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.
Some results of a numerical analysis of the serious unanticipated accident at the Fukishima-1 NPP are presented. The analysis was performed in March 2011 as part of the support given by Rosatom, including in making de...
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Some results of a numerical analysis of the serious unanticipated accident at the Fukishima-1 NPP are presented. The analysis was performed in March 2011 as part of the support given by Rosatom, including in making decisions about possible protection of the population in the Far East region of Russia. On the basis of calculations performed with the SOKRAT code, the state of the core during the first week and the possible reasons of the explosions in the first three power units were evaluated: the core of all three reactors melted and in course of its degradation from 950 to 1100 kg of hydrogen could have been formed followed by the formation of a burning mixture. The computational data on hydrogen emission due to oxidation of the melt by steam agree with experiments performed with the QUENCH and PARAMETR facilities. It can be asserted 1.5 years after the accident that post-accident studies confirm the main results of the real-time calculations.
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.
As the size of large-scale computer systems increases, their mean-time-between-failures are becoming significantly shorter than the execution time of many current scientific applications. Fault-tolerant parallel algor...
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As the size of large-scale computer systems increases, their mean-time-between-failures are becoming significantly shorter than the execution time of many current scientific applications. Fault-tolerant parallel algorithm (FTPA) is an application-level fault-tolerant approach that can achieve fast self-recovery by parallel recomputing. The method of parallelizing the loops has been used to design the parallel recomputing code for FTPA in our prior work. In the present paper, we first propose a new parallel recomputing code design methodology. Second, the parallel recomputing code design methodology is automated by exploring the use of compiler technology. Finally, we evaluate the performance of our approach with five programs on Tianhe-1A. The experimental results show that the parallel recomputing code generated by the new method has a higher efficiency of parallel recomputing. (C) 2013 Elsevier Ltd. 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.
We derive a lower bound on the secrecy capacity of a compound wiretap channel with channel state information at the transmitter which matches the general upper bound on the secrecy capacity of general compound wiretap...
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We derive a lower bound on the secrecy capacity of a compound wiretap channel with channel state information at the transmitter which matches the general upper bound on the secrecy capacity of general compound wiretap channels given by Liang et al. [1], thus establishing a full coding theorem in this case. We achieve this with a stronger secrecy criterion and the maximum error probability criterion, and with a decoder that is robust against the effect of randomization in the encoding. This relieves us from the need of decoding the randomization parameter, which is in general impossible within this model. Moreover, we prove a lower bound on the secrecy capacity of a compound wiretap channel without channel state information and derive a multiletter expression for the capacity in this communication scenario.
This study developed a framework for the shape optimization of aerodynamics profiles using computational fluid dynamics (CFD) and genetic algorithms. Agenetic algorithm code and a commercial CFD code were integrated t...
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This study developed a framework for the shape optimization of aerodynamics profiles using computational fluid dynamics (CFD) and genetic algorithms. Agenetic algorithm code and a commercial CFD code were integrated to develop a CFD shape optimization tool. The results obtained demonstrated the effectiveness of the developed tool. The shape optimization of airfoils was studied using different strategies to demonstrate the capacity of this tool with different GA parameter combinations.
In this paper, we built up a simplified model of the Passive Containment Cooling System in a CFD code, including a steel plate, a condensing channel and an evaporating channel. In the inner side of the plate, the cond...
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In this paper, we built up a simplified model of the Passive Containment Cooling System in a CFD code, including a steel plate, a condensing channel and an evaporating channel. In the inner side of the plate, the condensing channel is supposed to be the source of heat transfer into the steel plate. Along the outer side, an evaporating falling film is used to extract the heat from the steel plate. Upward flow of air is also considered along the evaporating film. In the condensing channel, a flow solver based on an asymptotic model of the Navier-Stokes equations at the low Mach number regime and two turbulence models (Buleev's model and Chien's k-epsilon model) are considered. The condensing channel model was used to model the COPAIN test, the computed heat flux and condensation rate were compared with the experimental data. In the evaporating channel, a simplified model developed by Aiello and Ciofalo (2009) was used, which considered the heat and mass balance between the falling film and the ascending air flow. The model was validated for two cases: a dry wall case and a completely wet wall case. In the former case, the results were compared with 20 predictions obtained by using the CFX-4 CFD code. In the latter case, the results were compared with experimental data obtained by Kang and Park. The comparison showed a satisfactory agreement on heat transfer rates, despite some overprediction depending on the air velocity. At the end, the condensing channel model and the evaporating channel model were coupled by the steel plate to establish the complete model for the PCCS. In the absence of relative tests, a case with general parameter values was implemented in the complete model. (C) 2013 Elsevier BM. All rights reserved.
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