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    A High Frame Rate Hybrid X-Ray Image Sensor

    Ercan, A. ; Tate, M.W. ; Gruner, S.M.
    Sensors Journal, IEEE

    Volume: 15 , Issue: 3
    DOI: 10.1109/JSEN.2014.2359153
    Publication Year: 2015 , Page(s): 1523 - 1531

    IEEE Journals & Magazines

    This paper describes a solid-state image sensor for high-speed X-ray imaging. The sensor is made up of a light sensitive detector layer bump-bonded to a readout integrated circuit (ROIC). The detector layer is high resistivity n-type silicon and is fully depleted in operation. The p-implanted islands are used to define pixel regions with 100-μm × 100-μm area. The detector layer contains 852 × 209 pixels indium bump-bonded to four identical CMOS ROICs. Each ROIC contains 213 × 209 pixels and is fabricated using a 0.25-μm CMOS process. The ROIC utilizes a capacitive transimpedance amplifier-type front-end coupled to a switched capacitor analog memory. This architecture allows storage of eight frames for high-speed burst imaging of up to a million frames per second, followed by a slower multiplexed readout. Details of the sensor design and operation are presented together with characterization results. View full abstract»

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    Fiducial Facial Point Extraction Using a Novel Projective Invariant

    Fan, X. ; Wang, H. ; Luo, Z. ; Li, Y. ; Hu, W. ; Luo, D.
    Image Processing, IEEE Transactions on

    Volume: 24 , Issue: 3
    DOI: 10.1109/TIP.2015.2390976
    Publication Year: 2015 , Page(s): 1164 - 1177

    IEEE Journals & Magazines

    Multimedia

    Automatic extraction of fiducial facial points is one of the key steps to face tracking, recognition, and animation. Great facial variations, especially pose or viewpoint changes, typically degrade the performance of classical methods. Recent learning or regression-based approaches highly rely on the availability of a training set that covers facial variations as wide as possible. In this paper, we introduce and extend a novel projective invariant, named the characteristic number (CN), which unifies the collinearity, cross ratio, and geometrical characteristics given by more (6) points. We derive strong shape priors from CN statistics on a moderate size (515) of frontal upright faces in order to characterize the intrinsic geometries shared by human faces. We combine these shape priors with simple appearance based constraints, e.g., texture, edge, and corner, into a quadratic optimization. Thereafter, the solution to facial point extraction can be found by the standard gradient descent. The inclusion of these shape priors renders the robustness to pose changes owing to their invariance to projective transformations. Extensive experiments on the Labeled Faces in the Wild, Labeled Face Parts in the Wild and Helen database, and cross-set faces with various changes demonstrate the effectiveness of the CN-based shape priors compared with the state of the art. View full abstract»

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    Noncontact Power Meter

    Donnal, J.S. ; Leeb, S.B.
    Sensors Journal, IEEE

    Volume: 15 , Issue: 2
    DOI: 10.1109/JSEN.2014.2359619
    Publication Year: 2015 , Page(s): 1161 - 1169

    IEEE Journals & Magazines

    Energy metering is increasingly important in today's power grid. With real-time power meters, utilities can efficiently incorporate renewables and consumers can tailor their demand accordingly. Several high-profile attempts at delivering realtime energy analytics to users, including Google Power Meter and Microsoft Hohm, have essentially failed because of a lack of sufficient richness and access to data at adequate bandwidth for reasonable cost. High performance meters can provide adequate data, but require custom installation at prohibitive expense, e.g., requiring an electrician for installation. This paper presents hardware and signal processing algorithms that enable high bandwidth measurements of voltage, current, harmonics, and power on an aggregate electrical service (such as a residential powerline) for nonintrusive analysis with hardware that requires no special skill or safety considerations for installation. View full abstract»

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    Comparison Between Different Design Topologies for Multi-Megawatt Direct Drive Wind Generators Using Improved Second Generation High Temperature Superconductors

    Karmaker, H. ; Ho, M. ; Kulkarni, D.
    Applied Superconductivity, IEEE Transactions on

    Volume: 25 , Issue: 3 , Part: 2
    DOI: 10.1109/TASC.2014.2375872
    Publication Year: 2015 , Article#: 5201605

    IEEE Journals & Magazines

    Various design topologies were investigated to study the weights and costs for a direct drive wind turbine generator using improved second generation (2G) YBCO high temperature superconductors (HTS). Five different design topologies using combinations of air core, iron core, salient and non-salient configurations for both stator and rotor were considered for a generator with the nominal rating of 10 MW, 8 RPM and 3300 V. The main objective of the investigation was to minimize the HTS quantities and the reduction of total cost to achieve the same rating performance. The electromagnetic design was performed using transient finite element modeling including the improved HTS conductor characteristic properties. The mechanical design includes the support structures for both full load operation and sudden three-phase terminal fault conditions which can cause severe stresses. View full abstract»

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    Multi-Task Pose-Invariant Face Recognition

    Ding, C. ; Xu, C. ; Tao, D.
    Image Processing, IEEE Transactions on

    Volume: 24 , Issue: 3
    DOI: 10.1109/TIP.2015.2390959
    Publication Year: 2015 , Page(s): 980 - 993

    IEEE Journals & Magazines

    Face images captured in unconstrained environments usually contain significant pose variation, which dramatically degrades the performance of algorithms designed to recognize frontal faces. This paper proposes a novel face identification framework capable of handling the full range of pose variations within ±90° of yaw. The proposed framework first transforms the original pose-invariant face recognition problem into a partial frontal face recognition problem. A robust patch-based face representation scheme is then developed to represent the synthesized partial frontal faces. For each patch, a transformation dictionary is learnt under the proposed multi-task learning scheme. The transformation dictionary transforms the features of different poses into a discriminative subspace. Finally, face matching is performed at patch level rather than at the holistic level. Extensive and systematic experimentation on FERET, CMU-PIE, and Multi-PIE databases shows that the proposed method consistently outperforms single-task-based baselines as well as state-of-the-art methods for the pose problem. We further extend the proposed algorithm for the unconstrained face verification problem and achieve top-level performance on the challenging LFW data set. View full abstract»

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    Modeling the Irradiance and Temperature Dependence of Photovoltaic Modules in PVsyst

    Sauer, K.J. ; Roessler, T. ; Hansen, C.W.
    Photovoltaics, IEEE Journal of

    Volume: 5 , Issue: 1
    DOI: 10.1109/JPHOTOV.2014.2364133
    Publication Year: 2015 , Page(s): 152 - 158

    IEEE Journals & Magazines

    In order to reliably simulate the energy yield of photovoltaic (PV) systems, it is necessary to have an accurate model of how the PV modules perform with respect to irradiance and cell temperature. Building on a previous study that addresses the irradiance dependence, two approaches to fit the temperature dependence of module power in PVsyst have been developed and are applied here to recent multi-irradiance and temperature data for a standard Yingli Solar PV module type. The results demonstrate that it is possible to match the measured irradiance and temperature dependence of PV modules in PVsyst. Improvements in energy yield prediction using the optimized models relative to the PVsyst standard model are considered significant for decisions about project financing. View full abstract»

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    H^{\infty } Controller Design for Preview and Delayed Systems

    Kojima, A.
    Automatic Control, IEEE Transactions on

    Volume: 60 , Issue: 2
    DOI: 10.1109/TAC.2014.2354911
    Publication Year: 2015 , Page(s): 404 - 419

    IEEE Journals & Magazines

    The H∞ control problem of general preview/delayed systems is solved using analytic solutions of the corresponding operator Riccati equations. The solution to the problem can be applied to a broad range of input/output delayed systems and enables the handling of preview/delayed control problems. The solvability condition is characterized by the roots of the transcendental equations and the control law for the general problem is given based on a predictive compensation with an integro-differential observer. Some interpretations of typical control problems are presented based on the solvability condition and the resulting control law. View full abstract»

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    Fiber Optic Refractometer Based on Leaky-Mode Interference of Bent Fiber

    Xinpu Zhang ; Wei Peng
    Photonics Technology Letters, IEEE

    Volume: 27 , Issue: 1
    DOI: 10.1109/LPT.2014.2359227
    Publication Year: 2015 , Page(s): 11 - 14

    IEEE Journals & Magazines

    In this letter, we present a novel fiber-optic Mach-Zehnder interferometer based on leaky-mode generation from fiber bending and experimentally demonstrate it that is used as a fiber-optic refractometer. The interferometer is simply constructed using a standard single-mode fiber with two fiber bending regions connected by a section of straight fiber. The phase difference is from the optical path difference between the core mode and leaky modes from the designed bending fiber structure. Refractive index (RI) sensors with different parameters have been fabricated and tested in NaCl solutions with different RIs in the range of 1.3288-1.3696, and a maximum RI sensitivity of -204-nm/RIU (refractive index unit) is achieved on a sensor with a 4-cm straight fiber length and 5-mm bending radius. Experimental results have confirmed that there are two dominant cladding modes interfering with the core mode. The RI sensitivities of the sensors with a uniform bending radius are independent of the straight fiber length; as a result, precise control of the fiber length is not required, which makes the sensor production cost-effective. View full abstract»

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    Low-Complexity Hardware Design for Fast Solving LSPs With Coordinated Polynomial Solution

    Chang, C. ; Chen, B. ; Chen, S. ; Wang, J. ; Chiu, Y.
    Very Large Scale Integration (VLSI) Systems, IEEE Transactions on

    Volume: 23 , Issue: 2
    DOI: 10.1109/TVLSI.2014.2305699
    Publication Year: 2015 , Page(s): 230 - 243

    IEEE Journals & Magazines

    This paper presents a low-complexity algorithm and the corresponding hardware based on the coordinated polynomial solutions for solving line spectrum pairs (LSPs). To improve the computation of LSPs, the enhanced Tschirnhaus transform (ETT) is proposed to accelerate the coordinated polynomial solution. The proposed ETT can replace fractional multiplication with addition and shift operations, so unnecessary operations are avoided. To further simplify the hardware of the ETT, three designs are presented: the preprocessing block (PPB), the iterative root-finding block (IRFB), and the closed-form solution block (CFSB). The PPB provides a design with less gate counts that can effectively transform LPCs into general-form polynomials. Such polynomials can be further decomposed into roots using the proposed IRFB based on the Birge-Vieta method. A pipeline-recursive framework is implemented in the IRFB to save calculations. To improve hardware utilization, this paper also analyzes the coefficients relationship of the ETT by introducing the data dependency graph to design the proposed functional blocks in CFSB. The experimental results show that the proposed hardware achieves a 40-fold improvement in throughput and reduces 1.16% of gate counts at the hardware synthesis level; the chip area is 1.29 ${rm mm}^{2}$ . The precision analysis indicates the average log spectral distance is 0.310. Moreover, the ETT in the proposed hardware only requires 29.9% of multiplication compared with the original one. Such results reveal that the proposed work is superior to the baseline work, thereby demonstrating the effectiveness of the proposed design. View full abstract»

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    Lumen Segmentation in Intravascular Optical Coherence Tomography using Backscattering Tracked and Initialized Random Walks

    Guha Roy, A. ; Conjeti, S. ; Carlier, S. ; Dutta, P. ; Kastrati, A. ; Laine, A. ; Navab, N. ; Katouzian, A. ; Sheet, D.
    Biomedical and Health Informatics, IEEE Journal of

    Volume: PP , Issue: 99
    DOI: 10.1109/JBHI.2015.2403713
    Publication Year: 2015 , Page(s): 1

    IEEE Early Access Articles

    Intravascular imaging using ultrasound (IVUS) or optical coherence tomography (OCT) is predominantly used to adjunct clinical information in interventional cardiology. OCT provides high-resolution images for detailed investigation of atherosclerosis induced thickening of the lumen wall resulting in arterial blockage and triggering acute coronary events. However, the stochastic uncertainty of speckles limits effective visual investigation over large volume of pullback data and clinicians are challenged by their inability to investigate subtle variations in the lumen topology associated with plaque vulnerability and onset of necrosis. This paper presents a lumen segmentation method using OCT imaging physics based graph representation of signals and random walks image segmentation approaches. The edge weights in the graph are assigned incorporating OCT signal attenuation physics models. Optical backscattering maxima is tracked along each A-scan of OCT and is subsequently refined using global graylevel statistics and used for initializing seeds for the random walks image segmentation. Accuracy of lumen vs. tunica segmentation has been measured on 15 in vitro and 6 in vivo pullbacks, each with 150-200 frames using (a) Cohen’s kappa coefficient (0:9786 0:0061) measured with respect to cardiologist’s annotation and (b) divergence of histogram of the segments computed with Kullback-Leibler (5:17 2:39) and Bhattacharya measures (0:56 0:28). High segmentation accuracy and consistency substantiates the characteristics of this method to reliably segment lumen across pullbacks in presence of vulnerability cues and necrotic pool, and has a deterministic finite time-complexity. This paper in general also illustrates development of methods and framework for tissue classification and segmentation incorporating cues of tissue-energy interaction physics in imaging. View full abstract»

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    Petascale Cosmology: Simulations of Structure Formation

    Croft, Rupert ; Di Matteo, Tiziana ; Khandai, Nishikanta ; Feng, Yu
    Computing in Science & Engineering

    Volume: 17 , Issue: 2
    DOI: 10.1109/MCSE.2015.5
    Publication Year: 2015 , Page(s): 40 - 46

    IEEE Journals & Magazines

    Simulations of the entire universe are by definition models of the largest and most complex physical system that exists. In carrying them out, simulators seek to discretize the matter (and radiation) in a model universe and follow their evolution from the Big Bang to the present day. View full abstract»

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    Formation of Ag/Al Screen-Printing Contacts on B Emitters

    Fritz, S. ; König, M. ; Riegel, S. ; Herguth, A. ; Hörteis, M. ; Hahn, G.
    Photovoltaics, IEEE Journal of

    Volume: 5 , Issue: 1
    DOI: 10.1109/JPHOTOV.2014.2364117
    Publication Year: 2015 , Page(s): 145 - 151

    IEEE Journals & Magazines

    In this study, the contact formation process of Al containing Ag screen-printing pastes to BBr3-based B emitters on Si is investigated. Therefore, a detailed scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy study of top-view and cross-sectional samples was conducted. The possible influence of a SiN:H antireflection coating was considered by comparing contacts with and without a SiN:H layer. To analyze the role of the glass frit in the paste, the contact formation of pastes without glass was examined. The results indicate that the Ag/Al contact spots grow below the Si surface/SiN:H layer. The glass frit is only indispensable for etching the antireflection layer-it is not needed for melting the metal in the screen-printing paste. The realized experiments lead to a phenomenological model for the contact formation process of Al containing screen-printing pastes to boron emitters. View full abstract»

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    Optimal Parameter Selection for the Alternating Direction Method of Multipliers (ADMM): Quadratic Problems

    Ghadimi, E. ; Teixeira, A. ; Shames, I. ; Johansson, M.
    Automatic Control, IEEE Transactions on

    Volume: 60 , Issue: 3
    DOI: 10.1109/TAC.2014.2354892
    Publication Year: 2015 , Page(s): 644 - 658

    IEEE Journals & Magazines

    The alternating direction method of multipliers (ADMM) has emerged as a powerful technique for large-scale structured optimization. Despite many recent results on the convergence properties of ADMM, a quantitative characterization of the impact of the algorithm parameters on the convergence times of the method is still lacking. In this paper we find the optimal algorithm parameters that minimize the convergence factor of the ADMM iterates in the context of $ell_{2} $-regularized minimization and constrained quadratic programming. Numerical examples show that our parameter selection rules significantly outperform existing alternatives in the literature. View full abstract»

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    Timely Event Detection by Networked Learners

    Canzian, L. ; Van Der Schaar, M.
    Signal Processing, IEEE Transactions on

    Volume: 63 , Issue: 5
    DOI: 10.1109/TSP.2015.2389765
    Publication Year: 2015 , Page(s): 1282 - 1296

    IEEE Journals & Magazines

    We consider a set of distributed learners that are interconnected via an exogenously-determined network. The learners observe different data streams that are related to common events of interest, which need to be detected in a timely manner. Each learner is equipped with a set of local classifiers, which generate local predictions about the common event based on the locally observed data streams. In this work, we address the following key questions: (1) Can the learners improve their detection accuracy by exchanging and aggregating information? (2) Can the learners improve the timeliness of their detections by forming clusters, i.e., by collecting information only from surrounding learners? (3) Given a specific tradeoff between detection accuracy and detection delay, is it desirable to aggregate a large amount of information, or is it better to focus on the most recent and relevant information? To address these questions, we propose a cooperative online learning scheme in which each learner maintains a set of weight vectors (one for each possible cluster), selects a cluster and the corresponding weight vector, generates a local prediction, disseminates it through the network, and combines all the received local predictions from the learners belonging to the selected cluster by using a weighted majority rule. The optimal cluster and weight vector that a learner should adopt depend on the specific network topology, on the location of the learner in the network, and on the characteristics of the data streams. To learn such optimal values, we propose a general online learning rule that exploits only the feedbacks that the learners receive. We determine an upper bound for the worst-case mis-detection probability and for the worst-case prediction delay of our scheme in the realizable case. Numerical simulations show that the proposed scheme is able to successfully adapt to the unknown characteristics of the data streams and can achieve substantial performance gains with - espect to a scheme in which the learners act individually or a scheme in which the learners always aggregate all available local predictions. We numerically evaluate the impact that different network topologies have on the final performance. Finally, we discuss several surprising existing trade-offs. View full abstract»

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    Wideband Spectrum Sensing for Cognitive Radios: A Multistage Wiener Filter Perspective

    Qing, H. ; Liu, Y. ; Xie, G. ; Gao, J.
    Signal Processing Letters, IEEE

    Volume: 22 , Issue: 3
    DOI: 10.1109/LSP.2014.2359491
    Publication Year: 2015 , Page(s): 332 - 335

    IEEE Journals & Magazines

    A wideband spectrum sensing scheme for cognitive radios is put forward in this letter. The proposed method operates over the total frequency bands simultaneously rather than a single band each time. It first estimates the number of occupied subbands, and then determines the accurate locations of occupied subbands as well as the vacant ones. Applying the ideas of multi stage Wiener filter to Gerschgorin disk estimator, this approach jointly makes the decision. In this way, the detection performance is enhanced because of capturing the signal information and suppressing the additive noise. Meanwhile, this approach avoids estimating the covariance matrix as well as the eigenvalue decomposition, and thus achieves a low computational complexity. Distinct from the conventional algorithms, neither noise power estimation nor prior knowledge of primary user signal is required, making the proposed algorithm robust to noise uncertainty and suitable for blind detection. Simulations under various conditions are presented to demonstrate the benefits of this approach and the results indicate that it surpasses the existing sensing algorithms. View full abstract»

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    An Iterative Method for Calculating Robust Rating Scores

    Allahbakhsh, M. ; Ignjatovic, A.
    Parallel and Distributed Systems, IEEE Transactions on

    Volume: 26 , Issue: 2
    DOI: 10.1109/TPDS.2013.215
    Publication Year: 2015 , Page(s): 340 - 350

    IEEE Journals & Magazines

    Online rating systems are widely used to facilitate making decisions on the web. For fame or profit, people may try to manipulate such systems by posting unfair evaluations. Therefore, determining objective rating scores of products or services becomes a very important yet difficult problem. Existing solutions are mostly majority based, also employing temporal analysis and clustering techniques. However, they are still vulnerable to sophisticated collaborative attacks. In this paper we propose an iterative rating algorithm which is very robust against collusion attacks as well as random and biased raters. Unlike previous iterative methods, our method is not based on comparing submitted evaluations to an approximation of the final rating scores, and it entirely decouples credibility assessment of the cast evaluations from the ranking itself. This makes it more robust against sophisticated collusion attacks than the previous iterative filtering algorithms. We provide a rigorous proof of convergence of our algorithm based on the existence of a fixed point of a continuous mapping which also happens to be a stationary point of a constrained optimization objective. We have implemented and tested our rating method using both simulated data as well as real world movie rating data. Our tests demonstrate that our model calculates realistic rating scores even in the presence of massive collusion attacks and outperforms well-known algorithms in the area. The results of applying our algorithm on the real-world data obtained from MovieLens conforms highly with the rating scores given by Rotten Tomatoes movie critics as domain experts for movies. View full abstract»

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    Continuous Finite-Time Output Regulation for Disturbed Systems Under Mismatching Condition

    Shihua Li ; Haibin Sun ; Jun Yang ; Xinghuo Yu
    Automatic Control, IEEE Transactions on

    Volume: 60 , Issue: 1
    DOI: 10.1109/TAC.2014.2324212
    Publication Year: 2015 , Page(s): 277 - 282

    IEEE Journals & Magazines

    In this technical note, the problem of finite-time output regulation control for a class of disturbed system under mismatching condition is investigated via a composite control design manner. The composite controller is developed by using a finite time control technique and a finite time disturbance observer (FTDO). A key idea is to design virtual control laws based on estimation values of the disturbances and the ith (1 ≤ i ≤ n - 1 where n is the order of the system) order derivative of disturbances. Finite time stability analysis for the augmented system is presented by means of Lyapunov stability theorems, which shows that the system output is regulated to zero in finite time even in the presence of mismatched disturbances. A motion control application demonstrates the effectiveness and attractive properties of the proposed method. View full abstract»

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    Magnetic Shield Material Characterization for the Facility for Rare Isotope Beams' Cryomodules

    Chandrasekaran, S.K. ; Saito, K. ; Shanab, S. ; Chouhan, S. ; Compton, C. ; Elliott, K. ; Leitner, M. ; Ozelis, J.
    Applied Superconductivity, IEEE Transactions on

    Volume: 25 , Issue: 3 , Part: 2
    DOI: 10.1109/TASC.2014.2375192
    Publication Year: 2015 , Article#: 3500305

    IEEE Journals & Magazines

    The saturation fields of cylindrical cryogenic magnetic shields, for quarter-wave resonator cavities, of diameters ranging from 229 to 447 mm were measured at 300 and 10 K. A 0.86 T normal conducting solenoid and a 2.5 T superconducting solenoid were used at 300 and 10 K, respectively. The shielding of the high magnetic field region of the cavity, due to fringe fields entering the shield through the beam-port holes of the shield, was examined. The relative initial permeability of toroidal samples from two cryogenic shielding materials were measured at 0.358 A/m, at different frequencies, to extrapolate the static value. These samples were also exposed to external fields up to 0.86 T at 300 K, and the residual magnetic field was measured to check for magnetization of the shielding materials. Results indicate that the performances of the measured cryogenic shielding materials are dependent on the magnitude of the applied field. The performances are improved at cryogenic temperatures only when the shields are exposed to small magnetic fields. At greater fields, however, the performance is degraded at cryogenic temperatures. The shielding materials are not magnetized when exposed to fields up to 0.86 T. View full abstract»

  • Freely Available from IEEE

    IEEE Systems, Man, and Cybernetics Society Information


    Systems, Man, and Cybernetics: Systems, IEEE Transactions on

    Volume: 45 , Issue: 3
    DOI: 10.1109/TSMC.2015.2401813
    Publication Year: 2015 , Page(s): C3

    IEEE Journals & Magazines

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    The Smart-Condo: Optimizing Sensor Placement for Indoor Localization

    Vlasenko, I. ; Nikolaidis, I. ; Stroulia, E.
    Systems, Man, and Cybernetics: Systems, IEEE Transactions on

    Volume: 45 , Issue: 3
    DOI: 10.1109/TSMC.2014.2356437
    Publication Year: 2015 , Page(s): 436 - 453

    IEEE Journals & Magazines

    Multimedia

    The Smart-Condo is a hardware/software platform that aims to support and assist an individual in performing a variety of everyday tasks within his/her living space. The key to achieving this goal is being able to recognize the individual’s general activities in real-time, without impeding these activities or compromising privacy. Since location and movement constitute meaningful evidence for many everyday tasks (e.g., presence in the bathroom correlates with personal hygiene activities), we are motivated to develop an efficient, accurate, and noninvasive occupant-localization method. To this end, we propose a methodology for planning the deployment of an array of privacy-respecting binary motion sensors. In particular, given the geometric constraints of the deployment space, we generate a model of indoor mobility patterns typical for a single occupant. We then use this model as the basis for a specific optimization problem: maximizing a measure of how well the frequently-visited areas of the living space are covered by a number of sensors, subject to a cardinality constraint on this number. We argue this optimization objective is a good surrogate for maximizing localization accuracy, and prove that it bears exploitable properties that make it receptive to a simple optimization routine. As a result, we obtain sensor configurations with localization accuracy superior to that achievable with the same number of sensors placed manually or randomly in the same environment. View full abstract»

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    A High-Gain Wideband Antenna With Frequency Selective Side Reflectors Operating in an Anti-Resonant Mode

    Kim, D. ; Kim, E.
    Antennas and Wireless Propagation Letters, IEEE

    Volume: 14
    DOI: 10.1109/LAWP.2014.2363199
    Publication Year: 2015 , Page(s): 442 - 445

    IEEE Journals & Magazines

    We propose a new high-gain wideband antenna with simple frequency selective reflectors (FSRs), which are installed at both sides of a source dipole antenna. The main role of each FSR is to transmit electromagnetic waves in a boresight direction, which is intended to increase antenna gain and an impedance-matching bandwidth at the same time. To do that, we operate the antenna in an anti-resonance mode, which is a conceptual shift of conventional Fabry–Perot (FP) resonance operation. Hence, the proposed FSRs operating under the anti-resonance mode collimate outgoing waves toward their lateral direction rather than a conventional normal direction. As a result, we can improve both the realized gain and the bandwidth up to about 12 dBi and 41% ( { S}_{11} = -10~\hbox {dB} ), respectively, only with one dipole antenna. All experiments show good agreement with predictions, which confirm the validity and usefulness of our approach. View full abstract»

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    From Optimal to Real-Time Control of a Mechanical Hybrid Powertrain

    van Berkel, K. ; Titulaer, R. ; Hofman, T. ; Vroemen, B. ; Steinbuch, M.
    Control Systems Technology, IEEE Transactions on

    Volume: 23 , Issue: 2
    DOI: 10.1109/TCST.2014.2334476
    Publication Year: 2015 , Page(s): 670 - 678

    IEEE Journals & Magazines

    This brief presents the design of an energy controller for a mechanical hybrid powertrain, which is suitable for implementation in real-time hardware. The mechanical hybrid powertrain uses a compact flywheel module to add hybrid functionalities to a conventional powertrain that consists of an internal combustion engine and a continuously variable transmission. The control objective is to minimize the overall fuel consumption for a given driving cycle. The design approach follows a generic framework to: 1) solve the optimization problem using optimal control; 2) make the optimal controller causal using a prediction of the future driving conditions; and 3) make the causal controller robust by tuning of one key calibration parameter. The highly constrained optimization problem is solved with dynamic programming. The future driving conditions are predicted using a model that smoothly approximates statistical data, and implemented in the receding model predictive control framework. The controller is made tunable by rule extraction from the model predictive controller, based on physical understanding of the system. The resulting real-time controller is transparent, causal, and robust, where the latter is shown by simulations for various driving cycles and start conditions. View full abstract»

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    Integration of solar generation into electricity markets: an Australian National Electricity Market case study

    Gilmore, J. ; Vanderwaal, B. ; Rose, I. ; Riesz, J.
    Renewable Power Generation, IET

    Volume: 9 , Issue: 1
    DOI: 10.1049/iet-rpg.2014.0108
    Publication Year: 2015 , Page(s): 46 - 56

    IET Journals & Magazines

    Historically, solar photovoltaic (PV) generation has been able to claim a significant `premium' in revenues over other generation types because of its correlation in operation with peak demand (and therefore high priced) periods. However, similar to many international markets, recent conditions in the Australian National Electricity Market, including low demand, high levels of rooftop PV generation and oversupply of capacity, are found to have eliminated the revenue premium for solar. Half-hourly modelling to 2030 illustrates that historical premiums are unlikely to resurface. Storage is shown to increase solar revenues at high penetrations, but can have a detrimental effect on solar revenues at lower solar penetration levels. Therefore at high solar penetration levels, solar generators will be incentivised to develop storage assets, since they can capture additional portfolio market benefits by minimising the decline in solar premiums because of the merit order effect. In contrast, most other market participants will find storage detrimental to revenues because of increasing competition during high priced periods, and will therefore have less incentive to include storage in their portfolios. View full abstract»

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    Coupled Analysis and Protection of the HTS DC Magnet for DC Induction Heater in Dynamic Disturbance

    Xu, D. ; Wang, Y. ; Li, Z.Y. ; Gao, H. ; Hong, Z. ; Jin, Z.
    Applied Superconductivity, IEEE Transactions on

    Volume: 25 , Issue: 3 , Part: 2
    DOI: 10.1109/TASC.2014.2375576
    Publication Year: 2015 , Article#: 4602605

    IEEE Journals & Magazines

    Designing a high temperature superconducting (HTS) DC induction heater requires the HTS magnet to be equipped with an HTS coil, iron core and air gap. A large amount of magnetic energy is stored in the iron core and must be transferred outside the magnet during system collapses. The nature of the operating conditions and dynamic heating processes make the magnet coil a substantial nonlinear inductive load for the power supply which can result in system collapse and potentially damage the peripheral circuit of the magnet. Therefore, a protection system is recommended for this magnet. This paper proposes an active protection system for a DC HTS induction heater composed of a magnet with an iron core and YBCO coated conductor (CC) tape. A Matlab/Simulink-based simulation model was coupled with a Comsol-based finite element method model to combine the electrical and electromagnetic characteristics to optimize the design configuration of the protection circuit. Experiments with different magnet operating currents and dump resistors were carried out to verify the feasibility of this proposed protection system for magnets with and without an iron core. The results show that the proposed scheme performs within desired specifications and that the dissipation efficiency and velocity vary depending upon different values of the dump resistor. View full abstract»

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    The Impact of Heterogeneous Computing on Workflows for Biomolecular Simulation and Analysis

    Cheatham III, Thomas E. ; Roe, Daniel R.
    Computing in Science & Engineering

    Volume: 17 , Issue: 2
    DOI: 10.1109/MCSE.2015.7
    Publication Year: 2015 , Page(s): 30 - 39

    IEEE Journals & Magazines

    The field of biomolecular simulation has matured to where detailed, accurate, and functionally relevant information that complements experimental data about the structure, dynamics, and interactions of biomolecules can now be routinely discovered. This has been enabled by access to large-scale and heterogeneous high-performance computing resources, including special-purpose hardware. The improved performance of modern simulation methods coupled with hardware advances is shifting the rate-limiting steps of common biomolecular simulations of small to moderately sized systems from the generation of data (for example, via production molecular dynamics simulations that used to take weeks or even months) to the pre- and postprocessing phases of the workflow, namely, simulation setup and data processing, management, and analysis. Because the computational resources that are optimal for generating data aren't necessarily the same as for processing that data, access to heterogeneous computational resources enables a broader exploration of biomolecular structure and dynamics by facilitating distinct aspects of typical biomolecular simulation workflows, which might not be as efficient on a one-size-fits-all computational platform. View full abstract»

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