著者

Susumu Fujiwara Hiroaki Nakamura Haolun Li Hisanori Miyanishi Tomoko Mizuguchi Takuo Yasunaga Takao Otsuka Yuji Hatano Shinji Saito

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.6, no.1, pp.94-99, 2019 (Released:2019-03-15)

参考文献数

9

被引用文献数

3 8

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We propose a computational strategy for investigating structural change of tritium-substituted macromolecules. Effects of radiation on macromolecules such as polymeric materials and DNA are classified into three categories: (1) direct action, (2) indirect action, and (3) decay effect. In this study, we focus on the decay effect exclusively. After a beta decay of substituted tritium in macromolecules to helium-3, the generated inert helium-3 is assumed to be deleted quickly. To get an insight into the decay effect to the damage of macromolecules, we perform molecular dynamics simulations of tritium-deleted macromolecules and analyze their structural change. Preliminary simulation results of decay effect on polymeric materials and DNA are presented.

著者

Michiaki Arita Sergiu Arapan David R. Bowler Tsuyoshi Miyazaki

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.1, no.1, pp.87-97, 2014 (Released:2014-10-31)

参考文献数

24

被引用文献数

15 22 1

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In oder to realize the DFT simulations on large-scale complex systems, we have been developing a linear-scaling DFT code Conquest. In this paper, we report the parallel efficiency of the code on K-computer and show that it has almost ideal parallel efficiency even when we use more than 200,000 cores. Using the code on such large-scale parallel computers, we are now ready to do actual DFT study on million-atom systems. By showing our current study on the nucleation of Ge dimers on three-dimensional Ge nano-islands on Si(001), we demonstrate that accurate, efficient and robust structure relaxation based on the DFT is possible in the actual scientific research on complex nano-structured materials.

著者

Yuya Hanaoka Momoko Nojiri Taku Itoh Susumu Nakata Keiko Watanabe

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.6, no.1, pp.195-214, 2019 (Released:2019-05-30)

参考文献数

10

被引用文献数

2

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To construct a model of metal foam that has rounded cells such as a real one, an implicit surface based modelling method has been proposed. In this method, uniformed points are first generated randomly by Poisson-disk sampling, and a Voronoi diagram is constructed from the points. In addition, an implicit function f (x) is generated in each of Voronoi cells by setting some constraints appropriately. An implicit surface is represented as f (x) = 0, and the constraints are set so that f (x) = 0 is generated inside each of Voronoi cells. In this model, walls of metal foam are represented by space between implicit surfaces of adjacent Voronoi cells. Rounded walls that have various thicknesses can be constructed by adjusting the constraints. In addition, the walls can be converted to a solid model constructed as tetrahedra filling the space.

著者

Yuji Hatano Hiroto Shimoyachi Tatsuya Asano Takahiro Kenmotsu Takuro Wada Yasuhisa Oya Hiroaki Nakamura Susumu Fujiwara

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.9, no.1, pp.198-205, 2022 (Released:2022-06-17)

参考文献数

12

被引用文献数

1

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The goal of this study is to establish a simple experimental system to examine the rate of double strand breaks (DSBs) of genome-sized DNA molecules under irradiation of β-rays from tritium under well-controlled conditions for the validation of computer simulation on interactions of biomolecules and ionizing radiation. Irradiation effects were insignificant at tritium concentration of 1300 Bq/cm3, indicating that the effects of β-rays were far smaller than those of oxidation and/or thermal motion at the low dose rate (4.3 μGy/h). Clear increase in DSB rate was observed at tritium concentrations of 3.0—4.0 MBq/cm3. The temperature dependence of DSB rate was examined by using the high concentration tritiated water.

著者

Hiroshi Serizawa Takashi Amemiya Kiminori Itoh

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.10, no.2, pp.221-246, 2023 (Released:2023-12-08)

参考文献数

43

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We present a minimal version of Landscape Evolution Models (LEMs) to capture the essence of tree-shaped channel network formation on the assumption of two mechanisms, soil erosion and diffusion. The continuous tectonic uplift is not required, which affects landscape evolution only at the starting point. We refer to the mathematical model as the Erosion-Diffusion Model (EDM). No steady state exists in the EDM except for the perfectly flat plane, which is realized at the ultimate final stage of the landform transition. It is suggested that generated channel patterns are temporal and transient creatures during long-term gravitational and erosional processes on the earth.

著者

Tomohoiro Tanaka Hidekazu Yoshioka

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.4, no.2, pp.162-175, 2017 (Released:2018-06-30)

参考文献数

21

被引用文献数

1 3

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The local inertial equation (LIE) as a simple mathematical model has been widely used for flood simulation. So far, the maximum allowable time step of the discretized LIE with the conventional semi-implicit scheme has been believed to follow the standard Courant-Friedrichs-Lewy condition. However, we demonstrate that this is not true from the viewpoint of a numerical stability analysis considering the model non-linearity. In addition, a fully-implicit variant of the scheme with higher stability is presented, indicating its practical advantages.

著者

Ran Dong Daisuke Shigeta Yoshihisa Fujita Soichiro Ikuno

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.9, no.1, pp.65-77, 2022 (Released:2022-02-08)

参考文献数

18

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Photonic crystals are widely employed in industry fields due to their bandgap property, which can confine and propagate electromagnetic waves inside the structure as a photonic waveguide. As this property can be adopted to propagate distinct frequency waves by changing the photonic structure, photonic crystals are also applied in frequency demultiplexer design. The finite-difference time-domain (FDTD) method is commonly applied to simulate electromagnetic wave propagations in photonic crystals, helping determine the desired bandgaps for frequency demultiplexers. Meanwhile, the multivariate empirical mode decomposition (MEMD) nonlinearly decomposes multivariate signals in the instantaneous frequency domain. Therefore, MEMD can verify and visualize the designed frequency demultiplexer made of photonic crystals by considering simulation results as a multi-channel signal. This research aims to propose a method to design and evaluate frequency demultiplexers using FDTD and MEMD. In this paper, photonic crystal bandgaps are adopted to design a frequency demultiplexer to separate two different frequency electromagnetic waves. Then, MEMD is employed to the result of frequency demultiplexer propagation simulated by FDTD. Our results reveal that the frequency demultiplexer made of photonic crystals can be designed using the bandgap properties, and its simulation results by FDTD method can be verified and visualized in the instantaneous frequency domain using MEMD.

著者

Yuya Hanaoka Taku Itoh Kohei Tateyama Susumu Nakata Keiko Watanabe

出版者

Japan Society for Simulation Technology

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.8, no.1, pp.143-153, 2021 (Released:2021-06-12)

参考文献数

11

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Recently, to generate metal foam models for either open or closed state, a sphere-function-based method and a radial-basis-function-based one have been proposed. In these methods, implicit functions are employed for representing shapes of metal foams. In this paper, these methods based on spheres and radial basis functions have similarly been extended by employing characteristics of implicit functions, so that open/closed states and their intermediates can be represented. It is an advantage of the extended methods that any states of metal foams can be represented by only one implicit function.

著者

Wang Sheng Ken Ishikawa Hiromi T. Tanaka Akihiro Tsukamoto Satoshi Tanaka

出版者

一般社団法人 日本シミュレーション学会

雑誌

日本シミュレーション学会英文誌 (ISSN:21885303)

巻号頁・発行日

vol.1, no.1, pp.188-204, 2015 (Released:2015-02-17)

参考文献数

17

被引用文献数

5

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Virtual reality (VR) technology can be used to simulate environments of historical sites in virtual spaces. In fact, many VR reproductions of historical sites have already been studied and developed. For users, the quality of the visual experience largely determines the authenticity of a VR space. However, when developing a VR space, it is difficult and time-consuming to significantly improve visual quality while maintaining real-time rendering speed, which is the primary requirement of an effective user interface. For this reason, there have been few genuinely photorealistic VR spaces created for historical sites. However, this has begun to change due to the arrival of next-generation three-dimensional (3D) game engines. In this paper, we report on our recent development of photorealistic VR spaces for historical Kyoto sites created using the UDK 3D Game Engine. Specifically, we describe our VR reproduction of Reizei-ke, which consists of the Japanese court noble residence (kuge-yashiki), and Funehoko-cho, which is an important site for Japan's Gion Festival. Through the fabrication of these VR spaces, we could also extract a workflow that allows us to realize photorealistic and read-time VR contents of other cultural assets based on the abovementioned next-generation 3D game engine.