Bayesian sparse modeling of extended X-ray absorption fine structure to determine interstitial oxygen positions in yttrium oxyhydride epitaxial thin film

Kumazoe, Hiroyuki*; Igarashi, Yasuhiko*; Iesari, F.*; Shimizu, Ryota*; Komatsu, Yuya*; Hitosugi, Taro*; Matsumura, Daiju; Saito, Hiroyuki*; Iwamitsu, Kazunori*; Okajima, Toshihiko*; et al.

AIP Advances (Internet), 11(12), p.125013_1 - 125013_5, 2021/12

https://doi.org/10.1063/5.0071166

Role of advection in atmospheric ammonia; A Case study at a Japanese lake basin influenced by agricultural ammonia sources

Kubota, Tomohiro; Kuroda, Hisao*; Watanabe, Mirai*; Takahashi, Akiko*; Nakazato, Ryoji*; Tarui, Mika*; Matsumoto, Shunichi*; Nakagawa, Keita*; Numata, Yasuko*; Ouchi, Takao*; et al.

Atmospheric Environment, 243, p.117856_1 - 117856_9, 2020/12

https://doi.org/10.1016/j.atmosenv.2020.117856

The dry and wet depositions of atmospheric ammonia (NH) is one of the important pathways of nitrogen loads to aquatic ecosystems. Crop and livestock agriculture, one of the largest emitters of NH in Asian countries, are known to cause high spatial and seasonal variation of NH and influence the surrounding lake basin areas via its dry and wet deposition. However, the spatial characteristics of the NH concentration in basin scale are not completely understood for regulation in NH emission. Here we aim to clarify dominant factors of spatial and seasonal variations of the NH concentration in a eutrophic lake basin surrounded by agricultural areas in Japan. Passive sampling over various land use categories in the basin was conducted at 36 sites in total from October 2018 to January 2020. Interestingly, the observed NH concentration near the livestock houses were higher in winter than summer, which was inconsistent with knowledge of seasonal changes of current NH emission inventory based on temperature-driven volatilization process. Comparing monthly NH concentrations with various meteorological factors, we suggested the importance of seasonal advection of NH from high emission sources to which has been rarely paid attention by the previous past studies. As for this, should be considered for lake ecosystem management since deposition of NH is known to be closely related to the ecological processes such as phytoplankton blooming.

Possibility of formic and acetic acids as active substrates for methanogenesis in the groundwater in Horonobe, Hokkaido

Tamamura, Shuji*; Endo, Ryo*; Shimizu, Satoru*; Iwatsuki, Teruki; Amano, Yuki; Omi, Yasushi*; Igarashi, Toshifumi*

Journal of MMIJ, 128(10,11), p.570 - 575, 2012/10

http://doi.org/10.2473/journalofmmij.128.570

no abstracts in English

Research and development of highly-accurate simulation for quantum many-body systems; Parallel-computing of density matrix renormalization group method and ultra large-scale simulations

Yamada, Susumu; Igarashi, Ryo; Okumura, Masahiko*; Imamura, Toshiyuki*; Machida, Masahiko

Oyo Suri, 20(2), p.132 - 147, 2010/06

http://ci.nii.ac.jp/naid/110007658157

The density matrix renormalization group (DMRG) method is a numerical calculation technique to obtain the ground state of quantum lattice systems whose degree of freedoms exponentially grows with the size of the lattice sites and particles (or spins in interacting spin systems). Its advantage is excellent accuracy comparable to the exact diagonalization scheme even in considerably large number of sites and particles (spins). However, the technique has been originally developed for one-dimensional systems. Therefore, the extension to higher dimensional lattices systems is in great demand since major rich physics such as superconductivity and ferromagnetism frequently occurs in two or three dimensions. This paper describes a parallelization strategy of the technique to calculate quasi-two dimensional (ladder) systems toward the next generation supercomputer and reports its good parallel efficiency on T2K supercomputer HA8000 at University of Tokyo. Moreover, typical quantum phenomena obtained by using the parallelized code are exhibited and some remarks on parallelization scheme in the next generation supercomputer are mentioned.

Strength proof evaluation of diffusion-jointed W/Ta interfaces by small punch test

Li, J.-F.*; Kawai, Masayoshi*; Kikuchi, Kenji; Igarashi, Tadashi*; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Kawasaki, Akira*

Journal of Nuclear Materials, 321(2-3), p.129 - 134, 2003/09

https://doi.org/10.1016/S0022-3115(03)00237-X

For the development of tantalum-clad tungsten targets for spallation neutron sources, the bonding strength of tantalum-tungsten interface was investigated by means of an easy-to-use and miniaturized small punch (SP) test, in which a punching load is vertically applied to the center of a jointed disk. Cracks initiated and propagated in the tungsten side for all the samples hot-isostatically pressed (HIPed) at temperatures from 1673 to 2073 K, whereas nocrack and debonding were observed in the interface, indicating that the jointed interface is strongly bonded. The re-crystallization of tungsten occurs and results in its strength reduction, consequently the crack-initiating load decreases with HIPing temperature. The finite element analysis of the measured SP testing results shows that the maximum bonding strength can exceed 1000 MPa. The present study shows that SP test is suitable for the strength evaluation of jointed tantalum-tungsten interfaces.

R&D of a MW-class solid-target for spallation neutron source

Kawai, Masayoshi*; Furusaka, Michihiro*; Kikuchi, Kenji; Kurishita, Hiroaki*; Watanabe, Ryuzo*; Li, J.*; Sugimoto, Katsuhisa*; Yamamura, Tsutomu*; Hiraoka, Yutaka*; Abe, Katsunori*; et al.

Journal of Nuclear Materials, 318, p.35 - 55, 2003/05

R&D works for MW class solid target composed of tungsten to produce pulsed intense neutron source has been made in order to construct a future scattering facility. Three methods were investigated to prevent corrosion of tungsten from water; those are hipping, brazing and electric coating in molten salt bath. Hipping condition was optimized to be 1500 degree C in the previous work: here small punch test shows highest load for crack initiation of hipped materials at the boundary of W/Ta. The basic techniques for the other two methods were developed. Erosion test showed that uncovered W is susceptible of flowing water velocity. At high velocity w is easy to be eroded. For solid target design slab type and rod type targets were studied. As long as the optimized neutron performance is concerned, 1MW solid target is better than mercury target.

Next-generation quantum many-body simulation project toward petaflops computing; Density matrix renormalization group method on massively parallel computer

Yamada, Susumu; Imamura, Toshiyuki*; Okumura, Masahiko; Igarashi, Ryo; Machida, Masahiko

no journal, , 

no abstracts in English

Parallel solver for large eigenvalue problems on density matrix renormalization group method

Yamada, Susumu; Imamura, Toshiyuki*; Okumura, Masahiko; Igarashi, Ryo; Machida, Masahiko

no journal, , 

no abstracts in English

Parallelization strategy for density matrix renormalization group toward peta-flops parallel computer

Yamada, Susumu; Imamura, Toshiyuki*; Okumura, Masahiko; Igarashi, Ryo; Machida, Masahiko

no journal, , 

no abstracts in English

Ground state phase diagram of the asymmetric spin tube up to 6 legs

Igarashi, Ryo; Okumura, Masahiko; Yamada, Susumu; Machida, Masahiko

no journal, ,