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  • Journal article
    Narendra KS, Shorten R, 2010,

    Hurwitz Stability of Metzler Matrices

    , IEEE TRANSACTIONS ON AUTOMATIC CONTROL, Vol: 55, Pages: 1484-1487, ISSN: 0018-9286
  • Journal article
    Gargiulo G, Calvo RA, Bifulco P, Cesarelli M, Jin C, Mohamed A, van Schaik Aet al., 2010,

    A new EEG recording system for passive dry electrodes

    , CLINICAL NEUROPHYSIOLOGY, Vol: 121, Pages: 686-693, ISSN: 1388-2457
  • Conference paper
    Porat T, Oron-Gilad T, Silbiger J, Rottem-Hovev Met al., 2010,

    'Castling Rays' a Decision Support Tool for UAV-Switching Tasks

    , CHI’ 2010 Conference Proceedings
  • Journal article
    Cope B, Cheung PYK, Luk W, Howes Let al., 2010,

    Performance comparison of graphics processors to reconfigurable logic: a case study

    , IEEE Transactions on Computers, Vol: 54, Pages: 433-448, ISSN: 0018-9340

    A systematic approach to the comparison of the graphics processor (GPU) and reconfigurable logic is defined in terms of three throughput drivers. The approach is applied to five case study algorithms, characterized by their arithmetic complexity, memory access requirements, and data dependence, and two target devices: the nVidia GeForce 7900 GTX GPU and a Xilinx Virtex-4 field programmable gate array (FPGA). Two orders of magnitude speedup, over a general-purpose processor, is observed for each device for arithmetic intensive algorithms. An FPGA is superior, over a GPU, for algorithms requiring large numbers of regular memory accesses, while the GPU is superior for algorithms with variable data reuse. In the presence of data dependence, the implementation of a customized data path in an FPGA exceeds GPU performance by up to eight times. The trends of the analysis to newer and future technologies are analyzed.
  • Journal article
    Giabardo P, Zugno M, Pinson P, Madsen Het al., 2010,

    Feedback, competition and stochasticity in a day ahead electricity market

    , Energy Economics, Vol: 32, Pages: 292-301, ISSN: 0140-9883

    Major recent changes in electricity markets relate to the process for their deregulation, along with increasing participation of renewable (stochastic) generation e.g. wind power. Our general objective is to model how feedback, competition and stochasticity (on the production side) interact in electricity markets, and eventually assess what their effects are on both the participants and the society. For this, day ahead electricity markets are modeled as dynamic closed loop systems, in which the feedback signal is the market price. In parallel, the Cournot competition model is considered. Mixed portfolios with significant share of renewable energy are based on stochastic threshold cost functions. Regarding trading strategies, it is assumed that generators are looking at optimizing their individual profits. The point of view of the society is addressed by analyzing market behavior and stability. The performed simulations show the beneficial effects of employing long term bidding strategies for both generators and society. Sensitivity analyses are performed in order to evaluate the effects of demand elasticity. It is shown that increase in demand elasticity reduces the possibility for the generators to exploit their market power. Furthermore, the results suggest that introduction of wind power generation in the market is beneficial both for the generators and the society. © 2009 Elsevier B.V. All rights reserved.
  • Journal article
    Jónsson T, Pinson P, Madsen H, 2010,

    On the market impact of wind energy forecasts

    , Energy Economics, Vol: 32, Pages: 313-320, ISSN: 0140-9883

    This paper presents an analysis of how day-ahead electricity spot prices are affected by day-ahead wind power forecasts. Demonstration of this relationship is given as a test case for the Western Danish price area of the Nord Pool's Elspot market. Impact on the average price behaviour is investigated as well as that on the distributional properties of the price. By using a non-parametric regression model to assess the effects of wind power forecasts on the average behaviour, the non-linearities and time variations in the relationship are captured well and the effects are shown to be quite substantial. Furthermore, by evaluating the distributional properties of the spot prices under different scenarios, the impact of the wind power forecasts on the price distribution is proved to be considerable. The conditional price distribution is moreover shown to be non-Gaussian. This implies that forecasting models for electricity spot prices for which parameters are estimated by a least squares techniques will not have Gaussian residuals. Hence the widespread assumption of Gaussian residuals from electricity spot price models is shown to be inadequate for these model types. The revealed effects are likely to be observable and qualitatively similar in other day-ahead electricity markets significantly penetrated by wind power. © 2009 Elsevier B.V. All rights reserved.
  • Journal article
    Bouganis C, Pournara I, Cheung PYK, 2010,

    Exploration of Heterogeneous FPGAs for Mapping Linear Projection Designs

    , IEEE Transactions on Very Large Scale Integration (VLSI) Systems, Vol: 18
  • Journal article
    Jamieson P, Becker T, Cheung PYK, Luk W, Rissa T, Pitkanen Tet al., 2010,

    Benchmarking and evaluating reconfigurable architectures targeting the mobile domain

    , ACM Transactions on Design Automation of Electronic Systems (TODAES), Vol: 15

    We present the GroundHog 2009 benchmarking suite that evaluates the power consumption of reconfigurable technology for applications targeting the mobile computing domain. This benchmark suite includes seven designs; one design targets fine-grained FPGA fabrics allowing for quick state-of-the-art evaluation, and six designs are specified at a high level allowing them to target a range of existing and future reconfigurable technologies. Each of the six designs can be stimulated with the help of synthetically generated input stimuli created by an open-source tool included in the downloadable suite. Another tool is included to help verify the correctness of each implemented design. To demonstrate the potential of this benchmark suite, we evaluate the power consumption of two modern industrial FPGAs targeting the mobile domain. Also, we show how an academic FPGA framework, VPR 5.0, that has been updated for power estimates can be used to estimates the power consumption of different FPGA architectures and an open-source CAD flow mapping to these architectures.
  • Journal article
    Mak T, Sedcole P, Cheung PYK, Luk Wet al., 2010,

    Wave-pipelined intra-chip signaling for on-FPGA communications

    , Integration, the VLSI Journal, Vol: 43, Pages: 188-201

    On-FPGA communication is becoming more problematic as the long interconnection performance is deteriorating in technology scaling. In this paper, we address this issue by proposing a novel wave-pipelined signaling scheme to achieve substantial throughput improvement in FPGAs. A new analytical model capturing the electrical characteristics in FPGA interconnects is presented. Based on the model, throughput and power consumption of a wave-pipelined link have been derived analytically and compared to the conventional synchronous links. Two circuit designs are proposed to realize wave-pipelined link using FPGA fabrics. The proposed approaches are also compared with conventional synchronous and asynchronous pipelining techniques. It is shown that the wave-pipelined approach can achieve up to 5.7 times improvement in throughput and 13% improvement in power consumption versus conventional delay-based on-chip communication schemes. Also, trade-offs between power, throughput and area consumption between the proposed and conventional designs are studied. The wave-pipelining approach provides a new alternative for on-FPGA communications and can potentially become a promising solution to mitigate the future interconnect scaling challenge.
  • Journal article
    Thordarson FO, Madsen H, Nielsen HA, Pinson Pet al., 2010,

    Conditional weighted combination of wind power forecasts

    , Wind Energy, Vol: 13, Pages: 751-763, ISSN: 1095-4244

    The classical regression model for combined forecasting was reformulated in order to impose restrictions on the combination weights. This restricted linear combination model was then extended to the case where the weights were allowed to be a non-parametric function of some meteorological variables, yielding the so-called conditional weighted combination method. The weight functions are estimated with local regression techniques. The conditional weighted combination method was applied to a test case of a wind farm over a period of 10 months. Various combinations of two forecasts out of the three available ones were considered. Analysis of the data suggested that meteorological forecasts of air density and turbulent kinetic energy may be considered as relevant external variables in the combination scheme. A performance comparison showed that the conditional weighted combination method introduced in this paper outperformed the least-squares combination method for almost all prediction horizons, especially for larger ones. This indicates that further developments based on conditional combination methods, including adaptivity of the weight functions estimation, may significantly enhance forecast accuracy and dampen the risk of large prediction errors. Copyright © 2010 John Wiley & Sons, Ltd.
  • Conference paper
    Lee JM, Cho SH, Kim SD, Calvo RAet al., 2010,

    An improvement of flocking algorithm based on spatial subdivision method

    , Pages: 26-30

    In this paper we present a noble flocking algorithm that yields an improvement in the execution time over the existing method based on the spatial subdivision method. One of characteristics in flocking behaviors is that two agents may share many common neighbors if they are spatially close to each other. The proposed algorithm improves the existing algorithm of the flocking behaviors by computing simultaneously the k-nearest neighbors of agents if they share many common neighbors. The performance of the proposed algorithm was compared with other method. The results of the comparisons show that the proposed algorithm outperforms the recently proposed flocking algorithm by about 31% with respect to the execution time. © 2010 The University of Wolverhampton.
  • Journal article
    Gargiulo G, Bifulco P, Cesarelli M, Ruffo M, Romano M, Calvo RA, Jin C, van Schaik Aet al., 2010,

    An ultra-high input impedance ECG amplifier for long-term monitoring of athletes

    , Medical Devices: Evidence and Research, Vol: 3, Pages: 1-9

    We present a new, low-power electrocardiogram (ECG) recording system with an ultra-high input impedance that enables the use of long-lasting, dry electrodes. The system incorporates a low-power Bluetooth module for wireless connectivity and is designed to be suitable for long-term monitoring during daily activities. The new system using dry electrodes was compared with a clinically approved ECG reference system using gelled Ag/AgCl electrodes and performance was found to be equivalent. In addition, the system was used to monitor an athlete during several physical tasks, and a good quality ECG was obtained in all cases, including when the athlete was totally submerged in fresh water. © 2010 Gargiulo et al.
  • Conference paper
    Picinali L, Prosser S, 2010,

    Monolateral and bilateral fitting with different hearing aids directional configurations

    , Pages: 726-734

    Hearing aid bilateral fitting in hearing impaired subjects raises some problems concerning the interaction of the perceptual binaural properties with the directional characteristics of the device. This experiment aims to establish whether and to which extent in a sample of 20 normally hearing subjects the binaural changes in the speech-to-noise level ratio (s/n), caused by different symmetrical and asymmetrical microphone configurations, and different positions of the speech signal (frontal or lateral), could alter the performances of the speech recognition in noise. Speech Reception Threshold (SRT) in noise (simulated through an Ambisonic virtual soundfield) has been measured monolaterally and bilaterally in order to properly investigate the role of the binaural interaction in the perception of reproduced signals.
  • Journal article
    Vincent C, Giebel G, Pinson P, Madsen Het al., 2010,

    Resolving nonstationary spectral information in wind speed time series using the hilbert-huang transform

    , Journal of Applied Meteorology and Climatology, Vol: 49, Pages: 253-267, ISSN: 1558-8424

    This work is motivated by the observation that large-amplitude wind fluctuations on temporal scales of 1-10 h present challenges for the power management of large offshore wind farms. Wind fluctuations on these scales are analyzed at a meteorological measurement mast in the Danish North Sea using a 4-yr time series of 10-min wind speed observations. An adaptive spectral analysis method called the Hilbert-Huang transform is chosen for the analysis, because the nonstationarity of time series of wind speed observations means that they are not well described by a global spectral analysis method such as the Fourier transform. The Hilbert-Huang transform is a local method based on a nonparametric and empirical decomposition of the data followed by calculation of instantaneous amplitudes and frequencies using the Hilbert transform. The Hilbert-Huang transformed 4-yr time series is averaged and summarized to show climatological patterns in the relationship between wind variability and time of day. First, by integrating the Hilbert spectrum along the frequency axis, a scalar time series representing the total variability within a given frequency range is calculated. Second, by calculating average spectra conditional to time of day, the time axis of the Hilbert spectrum is "remapped" to show climatological patterns. Third, the daily patterns in wind variability and wind speed are compared for the four seasons of the year. It is found that the most intense wind variability occurs in autumn even though the strongest observed wind speeds occur in winter. © 2010 American Meteorological Society.
  • Journal article
    Pinson P, McSharry P, Madsen H, 2010,

    Reliability diagrams for non-parametric density forecasts of continuous variables: Accounting for serial correlation

    , Quarterly Journal of the Royal Meteorological Society, Vol: 136, Pages: 77-90, ISSN: 0035-9009

    Reliability is seen as a primary requirement when verifying probabilistic forecasts, since a lack of reliability would introduce a systematic bias in subsequent decision-making. Reliability diagrams comprise popular and practical diagnostic tools for the reliability evaluation of density forecasts of continuous variables. Such diagrams relate to the assessment of the unconditional calibration of probabilistic forecasts. A reason for their appeal is that deviations from perfect reliability can be visually assessed based on deviations from the diagonal. Deviations from the diagonal may, however, be caused by both sampling effects and serial correlation in the forecast-verification pairs. We build on a recent proposal, consisting of associating reliability diagrams with consistency bars that would reflect the deviations from the diagonal that are potentially observable even if density forecasts are perfectly reliable. Our consistency bars, however, reflect potential deviations originating from the combined effects of limited counting statistics and serial correlation in the forecast-verification pairs. They are generated based on an original surrogate consistency resampling method. Its ability to provide consistency bars with a significantly better coverage against the independent and identically distributed (i.i.d.) resampling alternative is shown from simulations. Finally, a practical example of the reliability assessment of non-parametric density forecasts of short-term wind-power generation is given. © 2010 Royal Meteorological Society.
  • Journal article
    Myant C, Spikes HA, Stokes JR, 2010,

    Influence of load and elastic properties on the rolling and sliding friction of lubricated compliant contacts

    , TRIBOLOGY INTERNATIONAL, Vol: 43, Pages: 55-63, ISSN: 0301-679X
  • Journal article
    Calvo RA, D'Mello S, 2010,

    Affect Detection: An Interdisciplinary Review of Models, Methods, and Their Applications

    , IEEE TRANSACTIONS ON AFFECTIVE COMPUTING, Vol: 1, Pages: 18-37, ISSN: 1949-3045
  • Journal article
    Becker T, Jamieson P, Luk W, Cheung PYK, Rissa Tet al., 2010,

    Power characterisation for fine-grain reconfigurable fabrics

    , International Journal of Reconfigurable Computing, Vol: 2010

    This paper proposes a benchmarking methodology for characterising the power consumption of the fine-grain fabric in reconfigurable architectures. This methodology is part of the GroundHog 2009 power benchmarking suite. It covers active and inactive power as well as advanced low-power modes. A method based on random number generators is adopted for comparing activity modes. We illustrate our approach using five field-programmable gate arrays (FPGAs) that span a range of process technologies: Xilinx Virtex-II Pro, Spartan-3E, Spartan-3AN, Virtex-5, and Silicon Blue iCE65. We find that, despite improvements through process technology and low-power modes, current devices need further improvements to be sufficiently power efficient for mobile applications. The Silicon Blue device demonstrates that performance can be traded off to achieve lower leakage.
  • Journal article
    Siriwardena KAP, Fernando LCP, Nanayakkara N, Perera KFG, Kumara ADNT, Nanayakkara Tet al., 2010,

    Portable acoustic device for detection of coconut palms infested by <i>Rynchophorus ferrugineus</i> (Coleoptera: Curculionidae)

    , CROP PROTECTION, Vol: 29, Pages: 25-29, ISSN: 0261-2194
  • Conference paper
    Griggs WM, Anderson BDO, Shorten RN, 2010,

    Determining "Mixedness" and an Application of Finite-Gain Stability Results to "Mixed" System Interconnections

    , 49th IEEE Conference on Decision and Control (CDC), Publisher: IEEE, Pages: 714-719, ISSN: 0743-1546
  • Conference paper
    Ghajari M, Peldschus S, Galvanetto U, Asgharpour Z, Iannucci Let al., 2010,

    Influence of the body on head rotational acceleration in motorcycle helmet oblique impact tests

    , IRCOBI
  • Conference paper
    Pour PA, Hussain MS, AlZoubi O, D'Mello S, Calvo RAet al., 2010,

    The Impact of System Feedback on Learners' Affective and Physiological States

    , 10th International Conference on Intelligent Tutoring Systems, Publisher: SPRINGER-VERLAG BERLIN, Pages: 264-+, ISSN: 0302-9743
  • Conference paper
    Derntl M, Calvo RA, 2010,

    Embedding Educational Design Pattern Frameworks into Learning Management Systems

    , 1st International Conference on Reforming Education, Quality of Teaching and Technology-Enhanced Learning: Learning Technologies, Quality of Education, Educational Systems, Evaluation, Pedagogies, Publisher: SPRINGER-VERLAG BERLIN, Pages: 439-+, ISSN: 1865-0929
  • Journal article
    Aurisicchio M, Bracewell RH, Wallace KM, 2010,

    Understanding how the information requests of aerospace engineering designers influence information seeking behaviour

    , Journal of Engineering Design, Vol: Vol.21, Pages: 707-730

    Engineering design activities rely heavily on the richness of knowledge and information available. In order to progress their tasks, designers undertake numerous searches to answer their information requests. A review of the literature on information seeking (IS) found that the role of the types of information request on source selection has been little investigated compared with that of the source itself, the seeker, the seeker–source relationship and the work context. This paper describes the empirical research that was carried out in collaboration with the aerospace group of a major power systems company to understand the relationship between information searches and information requests raised by designers involved in individual design tasks. The empirical part of the research consisted of participating in a design activity undertaken within the collaborating company and in conducting analytical studies with its designers. Two large data sets were gathered using a diary study and observations with shadowing. Based on the literature review and empirical research, a framework to describe how engineering designers access information was developed. The context of an information request, the request itself and the associated search were characterised through three groups of categories. Designers were found to raise requests to acquire information and to process information. The main sources used to answer these requests were colleagues, databases and drawings. In examining how sources are used, the research confirmed that designers generally prefer to source knowledge and information through informal interactions with their colleagues and demonstrated that colleagues are more often consulted to answer the requests to process information and documentary sources to answer the requests to acquire information. The results on the use of the media to communicate with colleagues indicated that face-to-face interactions are preferred to answer the requests to process i
  • Conference paper
    Stanojevic R, Shorten R, 2010,

    Distributed dynamic speed scaling

    , Conference on IEEE INFOCOM, Publisher: IEEE, ISSN: 0743-166X
  • Conference paper
    Sajja S, Solmaz S, Shorten R, Corless Met al., 2010,

    Preservation of Common Quadratic Lyapunov Functions and Pade Approximations

    , 49th IEEE Conference on Decision and Control (CDC), Publisher: IEEE, Pages: 7334-7338, ISSN: 0743-1546
  • Conference paper
    Zappavigna A, Colaneri P, Geromel JC, Shorten Ret al., 2010,

    Dwell Time Analysis for Continuous-Time Switched Linear Positive Systems

    , American Control Conference, Publisher: IEEE, Pages: 6256-6261, ISSN: 0743-1619
  • Conference paper
    Shorten R, Narendra KS, 2010,

    On The Diagonal Stability of a Class of Almost Positive Switched Systems

    , American Control Conference, Publisher: IEEE, Pages: 6250-6255, ISSN: 0743-1619
  • Journal article
    Zeheb E, Shorten R, Sajja SSK, 2010,

    Strict positive realness of descriptor systems in state space

    , INTERNATIONAL JOURNAL OF CONTROL, Vol: 83, Pages: 1799-1809, ISSN: 0020-7179
  • Book chapter
    Gargiulo G, Bifulco P, Calvo RA, Cesarelli M, Jin C, McEwan A, van Schaik Aet al., 2010,

    Non-invasive Electronic Biosensor Circuits and Systems

    , INTELLIGENT AND BIOSENSORS, Editors: Somerset, Publisher: INTECH EUROPE, Pages: 123-146

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