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  • 1.
    Josefsson, Mattias
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    3D camera with built-in velocity measurement2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In today's industry 3D cameras are often used to inspect products. The camera produces both a 3D model and an intensity image by capturing a series of profiles of the object using laser triangulation. In many of these setups a physical encoder is attached to, for example, the conveyor belt that the product is travelling on. The encoder is used to get an accurate reading of the speed that the product has when it passes through the laser. Without this, the output image from the camera can be distorted due to a variation in velocity.

    In this master thesis a method for integrating the functionality of this physical encoder into the software of the camera is proposed. The object is scanned together with a pattern, with the help of this pattern the object can be restored to its original proportions.

  • 2.
    Mesgarzadeh, Behzad
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A 24-mW, 0.02-mm2, 1.5-GHz DLL-Based Frequency Multiplier in 130-nm CMOS2006In: Proceedings of the IEEE International System-on-Chip Conference (SoCC), 2006, 257-260 p.Conference paper (Other academic)
    Abstract [en]

    This paper presents a low-power small-area DLL-based frequency multiplier. Instead of using edge combiner-based clock synthesis scheme, the proposed frequency multiplier utilizes a ring oscillator, which is controlled by a DLL. An injection-locked slave ring oscillator is used for jitter suppression. The implementation of the proposed structure in 130-nm CMOS occupies an area of 0.02 mm2. It operates in the frequency range of 100 MHz to 1.5 GHz while consuming 24-mW power from a 1.2-V supply at 1.5 GHz. The measured output phase noise at 1.5 GHz is ¿100.1 dBc/Hz at a 4-MHz frequency offset.

  • 3. Danielsson, E
    et al.
    Domeij, M
    Lee, HS
    Zetterling, CM
    Ostling, M
    Schoner, A
    Hallin, Christer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology.
    A 4H-SiC BJT with an epitaxially regrown extrinsic base layer2005In: Materials Science Forum, ISSN 0255-5476, Vol. 483, 905-908 p.Article in journal (Refereed)
    Abstract [en]

    4H-SiC BJTs were fabricated using epitaxial regrowth instead of ion implantation to form a highly doped extrinsic base layer necessary for a good base ohmic contact. A remaining p(+) regrowth spacer at the edge of the base-emitter junction is proposed to explain a low current gain of 6 for the BJTs. A breakdown voltage of 1000 V was obtained for devices with Al implanted JTE.

  • 4.
    Lindström, Tom
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    Grear, Daniel A.
    Colorado State University, USA .
    Buhnerkempe, Michael
    Colorado State University, USA .
    Webb, Colleen T.
    Colorado State University, USA .
    Miller, Ryan S.
    US Anim and Plant Health Inspect Serv, CO USA .
    Portacci, Katie
    US Anim and Plant Health Inspect Serv, CO USA .
    Wennergren, Uno
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Biology. Linköping University, The Institute of Technology.
    A Bayesian Approach for Modeling Cattle Movements in the United States: Scaling up a Partially Observed Network2013In: PLoS ONE, ISSN 1932-6203, Vol. 8, no 1Article in journal (Refereed)
    Abstract [en]

    Networks are rarely completely observed and prediction of unobserved edges is an important problem, especially in disease spread modeling where networks are used to represent the pattern of contacts. We focus on a partially observed cattle movement network in the U.S. and present a method for scaling up to a full network based on Bayesian inference, with the aim of informing epidemic disease spread models in the United States. The observed network is a 10% state stratified sample of Interstate Certificates of Veterinary Inspection that are required for interstate movement; describing approximately 20,000 movements from 47 of the contiguous states, with origins and destinations aggregated at the county level. We address how to scale up the 10% sample and predict unobserved intrastate movements based on observed movement distances. Edge prediction based on a distance kernel is not straightforward because the probability of movement does not always decline monotonically with distance due to underlying industry infrastructure. Hence, we propose a spatially explicit model where the probability of movement depends on distance, number of premises per county and historical imports of animals. Our model performs well in recapturing overall metrics of the observed network at the node level (U.S. counties), including degree centrality and betweenness; and performs better compared to randomized networks. Kernel generated movement networks also recapture observed global network metrics, including network size, transitivity, reciprocity, and assortativity better than randomized networks. In addition, predicted movements are similar to observed when aggregated at the state level (a broader geographic level relevant for policy) and are concentrated around states where key infrastructures, such as feedlots, are common. We conclude that the method generally performs well in predicting both coarse geographical patterns and network structure and is a promising method to generate full networks that incorporate the uncertainty of sampled and unobserved contacts.

  • 5.
    Svensson, Marlene
    Linköping University, Department of Management and Engineering.
    A CFD Investigation of a Generic Bump and its Application to a Diverterless Supersonic Inlet2008Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This is a Master Thesis done at the Swedish Defence Research Agency with the purpose to design and investigate how different geometries of a compression surface integrated with an intake affects the performance such as distortion, boundary layer diversion, pressure recovery and deceleration of speed.

    The work was divided in two parts. In the first part, CFD calculations using the FOI developed Edge 4.1 code were made for the compression surfaces alone. In the second part the most promising design was integrated with an intake. Two more bumps with the intake were modelled and the three geometries were compared to the intake without bump. Surface flow, deceleration of Mach number, pressure recovery, mass flow, boundary layer diversion, lift and drag were the factors chosen to be examined, boundary layer diversion and pressure recovery being the two most vital.

  • 6.
    Fritzin, Jonas
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Svensson, Christer
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A Class-D outphasing RF amplifier with harmonic suppression in 90nm CMOS2010In: Proceedings of the ESSCIRC, 2010, Seville: IEEE , 2010, 310-313 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a low-power Class-D stage featuring a new harmonic reduction technique, which cancels the 3rd harmonic and reduces the 5th harmonic. The technique creates a voltage level of VDD/2 from a single supply voltage to shape the drain voltage, uses only digital circuits and eliminates the short-circuit current present in inverter-based Class-D stages. From a single Class-D stage operating at 900MHz, the measured output power is +5.1dBm with Drain Efficiency (DE) and Power-Added Efficiency (PAE) of 73% and 59% for a 1.2V supply, while 2nd to 4th harmonics are measured to be -37dBc without any filtering. Connecting two Class-D stages to a PCB-mounted transformer in an outphasing configuration, the overall amplifier is linear enough to amplify EDGE 8-PSK and WCDMA modulated signals at 900MHz without pre-distortion of the input signals or any other linearization technique.

  • 7.
    Ledin, Staffan
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems.
    A Comparison of Radix-2 Square Root Algorithms Using Digit Recurrence2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    When designing an electronic system, it might be desirable to implement a custom square root calculator unit to ensure quick calculations. The different questions when it comes to square root units are many. What algorithms are there? How are these algorithms implemented? What are the benefits and disadvantages of the different implementations? The goal of this thesis work is to try to answer these questions. In this paper, several different methods of calculating the radix-2 square root by digit recurrence are studied, designed and compared. The three main algorithms that are studied are the restoring square root algorithm, the non-restoring square root algorithm and the SRT (Sweeney, Robertson, Tocher) square root algorithm. They are all designed using the same technology and identical components where applicable. This is done in order to ensure that the comparisons give a fair assessment of the viability of the different algorithms. It is shown that the restoring and non-restoring square root algorithms perform similarly when using 65 nm technology, a 16 bit input, full data rate and 1.2 V power supply. The restoring square root algorithm have a slight edge when the systems are not pipelined, while the non-restoring algorithm performs slightly better when the systems are fully pipelined. The SRT square root algorithm perform worse than the other two in all cases.

  • 8. Sparring Björkstén, Karin
    et al.
    Ekberg, Stefan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Radiation Physics. Östergötlands Läns Landsting, Centre of Surgery and Oncology, Department of Radiation Physics.
    Säfström, Pia
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Medical Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology UHL.
    Dige, N
    Granerus, Göran
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medicine and Care, Clinical Physiology. Östergötlands Läns Landsting, Heart Centre, Department of Clinical Physiology.
    A computerized human reference brain for rCBF/SPET technetium-99m exametazime (HMPAO) investigation of elderly2004In: Clinical Physiology and Functional Imaging, ISSN 1475-0961, Vol. 24, no 4, 196-204 p.Article in journal (Refereed)
    Abstract [en]

    Using the bull's eye approach, a reference brain from the single photon emission tomography (SPET) images of 10 subjects aged 62-81 years with excellent mental and physical health was constructed. SPET images were acquired twice, 1 week apart, using a single detector rotating gamma camera collecting 64 planar images over a 360° orbit. The centre of each transaxial slice was first defined with an automatic edge detecting algorithm applied to an anterior-posterior and a side profile of the brain. Each slice was divided into 40 sectors. Maximum counts/pixel in each sector was picked. The 40 maximum count values from one transaxial slice were allowed to form a horizontal row in a new parametric image on the x-axis and slice number from the vertex to the basal parts of the brain on the y-axis. This new image was scaled to a 64 × 16 pixel matrix by interpolation, which meant a normalization of all studies to the same size. The parametric image in each subject was scaled with regard to intensity by a factor calculated by a normalization procedure using the least squares analysis. Mean and SD for each pixel were calculated, thereby constructing a 'mean parametric image', and a 'SD parametric image'. These two images are meant to be used as the reference brain for evaluation of patient studies. This method can be used for objective measurements of diffuse brain changes and for pattern recognition in larger groups of patients. Statistical multifactorial analysis of parameters used for acquisition and data processing is possible. © 2004 Blackwell Publishing Ltd.

  • 9.
    Häggblad, Erik
    et al.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Petersson, Henrik
    Linköping University, Department of Physics, Chemistry and Biology, Applied Physics. Linköping University, The Institute of Technology.
    Ilias, Michail A.
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    Anderson, Chris D
    Linköping University, Department of Clinical and Experimental Medicine, Dermatology and Venerology. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Heart and Medicine Centre, Department of Dermatology and Venerology in Östergötland.
    Salerud, Göran
    Linköping University, Department of Biomedical Engineering, Biomedical Instrumentation. Linköping University, The Institute of Technology.
    A diffuse reflectance spectroscopic study of UV-induced erythematous reaction across well-defined borders in human skin2010In: Skin research and technology, ISSN 0909-752X, E-ISSN 1600-0846, Vol. 16, no 3, 283-290 p.Article in journal (Refereed)
    Abstract [en]

    Introduction The colour of tissue is often of clinicaluse in the diagnosis of tissue homeostasis andphysiological responses to various stimuli.Determining tissue colour changes and borders,however, often poses an intricate problem and visualexamination, constituting clinical praxis, does notallow them to be objectively characterized orquantified. Demands for increased inter- and intraobserverreproducibility have been incentives for theintroduction of objective methods and techniques fortissue colour (e.g. erythema) evaluation. The aim ofthe present paper was to study the border zone of anUVB provoked erythematous response of humanskin in terms of blood volume and oxygenationmeasured by means of diffuse reflectancespectroscopy using a commercial probe.

    Material and Methods A provocation model, basedon partial masking of irradiated skin areas, definestwo erythema edges at every skin site responding tothe UV irradiation. In every subject, 5 test sites wereexposed with a constant UV light irradiance (14mW/cm2), but with different exposures times (0, 3,6, 9, 12 seconds). An analysis of the spectral datameasured across the two edges was performed for every scan line. The oxygenized and deoxygenizedhemoglobin contents were estimated in everymeasurement point, using a modified Beer-Lambertmodel.

    Results The fit of the experimental data to the model derived by the modified Beer-Lambert law was excellent (R2>0.95). Analyzing data for the chromophore content showed that the erythematous response in provoked areas is dominated by the increase in oxyhemoglobin. The width for the left and right border zone was estimated to 1.81±0.93 mm and 1.90±0.88 mm respectively (M±SD). The unprovoked area between the two edges was estimated to 0.77±0.68 mm.

    Conclusion While the chosen data analysis performed satisfactory, the ability of the probe design to differentiate spatial aspects of a reaction with abrupt borders was found to be suboptimal resulting in a probable overestimation of the erythematous edge slope. Probe modification or imaging are possible solutions.

  • 10. Berggren, Martin
    et al.
    Ekström, Sven-Erik
    Uppsala universitet, Avdelningen för teknisk databehandling.
    Nordström, Jan
    Uppsala universitet, Avdelningen för teknisk databehandling.
    A discontinuous Galerkin extension of the vertex-centered edge-based finite volume method2009In: Communications in Computational Physics, ISSN 1815-2406, Vol. 5, 456-468 p.Article in journal (Refereed)
  • 11.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Sajid, Muhammad
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Siddiqui, Imran
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks2012In: 2012 IEEE INTERNATIONAL CONFERENCE ON COMMUNICATIONS (ICC), Piscataway, NJ, USA: IEEE , 2012, 6525-6529 p.Conference paper (Refereed)
    Abstract [en]

    A distributed, load-aware, joint power and frequency allocation protocol is introduced for LTE-based cellular networks, and system-level simulations are performed. Our proposed scheme aims to cooperatively limit the impact of Fractional Frequency Reuse (FFR) on the center users throughput compared to the Reuse 1 scheme, while providing sufficient throughput for the edge users. This is achieved through an asynchronous, lightweight scheme of local message exchange between neighboring LTE eNodeBs. The proposed scheme facilitates a type of "bargain" where an overloaded sector requests permission to utilize its neighbors edge bands for its center users at a limited set of transmit power levels. Grants are generated at each neighbor by solving a small-scale optimization problem. Using an LTE simulator we evaluate our scheme on a network with 21 sectors of varying load patterns. The proposed schemes performance for center users is consistently improved with respect to FFR-3, while for edge users the performance degradation is controlled by a parameter we set in the optimization problems definitions; compared to Reuse 1 edge users still have gains. Specifically, we observed up to a 46% gain in the sectors center throughput with a cost below 9% at the edges when compared to the classic FFR scheme, while the overall system throughput goes up by up to 26% in heavily loaded scenarios.

  • 12.
    Sajid, Muhammad
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Siddiqui, Imran
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A distributed, load-aware, power and frequency bargaining protocol for LTE-based networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this thesis a distributed, dynamic, load aware, joint power and frequency allocation protocol for 4G networks along with system-level simulated results are presented. In all cellular networks, a key limiting factor for throughput is inter-cell interference, especially at the cell edges. Several methods have been proposed and adopted in each mobile network generation to cancel or suppress its effects, whereas each method has its drawbacks in terms of receiver complexity or additional control nodes. However, the proposed protocol presented here does not impose any architectural changes.  In 4G networks such as LTE, the choice of OFDMA for the air interface has paved the way for selective frequency and power allocation in the available spectrum. Taking advantage of this opportunity, fractional frequency reuse (FFR) has been proposed in OFDMA based mobile networks in order to reduce the throughput loss at the cell edges due to inter-cell interference. In FFR, center users lose part of available spectrum that is dedicated to the edge users.  Our protocol aims to minimize this loss of center users incurred by FFR, at the cost of minimal degradation at the edges.

    An eNodeB, only when overloaded, requests its neighbours’ edge band to be used for its center users at a reduced power level. This is done via small message exchange between the eNodeBs. The neighbors of the overloaded eNodeBs solve a small local knapsack problem to decide whether band lending is feasible or not. A distinguishing feature of this protocol is the power level adjustment for the borrowed band, which is mutually decided by the borrower and lender. The band is released when it is not needed or it is causing unacceptable loss to the lender. The implementation is done in a Matlab based LTE system level simulator. For the implementation of our protocol in the simulator, starting point was implementation of FFR-3 functionality, a prerequisite and a baseline for comparison with our protocol.

    Results are compared among three different setups of re-use1, FFR-3 and our protocol by varying number of overloaded eNodeBs for various numbers of scenarios and the comparison is made based on the center users’ throughput, edge users’ throughput. An estimation of time and protocol overhead is also presented. We have observed center users’ throughput gain up to 46%, at the cost of 9% edge users’ throughput loss, when compared to the classic FFR-3 scheme. The overall system throughput goes up to 26 % in heavily loaded scenario.

     

    The utility of the protocol for an LTE system is evident from the results, which is supported by the dynamic and decentralized nature of the protocol. This ensures better utilization of spectrum, by temporarily allocating more bandwidth where it is needed more.

  • 13.
    Ojani, Amin
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Mesgarzadeh, Behzad
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A DLL-based Injection-Locked Frequency Synthesizer for WiMedia UWB2012In: 2012 IEEE INTERNATIONAL SYMPOSIUM ON CIRCUITS AND SYSTEMS (ISCAS 2012), IEEE , 2012, 2027-2030 p.Conference paper (Refereed)
    Abstract [en]

    A WiMedia ultrawideband (UWB) frequency synthesizer is designed for band group #1. A very fast hopping is achieved by using a delay-locked loop (DLL) architecture which utilizes a novel variable gain voltage-controlled delay line (VCDL) scheme to compensate the phase error generated at the hopping instant. Fast-settling DLL allows an injection-locked oscillator (ILO) to be employed to reduce the current consumption in the edge combiner (EC). Simulated in STM 65-nm CMOS technology, synthesizer hopping time is less than two reference cycles. Phase noise at 3432 MHz is -124 dBc/Hz at 1 MHz offset. The adjacent spur level from the Monte Carlo simulation is -34 dBc. Excluding CML divider, the synthesizer draws 6.7 mW from a 1.2 V supply.

  • 14.
    Solli, Martin
    et al.
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Lenz, Reiner
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    A Font Search Engine for Large Font Databases2011In: ELCVIA Electronic Letters on Computer Vision and Image Analysis, ISSN 1577-5097, Vol. 10, no 1, 24-41 p.Article in journal (Refereed)
    Abstract [en]

    A search engine for font recognition is presented and evaluated. The intended usage is the search in very large font databases. The input to the search engine is an image of a text line, and the output is the name of the font used when rendering the text. After pre-processing and segmentation of the input image, a local approach is used, where features are calculated for individual characters. The method is based on eigenimages calculated from edge filtered character images, which enables compact feature vectors that can be computed rapidly. In this study the database contains 2763 different fonts for the English alphabet. To resemble a real life situation, the proposed method is evaluated with printed and scanned text lines and character images. Our evaluation shows that for 99 % of the queries, the correct font name can be found within the five best matches.

  • 15.
    Karlsson, Magnus
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Håkansson, Pär
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gong, Shaofang
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A Frequency Triplexer for Ultra-wideband Systems Utilizing Combined Broadside- and Edge-coupled Filters2008In: IEEE Transactions on Advanced Packaging, ISSN 1521-3323, Vol. 31, no 4, 794-801 p.Article in journal (Refereed)
    Abstract [en]

    A fully integrated triplexer for multiband ultra-wideband radio is presented. The triplexer utilizes a microstrip network and three combined broadside- and edge-coupled filters. It is fully integrated in a printed circuit board with low requirements on the printed circuit board process tolerance. Three flat subbands in the frequency band 3.1-4.8 GHz have been achieved. The group delay variation within each 500-MHz subband was measured to be around 1 ns. A good agreement between simulation and measurement was obtained.

  • 16.
    Karlsson, Magnus
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gong, Shaofang
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A Frequency-Triplexed Inverted-F Antenna System for Ultra-wide Multi-band Systems 3.1-4.8 GHz2007In: ISAST Transactions on Electronics and Signal Processing, ISSN 1797-2329, Vol. 1, no 1, 95-100 p.Article in journal (Refereed)
    Abstract [en]

    A fully integrated triplex antenna system for multibandUWB 3.1-4.8 GHz is presented. The system utilizes amicrostrip network and three combined broadside- and edgecoupledfilters to connect three inverted-F antennas in parallel.The triplexd antenna system is fully integrated in a printedcircuit board with low requirements on the printed circuit boardprocess tolerance. The group delay variation within the triplexerwas measured to be less than 1 ns. Furthermore, a goodagreement between simulation and measurement results wasobserved.

  • 17.
    Serban, Adriana
    et al.
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Karlsson, Magnus
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    Gong, Shaofang
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A Frequency-triplexed RF Front-end for Ultra-wideband Systems 3.1-4.8 GHz2008In: ISAST Transactions on Electronics and Signal Processing, ISSN 1797-2329, Vol. 1, no 2, 83-88 p.Article in journal (Refereed)
    Abstract [en]

    A multi-band and ultra-wideband (UWB) 3.1-4.8 GHz receiver front-end consisting of a fully integrated filter and triplexer network, and a flat gain low-noise amplifier (LNA) is presented in this paper. The front-end utilizes a microstrip network and three combined broadside- and edge-coupled bandpass filters to connect the three sub-bands. The LNA design employs dual-section input and output microstrip matching networks for wideband operation with a flat power gain and a low noise figure. The system is fully integrated in a four-metal-layer printed circuit board. The measured power gain is 10 dB and the noise figure of the front-end is 6 dB at each center frequency of the three sub-bands. The minimum isolation between the sub-bands is -27 dB and the isolation between the non-neighboring alternate sub-bands is -52 dB. The out-of-band interferer attenuation is below -30 dB.

  • 18.
    Angelakis, Vangelis
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Chen, Lei
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Fully Decentralized and Load-Adaptive Fractional Frequency Reuse Scheme2011In: Modeling, Analysis & Simulation of Computer and Telecommunication Systems (MASCOTS), 2011 IEEE 19th International Symposium on, 2011, 425-428 p.Conference paper (Refereed)
    Abstract [en]

    A new fully decentralized dynamic fractional frequency reuse (FFR)-based scheme for cellular OFDMA networks is introduced. FFR is a technique to mitigate inter-cell interference to improve the throughput of interference-limited users on the cell edge, to the expense of the rest of the cell's users and the aggregate throughput. The proposed scheme aims to limit the FFR-incurred loss of the center users' throughput, while still providing sufficient bandwidth for the cell edge users' communication. This is done by local information sharing and distributed optimization. The resulting flexibility of frequency reuse can be especially beneficial in scenarios with non-uniform and time-varying load. The optimization task is accomplished by solving a knapsack problem in each cell, where the goal is to maximize the center throughput while maintaining acceptable degradation on the cell edge with respect to the original FFR allocation. The performance improvement resulting from the distributed and dynamic FFR scheme is demonstrated by snapshot simulations on an 81-cells network with asymmetric cell load. The proposed scheme achieves up to a 62% gain in cell-center throughput with a cost of no more than 18% at the edges when compared to the classic FFR scheme. The overall system throughput improvement ranges from 22% to 58%.

  • 19.
    Abdul Aziz Hasan Ali, Aamir
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Shahzad, Muhammad Adil
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    A Joint Subcarrier/Power allocation Scheme for OFDMA-based Cellular Networks2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    The assignment of this master thesis consists of initiating power, subcarrier allocation in a dynamic FFR based scheme designed for multi-cell OFDMA networks and to enhance the throughput of all center users in bandwidth hungry borrower cells (overloaded cells) which was previously degraded by original FFR3 scheme as a result of partitioning of system bandwidth into center and edge bands respectively. The method uses band borrowing to compensate center user’s throughput loss in a semi and fully overloaded system. The scheme uses dynamic programming method (0/1 knapsack problem) to bargain an edge band on various power levels and tends to check the best combination (power and sub-carrier) which the system can utilize while still maintaining acceptable throughput loss for the users at the edge of the neighboring cell (lender cell).

    The algorithm consists of generating a borrowing request to neighboring cells for utilizing their edge bands by the overloaded borrower cell if their average center user throughput reaches below a minimum threshold value set in the system. The borrowing method uses 0/1 knapsack problem to capture an edge band based on limiting factors of total cost in average throughput losses by neighbors (Ci) and Un (tolerable mean user edge user throughput loss by lending cell). While solving knapsack problem the lender (neighbors) will check Ci and Un before granting the right to use its edge band. The later stage requires reducing subcarrier power level in order to utilize the lenders edge band using "soft borrower" mode. The borrowed sub-carriers will be activated take power from the original center band sub-carriers of the overloaded cell by taking into account the interference between the lender and the borrower. In case of negative (0) reply from the lender cell after the first request, multiple requests are generated at reduce power level at every step to order to acquire more bands. If a neighbor has band borrowing requests from multiple overloaded base stations, the band will be granted to the one which gives minimal loss in terms of throughput to the lender cell.

    The simulation results are analyzed w.r.t reuse-1 and FFR3 scheme of a multi cell regular and irregular scenarios comprising of lightly to heavily overloaded cells with various subcarrier allocation patterns. An overhead and time assessment is also presented between borrower and lender cells. Simulation results show an increase of 60% in center user’s throughput w.r.t original FFR3 scheme with an acceptable loss of 18% at the edges in complex overloaded scenarios while the overall system throughout increases by 35%.

  • 20.
    Lindén, Erik
    Linköping University, Department of Computer and Information Science, Software and Systems.
    A latency comparison of IoT protocols in MES2017Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Many industries are now moving several of their processes into the cloud computing sphere. One important process is to collect machine data in an effective way. Moving signal collection processes to the cloud instead of on premise raises many questions about performance, scalability, security and cost.This thesis focuses on some of the market leading and cutting edge protocols appropriate for industrial production data collection. It investigates and compares the pros and cons of the protocols with respect to the demands of industrial systems. The thesis also presents examples of how the protocols can be used to collect data all the way to a higher-level system such as ERP or MES.The protocols focused on are MQTT and AMQP (in OPC-UA). The possibilities of OPC-UA in cloud computing is of extra interest to investigate in this thesis due to its increasing usage and development.

  • 21.
    ul Hasan, Kamran
    et al.
    Linköping University, Department of Science and Technology. Linköping University, Faculty of Science & Engineering. CESAT, Islamabad, Pakistan.
    Asif, Muhammad
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology. COMSATS Institute Informat Technology, Lahore, Pakistan.
    Umair Hassan, Muhammad
    COMSATS Institute Informat Technology, Lahore, Pakistan.
    Sandberg, Mats O.
    Acreo AB, Norrköping, Sweden.
    Nour, Omer
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Willander, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, Faculty of Science & Engineering.
    Fagerholm, Siri
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    Strålfors, Peter
    Linköping University, Department of Clinical and Experimental Medicine, Division of Cell Biology. Linköping University, Faculty of Medicine and Health Sciences.
    A Miniature Graphene-based Biosensor for Intracellular Glucose Measurements2015In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 0019-4686, Vol. 174, 574-580 p.Article in journal (Refereed)
    Abstract [en]

    We report on a small and simple graphene-based potentiometric sensor for the measurement of intracellular glucose concentration. A fine borosilicate glass capillary coated with graphene and subsequently immobilized with glucose oxidase (GOD) enzyme is inserted into the intracellular environment of a single human cell. The functional groups on the edge plane of graphene assist the attachment with the free amine terminals of GOD enzyme, resulting in a better immobilization. The sensor exhibits a glucose-dependent electrochemical potential against an Ag/AgCl reference microelectrode which is linear across the whole concentration range of interest (10 - 1000 mu M). Glucose concentration in human fat cell measured by our graphene-based sensor is in good agreement with nuclear magnetic resonance (NMR) spectroscopy.

  • 22.
    Ewest, D.
    et al.
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering. Siemens Ind Turbomachinery AB, Sweden.
    Almroth, P.
    Siemens Ind Turbomachinery AB, Sweden.
    Sjodin, B.
    Siemens Ind Turbomachinery AB, Sweden.
    Simonsson, Kjell
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Leidermark, Daniel
    Linköping University, Department of Management and Engineering, Solid Mechanics. Linköping University, Faculty of Science & Engineering.
    Moverare, Johan
    Linköping University, Department of Management and Engineering, Engineering Materials. Linköping University, Faculty of Science & Engineering.
    A modified compliance method for fatigue crack propagation applied on a single edge notch specimen2016In: International Journal of Fatigue, ISSN 0142-1123, E-ISSN 1879-3452, Vol. 92, 61-70 p.Article in journal (Refereed)
    Abstract [en]

    Crack length measurements with high accuracy are often difficult to achieve during fatigue crack propagation testing under non-isothermal conditions. In this work a modified approach to the compliance method defined in e.g. ASTM E647 is described, which is better suited for high loads, varying temperatures and for taking the scatter in Youngs modulus into account. A numerical finite element study is performed for a single edge notch specimen, to investigate the influence of initiation locations on the accuracy of the method. The change in cracked area versus change in stiffness for three different cases are numerically shown to collapse to one curve, i.e. the result is not significantly affected by how the crack is initiated. The numerical study is compared to results from two experiments using different materials, with heat tinting during the tests for extracting snapshots of the crack fronts. A good agreement between the experiments and the numerical study is shown. A new compliance curve and a new geometry function for the stress intensity factor is proposed for the single edge notch specimen. (C) 2016 Elsevier Ltd. All rights reserved.

  • 23.
    Mesgarzadeh, Behzad
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Esmaeil Zadeh, Iman
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A multi-segment clocking scheme to reduce on-chip EMI2011In: IEEE International SoC Conference (SoCC), Taipei, Taiwan: IEEE , 2011, 251-255 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents an EMI reduction technique for VLSI circuits in which a multi-segment clock is employed. It is proven that utilizing a clock signal with relaxed edge rate can suppress the harmonic tones at the output spectrum. However, it calls for higher short-circuit power dissipation in the clocked devices. Proposed multi-segment clock signal reduces the electromagnetic radiations while keeping the short circuit power dissipation in an acceptable level. Simulation results in 65-nm CMOS process are presented to prove the capability of such a clock network in EMI reduction.

  • 24.
    Wadströmer, Niclas
    et al.
    Swedish Defence Research Institute (FOI), Linköping, Sweden.
    Ahlberg, Jörgen
    Swedish Defence Research Institute (FOI), Linköping, Sweden.
    Svensson, Thomas
    Swedish Defence Research Institute (FOI), Linköping, Sweden.
    A new hyperspectral dataset and some challenges2010In: Proc. SPIE 7695, Algorithms and Technologies for Multispectral, Hyperspectral, and Ultraspectral Imagery XVI / [ed] Sylvia S. Shen; Paul E. Lewis, SPIE - International Society for Optical Engineering, 2010, Art.nr. 7695-22- p.Conference paper (Refereed)
    Abstract [en]

    We present a new hyperspectral data set that FOI will keep publicly available. The hyperspectral data set was collected in an airborne measurement over the countryside. The spectral resolution was about 10 nm which allowed registrations in 60 spectral bands in the visual and near infrared range (390-960 nm). Objects with various signature properties were placed in three areas: the edge of a wood, an open field and a rough open terrain. Several overflights were performed over the areas. Between the overflights some of the objects were moved, representing different scenarios. Our interest is primarily in anomaly detection of man-made objects placed in nature where no such objects are expected. The objects in the trial were military and civilian vehicles, boards of different size and a camouflage net. The size of the boards range from multipixel to subpixel size. Due to wind and cloud conditions the stability and the flight height of the airplane vary between the overflights, which makes the analysis extra challenging. 

  • 25.
    Karlsson, Magnus
    et al.
    n/a.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Kulesza, W.
    n/a.
    A non-overlapping two-phase clock generator with adjustable duty cycle2003In: Electronic Proc. Nat. Symp. on Microwave Technique and High Speed Electronics, GHz'03, 2003Conference paper (Other academic)
    Abstract [en]

    In this paper, a new robust non-overlapping two-phase clock generator with adjustable duty cycle is proposed. The generator is based on a differential negative edge trigged D flip-flop and has small area and power consumption. The maximal clock rate and delay are also improved reaching a clock frequency of 1.0 GHz in a standard 0.35 µm CMOS process. The new clock generator is inherently glitch and spike free and robust against slow clock transitions, that reduces the design effort significantly.

  • 26.
    Asratian , Amen S
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    A note on transformations of edge colorings of bipartite graphs2009In: JOURNAL OF COMBINATORIAL THEORY SERIES B, ISSN 0095-8956 , Vol. 99, no 5, 814-818 p.Article in journal (Refereed)
    Abstract [en]

    The author and A. Mirumian proved the following theorem: Let G be a bipartite graph with maximum degree Delta and let t, n be integers, t andgt;= n andgt;= Delta. Then it is possible to obtain, from one proper edge t-coloring of G, any proper edge n-coloring of G using only transformations of 2-colored and 3-colored subgraphs such that the intermediate colorings are also proper. In this note we show that if t andgt; Delta then we can transform f to g using only transformations of 2-colored subgraphs. We also correct the algorithm suggested in [A.S. Asratian, Short solution of Kotzigs problem for bipartite graphs, J. Combin. Theory Set. B 74 (1998) 160-168] for transformation of f to g in the case when t = n = Delta and G is regular.

  • 27.
    Gustafsson, Oscar
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Electronics System.
    Wanhammar, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Electrical Engineering, Electronics System.
    A novel approach to multiple constant multiplication using minimum spanning trees2002In: Midwest Symposium on Circuits and Systems,2002, Piscataway, NJ: IEEE , 2002, 652- p.Conference paper (Refereed)
    Abstract [en]

    In this work a novel approach to multiple constant multiplication based on minimum spanning trees is proposed. Each required coefficient is assigned to a vertex in a graph. The vertices are connected with weighted edges, where each edge weight corresponds to the number of adders required to derive one of the coefficient from the previous. The graph can be used to solve for the minimum spanning tree, which leads to a realization with a small number of adders. The optimal minimum spanning tree can be found in polynomial time. It is also possible to add extra constraints to the spanning tree, such as limited out-degree (corresponds to fan-out) and limited tree height (corresponds to delay). These problems are harder to solve, but there are good heuristics available. It is shown by simulation that the performance of the proposed algorithm is comparable with recently published algorithms.

  • 28.
    Klaastad, Øivind
    et al.
    Department of Anesthesiology, Rikshospitalet University Hospital, Oslo, Norway.
    Smith, Hans-Jørgen
    Department of Radiology, Rikshospitalet University Hospital, Oslo, Norway.
    Smedby, Örjan
    Linköping University, Faculty of Health Sciences. Linköping University, Department of Medical and Health Sciences, Radiology. Östergötlands Läns Landsting, Centre for Medical Imaging, Department of Radiology in Linköping. Linköping University, Center for Medical Image Science and Visualization (CMIV).
    Winther-Larssen, Eldrid H.
    Department of Radiology, Rikshospitalet University Hospital, Oslo, Norway.
    Brodal, Per
    Department of Anatomy, University of Oslo, Oslo, Norway.
    Breivik, Harald
    Department of Anesthesiology, Rikshospitalet University Hospital, Oslo, Norway.
    Fosse, Erik T.
    The Interventional Centre, Rikshospitalet University Hospital, Oslo, Norway.
    A novel infraclavicular brachial plexus block: The lateral and sagittal technique, developed by magnetic resonance imaging studies2004In: Anesthesia and Analgesia, ISSN 0003-2999, E-ISSN 1526-7598, Vol. 98, no 1, 252-256 p.Article in journal (Refereed)
    Abstract [en]

    A new infraclavicular brachial plexus block method has the patient supine with an adducted arm. The target is any of the three cords behind the pectoralis minor muscle. The point of needle insertion is the intersection between the clavicle and the coracoid process. The needle is advanced 0degrees-30degrees posterior, always strictly in the sagittal plane next to the coracoid process while abutting the antero-inferior edge of the clavicle. We tested the new method using magnetic resonance imaging (MRI) in 20 adult volunteers, without inserting a needle. Combining 2 simulated needle directions by 15degrees posterior and 0degrees in the images of the volunteers, at least one cord in 19 of 20 volunteers was contacted. This occurred within a needle depth of 6.5 cm. In the sagittal plane of the method the shortest depth to the pleura among all volunteers was 7.5 cm. The MRI study indicates that the new infraclavicular technique may be efficient in reaching a cord of the brachial plexus, often not demanding more than two needle directions. The risk of pneumothorax should be minimal because the needle is inserted no deeper than 6.5 cm. However, this needs to be confirmed by a clinical study.

  • 29.
    Fahleson, Tobias
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering.
    Ågren, Hans
    KTH Royal Institute Technology, Sweden.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Theoretical Chemistry. Linköping University, Faculty of Science & Engineering. KTH Royal Institute Technology, Sweden.
    A Polarization Propagator for Nonlinear X-ray Spectroscopies2016In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 7, no 11, 1991-1995 p.Article in journal (Refereed)
    Abstract [en]

    A complex polarization propagator approach has been developed to third order and implemented in density functional theory (DFT), allowing for the direct calculation of nonlinear molecular properties in the X-ray wavelength regime without explicitly addressing the excited-state manifold. We demonstrate the utility of this propagator method for the modeling of coherent near-edge X-ray two-photon absorption using, as an example, DFT as the underlying electronic structure model. Results are compared with the corresponding near edge X-ray absorption fine structure spectra, illuminating the differences in the role of symmetry, localization, and correlation between the two spectroscopies. The ramifications of this new technique for nonlinear X-ray research are briefly discussed.

  • 30.
    Felsberg, Michael
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Kruger, Norbert
    n/a.
    A Probabilistic Definition of Intrinsic Dimensionality for Images2003Report (Other academic)
    Abstract [en]

    In this paper we address the problem of appropriately representing the intrinsic dimensionality of image neighborhoods. This dimensionality describes the degrees of freedom of a local image patch and it gives rise to some of the most often applied corner and edge detectors. It is common to categorize the intrinsic dimensionality (iD) to three distinct cases: i0D, i1D, and i2D. Real images however contain combinations of all three dimensionalities which has to be taken into account by a continuous representation. Based on considerations of the structure tensor, we derive a cone-shaped iD-space which leads to a probabilistic point of view to the estimation of intrinsic dimensionality.

  • 31.
    Felsberg, Michael
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision . Linköping University, The Institute of Technology.
    Kruger, Norbert
    n/a.
    A Probabilistic Definition of Intrinsic Dimensionality for Images2003In: 25. DAGM Symposium Mustererkennung, Magdeburg eds Michaelis, B. and Krell, G., 2003, Vol. 2781, 140-147 p.Conference paper (Refereed)
    Abstract [en]

    In this paper we address the problem of appropriately representing the intrinsic dimensionality of image neighborhoods. This dimensionality describes the degrees of freedom of a local image patch and it gives rise to some of the most often applied corner and edge detectors. It is common to categorize the intrinsic dimensionality (iD) to three distinct cases: i0D, i1D, and i2D. Real images however contain combinations of all three dimensionalities which has to be taken into account by a continuous representation. Based on considerations of the structure tensor, we derive a cone-shaped iD-space which leads to a probabilistic point of view to the estimation of intrinsic dimensionality.

  • 32.
    Ojani, Amin
    et al.
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Mesgarzadeh, Behzad
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    Alvandpour, Atila
    Linköping University, Department of Electrical Engineering, Electronic Devices. Linköping University, The Institute of Technology.
    A quadrature UWB frequency synthesizer with dynamic settling-time calibration2013In: IEEE International Symposium on Circuits and Systems (ISCAS), 2013, IEEE , 2013, 2480-2483 p.Conference paper (Refereed)
    Abstract [en]

    This paper presents a quadrature DLL-based architecture for WiMedia ultra-wideband (UWB) frequency synthesis. I and Q carriers are directly generated by combining the quadrature multi-phase outputs of the DLL, using separate edge combiners (EC). A variable-stage voltage-controlled delay line (VCDL) scheme is proposed to provide the corresponding output phases to each EC, without the need for multiplexing the DLL outputs for different bands. Moreover, to prevent possible synthesizer hopping time degradation due to dynamic variations in temperature and voltage, a monitoring mechanism is employed to measure the time error at the instant of band switching, and compensate for it if it is beyond a limited value. The Synthesizer is implemented in a standard 65-nm CMOS technology and the simulation results indicate a hopping time of 4.5 to 8.8 ns across process corners. Simulated phase noise at 1 MHz offset from 4488 MHz carrier is -115 dBc/Hz and the worst case spur suppression is -31 dBc. The synthesizer consumes 13.9 mA from a 1.2-V supply.

  • 33.
    El Ouali, Mourad
    et al.
    University of Kiel, Germany.
    Fohlin, Helena
    Linköping University, Department of Clinical and Experimental Medicine, Division of Clinical Sciences. Linköping University, Faculty of Health Sciences. Östergötlands Läns Landsting, Center for Health and Developmental Care, Regional Cancer Center South East Sweden.
    Srivastav, Anand
    University of Kiel, Germany.
    A randomised approximation algorithm for the hitting set problem2014In: Theoretical Computer Science, ISSN 0304-3975, Vol. 555, 23-34 p.Article in journal (Refereed)
    Abstract [en]

    Let H = (V, epsilon) be a hypergraph with vertex set V and edge set epsilon, where n := vertical bar V vertical bar and m := vertical bar epsilon vertical bar. Let l be the maximum size of an edge and Delta be the maximum vertex degree. A hitting set (or vertex cover) in H is a subset of V in which all edges are incident. The hitting set problem is to find a hitting set of minimum cardinality. It is known that an approximation ratio of l can be achieved easily. On the other hand, for constant l, an approximation ratio better than l cannot be achieved in polynomial time under the unique games conjecture (Khot and Regev, 2008 [17]). Thus breaking the l-barrier for significant classes of hypergraphs is a complexity-theoretically and algorithmically interesting problem, which has been studied by several authors (Krivelevich, 1997 [18], Halperin, 2000 [12], Okun, 2005 [23]). We propose a randomised algorithm of hybrid type for the hitting set problem, which combines LP-based randomised rounding, graphs sparsening and greedy repairing and analyse it for different classes of hypergraphs. For hypergraphs with Delta = O(n1/4) and l = O (root n) we achieve an approximation ratio of l(1 - c/Delta), for some constant c greater than 0, with constant probability. For the case of hypergraphs where l and Delta are constants, we prove a ratio of l(1 - l-1/8 Delta). The latter is done by analysing the expected size of the hitting set and using concentration inequalities. Moreover, for quasi-regularisable hypergraphs, we achieve an approximation ratio of l(1 - n/8m). We show how and when our results improve over the results of Krivelevich, Halperin and Okun.

  • 34.
    Gill, Jonna
    et al.
    Linköping University, Department of Mathematics, Applied Mathematics. Linköping University, The Institute of Technology.
    Linusson, Svante
    Royal Institute of Technology, Stockholm.
    Moulton, Vincent
    University of East Anglia.
    Steel, Mike
    University of Canterbury.
    A regular decomposition of the edge-product space of phylogenetic trees2008In: Advances in Applied Mathematics, ISSN 0196-8858, Vol. 14, no 2, 158-176 p.Article in journal (Refereed)
    Abstract [en]

    We investigate the topology and combinatorics of a topological space called the edge-product space that is generated by the set of edge-weighted finite labelled trees. This space arises by multiplying the weights of edges on paths in trees, and is closely connected to tree-indexed Markov processes in molecular evolutionary biology. In particular, by considering combinatorial properties of the Tuffley poset of labelled forests, we show that the edge-product space has a regular cell decomposition with face poset equal to the Tuffley poset.

  • 35.
    Henningsson, Mathias
    et al.
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    Holmberg, Kaj
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    Rönnqvist, Mikael
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    Värbrand, Peter
    Linköping University, Department of Science and Technology. Linköping University, The Institute of Technology.
    A ring network design problem solved by a ring generation and allocation approach2003Report (Other academic)
    Abstract [en]

    The development of optical fibers in telecommunications has lead large changes in the field. When design a telecommunication network, capacity nowadays is cheap, and the minimal cost design tends to be a tree. Since such a design is very vulnerable for link or node failures, one often wish to include some kind of survivability requirement, for example that the network should be two-edge-connected or two-node-connected. Another form of design model is to prescribe that the network should be composed of connected rings of links. The network design problem is then to choose links from a give network, and compose them into a number of rings. Furthermore, the rings should be connected at certain transit nodes. Each possible ring is associated with a certain fixed cost, and all links in a certain ring are given the same capacity. Traffic between rings may pass through other rings, which is an important element of the problem. Finally, reserve capacity allocation according to certain principles is included. We describe the problem, modeled as a linear integer programming problem, and discuss different formulations and different solution methods. As the problem is quite difficult, we focus on heuristic solution methods, including elements of column generation and Lagrangean relaxation.

  • 36.
    Ahrén, Maria
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Selegård, Linnéa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    Söderlind, Fredrik
    Linköping University, Department of Physics, Chemistry and Biology, Nanostructured Materials. Linköping University, The Institute of Technology.
    Linares, Mathieu
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Kauczor, Joanna
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Norman, Patrick
    Linköping University, Department of Physics, Chemistry and Biology, Computational Physics. Linköping University, The Institute of Technology.
    Käll, Per-Olov
    Linköping University, Department of Physics, Chemistry and Biology, Physical Chemistry. Linköping University, The Institute of Technology.
    Uvdal, Kajsa
    Linköping University, Department of Physics, Chemistry and Biology, Molecular Surface Physics and Nano Science. Linköping University, Faculty of Science & Engineering.
    A simple polyol-free synthesis route to Gd2O3 nanoparticles for MRI applications: an experimental and theoretical study2012In: Journal of nanoparticle research, ISSN 1388-0764, E-ISSN 1572-896X, Vol. 14, no 8Article in journal (Refereed)
    Abstract [en]

    Chelated gadolinium ions, e. g., GdDTPA, are today used clinically as contrast agents for magnetic resonance imaging (MRI). An attractive alternative contrast agent is composed of gadolinium oxide nanoparticles as they have shown to provide enhanced contrast and, in principle, more straightforward molecular capping possibilities. In this study, we report a new, simple, and polyol-free way of synthesizing 4-5-nm-sized Gd2O3 nanoparticles at room temperature, with high stability and water solubility. The nanoparticles induce high-proton relaxivity compared to Gd-DTPA showing r(1) and r(2) values almost as high as those for free Gd3+ ions in water. The Gd2O3 nanoparticles are capped with acetate and carbonate groups, as shown with infrared spectroscopy, near-edge X-ray absorption spectroscopy, X-ray photoelectron spectroscopy and combined thermogravimetric and mass spectroscopy analysis. Interpretation of infrared spectroscopy data is corroborated by extensive quantum chemical calculations. This nanomaterial is easily prepared and has promising properties to function as a core in a future contrast agent for MRI.

  • 37.
    Westerlund, Andreas
    et al.
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    Göthe-Lundgren, Maud
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    Larsson, Torbjörn
    Linköping University, Department of Mathematics. Linköping University, The Institute of Technology.
    A stabilized column generation scheme for the traveling salesman subtour problem2006In: Discrete Applied Mathematics, ISSN 0166-218X, Vol. 154, no 15, 2212-2238 p.Article in journal (Refereed)
    Abstract [en]

    Given an undirected graph with edge costs and both revenues and weights on the vertices, the traveling salesman subtour problem is to find a subtour that includes a depot vertex, satisfies a knapsack constraint on the vertex weights, and that minimizes edge costs minus vertex revenues along the subtour.

    We propose a decomposition scheme for this problem. It is inspired by the classic side-constrained 1-tree formulation of the traveling salesman problem, and uses stabilized column generation for the solution of the linear programming relaxation. Further, this decomposition procedure is combined with the addition of variable upper bound (VUB) constraints, which improves the linear programming bound. Furthermore, we present a heuristic procedure for finding feasible subtours from solutions to the column generation problems. An extensive experimental analysis of the behavior of the computational scheme is presented.

  • 38.
    Vesterbacka, Mark
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    A static CMOS master-slave flip-flop experiment2000In: Proc. 7th IEEE Int. Conf. on Electronics, Circuits and Systems, ICECS'00, IEEE , 2000, 870-873 vol.2 p.Conference paper (Refereed)
    Abstract [en]

    A variant of a classical master-slave flip-flop based on transmission gates is derived where the transmission gates are replaced by static CMOS gates. The transmission gate flip-flop and the variant are evaluated along with one flip-flop based on C2MOS latches and another based on SR latches. All flip-flops are edge-triggered. The propagation delay, set-up time, and hold time are estimated using a 0.35 μm process. The author also investigates how the power dissipation at the maximal clock frequency varies when the supply voltage is scaled, both when the device geometry is kept constant and when it is scaled to yield good noise margins. In comparison, the variant on master-slave flip-flop has short propagation delay, but is only average in terms of throughput and power consumption. The flip-flop realized with C2 MOS latches seems to be a better candidate for a general-purpose implementation when voltage scaling is an option

  • 39.
    Sonntag, Dag
    Linköping University, Department of Computer and Information Science, Database and information techniques. Linköping University, The Institute of Technology.
    A Study of Chain Graph Interpretations2014Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Probabilistic graphical models are today one of the most well used architectures for modelling and reasoning about knowledge with uncertainty. The most widely used subclass of these models is Bayesian networks that has found a wide range of applications both in industry and research. Bayesian networks do however have a major limitation which is that only asymmetric relationships, namely cause and eect relationships, can be modelled between its variables. A class of probabilistic graphical models that has tried to solve this shortcoming is chain graphs. It is achieved by including two types of edges in the models, representing both symmetric and asymmetric relationships between the connected variables. This allows for a wider range of independence models to be modelled. Depending on how the second edge is interpreted this has also given rise to dierent chain graph interpretations.

    Although chain graphs were first presented in the late eighties the field has been relatively dormant and most research has been focused on Bayesian networks. This was until recently when chain graphs got renewed interest. The research on chain graphs has thereafter extended many of the ideas from Bayesian networks and in this thesis we study what this new surge of research has been focused on and what results have been achieved. Moreover we do also discuss what areas that we think are most important to focus on in further research.

    List of papers
    1. Chain Graphs and Gene Networks
    Open this publication in new window or tab >>Chain Graphs and Gene Networks
    2015 (English)In: Foundations of Biomedical Knowledge Representation: Methods and Applications / [ed] Arjen Hommersom and Peter J.F. Lucas, Springer, 2015, 159-178 p.Chapter in book (Refereed)
    Abstract [en]

    Chain graphs are graphs with possibly directed and undirected edges, and no semidirected cycle. They have been extensively studied as a formalism to represent probabilistic independence models, because they can model symmetric and asymmetric relationships between random variables. This allows chain graphs to represent a wider range of systems than Bayesian networks. This in turn allows for a more correct representation of systems that may contain both causal and non-causal relationships between its variables, like for example biological systems. In this chapter we give an overview of how to use chain graphs and what research exists on them today. We also give examples on how chain graphs can be used to model advanced systems, that are not well understood, such as gene networks.

    Place, publisher, year, edition, pages
    Springer, 2015
    Series
    Lecture Notes in Artificial Intelligence, ISSN 0302-9743 ; 9521
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105813 (URN)10.1007/978-3-319-28007-3_10 (DOI)978-3-319-28006-6 (ISBN)978-3-319-28007-3 (ISBN)
    Note

    The previous status of this article was Manuscript.

    Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2016-03-29Bibliographically approved
    2. Chain Graph Interpretations and Their Relations, Extended Version
    Open this publication in new window or tab >>Chain Graph Interpretations and Their Relations, Extended Version
    2013 (English)In: Proceedings of the 12th European Conference, ECSQARU 2013, Utrecht, The Netherlands, July 8-10, 2013 / [ed] Linda C. van der Gaag, Springer Berlin/Heidelberg, 2013, 510-521 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper deals with different chain graph interpretations and the relations between them in terms of representable independence models. Specifically, we study the Lauritzen-Wermuth-Frydenberg, Andersson-Madigan-Perlman and multivariate regression interpretations and present the necessary and sufficient conditions for when a chain graph of one interpretation can be perfectly translated into a chain graph of another interpretation. Moreover, we also present a feasible split for the Andersson-Madigan-Perlman interpretation with similar features as the feasible splits presented for the other two interpretations.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2013
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743 (print), 1611-3349 (online) ; Vol. 7958
    Keyword
    Chain Graphs, Lauritzen-Wermuth-Frydenberg interpretation, Andersson-Madigan-Perlman interpretation, multivariate regression interpretation
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-105814 (URN)10.1007/978-3-642-39091-3_43 (DOI)978-3-642-39090-6 (ISBN)978-3-642-39091-3 (ISBN)
    Conference
    The 12th European Conference on Symbolic and Quantitative Approaches to Reasoning with Uncertainty July 7th -10th, Utrecht, The Netherlands
    Note

    Awarded best student paper award at ECSQARU 2013.

    Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2015-05-28Bibliographically approved
    3. Approximate Counting of Graphical Models Via MCMC Revisited
    Open this publication in new window or tab >>Approximate Counting of Graphical Models Via MCMC Revisited
    2015 (English)In: International Journal of Intelligent Systems, ISSN 0884-8173, E-ISSN 1098-111X, Vol. 30, no 3, 384-420 p.Article in journal (Refereed) Published
    Abstract [en]

    We apply MCMC sampling to approximately calculate some quantities, and discuss their implications for learning directed and acyclic graphs (DAGs) from data. Specifically, we calculate the approximate ratio of essential graphs (EGs) to DAGs for up to 31 nodes. Our ratios suggest that the average Markov equivalence class is small. We show that a large majority of the classes seem to have a size that is close to the average size. This suggests that one should not expect more than a moderate gain in efficiency when searching the space of EGs instead of the space of DAGs. We also calculate the approximate ratio of connected EGs to connected DAGs, of connected EGs to EGs, and of connected DAGs to DAGs. These new ratios are interesting because, as we will see, they suggest that some conjectures that appear in the literature do not hold. Furthermore, we prove that the latter ratio is asymptotically 1.

    Finally, we calculate the approximate ratio of EGs to largest chain graphs for up to 25 nodes. Our ratios suggest that Lauritzen-Wermuth-Frydenberg chain graphs are considerably more expressive than DAGs. We also report similar approximate ratios and conclusions for multivariate regression chain graphs.

    Place, publisher, year, edition, pages
    Wiley-Blackwell, 2015
    Keyword
    MCMC sampling, Bayesian networks, Chain graphs, Lauritzen-Wermuth-Frydenberg interpretation, Multivariate regression interpretation
    National Category
    Computer and Information Science
    Identifiers
    urn:nbn:se:liu:diva-105815 (URN)10.1002/int.21704 (DOI)000348308600008 ()
    Note

    This work is funded by the Center for Industrial Information Technology (CENIIT) and a so-called career contract at Linkoping University, by the Swedish Research Council (ref. 2010-4808), and by FEDER funds and the Spanish Government (MICINN) through the projects TIN2010-20900-C04-03 and TIN2010-20900-C04-01.

    Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2016-03-29Bibliographically approved
    4. Learning Multivariate Regression Chain Graphs under Faithfulness
    Open this publication in new window or tab >>Learning Multivariate Regression Chain Graphs under Faithfulness
    2012 (English)In: Proceedings of the 6th European Workshop on Probabilistic Graphical Models, Granada (Spain), 19-21 September, 2012 / [ed] Andrés Cano, Manuel Gémez.-Olmedo and Thomas D. Nielsen, 2012, 299-306 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    This paper deals with multivariate regression chain graphs, which were introduced by Cox and Wermuth (1993, 1996) to represent linear causal models with correlated errors. Specifically, we present a constraint based algorithm for learning a chain graph a given probability distribution is faithful to. We also show that for each Markov equivalence class of multivariate regression chain graphs there exists a set of chain graphs with a unique minimal set of lines. Finally, we show that this set of lines can be identified from any member of the class by repeatedly splitting its connectivity components according to certain conditions.

    Keyword
    Chain Graph, Multivariate Regression Chain Graph, Learning, Bidirected Graph
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-80306 (URN)978-84-15536-57-4 (ISBN)
    Conference
    Sixth European Workshop on Probabilistic Graphical Models (PGM 2012), 19-21 September 2012, Granada, Spain
    Available from: 2012-08-23 Created: 2012-08-23 Last updated: 2016-07-01Bibliographically approved
    5. An inclusion optimal algorithm for chain graph structure learning: with supplement
    Open this publication in new window or tab >>An inclusion optimal algorithm for chain graph structure learning: with supplement
    2014 (English)In: Proceedings of the 17th International Conference on Arti-cial Intelligence and Statistics, 2014, 778-786 p.Conference paper, Published paper (Other academic)
    Abstract [en]

    This paper presents and proves an extension of Meek’s conjecture to chain graphs under the Lauritzen-Wermuth-Frydenberg interpretation. The proof of the conjecture leads to the development of a structure learning algorithm that finds an inclusion optimal chain graph for any given probability distribution satisfying the composition property. Finally, the new algorithm is experimentally evaluated.

    Series
    JMLR Workshop and Conference Proceedings, Vol. 33
    Keyword
    Chain Graph, Lauritzen-Wermuth-Frydenberg interpretation, Learning
    National Category
    Computer Systems
    Identifiers
    urn:nbn:se:liu:diva-105816 (URN)
    Conference
    17th International Conference on Artificial Intelligence and Statistics April 22-25, 2014, Reykjavik, Iceland
    Available from: 2014-04-08 Created: 2014-04-08 Last updated: 2016-03-29Bibliographically approved
  • 40. Birgerson, J.
    et al.
    Keil, M.
    Luo, Y.
    Theoretical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
    Svensson, S.
    Department of Physics, Uppsala University, S-751 21 Uppsala, Sweden.
    Agren, H.
    Ågren, H., Theoretical Chemistry, Royal Institute of Technology, S-100 44 Stockholm, Sweden.
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    A study of the electronic structure of ethylenedioxythiophene in gas phase using NEXAFS and quantum chemical calculations2004In: Chemical Physics Letters, ISSN 0009-2614, Vol. 392, no 1-3, 100-104 p.Article in journal (Refereed)
    Abstract [en]

    Near-edge X-ray absorption fine structure spectroscopy spectra of ethylenedioxythiophene has been recorded in gas phase at the carbon K-edge, sulphur L-edge and oxygen, K-edge. The experimental data has been interpreted with the help of a modified density functional code deMon. The good agreement between the calculated spectra and the measured one allows us to assign all observed resonances. The existence of p* resonances in both the measured and the calculated OK-edge adsorption spectrum demonstrate that the delocalized p-system of the thiophene part of the molecule is extended up to the oxygen atoms of the molecule. © 2004 Elsevier B.V. All rights reserved.

  • 41.
    Liu, Yang
    et al.
    Faculty of Technology, University of Vaasa, Vaasa, Finland.
    Jantti, Riku
    Faculty of Technology, University of Vaasa, Vaasa, Finland.
    A Study Towards Enhanced Reliability Performance of Remote Control and Monitoring Application Over Commercial Wireless Communication Networks2006In: 2006 International Conference on Wireless Communications, Networking and Mobile Computing, Institute of Electrical and Electronics Engineers (IEEE), 2006, 1-4 p.Conference paper (Refereed)
    Abstract [en]

    Remote control and monitoring systems provide many useful operating advantages in industrial automation and demand highly reliable and secure communication means. Their widespread use is, however, limited because of the high cost of current communications in use making them economically infeasible. Hence, there is a need to develop new low cost communication and control concepts by making such solutions economically feasible. In this paper, we present a scheme for implementing reliable wireless communication links for application of remote control and monitoring system based on current available commercial wireless communication networks, e.g. GPRS/EDGE/UMTS. The reliability enhancement over wireless networks has been proposed and its performance has been studied. This paper examines the proposed solution by means of both analytical and numerical evaluation, and has shown that the demanded reliability performance can be met by using only commercial wireless communication networks.

  • 42.
    Asratian, Armen
    et al.
    Linköping University, The Institute of Technology. Linköping University, Department of Mathematics, Applied Mathematics.
    Casselgren, Carl Johan
    A sufficient condition for interval edge colorings of (4,3)-biregular bipartite graphs2006Report (Other academic)
  • 43.
    Westin, Carl-Fredrik
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    A Tensor Framework for Multidimensional Signal Processing1994Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis deals with ltering of multidimensional signals. A large part of the thesis is devoted to a novel filtering method termed "Normalized convolution". The method performs local expansion of a signal in a chosen lter basis which not necessarily has to be orthonormal. A key feature of the method is that it can deal with uncertain data when additional certainty statements are available for the data and/or the lters. It is shown how false operator responses due to missing or uncertain data can be significantly reduced or eliminated using this technique. Perhaps the most well-known of such eects are the various 'edge effects' which invariably occur at the edges of the input data set. The method is an example of the signal/certainty - philosophy, i.e. the separation of both data and operator into a signal part and a certainty part. An estimate of the certainty must accompany the data. Missing data are simply handled by setting the certainty to zero. Localization or windowing of operators is done using an applicability function, the operator equivalent to certainty, not by changing the actual operator coefficients. Spatially or temporally limited operators are handled by setting the applicability function to zero outside the window.

    The use of tensors in estimation of local structure and orientation using spatiotemporal quadrature filters is reviewed and related to dual tensor bases. The tensor representation conveys the degree and type of local anisotropy. For image sequences, the shape of the tensors describe the local structure of the spatiotemporal neighbourhood and provides information about local velocity. The tensor representation also conveys information for deciding if true flow or only normal flow is present. It is shown how normal flow estimates can be combined into a true flow using averaging of this tensor eld description.

    Important aspects of representation and techniques for grouping local orientation estimates into global line information are discussed. The uniformity of some standard parameter spaces for line segmentation is investigated. The analysis shows that, to avoid discontinuities, great care should be taken when choosing the parameter space for a particular problem. A new parameter mapping well suited for line extraction, the Möbius strip parameterization, is de ned. The method has similarities to the Hough Transform.

    Estimation of local frequency and bandwidth is also discussed. Local frequency is an important concept which provides an indication of the appropriate range of scales for subsequent analysis. One-dimensional and two-dimensional examples of local frequency estimation are given. The local bandwidth estimate is used for dening a certainty measure. The certainty measure enables the use of a normalized averaging process increasing robustness and accuracy of the frequency statements.

  • 44.
    Luo, Y.
    et al.
    Theoretical Chemistry, Roy. Inst. of Technology, S-10044, Stockholm, Sweden.
    Agren, H.
    Ågren, H., Theoretical Chemistry, Roy. Inst. of Technology, S-10044, Stockholm, Sweden.
    Keil, M.
    Friedlein, Rainer
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    Salaneck, William R
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Surface Physics and Chemistry .
    A theoretical investigation of the near-edge X-ray absorption spectrum of hexa- peri -hexabenzocoronene2001In: Chemical Physics Letters, ISSN 0009-2614, Vol. 337, no 1-3, 176-180 p.Article in journal (Refereed)
    Abstract [en]

    The near-edge X-ray absorption spectrum of hexa-peri-hexabenzocoronene has been simulated by density functional theory techniques using transition state and full core hole potentials. The total spectrum is found to be a composition of multiple structure in the subspectra of the symmetry unique carbons, rather than by chemically shifted single p* transitions. This quite 'fullerene-like' behavior, with only minor reminiscence of either graphite or benzene spectral features, is used to argue that long-range effects must be important to build up the dominating single excitonic p* feature in graphite. © 2001 Elsevier Science B.V.

  • 45.
    Åström, Freddie
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Center for Medical Image Science and Visualization, CMIV. Linköping University, The Institute of Technology.
    A Variational Approach to Image Diffusion in Non-Linear Domains2013Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Image filtering methods are designed to enhance noisy images captured in situations that are problematic for the camera sensor. Such noisy images originate from unfavourable illumination conditions, camera motion, or the desire to use only a low dose of ionising radiation in medical imaging. Therefore, in this thesis work I have investigated the theory of partial differential equations (PDE) to design filtering methods that attempt to remove noise from images. This is achieved by modeling and deriving energy functionals which in turn are minimized to attain a state of minimum energy. This state is obtained by solving the so called Euler-Lagrange equation. An important theoretical contribution of this work is that conditions are put forward determining when a PDE has a corresponding energy functional. This is in particular described in the case of the structure tensor, a commonly used tensor in computer vision.A primary component of this thesis work is to model adaptive image filtering such that any modification of the image is structure preserving, but yet is noise suppressing. In color image filtering this is a particular challenge since artifacts may be introduced at color discontinuities. For this purpose a non-Euclidian color opponent transformation has been analysed and used to separate the standard RGB color space into uncorrelated components.A common approach to achieve adaptive image filtering is to select an edge stopping function from a set of functions that have proven to work well in the past. The purpose of the edge stopping function is to inhibit smoothing of image features that are desired to be retained, such as lines, edges or other application dependent characteristics. Thus, a step from ad-hoc filtering based on experience towards an application-driven filtering is taken, such that only desired image features are processed. This improves what is characterised as visually relevant features, a topic which this thesis covers, in particular for medical imaging.The notion of what are relevant features is a subjective measure may be different from a layman's opinion compared to a professional's. Therefore, we advocate that any image filtering method should yield an improvement not only in numerical measures but also a visual improvement should be experienced by the respective end-user

    List of papers
    1. Color Persistent Anisotropic Diffusion of Images
    Open this publication in new window or tab >>Color Persistent Anisotropic Diffusion of Images
    2011 (English)In: Image Analysis / [ed] Anders Heyden, Fredrik Kahl, Heidelberg: Springer, 2011, 262-272 p.Conference paper, Published paper (Refereed)
    Abstract [en]

    Techniques from the theory of partial differential equations are often used to design filter methods that are locally adapted to the image structure. These techniques are usually used in the investigation of gray-value images. The extension to color images is non-trivial, where the choice of an appropriate color space is crucial. The RGB color space is often used although it is known that the space of human color perception is best described in terms of non-euclidean geometry, which is fundamentally different from the structure of the RGB space. Instead of the standard RGB space, we use a simple color transformation based on the theory of finite groups. It is shown that this transformation reduces the color artifacts originating from the diffusion processes on RGB images. The developed algorithm is evaluated on a set of real-world images, and it is shown that our approach exhibits fewer color artifacts compared to state-of-the-art techniques. Also, our approach preserves details in the image for a larger number of iterations.

    Place, publisher, year, edition, pages
    Heidelberg: Springer, 2011
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743 (print), 1611-3349 (online) ; 6688
    Keyword
    Non-linear diffusion, color image processing, perceptual image quality
    National Category
    Information Science Computer Vision and Robotics (Autonomous Systems)
    Identifiers
    urn:nbn:se:liu:diva-68999 (URN)10.1007/978-3-642-21227-7_25 (DOI)978-3-642-21226-0 (ISBN)978-3-642-21227-7 (ISBN)
    Conference
    The 17th Scandinavian Conference on Image Analysis, 23-27 May 2011, Ystad Sweden
    Note

    Original Publication: Åström Freddie, Felsberg Michael and Lenz Reiner, Color Persistent Anisotropic Diffusion of Images, 2011, Image Analysis, SCIA conference, 23-27 May 2011, Ystad Sweden, 262-272. http://dx.doi.org/10.1007/978-3-642-21227-7_25 Copyright: Springer

    Available from: 2011-06-17 Created: 2011-06-15 Last updated: 2016-08-31Bibliographically approved
    2. On Tensor-Based PDEs and their Corresponding Variational Formulations with Application to Color Image Denoising
    Open this publication in new window or tab >>On Tensor-Based PDEs and their Corresponding Variational Formulations with Application to Color Image Denoising
    2012 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    The case when a partial differential equation (PDE) can be considered as an Euler-Lagrange (E-L) equation of an energy functional, consisting of a data term and a smoothness term is investigated. We show the necessary conditions for a PDE to be the E-L equation for a corresponding functional. This energy functional is applied to a color image denoising problem and it is shown that the method compares favorably to current state-of-the-art color image denoising techniques.

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2012
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 7574
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-79603 (URN)10.1007/978-3-642-33712-3_16 (DOI)978-3-642-33711-6 (ISBN)978-3-642-33712-3 (ISBN)
    Conference
    ECCV 2012: 12th European Conference on Computer Vision, 7-12 October, Firenze, Italy
    Projects
    NACIPGARNICSELLIIT
    Available from: 2012-08-10 Created: 2012-08-10 Last updated: 2017-06-01Bibliographically approved
    3. Targeted Iterative Filtering
    Open this publication in new window or tab >>Targeted Iterative Filtering
    2013 (English)Conference paper, Published paper (Refereed)
    Abstract [en]

    The assessment of image denoising results depends on the respective application area, i.e. image compression, still-image acquisition, and medical images require entirely different behavior of the applied denoising method. In this paper we propose a novel, nonlinear diffusion scheme that is derived from a linear diffusion process in a value space determined by the application. We show that application-driven linear diffusion in the transformed space compares favorably with existing nonlinear diffusion techniques. 

    Place, publisher, year, edition, pages
    Springer Berlin/Heidelberg, 2013
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743 (print), 1611-3349 (online) ; 7893
    National Category
    Signal Processing
    Identifiers
    urn:nbn:se:liu:diva-89674 (URN)10.1007/978-3-642-38267-3_1 (DOI)978-3-642-38266-6 (ISBN)978-3-642-38267-3 (ISBN)
    Conference
    Fourth International Conference on Scale Space and Variational Methods in Computer Vision (SSVM 2013), 2-6 June 2013, Schloss Seggau, Graz region, Austria
    Projects
    VIDIGARNICSSM10-002BILDLAB
    Available from: 2013-04-03 Created: 2013-03-01 Last updated: 2016-05-04Bibliographically approved
  • 46.
    Chen, Lei
    et al.
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Yuan, Di
    Linköping University, Department of Science and Technology, Communications and Transport Systems. Linköping University, The Institute of Technology.
    Achieving higher HSDPA performance and preserving R99 soft handover control by large scale optimization in CPICH coverage planning2009In: Proceedings of IEEE Wireless Telecommunications Symposium (WTS) 2009, Piscataway, NJ, USA: IEEE , 2009, 39-44 p.Conference paper (Refereed)
    Abstract [en]

    Common Pilot Channel (CPICH) power is a crucial parameter in coverage planning of todays UMTS networks that implement both HSDPA and R99 services. Adopting a non-uniform allocation of cell CPICH power and minimizing its amount necessary for coverage, the resulting power saving significantly improves HSDPA performance. At the same time, it is vital to have the desired level R99 soft handover which is heavily influenced by CPICH. In this paper, we demonstrate how large scale optimization can deal with both tasks. Our approach focuses on enhancing cell-edge HSDPA data rate, subject to requirements of CPICH coverage and the level of R99 soft(-er) handover We present a solution algorithm that optimizes CPICH allocation for HSDPA performance, and, in parallel, offers accurate control of R99 soft handover Experimental results for large and realistic network planning scenarios demonstrate the benefit of our optimization approach.

  • 47.
    Felsberg, Michael
    Linköping University, Center for Medical Image Science and Visualization (CMIV). Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, The Institute of Technology.
    Adaptive Filtering using Channel Representations2012In: Mathematical Methods for Signal and Image Analysis and Representation / [ed] Luc Florack, Remco Duits, Geurt Jongbloed, Marie-Colette Lieshout, Laurie Davies, Springer London, 2012, 31-48 p.Chapter in book (Refereed)
    Abstract [en]

    This book presents a mathematical methodology for image analysis tasks at the edge of current research, including anisotropic diffusion filtering of tensor fields. Instead of specific applications, it explores methodological structures on which they are built.

  • 48.
    Cervin, Albert
    Linköping University, Department of Science and Technology, Media and Information Technology. Linköping University, The Institute of Technology.
    Adaptive Hardware-accelerated Terrain Tessellation2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In this master thesis report, a scheme for adaptive hardware terrain tessellation is presented. The scheme uses an offline processing approach where a height map is analyzed in terms of curvature and the result is stored in a resource called density map. This density map is then bound as a resource to the hardware tessellation stage and used to bias the tessellation factor for a given edge. The scheme is implemented inside FrostbiteTM2 by EATM DICETM and produces good results while making the heightfield rendering more efficient. The performance gain can be used to increase the rendering detail, allowing for better visual appearance for the terrain mesh. The scheme is currently implemented for hardware tessellation but could also be used for software terrain mesh generation. The implementation works satisfactory and produces good results with a reasonable speed.

  • 49.
    Münger, Peter
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics. Linköping University, The Institute of Technology.
    Chirita, Valeriu
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Hultman, Lars
    Linköping University, The Institute of Technology. Linköping University, Department of Physics, Chemistry and Biology, Thin Film Physics.
    Greene, J.E.
    Adatom/vacancy interactions and interlayer mass transport in small two-dimensional Pt clusters on Pt(1 1 1)2003In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 539, no 1-3Article in journal (Refereed)
    Abstract [en]

    We use embedded-atom molecular dynamics simulations to follow the dynamics of adatoms, vacancies, and adatom/vacancy pairs on two-dimensional hexagonal Pt19 clusters on Pt(1 1 1) surfaces at 1000 K. All configurations are found to be quite stable and have essentially the same migration mobilities as compact hexagonal clusters. However, the presence of a single vacancy dramatically decreases the lifetime of an adatom on the cluster by a factor of three. This occurs primarily through an enhancement of the rate of push-out/exchange reactions at the outer cluster edge resulting from vacancy-induced softening of edge atom bonds. Overall, adatoms in the presence of vacancies descend to the terrace via vacancy filling 10% of the time, and through reactions with outer cluster edges the remaining 90%. Direct vacancy filling mechanisms are analogous to, and have similar activation energies with, those at outer cluster edges: adatom hopping over descending steps and push-out/exchange reactions. © 2003 Elsevier B.V. All rights reserved.

  • 50.
    Tiwari, Ashutosh
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biosensors and Bioelectronics. Linköping University, The Institute of Technology.
    Valyukh, SergiyLinköping University, Department of Physics, Chemistry and Biology, Applied Optics . Linköping University, The Institute of Technology.
    Advanced Energy Materials2014Collection (editor) (Other academic)
    Abstract [en]

    An essential resource for scientists designing new energy materials for the vast landscape of solar energy conversion as well as materials processing and characterizatio.

    Based on the new and fundamental research on novel energy materials with tailor-made photonic properties, the role of materials engineering has been to provide much needed support in the development of photovoltaic devices. Advanced Energy Materials offers a unique, state-of-the-art look at the new world of novel energy materials science, shedding light on the subject's vast multi-disciplinary approach.

    The book focuses particularly on photovoltaics, efficient light sources, fuel cells, energy-saving technologies, energy storage technologies, nanostructured materials as well as innovating materials and techniques for future nanoscale electronics. Pathways to future development are also discussed.Critical, cutting-edge subjects are addressed, including:

    • Non-imaging focusing heliostat; state-of-the-art of nanostructures
    • Metal oxide semiconductors and their nanocomposites
    • Superionic solids; polymer nanocomposites; solid electrolytes; advanced electronics
    • Electronic and optical properties of lead sulfide
    • High-electron mobility transistors and light-emitting diodes
    • Anti-ferroelectric liquid crystals; PEEK membrane for fuel cells
    • Advanced phosphors for energy-efficient lighting
    • Molecular computation photovoltaics and photocatalysts
    • Photovoltaic device technology and non-conventional energy applicationsReadership

    The book is written for a large and broad readership including researchers and university graduate students from diverse backgrounds such as chemistry, materials science, physics, and engineering working in the fields of nanotechnology, photovoltaic device technology, and non-conventional energy.

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