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Journal Articles

Design for detecting recycling muon after muon-catalyzed fusion reaction in solid hydrogen isotope target

Okutsu, Kenichi*; Yamashita, Takuma*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 170, p.112712_1 - 112712_4, 2021/09

A muonic molecule which consists of two hydrogen isotope nuclei (deuteron (d) or tritium (t)) and a muon decays immediately via nuclear fusion and the muon will be released as a recycling muon, and start to find another hydrogen isotope nucleus. The reaction cycle continues until the muon ends up its lifetime of 2.2 $$mu$$s. Since the muon does not participate in the nuclear reaction, the reaction is so called a muon catalyzed fusion ($$mu$$CF). The recycling muon has a particular kinetic energy (KE) of the muon molecular orbital when the nuclear reaction occurs. Since the KE is based on the unified atom limit where distance between two nuclei is zero. A precise few-body calculation estimating KE distribution (KED) is also in progress, which could be compared with the experimental results. In the present work, we observed recycling muons after $$mu$$CF reaction.

Journal Articles

Time evolution calculation of muon catalysed fusion; Emission of recycling muons from a two-layer hydrogen film

Yamashita, Takuma*; Okutsu, Kenichi*; Kino, Yasushi*; Nakashima, Ryota*; Miyashita, Konan*; Yasuda, Kazuhiro*; Okada, Shinji*; Sato, Motoyasu*; Oka, Toshitaka; Kawamura, Naritoshi*; et al.

Fusion Engineering and Design, 169, p.112580_1 - 112580_5, 2021/08

A muon ($$mu$$) having 207 times larger mass of electron and the same charge as the electron has been known to catalyze a nuclear fusion between deuteron (d) and triton (t). These two nuclei are bound by $$mu$$ and form a muonic hydrogen molecular ion, dt$$mu$$. Due to the short inter-nuclear distance of dt$$mu$$, the nuclear fusion, d +t$$rightarrow alpha$$ + n + 17.6 MeV, occurs inside the molecule. This reaction is called muon catalyzed fusion ($$mu$$CF). Recently, the interest on $$mu$$CF is renewed from the viewpoint of applications, such as a source of high-resolution muon beam and mono-energetic neutron beam. In this work, we report a time evolution calculation of $$mu$$CF in a two-layered hydrogen isotope target.

Journal Articles

Data-driven derivation of partial differential equations using neural network model

Koyamada, Koji*; Yu, L.*; Kawamura, Takuma; Konishi, Katsumi*

International Journal of Modeling, Simulation, and Scientific Computing, 12(2), p.2140001_1 - 2140001_19, 2021/04

With the improvement of sensors technologies in various fields such as fluid dynamics, meteorology, and space observation, it is an important issue to derive explanatory models using partial differential equations (PDEs) for the big data obtained from them. In this paper, we propose a technique for estimating linear PDEs with higher-order derivatives for spatiotemporally discrete point cloud data. The technique calculates the time and space derivatives from a neural network (NN) trained on the point cloud data, and estimates the derivative term of the PDE using regression analysis techniques. In the experiment, we computed the error of the estimated PDEs for various meta-parameters for the PDEs with exact solutions. As a result, we found that increasing the hierarchy of NNs to match the order of the derivative terms in the exact solution PDEs and adopting L1 regularization with LASSO as the method of regression analysis increased the accuracy of the model.

Journal Articles

Interactive in-situ steering using interactive in-situ visualization framework based on particle

Kawamura, Takuma

Dai-34-Kai Suchi Ryutai Rikigaku Shimpojiumu Koen Rombunshu (Internet), 3 Pages, 2020/12

The search for computational parameters in simulations is an important issue in optimizing design variables and increasing the accuracy of simulations. However, due to the recent improvement in the performance of computational units, the data I/O speed has become a bottleneck, making it difficult to store the calculation results consisting of huge parameters in storage. In this study, we focused on in-situ steering, in which computational parameters are explored simultaneously with the computation on the supercomputer. We have extended our previously developed particle-based interactive in-situ visualization framework to develop a technique for interactively steering the computational parameters of batch-processed simulations. We applied this technique to a real-time simulation under development in our mid-term plan, and showed that the user can optimize the parameter search by adjusting the computational parameters in real time with feedback from the visualization.

Journal Articles

Interactive in-situ steering and visualization of GPU-accelerated simulations using particle-based volume rendering

Kawamura, Takuma; Hasegawa, Yuta; Idomura, Yasuhiro

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.187 - 192, 2020/10

In order to realize the atmospheric dispersion prediction of pollutants, a fluid simulation by adaptive mesh refinement (AMR) optimized for GPU supercomputer has been developed, and interactive visualization and parameter steering of the simulation results are needed. In this study, we extend particle-based in-situ visualization method for structured grids into AMR, and enables in-situ steering of the simulation parameters by utilizing an in-situ control mechanism via files. By combining the developed method with plume dispersion simulation in urban areas running on a GPU platform, it was shown that human-in-the-loop pollution source search is possible without enormous parameter scanning.

Journal Articles

Intuitive interactions for immersive data exploration of numerical simulation results

Tabata, Ginga*; Sakamoto, Naohisa*; Kawamura, Takuma

Proceedings of Joint International Conference on Supercomputing in Nuclear Applications + Monte Carlo 2020 (SNA + MC 2020), p.193 - 200, 2020/10

In interactive visualization/analysis, interactive operation of visualization results on the screen is an important technology that is directly linked to knowledge extraction. On the conventional 2D display, interactive operations such as moving the viewpoint and adjusting the visualization parameters were performed using the mouse. Then, the virtual reality (VR) technology such as CAVE system and head mounted display (HMD) is used for visualization and analysis, and the development of technology for interactively operating visualization result data in VR space has become one of the important issues in the visualization field. In this paper, we propose a technique to capture a real hand gesture by Leap Motion and intuitively change the viewpoint movement and visualization parameters in VR space by HMD. We asked four people to test the developed technology, and obtained a result that it was easy to change the viewpoint from the questionnaire on the operation feeling.

Journal Articles

Improvement in interactive remote in situ visualization using SIMD-aware function parser and asynchronous data I/O

Kawamura, Takuma; Idomura, Yasuhiro

Journal of Visualization, 23(4), p.695 - 706, 2020/08

 Times Cited Count:0 Percentile:0.01(Computer Science, Interdisciplinary Applications)

An in-situ visualization system based on the particle-based volume rendering offers a highly scalable and flexible visual analytics environment based on multivariate volume rendering. Although it showed excellent computational performance on the conventional CPU platforms, accelerated computation on the latest many core platforms revealed performance bottlenecks related to a function parser and particles I/O. In this paper, we develop a new SIMD-aware function parser and an asynchronous data I/O method based on task-based thread parallelization. Numerical experiments on the Oakforest-PACS, which consists of 8208 Intel Xeon Phi7250 (Knights Landing) processors, demonstrate an order of magnitude speedup with keeping improved strong scaling up to $$sim$$ 100 k cores.

Journal Articles

Fuel debris' air cooling analysis using a lattice Boltzmann method

Onodera, Naoyuki; Idomura, Yasuhiro; Kawamura, Takuma; Uesawa, Shinichiro; Yamashita, Susumu; Yoshida, Hiroyuki

Proceedings of 27th International Conference on Nuclear Engineering (ICONE-27) (Internet), 6 Pages, 2019/05

A dry method is one of practical methods for decommissioning the TEPCO's Fukushima Daiichi Nuclear Power Station. Japan Atomic Energy Agency (JAEA) has been evaluating the air cooling performance by using the JUPITER code. However, the JUPITER code requires a large computational cost to capture debris' structures. To accelerate such CFD analyses, we use the CityLBM code, which is based on the lattice Boltzmann method (LBM) and is highly optimized for GPUs. The CityLBM code is validated against free convective heat transfer experiments at JAEA, and the similar accuracy as the JUPITER code is confirmed regarding the prediction capability of heat transfer and the resulting temperature distributions. It is also shown that the elapse time of a CityLBM simulation on GPUs is reduced to 1/6 compared with that of the corresponding JUPITER simulation on CPUs with the same number of GPUs and CPUs. The results show that the LBM is promising for accelerating thermal convective simulations.

Journal Articles

Radiation imaging system using a compact $$gamma$$-ray imager mounted on a remotely operated machine

Sato, Yuki; Kawabata, Kuniaki; Ozawa, Shingo*; Izumi, Ryo*; Kaburagi, Masaaki; Tanifuji, Yuta; Terasaka, Yuta; Miyamura, Hiroko; Kawamura, Takuma; Suzuki, Toshikazu*; et al.

IFAC-PapersOnLine, 50(1), p.1062 - 1066, 2017/07

 Times Cited Count:2 Percentile:67.06

Journal Articles

Performance evaluation of runtime data exploration framework based on in-situ particle based volume rendering

Kawamura, Takuma; Noda, Tomoyuki; Idomura, Yasuhiro

Supercomputing Frontiers and Innovations, 4(3), p.43 - 54, 2017/07

AA2017-0206.pdf:3.74MB

We examine the performance of the in-situ data exploration framework based on the in-situ Particle Based Volume Rendering (In-Situ PBVR) on the latest many-core platform. In-Situ PBVR converts extreme scale volume data into small rendering primitive particle data via parallel Monte-Carlo sampling without costly visibility ordering. This feature avoids severe bottlenecks such as limited memory size per node and significant performance gap between computation and inter-node communication. In addition, remote in-situ data exploration is enabled by asynchronous file-based control sequences, which transfer the small particle data to client PCs, generate view-independent volume rendering images on client PCs, and change visualization parameters at runtime. In-Situ PBVR shows excellent strong scaling with low memory usage up to about 100k cores on the Oakforest-PACS, which consists of 8,208 Intel Xeon Phi7250 (Knights Landing) processors.

Journal Articles

Algebraic design of multi-dimensional transfer function using transfer function synthesizer

Kawamura, Takuma; Idomura, Yasuhiro; Miyamura, Hiroko; Takemiya, Hiroshi

Journal of Visualization, 20(1), p.151 - 162, 2017/02

 Times Cited Count:2 Percentile:17.71(Computer Science, Interdisciplinary Applications)

In this paper, we propose a novel transfer function design interface for multivariate volume rendering. In the conventional multivariate volume rendering, GUI based transfer function design interfaces were limited to two-dimensional variables space. In order to design higher dimensional transfer functions in an interactive and intuitive manner, a Transfer Function Synthesizer (TFS) is developed. On the TFS, multi-dimensional transfer functions are generated by algebraic synthesis of one-dimensional transfer functions, which are designed based on the conventional GUIs or algebraic expressions. The TFS enables not only multivariate volume rendering but also general visualization techniques such as surface visualization and image composition within the framework of volume rendering. The TFS is implemented on the remote visualization system PBVR, and applied to various multivariate scalar volume data generated from nuclear applications.

Journal Articles

In-situ visual exploration of multivariate volume data based on particle based volume rendering

Kawamura, Takuma; Noda, Tomoyuki; Idomura, Yasuhiro

Proceedings of 2nd Workshop on In Situ Infrastructures for Enabling Extreme-scale Analysis and Visualization (ISAV 2016) (Internet), p.18 - 22, 2016/11

 Times Cited Count:7 Percentile:92.55

A novel in-situ online visualization framework is developed based on the Particle Based Volume Rendering (PBVR), which renders multivariate volume data using view-independent particle data. Our online approach enables visualization of particle data with interactive view exploration and changes of multi-dimensional transfer functions at runtime. The runtime visualization show excellent strong scaling up to thousands of cores, and its computational cost is small. These features enable flexible in-situ data exploration for monitoring extreme scale simulations. The utility of the proposed framework is demonstrated by applying it to simulations of molten debris relocation in reactor pressure vessels using the JUPITER code.

Journal Articles

Analyses for designing objects in mechanical design

Nakajima, Norihiro; Miyamura, Hiroko; Kawakami, Yoshiaki; Kawamura, Takuma

Kashika Joho Gakkai-Shi, 35(Suppl.1), p.233 - 238, 2015/07

no abstracts in English

Journal Articles

Open-source remote visualization software PBVR

Kawamura, Takuma

Keisan Kogaku Nabi, Nyusu Reta (Internet), 7, p.4 - 5, 2015/06

It has been difficult for traditional remote visualization systems to explore large-scale data because of bottlenecks such as visualization speed, memory limit, and data transfer time. Remote visualization software PBVR (Particle-Based Volume Rendering) employed client-server system and achieved interactive data exploration by converting the large-scale data to small particle data which is transferred to the client machine. We developed PBVR system as open source code and contributed an article about PBVR system.

Journal Articles

Visualization technique for large-scale data by particle-based volume rendering

Kawamura, Takuma; Idomura, Yasuhiro; Miyamura, Hiroko; Imamura, Toshiyuki*; Takemiya, Hiroshi

Shisutemu Seigyo Joho Gakkai Rombunshi, 28(5), p.221 - 227, 2015/05

However remote volume visualization is important to obtain knowledge from complicated large-scale simulation results on supercomputer, the rendering speed and data transfer speed becomes bottleneck of the conventional Client/Server volume visualization techniques. Client/Server visualization system using particle-based volume rendering enables interactive volume visualization, which converts the original volume data to small size light particle data utilizing the supercomputer and transfer the data to Client PC. This system generated the particle data at a few seconds using parallel process on supercomputer Kei with strong scaling till 1000 processers.

Journal Articles

Remote visualization system based on particle based volume rendering

Kawamura, Takuma; Idomura, Yasuhiro; Miyamura, Hiroko; Takemiya, Hiroshi; Sakamoto, Naohisa*; Koyamada, Koji*

Visualization and Data Analysis 2015 (Proceedings of SPIE Vol.9397) (Internet), p.93970S_1 - 93970S_8, 2015/02

 Times Cited Count:3 Percentile:86.38

In this paper, we propose a novel remote visualization system based on particle-based volume rendering (PBVR), which enables interactive analyses of extreme scale volume data located on remote computing systems. The remote PBVR system consists of Server, which generates particles for rendering, and Client, which processes volume rendering, and the particle data size becomes significantly smaller than the original volume data. Depending on network bandwidth, the level of detail of images is flexibly controlled to attain high frame rates. Server is highly parallelized on various parallel platforms with hybrid programing model. The mapping process is accelerated by two orders of magnitudes compared with a single CPU. The structured and unstructured volume data with 100 millions of cells is processed within a few seconds. Compared with commodity Client/Server visualization tools, the total processing cost is dramatically reduced by using proposed system.

Journal Articles

Multivariate volume rendering using transfer function synthesizer implemented in remote visualization system PBVR

Kawamura, Takuma; Idomura, Yasuhiro; Miyamura, Hiroko; Takemiya, Hiroshi

Proceedings of SIGGRAPH Asia 2015 (SA 2015) (Internet), 4 Pages, 2015/00

In this paper, we propose a novel transfer function design technique for multivariate volume rendering. This technique generates a multidimensional transfer function by logical synthesis of variables and transfer functions. This technique enables analysts to extract correlation of variables and to combine multivariate surface and volume shapes. And this technique is implemented in Remote Visualization System PBVR optimized to several supercomputers. An experiment for the multi-phase fuel melting simulation result in the nuclear energy field shows the powerful ability of this technique enough by extracting complex behavior of molten materials.

Journal Articles

Hands-on seminar of remote visualization system PBVR

Kawamura, Takuma

Proceedings of SIGGRAPH Asia 2015 (SA 2015) (Internet), 2 Pages, 2015/00

This seminar serves as a practical guide to Particle-Based Volume Rendering (PBVR) and its Client-Server system, which is one of a promising technique for large-scale visualization. Remote visualization using Commodity software takes a long time from a few hours to few days because of the explosive increase of the original data or polygon size, however PBVR enables interactive visualization by using pixel-based particle data on the client-server system. PBVR is developed as cross-platform and run on various supercomputers such as K computer, or user PC. Flexible GUI is implemented for analytical visualization for multivariate data. The goal of this course is to learn principle of PBVR and integrated particle-based visualization by using open-source PBVR system through lectures and demonstration.

Journal Articles

2-dimentional visualization technique for exploring region of interest in 4-dimensional data

Miyamura, Hiroko; Kawamura, Takuma; Suzuki, Yoshio; Idomura, Yasuhiro; Takemiya, Hiroshi

Joho Shori Gakkai Rombunshi, 55(9), p.2216 - 2224, 2014/09

In numerical simulations, variations of calculation results with respect to a variable axis are often observed. When the target model is given in 3D, the simulation results become 4D. Such a multi-dimensional dataset given in more than 4D space is analyzed by detailed explorations of regions of interest (ROIs) in multi-dimensional space. However, for high-dimensional and large-scale datasets, this approach requires enormous processing time and effort, and may have difficulty in capturing all the ROIs. Therefore, we propose a technique that is based on a concept of spatiotemporal image. In our technique, a space axis is created by octree, a variable axis is defined in the direction perpendicular to the space axis. Our technique is applied to the results of 3D seismic simulations of a nuclear plant, and regions with characteristic frequency responses of each region are analyzed. Through the analyses, it is demonstrated that our technique can effectively capture ROIs from 4D datasets.

Journal Articles

Remote visualization system based on particle based volume rendering

Kawamura, Takuma; Idomura, Yasuhiro; Miyamura, Hiroko; Takemiya, Hiroshi

Nihon Shimyureshon Gakkai Rombunshi, 6(2), p.15 - 26, 2014/09

In this paper, we propose a novel remote visualization system based on particle-based volume rendering (PBVR). The system consists of a Server, which generates particles (rendering primitives), and a Client, which process volume rendering, and particles are transferred from Server to Client. The size of particle data is determined by the resolution of rendering images, and is significantly smaller than the original volume data. The smallness of the particle data is useful also for achieving a high frame rate. In the system, Server is highly parallelized on multiple GPGPUs using a hybrid MPI-CUDA programing model. The particle generation is accelerated by two orders of magnitudes compared with CPU, and structured and unstructured volume data with a hundred million cells are processed within a second. The total performance of remote visualization is compared against a commodity visualization tool, and an order of magnitude faster processing speed is achieved.

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