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Forchheimer, Robert
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Publications (10 of 56) Show all publications
Setterqvist, E. & Forchheimer, R. (2018). Real-Time Communication Systems based on Taut Strings. Journal of Communications and Networks, 20(2), 207-218
Open this publication in new window or tab >>Real-Time Communication Systems based on Taut Strings
2018 (English)In: Journal of Communications and Networks, ISSN 1229-2370, E-ISSN 1976-5541, Vol. 20, no 2, p. 207-218Article in journal (Refereed) Published
Abstract [en]

We consider buffered real-time communication over channels with time-dependent capacities which are known in advance. The real-time constraint is imposed in terms of limited transmission time between sender and receiver. For a network consisting of a single channel it is shown that there is a coding rate strategy, geometrically characterized as a taut string, which minimizes the average distortion with respect to all convex distortionrate functions. Utilizing the taut string characterization further, an algorithm that computes the optimal coding rate strategy is provided. We then consider more general networks with several connected channels in parallel or series with intermediate buffers. It is shown that also for these networks there is a coding rate strategy, geometrically characterized as a taut string, which minimizes the average distortion with respect to all convex distortion-rate functions. The optimal offline strategy provides a benchmark for the evaluation of different coding rate strategies. Further, it guides us in the construction of a simple but rather efficient strategy for channels in the online setting which alternates between a good and a bad state.

Place, publisher, year, edition, pages
IEEE, 2018
Keywords
Buffers; distortion; real-time systems; source coding; taut string
National Category
Telecommunications
Identifiers
urn:nbn:se:liu:diva-148263 (URN)10.1109/JCN.2018.000027 (DOI)000432478900009 ()
Note

Funding Agencies|Research School in Interdisciplinary Mathematics at Linkoping University; Swedish Research Council [2014-6230]

Available from: 2018-06-04 Created: 2018-06-04 Last updated: 2018-06-21
Toss, H., Sani, N., Fabiano, S., Simon, D. T., Forchheimer, R. & Berggren, M. (2016). Polarization of ferroelectric films through electrolyte. Journal of Physics: Condensed Matter, 28(10), Article ID 105901.
Open this publication in new window or tab >>Polarization of ferroelectric films through electrolyte
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2016 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 28, no 10, article id 105901Article in journal (Refereed) Published
Abstract [en]

A simplified model is developed to understand the field and potential distribution through devices based on a ferroelectric film in direct contact with an electrolyte. Devices based on the ferroelectric polymer polyvinylidenefluoride-trifluoroethylene (PVDF-TrFE) were produced – in metalferroelectric-metal, metal-ferroelectric-dielectric-metal, and metal-ferroelectric-electrolyte-metal architectures – and used to test the model, and simulations based on the model and these fabricated devices were performed. From these simulations we find indication of progressive polarization of the films. Furthermore, the model implies that there is a relation between the separation of charge within the devices and the observed open circuit voltage. This relation is confirmed experimentally. The ability to polarize ferroelectric polymer films through aqueous electrolytes, combined with the strong correlation between the properties of the electrolyte double layer and the device potential, opens the door to a variety of new applications for ferroelectric technologies, e.g., regulation of cell culture growth and release, steering molecular self-assembly, or other large area applications requiring aqueous environments.

Place, publisher, year, edition, pages
Institute of Physics (IOP), 2016
National Category
Physical Sciences Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-121802 (URN)10.1088/0953-8984/28/10/105901 (DOI)000371007800015 ()
Note

Funding agencies:  Swedish Governmental Agency for Innovation Systems (VINNOVA) [2010-00507]; Knut and Alice Wallenberg Foundation; Advanced Functional Materials Center at Linkoping University; Onnesjo Foundation

Available from: 2015-10-07 Created: 2015-10-07 Last updated: 2017-12-01Bibliographically approved
Forchheimer, D., Forchheimer, R. & Haviland, D. B. (2015). Improving image contrast and material discrimination with nonlinear response in bimodal atomic force microscopy. Nature Communications, 6(6270)
Open this publication in new window or tab >>Improving image contrast and material discrimination with nonlinear response in bimodal atomic force microscopy
2015 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 6, no 6270Article in journal (Refereed) Published
Abstract [en]

Atomic force microscopy has recently been extented to bimodal operation, where increased image contrast is achieved through excitation and measurement of two cantilever eigen-modes. This enhanced material contrast is advantageous in analysis of complex heterogeneous materials with phase separation on the micro or nanometre scale. Here we show that much greater image contrast results from analysis of nonlinear response to the bimodal drive, at harmonics and mixing frequencies. The amplitude and phase of up to 17 frequencies are simultaneously measured in a single scan. Using a machine-learning algorithm we demonstrate almost threefold improvement in the ability to separate material components of a polymer blend when including this nonlinear response. Beyond the statistical analysis performed here, analysis of nonlinear response could be used to obtain quantitative material properties at high speeds and with enhanced resolution.

Place, publisher, year, edition, pages
Nature Publishing Group: Nature Communications, 2015
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-116841 (URN)10.1038/ncomms7270 (DOI)000350289500001 ()25665933 (PubMedID)
Note

Funding Agencies|Knut and Alice Wallenberg Foundation; Vetenskapsradet

Available from: 2015-04-07 Created: 2015-04-07 Last updated: 2017-12-04
Tu, D., Takimiya, K., Zschieschang, U., Klauk, H. & Forchheimer, R. (2015). Modeling of Drain Current Mismatch in OrganicThin-Film Transistors. IEEE/OSA Journal of Display Technology, 11, 559-563
Open this publication in new window or tab >>Modeling of Drain Current Mismatch in OrganicThin-Film Transistors
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2015 (English)In: IEEE/OSA Journal of Display Technology, ISSN 1551-319X, E-ISSN 1558-9323, Vol. 11, p. 559-563Article in journal (Refereed) Published
Abstract [en]

In this paper, we present a consistent model to analyzethe drain current mismatch of organic thin-film transistors.The model takes charge fluctuations and edge effects into account,to predict the fluctuations of drain currents. A Poisson distributionfor the number of charge carriers is assumed to represent therandom distribution of charge carriers in the channel. The edge effectsdue to geometric variations in fabrication processes are interpretedin terms of the fluctuations of channel length and width. Thesimulation results are corroborated by experimental results takenfrom over 80 organic transistors on a flexible plastic substrate.

Keywords
Current fluctuation, mismatch, modeling, organic thin-film transistors (OTFTs)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-127600 (URN)10.1109/JDT.2015.2419692 (DOI)000376179800010 ()
Projects
“ Silicon-Organic Hybrid Autarkic Systems (SiOS)” project
Funder
Swedish Foundation for Strategic Research
Available from: 2016-05-03 Created: 2016-05-03 Last updated: 2017-11-30Bibliographically approved
Muhammad, M., Zervas, G. & Forchheimer, R. (2015). Resource Allocation for Space-Division Multiplexing: Optical White Box Versus Optical Black Box Networking. Journal of Lightwave Technology, 33(23), 4928-4941
Open this publication in new window or tab >>Resource Allocation for Space-Division Multiplexing: Optical White Box Versus Optical Black Box Networking
2015 (English)In: Journal of Lightwave Technology, ISSN 0733-8724, E-ISSN 1558-2213, Vol. 33, no 23, p. 4928-4941Article in journal (Refereed) Published
Abstract [en]

Elastic optical networking (EON) with space-division multiplexing (SDM) is the only evident long-term solution to the capacity needs of the future networks. The introduction of space via spatial fibers, such as multicore fibers (MCF) to EON provides an additional dimension as well as challenges to the network planning and resource optimization problem. There are various types of technologies for SDM transmission medium, switching, and amplification; each of them induces different capabilities and constraints on the network. For example, employing MCF as the transmission medium for SDM mitigates the spectrum continuity constraint of the routing and spectrum allocation problem for EON. In fact, cores can be switched freely on different links during routing of the network traffic. On the other hand, intercore crosstalk should be taken into account while solving the resource allocation problem. In the framework of switching for elastic SDM network, the programmable architecture on demand (AoD) node (optical white box) can provide a more scalable solution with respect to the hard-wired reconfigurable optical add/drop multiplexers (ROADMs) (optical black box). This study looks into the routing, modulation, spectrum, and core allocation (RMSCA) problem for weakly-coupled MCF-based elastic SDM networks implemented through AoDs and static ROADMs. The proposed RMSCA strategies integrate the spectrum resource allocation, switching resource deployment, and physical layer impairment in terms of intercore crosstalk through a multiobjective cost function. The presented strategies perform a cross-layer optimization between the network and physical layers to compute the actual intercore crosstalk for the candidate resource solutions and are specifically tailored to fit the type of optical node deployed in the network. The aim of all these strategies is to jointly optimize the switching and spectrum resource efficiency when provisioning demands with diverse capacity requirements. Extensive simulation results demonstrate that 1) by exploiting the dense intranodal connectivity of the ROADM-based SDM network, resource efficiency and provisioned traffic volume improve significantly related to the AoD-based solution, 2) the intercore crosstalk aware strategies improve substantially the provisioned traffic volume for the AoD-based SDM network, and 3) the switching modules grows very gently for the network designed with AoD nodes related to the one with ROADMs as the traffic increases, qualifying AoD as a scalable and cost-efficient choice for future SDM networks.

Place, publisher, year, edition, pages
IEEE-INST ELECTRICAL ELECTRONICS ENGINEERS INC, 2015
Keywords
Architecture on demand; inter-core crosstalk; multi-core fiber; network planning; quasi-static traffic; space division multiplexing
National Category
Electrical Engineering, Electronic Engineering, Information Engineering
Identifiers
urn:nbn:se:liu:diva-123515 (URN)10.1109/JLT.2015.2493123 (DOI)000365228100001 ()
Note

Funding Agencies|Swedish Research Council [2014-6230]; EPSRC [EP/L027070/1 SONATAS]

Available from: 2015-12-22 Created: 2015-12-21 Last updated: 2017-12-01
Anders, Å. & Forchheimer, R. (2014). A High Speed 2D Time-to-Impact Algorithm Targeted for Smart Image Sensors. In: Proc. SPIE 9022, Image Sensors and Imaging Systems 2014: . Paper presented at Image Sensors and Imaging Systems, February 2, 2014, San Francisco, California, USA. International Society for Optical Engineering; 1999, 9022
Open this publication in new window or tab >>A High Speed 2D Time-to-Impact Algorithm Targeted for Smart Image Sensors
2014 (English)In: Proc. SPIE 9022, Image Sensors and Imaging Systems 2014, International Society for Optical Engineering; 1999 , 2014, Vol. 9022Conference paper, Published paper (Refereed)
Abstract [en]

In this paper we present a 2D extension of a previously described 1D method for a time-to-impact sensor [5][6]. As in the earlier paper, the approach is based on measuring time instead of the apparent motion of points in the image plane to obtain data similar to the optical flow. The specific properties of the motion field in the time-to-impact application are used, such as using simple feature points which are tracked from frame to frame. Compared to the 1D case, the features will be proportionally fewer which will affect the quality of the estimation. We give a proposal on how to solve this problem. Results obtained are as promising as those obtained from the 1D sensor.

Place, publisher, year, edition, pages
International Society for Optical Engineering; 1999, 2014
Series
Proceedings of SPIE, ISSN 0277-786X ; 9022
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-106701 (URN)10.1117/12.2037738 (DOI)000334024600023 ()
Conference
Image Sensors and Imaging Systems, February 2, 2014, San Francisco, California, USA
Available from: 2014-05-19 Created: 2014-05-19 Last updated: 2014-05-23
Ajmal, M., Furdek, M., Monti, P., Wosinska, L. & Forchheimer, R. (2014). An Optimization Model for Dynamic Bulk Provisioning in Elastic Optical Networks. In: Asia Communications and Photonics Conference 2014: . Paper presented at Asia Communications and Photonics Conference, November 11-14, Shanghai, China (pp. AF3E.6). Optics Info Base, Optical Society of America
Open this publication in new window or tab >>An Optimization Model for Dynamic Bulk Provisioning in Elastic Optical Networks
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2014 (English)In: Asia Communications and Photonics Conference 2014, Optics Info Base, Optical Society of America, 2014, p. AF3E.6-Conference paper, Published paper (Refereed)
Abstract [en]

We investigate benefits of setup-delay tolerance in elastic optical networks and propose an optimization model for dynamic and concurrent connection provisioning. Simulation shows that the proposed strategy offers significant improvement of the network blocking performance.

Place, publisher, year, edition, pages
Optics Info Base, Optical Society of America, 2014
Keywords
Fiber optics and optical communications; Networks, network optimization
National Category
Information Systems Computer Sciences
Identifiers
urn:nbn:se:liu:diva-115904 (URN)10.1364/ACPC.2014.AF3E.6 (DOI)2-s2.0-84918576254 (Scopus ID)978-1-55752-852-0 (ISBN)
Conference
Asia Communications and Photonics Conference, November 11-14, Shanghai, China
Available from: 2015-03-23 Created: 2015-03-23 Last updated: 2018-01-11Bibliographically approved
Muhammad, A., Zervas, G. S., Amaya, N., Simeonidou, D. & Forchheimer, R. (2014). Cost-Efficient Design of Flexible Optical Networks Implemented by Architecture on Demand. In: 2014 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC): San Francisco, California United States 9–13 March 2014. Paper presented at Optical Fiber Communications Conference and Exhibition (OFC) (pp. W2A.17). IEEE
Open this publication in new window or tab >>Cost-Efficient Design of Flexible Optical Networks Implemented by Architecture on Demand
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2014 (English)In: 2014 OPTICAL FIBER COMMUNICATIONS CONFERENCE AND EXHIBITION (OFC): San Francisco, California United States 9–13 March 2014, IEEE , 2014, p. W2A.17-Conference paper, Published paper (Refereed)
Abstract [en]

Architecture on demand (AoD) node offers considerable flexibility against traditional ROADMs. The paper presents a cost-efficient network planning strategy that exploits the flexibility inherent in AoD. Results show that AoD can save significantly in node modules through a proper network design.

Place, publisher, year, edition, pages
IEEE, 2014
National Category
Communication Systems
Identifiers
urn:nbn:se:liu:diva-122087 (URN)10.1364/OFC.2014.W2A.17 (DOI)000361020300538 ()978-1-55752-993-0 (ISBN)
Conference
Optical Fiber Communications Conference and Exhibition (OFC)
Available from: 2015-10-19 Created: 2015-10-19 Last updated: 2015-10-27
Ajma, M., Furdek, M., Monti, P., Wosinska, L. & Forchheimer, R. (2014). Dynamic provisioning utilizing redundant modules in elastic optical networks based on architecture on demand nodes. In: European Conference on Optical Communication (ECOC), 2014: . Paper presented at European Conference on Optical Communication (ECOC), 2014, September 21-25, Cannes, France (pp. 1-3). IEEE
Open this publication in new window or tab >>Dynamic provisioning utilizing redundant modules in elastic optical networks based on architecture on demand nodes
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2014 (English)In: European Conference on Optical Communication (ECOC), 2014, IEEE , 2014, p. 1-3Conference paper, Published paper (Refereed)
Abstract [en]

Survivable synthetic ROADMs are equipped with redundant switching modules to support failure recovery. The paper proposes a dynamic connection provisioning strategy which exploits these idle redundant modules to provision regular traffic resulting in a substantial improvement in the blocking performance.

Place, publisher, year, edition, pages
IEEE, 2014
Keywords
optical fibre networks; telecommunication traffic; demand nodes; dynamic connection provisioning strategy; dynamic provisioning; elastic optical networks; failure recovery; redundant switching modules; survivable synthetic ROADM; Availability; Educational institutions; Optical add-drop multiplexers; Optical fiber networks; Optical switches; Ports (Computers)
National Category
Information Systems Computer Sciences
Identifiers
urn:nbn:se:liu:diva-115906 (URN)10.1109/ECOC.2014.6963998 (DOI)2-s2.0-84915818579 (Scopus ID)
Conference
European Conference on Optical Communication (ECOC), 2014, September 21-25, Cannes, France
Available from: 2015-03-23 Created: 2015-03-23 Last updated: 2018-01-11Bibliographically approved
Markus, N., Frljak, M., Pandzic, I. S., Ahlberg, J. & Forchheimer, R. (2014). Eye pupil localization with an ensemble of randomized trees. Pattern Recognition, 47(2), 578-587
Open this publication in new window or tab >>Eye pupil localization with an ensemble of randomized trees
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2014 (English)In: Pattern Recognition, ISSN 0031-3203, E-ISSN 1873-5142, Vol. 47, no 2, p. 578-587Article in journal (Refereed) Published
Abstract [en]

We describe a method for eye pupil localization based on an ensemble of randomized regression trees and use several publicly available datasets for its quantitative and qualitative evaluation. The method compares well with reported state-of-the-art and runs in real-time on hardware with limited processing power, such as mobile devices.

Place, publisher, year, edition, pages
Elsevier, 2014
Keywords
Eye pupil localization; Boosting; Randomized trees
National Category
Engineering and Technology
Identifiers
urn:nbn:se:liu:diva-103864 (URN)10.1016/j.patcog.2013.08.008 (DOI)000329413000008 ()
Available from: 2014-01-31 Created: 2014-01-30 Last updated: 2017-12-06
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