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Critical review of conservation equations for two-phase flow in the U.S. NRC TRACE code

NUCLEAR ENGINEERING AND DESIGN 2011年第10期241卷 4237-4260页

作者： Wulff, Wolfgang 11 Hamilton Rd Setauket NY 11733 USA

The field equations for two-phase flow in the computer code TRAC/RELAP Advanced Computational Engine or TRACE are examined to determine their validity, their capabilities and limitations in resolving nuclear reactor safety issues. TRACE was developed for the NRC to predict thermohydraulic phenomena in nuclear power plants during operational transients and postulated accidents. TRACE is based on the rigorously derived and well-established two-fluid field equations for 1-D and 3-D two-phase flow. It is shown that: (1) The two-fluid field equations for mass conservation as implemented in TRACE are wrong because local mass balances in TRACE are in conflict with mass conservation for the whole reactor system, as shown in Section 3.1. (2) Wrong equations of motion are used in TRACE in place of momentum balances, compromising at branch points the prediction of momentum transfer between, and the coupling of, loops in hydraulic networks by impedance (form loss and wall shear) and by inertia and thereby the simulation of reactor component interactions. (3) Most seriously, TRACE calculation of heat transfer from fuel elements is incorrect for single and two-phase flows, because Eq. (3-4) of the TRACE Manual is wrong (see Section 5.2). (4) Boundary conditions for momentum and energy balances in TRACE are restricted to flow regimes(1) with single-phase wall contact because TRACE lacks constitutive relations for solid-fluid exchange of momentum and heat in prevailing flow regimes. Without a quantified assessment of consequences from (3) to (4), predictions of phasic fluid velocities, fuel temperatures and important safety parameters, e.g., peak clad temperature, are questionable. Moreover, TRACE cannot predict 3-D single- or two-phase flows because: (5) incorrectly averaged equations are used for 3-D predictions, (6) fluid shear is ignored but needed to predict counter-current flows with the two-fluid model, and (7) fictitious body forces and fictitious distributed mass and heat

关键词： TWO-phase flow coding theory FIELD theory (Physics) NUCLEAR reactors -- Safety measures HYDRAULICS NUCLEAR power plants HEAT transfer

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Location and sizing of a plant stack: Design study using CFD

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NUCLEAR ENGINEERING AND DESIGN 2011年第6期241卷 2248-2256页

作者： Petrangeli, Gianni Univ Pisa I-56123 Pisa Italy

The effect of the presence of a stack on the ground level concentration of emissions near the plant is to significantly decrease the concentrations (in practical cases of interest, by a factor of 5-10), while the presence of nearby plant buildings is to partly eliminate this beneficial effect due to the effect of the building wake. The author of this paper believes that the practical methods currently used for the evaluation of ground concentrations in these cases deserve some improvement. One line of development here suggested is the use of Computer Fluid Dynamics (CFD) codes. The author believes that presently available Code Packages in this field are sufficiently accurate. A number of case studies are presented in this paper, with the aim of encouraging the use of these rather simple methods of study. Moreover, a comparison of calculation results with a field test results confirms also the quantitative reliability of the calculation method here proposed. The main conclusions of this exercise could be the following: - The use of CFD Computer Codes seems suitable for atmospheric dispersion calculations of interest to the nuclear plant designer and safety analyst;in particular, for design studies aimed at the definition of nuclear plant and stack arrangements, the result of this exercise seem to indicate that the methods here used are completely suitable for the comparison of various solutions. - The use of CFD codes may avoid wrong decisions, like the elimination of a stack in the design of a nuclear plant;excessive and detrimental over-conservatism can also be avoided. - When adequate guidance is provided, as this paper attempts to do (Appendix), the CFD calculation methods are rather robust and simple to perform. (C) 2011 Elsevier B.V. All rights reserved.

关键词： NUCLEAR power plants -- Design & construction COMPUTATIONAL fluid dynamics RELIABILITY (Engineering) coding theory NUMERICAL calculations QUANTITATIVE research CASE studies

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Soft decoding of the (23,12,7) Golay-code up to five errors

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IET COMMUNICATIONS 2011年第15期5卷 2206-2211页

作者： Li, Y. Wang, L. Truong, T-K Xiamen Univ Dept Commun Engn Xiamen 361005 Fujian Peoples R China I Shou Univ Dept Informat Engn Kaohsiung Cty 840 Taiwan Natl Sun Yat Sen Univ Dept Comp Sci & Engn Kaohsiung Taiwan

A new decoder is proposed to decode the (23, 12, 7) binary Golay-code up to five errors. It is based on the algorithm that can correct up to four errors for the (24, 12, 8) extended Golay-code proposed by Lin et al., thereby achieving the soft decoding in the real sense for the Golay-code. For a weight-2 or weight-3 error pattern decoded by the hard decoder for correcting up to three errors, one can find the corresponding 21 weight-4 or weight-5 error patterns and choose the one with the maximum emblematic probability value, which is defined as the product of individual bit-error probabilities corresponding to the non-zero locations of the error pattern as the ultimate choice. Finally, simulation results of this decoder over additive white Gaussian noise (AWGN) channels show that the proposed method provides 0.9 dB coding gain than that of Lin et al.'s algorithm at bit-error rate of 10(-5).

关键词： DEcoding algorithms BIT error rate SOFT error (Electronics) RANDOM noise theory coding theory DECODERS & decoding

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(1+v)-Constacyclic codes over F₂ + uF₂ + vF₂ + uvF₂

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JOURNAL OF THE FRANKLIN INSTITUTE-ENGINEERING AND APPLIED MATHEMATICS 2011年第9期348卷 2625-2632页

作者： Karadeniz, Suat Yildiz, Bahattin Fatih Univ Dept Math TR-34500 Istanbul Turkey

In this work, (1+v)-constacyclic codes over the ring F-2 + uF(2) + vF(2) + uvF(2) are studied. (1+v)-constacyclic codes over F-2 + uF(2) + vF(2) + uvF(2) of odd lengths are characterized with the help of cyclic codes over F-2 + uF(2) + vF(2) + uvF(2). A natural Gray map from (F-2 + uF(2) + v(2) + uvF(2))(n) to (F-2 + uF(2))(2n) is introduced and it is shown that the image under this map of (1+v)-constacyclic codes over F-2 + uF(2) + vF(2) + uvF(2) are cyclic codes over F-2 + uF(2). Also a substantial number of optimal binary linear codes are obtained as the images of (1+v)-constacyclic codes over F-2 + uF(2) + vF(2) + uvF(2). (C) 2011 The Franklin Institute. Published by Elsevier Ltd. All rights reserved.

关键词： coding theory NUMBER theory BINARY system (Mathematics) LINEAR systems MAPPINGS (Mathematics) IMAGE analysis

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Efficient Algorithms for Computing With Protein-Based Volumetric Memory Processors

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IEEE TRANSACTIONS ON NANOTECHNOLOGY 2011年第4期10卷 881-890页

作者： Rajasekaran, Sanguthevar Kundeti, Vamsi Birge, Robert Kumar, Vipin Sahni, Sartaj Univ Connecticut Dept Comp Sci & Engn Storrs CT 06269 USA Univ Connecticut Dept Chem Storrs CT 06269 USA Univ Minnesota Dept Comp Sci & Engn Minneapolis MN 55455 USA Univ Florida Dept Comp Informat Sci & Engn Gainesville FL 32611 USA

With an ever increasing volume of digital data there is a huge increase in the demand for much faster, smaller, and denser storage technologies. Conventional 2-D (surface) storage/memory technologies may soon be replaced with much faster and denser 3-D volumetric (holographic) storage technologies. Photo sensitive protein bacteriorhodopsin has been proven to have great chemical, thermal, and holographic properties and is a good choice for both associative and volumetric memories. Associative memory systems have a wide range of practical applications. However, there is a lack of a formal computational model that can be used to analyze the performance of different algorithms on architectures that support associative memory. We first address this issue by defining a new computational model on protein-based associative memory processors. We also present and analyze algorithms for several fundamental problems on this new model. Secondly, we employ balanced modulated codes in volumetric memories to reduce the bit error rate and improve fidelity. Conventional coding schemes such as 6 : 8 coding, limit the size of the page to 8 bits and achieve a code rate (utility) of only 75%. As the technology matures we need efficient algorithms to produce these codes with better utility. In this paper, 1 we address this problem and give algorithms that can generate these codes with superior utility.

关键词： Associative memory associative memory processors bacteriorhodopsin coding theory parallel computing protein-based memory volumetric memory

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Ultrasonic Backscatter Imaging by Shear-Wave-Induced Echo Phase Encoding of Target Locations

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IEEE TRANSACTIONS ON ULTRASONICS FERROELECTRICS AND FREQUENCY CONTROL 2011年第1期58卷 102-111页

作者： McAleavey, Stephen Univ Rochester Dept Biomed Engn Rochester NY 14642 USA Univ Rochester Dept Elect & Comp Engn Rochester NY USA

We present a novel method for ultrasound back-scatter image formation wherein lateral resolution of the target is obtained by using traveling shear waves to encode the lateral position of targets in the phase of the received echo. We demonstrate that the phase modulation as a function of shear wavenumber can be expressed in terms of a Fourier transform of the lateral component of the target echogenicity. The inverse transform, obtained by measurements of the phase modulation over a range of shear wave spatial frequencies, yields the lateral scatterer distribution. Range data are recovered from time of flight as in conventional ultrasound, yielding a B-mode-like image. In contrast to conventional ultrasound imaging, where mechanical or electronic focusing is used and lateral resolution is determined by aperture size and wavelength, we demonstrate that lateral resolution using the proposed method is independent of the properties of the aperture. Lateral resolution of the target is achieved using a stationary, unfocused, single-element transducer. We present simulated images of targets of uniform and non-uniform shear modulus. Compounding for speckle reduction is demonstrated. Finally, we demonstrate image formation with an unfocused transducer in gelatin phantoms of uniform shear modulus.

关键词： ULTRASONIC imaging BACKSCATTERING SHEAR waves coding theory ECHO TRANSDUCERS FERROELECTRICITY

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New (n, r)-Arcs in PG(2,17), PG(2,19), and PG(2,23)

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PROBLEMS OF INFORMATION TRANSMISSION 2011年第3期47卷 217-223页

作者： Daskalov, R. Metodieva, E. Department of Mathematics Technical University of Gabrovo Gabrovo Bulgaria

An (n, r)-arc is a set of n points of a projective plane such that some r but no r+1 of them are collinear. The maximum size of an (n, r)-arc in PG(2, q) is denoted by mr(2, q). In this paper a new (95, 7)-arc, (183, 12)-arc, and (205, 13)-arc in PG(2, 17) are constructed, as well as a (243, 14)-arc and (264, 15)-arc in PG(2, 19). Likewise, good large (n, r)-arcs in PG(2, 23) are constructed and a table with bounds on mr(2, 23) is presented. In this way many new 3-dimensional Griesmer codes are obtained. The results are obtained by nonexhaustive local computer search.

关键词： PROJECTIVE planes coding theory GALOIS theory VECTOR spaces INVARIANT subspaces

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The inverse of circulant matrix

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APPLIED MATHEMATICS AND COMPUTATION 2011年第21期217卷 8495-8503页

作者： Lin Fuyong Huaqiao Univ Dept Mech Quanzhou 361021 Fujian Peoples R China

A direct method is proposed to get the inverse matrix of circulant matrix that find important application in engineering, the elements of the inverse matrix are functions of zero points of the characteristic polynomial g(z) and g'(z) of circulant matrix, four examples to get the inverse matrix are presented in the paper. (C) 2011 Elsevier Inc. All rights reserved.

关键词： Circulant matrix Inverse matrix Linear equation Circulant structure coding theory

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An information theoretic approach to generating fuzzy hypercubes for if-then classifiers

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JOURNAL OF INTELLIGENT & FUZZY SYSTEMS 2011年第1期22卷 33-52页

作者： Makrehchi, Masoud Kamel, Mohamed S. Thomson Reuters Corp Eagan MN 55102 USA Univ Waterloo Pattern Anal & Machine Intelligence Lab Dept Elect & Comp Engn Waterloo ON N2L 3G1 Canada

In this paper, a framework for automatic generation of fuzzy membership functions and fuzzy rules from training data is proposed. The main focus of this paper is designing fuzzy if-then classifiers;however the proposed method can be employed in designing a wide range of fuzzy system applications. After the fuzzy membership functions are modeled by their supports, an optimization technique, based on a multi-objective real coded genetic algorithm with adaptive cross over and mutation probabilities, is implemented to find near optimal supports. Employing interpretability constraint in parameter representation and encoding, we ensure that the generated fuzzy membership function does have a semantic meaning. The fitness function of the genetic algorithm, which estimates the quality of the generated membership functions, consists of two elements: (i) the Shannon entropy and mutual information measures to measure diversity of the data distribution in a hypercube;and (ii) the number of generated fuzzy rules addressing the measure of compactness of the fuzzy system. Finally membership functions are tuned to yield optimal classifier hypercubes, which represent the predictivity and discriminating power of the classifier. Fuzzy rules of the classifier are derived from the optimal hypercubes. Using the proposed approach to designing fuzzy if-then classifiers, we are also able to evaluate the generated membership functions and compare the results with that of other techniques which have been previously reported in the literature. Using the experimental result, we show that the proposed approach outperforms other techniques in low resolutions. It means that the proposed approach can achieve satisfying result with lower complexity.

关键词： INFORMATION theory FUZZY hypergraphs COMBINATORIAL optimization GENETIC algorithms coding theory DATA distribution FUZZY logic EXPERIMENTAL design

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Directional lifting wavelet and universal trellis-coded quantisation-based image coding algorithm and objective quality evaluation

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IET IMAGE PROCESSING 2011年第8期5卷 693-702页

作者： Hou, X. Jiang, G. Ji, R. Shi, C. Xi An Jiao Tong Univ Sch Elect & Informat Engn Xian 710049 Peoples R China Xian Inst Elect Engn Xian 710100 Peoples R China

In this study, an image coding algorithm based on directional lifting wavelet transform (DLWT) and universal trellis-coded quantisation (UTCQ) is presented, and the coding performance is evaluated with three objective image quality metrics. Compared to the discrete wavelet transform, DLWT performing prediction and update along the direction of the local region can provide an efficient representation of edges in images, but shows a similar ability in representing the smooth region. To further improve the visual quality of the smooth background regions, UTCQ is adopted to quantising the wavelet coefficients. The proposed algorithm is measured with not only the dominant peak signal-to-noise ratio (PSNR), but also new metrics multi-scale structural similarity index measure (MSSIM) and visual information fidelity (VIF) which provide a better approximation to the perceived image quality than PSNR by taking the property of human visual system (HVS) into account. Experimental results show that the proposed algorithm has the best MSSIM and VIF performance among the compared algorithms (including JPEG2000) for the typical test images, and its decoded images at low bit-rate are visually more appealing in both edges and smooth background regions. For image Barbara, the proposed algorithm outperforms JPEG2000 up to 24.63% relatively in VIF and 1.93 dB in PSNR at 0.5 bpp, at most 3.62% relatively in MSSIM at 0.125 bpp. The experimental results also show that UTCQ does perform better than scalar quantisation (SQ) in MSSIM and VIF and improves the subjective visual quality, although UTCQ is not necessarily better than SQ in PSNR.

关键词： IMAGING systems -- Image quality WAVELETS (Mathematics) coding theory COMPUTER algorithms SIGNAL-to-noise ratio APPROXIMATION theory BIOMEDICAL materials -- Imaging compatibility

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