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Journal Articles

Interactive steering on in situ particle-based volume rendering framework

Kawamura, Takuma; Hasegawa, Yuta; Idomura, Yasuhiro

Journal of Visualization, 27(1), p.89 - 107, 2024/02

Interactive in-situ steering is an effective tool for debugging, searching for optimal solutions, and analyzing inverse problems in fast and large-scale computational fluid dynamics (CFD) simulations. We propose an interactive in-situ steering framework for large-scale CFD simulations on GPU supercomputers. This framework employs in-situ particle-based volume rendering (PBVR), in-situ data sampling, and a file-based control that enables interactive communication of steering parameters, compressed particle data, and sampled monitoring data between supercomputers and user PCs. The parallelized PBVR is processed on the host CPU to avoid interference with CFD simulations on the GPU. We apply the proposed framework to a real-time plume dispersion analysis code CityLBM on GPU supercomputers. In the numerical experiment, we address an inverse problem to find a pollutant source from the monitoring data, and demonstrate the effectiveness of the human-in-the-loop approach.

Journal Articles

VR extension of client server type particle-based volume visualization application

Kawamura, Takuma; Sakamoto, Naohisa*; Osaki, Tsukasa*

Journal of Advanced Simulation in Science and Engineering (Internet), 10(1), p.31 - 39, 2023/02

Visualization of large fluid computation results at remote locations by VR, especially using volume rendering, is one of the key challenges in the visualization field. The remote visualization application CS-PBVR is capable of interactive volume rendering of large-scale data in remote locations. In this study, the image generation of CS-PBVR was extended for head-mounted displays to develop a remote VR visualization application, VR-PBVR. We also developed a function that allows manipulation of visualization data by gesture control with both hands in VR space. We applied VR-PBVR to remote volume data and confirmed that it can visualize the data at interactive frame rates.

Journal Articles

Development of VR support and gesture control functions for particle-based visualization applications

Kawamura, Takuma; Sakamoto, Naohisa*

Dai-36-Kai Suchi Ryutai Rikigaku Shimpojiumu Koen Rombunshu (Internet), 3 Pages, 2022/12

Volume rendering is useful for visualizing computer fluid dynamics (CFD) data, and its VR visualization helps to understand complex 3D data. Volume rendering of large scale data in remote locations in VR space is an important issue of the visualization field. A remote visualization application CS-PBVR can interactively visualize the large-scale datasets in remote locations with volume rendering. In order to extend CS-PBVR into VR-PBVR which is applicable to a head mount display (HMD) Oculus rift S, we added a stereo image generation function, a gesture control function, and a renewed processing flow. VR-PBVR achieved interactive visualization of remotely located test dataset (2M cells) with 90 fps.

Journal Articles

VR extension of particle-based remote visualization application

Kawamura, Takuma; Sakamoto, Naohisa*

Proceedings of 41st JSST Annual International Conference on Simulation Technology (JSST 2022) (Internet), p.266 - 269, 2022/09

Visualization of the large CFD dataset in remote locations by VR, especially using volume rendering, is one of the issues in the visualization field. The visualization library KVS supports PBVR, a unique particle-based visualization method suitable for large-scale data, and we have developed an extension of KVS for VR. In this paper, we present a design for VR extension of CS-PBVR, a remote visualization application based on KVS. The developed CS-PBVR for VR is then applied to test data and shown to be capable of VR visualization at interactive frame rates.

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

 Times Cited Count:3 Percentile:49.33(Nuclear Science & Technology)

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

 Times Cited Count:3 Percentile:49.33(Nuclear Science & Technology)

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

Dynamical response of transition-edge sensor microcalorimeters to a pulsed charged-particle beam

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I.-H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

IEEE Transactions on Applied Superconductivity, 31(5), p.2101704_1 - 2101704_4, 2021/08

 Times Cited Count:1 Percentile:12.26(Engineering, Electrical & Electronic)

A superconducting transition-edge sensor (TES) microcalorimeter is an ideal X-ray detector for experiments at accelerator facilities because of good energy resolution and high efficiency. To study the performance of the TES detector with a high-intensity pulsed charged-particle beam, we measured X-ray spectra with a pulsed muon beam at the Japan Proton Accelerator Research Complex (J-PARC) in Japan. We found substantial temporal shifts of the X-ray energy correlated with the arrival time of the pulsed muon beam, which was reasonably explained by pulse pileup due to the incidence of energetic particles from the initial pulsed beam.

Journal Articles

Deexcitation dynamics of muonic atoms revealed by high-precision spectroscopy of electronic $$K$$ X rays

Okumura, Takuma*; Azuma, Toshiyuki*; Bennet, D. A.*; Caradonna, P.*; Chiu, I. H.*; Doriese, W. B.*; Durkin, M. S.*; Fowler, J. W.*; Gard, J. D.*; Hashimoto, Tadashi; et al.

Physical Review Letters, 127(5), p.053001_1 - 053001_7, 2021/07

 Times Cited Count:9 Percentile:77.29(Physics, Multidisciplinary)

We observed electronic $$K$$X rays emitted from muonic iron atoms using a superconducting transition-edge-type sensor microcalorimeter. The energy resolution of 5.2 eV in FWHM allowed us to observe the asymmetric broad profile of the electronic characteristic $$K$$$$alpha$$ and $$K$$$$beta$$ X rays together with the hypersatellite $$K$$$$alpha$$ X rays around 6 keV. This signature reflects the time-dependent screening of the nuclear charge by the negative muon and the $$L$$-shell electrons, accompanied by electron side-feeding. Assisted by a simulation, this data clearly reveals the electronic $$K$$- and $$L$$-shell hole production and their temporal evolution during the muon cascade process.

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:7.99(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:3 Percentile:66.81

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


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:18.61(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:9 Percentile:91.02

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.

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