a step where one has to find an explicit expression for an implicitly defined function. However, if the number of multipole moments are finite we give an explicit expression in terms of power series.

    List of papers
    1. Static axisymmetric spacetimes with prescribed multipole moments
    Open this publication in new window or tab >>Static axisymmetric spacetimes with prescribed multipole moments
    2005 (English)In: Classical and Quantum Gravity, ISSN 0264-9381, Vol. 22, no 9, p. 1607-1621Article in journal (Refereed) Published
    Abstract [en]

    In this paper we develop a method of finding the static axisymmetric spacetime corresponding to any given set ofmultipolemoments. In addition to an implicit algebraic form for the general solution, we also give a power series expression for all finite sets of multipole moments. As conjectured by Geroch we prove in the special case of axisymmetry, that there is a static spacetime for any given set of multipole moments subject to a (specified) convergence criterion. We also use this method to confirm a conjecture of Hernández-Pastora and Martín concerning the monopole–quadrupole solution.

    Keywords
    static, axisymmetric, exact solution, multipole moments, spacetime, algebraic equation
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-13749 (URN)10.1088/0264-9381/22/9/009 (DOI)
    Available from: 2006-01-12 Created: 2006-01-12 Last updated: 2024-01-10
    2. Explicit multipole moments of stationary axisymmetric spacetimes
    Open this publication in new window or tab >>Explicit multipole moments of stationary axisymmetric spacetimes
    2005 (English)In: Classical and Quantum Gravity, ISSN 0264-9381, Vol. 22, no 17, p. 3585-3594Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we study multipole moments of axisymmetric stationary asymptotically flat spacetimes. We show how the tensorial recursion of Geroch and Hansen can be reduced to a recursion of scalar functions. We also demonstrate how a careful choice of conformal factor collects all moments into one complex-valued function on , where the moments appear as the derivatives at 0. As an application, we calculate the moments of the Kerr solution. We also discuss the freedom in choosing the potential for the moments.

    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-13750 (URN)10.1088/0264-9381/22/17/017 (DOI)
    Available from: 2006-01-12 Created: 2006-01-12 Last updated: 2024-01-10
    Download full text (pdf)
    FULLTEXT01
  • 46. Order onlineBuy this publication >>
    Bäckdahl, Thomas
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    Multipole Moments of Stationary Spacetimes2008Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    In this thesis we study the relativistic multipole moments for stationary asymptotically flat spacetimes as introduced by Geroch and Hansen. These multipole moments give an asymptotic description of the gravitational field in a coordinate independent way.

    Due to this good description of the spacetimes, it is natural to try to construct a spacetime from only the set of multipole moments. Here we present a simple method to do this for the static axisymmetric case. We also give explicit solutions for the cases where the number of non-zero multipole moments are finite. In addition, for the general stationary axisymmetric case, we present methods to generate solutions.

    It has been a long standing conjecture that the multipole moments give a complete characterization of the stationary spacetimes. Much progress toward a proof has been made over the years. However, there is one remaining difficult task: to prove that a spacetime exists with an a-priori given arbitrary set of multipole moments subject to some given condition.

    Here we present such a condition for the axisymmetric case, and prove that it is both necessary and sufficient. We also extend this condition to the general case without axisymmetry, but in this case we only prove the necessity of our condition.

    List of papers
    1. Static axisymmetric spacetimes with prescribed multipole moments
    Open this publication in new window or tab >>Static axisymmetric spacetimes with prescribed multipole moments
    2005 (English)In: Classical and Quantum Gravity, ISSN 0264-9381, Vol. 22, no 9, p. 1607-1621Article in journal (Refereed) Published
    Abstract [en]

    In this paper we develop a method of finding the static axisymmetric spacetime corresponding to any given set ofmultipolemoments. In addition to an implicit algebraic form for the general solution, we also give a power series expression for all finite sets of multipole moments. As conjectured by Geroch we prove in the special case of axisymmetry, that there is a static spacetime for any given set of multipole moments subject to a (specified) convergence criterion. We also use this method to confirm a conjecture of Hernández-Pastora and Martín concerning the monopole–quadrupole solution.

    Keywords
    static, axisymmetric, exact solution, multipole moments, spacetime, algebraic equation
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-13749 (URN)10.1088/0264-9381/22/9/009 (DOI)
    Available from: 2006-01-12 Created: 2006-01-12 Last updated: 2024-01-10
    2. Explicit multipole moments of stationary axisymmetric spacetimes
    Open this publication in new window or tab >>Explicit multipole moments of stationary axisymmetric spacetimes
    2005 (English)In: Classical and Quantum Gravity, ISSN 0264-9381, Vol. 22, no 17, p. 3585-3594Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we study multipole moments of axisymmetric stationary asymptotically flat spacetimes. We show how the tensorial recursion of Geroch and Hansen can be reduced to a recursion of scalar functions. We also demonstrate how a careful choice of conformal factor collects all moments into one complex-valued function on , where the moments appear as the derivatives at 0. As an application, we calculate the moments of the Kerr solution. We also discuss the freedom in choosing the potential for the moments.

    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-13750 (URN)10.1088/0264-9381/22/17/017 (DOI)
    Available from: 2006-01-12 Created: 2006-01-12 Last updated: 2024-01-10
    3. Calculation of, and bounds for, the multipole moments of stationary spacetimes
    Open this publication in new window or tab >>Calculation of, and bounds for, the multipole moments of stationary spacetimes
    2006 (English)In: Classical and Quantum Gravity, ISSN 0264-9381, Vol. 23, no 20, p. 5997-6006Article in journal (Refereed) Published
    Abstract [en]

    In this paper, the multipole moments of stationary asymptotically flat spacetimes are considered. We show how the tensorial recursion of Geroch and Hansen can be replaced by a scalar recursion on . We also give a bound on the multipole moments. This gives a proof of the 'necessary part' of a long-standing conjecture due to Geroch.

    Keywords
    multipole moments, stationary, spacetimes
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-13158 (URN)10.1088/0264-9381/23/20/019 (DOI)
    Available from: 2008-05-21 Created: 2008-05-21 Last updated: 2024-01-10
    4. Axisymmetric stationary solutions with arbitrary multipole moments
    Open this publication in new window or tab >>Axisymmetric stationary solutions with arbitrary multipole moments
    2007 (English)In: Classical and Quantum Gravity, ISSN 0264-9381, Vol. 24, no 9, p. 2205-2215Article in journal (Refereed) Published
    Abstract [en]

    In this paper, the problem of finding an axisymmetric stationary spacetime from a specified set of multipole moments is studied. The condition on the multipole moments, for the existence of a solution, is formulated as a convergence condition on a power series formed from the multipole moments. The methods in this paper can also be used to give approximate solutions to any order, as well as estimates on each term of the resulting power series.

    Keywords
    multipole moments, statinary, axisymmetric, existence, spacetime
    National Category
    Mathematics
    Identifiers
    urn:nbn:se:liu:diva-13159 (URN)10.1088/0264-9381/24/9/004 (DOI)
    Available from: 2008-05-21 Created: 2008-05-21 Last updated: 2009-04-24
    Download full text (pdf)
    FULLTEXT01
    Download (pdf)
    COVER01
  • 47.
    Bäckström, Louise
    Linköping University, Department of Physics, Chemistry and Biology.
    In Situ Heating During XRD Measurements as a Method to Study Recrystallisation of Aluminium Alloy AA30032018Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Recrystallisation is an important topic in the metal industry since the process may drastically alter the properties of the materials subjected to it. By controlling the recrystallisation process, the material properties can be adjusted as desired, which could lead to stronger materials and hence lighter constructions, decreasing our material consumption. This is currently regulated using softening curves complied from tensile tests, a method which does not show the degree of recrystallisation of a metal. This thesis work therefore explores the possibility to characterise the recrystallisation process using in situ X-ray diffraction, XRD, during heating.The method proposed is using in situ heat treatments of aluminium samples combined with XRD measurements. The results show that it is possible to follow the recrystallisation process of rolled aluminium alloy AA3003 by using in situ XRD during heating, a discovery that could facilitate development and understanding of new materials. Nevertheless, further investigations of the subject is required before the method will be profitable.

    Download full text (pdf)
    fulltext
  • 48.
    Cabello, Adan
    et al.
    University of Seville, Spain.
    Gu, Mile
    Nanyang Technology University, Singapore; National University of Singapore, Singapore.
    Guehne, Otfried
    University of Siegen, Germany.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Wiesner, Karoline
    University of Bristol, England.
    Thermodynamical cost of some interpretations of quantum theory2016In: PHYSICAL REVIEW A, ISSN 2469-9926, Vol. 94, no 5, article id 052127Article in journal (Refereed)
    Abstract [en]

    The interpretation of quantum theory is one of the longest-standing debates in physics. Type I interpretations see quantum probabilities as determined by intrinsic properties of the observed system. Type II see them as relational experiences between an observer and the system. It is usually believed that a decision between these two options cannot be made simply on purely physical grounds but requires an act of metaphysical judgment. Here we show that, under some assumptions, the problem is decidable using thermodynamics. We prove that type I interpretations are incompatible with the following assumptions: (i) The choice of which measurement is performed can be made randomly and independently of the system under observation, (ii) the system has limited memory, and (iii) Landauers erasure principle holds.

    Download full text (pdf)
    fulltext
  • 49.
    Cai, Xia
    et al.
    Fudan Univ, Peoples R China; Shanghai Normal Univ, Peoples R China; Fudan Univ, Peoples R China.
    Liu, Fengcai
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Yu, Anran
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Qin, Jiajun
    Linköping University, Department of Physics, Chemistry and Biology, Electronic and photonic materials. Linköping University, Faculty of Science & Engineering.
    Hatamvand, Mohammad
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Ahmed, Irfan
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Luo, Jiayan
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Zhang, Yiming
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Zhang, Hao
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China; Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Zhan, Yiqiang
    Fudan Univ, Peoples R China; Fudan Univ, Peoples R China.
    Data-driven design of high-performance MASn(x)Pb(1-x)I(3) perovskite materials by machine learning and experimental realization2022In: Light: Science & Applications, ISSN 2095-5545, E-ISSN 2047-7538, Vol. 11, no 1, article id 234Article in journal (Refereed)
    Abstract [en]

    The photovoltaic performance of perovskite solar cell is determined by multiple interrelated factors, such as perovskite compositions, electronic properties of each transport layer and fabrication parameters, which makes it rather challenging for optimization of device performances and discovery of underlying mechanisms. Here, we propose and realize a novel machine learning approach based on forward-reverse framework to establish the relationship between key parameters and photovoltaic performance in high-profile MASn(x)Pb(1-x)I(3) perovskite materials. The proposed method establishes the asymmetrically bowing relationship between band gap and Sn composition, which is precisely verified by our experiments. Based on the analysis of structural evolution and SHAP library, the rapid-change region and low-bandgap plateau region for small and large Sn composition are explained, respectively. By establishing the models for photovoltaic parameters of working photovoltaic devices, the deviation of short-circuit current and opencircuit voltage with band gap in defective-zone and low-bandgap-plateau regions from Shockley-Queisser theory is captured by our models, and the former is due to the deep-level traps formed by crystallographic distortion and the latter is due to the enhanced susceptibility by increased Sn (4+ )content. The more difficulty for hole extraction than electron is also concluded in the models and the prediction curve of power conversion efficiency is in a good agreement with Shockley-Queisser limit. With the help of search and optimization algorithms, an optimized Sn:Pb composition ratio near 0.6 is finally obtained for high-performance perovskite solar cells, then verified by our experiments. Our constructive method could also be applicable to other material optimization and efficient device development.

    Download full text (pdf)
    fulltext
  • 50.
    Carine, J.
    et al.
    Univ Concepcion, Chile; Univ Concepcion, Chile.
    Canas, G.
    Univ Bio Bio, Chile.
    Skrzypczyk, P.
    Univ Bristol, England.
    Supic, I
    Barcelona Inst Sci and Technol, Spain.
    Guerrero, N.
    Univ Concepcion, Chile; Univ Concepcion, Chile.
    Garcia, T.
    Univ Concepcion, Chile; Univ Concepcion, Chile.
    Pereira, L.
    Univ Concepcion, Chile; Univ Concepcion, Chile.
    Prosser, M. A. S.
    Univ La Frontera, Chile.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Delgado, A.
    Univ Concepcion, Chile.
    Walborn, S. P.
    Univ Concepcion, Chile; Univ Fed Rio de Janeiro, Brazil.
    Cavalcanti, D.
    Barcelona Inst Sci and Technol, Spain.
    Lima, G.
    Univ Concepcion, Chile.
    Multi-core fiber integrated multi-port beam splitters for quantum information processing2020In: Optica, E-ISSN 2334-2536, Vol. 7, no 5, p. 542-550Article in journal (Refereed)
    Abstract [en]

    Multi-port beam splitters are cornerstone devices for high-dimensional quantum information tasks, which can outperform the two-dimensional ones. Nonetheless, the fabrication of such devices has proven to be challenging with progress only recently achieved with the advent of integrated photonics. Here, we report on the production of high-quality N x N (with N = 4, 7) multi-port beam splitters based on a new scheme for manipulating multi-core optical fibers. By exploring their compatibility with optical fiber components, we create four-dimensional quantum systems and implement the measurement-device-independent random number generation task with a programmable four-arm interferometer operating at a 2 MHz repetition rate. Due to the high visibilities observed, we surpass the one-bit limit of binary protocols and attain 1.23 bits of certified private randomness per experimental round. Our result demonstrates that fast switching, low loss, and high optical quality for high-dimensional quantum information can be simultaneously achieved with multi-core fiber technology. (C) 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement

1234567 1 - 50 of 334
CiteExportLink to result list
Permanent link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • oxford
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf