Norihiro Nakajima

Toward an international sparse linear algebra expert system by interconnecting the ITBL computational Grid with the Grid-TLSE platform

Complex optimization problems are of high interest for Process Systems Engineering. The selection of the relevant technique for the treatment of a given problem has already been studied for batch plant design issues. Classically, most works reported in the dedicated literature yet considered item sizes as continuous variables. In a view of realism, a similar approach is proposed in this paper, with discrete variables for representing equipment capacities, which leads to a combinatorial problem. For this purpose, a Genetic Algorithm was used, which is multiparametric by nature and a grid approach is perfectly relevant to this case study, since the GA code must be run several times, with different values of some input parameters, to guarantee its stochastic nature. This paper is devoted to the presentation of a grid-oriented GA methodology. Some significant results are highlighted and discussed.In the present paper, the methodology of interoperability between ITBL and Grid-TLSE is described. Grid-TLSE is an expert web site to provides user assistance in choosing the right solver for its problems and appropriate values for the control parameters of the selected solve. The time to solution of linear equation solver strongly depends on the type of problem, the selected algorithm, its implementation and the target computer architecture. Grid-TLSE uses the Diet middleware to distribute computing tasks over the Grid. Therefore, extending the variety of computer architecture by Grid middleware interoperability between Diet and ITBL has a beneficial impact to the expert system. To show the feasibility of the methodology, job transfering program as a special service of Diet was developed.

Development of Three-Dimensional Virtual Plant Vibration Simulator on Grid Computing Environment ITBL-IS/AEGIS

Center for computational science and e-systems of Japan Atomic Energy Agency is carrying out R&D in the area of extra large-scale simulation technologies for solving nuclear plant structures in its entirety. Specifically, we focus on establishing a virtual plant vibration simulator on interconnected supercomputers intended for seismic response analysis of a whole nuclear plant. The simulation of the whole plant is a very difficult task because an extremely large dataset must be processed. To overcome this difficulty, we have proposed and implemented a necessary simulation framework and computing platform. The simulation framework based on the computing platform has been applied to a linear elastic analysis of the reactor pressure vessel and cooling systems of a nuclear research facility, the HTTR. The simulation framework opens a possibility of new simulation technologies for building a whole virtual nuclear plant in computers for virtual experiments.Copyright

Component-Wise Meshing Approach and Evaluation of Bonding Strategy on the Interface of Components for Assembled Finite Element Analysis of Structures

The finite elements are extensively utilized to solve various problems in engineering fields with the growth of computing technologies. However, there is a lack of methodology for analyses of huge assembled structures. The mechanics on the interface of each components, for instance, contact, bolt joint and welding in assembly is a key issue for important huge structure such as nuclear power plants. On the other hand, it is well known that as finite element models become large and complex, construction of detailed mesh becomes a bottleneck in the CAE procedures. To solve these problems, the authors would like to introduce component-wise meshing approach and bonding strategy on the interface of components. In order to assemble component-wise meshes, the penalty method is introduced not only to constrain the displacements, but also to introduce classical spring connection on the joint interface, although penalty method is claimed that it is not suitable for iterative solver. In this paper, the convergence performance of an iterative solver with penalty method is investigated and the detailed component-wise distributed computation scheme is described with numerical examples.

Interoperability between UNICORE and ITBL

The interoperability among different science grid systems is indispensable to worldwide use of a large-scale experimental facility as well as a large-scale supercomputer. One of the simplest ways to achieve the interoperability is to convert message among different science grid systems without modifying themselves. Under such consideration, the interoperability between UNICORE and ITBL (IT-Based Laboratory) has been achieved without modifying these grid systems by adopting a connection server which works as a mediator. Until international standardization is established, the method of message conversion among different science grid systems is promising as a way to establish the interoperability.

Shape Optimization Using an Adjoint Variable Method in ITBL Grid Environment

To decrease the fluid drag force on the surface of a specified object subjected to an unsteady flow, under a constant volume condition, the adjoint variable method is formulated by using FEM. Based on the Lagrange multiplier method (a conditional variational principle), this method consists of the state equation, the adjoint equation and the sensitivity equation. To solve the equations effectively using the steepest descent method, a parallel algorithm that finds the Armijos line-search step size is constructed. The shape optimization code for solving a large scale 3D problem using a parallel algorithm was implemented on ITBL using the HPC-MW library. Results show that, by using shape optimization, the fluid drag force on the object can be reduced by about 17.5%. (authors)

A Parametric Study for the Seismic Response Analysis of a Nuclear Reactor Building by Using a Three-Dimensional Finite Element Model

Research and development of three-dimensional vibration simulation technologies for nuclear facilities is one mission of the Center for Computational Science and e-Systems of the Japan Atomic Energy Agency (JAEA). A seismic intensity of upper 5 was observed in the area of High-Temperature Engineering Test Reactor (HTTR) at the Oarai Research and Development Center of JAEA during the 2011 Tohoku earthquake. In this paper, we report a seismic response analysis of this earthquake using three-dimensional models of the HTTR building. We performed a parametric study by using uncertainty parameters. Furthermore, we examined the variation in the response result for the uncertainty parameters to create a valid 3D finite element model.Copyright

Structural Analysis for Assembly by Integrating Parts

Almost all industrial products are assembled from multiple parts, and this is true for all sizes of products. As an example, a nuclear facility is a large structure consisting of more than 10 million components. This paper discusses a method to analyze an assembly by gathering data on its component parts. Gathered data on component may identify ill conditioned meshes for connecting surfaces between components. These ill meshes are typified by nodal point disagreement in finite element discretization. A technique to resolve inconsistencies in data among the components is developed. By using this technique, structural analysis for an assembly can be carried out, and results can be obtained by the use of supercomputers, such as the K computer. Numerical results are discussed for components of the High Temperature Engineering Test Reactor of the Japan Atomic Energy Agency.© 2014 ASME

R&D of Validity Evaluation System for Seismic Simulation of Entire Nuclear Plant

Our goal is to evaluate validity of numerical simulation results in the nuclear field in order to estimate real behavior of nuclear plants and thus to contribute their security and safety. Recently, it becomes possible to execute a full-scale numerical simulation under a real condition, such as a seismic behavior of entire nuclear plant. To estimate real behavior accurately by such simulations, it is indispensable to evaluate validity of simulation results because numerical simulations include various uncertainties such as “uncertainty due to randomness” and “uncertainty due to lack of knowledge”. As one of approaches to evaluate validity of simulation results, we introduce “the degree of certainty” of simulations to real behavior. Here, to get a more accurate degree of certainty, we try to confirm the degree of influence about unevenness of uncertainty and to reduce uncertainty due to lack of knowledge. For this, we research and develop a validity evaluation system composed of three tools. One is a tool able to introduce the degree of certainty from various uncertainties to put together various uncertainties. Another is a tool able to analyze the sensitivity of each uncertainty to whole uncertainty. Moreover, we research a tool able to analyze factors of various uncertainties. We have applied them to our seismic simulation system which enables to execute the assembly structure analysis of an entire nuclear plant and confirmed that their functions are applicable to the simulation.© 2012 ASME

Development of Cognitive Methodology based Data Analysis System

Nuclear engineering is an integrated engineering field of mechanical and civil engineering, partical physics as well as fluid and thermodynamics. Researchers in nuclear engineering fields need to treat extensive physical and engineering information obtained through theories, simulations, experiments and observations in order to promote a nuclear technology safely and securely. To meet the need, the Cognitive methodology-based Data Analysis System (CDAS) which equips information technologies that have recognition abilities similar to those of humans has been developed. The system supports researchers to analyze numerical simulation data by using extensive scientific knowledge. In the present study, information technology is developed for performing these processes and for configuring systems. In addition, a prototype system has been constructed using this information technology and an application experiment using a virtual plant vibration simulator has been performed to confirm the implementability of the system. The results obtained demonstrate that the CDAS enables researchers to dynamically set essential functions for evaluation and judgment, enabling them to readily extract meaningful and reliable information from large-scale data of up to 1 TB.

Interoperation between Atomic Energy Grid Infrastructure (AEGIS) and Other Grids

Coordination of global knowledge is needed to advance the computational and computer science needed for nuclear research. We have been conducting cooperative international research in various fields to construct a highly-secure worldwide network computing infrastructure, based on the Atomic Energy Grid Infrastructure (AEGIS). A promising way to achieve this is to establish interoperation using AEGIS with other grids. The operation of existing grid environments that allow the continuous development and execution of user applications is critical. To achieve the interoperability while maintaining operations, we have developed a system that converts messages among different grid middlewares without requiring modification of grid middlewares. To realize interoperability with two or more grid middlewares in the present study, we have defined the application programming interface (API) as a common interface to convert messages among the grid middlewares. We have applied our system to three interoperable environments. Through these experiments, we have confirmed that our system is applicable to the construction of interoperable environments among various grid middlewares.