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Efficient high harmonics generation by enhancement cavity driven with a post-compressed FCPA laser at 10 MHz

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High Power Laser Science and Engineering 2018年第2期6卷 45-50页

作者： Zhigang Zhao akira Ozawa Makoto Kuwata-Gonokami Yohei Kobayashi The Institute for Solid State Physics The University of Tokyo Department of Physics Graduate School of Science The University of Tokyo

Efficient high harmonics generation(HHG) was demonstrated at 10 MHz repetition rate with an external femtosecond enhancement cavity, seeded by a ～70 fs post-compressed 10 MHz fiber chirped pulse amplifier(FCPA) laser. Operation lasting over 30 min with 0.1 m W outcoupled power at 149 nm was demonstrated. It was found that shorter pulse was beneficial for alleviating the nonlinear plasma effect and improving the efficiency of HHG. Low finesse cavity can relax the plasma nonlinearity clamped intra-cavity power and improve the cavity-locking stability. The pulse duration is expected to be below 100 fs for both 1040 nm and 149 nm outputs, making it ideal for applications such as time-resolved photoemission spectroscopy.

关键词： enhancement cavity high harmonics generation ultrafast fiber lasers

Maintenance of an abrupt boundary between needle-leaved and broad-leaved forests in a wetland near coast

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Journal of Forestry Research 2009年第A2期20卷 91-98,I0001页

作者： Shiro Tsuyuzaki akira Haraguchi Graduate School of Environmental Earth Science Hokkaido University Sapporo 060-0810 Japan Faculty of Environmental Engineering The University of Kitakyushu Kitakyushu 808-0135 Japan

There is an abrupt boundary between two well-developed wetland forests, a stand consisting of a broad-leaved, nitrogen-fixer Alnusjaponica and a stand of the needle-leaved Picea glehnii Masters, in eastern Hokkaido, Japan. To clarify maintenance mechanisms, we studied the forest profile, water level, groundwater and precipitation chemistry, seedling establishment patterns in relation to microhabitats, and seed migration. The profile of groundwater level insufficiently explained the abrupt boundary formation, while the groundwater chemistry differed significantly between the two forests ; i.e., EC, Na^＋, K^＋, Mg^2＋, Ca^2＋ and Cl^- were higher in P. glehnii forest and pH was lower. Precipitation in P. glehnii forest contained richer Na＋, Ca^2＋ and Cl^-, indicating that the differences in surface-water chemistry were mostly derived from precipitation. Solar radiation was less than 2.2 MJ.m^-2.d^-1 on P. glehnii forest in late June, while that was patchily distributed in *** forest with a range from 1.0 to 3.7 MJ＇m^-2＇d^-1. Moss cover on the soil surface, most of which were made of Sphagnum spp., was 60% in P. glehnii forest, but was 10% in A. japonica forest. Surface water chemistry represented by pH was considered to determine the development of Sphagnum moss. About 70% of P. glehnii seedlings 〈 1.3 m in height established on moss cover. Seed-sowing experiments suggested that seed germination and seedling survival for both species were significantly higher in P. glehnii forest. Therefore, the regeneration of P. glehnii in A. japonica forest was negligible, owing to the paucity of favorable microhabitats and low seedling establishment. A. japonica regenerated only by resprouting, and the seedlings were few in both forests. In addition, A. japonica seed migration into the P. glehnii forests was greatly restricted, and low solar radiation in the P. glehnii forest contributed to low seedling survival. Based on those results, we concluded that Picea glehnii and Alnu

关键词： Alnusjaponica microhabitat Picea glehnii positive feedback switch precipitation chemistry seed dispersal wetland forest

High-quality micro-shape fabrication of monocrystalline diamond by nanosecond pulsed laser and acid cleaning

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International Journal of Extreme Manufacturing 2022年第2期4卷 173-183页

作者： Yasuhiro Okamoto Tubasa Okubo Atsuya Kajitani akira Okada Graduate School of Natural Science and Technology Okayama UniversityOkayamaJapan

The flat plane of small surface roughness below 0.1μm average roughness was obtained for monocrystalline diamond by nanosecond pulsed laser irradiation of 1060 nm and post-process acid cleaning,at a laser fluence around the material removal threshold *** glossy and flat plane at the bottom of the micro-groove was parallel to the top surface of the specimen,although the round beam of Gaussian mode was irradiated in the direction perpendicular to the top surface of *** square beam of top-hat mode produced a shallower micro-groove with a wider,flatter bottom compared with the round beam in Gaussian *** creation method of the flat plane with small surface roughness was discussed in the arrangement strategy of linear micro-grooving by the square beam of top-hat *** side-by-side repetition of linear micro-grooving did not create a flat plane with constant ***,a two-step scanning method was proposed in order to overcome the problem in the normal side-by-side repetition of liner ***-removal areas were partly retained between the processing lines in the first step,and the laser scanning was conducted on the retained area in the second *** newly proposed two-step scanning method was practical and useful to create a widely flat plane with small surface roughness,and the two-step scanning method provided superior control over the micro-groove *** proposed method can reduce the surface roughness in addition to the shape creation of monocrystalline diamond,and it can be used as a high-quality micro-shape fabrication method of monocrystalline diamond.

关键词： monocrystalline diamond nanosecond pulsed laser flat surface smooth surface micro-grooving

Implementation issues of the planning support tool in Japan:Focusing on urban disaster mitigation

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Frontiers of Architectural Research 2019年第4期8卷 483-497页

作者： Kazuki Karashima akira Ohgai Department of Architecture and Civil Engineerins Toyohashi University of TechnologyToyohashiAichiJapan

This study determined the issues of Planning Support System(PSS)implementation in the field of urban disaster mitigation in Japan by understanding its analytical perspective through a review of Western literature,a questionnaire survey of urban planning consultant companies,and PSS implementation for a practical project in a *** the instrum ental perspective,there was difficulty in conducting the simulationbased PSS due to the enormous simulation time *** the transfer perspective,the importance of the municipality^decision of adopting the PSS to a project,securing the budget and continuous running costs,track record of the practical project,and lack of human resource for the PSS use were *** the user perspective,the difficulty in data collection and update as well as im portance of the cooperative system/support from the developer in the initial period were ***,considering the low number of implementations,a platform may be important for the promotion of PSS *** may be also useful for the diffusion of *** is necessary for the developers to fully comm unicate the benefits of PSS *** is thought that a close cooperative system and support are required in the initial *** prom oting and understanding the benefits of PSS adoption,a guideline or manual seems to be *** is effective for ensuring the budget and providing an explanation to high-level members of the organizations about the effect of utilizing these *** the final implementation,the possibility of installation,maintenance,and operation of the PSS by the municipality was discussed.

关键词： Planning support tool Urban disaster mitigation Implementation GIS Fire spread Evacuation

High-resolution modeling and evaluation of ozone air quality of Osaka using MM5-CMAQ system

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Journal of Environmental Sciences 2009年第6期21卷 782-789页

作者： SHRESTHA Kundan Lal KONDO akira KAGA Akikazu INOUE Yoshio Division of Sustainable Energy and Environmental Engineering School of EngineeringOsaka University

High-resolution modeling approach is increasingly being considered as a necessary step for improving the monitoring and predictions of regional air quality. This is especially true for highly urbanized region with complex terrain and land-use. This study uses Community Multiscale Air Quality （CMAQ） model coupled with MM5 mesoscale model for a comprehensive analysis to assess the suitability of such high-resolution modeling system in predicting ozone air quality in the complex terrains of Osaka, Japan. The 1-km and 3-kin grid domains were nested inside a 9-km domain and the domain with 1-km grid covered the Osaka region. High-resolution Grid Point Value-Mesoscale Model （GPV-MSM） data were used after suitable validation. The simulated ozone concentrations were validated and evaluated using statistical metrics using performance criteria set for ozone. Daily maxima of ozone were found better simulated by the 1-krn grid domain than the coarser 9-km and 3-km domains, with the maximum improvement in the mean absolute gross error about 3 ppbv. In addition, 1-km grid results fared better than other grids at most of the observation stations that showed noticeable differences in gross error as well as correlation. These results amply justify the use of the integrated high-resolution MM5-CMAQ modeling system in the highly urbanized region, such as the Osaka region, which has complex terrain and land-use.

关键词： air quality model evaluation ozone Community Multiscale Air Quality MM5 statistical analysis

Extraction of yarn positional information from three-dimensional CT image of textile fabric using a yarn model for its structure analysis

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仪器仪表学报 2008年第8期29卷 1569-1576页

作者： Toshihiro Shinohara Jun-ya Takayama Shinji Ohyama akira Kobayashi School of Biology-Oriented Science and Technology Kinki University Kinokawa-shi Wakayama-kenJapan Graduate School of Science and Engineering Tokyo Institute of Technology1-12-1 Meguro-kuTokyoJapan Faculty of University Evaluation and Research National Institution for Academic Degrees and UniversityEvaluation Kodaira-shi TokyoJapan

This paper proposes a novel method for analyzing a textile fabric structure to extract positional information regarding each yarn using three-dimensional X-ray computed tomography(3D CT) *** relationship among the yarns can be reconstructed using the extracted yarn positional *** this paper,a sequence of points on the center line of each yarn of the sample is defined as the yarn positional information,since the sequence can be regarded as the representative position of the *** sequence is extracted by tracing the *** yarn is traced by estimating the yarn center and direction and correlating the yarn part of the 3D CT image with a 3D yarn model,which is moved along the estimated yarn *** trajectory of the center of the yarn model corresponds to the positional information of the *** application of the proposed method is shown by experimentally applying the proposed method to a 3D CT image of a double-layered woven ***,the experimental results for a plain knitted fabric show that this method can be applied to even knitted fabrics.

关键词：纺织品 CT影像分析方法物理结构

Tomographic particle image velocimetry measurement on three-dimensional swirling flow in dual-stage counter-rotating swirler

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Chinese Journal of Aeronautics 2024年第3期37卷 7-20页

作者： Yuyang ZHOU Ling DONG Mingtao SHANG Jibao LI akira RINOSHIKA Key Laboratory of Fluid Mechanics of Ministry of Education Beihang UniversityBeijing 100191China School of Mechanical and Automotive Engineering Shanghai University of Engineering ScienceShanghai 201620China AECC Commercial Aircraft Engine Co. Ltd.Shanghai 200241China Department of Mechanical Systems Engineering Yamagata UniversityYamagata 992-8510Japan

Three-Dimensional(3D)swirling flow structures,generated by a counter-rotating dualstage swirler in a confined chamber with a confinement ratio of 1.53,were experimentally investigated at Re=2.3×10^(5)using Tomographic Particle Image Velocimetry(Tomo-PIV)and planar Particle Image Velocimetry(PIV).Based on the analysis of the 3D time-averaged swirling flow structures and 3D Proper Orthogonal Decomposition(POD)of the Tomo-PIV data,typical coherent flow structures,including the Corner Recirculation Zone(CRZ),Central Recirculation Zone(CTRZ),and Lip Recirculation Zone(LRZ),were *** counter-rotating dual-stage swirler with a Venturi flare generates the independence process of vortex breakdown from the main stage and pilot stage,leading to the formation of an LRZ and a smaller CTRZ near the nozzle *** confinement squeezes the CRZ to the corner and causes a reverse rotation flow to limit the shape of the CTRZ.A large-scale flow structure caused by the main stage features an explosive breakup,flapping,and Precessing Vortex Core(PVC).The explosive breakup mode dominates the swirling flow structures owing to the expansion and construction of the main jet,whereas the flapping mode is related to the wake *** limits the expansion of PVC and causes it to contract after the impacting area.

关键词： Coherent structures Dual-stage counter-rotating swirler cup Precessing vortex core Proper orthogonal decomposition Swirling flow Tomographic particle image velocimetry

Nutrition status and Helicobacter pylori infection in patients receiving hemodialysis

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World Journal of Gastroenterology 2018年第15期24卷 1591-1600页

作者： Mitsushige Sugimoto Hideo Yasuda akira Andoh Division of Digestive Endoscopy Shiga University of Medical Science Hospital First Department of Medicine Hamamatsu University School of Medicine Department of Gastroenterology Shiga University of Medical Science Hospital

Chronic kidney disease(CKD) patients receiving hemodialysis(HD) often develop gastrointestinal abnormalities over their long treatment period. In general, prognosis in such patients is poor due to the development of protein-energy wasting(PEW). Therefore, it is important to clarify the etiology of PEW and to establish better strategies to deal with this condition. Chronic Helicobacter pylori(H. pylori) infection in the gastric mucosa has a close association with not only the development of peptic ulcer disease and gastric cancer, but is also associated with abnormal plasma and gastric mucosal ghrelin levels that are seen in malnutrition. It is unclear whether H. pylori infection of the gastric mucosa is directly associated with prognosis in HD patients by affecting ghrelin levels. Recent studies show that the prevalence of H. pylori infection in HD patients is significantly lower than in subjects with normal renal function. In the natural history of H. pylori infection in HD patients, the prevalence of infection decreases as the length of time on HD increases. The severity of gastric mucosal atrophy has been suggested as the major determinant of ghrelin levels in these patients, and eradication therapy of H. pylori improves nutritional status by increasing serum cholinesterase and cholesterol levels, especially in patients with mildto-moderate gastric mucosal atrophy. Prompt H. pylori eradication to inhibit the progress of gastric atrophy may be required to prevent this decrease in ghrelin levels and subsequent PEW and improve the prognosis of HD patients by improving their nutritional status.

关键词： Helicobacter pylori Hemodialysis Ghrelin Gastric mucosa Anti-bacterial agents

An Improvement of Multigrid Methods Using Multiple Grids on Each Layer for Parallel Computing

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Journal of Mathematical Research with Applications 2021年第1期41卷 87-98页

作者： akira IMAKURA University of Tsukuba

Multigrid methods are widely used and well studied for linear solvers and preconditioners of Krylov subspace methods. The multigrid method is one of the most powerful approaches for solving large scale linear systems; however, it may show low parallel efficiency on coarse grids. There are several kinds of research on this issue. In this paper, we intend to overcome this difficulty by proposing a novel multigrid algorithm that has multiple grids on each *** results indicate that the proposed method shows a better convergence rate compared with the existing multigrid method.

关键词： linear systems multigrid preconditioner