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Graded Bit-Error-Correcting Codes With Applications to Flash Memory

IEEE TRANSACTIONS ON INFORMATION theory 2013年第4期59卷 2315-2327页

作者： Gabrys, Ryan Yaakobi, Eitan Dolecek, Lara Univ Calif Los Angeles Los Angeles CA 90095 USA CALTECH Pasadena CA 91106 USA

Flash memory is a promising new storage technology. Supported by empirical data collected from a Flash memory device, we propose a class of codes that exploits the asymmetric nature of the error patterns in a Flash device using tensor product operations. We call these codes graded bit-error-correcting codes. As demonstrated on the data collected from a Flash chip, these codes significantly delay the onset of errors and therefore have the potential to prolong the lifetime of the memory device.

关键词： coding theory error-correcting codes flash memory tensor product codes

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Torsion Dynamic Behaviour of the Ship Hull Made out of Layered Composites

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-7页

作者： Chirica, Ionel Dunarea de Jos Univ Galati Galati 800008 Romania

This paper addresses the dynamic torsion behaviour of the ship hull with very large open decks. A short overview of the past research is presented, and several key findings and behavioral characteristics are discussed. In the paper, the author is focusing on the dynamic part of a new macroelement model used for torsion dynamic analysis of the ship hull made of composite materials. The numerical analysis (using two methods, one of them being a new proposed method) and experiments are developed on a simplified typical hull of a container ship. The torsion analysis is performed on a scale model of a container ship, made of layered composite plates, and the first 5 natural frequencies are determined. The results obtained with the proposed numerical method (software code TORS, made by the author) are compared with the results obtained with FE analysis and with the experiments done on the physical model.

关键词： TORSION COMPOSITE materials BRIDGE floors CONTAINER ships COMPUTER software coding theory

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Development and assessment of a sub-channel code applicable for trans-critical transient of SCWR

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NUCLEAR ENGINEERING AND DESIGN 2013年 262卷 499-509页

作者： Liu, X. J. Yang, T. Cheng, X. Shanghai Jiao Tong Univ Sch Nucl Sci & Engn Shanghai 200240 Peoples R China Karlsruhe Inst Technol Inst Fus & Reactor Technol D-76131 Karlsruhe Germany

In the last few years, extensive R&D activities have been launched covering various aspects of super-critical water-cooled reactor (SCWR), especially the thermal-hydraulic analysis. Sub-channel code plays an indispensable role to predict the detail thermal-hydraulic behavior of the SCWR fuel assembly. This paper develops a new version of sub-channel code COBRA-SC based on the previous COBRA-IV code. The supercritical water property and heat transfer/pressure drop correlations under supercritical pressure are implemented to this code. Moreover, in order to simulate the trans-critical transient (the pressure undergo a decrease from the supercritical pressure to the subcritical pressure), pseudo two-phase method is employed in COBRA-SC code. This work is completed by introduction of a virtual two-phase region near the pseudo-critical line. A smooth transition of void fraction can be realized. In addition, several heat transfer correlations right underneath the critical point are introduced into this code to capture the heat transfer behavior during the trans-critical transient. Some experimental data from simple geometry, e.g. the single tube, small rod bundle, is used to validate and evaluate this new developed COBRA-SC code. The predicted results show a good agreement with the experimental data, demonstrating good feasibility of this code for SCWR condition. A code to code comparison between COBRA-SC and ATHLET for a blowdown transient of a small fuel assembly is also presented and discussed in this paper. (C) 2013 Elsevier B.V. All rights reserved.

关键词： CHANNEL coding SUPERCRITICAL water NUMERICAL calculations TWO-phase flow coding theory

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Multiscale unit-memory convolutional codes

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IET COMMUNICATIONS 2013年第11期7卷 1043-1050页

作者： Nagaraj, Santosh V. Bell, Mark R. San Diego State Univ Dept Elect & Comp Engn San Diego CA 92182 USA Purdue Univ Sch Elect W Lafayette IN 47907 USA

In this study, authors propose structure to unit memory (UM) convolutional codes that greatly simplify their decoding when using sequential or suboptimal L-decoders. The multiscale structure proposed in this study preserves the word-oriented nature of unit memory codes (UMCs), but allows for processing the code in blocks of sizes less than the memory of the code with non-Viterbi-type decoders. At one end of the multiscale structure are generic UMCs. At the other end are structured systematic UMCs that can be decoded with the same ease as conventional multimemory convolutional codes with sequential or L-decoders. As a special case, the authors show quick-look parity check systematic codes of arbitrary rates that are better than previously known optimum minimum distance systematic convolutional codes. These codes are derived from block codes and the convolutional code can be decoded using the syndrome decoder of the underlying block code. The authors present simulation results and analysis to support the proposed multiscale UM convolutional codes.

关键词： coding theory PARITY-check matrix MEMORY transfer THOUGHT & thinking SIMULATION methods & models

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Analytical Particular Solutions of Multiquadrics Associated with Polyharmonic Operators

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MATHEMATICAL PROBLEMS IN ENGINEERING 2013年第1期2013卷 1-11页

作者： Tsai, Chia-Cheng Natl Kaohsiung Marine Univ Dept Marine Environm Engn Kaohsiung 811 Taiwan

We derive two-and three-dimensional analytical particular solutions of multiquadrics (MQ) associated with the polyharmonic operators, named as the polyharmonic multiquadrics (PMQs). The methods of undetermined coefficients are constructed by observing the first few orders of the PMQs which are obtained by the symbolic software, Mathematica. By expanding the PMQs into the Laurent series, the unknown coefficients of the PMQs can be determined. The homogeneous parts of the PMQs are suitably arranged so that the PMQs are hierarchically unique and infinitely differentiable. Mathematica codes are provided for obtaining the PMQs of arbitrary orders. The derived PMQs are validated by numerical solutions for Poisson's equation. Numerical results indicate that the solutions obtained by the PMQs are more accurate than those by the MQ.

关键词： POLYHARMONIC functions OPERATOR theory COMPUTER software LAURENT series coding theory POISSON'S equation

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Toward a Statistical Framework for Source Anonymity in Sensor Networks

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IEEE TRANSACTIONS ON MOBILE COMPUTING 2013年第2期12卷 248-260页

作者： Alomair, Basel Clark, Andrew Cuellar, Jorge Poovendran, Radha KACST CRI POB 6086 Riyadh 11442 Saudi Arabia Univ Washington Dept Elect Engn NSL Seattle WA 98195 USA CERT Corp Res & Technol CT T DE IT1 D-81739 Munich Germany

In certain applications, the locations of events reported by a sensor network need to remain anonymous. That is, unauthorized observers must be unable to detect the origin of such events by analyzing the network traffic. Known as the source anonymity problem, this problem has emerged as an important topic in the security of wireless sensor networks, with variety of techniques based on different adversarial assumptions being proposed. In this work, we present a new framework for modeling, analyzing, and evaluating anonymity in sensor networks. The novelty of the proposed framework is twofold: first, it introduces the notion of "interval indistinguishability" and provides a quantitative measure to model anonymity in wireless sensor networks;second, it maps source anonymity to the statistical problem of binary hypothesis testing with nuisance parameters. We then analyze existing solutions for designing anonymous sensor networks using the proposed model. We show how mapping source anonymity to binary hypothesis testing with nuisance parameters leads to converting the problem of exposing private source information into searching for an appropriate data transformation that removes or minimize the effect of the nuisance information. By doing so, we transform the problem from analyzing real-valued sample points to binary codes, which opens the door for coding theory to be incorporated into the study of anonymous sensor networks. Finally, we discuss how existing solutions can be modified to improve their anonymity.

关键词： Wireless sensor networks (WSN) source location privacy anonymity hypothesis testing nuisance parameters coding theory

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LOCAL-OPTIMALITY GUARANTEES BASED ON PATHS FOR OPTIMAL DEcoding

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SIAM JOURNAL ON DISCRETE MATHEMATICS 2013年第4期27卷 2049-2063页

作者： Even, Guy Halabi, Nissim Tel Aviv Univ Sch Elect Engn IL-69978 Tel Aviv Israel

This paper presents a unified analysis framework that captures recent advances in the study of local-optimality characterizations for codes on graphs. These local-optimality characterizations are based on combinatorial structures embedded in the Tanner graph of the code. Local optimality implies both unique maximum likelihood optimality and unique linear programming (LP) decoding optimality. Also, an iterative message-passing decoding algorithm is guaranteed to find the unique locally optimal codeword if one exists. We demonstrate an instance of this proof technique by considering a definition of local optimality that is based on the simplest combinatorial structures in Tanner graphs, namely, paths of length h. We apply the technique of local optimality to binary Tanner codes (including any low-density parity-check code, and in particular any irregular repeat-accumulate code with both even and odd repetition factors). Inverse polynomial bounds in the code length are proved on the word error probability of LP decoding for binary Tanner codes. When the local codes are restricted to single parity-check codes, these bounds also hold for decoding by a certain iterative message-passing decoding algorithm.

关键词： coding theory Tanner codes local optimality maximum likelihood linear programming decoding error probability iterative message-passing decoding repeat-accumulate codes

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Analytical models for a small LFR core dynamics studies

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NUCLEAR ENGINEERING AND DESIGN 2013年 254卷 67-88页

作者： Lorenzi, S. Cammi, A. Bortot, S. Ponciroli, R. Moisseytsev, A. Politecn Milan Nucl Engn Div CeSNEF Dept Energy I-20156 Milan Italy Argonne Natl Lab Nucl Engn Div Argonne IL 60439 USA

Analytical models for the study of a small Lead-cooled Fast Reactor (LFR) demonstrator (DEMO) core dynamics, in a control-oriented perspective, have been developed aimed at providing a useful, very flexible and straightforward tool allowing relatively quick transient design-basis and stability analyses. A simplified approach has been developed consisting in a lumped-parameter modeling of the coupled neutronics and thermal-hydraulics. The reactor transient responses following both postulated accident initiators such as Unprotected Transient of OverPower (UTOP), Loss of Heat Sink (ULOHS) and Loss of Flow (ULOF), and an emergency SCRAM event have been studied in MATLAB/SIMULINK (R) environment. A benchmark analysis has been then performed by means of the SAS4A/SASSYS-1 Liquid Metal Reactor Code System with the purpose of providing verification for the analytical outcomes of the nonlinear model and indicating how the latter relate to more realistic one-dimensional calculations. As a general result, responses concerning the main core characteristics (namely, power, reactivity, etc.) have turned out to be mutually consistent in terms of both steady-state absolute figures and transient developments, showing discrepancies of the order of only few per cents. DEMO dynamic behavior has been studied through a linear approach as well, so as to enable the use of linear analysis tools allowing to verify the system stability, thanks to the possibility of expressing a physical model in terms of transfer functions or state-space representation. The impact of linearization and point-kinetics one-precursor-group approximation has been further evaluated by examining the respective transient predictions, which have been compared to the nonlinear reference ones for increasing perturbations. An asymptotic stability analysis, according to Lyapunov's definition, is finally presented. (C) 2012 Elsevier B.V. All rights reserved.

关键词： FAST reactors STABILITY (Mechanics) LUMPED parameter systems COUPLED mode theory (Wave-motion) HEAT sinks (Electronics) coding theory NONLINEAR analysis

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Continuous firefly algorithm applied to PWR core pattern enhancement

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NUCLEAR ENGINEERING AND DESIGN 2013年 258卷 107-115页

作者： Poursalehi, N. Zolfaghari, A. Minuchehr, A. Moghaddam, H. K. Shahid Beheshti Univ Dept Engn GC Tehran Iran

In this research, the new meta-heuristic optimization strategy, firefly algorithm, is developed for the nuclear reactor loading pattern optimization problem. Two main goals in reactor core fuel management optimization are maximizing the core multiplication factor (Kerr) in order to extract the maximum cycle energy and minimizing the power peaking factor due to safety constraints. In this work, we define a multi-objective fitness function according to above goals for the core fuel arrangement enhancement. In order to evaluate and demonstrate the ability of continuous firefly algorithm (CFA) to find the near optimal loading pattern, we developed CFA nodal expansion code (CFANEC) for the fuel management operation. This code consists of two main modules including CFA optimization program and a developed core analysis code implementing nodal expansion method to calculate with coarse meshes by dimensions of fuel assemblies. At first, CFA is applied for the Foxholes test case with continuous variables in order to validate CFA and then for KWU PWR using a decoding strategy for discrete variables. Results indicate the efficiency and relatively fast convergence of CFA in obtaining near optimal loading pattern with respect to considered fitness function. At last, our experience with the CFA confirms that the CFA is easy to implement and reliable. (C) 2013 Elsevier B.V. All rights reserved.

关键词： PRESSURIZED water reactors NUCLEAR reactors -- Cores ALGORITHMS CONTINUOUS flow reactors PATTERN recognition systems MATHEMATICAL optimization coding theory

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Combined one-dimensional lowpass and highpass filters for subband transformer

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ELECTRONICS LETTERS 2013年第18期49卷 1150-1151页

作者： Rajovic, V. Savic, G. Ceperkovic, V. Prokin, M. Univ Belgrade Sch Elect Engn Belgrade Serbia

Subband transformation coefficients are typically computed by first filtering and downsampling of an input uncompressed signal and then subsequently filtering and downsampling the result intermediate signals with a set of lowpass and highpass filters. State-of-the-art subband transformers are complex, which increases consumed power. A novel method for significantly decreasing the complexity of subband transformers to a minimum is presented. This solution was implemented in a field programmable gate array, together with various methods for compression and decompression.

关键词： MATHEMATICAL programming FIELD programmable gate arrays PROGRAMMABLE logic devices coding theory LOGIC devices FUNCTIONAL equations

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