In computational astrophysics, the effect of gravity is essential even with very heavy computation of O(N2) for N particles. Several special purpose machines have been implemented as gravity engine to handle this prob...
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ISBN:
(纸本)0769523129
In computational astrophysics, the effect of gravity is essential even with very heavy computation of O(N2) for N particles. Several special purpose machines have been implemented as gravity engine to handle this problem extremely fast, however there are few sites in the world to operate such systems. We have developed a grid environment to access such a system based on grid-RFC, named HMCS-G. Using HMCS-G, a multi-physical computational astrophysics simulation can be performed with the combination of a PC-cluster and the gravity engine GRAPE-6. In typical size of problems for galaxy formation, however, the computation power of PC-cluster is much weaker than that of GRAPE-6, and we need multiple sets of PC-clusters to share the power of GRAPE-6 on grid environment. We have developed such a system using OmniRPC, a grid-enabled RPC system. In this system, OmniRPC are used both to distribute jobs for parameter search on multiple PC-clusters and to access GRAPE-6 server from these clusters. We performed an actual problem to search several formations of galaxy on this system, and confirmed such a solution is useful for wide variety of computational astrophysics research.
In neural networks based on a distributed information representation, when different patterns are to be recalled from the same input by association depending on the context, the usual method is to concatenate the patt...
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This paper addresses the dynamic location management for personal communication service (PCS) networks with consideration of mobility patterns. The popular hexagonal cellular architecture is considered. In this paper,...
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In a core disruptive accident (CDA) of a Fast Breeder Reactor, the post accident heat removal (PAHR) is crucial for the accident mitigation. The molten core material should be solidified in the sodium coolant in the r...
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In a core disruptive accident (CDA) of a Fast Breeder Reactor, the post accident heat removal (PAHR) is crucial for the accident mitigation. The molten core material should be solidified in the sodium coolant in the reactor vessel. In the present experiment, molten material is injected into water to experimentally obtain fragments and the visualized information of the fragmentation. The distributed particle behaviour of the molten material jet is observed with high-speed video camera. The distributions of the fragmented droplet diameter from the molten material jet are evaluated by correcting the solidified particles. The experimental results of the mean fragmented droplet diameter are compared with the existing theories. Consequently, the fragmented droplet diameter is close to the value estimated based on the Kelvin-Helmholtz instability. Once the particle diameter of the fragmented molten,material could be known from a hydrodynamic model, it becomes possible to estimate the mass ratio of the molten particle to the total injected mass by combining an appropriate heat transfer model The mass ratio of the molten fragment to total mass of the melted mixed oxide fuel in sodium coolant estimated in the present study is very small. The result means that most of the molten mixed oxide fuel material injected into the sodium coolant can be cooled down under the solidified temperature, if the amount of the coolant is sufficient.
The purpose of this paper is to suggest new 3-D N-link system movement simulator. Previous presented method used to "Jacobian" matrix for connecting between the work space coordination and the angle state sp...
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ISBN:
(纸本)0780384636
The purpose of this paper is to suggest new 3-D N-link system movement simulator. Previous presented method used to "Jacobian" matrix for connecting between the work space coordination and the angle state space for representing the whole N-link system. But this system has difficulties for simulating the whole dynamics of the general N-link system from the side of computational cost and the precision of the calculations. The major reasons depend on the fundamental principle of conversion equivalence between the work space coordination q&rarr, and the angle state space x &rarr this principle assure that we can change the work space coordinate into the angle state space coordinate which is convenient for the calculation, but this conversion have singularity - that is, there is no inverse matrix of "J". In addition, there is accumulation of calculation error when it follows from the link root to link end in the case of calculating the multi-joint link movement dynamics, and the problem of treating the external force into the angular space dynamics. In this study, we consider the N-link system as N-particle movement system. And each of the particles is connected by a kind of spring damper model in imitation of a link. Because of this, our proposed method has no coordinate conversion between work space and angular space in the dynamics simulation. And by the way of introducing some dynamics restriction, we can construct many of joint features such as fixed joint or single revolute joint, spherical link and so on. And we confirmed the 3D N-link system performance through some dynamics simulation such as walking, this simulator shows good accuracy and computational cost performances comparing previous proposed N-link system simulator.
作者：
Md. Mizanur RahmanDoctoral Student
Agricultural and Aquatic Systems and Engineering Program Asian Institute of Technology (AIT) Pathumthani Thailand. E-mail:
Mobile IP is the current standard for supporting global mobility, however the performance degrades to support micro mobility. Cellular IP could be a good solution to accommodate efficiently hundreds of, thousands of m...
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Mobile IP is the current standard for supporting global mobility, however the performance degrades to support micro mobility. Cellular IP could be a good solution to accommodate efficiently hundreds of, thousands of mobile hosts that perform fast and frequent handoff in a small local area network. In semisoft handoff of cellular IP, a mobile host sends a semisoft packet to the new base station before performing actual handoff to guarantee that the routing cache mapping associated with the new base station is created before actual handoff takes place. But packet loss and handoff delay are still occurred by this model. We propose an advanced semisoft handoff method with no packet loss but with additional small packet delay just before or after handoff. In this method, the cross-over node calculates the time for the last message to be delivered to the mobile host via the old base station just before handoff based on four typical network models. On receiving that packet, the mobile host performs handoff to the new base station. Our simulation experiment results show that the proposed semisoft handoff method actually outperforms the traditional semisoft handoff method in both handoff packet loss and handoff delay. We study the performance of the advanced semisoft handoff method with the network models.
We have developed a hybrid computing system named HMCS-G (Grid-enabled Heterogeneous Multi-Computer System) which combines multiple cluster systems and a special purpose machine for gravity calculations. The purpose o...
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We have developed a hybrid computing system named HMCS-G (Grid-enabled Heterogeneous Multi-Computer System) which combines multiple cluster systems and a special purpose machine for gravity calculations. The purpose of HMCS-G is to provide ideal computation environment for computational astrophysics, which requires multiple physics phenomena for precise and detailed simulation. There are two categories of machines required for this system, that is, multiple PC-clusters for general purpose computation such as hydro-dynamics and a special purpose machine GRAPE-6 which calculates gravity for all pairs of particles in the system with very high-speed. These systems are connected with a grid-RPC named OmniRPC which supports Globus and ssh for authentication. Our HMCS-G enables the worldwide access to GRAPE-6 cluster which provides several TFLOPS performance for gravity calculation. All participating PC-clusters share this resource in time sharing manner with grid technology. For efficient usage of GRAPE-6 resource, we modified the original server cluster of it for multiple clients running in various network environment. Currently, precise simulations on galaxy formation are being performed on clusters in several institutes with smoothed particle hydrodynamics and radiative transfer under complete gravity calculation, as the first real application on HMCS-G.
In this paper we consider a method for finding several eigenvalues and corresponding eigenvectors of large-scale generalized eigenvalue problems. In this method, a small matrix pencil that has only the desired eigenva...
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Reconfigurable architecture for the probabilistic neural network (PNN) is proposed and the PNN hardware system is developed using FPGAs. In the system, preprocessing circuits as well as the PNN can be reconfigured ada...
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Reconfigurable architecture for the probabilistic neural network (PNN) is proposed and the PNN hardware system is developed using FPGAs. In the system, preprocessing circuits as well as the PNN can be reconfigured adapting each task. Potential performance of the PNN cannot be brought out until the total reconfigurability including the preprocessing is achieved. The developed system shows high recognition accuracy with high processing speed for some image recognition tasks.
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