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2009 6th IEEE Consumer Communications and Networking Conference, CCNC 2009

作者： Li, Xiaochen Cao, Fengming Wu, Dapeng Department of Electrical and Computer Engineering University of Florida Gainesville FL 32611 United States Toshiba Europe Research Telecommunication Lab 32 Queen Square Bristol BS1 4ND United Kingdom

ISBN: (纸本)9781424423095

In this paper, we study the power allocation scheme for a single user, multi-channel system, e.g. orthogonal frequency-division multiplexing (OFDM) systems, under time-variant wireless fading channels. We assume the receiver feeds back perfectly estimated channel state information (CSI) to the transmitter after a processing delay. The objective of the power allocation is to maximize physical (PHY) layer throughput under quality-of-service (QoS) constraint. The QoS measure of our consideration is a triplet of data rate, delay, and delay bound violation probability. A two-step suboptimal power allocation scheme is proposed which addresses the imperfect CSI issue. In the first step, the total transmission power that can be used by one block is determined according to the summation of the channel gains of all the channels. In the second step, the total transmission power is allocated to all the channels. Compared to the optimal power allocation scheme designed for the perfect CSI scenario, the proposed power allocation scheme reduces the computation complexity significantly while achieves comparable performance. ©2009 IEEE.

关键词： Quality of service

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Conversational agents in e-learning

Conversational agents in e-learning

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28th SGAI International Conference on Innovative Techniques and Applications of Artificial Intelligence, AI 2008

作者： Kerry, Alice Ellis, Richard Bull, Susan Electronic Electrical and Computer Engineering University of Birmingham Edgbaston Birmingham B15 2TT United Kingdom Elzware Ltd 70 Mendip Road Bristol BS3 4NY United Kingdom

ISBN: (纸本)9781848822146

This paper discusses the use of natural language or 'conversational' agents in e-learning environments. We describe and contrast the various applications of conversational agent technology represented in the e-learning literature, including tutors, learning companions, language practice and systems to encourage reflection. We offer two more detailed examples of conversational agents, one which provides learning support, and the other support for self-assessment. Issues and challenges for developers of conversational agent systems for e-learning are identified and discussed. © 2009 Springer-Verlag London.

关键词： computer aided instruction

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Active chaos control of a cam-follower impacting system using FPIC Technique

Active chaos control of a cam-follower impacting system usin...

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作者： Taborda, John Alexander Santini, Stefania Di Bernardo, Mario Angulo, Fabiola Department of Electrical and Electronics Engineering and Computer Science Universidad Nacional de Colombia - Sede Manizales Campus la Nubia Manizales Colombia Department of Systems and Computer Science University of Naples Federico II Napoli Italy Bristol Center for Applied Nonlinear Mathematics University of Bristol Bristol BS81TR United Kingdom

ISBN: (纸本)9783902661654

In this paper, we apply a novel active control scheme to suppress chaotic behavior in a cam-follower impacting system using Fixed-Point Inducting Control or FPIC Technique. Namely, the input speed of the cam-follower system is actively controlled in order to reach a single-impact periodic motion. A cam-follower system characterized by a radial cam and a flat-faced follower is used as a representative example. High-order periodic-impact and chaotic motions are controlled varying the input speed of the cam-follower system. Stroboscopic and impact maps are used to select the suitable control parameters under which stable single-impact periodic responses are reached.

关键词： Chaos control

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Active Chaos Control of a Cam-Follower Impacting System using FPIC Technique *

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IFAC Proceedings Volumes 2009年第7期42卷 327-332页

作者： John Alexander Taborda Stefania Santini Mario di Bernardo Fabiola Angulo Department of Electrical and Electronics Engineering and Computer Science Universidad Nacional de Colombia - Sede Manizales Campus La Nubia Manizales Colombia Department of Systems and Computer Science University of Naples Federico II Napoli Italy Department of Systems and Computer Science University of Naples Federico II Napoli Italy Bristol Center for Applied Nonlinear Mathematics University of Bristol Bristol BS81TR UK

关键词： piecewise smooth systems impacting systems cam-follower systems active control chaos control FPIC technique bifurcation theory Control design

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Imaging algorithms for locating damage via in situ ultrasonic sensors

Imaging algorithms for locating damage via in situ ultrasoni...

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作者： Michaels, Jennifer E. Croxford, Anthony J. Wilcox, Paul D. School of Electrical and Computer Engineering Georgia Institute of Technology Atlanta GA 30332-0250 United States Department of Mechanical Engineering University of Bristol Bristol BS8 1TR United Kingdom

ISBN: (纸本)9781424419630

Permanently mounted ultrasonic sensors arranged as a spatially distributed array are being considered for in situ monitoring of the integrity of structural components. Here we consider two imaging algorithms for locating damage based upon changes in received signals. All transducer pairs in the array are considered, with each transducer acting in turn as a transmitter and the remaining transducers as receivers. The first imaging algorithm is based upon spatially distributing the differenced signals between each transducer pair as per expected arrival times for discrete scatterers. The resulting images, which consist of concentric ellipses, are summed over all pairs to form the final image. The second algorithm is based upon the cross correlation between waveforms originating from the same transmitter and received by two different transducers. The cross correlation waveforms, which capture the time difference of arrival between two pairs, are similarly distributed and summed to form the final image via a hyperbolic rather than an elliptical relationship. Results are shown for artificial damage in an aluminum plate. ©2008 IEEE.

关键词： Structural health monitoring

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Side channel analysis of an automotive microprocessor

Side channel analysis of an automotive microprocessor

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IET Irish Signals and Systems Conference, ISSC 2008

作者： Hamilton, M.D. Tunstall, M. Popovici, E.M. Marnane, W.P. Dept. of Microelectronic Engineering University College Cork Cork Ireland Dept. of Computer Science University of Bristol Merchant Venturers Building Woodland Road Bristol BS8 1UB United Kingdom Dept. of Electrical and Electronic Engineering University College Cork Cork Ireland

ISBN: (纸本)9780863419317

Automotive electronics are becoming ever more complex. The quantity and sensitivity of data that is transmitted throughout a car is expected to continue to increase in coming years. On board computers can contain information about the car and dictate how the car behaves. This means that these systems need to be secure to protect the data held within such system so that the behaviour cannot be modified by an unauthorised user. This paper outlines a method for implementing AES encryption over a CAN bus and how such a system could be attacked using correlation power analysis.

关键词： Side channel attack

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A COMPARISON OF TEMPERATURE COMPENSATION METHODS FOR GUIDED WAVE STRUCTURAL HEALTH MONITORING

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AIP Conference Proceedings 2008年第1期975卷 1453-1460页

作者： P. D. Wilcox A. J. Croxford J. E. Michaels Y. Lu B. W. Drinkwater aDepartment of Mechanical Engineering University of Bristol Bristol BS8 1TR UK bSchool of Electrical and Computer Engineering Georgia Institute of Technology Atlanta Georgia 30332‐0250 USA

The sensitivity to damage achievable by guided wave structural health monitoring systems is limited by the repeatability of recorded signals under normal operating conditions. Direct subtraction of reference signals leads to unacceptably high post‐subtraction noise in the presence of modest temperature changes due to variations in reflections from benign structural features, hence temperature compensation is necessary. In this paper, various numerical compensation strategies are investigated. It is concluded that a combination of stretching and translating time‐traces provides reasonable compensation performance for modest temperature changes.

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Fault injection platform for block ciphers

Fault injection platform for block ciphers

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IET Irish Signals and Systems Conference, ISSC 2008

作者： Baldwin, B. Popovici, E.M. Tunstall, M. Marnane, I.P. Claude Shannon Institute for Discrete Mathematics Coding and Cryptography Dept. of Electrical and Electronic Engineering University College Cork Cork Ireland Claude Shannon Institute for Discrete Mathematics Coding and Cryptography Dept. of Microelectronic Engineering University College Cork Cork Ireland Dept. of Computer Science University of Bristol Merchant Venturers Building Woodland Road Bristol BS8 1UB United Kingdom

ISBN: (纸本)9780863419317

Block ciphers are typically resistant to direct attacks, such as an exhaustive key search or cryptanalysis, all of which require too many resources to achieve an efficient attack. Many block ciphers are examined for their resistance to less direct attacks that target a given implementation. Of these attacks, fault attacks are amongst the most effective at retrieving information on secret key, and require specific countermeasures to be included in an implementation. In this paper we describe a simple platform for the study of fault injection and analysis in the context of fault attacks block ciphers based on a Feistel structure (e.g. DES). We show that an attacker who can successfully inject faults into a block cipher can reduce the complexity of an attack to derive the secret key. We also present a novel version of the attack than can be applied to Triple-DES by independently injecting faults in the second and third instantiations of DES involved in a Triple- DES computation.

关键词： Side channel attack

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Deterministic optical quantum computer using photonic modules

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Physical Review A 2008年第3期78卷 032318-032318页

作者： Ashley M. Stephens Zachary W. E. Evans Simon J. Devitt Andrew D. Greentree Austin G. Fowler William J. Munro Jeremy L. O’Brien Kae Nemoto Lloyd C. L. Hollenberg Centre for Quantum Computer Technology The University of Melbourne Victoria 3010 Australia National Institute for Informatics 2-1-2 Hitotsubashi Chiyoda-ku Tokyo 101-8430 Japan Institute for Quantum Computing University of Waterloo Waterloo Ontario Canada N2L 3G1 Hewlett-Packard Laboratories Filton Road Stoke Gifford Bristol BS34 8QZ United Kingdom Centre for Quantum Photonics H. H. Wills Physics Laboratory and Department of Electrical and Electronic Engineering University of Bristol Merchant Venturers Building Woodland Road Bristol BS8 1UB United Kingdom

The optical quantum computer is one of the few experimental systems to have demonstrated small scale quantum information processing. Making use of cavity quantum electrodynamics approaches to operator measurements, we detail an optical network for the deterministic preparation of arbitrarily large two-dimensional cluster states. We show that this network can form the basis of a large scale deterministic optical quantum computer that can be fabricated entirely on chip.

关键词： Quantum optics

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Entanglement-enhanced quantum key distribution

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Physical Review A 2008年第3期78卷 032314-032314页

作者： Olli Ahonen Mikko Möttönen Jeremy L. O’Brien Department of Engineering Physics/COMP Helsinki University of Technology P. O. Box 5100 FI-02015 TKK Finland Australian Research Council Centre of Excellence for Quantum Computer Technology The University of New South Wales Sydney New South Wales 2052 Australia Low Temperature Laboratory Helsinki University of Technology P. O. Box 3500 FI-02015 TKK Finland Centre for Quantum Photonics H. H. Wills Physics Laboratory & Department of Electrical and Electronic Engineering University of Bristol Merchant Venturers Building Woodland Road Bristol BS8 1UB United Kingdom

We present and analyze a quantum key distribution protocol based on sending entangled N-qubit states instead of single-qubit ones as in the trail-blazing scheme by Bennett and Brassard 1984 (BB84). Since the qubits are sent and acknowledged individually, an eavesdropper is limited to accessing them one by one. In an intercept-resend attack, this fundamental restriction allows one to make the eavesdropper’s information on the transmitted key vanish if even one of the qubits is not intercepted. The implied upper bound 1∕(2N) for this information is further shown not to be the lowest, as the information can be reduced to less than 30% of that in the BB84 scheme in the case N=2. In general, the protocol is at least as secure as BB84.

关键词： Quantum cryptography

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