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  • 1.
    Abellán, C.
    et al.
    ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.
    Acín, A.
    ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain / ICREA - Institució Catalana de Recerca i Estudis Avançats, Barcelona, Spain.
    Alarcón, A.
    Millennium Institute for Research in Optics, Universidad de Concepción, Universidad de Concepción, Concepción, Chile / Departamento de Ingeniería Eléctrica, Universidad de Concepción, Concepción, Chile.
    Alibart, O.
    Université Côte d’Azur, CNRS UMR 7010, Institut de Physique de Nice (INPHYNI), Nice, France.
    Andersen, C. K.
    Department of Physics, ETH Zurich,, Zurich, Switzerland.
    Andreoli, F.
    Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy.
    Beckert, A.
    Department of Physics, ETH Zurich,, Zurich, Switzerland.
    Beduini, F. A.
    ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.
    Bendersky, A.
    Departamento de Computación, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires and Instituto de Investigación en Ciencias de la Comunicación (ICC), CONICET, Buenos Aires, Argentina.
    Bentivegna, M.
    Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy.
    Bierhorst, P.
    National Institute of Standards and Technology, Boulder, CO, USA.
    Burchardt, D.
    Ludwig-Maximilians-Universität, Munich, Germany.
    Cabello, A.
    Departamento de Física Aplicada II, Universidad de Sevilla, Seville, Spain.
    Cariñe, J.
    Millennium Institute for Research in Optics, Universidad de Concepción, Universidad de Concepción, Concepción, Chile.
    Carrasco, S.
    ICFO - Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology, Barcelona, Spain.
    Carvacho, G.
    Dipartimento di Fisica, Sapienza Università di Roma, Rome, Italy.
    Cavalcanti, D.
    Chaves, R.
    Cortés-Vega, J.
    Cuevas, A.
    Delgado, A.
    de Riedmatten, H.
    Eichler, C.
    Farrera, P.
    Fuenzalida, J.
    García-Matos, M.
    Garthoff, R.
    Gasparinetti, S.
    Gerrits, T.
    Ghafari Jouneghani, F.
    Glancy, S.
    Gómez, E. S.
    González, P.
    Guan, J. -Y.
    Handsteiner, J.
    Heinsoo, J.
    Heintze, G.
    Hirschmann, A.
    Jiménez, O.
    Kaiser, F.
    Knill, E.
    Knoll, L. T.
    Krinner, S.
    Kurpiers, P.
    Larotonda, M. A.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Lenhard, A.
    Li, H.
    Li, M. -H.
    Lima, G.
    Liu, B.
    Liu, Y.
    López Grande, I. H.
    Lunghi, T.
    Ma, X.
    Magaña-Loaiza, O. S.
    Magnard, P.
    Magnoni, A.
    Martí­-Prieto, M.
    Martínez, D.
    Mataloni, P.
    Mattar, A.
    Mazzera, M.
    Mirin, R. P.
    Mitchell, M. W.
    Nam, S.
    Oppliger, M.
    Pan, J. -W.
    Patel, R. B.
    Pryde, G. J.
    Rauch, D.
    Redeker, K.
    Rieländer, D.
    Ringbauer, M.
    Roberson, T.
    Rosenfeld, W.
    Salathé, Y.
    Santodonato, L.
    Sauder, G.
    Scheidl, T.
    Schmiegelow, C. T.
    Sciarrino, F.
    Seri, A.
    Shalm, L. K.
    Shi, S. -C
    Slussarenko, S.
    Stevens, M. J.
    Tanzilli, S.
    Toledo, F.
    Tura, J.
    Ursin, R.
    Vergyris, P.
    Verma, V. B.
    Walter, T.
    Wallraff, A.
    Wang, Z.
    Weinfurter, H.
    Weston, M. M.
    White, A. G.
    Wu, C.
    Xavier, Guilherme B.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    You, L.
    Yuan, X.
    Zeilinger, A.
    Zhang, Q.
    Zhang, W.
    Zhong, J.
    Challenging Local Realism with Human Choices2018In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 557, p. 212-216Article in journal (Refereed)
    Abstract [en]

    A Bell test is a randomized trial that compares experimental observations against the philosophical worldview of local realism , in which the properties of the physical world are independent of our observation of them and no signal travels faster than light. A Bell test requires spatially distributed entanglement, fast and high-efficiency detection and unpredictable measurement settings. Although technology can satisfy the first two of these requirements, the use of physical devices to choose settings in a Bell test involves making assumptions about the physics that one aims to test. Bell himself noted this weakness in using physical setting choices and argued that human ‘free will’ could be used rigorously to ensure unpredictability in Bell tests. Here we report a set of local-realism tests using human choices, which avoids assumptions about predictability in physics. We recruited about 100,000 human participants to play an online video game that incentivizes fast, sustained input of unpredictable selections and illustrates Bell-test methodology. The participants generated 97,347,490 binary choices, which were directed via a scalable web platform to 12 laboratories on five continents, where 13 experiments tested local realism using photons, single atoms, atomic ensembles and superconducting devices. Over a 12-hour period on 30 November 2016, participants worldwide provided a sustained data flow of over 1,000 bits per second to the experiments, which used different human-generated data to choose each measurement setting. The observed correlations strongly contradict local realism and other realistic positions in bi-partite and tri-partite 12 scenarios. Project outcomes include closing the ‘freedom-of-choice loophole’ (the possibility that the setting choices are influenced by ‘hidden variables’ to correlate with the particle properties), the utilization of video-game methods for rapid collection of human-generated randomness, and the use of networking techniques for global participation in experimental science.

  • 2.
    Abidin, Aysajan
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Authentication in Quantum Key Distribution: Security Proof and Universal Hash Functions2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Quantum Key Distribution (QKD) is a secret key agreement technique that consists of two parts: quantum transmission and measurement on a quantum channel, and classical post-processing on a public communication channel. It enjoys provable unconditional security provided that the public communication channel is immutable. Otherwise, QKD is vulnerable to a man-in-the-middle attack. Immutable public communication channels, however, do not exist in practice. So we need to use authentication that implements the properties of an immutable channel as well as possible. One scheme that serves this purpose well is the Wegman-Carter authentication (WCA), which is built upon Almost Strongly Universal2 (ASU2) hashing. This scheme uses a new key in each authentication attempt to select a hash function from an ASU2 family, which is then used to generate the authentication tag for a message.

    The main focus of this dissertation is on authentication in the context of QKD. We study ASU2 hash functions, security of QKD that employs a computationally secure authentication, and also security of authentication with a partially known key. Specifically, we study the following.

    First, Universal hash functions and their constructions are reviewed, and as well as a new construction of ASU2 hash functions is presented. Second, security of QKD that employs a specific computationally secure authentication is studied. We present detailed attacks on various practical implementations of QKD that employs this authentication. We also provide countermeasures and prove necessary and sufficient conditions for upgrading the security of the authentication to the level of unconditional security. Third, Universal hash function based multiple authentication is studied. This uses a fixed ASU2 hash function followed by one-time pad encryption, to keep the hash function secret. We show that the one-time pad is necessary in every round for the authentication to be unconditionally secure. Lastly, we study security of the WCA scheme, in the case of a partially known authentication key. Here we prove tight information-theoretic security bounds and also analyse security using witness indistinguishability as used in the Universal Composability framework.

    List of papers
    1. New Universal Hash Functions
    Open this publication in new window or tab >>New Universal Hash Functions
    2012 (English)In: Lecture Notes in Computer Science, Vol. 7242 / [ed] Frederik Armknecht and Stefan Lucks, Springer Berlin Heidelberg , 2012, p. 99-108Conference paper, Published paper (Refereed)
    Abstract [en]

    Universal hash functions are important building blocks for unconditionally secure message authentication codes. In this paper, we present a new construction of a class of Almost Strongly Universal hash functions with much smaller description (or key) length than the Wegman-Carter construction. Unlike some other constructions, our new construction has a very short key length and a security parameter that is independent of the message length, which makes it suitable for authentication in practical applications such as Quantum Cryptography.

    Place, publisher, year, edition, pages
    Springer Berlin Heidelberg, 2012
    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 7242
    National Category
    Other Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-84711 (URN)10.1007/978-3-642-34159-5_7 (DOI)978-3-642-34158-8 (ISBN)978-3-642-34159-5 (ISBN)
    Conference
    4th Western European Workshop on Research in Cryptology, WEWoRC 2011, Weimar, Germany, July 20-22, 2011
    Projects
    ICG QC
    Available from: 2012-10-18 Created: 2012-10-17 Last updated: 2018-01-31
    2. Vulnerability of "A Novel Protocol-Authentication Algorithm Ruling out a Man-in-the-Middle Attack in Quantum Cryptography"
    Open this publication in new window or tab >>Vulnerability of "A Novel Protocol-Authentication Algorithm Ruling out a Man-in-the-Middle Attack in Quantum Cryptography"
    2009 (English)In: International Journal of Quantum Information, ISSN 0219-7499, Vol. 7, no 5, p. 1047-1052Article in journal (Refereed) Published
    Abstract [en]

    In this paper, we review and comment on "A novel protocol-authentication algorithm ruling out a man-in-the-middle attack in quantum cryptography" [M. Peev et al., Int. J. Quant. Inf. 3 (2005) 225]. In particular, we point out that the proposed primitive is not secure when used in a generic protocol, and needs additional authenticating properties of the surrounding quantum-cryptographic protocol.

    Keywords
    Quantum cryptography, quantum key distribution, authentication
    National Category
    Natural Sciences
    Identifiers
    urn:nbn:se:liu:diva-20405 (URN)10.1142/S0219749909005754 (DOI)
    Projects
    ICG QC
    Available from: 2009-09-08 Created: 2009-09-07 Last updated: 2016-08-31Bibliographically approved
    3. Attacks on quantum key distribution protocols that employ non-ITS authentication
    Open this publication in new window or tab >>Attacks on quantum key distribution protocols that employ non-ITS authentication
    Show others...
    2016 (English)In: Quantum Information Processing, ISSN 1570-0755, E-ISSN 1573-1332, Vol. 15, no 1, p. 327-362Article in journal (Refereed) Published
    Abstract [en]

    We demonstrate how adversaries with unbounded computing resources can break Quantum Key Distribution (QKD) protocols which employ a particular message authentication code suggested previously. This authentication code, featuring low key consumption, is not Information-Theoretically Secure (ITS) since for each message the eavesdropper has intercepted she is able to send a different message from a set of messages that she can calculate by finding collisions of a cryptographic hash function. However, when this authentication code was introduced it was shown to prevent straightforward Man-In-The-Middle (MITM) attacks against QKD protocols.

    In this paper, we prove that the set of messages that collide with any given message under this authentication code contains with high probability a message that has small Hamming distance to any other given message. Based on this fact we present extended MITM attacks against different versions of BB84 QKD protocols using the addressed authentication code; for three protocols we describe every single action taken by the adversary. For all protocols the adversary can obtain complete knowledge of the key, and for most protocols her success probability in doing so approaches unity.

    Since the attacks work against all authentication methods which allow to calculate colliding messages, the underlying building blocks of the presented attacks expose the potential pitfalls arising as a consequence of non-ITS authentication in QKDpostprocessing. We propose countermeasures, increasing the eavesdroppers demand for computational power, and also prove necessary and sufficient conditions for upgrading the discussed authentication code to the ITS level.

    Place, publisher, year, edition, pages
    Springer Publishing Company, 2016
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-91260 (URN)10.1007/s11128-015-1160-4 (DOI)000372876800020 ()
    Projects
    ICG QC
    Note

    Vid tiden för disputation förelåg publikationen som manuskript

    Funding agencies: Vienna Science and Technology Fund (WWTF) [ICT10-067]; Austrian Research Promotion Agency (FFG) [Bridge-2364544]

    Available from: 2013-04-18 Created: 2013-04-18 Last updated: 2017-12-06Bibliographically approved
    4. On Security of Universal Hash Function Based Multiple Authentication
    Open this publication in new window or tab >>On Security of Universal Hash Function Based Multiple Authentication
    2012 (English)In: Lecture Notes in Computer Science, Vol. 7618 / [ed] Chim, Tat Wing and Yuen, Tsz Hon, 2012, p. 303-310Conference paper, Published paper (Refereed)
    Abstract [en]

    Universal hash function based multiple authentication was originally proposed by Wegman and Carter in 1981. In this authentication, a series of messages are authenticated by first hashing each message by a fixed (almost) strongly universal$_2$ hash function and then encrypting the hash value with a preshared one-time pad. This authentication is unconditionally secure. In this paper, we show that the unconditional security cannot be guaranteed if the hash function output for the first message is not encrypted, as remarked in [Atici and Stinson, CRYPTO '96. LNCS, vol. 1109]. This means that it is not only sufficient, but also necessary, to encrypt the hash of every message to be authenticated in order to have unconditional security. The security loss is demonstrated by a simple existential forgery attack.

    Series
    Lecture Notes in Computer Science, ISSN 0302-9743, E-ISSN 1611-3349 ; 7618
    National Category
    Engineering and Technology
    Identifiers
    urn:nbn:se:liu:diva-84732 (URN)10.1007/978-3-642-34129-8_27 (DOI)978-3-642-34128-1 (ISBN)978-3-642-34129-8 (ISBN)
    Conference
    14th International Conference on Information and Communications Security, ICICS 2012, Hong Kong, China, October 29-31, 2012
    Projects
    ICG QC
    Available from: 2012-10-18 Created: 2012-10-18 Last updated: 2018-02-12
    5. Direct proof of security of Wegman-Carter authentication with partially known key
    Open this publication in new window or tab >>Direct proof of security of Wegman-Carter authentication with partially known key
    2014 (English)In: Quantum Information Processing, ISSN 1570-0755, E-ISSN 1573-1332, Vol. 13, no 10, p. 2155-2170Article in journal (Refereed) Published
    Abstract [en]

    Information-theoretically secure (ITS) authentication is needed in Quantum Key Distribution (QKD). In this paper, we study security of an ITS authentication scheme proposed by Wegman& Carter, in the case of partially known authentication key. This scheme uses a new authentication key in each authentication attempt, to select a hash function from an Almost Strongly Universal2 hash function family. The partial knowledge of the attacker is measured as the trace distance between the authentication key distribution and the uniform distribution; this is the usual measure in QKD. We provide direct proofs of security of the scheme, when using partially known key, first in the information-theoretic setting and then in terms of witness indistinguishability as used in the Universal Composability (UC) framework. We find that if the authentication procedure has a failure probability ε and the authentication key has an ε´ trace distance to the uniform, then under ITS, the adversary’s success probability conditioned on an authentic message-tag pair is only bounded by ε +|Ƭ|ε´, where |Ƭ| is the size of the set of tags. Furthermore, the trace distance between the authentication key distribution and the uniform increases to |Ƭ|ε´ after having seen an authentic message-tag pair. Despite this, we are able to prove directly that the authenticated channel is indistinguishable from an (ideal) authentic channel (the desired functionality), except with probability less than ε + ε´. This proves that the scheme is (ε + ε´)-UC-secure, without using the composability theorem.

    Place, publisher, year, edition, pages
    Springer, 2014
    Keywords
    Authentication, Strongly Universal hash functions, Partially known key, Trace distance, Universal Composability, Quantum Key Distribution.
    National Category
    Electrical Engineering, Electronic Engineering, Information Engineering
    Identifiers
    urn:nbn:se:liu:diva-91264 (URN)10.1007/s11128-013-0641-6 (DOI)000341842000002 ()
    Projects
    ICG QC
    Available from: 2013-04-18 Created: 2013-04-18 Last updated: 2017-12-06Bibliographically approved
  • 3.
    Abidin, Aysajan
    Linköping University, Department of Electrical Engineering, Information Coding.
    On Security of Universal Hash Function Based Multiple Authentication2012In: Lecture Notes in Computer Science, Vol. 7618 / [ed] Chim, Tat Wing and Yuen, Tsz Hon, 2012, p. 303-310Conference paper (Refereed)
    Abstract [en]

    Universal hash function based multiple authentication was originally proposed by Wegman and Carter in 1981. In this authentication, a series of messages are authenticated by first hashing each message by a fixed (almost) strongly universal$_2$ hash function and then encrypting the hash value with a preshared one-time pad. This authentication is unconditionally secure. In this paper, we show that the unconditional security cannot be guaranteed if the hash function output for the first message is not encrypted, as remarked in [Atici and Stinson, CRYPTO '96. LNCS, vol. 1109]. This means that it is not only sufficient, but also necessary, to encrypt the hash of every message to be authenticated in order to have unconditional security. The security loss is demonstrated by a simple existential forgery attack.

  • 4.
    Abidin, Aysajan
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Direct proof of security of Wegman-Carter authentication with partially known key2014In: Quantum Information Processing, ISSN 1570-0755, E-ISSN 1573-1332, Vol. 13, no 10, p. 2155-2170Article in journal (Refereed)
    Abstract [en]

    Information-theoretically secure (ITS) authentication is needed in Quantum Key Distribution (QKD). In this paper, we study security of an ITS authentication scheme proposed by Wegman& Carter, in the case of partially known authentication key. This scheme uses a new authentication key in each authentication attempt, to select a hash function from an Almost Strongly Universal2 hash function family. The partial knowledge of the attacker is measured as the trace distance between the authentication key distribution and the uniform distribution; this is the usual measure in QKD. We provide direct proofs of security of the scheme, when using partially known key, first in the information-theoretic setting and then in terms of witness indistinguishability as used in the Universal Composability (UC) framework. We find that if the authentication procedure has a failure probability ε and the authentication key has an ε´ trace distance to the uniform, then under ITS, the adversary’s success probability conditioned on an authentic message-tag pair is only bounded by ε +|Ƭ|ε´, where |Ƭ| is the size of the set of tags. Furthermore, the trace distance between the authentication key distribution and the uniform increases to |Ƭ|ε´ after having seen an authentic message-tag pair. Despite this, we are able to prove directly that the authenticated channel is indistinguishable from an (ideal) authentic channel (the desired functionality), except with probability less than ε + ε´. This proves that the scheme is (ε + ε´)-UC-secure, without using the composability theorem.

  • 5.
    Abidin, Aysajan
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding.
    New Universal Hash Functions2012In: Lecture Notes in Computer Science, Vol. 7242 / [ed] Frederik Armknecht and Stefan Lucks, Springer Berlin Heidelberg , 2012, p. 99-108Conference paper (Refereed)
    Abstract [en]

    Universal hash functions are important building blocks for unconditionally secure message authentication codes. In this paper, we present a new construction of a class of Almost Strongly Universal hash functions with much smaller description (or key) length than the Wegman-Carter construction. Unlike some other constructions, our new construction has a very short key length and a security parameter that is independent of the message length, which makes it suitable for authentication in practical applications such as Quantum Cryptography.

  • 6.
    Abidin, Aysajan
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Pacher, Christoph
    Austrian Institute of Technology, Austria.
    Lorünser, Thomas
    Austrian Institute of Technology, Austria.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Peev, Momtchil
    Austrian Institute of Technology, Austria.
    Quantum cryptography and authentication with low key-consumption2011In: Proceedings of SPIE - The International Society for Optical Engineering, 2011, p. 818916-Conference paper (Refereed)
    Abstract [en]

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

  • 7.
    Adamsson, Gustav
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Fast and Approximate Text Rendering Using Distance Fields2015Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Distance field text rendering has many advantages compared to most other text renderingsolutions. Two of the advantages are the possibility  to scale the glyphs without losing the crisp edge and less memory consumption. A drawback with distance field text renderingcan be high distance field generation time. The solution for fast distance field text renderingin this thesis generates the distance fields by drawing distance gradients locally over the outlines of the glyphs. This method is much faster than the old exact methods for generating distance fields that often includes multiple passes over the whole image.

    Using the solution for text rendering proposed in this thesis results in good looking text that is generated on the fly. The distance fields are generated on a mobile device in less than 10 ms for most of the glyphs in good quality which is less than the time between two frames.

  • 8.
    Aguilar, Edgar A.
    et al.
    Univ Gdansk, Poland.
    Farkas, Mate
    Univ Gdansk, Poland.
    Martinez, Daniel
    Univ Concepcion, Chile.
    Alvarado, Matias
    Univ Concepcion, Chile.
    Carine, Jaime
    Univ Concepcion, Chile.
    Xavier, Guilherme B
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering. Univ Concepcion, Chile.
    Barra, Johanna F.
    Univ Concepcion, Chile.
    Canas, Gustavo
    Univ Bio Bio, Chile.
    Pawlowski, Marcin
    Univ Gdansk, Poland.
    Lima, Gustavo
    Univ Concepcion, Chile.
    Certifying an Irreducible 1024-Dimensional Photonic State Using Refined Dimension Witnesses2018In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 120, no 23, article id 230503Article in journal (Refereed)
    Abstract [en]

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

  • 9.
    Ahlberg, Jörgen
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Visualization Techniques for Surveillance: Visualizing What Cannot Be Seen and Hiding What Should Not Be Seen2015In: Konsthistorisk Tidskrift, ISSN 0023-3609, E-ISSN 1651-2294, Vol. 84, no 2, p. 123-138Article in journal (Refereed)
    Abstract [en]

    This paper gives an introduction to some of the problems of modern camera surveillance, and how these problems are, or can be, addressed using visualization techniques. The paper is written from an engineering point of view, attempting to communicate visualization techniques invented in recent years to the non-engineer reader. Most of these techniques have the purpose of facilitating for the surveillance operator to recognize or detect relevant events (such as violence), while, in contrast, some have the purpose of hiding information in order to be less privacy-intrusive. Furthermore, there are also cameras and sensors that produce data that have no natural visible form, and methods for visualizing such data are discussed as well. Finally, in a concluding discussion an attempt is made to predict how the discussed methods and techniques will be used in the future. 

  • 10.
    Ahlberg, Jörgen
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Termisk Systemteknik AB, Linköping, Sweden.
    Berg, Amanda
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering. Termisk Systemteknik AB, Linköping, Sweden.
    Evaluating Template Rescaling in Short-Term Single-Object Tracking2015Conference paper (Refereed)
    Abstract [en]

    In recent years, short-term single-object tracking has emerged has a popular research topic, as it constitutes the core of more general tracking systems. Many such tracking methods are based on matching a part of the image with a template that is learnt online and represented by, for example, a correlation filter or a distribution field. In order for such a tracker to be able to not only find the position, but also the scale, of the tracked object in the next frame, some kind of scale estimation step is needed. This step is sometimes separate from the position estimation step, but is nevertheless jointly evaluated in de facto benchmarks. However, for practical as well as scientific reasons, the scale estimation step should be evaluated separately – for example,theremightincertainsituationsbeothermethodsmore suitable for the task. In this paper, we describe an evaluation method for scale estimation in template-based short-term single-object tracking, and evaluate two state-of-the-art tracking methods where estimation of scale and position are separable.

  • 11.
    Ahlberg, Jörgen
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Li, Haibo
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Representing and Compressing MPEG-4 Facial Animation Parameters using Facial Action Basis Functions1999In: IEEE Transactions on Circuits and Systems, ISSN 0098-4094, E-ISSN 1558-1276, Vol. 9, no 3, p. 405-410Article in journal (Refereed)
    Abstract [en]

    In model-based, or semantic, coding, parameters describing the nonrigid motion of objects, e.g., the mimics of a face, are of crucial interest. The facial animation parameters (FAPs) specified in MPEG-4 compose a very rich set of such parameters, allowing a wide range of facial motion. However, the FAPs are typically correlated and also constrained in their motion due to the physiology of the human face. We seek here to utilize this spatial correlation to achieve efficient compression. As it does not introduce any interframe delay, the method is suitable for interactive applications, e.g., videophone and interactive video, where low delay is a vital issue.

  • 12.
    Ahlberg, Jörgen
    et al.
    Linköping University, Department of Electrical Engineering, Computer Vision. Linköping University, Faculty of Science & Engineering.
    Åstrom, Anders
    Swedish Natl Forens Ctr NFC, Linkoping, Sweden.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Simultaneous sensing, readout, and classification on an intensity-ranking image sensor2018In: International journal of circuit theory and applications, ISSN 0098-9886, E-ISSN 1097-007X, Vol. 46, no 9, p. 1606-1619Article in journal (Refereed)
    Abstract [en]

    We combine the near-sensor image processing concept with address-event representation leading to an intensity-ranking image sensor (IRIS) and show the benefits of using this type of sensor for image classification. The functionality of IRIS is to output pixel coordinates (X and Y values) continuously as each pixel has collected a certain number of photons. Thus, the pixel outputs will be automatically intensity ranked. By keeping track of the timing of these events, it is possible to record the full dynamic range of the image. However, in many cases, this is not necessary-the intensity ranking in itself gives the needed information for the task at hand. This paper describes techniques for classification and proposes a particular variant (groves) that fits the IRIS architecture well as it can work on the intensity rankings only. Simulation results using the CIFAR-10 dataset compare the results of the proposed method with the more conventional ferns technique. It is concluded that the simultaneous sensing and classification obtainable with the IRIS sensor yields both fast (shorter than full exposure time) and processing-efficient classification.

    The full text will be freely available from 2019-08-13 11:07
  • 13.
    Ajma, Muhammad
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Furdek, Marija
    School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, Sweden / Faculty of Electrical Engineering and Computing, Dept. of Telecommunications, University of Zagreb, Croatia.
    Monti, Paolo
    School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, Sweden.
    Wosinska, Lena
    School of Information and Communication Technology, KTH Royal Institute of Technology, Stockholm, Sweden.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Dynamic provisioning utilizing redundant modules in elastic optical networks based on architecture on demand nodes2014In: European Conference on Optical Communication (ECOC), 2014, IEEE , 2014, p. 1-3Conference 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.

  • 14.
    Ajmal, Muhammad
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Cavdar, Cicek
    Royal Institute of Technology, KTH, Stockholm, Sweden.
    Wosinska, Lena
    Royal Institute of Technology, KTH, Stockholm, Sweden.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Trading Quality of Transmission for Improved Blocking Performance in All-Optical Networks2013In: Asia Communications and Photonics Conference 2013, 2013, p. AF4E.5-Conference paper (Refereed)
    Abstract [en]

    We propose a connection provisioning strategy in dynamic all-optical networks, which exploit the possibility to allow a tolerable signal quality degradation during a small fraction of holding-time resulting in a significant improvement of blocking performance.

  • 15.
    Ajmal, Muhammad
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Furdek, Marija
    Royal Institute of Technology, KTH, Stockholm, Sweden / Dept. of Telecommunications, University of Zagreb, Croatia.
    Monti, Paolo
    Royal Institute of Technology, KTH, Stockholm, Sweden.
    Wosinska, Lena
    Royal Institute of Technology, KTH, Stockholm, Sweden.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    An Optimization Model for Dynamic Bulk Provisioning in Elastic Optical Networks2014In: Asia Communications and Photonics Conference 2014, Optics Info Base, Optical Society of America, 2014, p. AF3E.6-Conference 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.

  • 16.
    Ajmal, Muhammad
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Zervas, Georgios
    High-Performance Networks Group, University of Bristol, UK.
    Saridis, George
    High-Performance Networks Group, University of Bristol, UK.
    Salas, Emilio H.
    High-Performance Networks Group, University of Bristol, UK.
    Simeonidou, Dimitra
    High-Performance Networks Group, University of Bristol, UK.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Flexible and Synthetic SDM Networks with Multi-core-Fibers Implemented by Programmable ROADMs2014In: Proceedings of European Conference on Optical Communication ECOC2014, Cannes, France, September 21-25 September 2014, IEEE , 2014, p. 1-3Conference paper (Refereed)
    Abstract [en]

    This study looks into network planning issues for synthetic MCF-based SDM networks implemented through programmable ROADMs. The results show that significant savings in switching modules and energy can be attained by exploiting the flexibility inherent in programmable ROADM through a proper network design.

  • 17.
    Ajmal, Muhammad
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Zervas, Georgios
    High-Performance Networks Group, University of Bristol, UK.
    Simeonidou, Dimitra
    High-Performance Networks Group, University of Bristol, UK.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Routing, Spectrum and Core Allocation in Flexgrid SDM Networks with Multi-core Fibers2014In: 2014 INTERNATIONAL CONFERENCE ON OPTICAL NETWORK DESIGN AND MODELING, IEEE , 2014, p. 192-197Conference paper (Refereed)
    Abstract [en]

    Space division multiplexing (SDM) over multi-core fiber (MCF) is advocated as a promising technology to overcome the capacity limit of the current single-core optical networks. However, employing the MCF for flexgrid networks necessitates the development of new concepts, such as routing, spectrum and core allocation (RSCA) for traffic demands. The introduction of MCF in the networks mitigates the spectrum continuity constraint of the routing and spectrum assignment (RSA) problem. In fact cores can be switched freely on different links during routing of the network traffic. Similarly, the route disjointness for demands with same allocated spectrum diminishes to core disjointness at the link level. On the other hand, some new issues such as the inter-core crosstalk should be taken into account while solving the RSCA problem. This paper formulates the RSCA network planning problem using the integer linear programming (ILP) formulation. The aim is to optimally minimize the maximum number of spectrum slices required on any core of MCF of a flexgrid SDM network. Furthermore, a scalable and effective heuristic is proposed for the same problem and its performance is compared with the optimal solution. The results show that the proposed algorithm is able to well approximate the optimal solution based on ILP model.

  • 18.
    Ali, Wajid
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Mohammed, Shahzaan
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Analyzing Wavelength Conversion and Traffic Grooming in Optical WDM Networks2013Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Wavelength conversion and traffic grooming have been among the most researched areas and technologies of importance in optical networking. Network performance improves significantly by relaxing the wavelength continuity constraint using wavelength converters and by improving the wavelength utilization using traffic grooming. We have done a literature review that compares the performance of wavelength conversion devices with different traffic grooming devices. This thesis work analyzes the impact of increasing the number of wavelength conversion devices and grooming capable devices using different placement schemes for our proposed network model, traffic loads and link capacities. Deciding the number and location of these devices to be used in a network is equally important. This work has been done through the simulation of different device placement scenarios and the results have been analyzed using connection blocking probability as the performance metric. Our reviews and work, correctly predict the behavior of results as demonstrated by the results of other referred literatures relating to wavelength conversion and traffic grooming.

  • 19.
    Alvbrant, Joakim
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Keshmiri, Vahid
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Wikner, Jacob
    Linköping University, Department of Electrical Engineering, Integrated Circuits and Systems. Linköping University, Faculty of Science & Engineering.
    Transfer Characteristics and Bandwidth Limitation in a Linear-Drift Memristor Model2015In: 2015 EUROPEAN CONFERENCE ON CIRCUIT THEORY AND DESIGN (ECCTD), IEEE , 2015, p. 332-335Conference paper (Refereed)
    Abstract [en]

    The linear-drift memristor model, suggested by HP Labs a few years ago, is used in this work together with two window functions. From the equations describing the memristor model, the transfer characteristics of a memristor is formulated and analyzed. A first-order estimation of the cut-off frequency is shown, that illustrates the bandwidth limitation of the memristor and how it varies with some of its physical parameters. The design space is elaborated upon and it is shown that the state speed, the variation of the doped and undoped regions of the memristor, is inversely proportional to the physical length, and depth of the device. The transfer characteristics is simulated for Joglekar-Wolf, and Biolek window functions and the results are analyzed. The Joglekar-Wolf window function causes a distinct behavior in the tranfer characteristics at cut-off frequency. The Biolek window function on the other hand gives a smooth state transfer function, at the cost of loosing the one-to-one mapping between charge and state. We also elaborate on the design constraints derived from the transfer characteristics.

  • 20.
    Alwan, Abdulrahman
    Linköping University, Department of Electrical Engineering, Information Coding.
    Implementation of Wavelet-Kalman Filtering Technique for Auditory Brainstem Response2012Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Auditory brainstem response (ABR) evaluation has been one of the most reliable methods for evaluating hearing loss. Clinically available methods for ABR tests require averaging for a large number of sweeps (~1000-2000) in order to obtain a meaningful ABR signal, which is time consuming.  This study proposes a faster new method for ABR filtering based on wavelet-Kalman filter that is able to produce a meaningful ABR signal with less than 500 sweeps. The method is validated against ABR data acquired from 7 normal hearing subjects with different stimulus intensity levels, the lowest being 30 dB NHL. The proposed method was able to filter and produce a readable ABR signal using 400 sweeps; other ABR signal criteria were also presented to validate the performance of the proposed method.

  • 21.
    Ambuluri, Sreehari
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, Faculty of Science & Engineering.
    Garrido, Mario
    Linköping University, Department of Electrical Engineering, Electronics System. Linköping University, The Institute of Technology.
    Caffarena, Gabriel
    Boadilla del Monte, Madrid, Spain.
    Ogniewski, Jens
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Ragnemalm, Ingemar
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    New Radix-2 and Radix-22 Constant Geometry Fast Fourier Transform Algorithms For GPUs2013Conference paper (Refereed)
    Abstract [en]

    This paper presents new radix-2 and radix-22 constant geometry fast Fourier transform (FFT) algorithms for graphics processing units (GPUs). The algorithms combine the use of constant geometry with special scheduling of operations and distribution among the cores. Performance tests on current GPUs show a significant improvements compared to the most recent version of NVIDIA’s well-known CUFFT, achieving speedups of up to 5.6x.

  • 22.
    Amselem, E
    et al.
    Stockholm University, Sweden .
    Bourennane, M
    Stockholm University, Sweden .
    Budroni, C
    University of Siegen, Germany .
    Cabello, A
    University of Seville, Spain .
    Guehne, O
    University of Siegen, Germany .
    Kleinmann, M
    University of Siegen, Germany .
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Wiesniak, M
    University of Gdansk, Poland .
    Editorial Material: Comment on "State-Independent Experimental Test of Quantum Contextuality2013In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 110, no 7Article in journal (Other academic)
    Abstract [en]

    n/a

  • 23.
    Anders, Åström
    et al.
    Combitech AB, Linköping, Sweden .
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    A High Speed 2D Time-to-Impact Algorithm Targeted for Smart Image Sensors2014In: Proc. SPIE 9022, Image Sensors and Imaging Systems 2014, International Society for Optical Engineering; 1999 , 2014, Vol. 9022Conference 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.

  • 24.
    Andersson Hultgren, Jonas
    Linköping University, Department of Electrical Engineering, Information Coding.
    Metoder för förbättrad rumsuppfattning i körsimulatorer2011Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today, driving simulators are a very important resource for conducting studies whichconcern driver behavior and perception. Full control of the scenario andenvironment, costs and safety are all factors which makes simulator studiespreferable over real world studies.

    One issue for driving simulators is that the image is projected onto a twodimensionalscreen, which limits the driver's ability to correctly estimate distanceand speed. It is commonly known that distance and velocity are underestimated indriving simulators.

    The goal of this thesis was to find methods that could lead to better distanceestimation in driving simulators and in this project motion parallax and shadowswere implemented and tested, focusing mainly on the former.At the end of the project, a simulator study was conducted to evaluate the effect ofmotion parallax. Ten participants made two runs each in VTI's Simulator III facility,one with motion parallax enabled and one with it disabled. The scenario that tookplace during the two runs consisted of several overtaking situations and a speedperception test.

    The results from the simulator study showed that the participants tended to positionthemselves farther from the road center line when motion parallax was active insituations when the field of view was obscured by preceding vehicles.

  • 25.
    Andersson, Martin
    Linköping University, Department of Electrical Engineering, Information Coding.
    Parametric Prediction Model for Perceived Voice Quality in Secure VoIP2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    More and more sensitive information is communicated digitally and with thatcomes the demand for security and privacy on the services being used. An accurateQoS metric for these services are of interest both for the customer and theservice provider. This thesis has investigated the impact of different parameterson the perceived voice quality for encrypted VoIP using a PESQ score as referencevalue. Based on this investigation a parametric prediction model has been developedwhich outputs a R-value, comparable to that of the widely used E-modelfrom ITU. This thesis can further be seen as a template for how to construct modelsof other equipments or codecs than those evaluated here since they effect theresult but are hard to parametrise.

    The results of the investigation are consistent with previous studies regarding theimpact of packet loss, the impact of jitter is shown to be significant over 40 ms.The results from three different packetizers are presented which illustrates theneed to take such aspects into consideration when constructing a model to predictvoice quality. The model derived from the investigation performs well withno mean error and a standard deviation of the error of a mere 1:45 R-value unitswhen validated in conditions to be expected in GSM networks. When validatedagainst an emulated 3G network the standard deviation is even lower.v

  • 26.
    Appleby, D. M.
    et al.
    Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada.
    Bengtsson, Ingemar
    Stockholm University.
    Brierley, Stephen
    University of Bristol, UK.
    Grassl, Markus
    National University of Singapore.
    Gross, David
    ETH Zurich, Switzerland.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    The monomial representations of the Clifford group2012In: Quantum information & computation, ISSN 1533-7146, Vol. 12, no 5-6, p. 404-431Article in journal (Refereed)
    Abstract [en]

    We show that the Clifford group-the normaliser of the Weyl-Heisenberg group-can be represented by monomial phase-permutation matrices if and only if the dimension is a square number. This simplifies expressions for SIC vectors, and has other applications to SICs and to Mutually Unbiased Bases. Exact solutions for SICs in dimension 16 are presented for the first time.

  • 27.
    Appleby, D.M.
    et al.
    Perimeter Institute for Theoretical Physics, Waterloo, Ontario, Canada.
    Bengtsson, Ingemar
    Stockholms Universitet, AlbaNova, Fysikum, Stockholm, Sweden.
    Brierley, Stephen
    Heilbronn Institute for Mathematical Research, Department of Mathematics, University of Bristol, United Kingdom.
    Ericsson, Åsa
    Linköping University, Department of Mathematics, Mathematics and Applied Mathematics. Linköping University, The Institute of Technology.
    Grassl, Markus
    Centre for Quantum Technologies, National University of Singapore, Singapore.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Systems of Imprimitivity for the Clifford Group2014In: Quantum information & computation, ISSN 1533-7146, Vol. 14, no 3-4, p. 339-360Article in journal (Refereed)
    Abstract [en]

    It is known that if the dimension is a perfect square the Clifford group can be represented by monomial matrices. Another way of expressing this result is to say that when the dimension is a perfect square the standard representation of the Clifford group has a system of imprimitivity consisting of one dimensional subspaces. We generalize this result to the case of an arbitrary dimension. Let k be the square-free part of the dimension. Then we show that the standard representation of the Clifford group has a system of imprimitivity consisting of k-dimensional subspaces. To illustrate the use of this result we apply it to the calculation of SIC-POVMs (symmetric informationally complete positive operator valued measures), constructing exact solutions in dimensions 8 (hand-calculation) as well as 12 and 28 (machine-calculation).

  • 28.
    Arbring, Joel
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding.
    Hedström, Patrik
    Linköping University, Department of Electrical Engineering, Information Coding.
    On Data Compression for TDOA Localization2010Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    This master thesis investigates different approaches to data compression on common types of signals in the context of localization by estimating time difference of arrival (TDOA). The thesis includes evaluation of the compression schemes using recorded data, collected as part of the thesis work. This evaluation shows that compression is possible while preserving localization accuracy.

    The recorded data is backed up with more extensive simulations using a free space propagation model without attenuation. The signals investigated are flat spectrum signals, signals using phase-shift keying and single side band speech signals. Signals with low bandwidth are given precedence over high bandwidth signals, since they require more data in order to get an accurate localization estimate.

    The compression methods used are transform based schemes. The transforms utilized are the Karhunen-Loéve transform and the discrete Fourier transform. Different approaches for quantization of the transform components are examined, one of them being zonal sampling.

    Localization is performed in the Fourier domain by calculating the steered response power from the cross-spectral density matrix. The simulations are performed in Matlab using three recording nodes in a symmetrical geometry.

    The performance of localization accuracy is compared with the Cramér-Rao bound for flat spectrum signals using the standard deviation of the localization error from the compressed signals.

  • 29.
    Astrom, Anders
    et al.
    Combitech AB, Linköping, Sweden .
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Low-complexity, high-speed, and high-dynamic range time-to-impact algorithm2012In: Journal of Electronic Imaging (JEI), ISSN 1017-9909, E-ISSN 1560-229X, Vol. 21, no 4Article in journal (Refereed)
    Abstract [en]

    We present a method suitable for a time-to-impact sensor. Inspired by the seemingly "low" complexity of small insects, we propose a new approach to optical flow estimation that is the key component in time-to-impact estimation. The approach is based on measuring time instead of the apparent motion of points in the image plane. The specific properties of the motion field in the time-to-impact application are used, such as measuring only along a one-dimensional (1-D) line and using simple feature points, which are tracked from frame to frame. The method lends itself readily to be implemented in a parallel processor with an analog front-end. Such a processing concept [near-sensor image processing (NSIP)] was described for the first time in 1983. In this device, an optical sensor array and a low-level processing unit are tightly integrated into a hybrid analog-digital device. The high dynamic range, which is a key feature of NSIP, is used to extract the feature points. The output from the device consists of a few parameters, which will give the time-to-impact as well as possible transversal speed for off-centered viewing. Performance and complexity aspects of the implementation are discussed, indicating that time-to-impact data can be achieved at a rate of 10 kHz with todays technology.

  • 30.
    Axell, Erik
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    On the Optimal K-term Approximation of a Sparse Parameter Vector MMSE Estimate2009In: Proceedings of the 2009 IEEE Workshop on Statistical Signal Processing (SSP'09), IEEE , 2009, p. 245-248Conference paper (Refereed)
    Abstract [en]

    This paper considers approximations of marginalization sums thatarise in Bayesian inference problems. Optimal approximations ofsuch marginalization sums, using a fixed number of terms, are analyzedfor a simple model. The model under study is motivated byrecent studies of linear regression problems with sparse parametervectors, and of the problem of discriminating signal-plus-noise samplesfrom noise-only samples. It is shown that for the model understudy, if only one term is retained in the marginalization sum, thenthis term should be the one with the largest a posteriori probability.By contrast, if more than one (but not all) terms are to be retained,then these should generally not be the ones corresponding tothe components with largest a posteriori probabilities.

  • 31.
    Berg, Amanda
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology. Termisk Systemteknik AB, Linköping, Sweden.
    Ahlberg, Jörgen
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology. Termisk Systemteknik AB, Linköping, Sweden.
    Classification and temporal analysis of district heating leakages in thermal images2014In: Proceedings of The 14th International Symposium on District Heating and Cooling, 2014Conference paper (Other academic)
    Abstract [en]

    District heating pipes are known to degenerate with time and in some cities the pipes have been used for several decades. Due to bad insulation or cracks, energy or media leakages might appear. This paper presents a complete system for large-scale monitoring of district heating networks, including methods for detection, classification and temporal characterization of (potential) leakages. The system analyses thermal infrared images acquired by an aircraft-mounted camera, detecting the areas for which the pixel intensity is higher than normal. Unfortunately, the system also finds many false detections, i.e., warm areas that are not caused by media or energy leakages. Thus, in order to reduce the number of false detections we describe a machine learning method to classify the detections. The results, based on data from three district heating networks show that we can remove more than half of the false detections. Moreover, we also propose a method to characterize leakages over time, that is, repeating the image acquisition one or a few years later and indicate areas that suffer from an increased energy loss.

  • 32.
    Berg, Amanda
    et al.
    Linköping University, Department of Electrical Engineering. Linköping University, The Institute of Technology. Termisk Systemteknik AB, Linköping, Sweden.
    Ahlberg, Jörgen
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology. Termisk Systemteknik AB, Linköping, Sweden.
    Classification of leakage detections acquired by airborne thermography of district heating networks2014In: 2014 8th IAPR Workshop on Pattern Recognition in Remote Sensing (PRRS), IEEE , 2014, p. 1-4Conference paper (Refereed)
    Abstract [en]

    We address the problem of reducing the number offalse alarms among automatically detected leakages in districtheating networks. The leakages are detected in images capturedby an airborne thermal camera, and each detection correspondsto an image region with abnormally high temperature. Thisapproach yields a significant number of false positives, and wepropose to reduce this number in two steps. First, we use abuilding segmentation scheme in order to remove detectionson buildings. Second, we extract features from the detectionsand use a Random forest classifier on the remaining detections.We provide extensive experimental analysis on real-world data,showing that this post-processing step significantly improves theusefulness of the system.

  • 33.
    Berggren, Magnus
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Bobacka, Johan
    Åbo Akademi.
    Svensson, Per-Olof
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Nilsson, David
    Acreo AB.
    Larsson, Oscar
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Ivaska, Ari
    Åbo Akademi.
    PEDOT: PSS-Based Electrochemical Transistors for Ion-to-Electron Transduction and Sensor Signal Amplification2008In: Organic Semiconductors in Sensor Applications / [ed] D.A. Bernards, R. Owens, G. Malliaras, Springer, 2008, 1, p. 263-280Chapter in book (Other academic)
    Abstract [en]

    The chapter reports the use of organic electrochemical transistors in sensor applications. These transistors are excellent ion-to-electron transducers and can serve as very sensitive transducers in amperometric sensor applications. To further improve their sensitivity, we outline various amplification circuits all realized in organic electrochemical transistors.

  • 34.
    Blackert, Axel
    Linköping University, Department of Electrical Engineering, Information Coding.
    Evaluation of Multi-Threading in Vulkan2016Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    Today processor development has a lot of focus on parallel performance by providing multiple cores that programs can use. The problem with the current version of OpenGL is that it lacks support for utilizing multiple CPU threads for calling rendering commands. Vulkan is a new low level graphics API that gives more control to the developers and provides tools to properly utilize multiple threads for doing rendering operations in parallel. This should give increased performance in situations where the CPU is limiting the performance of the application and the goal of this report is to evaluate how large these performance gains can be in different scenes. To do this evaluation a test program is written with both Vulkan and OpenGL implementations and by rendering the same scene using different APIs and techniques the performance can be compared. In addition to evaluating the multithreaded rendering performance the new explicit pipelines in Vulkan is also evaluated.

  • 35.
    Bäcklund, Henrik
    et al.
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Neijman, Niklas
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Automatic Mesh Decomposition for Real-time Collision Detection2014Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Intersections tests between meshes in physics engines are time consuming and computationalheavy tasks. In order to speed up these intersection tests, each mesh can be decomposedinto several smaller convex hulls where the intersection test between each pair of these smallerhulls becomes more computationally efficient.

    The decomposition of meshes within the game industry is today performed by digital artistsand is considered a boring and time consuming task. Hence, the focus of this master thesislies in automatically decompose a mesh into several smaller convex hulls and to approximatethese decomposed pieces with bounding volumes of different complexity. These boundingvolumes together represents a collision mesh that is fully usable in modern games.

  • 36.
    Cabello, Adan
    et al.
    University of Seville, Spain.
    Gu, Mile
    Nanyang Technology University, Singapore; National University of Singapore, Singapore.
    Guehne, Otfried
    University of Siegen, Germany.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Wiesner, Karoline
    University of Bristol, England.
    Thermodynamical cost of some interpretations of quantum theory2016In: PHYSICAL REVIEW A, ISSN 2469-9926, Vol. 94, no 5, article id 052127Article in journal (Refereed)
    Abstract [en]

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

  • 37.
    Carvacho, Gonzalo
    et al.
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Carine, Jaime
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Saavedra, Gabriel
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Cuevas, Alvaro
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Fuenzalida, Jorge
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Toledo, Felipe
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Figueroa, Miguel
    University of Concepcion, Chile; University of Concepcion, Chile.
    Cabello, Adan
    University of Seville, Spain.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Mataloni, Paolo
    University of Roma La Sapienza, Italy.
    Lima, Gustavo
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Xavier, Guilherme B.
    University of Concepcion, Chile; University of Concepcion, Chile; University of Concepcion, Chile.
    Postselection-Loophole-Free Bell Test Over an Installed Optical Fiber Network2015In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 115, no 3, p. 030503-Article in journal (Refereed)
    Abstract [en]

    Device-independent quantum communication will require a loophole-free violation of Bell inequalities. In typical scenarios where line of sight between the communicating parties is not available, it is convenient to use energy-time entangled photons due to intrinsic robustness while propagating over optical fibers. Here we show an energy-time Clauser-Horne-Shimony-Holt Bell inequality violation with two parties separated by 3.7 km over the deployed optical fiber network belonging to the University of Concepcion in Chile. Remarkably, this is the first Bell violation with spatially separated parties that is free of the postselection loophole, which affected all previous in-field long-distance energy-time experiments. Our work takes a further step towards a fiber-based loophole-free Bell test, which is highly desired for secure quantum communication due to the widespread existing telecommunication infrastructure.

  • 38.
    Christoph, Heilmair
    Linköping University, Department of Electrical Engineering, Information Coding.
    GPU-Based Visualisation of Viewshed from Roads or Areas in a 3D Environment2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Viewshed refers to the calculation and visualisation of what part of a terrain isvisible from a given observer point. It is used within many fields, such as militaryplanning or telecommunication tower placement. So far, no general fast methodsexist for calculating the viewshed for multiple observers that may for instancerepresent a road within the terrain. Additionally, if the terrain contains over-lapping structures such as man-made constructions like bridges, most currentviewshed algorithms fail. This report describes two novel methods for viewshedcalculation using multiple observers for terrain that may contain overlappingstructures. The methods have been developed at Vricon in Linköping as a Mas-ter’s Thesis project. Both methods are implemented using the graphics program-ming unit and the OpenGL graphics library, using a computer graphics approach.Results are presented in the form of figures and images, as well as running timetables using two different test setups. Lastly, future possible improvements arealso discussed. The results show that the first method is a viable real-time solu-tion and that the second method requires some additional work.

  • 39.
    Cirkic, Mirsad
    et al.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Persson, Daniel
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Larsson, Erik G.
    Linköping University, Department of Electrical Engineering, Communication Systems. Linköping University, The Institute of Technology.
    Approximating the LLR Distribution for a Class of Soft-Output MIMO Detectors2012In: IEEE Transactions on Signal Processing, ISSN 1053-587X, E-ISSN 1941-0476, Vol. 60, no 12, p. 6421-6434Article in journal (Refereed)
    Abstract [en]

    We present approximations of the LLR distribution for a class of fixed-complexity soft-output MIMO detectors, such as the optimal soft detector and the soft-output via partial marginalization detector. More specifically, in a MIMO AWGN setting, we approximate the LLR distribution conditioned on the transmitted signal and the channel matrix with a Gaussian mixture model (GMM). Our main results consist of an analytical expression of the GMM model (including the number of modes and their corresponding parameters) and a proof that, in the limit of high SNR, this LLR distribution converges in probability towards a unique Gaussian distribution.

  • 40.
    Dalkvist, Mikael
    Linköping University, Department of Electrical Engineering, Information Coding.
    Image Completion Using Local Images2011Independent thesis Advanced level (degree of Master (One Year)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Image completion is a process of removing an area from a photograph and replacing it with suitable data. Earlier methods either search for this relevant data within the image itself, or extends the search to some form of additional data, usually some form of database.

    Methods that search for suitable data within the image itself has problems when no suitable data can be found in the image. Methods that extend their search has in earlier work either used some form of database with labeled images or a massive database with photos from the Internet. For the labels in a database to be useful they typically needs to be entered manually, which is a very time consuming process. Methods that uses databases with millions of images from the Internet has issues with copyrighted images, storage of the photographs and computation time.

    This work shows that a small database of the user’s own private, or professional, photos can be used to improve the quality of image completions. A photographer today typically take many similar photographs on similar scenes during a photo session. Therefore a smaller number of images are needed to find images that are visually and structurally similar, than when random images downloaded from the internet are used.

    Thus, this approach gains most of the advantages of using additional data for the image completions, while at the same time minimizing the disadvantages. It gains a better ability to find suitable data without having to process millions of irrelevant photos.

  • 41.
    Dzhafarov, Ehtibar N.
    et al.
    Purdue University, IN 47907 USA.
    Kujala, Janne V.
    University of Jyvaskyla, Finland.
    Larsson, Jan-Åke
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Contextuality in Three Types of Quantum-Mechanical Systems2015In: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 45, no 7, p. 762-782Article in journal (Refereed)
    Abstract [en]

    We present a formal theory of contextuality for a set of random variables grouped into different subsets (contexts) corresponding to different, mutually incompatible conditions. Within each context the random variables are jointly distributed, but across different contexts they are stochastically unrelated. The theory of contextuality is based on the analysis of the extent to which some of these random variables can be viewed as preserving their identity across different contexts when one considers all possible joint distributions imposed on the entire set of the random variables. We illustrate the theory on three systems of traditional interest in quantum physics (and also in non-physical, e.g., behavioral studies). These are systems of the Klyachko-Can-Binicioglu-Shumovsky-type, Einstein-Podolsky-Rosen-Bell-type, and Suppes-Zanotti-Leggett-Garg-type. Listed in this order, each of them is formally a special case of the previous one. For each of them we derive necessary and sufficient conditions for contextuality while allowing for experimental errors and contextual biases or signaling. Based on the same principles that underly these derivations we also propose a measure for the degree of contextuality and compute it for the three systems in question.

  • 42.
    Edhammer, Jens
    Linköping University, Department of Electrical Engineering, Information Coding.
    Rigid Body Physics for Synthetic Data Generation2016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    For synthetic data generation with concave collision objects, two physics simu- lations techniques are investigated; convex decomposition of mesh models for globally concave collision results, used with the physics simulation library Bullet, and a GPU implemented rigid body solver using spherical decomposition and impulse based physics with a spatial sorting-based collision detection.

    Using the GPU solution for rigid body physics suggested in the thesis scenes con- taining large amounts of bodies results in a rigid body simulation up to 2 times faster than Bullet 2.83. 

  • 43.
    Einar, Marcus
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Implementing and Testing Self-Timed Rings on a FPGA as Entropy Sources2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Random number generators are basic building blocks of modern cryptographic systems. Usually pseudo random number generators, carefully constructed deter- ministic algorithms that generate seemingly random numbers, are used. These are built upon foundations of thorough mathematical analysis and have been subjected to stringent testing to make sure that they can produce pseudo random sequences at a high bit-rate with good statistical properties.

    A pseudo random number generator must be initiated with a starting value. Since they are deterministic, the same starting value used twice on the same pseudo random number generator will produce the same seemingly random sequence. Therefore it is of utmost importance that the starting value contains enough en- tropy so that the output cannot be predicted or reproduced in an attack. To gen- erate a high entropy starting value, a true random number generator that uses sampling of some physical non-deterministic phenomenon to generate entropy, can be used. These are generally slower than their pseudo random counterparts but in turn need not generate the same amount of random values.

    In field programmable gate arrays (FPGA), generating random numbers is not trivial since they are built upon digital logic. A popular technique to generate entropy within a FPGA is to sample jittery clock signals. A quite recent technique proposed to create a robust clock signals, that contains such jitter, is to use self- timed ring oscillators. These are structures in which several events can propagate freely at an evenly spaced phase distribution.

    In this thesis self-timed rings of six different lengths is implemented on a spe- cific FPGA hardware. The different implementations are tested with the TestU01 test suite. The results show that two of the implementations have a good oscilla- tory behaviour that is well suited for use as random number generators. Others exhibit unexpected behaviours that are not suited to be used in a random num- ber generator. Two of the implemented random generators passed all tests in the TestU01 batteries Alphabit and BlockAlphabit. One of the generators was deemed not fit for use in a random number generator after failing all of the tests. The last three were not subjected to any tests since they did not behave as ex- pected.

  • 44.
    Elfwing, Anders
    et al.
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ponseca, Carlito
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Ouyang, Liangqi
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Urbanowicz, Andrzej
    Ctr Phys Sci and Technol, Lithuania; TERAVIL Ltd, Lithuania.
    Krotkus, Arunas
    Ctr Phys Sci and Technol, Lithuania.
    Tu, Deyu
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Inganäs, Olle
    Linköping University, Department of Physics, Chemistry and Biology, Biomolecular and Organic Electronics. Linköping University, Faculty of Science & Engineering.
    Conducting Helical Structures from Celery Decorated with a Metallic Conjugated Polymer Give Resonances in the Terahertz Range2018In: Advanced Functional Materials, ISSN 1616-301X, E-ISSN 1616-3028, Vol. 28, no 24, article id 1706595Article in journal (Refereed)
    Abstract [en]

    A method to decorate cellulose-based helices retrieved from the plant celery with a conductive polymer is proposed. Using a layer-by-layer method, the decoration of the polyanionic conducting polymer poly(4-(2,3-dihydrothieno [3,4-b]-[1,4]dioxin-2-yl-methoxy)-1-butanesulfonic acid (PEDOT-S) is enhanced after coating the negatively charged cellulose helix with a polycationic polyethyleneimine. Microscopy techniques and two-point probe are used to image the structure and measure the conductivity of the helix. Analysis of the optical and electrical properties of the coated helix in the terahertz (THz) frequency range shows a resonance close to 1 THz and a broad shoulder that extends to 3.5 THz, consistent with electromagnetic models. Moreover, as helical antennas, it is shown that both axial and normal modes are present, which are correlated to the orientation and antenna electrical lengths of the coated helices. This work opens the possibility of designing tunable terahertz antennas through simple control of their dimensions and orientation.

  • 45.
    Engvall, Sebastian
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Kaijsers algoritm för beräkning av Kantorovichavstånd parallelliserad i CUDA2013Independent thesis Basic level (university diploma), 10,5 credits / 16 HE creditsStudent thesis
    Abstract [en]

    This thesis processes the work of developing CPU code and GPU code for Thomas Kaijsers algorithm for calculating the kantorovich distance and the performance between the two is compared. Initially there is a rundown of the algorithm which calculates the kantorovich distance between two images. Thereafter we go through the CPU implementation followed by GPGPU written in CUDA. Then the results are presented. Lastly, an analysis about the results and a discussion with possible improvements is presented for possible future applications.

  • 46.
    Ericsson, Marcus
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, Faculty of Science & Engineering.
    Transmission, Storage, and Visualization of Data with ANT+2015Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Ultra low-powers wireless technology sensors uses when devices is used to consumeslow power. ANT+ sensors can run for years on a single coin battery. In thethesis the ANT+ sensor data is used in an application that can store and visualizethe data.

  • 47.
    Eriksson, Carl-Henrik
    Linköping University, Department of Electrical Engineering, Information Coding.
    Standardiserad informationssäkerhet inom systemutveckling: En pragmatisk metod för uppehållande av en hög standard med ramverket ISO 270002016Independent thesis Advanced level (degree of Master (Two Years)), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    In today’s online world it is important to protect your organization’s valuable information and assets. Information can be stolen or destroyed in many different ways, and it needs to be dealt with not only on a technical level, but also on a management level. However, the current methods are not very intuitive and require a lot of familiarity with information security management. This report explores how planning of information security within an organization can instead be accomplished in a simple and pragmatic manner, without discouraging the user with too much information and making it too complicated. This is done by examining the requirements and controls from the ISO 27000 framework, and with those in regard creating a method that’s more useful, intuitive, and easy to follow. 

  • 48.
    Eriksson, Madeleine
    Linköping University, Department of Electrical Engineering, Information Coding.
    Litteraturstudie om möjligheterna att analysera och modifiera talsignaler2010Independent thesis Basic level (university diploma), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This bachelor thesis is a literature study of the possibility to analyze and modify speech signals and will act as a pilotstudy for future theses in speaker verification.The thesis deals with the voice anatomy and physiology, synthesizer history and the various methods available when thevoice is used as a biometric method.A search and evaluation of existing programs have been conducted to determine the relevance of the attacks on theparameters used for speaker verification

  • 49.
    Fabiano, Simone
    et al.
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Usta, Hakan
    Polyera Corp, IL 60077 USA; Abdullah Gul University, Turkey.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Crispin, Xavier
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Facchetti, Antonio
    Polyera Corp, IL 60077 USA.
    Berggren, Magnus
    Linköping University, Department of Science and Technology, Physics and Electronics. Linköping University, The Institute of Technology.
    Selective Remanent Ambipolar Charge Transport in Polymeric Field-Effect Transistors For High-Performance Logic Circuits Fabricated in Ambient2014In: Advanced Materials, ISSN 0935-9648, E-ISSN 1521-4095, Vol. 26, no 44, p. 7438-7443Article in journal (Refereed)
    Abstract [en]

    n/a

  • 50.
    Forchheimer, Daniel
    et al.
    Royal Institute Technology KTH, Sweden.
    Forchheimer, Robert
    Linköping University, Department of Electrical Engineering, Information Coding. Linköping University, The Institute of Technology.
    Haviland, David B.
    Royal Institute Technology KTH, Sweden.
    Improving image contrast and material discrimination with nonlinear response in bimodal atomic force microscopy2015In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 6, no 6270Article in journal (Refereed)
    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.

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