In this paper, we propose a joint contention-based bandwidth request mechanism for WiMAX two-hop relay networks. For this purpose, we considered contention by message and code mechanisms. These are normally deployed i...
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In this paper, we propose a joint contention-based bandwidth request mechanism for WiMAX two-hop relay networks. For this purpose, we considered contention by message and code mechanisms. These are normally deployed in single-hop networks. This message scheme suffers from low contention efficiency and higher access delay when the number of mobile stations (MSs) in the network increases. Conversely, this code technique undergoes transmission failure due to the inappropriate setting of the detection threshold at relay stations (RSs). However, these message and code mechanisms are advantageous when they are carried out at appropriate hops. Among the four possible options created by combining the message and code methods, the message requests from MS to RS and code requests from RS to base stations (BSs) performed better than other possible combinations. Using a comprehensive case study and simulation results, we generated signaling examples that confirmed the significance of the proposed method in terms of signaling overhead, network throughput, connection delay and queuing size. (C) 2012 Elsevier Ltd. All rights reserved.
Containment atmosphere mixing is an important nuclear power safety issue related to hydrogen explosion risk. Extensive experimental and numerical research effort has been applied to this issue internationally, includi...
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Containment atmosphere mixing is an important nuclear power safety issue related to hydrogen explosion risk. Extensive experimental and numerical research effort has been applied to this issue internationally, including several international standard problems. One of the findings was that containment atmosphere mixing using lumped-parameter codes common in the safety analyses is complicated due to limitations inherent in the lumped-parameter method. However, it was also found, that in the cases when the user had selected appropriate nodalisation schemes, results obtained with the lumped-parameter codes were satisfactory. The paper presents simulations of one of the containment atmosphere mixing experiments - MISTRA M5 (formation of stratified conditions by a jet/plume steam release and vertical thermal gradient) - performed using a lumped-parameter code COCOSYS. Special nodalisation features required to compensate for the method limitations are described and used. Additionally, an uncertainty and sensitivity analysis of the simulation is presented. The parameters with large uncertainties having high influence on the results are identified. The importance of an adequate nodalisation to account for the occurring processes, e.g., in this case, plume/jet releases, is showed. (C) 2013 Elsevier B.V. All rights reserved.
An error bit rate (EBR) analysis of digital image watermarking is proposed based on information theory. The relationship between watermarking capacity and EBR is also discussed. Two watermarking communication models a...
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An error bit rate (EBR) analysis of digital image watermarking is proposed based on information theory. The relationship between watermarking capacity and EBR is also discussed. Two watermarking communication models are established for the EBR analysis of digital image watermarking. In the watermarking communication models, channel coding is introduced to transmit digital watermark in the watermarking channel. Another concept, watermark payload capacity, is introduced. EBR of watermarking will keep a lower lever if its payload capacity is less than the channel capacity. (C) 2012 Elsevier Ltd. All rights reserved.
The validation of thermal hydraulic system codes like TRACE is a demanding and highly needed task for the nuclear engineering community. In the present paper the validation of TRACE is focused on the heat transfer enh...
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The validation of thermal hydraulic system codes like TRACE is a demanding and highly needed task for the nuclear engineering community. In the present paper the validation of TRACE is focused on the heat transfer enhancement models for spacer grids. Several test sections are selected for that purpose whereas several coolants, different rod arrangements and dimensions, and various thermal hydraulic boundary conditions are considered. The systematic evaluation by means of post-test calculations shows that the present TRACE model is well able to represent the magnitude of the heat transfer enhancement directly at the spacer grid. Nevertheless, improvements of the model were necessary in order to catch the enhancement downstream of the spacer grid. With the present model, the exponential decay of the enhancement is over estimated. The comparison with experimental data suggests a faster establishment of the fully developed flow. Adjustments to the model are done in order to represent the data correctly in terms of magnitude and duration. (C) 2013 Elsevier B.V. All rights reserved.
A new class of subcodes in rank metric is proposed;based on it, multicomponent network codes are constructed. Basic properties of subspace subcodes are considered for the family of rank codes with maximum rank distanc...
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A new class of subcodes in rank metric is proposed;based on it, multicomponent network codes are constructed. Basic properties of subspace subcodes are considered for the family of rank codes with maximum rank distance (MRD codes). It is shown that nonuniformly restricted rank subcodes reach the Singleton bound in a number of cases. For the construction of multicomponent codes, balanced incomplete block designs and matrices in row-reduced echelon form are used. A decoding algorithm for these network codes is proposed. Examples of codes with seven and thirteen components are given.
A direct method is proposed to get the solution of linear systems of equations with circulant-like coefficient matrices that find important application in engineering, the elements of solutions are functions of zero p...
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A direct method is proposed to get the solution of linear systems of equations with circulant-like coefficient matrices that find important application in engineering, the elements of solutions are functions of zero points of the characteristic polynomial g(z) and g'(z) of circulant matrix, three examples to get the inverse matrix, and the solutions of linear system are presented in the paper. (C) 2013 Elsevier Inc. All rights reserved.
In Network-on-Chip (NoC) based multi-core platforms, Distributed Shared Memory (DSM) preferably uses virtual addressing in order to hide the physical locations of the memories. However, this incurs performance penalty...
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In Network-on-Chip (NoC) based multi-core platforms, Distributed Shared Memory (DSM) preferably uses virtual addressing in order to hide the physical locations of the memories. However, this incurs performance penalty due to the Virtual-to-Physical (V2P) address translation overhead for all memory accesses. Based on the data property which can be either private or shared, this paper proposes a hybrid DSM which partitions a local memory into a private and a shared part. The private part is accessed directly using physical addressing and the shared part using virtual addressing. In particular, the partitioning boundary can be configured statically at design time and dynamically at runtime. The dynamic configuration further removes the V2P address translation overhead for those data with changeable property when they become private at runtime. In the experiments with three applications (matrix multiplication, 2D FFT, and H.264/AVC encoding), compared with the conventional DSM, our techniques show performance improvement up to 37.89%. (C) 2012 Elsevier Ltd. All rights reserved.
A two-level batch chromosome coding scheme is proposed to solve the lot splitting problem with equipment capacity constraints in flexible job shop scheduling, which includes a lot splitting chromosome and a lot schedu...
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A two-level batch chromosome coding scheme is proposed to solve the lot splitting problem with equipment capacity constraints in flexible job shop scheduling, which includes a lot splitting chromosome and a lot scheduling chromosome. To balance global search and local exploration of the differential evolution algorithm, a hybrid discrete differential evolution algorithm (HDDE) is presented, in which the local strategy with dynamic random searching based on the critical path and a random mutation operator is developed. The performance of HDDE was experimented with 14 benchmark problems and the practical dye vat scheduling problem. The simulation results showed that the proposed algorithm has the strong global search capability and can effectively solve the practical lot splitting problems with equipment capacity constraints.
First order approximation in standard perturbation theory has been used for the safety analysis of Indian prototype fast breeder reactor (PFBR). Material void and Doppler worth distribution obtained with first order a...
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First order approximation in standard perturbation theory has been used for the safety analysis of Indian prototype fast breeder reactor (PFBR). Material void and Doppler worth distribution obtained with first order approximation has been used to find the response of PFBR core during reactivity transients like unprotected loss of flow accident (ULOFA) and unprotected transient over power accident (UTOPA) up to sodium voiding. The validity of first order approximation applied to larger perturbations during such accidents has been tested by developing an exact perturbation code PERTX. 2D diffusion code ALCIALMI and ABBN-93 evaluated nuclear data has been used for the analysis. European Reactor Analysis Optimized Calculation System (ERANOS) is a code system used for reliable neutronic calculations of current and advanced fast reactor cores. The results of perturbation analysis of PFBR done with IGCAR code systems have been compared with those obtained with ERANOS 2.1 and JEFF 3.1 nuclear data. The present study reveals the adequacy of the IGCAR perturbation methods in 2D for the safety analysis of PFBR core involving transients with fuel, structure and coolant temperatures change. (C) 2012 Elsevier B.V. All rights reserved.
Multidimensional multiphysics analysis of TRISO-coated particle fuel using the BISON finite element nuclear fuels code is described. The governing equations and material models applicable to particle fuel and implemen...
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Multidimensional multiphysics analysis of TRISO-coated particle fuel using the BISON finite element nuclear fuels code is described. The governing equations and material models applicable to particle fuel and implemented in BISON are outlined. Code verification based on a recent IAEA benchmarking exercise is described, and excellent comparisons are reported. Multiple TRISO-coated particles of increasing geometric complexity are considered. The code's ability to use the same algorithms and models to solve problems of varying dimensionality from 1D through 3D is demonstrated. The code provides rapid solutions of 10 spherically symmetric and 2D axially symmetric models, and its scalable parallel processing capability allows for solutions of large, complex 3D models. Additionally, the flexibility to easily include new physical and material models and straightforward ability to couple to lower length scale simulations makes BISON a powerful tool for simulation of coated-particle fuel. Future code development activities and potential applications are identified. (C) 2013 Elsevier B.V. All rights reserved.
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