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  • 251.
    Alfredsson, Stefan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    A Case Study of Recent Mifare Classic Field Deployments From an (In-)Security Perspective2013In: Proceedings of the 21st International Conference on Software, Telecommunications and Computer Networks (SoftCOM 2013), Split, Croatia: FESB, University of Split , 2013Conference paper (Refereed)
    Abstract [en]

    Mifare Classic is a very popular near-field communication technology that provides a shared-key, access-controlled, storage. Although the authentication protocol of Mifare Classic is compromised since half a decade, systems are still being deployed based on this technology, e.g. for access control systems and for public transport ticketing. By using commodity hardware, such as NFC enabled smartphones, by passing the security measures in some cases only require the installation and operation of a smartphone app. To this end, we present case studies of a number of recent Mifare Classic systems deployed during the last year, to serve as an illustration of practical security problems and to raise awareness thereof among NFC technology buyers and system implementors.

  • 252.
    Alfredsson, Stefan
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    A Cross-Layer Perspective on Transport Protocol Performance in Wireless Networks2012Doctoral thesis, monograph (Other academic)
    Abstract [en]

    Communication by wireless technologies has seen a tremendous growth in the last decades. Mobile phone technology and wireless broadband solutions are rapidly replacing the last-hop wireline connectivity for telephones and Internet access.  Research has, however, shown that Internet traffic can experience a performance degradation over wireless compared to wired networks.  The inherent properties of radio communication lead to a higher degree of unreliability, compared to communication by wire or fiber.  This can result in an increased amount of transmission errors, packet loss, delay and delay variations, which in turn affect the performance of the main Internet transport protocols TCP and UDP.  This dissertation examines the cross-layer relationship between wireless transmission and the resulting performance on the transport layer. To this end, experimental evaluations of TCP and UDP over a wireless 4G downlink system proposal are performed.  The experiment results show, in a holistic scenario, that link-level adaptive modulation, channel prediction, fast persistent link retransmissions, and channel scheduling, enables the transport protocols TCP and UDP to perform well and utilize the wireless link efficiently.  Further, a novel approach is proposed where a modified TCP receiver can choose to accept packets that are corrupted by bit errors. Results from network emulation experiments indicate that by accepting and acknowledging even small amounts of corrupted data, a much higher throughput can be maintained compared to standard TCP.

  • 253.
    Alfredsson, Stefan
    Karlstad University, Division for Information Technology.
    TCP in Wireless Networks: Challenges, Optimizations and Evaluations2005Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    This thesis presents research on transport layer behavior in wireless networks. As the Internet is expanding its reach to include mobile devices, it has become apparent that some of the original design assumptions for the dominant transport protocol, TCP, are approaching their limits. A key feature of TCP is the congestion control algorithm, constructed with the assumption that packet loss is normally very low, and that packet loss therefore is a sign of network congestion. This holds true for wired networks, but for mobile wireless networks non-congestion related packet loss may appear. The varying signal power inherent with mobility and handover between base-stations are two example causes of such packet loss. This thesis provides an overview of the challenges for TCP in wireless networks together with a compilation of a number of suggested TCP optimizations for these environments. A TCP modification called TCP-L is proposed. It allows an application to increase its performance, in environments where residual bit errors normally give a degraded throughput, by making a reliability tradeoff. The performance of TCP-L is experimentally evaluated with an implementation in the Linux kernel. The transport layer performance in a 4G scenario is also experimentally investigated, focusing on the impact of the link layer design and its parameterization. Further, for emulation-based protocol evaluations, controlled packet loss and bit error generation is shown to be an important aspect.

  • 254.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    Bit Error Tolerant Multimedia Transport2004In: Perspectives on Multimedia: Communication, Media and Information Technology, Chichester: John Wiley & Sons, 2004, p. 175-191Chapter in book (Other academic)
  • 255.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Division for Information Technology.
    TCP-L: Allowing Bit Errors in Wireless TCP2003In: Proceedings of the 12th IST Summit on Mobile and Wireless Communications: Enabling a Pervasive Wireless World / [ed] Atílio Gameiro, Institute for Operations Research and the Management Sciences (INFORMS), 2003, p. 149-154Conference paper (Refereed)
    Abstract [en]

    This paper presents a technique to improve the performance of TCP and the utilization of wireless networks.Wireless links exhibit high rates of bit errors, compared to communication over wireline or fiber. Since TCP cannotseparate packet losses due to bit errors versus congestion,all losses are treated as signs of congestion and congestionavoidance is initiated. This paper explores the possibility of accepting TCP packets with an erroneous checksum, toimprove network performance for those applications that can tolerate bit errors. Since errors may be in the TCP header aswell as the payload, the possibility of recovering the headeris discussed. An algorithm for this recovery is also presented.Experiments with an implementation have been performed,which show that large improvements in throughput can beachieved, depending on link and error characteristics.

  • 256.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    A 4G Link Level Emulator for Transport Protocol Evaluation2004In: Proceedings of The Second Swedish National Computer Networking Workshop (SNCNW), 2004, p. 19-23Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and networkemulator, based upon the "Wireless IP" 4G system proposalfrom Uppsala University and partners. In wireless fading down-links (base to terminals) link-level frames are scheduled andthe transmission is adapted on a fast time scale. With fastlink adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteractedat the physical and link layers. A purpose of the emulatoris to investigate the resulting interaction with transport layer protocols. The emulator is built on Internet technologies, andis installed as a gateway between communicating hosts. The paper gives an overview of the emulator design, and presentspreliminary experiments with three different TCP variants. The results illustrate the functionality of the emulator by showing theeffect of changing link layer parameters on the different TCP variants.

  • 257.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Cross-layer analysis of TCP performance in a 4G system2007In: Proceedings of the 15th International Conference on Software, Telecommunications and Computer Networks, IEEE Computer Society, 2007Conference paper (Refereed)
    Abstract [en]

    This paper presents results from an experimental study of TCP in a wireless 4G evaluation system. Test-bed results on transport layer performance are presented and analyzed in relation to several link layer aspects. The aspects investigated are the impact of channel prediction errors, channel scheduling, delay, and adaptive modulation switch level, on TCP performance. The paper contributes a cross-layer analysis of the interaction between symbol modulation levels, different scheduling strategies, channel prediction errors and the resulting frame retransmissions effect on TCP. The paper also shows that highly persistent ARQ with fast link retransmissions do not interact negatively with the TCP retransmission timer even for short round trip delays.

  • 258.
    Alfredsson, Stefan
    et al.
    Karlstad University, Division for Information Technology. Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Division for Information Technology.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Emulation and Validation of a 4G System Proposal2005In: Proceedings of RadioVetenskap och Kommunikation 2005: Volume II, 2005, p. 357-362Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and network emulator,along with experiments and validation against the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at thephysical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the link layer. The paper gives an overview of the emulator design, and presents experimental results with three different TCP variants in combination with various link layer characteristics.

  • 259.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Impact of 4G Wireless Link Configurations on VoIP Network Performance2008In: Proceedings of the 2008 IEEE International Symposium on Wireless Communication Systems, IEEE Communications Society, 2008, p. 708-712Conference paper (Refereed)
    Abstract [en]

    The performance of applications in wireless networks is partly dependent upon the link configuration. Link characteristics varies with frame retransmission persistency, link frame retransmission delay, adaptive modulation strategies, coding, and more. The link configuration and channel conditions can lead to packet loss, delay and delay variations, which impact different applications in different ways. A bulk transfer application may tolerate delays to a large extent, while packet loss is undesirable. On the other hand, real-time interactive applications are sensitive to delay and delay variations, but may tolerate packet loss to a certain extent. This paper contributes a study of the effect of link frame retransmission persistency and delay on packet loss and latency for real-time interactive applications. The results indicate that a reliable retransmission mechanism with fast link retransmissions in the range of 2-8 ms is sufficient to provide an upper delay bound of 50 ms over the wireless link, which is well within the delay budget of voice over IP applications.

  • 260.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Mikael, Sternad
    Signaler och System, Uppsala universitet.
    Transport Protocol Performance over 4G Links: Emulation Methodology and Results2006In: Proceedings of the International Symposium on Wireless Communication Systems (ISWCS), IEEE Computer Society, 2006, p. 327-332Conference paper (Refereed)
    Abstract [en]

    This paper presents a wireless link and network emulator for the "Wireless IP" 4G system proposal from Uppsala University and partners. In wireless fading downlinks (base to terminals) link-level frames are scheduled and the transmission is adapted on a fast time scale. With fast link adaptation and fast link level retransmission, the fading properties of wireless links can to a large extent be counteracted at the physical and link layers. The emulator has been used to experimentally investigate the resulting interaction between the transport layer and the physical/link layer in such a downlink. The paper introduces the Wireless IP system, describes the emulator design and implementation, and presents experimental results with TCP in combination with various physical/link layer parameters. The impact of link layer ARQ persistency, adaptive modulation, prediction errors and simple scheduling are all considered.

  • 261.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Impact of TCP Congestion Control on Bufferbloat in Cellular Networks2013In: Proceedings of the 14th IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM 2013) / [ed] Angelos Lazaris, Balaji Rengarajan, IEEE Press, 2013Conference paper (Refereed)
    Abstract [en]

    The existence of excessively large and too filled network buffers, known as bufferbloat, has recently gained attention as a major performance problem for delay-sensitive applications. One important network scenario where bufferbloat may occur is cellular networks.

    This paper investigates the interaction between TCP congestion control and buffering in cellular networks. Extensive measurements have been performed in commercial 3G, 3.5G and 4G cellular networks, with a mix of long and short TCP flows using the CUBIC, NewReno and Westwood+ congestion control algorithms. The results show that the completion times of short flows increase significantly when concurrent long flow traffic is introduced. This is caused by increased buffer occupancy from the long flows. In addition, for 3G and 3.5G the completion times are shown to depend significantly on the congestion control algorithms used for the background flows, with CUBIC leading to significantly larger completion times.

  • 262.
    Alfredsson, Stefan
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Del Giudice, Giacomo
    Politecnico di Bari, Italy.
    Garcia, Johan
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    Brunstrom, Anna
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science.
    De Cicco, Luca
    Ecole superieure d'Electricite, France; Politecnico di Bari, Italy.
    Mascolo, Saverio
    Politecnico di Bari, Italy.
    Observations of Bufferbloat in Swedish Cellular Networks2013In: Proceedings of the 9th Swedish National Computer Networking Workshop (SNCNW 2013) / [ed] Bengt Ahlgren, 2013Conference paper (Refereed)
  • 263.
    Algervik, Robert
    Karlstad University, Faculty of Technology and Science, Avdelningen för matematik.
    Embedding Theorems for Mixed Norm Spaces and Applications2010Doctoral thesis, monograph (Other academic)
    Abstract [en]

    This thesis is devoted to the study of mixed norm spaces that arise in connection with embeddings of Sobolev and Besov type spaces. We study different structural, integrability, and smoothness properties of functions satisfying certain mixed norm conditions. Conditions of this type are determined by the behaviour of linear sections of functions. The work in this direction originates in a paper due to Gagliardo (1958), and was further developed by Fournier (1988), by Blei and Fournier (1989), and by Kolyada (2005).

    Here we continue these studies. We obtain some refinements of known embeddings for certain mixed norm spaces introduced by Gagliardo, and we study general properties of these spaces. In connection with these results, we consider a scale of intermediate mixed norm spaces, and prove intrinsic embeddings in this scale.

    We also consider more general, fully anisotropic, mixed norm spaces. Our main theorem states an embedding of these spaces to Lorentz spaces. Applying this result, we obtain sharp embedding theorems for anisotropic Sobolev-Besov spaces, and anisotropic fractional Sobolev spaces. The methods used are based on non-increasing rearrangements, and on estimates of sections of functions and sections of sets. We also study limiting relations between embeddings of spaces of different type. More exactly, mixed norm estimates enable us to get embedding constants with sharp asymptotic behaviour. This gives an extension of the results obtained for isotropic Besov spaces by Bourgain, Brezis, and Mironescu, and for anisotropic Besov spaces by Kolyada.

    We study also some basic properties (in particular the approximation properties) of special weak type spaces that play an important role in the construction of mixed norm spaces, and in the description of Sobolev type embeddings.

    In the last chapter, we study mixed norm spaces consisting of functions that have smooth sections. We prove embeddings of these spaces to Lorentz spaces. From this result, known properties of Sobolev-Liouville spaces follow.

  • 264.
    Algervik, Robert
    Karlstad University, Faculty of Technology and Science, Avdelningen för matematik.
    Embedding Theorems for Mixed Norm Spaces and Applications2008Licentiate thesis, monograph (Other scientific)
    Abstract [en]

    This thesis is devoted to the study of mixed norm spaces that arise in connection with embeddings of Sobolev and Besov type spaces. The work in this direction originates in a paper due to Gagliardo (1958), and was continued by Fournier (1988) and by Kolyada (2005).

    We consider fully anisotropic mixed norm spaces. Our main theorem states an embedding of these spaces into Lorentz spaces. Applying this result, we obtain sharp embedding theorems for anisotropic fractional Sobolev spaces and anisotropic Sobolev-Besov spaces. The methods used are based on non-increasing rearrangements and on estimates of sections of functions and sections of sets. We also study limiting relations between embeddings of spaces of different type. More exactly, mixed norm estimates enable us to get embedding constants with sharp asymptotic behaviour. This gives an extension of the results obtained for isotropic Besov spaces $B_p^\alpha$ by Bourgain, Brezis, and Mironescu, and for Besov spaces $B^{\alpha_1,\dots,\alpha_n}_p$ by Kolyada.

    We study also some basic properties (in particular the approximation properties) of special weak type spaces that play an important role in the construction of mixed norm spaces and in the description of Sobolev type embeddings.

  • 265.
    Algervik, Robert
    et al.
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    Kolyada, Viktor
    Karlstad University, Faculty of Technology and Science, Department of Mathematics.
    On Fournier-Gagliardo mixed norm spaces2011In: Annales Academiae Scientiarum Fennicae Mathematica, ISSN 1239-629X, Vol. 36, p. 493-508Article in journal (Refereed)
    Abstract [en]

    We study mixed norm spaces

    V (Rn)

    that arise in connection with embeddings of

    Sobolev spaces

    W

    1

    1

    (Rn). We prove embeddings of V (Rn)

    into Lorentz type spaces defined in terms

    of iterative rearrangements. Basing on these results, we introduce the scale of mixed norm spaces

    V

    p

    (Rn). We prove that V ½ V p

    and we discuss some questions related to this embedding.

  • 266.
    Alho, Artur
    et al.
    Univ Lisbon, Ctr Math Anal Geometry & Dynam Syst, Inst Super Tecn, Av Rovisco Pais, P-1049001 Lisbon, Portugal..
    Carloni, Sante
    Univ Lisbon, Ctr Multidisciplinar Astrofis CENTRA, Inst Super Tecn, Av Rovisco Pais, P-1049001 Lisbon, Portugal..
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    On dynamical systems approaches and methods in f (R) cosmology2016In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 8, article id 064Article in journal (Refereed)
    Abstract [en]

    We discuss dynamical systems approaches and methods applied to flat Robertson Walker models in f(R)-gravity. We argue that a complete description of the solution space of a model requires a global state space analysis that motivates globally covering state space adapted variables. This is shown explicitly by an illustrative example, f(R) = R + alpha R-2, alpha > 0, for which we introduce new regular dynamical systems on global compactly extended state spaces for the Jordan and Einstein frames. This example also allows us to illustrate several local and global dynamical systems techniques involving, e.g., blow ups of nilpotent fixed points, center manifold analysis, averaging, and use of monotone functions. As a result of applying dynamical systems methods to globally state space adapted dynamical systems formulations, we obtain pictures of the entire solution spaces in both the Jordan and the Einstein frames. This shows, e.g., that due to the domain of the conformal transformation between the Jordan and Einstein frames, not all the solutions in the Jordan frame are completely contained in the Einstein frame. We also make comparisons with previous dynamical systems approaches to f (R) cosmology and discuss their advantages and disadvantages.

  • 267.
    Alho, Artur
    et al.
    University of Lisbon, Portugal.
    Hell, Juliette
    Free University Berlin, Germany.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Global dynamics and asymptotics for monomial scalar field potentials and perfect fluids2015In: Classical and quantum gravity, ISSN 0264-9381, E-ISSN 1361-6382, Vol. 32, no 14, article id 145005Article in journal (Refereed)
    Abstract [en]

    We consider a minimally coupled scalar field with a monomial potential and a perfect fluid in flat Friedmann-Lemaitre-Robertson-Walker cosmology. We apply local and global dynamical systems techniques to a new three-dimensional dynamical systems reformulation of the field equations on a compact state space. This leads to a visual global description of the solution space and asymptotic behavior. At late times we employ averaging techniques to prove statements about how the relationship between the equation of state of the fluid and the monomial exponent of the scalar field affects asymptotic source dominance and asymptotic manifest self-similarity breaking. We also situate the ’attractor’ solution in the three-dimensional state space and show that it corresponds to the one-dimensional unstable center manifold of a de Sitter fixed point, located on an unphysical boundary associated with the dynamics at early times. By deriving a center manifold expansion we obtain approximate expressions for the attractor solution. We subsequently improve the accuracy and range of the approximation by means of Pade approximants and compare with the slow-roll approximation. 

  • 268.
    Alho, Artur
    et al.
    Technical University of Lisbon, Portugal.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Global dynamics and inflationary center manifold and slow-roll approximants2015In: Journal of Mathematical Physics, ISSN 0022-2488, E-ISSN 1089-7658, Vol. 56, no 1, article id 012502Article in journal (Refereed)
    Abstract [en]

    We consider the familiar problem of a minimally coupled scalar field with quadratic potential in flat Friedmann-Lemaître-Robertson-Walker cosmology to illustrate a number of techniques and tools, which can be applied to a wide range of scalar field potentials and problems in, e.g., modified gravity. We present a global and regular dynamical systems description that yields a global understanding of the solution space, including asymptotic features. We introduce dynamical systems techniques such as center manifold expansions and use Padé approximants to obtain improved approximations for the “attractor solution” at early times. We also show that future asymptotic behavior is associated with a limit cycle, which shows that manifest self-similarity is asymptotically broken toward the future and gives approximate expressions for this behavior. We then combine these results to obtain global approximations for the attractor solution, which, e.g., might be used in the context of global measures. In addition, we elucidate the connection between slow-roll based approximations and the attractor solution, and compare these approximations with the center manifold based approximants.

  • 269.
    Alho, Artur
    et al.
    Center for Mathematical Analysis, Geometry and Dynamical Systems, Instituto Superior Técnico, Universidade de Lisboa, Portugal.
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Inflationary alpha-attractor cosmology: A global dynamical systems perspective2017In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 95, no 8, article id 083517Article in journal (Refereed)
    Abstract [en]

    We study flat Friedmann-Lemaitre-Robertson-Walker alpha-attractor E- and T-models by introducing a dynamical systems framework that yields regularized unconstrained field equations on two-dimensional compact state spaces. This results in both illustrative figures and a complete description of the entire solution spaces of these models, including asymptotics. In particular, it is shown that observational viability, which requires a sufficient number of e-folds, is associated with a particular solution given by a one-dimensional center manifold of a past asymptotic de Sitter state, where the center manifold structure also explains why nearby solutions are attracted to this "inflationary attractor solution." A center manifold expansion yields a description of the inflationary regime with arbitrary analytic accuracy, where the slow-roll approximation asymptotically describes the tangency condition of the center manifold at the asymptotic de Sitter state.

  • 270.
    Alho, Artur
    et al.
    Univ Lisbon, Inst Super Tecn, Ctr Math Anal Geometry & Dynam Syst, P-1049001 Lisbon, Portugal..
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Scalar field deformations of Lambda CDM cosmology2015In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 92, no 10, article id 103502Article in journal (Refereed)
    Abstract [en]

    This paper treats nonrelativistic matter and a scalar field phi with a monotonically decreasing potential minimally coupled to gravity in flat Friedmann-Lemaitre-Robertson-Walker cosmology. The field equations are reformulated as a three-dimensional dynamical system on an extended compact state space, complemented with cosmographic diagrams. A dynamical systems analysis provides global dynamical results describing possible asymptotic behavior. It is shown that one should impose global and asymptotic bounds on lambda = -V-1 dV/d phi to obtain viable cosmological models that continuously deform Lambda CDM cosmology. In particular we introduce a regularized inverse power-law potential as a simple specific example.

  • 271.
    Alho, Artur
    et al.
    Univ Lisbon, Portugal..
    Uggla, Claes
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics (from 2013).
    Wainwright, John
    Univ Waterloo, Canada..
    Perturbations of the Lambda-CDM model in a dynamical systems perspective2019In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 9, article id 045Article in journal (Refereed)
    Abstract [en]

    The observational success and simplicity of the ACDM model, and the explicit analytic perturbations thereof, set the standard for any alternative cosmology. It therefore serves as a comparison ground and as a test case for methods which can be extended and applied to other cosmological models. In this paper we introduce dynamical systems and methods to describe linear scalar and tensor perturbations of the ACDM model, which serve as pedagogical examples that show the global illustrative powers of dynamical systems in the context of cosmological perturbations. We also study the asymptotic properties of the shear and Weyl tensors and discuss the validity of the perturbations as approximations to the Einstein field equations. Furthermore, we give a new approximation for the linear growth 5 rate, f (z) = d ln delta/d ln a = Omega(6/11)(m) - 1/70(1-Omega(m))(5/2), where z is the cosmological redshift, Omega(m) = Omega(m)(z), while a is the background scale factor, and show that it is much more accurate than the previous ones in the literature.

  • 272. Ali, A
    et al.
    Hoagg, J. B
    Mossberg, Magnus
    Karlstad University, Faculty of Technology and Science, Department of Physics and Electrical Engineering.
    Bernstein, D. S
    Growing window recursive quadratic optimization with variable regularization2010Conference paper (Refereed)
  • 273.
    Ali, Asad A.
    et al.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    Hoagg, Jesse B.
    Univ Kentucky, Dept Mech Engn, 151 Ralph G Anderson Bldg, Lexington, KY 40507 USA..
    Mossberg, Magnus
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Engineering and Physics.
    Bernstein, Dennis S.
    Univ Michigan, Dept Aerosp Engn, Ann Arbor, MI 48109 USA..
    On the stability and convergence of a sliding-window variable-regularization recursive-least-squares algorithm2016In: International journal of adaptive control and signal processing (Print), ISSN 0890-6327, E-ISSN 1099-1115, Vol. 30, no 5, p. 715-735Article in journal (Refereed)
    Abstract [en]

    A sliding-window variable-regularization recursive-least-squares algorithm is derived, and its convergence properties, computational complexity, and numerical stability are analyzed. The algorithm operates on a finite data window and allows for time-varying regularization in the weighting and the difference between estimates. Numerical examples are provided to compare the performance of this technique with the least mean squares and affine projection algorithms. Copyright (c) 2015 John Wiley & Sons, Ltd.

  • 274.
    Ali, Nour
    et al.
    Brunel University, London, UK.
    Baker, Sean
    University of Limerick, Ireland.
    O’Crowley, Ross
    Red Orkid Limited, Dublin, Ireland.
    Herold, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Buckley, Jim
    University of Limerick, Ireland.
    Architecture consistency: State of the practice, challenges and requirements2018In: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 23, no 1, p. 224-258Article in journal (Refereed)
    Abstract [en]

    Architecture Consistency (AC) aims to align implemented systems with their intended architectures. Several AC approaches and tools have been proposed and empirically evaluated, suggesting favourable results. In this paper, we empirically examine the state of practice with respect to Architecture Consistency, through interviews with nineteen experienced software engineers. Our goal is to identify 1) any practises that the companies these architects work for, currently undertake to achieve AC; 2) any barriers to undertaking explicit AC approaches in these companies; 3) software development situations where practitioners perceive AC approaches would be useful, and 4) AC tool needs, as perceived by practitioners. We also assess current commercial AC tool offerings in terms of these perceived needs. The study reveals that many practitioners apply informal AC approaches as there are barriers for adopting more formal and explicit approaches. These barriers are: 1) Difficulty in quantifying architectural inconsistency effects, and thus justifying the allocation of resources to fix them to senior management, 2) The near invisibility of architectural inconsistency to customers, 3) Practitioners’ reluctance towards fixing architectural inconsistencies, and 4) Practitioners perception that huge effort is required to map the system to the architecture when using more formal AC approaches and tools. Practitioners still believe that AC would be useful in supporting several of the software development activities such as auditing, evolution and ensuring quality attributes. After reviewing several commercial tools, we posit that AC tool vendors need to work on their ability to support analysis of systems made up of different technologies, that AC tools need to enhance their capabilities with respect to artefacts such as services and meta-data, and to focus more on non-maintainability architectural concerns.

  • 275.
    Ali, Nour
    et al.
    Brunel University, London, UK.
    Baker, Sean
    University of Limerick, Ireland.
    O'Crowley, Ross
    Red Orkid Limited, Dublin, Ireland.
    Herold, Sebastian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Buckley, Jim
    University of Limerick, Ireland.
    Architecture consistency: State of the practice, challenges and requirements (vol 23, pg 224, 2018)2018In: Journal of Empirical Software Engineering, ISSN 1382-3256, E-ISSN 1573-7616, Vol. 23, no 3, p. 1868-1869Article in journal (Refereed)
  • 276. Ali Yahiya, Tara
    et al.
    Chaouchi, Hakima
    Kassler, Andreas
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. Karlstad University, Faculty of Economic Sciences, Communication and IT, Centre for HumanIT.
    Pujolle, Guy
    Seamless Interworking of WLAN and WMAN Wireless Networks2006Conference paper (Refereed)
    Abstract [en]

    Future network environments will be heterogeneous and mobile terminals will have the opportunity to dynamically select among many different access technologies. Therefore, it is important to provide service continuity in case of vertical handovers when terminals change the access technology. Two important wireless access technologies are WLAN (Wireless Local Access Networks) and WMAN (Wireless Metropolitan Access Networks) networks. In this paper, we address several challenges related to a seamless integration of those technologies. We highlight important aspects for designing a WLAN/WMAN interworking architecture and we address important Quality of Service (QoS) issues for such interworked systems like degree of QoS support provided by the technologies, QoS mapping and signalling for vertical handover. By formulating several interworking scenarios, where WLAN users with ongoing voice, video and data sessions hand over to WMAN, we study QoS and performance issues and analyse feasibility of seamless session continuity through simulations

  • 277.
    Alizadeh Noghani, Kyoomars
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Towards Seamless Live Migration in SDN-Based Data Centers2018Licentiate thesis, comprehensive summary (Other academic)
    Abstract [en]

    Live migration of Virtual Machines (VMs) has significantly improved the flexibility of modern Data Centers (DCs). Ideally, live migration ought to be seamless which in turn raises challenges on how to minimize service disruption and avoid performance degradation. To address these challenges, a comprehensive support from the underlying network is required. However, legacy DC networks fall short to help as they take a reactive approach to live migration procedure. Moreover, the complexity and inflexibility of legacy DC networks make it difficult to deploy, manage, and improve network technologies that DC providers may need to use for migration.

    In this thesis, we explore the application of Software Defined Networking (SDN) paradigm for making live VM migration more seamless. Exploiting the characteristics of SDN such as its centralized view on network states, we contribute to the body of knowledge by enhancing the quality of intra- and inter-DC live migration. Firstly, for intra-DC migration, we provide an SDN-based solution which minimizes the service disruption by employing OpenFlow-based resiliency mechanisms to prepare a DC network for migration proactively. Secondly, we improve the inter-DC live migration by accelerating the network convergence through announcing the migration in the control plane using MP-BGP protocol. Further, our proposed framework resolves the sub-optimal routing problem by conducting the gateway functionality at the SDN controller. Finally, with the ultimate goal of improving the inter-DC migration, we develop an SDN-based framework which automates the deployment, improves the management, enhances the performance, and increases the scalability of interconnections among DCs.

  • 278.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Ghazzai, Hakim
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    A Generic Framework for Task Offloading in mmWave MEC Backhaul Networks2018In: 2018 IEEE Global Communications Conference (GLOBECOM), IEEE, 2018, p. 1-7Conference paper (Refereed)
    Abstract [en]

    With the emergence of millimeter-Wave (mmWave) communication technology, the capacity of mobile backhaul networks can be significantly increased. On the other hand, Mobile Edge Computing (MEC) provides an appropriate infrastructure to offload latency-sensitive tasks. However, the amount of resources in MEC servers is typically limited. Therefore, it is important to intelligently manage the MEC task offloading by optimizing the backhaul bandwidth and edge server resource allocation in order to decrease the overall latency of the offloaded tasks. This paper investigates the task allocation problem in MEC environment, where the mmWave technology is used in the backhaul network. We formulate a Mixed Integer NonLinear Programming (MINLP) problem with the goal to minimize the total task serving time. Its objective is to determine an optimized network topology, identify which server is used to process a given offloaded task, find the path of each user task, and determine the allocated bandwidth to each task on mmWave backhaul links. Because the problem is difficult to solve, we develop a two-step approach. First, a Mixed Integer Linear Program (MILP) determining the network topology and the routing paths is optimally solved. Then, the fractions of bandwidth allocated to each user task are optimized by solving a quasi-convex problem. Numerical results illustrate the obtained topology and routing paths for selected scenarios and show that optimizing the bandwidth allocation significantly improves the total serving time, particularly for bandwidth-intensive tasks.

  • 279.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hernandez Benet, Cristian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Marotta, Antonio
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Jestin, Patrick
    Ericsson AB, Sweden.
    Srivastava, Vivek V.
    Ericsson AB, Sweden.
    Automating Ethernet VPN deployment in SDN-based Data Centers2017In: 2017 Fourth International Conference on Software Defined Systems (SDS)., IEEE, 2017, p. 61-66Conference paper (Refereed)
    Abstract [en]

    Layer 2 Virtual Private Network (L2VPN) is widely deployed in both service provider networks and enterprises. However, legacy L2VPN solutions have scalability limitations in the context of Data Center (DC) interconnection and networking which require new approaches that address the requirements of service providers for virtual private cloud services. Recently, Ethernet VPN (EVPN) has been proposed to address many of those concerns and vendors started to deploy EVPN based solutions in DC edge routers. However, manual configuration leads to a time-consuming, error-prone configuration and high operational costs. Automating the EVPN deployment from cloud platforms such as OpenStack enhances both the deployment and flexibility of EVPN Instances (EVIs). This paper proposes a Software Defined Network (SDN) based framework that automates the EVPN deployment and management inside SDN-based DCs using OpenStack and OpenDaylight (ODL). We implemented and extended several modules inside ODL controller to manage and interact with EVIs and an interface to OpenStack that allows the deployment and configuration of EVIs. We conclude with scalability analysis of our solution.

  • 280.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Hernandez Benet, Cristian
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Taheri, Javid
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    SDN helps volume in Big Data2018In: Big Data and Software Defined Networks / [ed] Javid Taheri, London: IET Digital Library, 2018, 1, p. 185-206Chapter in book (Refereed)
    Abstract [en]

    Both Big Data and SDN are described in detail in previous chapters. This chapter investigates how SDN architecture can leverage its unique features to mitigate the challenges of Big Data volume. Accordingly, first, we provide an overview of Big Data volume, its effects on the underlying network, and mention some potential SDN solutions to address the corresponding challenges. Second, we elaborate more on the network-monitoring, traffic-engineering, and fault-tolerant mechanisms which we believe they may help to address the challenges of Big Data volume. Finally, this chapter is concluded with some open issues.

  • 281.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    SDN Enhanced Ethernet VPN for Data Center Interconnect2017In: 2017 IEEE 6th International Conference on Cloud Networking (CloudNet) / [ed] Maga, D, IEEE, 2017, p. 77-82Conference paper (Refereed)
    Abstract [en]

    Ethernet Virtual Private Network (EVPN) is an emerging technology that addresses the networking challenges presented by geo-distributed Data Centers (DCs). One of the major advantages of EVPN over legacy layer 2 VPN solutions is providing All-Active (A-A) mode of operation so that the traffic can truly be multi-homed on Provider Edge (PE) routers. However, A-A mode of operation introduces new challenges. In the case where the Customer Edge (CE) router is multi-homed to one or more PE routers, it is necessary that only one of the PE routers should forward Broadcast, Unknown unicast, and Multicast (BUM) traffic into the DC. The PE router that assumes the primary role for forwarding BUM traffic to the CE device is called the Designated Forwarder (DF). The proposed solution to select the DF in the EVPN standard is based on a distributed algorithm which has a number of drawbacks such as unfairness and intermittent behavior. In this paper, we introduce a Software-Defined Networking (SDN) based architecture for EVPN support, where the SDN controller interacts with EVPN control plane. We demonstrate how our solution mitigates existing problems for DF selection which leads to improved EVPN performance.

  • 282.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Sankar Gopannan, Prem
    Ericsson, USA.
    EVPN/SDN Assisted Live VM Migration between Geo-Distributed Data Centers2018In: 4th IEEE Conference on Network Softwarization (NetSoft), IEEE, 2018, p. 105-113Conference paper (Refereed)
    Abstract [en]

    Live Virtual Machine (VM) migration has significantly improved the flexibility of modern Data Centers (DC). However, seamless live migration of a VM between geo-distributed DCs faces several challenges due to difficulties in preserving the network configuration after the migration paired with a large network convergence time. Although SDN-based approaches can speed up network convergence time, these techniques have two limitations. First, they typically react to the new topology by installing new flow rules once the migration is finished. Second, because the WAN is typically not under SDN control, they result in sub-optimal routing thus severely degrading the network performance once the VM is attached at the new location.

    In this paper, we identify networking challenges for VM migration across geo-distributed DCs. Based on those observations, we design a novel long-haul VM migration scheme that overcomes those limitations. First, instead of reactively restoring connectivity after the migration, our SDN-based approach proactively restores flows across the WAN towards the new location with the help of EVPN and VXLAN overlay technologies. Second, the SDN controller accelerates the network convergence by announcing the migration to other controllers using MP-BGP control plane messages. Finally, the SDN controller resolves the sub-optimal routing problem that arises as a result of migration implementing a distributed anycast gateway. We implement our approach as extensions to the OpenDaylight controller. Our evaluation shows that our approach outperforms existing approaches in reducing the downtime by 400 ms and increasing the application performance up to 12 times.

  • 283.
    Alizadeh Noghani, Kyoomars
    et al.
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Kassler, Andreas
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Taheri, Javid
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    On the Cost-Optimality Trade-off for Service Function Chain Reconfiguration2019Conference paper (Refereed)
    Abstract [en]

    Optimal placement of Virtual Network Functions (VNFs) in virtualized data centers enhances the overall performance of Service Function Chains (SFCs) and decreases the operational costs for mobile network operators. Maintaining an optimal placement of VNFs under changing load requires a dynamic reconfiguration that includes adding or removing VNF instances, changing the resource allocation of VNFs, and re-routing corresponding service flows. However, such reconfiguration may lead to notable service disruptions and impose additional overhead on the VNF infrastructure, especially when reconfiguration entails state or VNF migration. On the other hand, not changing the existing placement may lead to high operational costs. In this paper, we investigate the trade-off between the reconfiguration of SFCs and the optimality of the resulting placement and service flow (re)routing. We model different reconfiguration costs related to the migration of stateful VNFs and solve a joint optimization problem that aims to minimize both the total cost of the VNF placement and the reconfiguration cost necessary for repairing a suboptimal placement. Numerical results show that a small number of reconfiguration operations can significantly reduce the operational cost of the VNF infrastructure; however, too much reconfiguration may not pay off should heavy costs be involved.

  • 284.
    Aljinovic, Andrea Aglic
    et al.
    University of Zagreb, Croatia.
    Peric, Ivan
    University of Zagreb, Croatia.
    Persson, Lars-Erik
    Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
    Josip Pecaric- and his life in mathematics and politics2019In: Mathematical Inequalities & Applications, ISSN 1331-4343, E-ISSN 1848-9966, Vol. 22, no 4, p. 1067-1080Article in journal (Refereed)
    Abstract [en]

    It is impossible in limited number of pages to give a fair picture of such a remarkable man, great mathematician and human being as Josip Pecaric. Our intention is instead to complement the picture of him in various ways. We hope that our paper will give also someflavor of Josip as family man, fighter, supervisor,international authority, author (also in other subjects than mathematics), fan of the Croatian football team, and not only as his obvious role as our King of Inequalities.

  • 285. All, Rainar
    et al.
    Harrami, Omar
    Postgård, Ulrika
    Strömgren, Mattias
    Karlstad University, Faculty of Social and Life Sciences, Department of Health and Environmental Sciences.
    Olyckor, riskanalyser och säkerhetsarbete: Några olika perspektiv inom Räddningsverket2006Other (Other (popular science, discussion, etc.))
    Abstract [sv]

    Sammanfattning

    Syftet med denna kartläggning har varit att ge en nulägesbild över hur riskanalyser, riskbedömningar och riskvärderingar sker i Räddningsverkets arbete med skydd mot olyckor. Ett syfte har också varit att beskriva de olika strategier för säkerhetsarbete som tillämpas i myndigheten.



    Kartläggningen har utförts genom gruppintervjuer under perioden oktober 2004 mars 2005 och har följts upp med hjälp av två seminarier i november 2005. Analysgruppen har bestått av medarbetare vid Räddningsverkets sekretariat för forskning och analys.

    Resultaten visar bland annat att:

    - verkets arbete utgår från en kompott av olyckor, skador och händelser, var och en med sin egen logik baserad på tradition, lagstiftning och politisk inriktning

    - arbetet bedrivs utifrån en mångfald av strategier som i många fall inte är produkten av genomtänkta analyser och medvetna val

    - verkets olika roller behöver närmare analyseras och kopplas till tydligare

    strategier och metoder för arbetet med skydd mot olyckor

    - säkerhetsarbete och riskhantering är inte synonyma begrepp i myndigheten

    - det saknas myndighetsgemensamma begreppsdefinitioner inom det kartlagda

    området

    - det råder en brist i myndigheten på djupare diskussioner och reflektioner kring värdegrunder och principer för riskvärdering.



    Rapporten behandlar många olika frågor som på olika sätt är relevanta för Räddningsverkets arbete på kort och lång sikt. I rapporten ges ett tiotal förslag till fortsatt arbete. Några förslag är att:

    - utarbeta en begreppspolicy för myndigheten

    - utarbeta information till privatpersoner som lagenliga skyldigheter inom det olycksförebyggande området

    - satsa på kompetensutveckling internt

    - starta ett utvecklingsarbete inom riskvärdering

    - utveckla analysförmåga för framtidens olycksrisk

    - starta en idéverkstad för framtida säkerhetsarbete



    Kartläggningen ska ligga till grund för fortsatt utvecklingsarbete inom Räddningsverket. Delar av materialet kan också komma att utgöra underlag för

    utveckling av läromedel för verkets utbildningsverksamhet. Rapporten utgör också en möjlig källa för fortsatt forskning och analys inom området

  • 286. Allman, Mark
    et al.
    Avrachenkov, Konstatin
    Ayesta, Urtzi
    Blanton, Josh
    Hurtig, Per
    Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.
    Early Retransmit for TCP and SCTP2008Other (Other (popular science, discussion, etc.))
    Abstract [en]

    This document proposes a new mechanism for TCP and SCTP that can be used to recover lost segments when a connection's congestion window is small. The "Early Retransmit" mechanism allows the transport to reduce, in certain special circumstances, the number of duplicate acknowledgments required to trigger a fast retransmission. This allows the transport to use fast retransmit to recover packet losses that would otherwise require a lengthy retransmission timeout.

  • 287.
    Allvin, Michael
    Sociologiska institutionen, Uppsala universitet.
    Recension av Ola Bergström, Kristina Håkansson, Tommy Isidorsson och Lars Walter, Den nya arbetsmarknaden: Bemanningsbranschens etablering i Sverige (Academia Adacta, Lund 2007).2008In: Arbetsmarknad & Arbetsliv, ISSN 1400-9692, Vol. 14, no 2, p. 71-74Article in journal (Other (popular science, discussion, etc.))
  • 288.
    Allvin, Michael
    et al.
    Uppsala universitet.
    Mellner, Christin
    Stockholms universitet.
    Movitz, Fredrik
    Stockholms universitet.
    Aronsson, Gunnar
    Stockholms universitet.
    Den utbredda flexibiliteten: Ett försök att beräkna förekomsten av lågreglerade arbetsvillkor2012In: Arbetsmarknad & Arbetsliv, ISSN 1400-9692, Vol. 18, no 1, p. 9-24Article in journal (Refereed)
    Abstract [sv]

    Nästan 30 år efter det att begreppet flexibilitet i arbetslivet kom i bruk råder det fortfarande stor osäkerhet om vad begreppet innebär och hur vanligt det egentligen är. I artikeln diskuteras flexibilitet utifrån en representativ studie av den svenska arbetskraften. I studien konstateras att både traditionellt organiserade och helt fria arbeten är relativt ovanliga. Däremot är flexibla arbetsvillkor desto mer vanligt förekommande och spridda i varierande grad bland den svenska arbetskraften.

  • 289.
    Allvin, Michael
    et al.
    Uppsala universitet.
    Movitz, Fredrik
    Stockholms universitet.
    "Självständiga lärosäten": Om de förändrade villkoren för högre utbildning och universitetens normalisering2011In: Arbetsmarknad & Arbetsliv, ISSN 1400-9692, Vol. 17, no 2, p. 59-73Article in journal (Refereed)
    Abstract [sv]

    När den högre utbildningen avregleras får universitet  och högskolor själva bestämma hur de ska organisera sin verksamhet. Det sker även i den övriga västvärlden, liksom i den övriga svenska offentliga sektorn. Frågan är dock vad ett sådant självbestämmande egentligen är värt. Avregleringen lämnar nämligen lärosätena att konkurrera med varandra på en allt snävare och alltmer standardiserad spelplan, vilket i sin tur tvingar dem till långtgående rationaliseringar och prioriteringar.

  • 290.
    Alm, Maria
    Karlstad University, Faculty of Arts and Education, Department of Education.
    Teaching materials and students with mental retardation2008Conference paper (Other (popular science, discussion, etc.))
    Abstract [en]

    Teaching materials and students with mental retardation



    From a socio-cultural perspective, teaching materials can be regarded as mediating tools for transferring culturally based knowledge, norms, values and traditions. While literature on teaching materials in general is substantial, few investigations have been conducted on teaching materials for students with mental retardation.



    In this paper I will present parts of an ongoing project in which this issue is focused. The study includes about twenty students in two training school classes and one class for students with mild mental retardation, covering the grades 7 10 in the compulsory school.



    Teaching materials in this study are defined as cultural tools used in education and serving a pedagogical function in programs for students with mental retardation (särskolan). My preliminary findings indicate predominance for everyday skills in teaching material activities. Reading or mathematical development in teaching material activities are of low priority. The activities often imply dilemmas the teacher have to master.

  • 291.
    Alm, Maria
    et al.
    Karlstad University, Faculty of Arts and Education, Department of Education.
    Berthén, Diana
    Bladini, Kerstin
    Karlstad University, Faculty of Arts and Education, Department of Education.
    Johansson, Iréne
    Komplicerad skolsituation - elever med utvecklingstörning och deras lärare2001Report (Other academic)
  • 292.
    Almang, Jan
    Gothenburg University, Sweden.
    A NOTE ON SHAPES2015In: Journal of Philosophical Research (JPR), ISSN 1053-8364, E-ISSN 2153-7984, Vol. 40, p. 469-471Article in journal (Refereed)
    Abstract [en]

    It has recently been argued that the Special Theory of Relativity entails that shapes are not intrinsic properties of objects. Rather, they are properties an object has only relative to an inertial frame. In this discussion note I argue that this position, while correct, is incomplete. Objects have frame-dependent shapes because they have an intrinsic property that is the same in all inertial frames.

  • 293.
    Almang, Jan
    University of Gothenburg, Sweden.
    Affordances and the Nature of Perceptual Content2008In: International journal of philosophical studies (Print), ISSN 0967-2559, E-ISSN 1466-4542, Vol. 16, no 2, p. 161-177Article in journal (Refereed)
    Abstract [en]

    According to John McDowell, representational perceptual content is conceptual through and through. This paper criticizes this view by claiming that there is a certain kind of representational and non-conceptual perceptual content that is sensitive to bodily skills. After a brief introduction to McDowell's position, Merleau-Ponty's notion of body schema and Gibson's notion of affordance are presented. It is argued that affordances are constitutive of representational perceptual content, and that at least some affordances, the so-called 'conditional affordances', are essentially related to the body schema. This means that the perceptual content depends upon the nature of the body schema. Since the body schema does not pertain to the domain that our conceptual faculties operate upon, it is argued that this kind of perceptual content cannot be conceptual. At least some of that content is representational, yet it cannot feature as non-demonstrative conceptual content. It is argued that if it features as demonstrative conceptual content, it has to be captured by private concepts. Since McDowell's theory does not allow for the existence of a private language, it is concluded that at least some representational perceptual content is non-conceptual.

  • 294.
    Almang, Jan
    Arvika, Sweden.
    An Argument for Shape Internalism2017In: Erkenntnis, ISSN 0165-0106, E-ISSN 1572-8420, Vol. 82, no 4, p. 819-836Article in journal (Refereed)
    Abstract [en]

    This paper is a defense of an internalist view of the perception of shapes. A basic assumption of the paper is that perceptual experiences have certain parts which account both for the phenomenal character associated with perceiving shapes-phenomenal shapes-and for the intentional content presenting shapes-intentional shapes. Internalism about perceptions of shapes is defined as the claim that phenomenal shapes determine the intentional shapes. Externalism is defined as the claim that perceptual experiences represent whatever shape the phenomenal shape reliably tracks. The argument against externalism proceeds in three steps. First, it is argued that phenomenal shapes are modality specific, such that a phenomenal shape that features in a visual perceptual experience cannot feature in a haptic perceptual experience, and vice versa. Second, it is argued that intentional shapes are amodal. Third, it is argued that externalism is incompatible with the fact that phenomenal shapes are modality specific and intentional shapes amodal.

  • 295.
    Almang, Jan
    Gothenburg University, Sweden.
    Perceiving Exploding Tropes2016In: Grazer Philosophische Studien, ISSN 0165-9227, E-ISSN 1875-6735, Vol. 93, no 1, p. 42-62Article in journal (Refereed)
    Abstract [en]

    The topic of this paper is the perception of properties. It is argued that the perception of properties allows for a distinction between the sense of the identity and the sense of the qualitative nature of a property. So, for example, we might perceive a property as being identical over time even though it is presented as more and more determinate. Thus, you might see an object first as red and then as crimson red. In this case, the property is perceived as identical over time, even though the sense of the qualitative nature ( the redness, the crimson redness) of the property is changing. The distinction between the sense of identity and the sense of quality is explicated in terms of perceiving a particular property, a trope, and perceiving it as an instance of a universal. It is subsequently argued that the perceived tropes cannot constitute the phenomenal character of the perceptual experience.

  • 296.
    Almang, Jan
    Gothenburg University, Göteborg, Sweden.
    Perceptual Transparency and Perceptual Constancy2014In: Husserl Studies, ISSN 0167-9848, E-ISSN 1572-8501, Vol. 30, no 1, p. 1-19Article in journal (Refereed)
    Abstract [en]

    A central topic in discussions about qualia concerns their purported transparency. According to transparency theorists, an experience is transparent in the sense that the subject having the experience is aware of nothing but the intended object of the experience. In this paper this notion is criticized for failing to account for the dynamical aspects of perception. A key assumption in the paper is that perceptual content has a certain temporal depth, in the sense that each act of perception can present an object as extended in time and that objects can be perceived as persisting through time. An object that is seen as persisting through time is often seen as constant and unchanging, even though the presentation of it is changing. In this paper it is argued that in order to account for these cases of perceptual constancy, we must distinguish between the awareness of having perceived that an object has a property at a certain point in time, and perceptually intending that it has that property at that point in time. Consequently, we must in at least some instances be aware of something more than the object of the experience. But precisely this distinction is rejected by the transparency theory.

  • 297.
    Almang, Jan
    Gothenburg, University.
    TENSE AS A FEATURE OF PERCEPTUAL CONTENT2014In: Journal of Philosophy, ISSN 0022-362X, E-ISSN 1939-8549, Vol. 111, no 7, p. 361-378Article in journal (Refereed)
  • 298.
    Almang, Jan
    Gothenburg University, Sweden.
    The Causal Self-Referential Theory of Perception Revisited2013In: Dialectica, ISSN 0012-2017, E-ISSN 1746-8361, Vol. 67, no 1, p. 29-53Article in journal (Refereed)
    Abstract [en]

    This is a paper about The Causal Self-Referential Theory of Perception. According to The Causal Self-Referential Theory as developed by above all John Searle and David Woodruff Smith, perceptual content is satisfied by an object only if the object in question has caused the perceptual experience. I argue initially that Searle's account cannot explain the distinction between hallucination and illusion since it requires that the state of affairs that is presented in the perceptual experience must exist in order for the perception to be veridical. Smith's account is interestingly different in that the descriptive content, i.e. the content that presents the perceptual object as having certain properties, does not determine the object of the experience. His account consequently does not require that the state of affairs that is presented in perception exists in order for the perception to have an object. Smith argues instead that perceptual reference is determined by a specific kind of demonstrative content. In this paper it is argued that Smith's account of demonstrative content is too indeterminate and in certain circumstances prescribes the wrong object. It is subsequently argued that the theory of demonstrative content can be modified so as to avoid these consequences. This modification involves deriving the conditions of satisfaction of seeing an object from the conditions of satisfaction of seeing the shape of the object, where the shape of the object is conceived of as a particularized property, what is also called a trope'.

  • 299.
    Almang, Jan
    University West, Trollhättan, Sweden; University of Gothenburg, Gothenburg, Sweden.
    Time, Mode and Perceptual Content2012In: Acta Analytica, ISSN 0353-5150, E-ISSN 1874-6349, Vol. 27, no 4, p. 425-439Article in journal (Refereed)
    Abstract [en]

    Francois Recanati has recently argued that each perceptual state has two distinct kinds of content, complete and explicit content. According to Recanati, the former is a function of the latter and the psychological mode of perception. Furthermore, he has argued that explicit content is temporally neutral and that time-consciousness is a feature of psychological mode. In this paper it is argued, pace Recanati, that explicit content is not temporally neutral. Recanati's position is initially presented. Three desiderata for a theory of time-consciousness are subsequently introduced. It is then argued that a theory locating time-consciousness as a feature of psychological mode will fail to satisfy these desiderata. In the last section the intentionality of memories is discussed. Using the notion of shiftable indexical, it is argued that memories have the same explicit content as perceptions, but that they nevertheless can have different conditions of satisfaction since they are entertained in different modes.

  • 300.
    Almang, Jan
    Gothenburg University, Sweden.
    Two Kinds of Time-Consciousness and Three Kinds of Content2013In: Axiomathes, ISSN 1122-1151, E-ISSN 1572-8390, Vol. 23, no 1, p. 61-80Article in journal (Refereed)
    Abstract [en]

    This paper explores the distinction between perceiving an object as extended in time, and experiencing a sequence of perceptions. I argue that this distinction cannot be adequately described by any present theory of time-consciousness and that in order to solve the puzzle, we need to consider perceptual content as having three distinct constituents: Explicit content, which has a particular phenomenal character, modal content, or the kind of content that is contributed by the psychological mode, and implicit content, which lacks phenomenal character. These notions are then further clarified and related to each other.

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