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shock Wave Observation in Narrow Tubes for a Parametric study on Micro Wave Rotor Design

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Journal of Thermal science 2008年第2期17卷 134-140页

作者： Koji okamoto Mikiya Araki Department of Aeronautics and Astronautics University of Tokyo Department of Mechanical Engineering Gunma University

Wave rotor is expected to improve the performance of micro gas turbines drastically. In the wave rotor design, the rotor speed is determined principally by the tube length. Therefore, a longer tube is preferable for miniaturized wave rotors to avoid the difficulty in bearings and lubrication system, while it may yield thicker wall boundary layer, shock wave dissipation and so on. In the present study, an experimental apparatus was built to visualize the wave rotor internal flow dynamics in a narrow tube by schlieren method and Laser Doppler Anemometry. In addi- tion, different lengths of the tube were adopted and compared to investigate the effect of wall friction. Finally, 2D numerical simulation was performed and the results were compared with those of experiments.

关键词： wave rotor shock wave unsteady flow micro propulsion flow visualization.

后稳定型膝关节置换术胫骨平台假体后倾角对膝关节运动学、股四头肌肌力以及髌股关节接触应力的影响

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临床骨科杂志 2015年第2期18卷 210-210页

作者： okamoto s Mizu-Uchi H Okazaki K 胡孔足

作者采用膝关节模型研究后稳定型膝关节置换术胫骨平台假体后倾角对膝关节运动学、股四头肌肌力以及髌股关节接触应力的影响,发现随着胫骨平台假体后倾角的增加,股四头肌肌力以及髌股关节接触应力均减小。在胫骨平台假体后倾角为5°和1... 详细信息

作者采用膝关节模型研究后稳定型膝关节置换术胫骨平台假体后倾角对膝关节运动学、股四头肌肌力以及髌股关节接触应力的影响,发现随着胫骨平台假体后倾角的增加,股四头肌肌力以及髌股关节接触应力均减小。在胫骨平台假体后倾角为5°和10°时分别发现胫骨组件前移和胫骨组件前方撞击。

关键词：膝关节置换术胫骨平台关节运动学接触应力髌股关节股四头肌后稳定型后倾角

Malignant biliary obstruction due to metastatic non-hepatopancreato-biliary cancer

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World Journal of Gastroenterology 2022年第10期28卷 985-1008页

作者： Takeshi okamoto Department of Gastroenterology St.Luke’s International HospitalChuo-ku 104-8560TokyoJapan

Malignant biliary obstruction generally results from primary malignancies of the pancreatic head,bile duct,gallbladder,liver,and ampulla of *** lesions from other primaries to these organs or nearby lymph nodes are rarer causes of biliary *** most common primaries include renal cancer,lung cancer,gastric cancer,colorectal cancer,breast cancer,lymphoma,and *** may be difficult to differentiate from primary hepato-pancreatobiliary cancer based on imaging studies,or even on *** is also no consensus on the optimal method of treatment,including the feasibility and effectiveness of endoscopic intervention or surgery.A thorough review of the literature on pancreato-biliary metastases and malignant biliary obstruction due to metastatic non-hepato-pancreato-biliary cancer is *** diagnostic modality and clinical characteristics may differ significantly depending on the type of primary *** primaries also cause malignant biliary obstruction in different ways,including direct invasion,pancreatic or biliary metastasis,hilar lymph node metastasis,liver metastasis,and peritoneal *** may hold promise for some types of pancreato-biliary *** review aims to elucidate the current knowledge in this area,which has received sparse attention in the *** aging population,advances in diagnostic imaging,and improved treatment options may lead to an increase in these rare occurrences going forward.

关键词： Bile duct obstruction Obstructive jaundice Pancreas Metastasis Endoscopic retrograde cholangiopancreatography

A mathematical model to predict the risk of hepatitis B infection through needle/syringe sharing in mass vaccination

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Infectious Diseases of Poverty 2013年第1期2卷 231-239页

作者： Etsuji okamoto Department of Health and Welfare service Research National Institute of Public HealthSaitama 351-01972-3-6 MinamiWako-shiJapan

Background:The Japanese Government settled a class litigation case with hepatitis B virus(HBV)carriers who claim to have been infected through needle/syringe sharing in childhood mass vaccination with a blanket compensation ***,it is difficult to estimate how many of the present HBV carriers were infected horizontally from mass vaccination and how many were infected vertically from ***:A mathematical model to predict the risk of infection through needle/syringe sharing in mass vaccination was proposed and a formula was *** formula was presented in a logarithmic graph enabling users to estimate how many people will be infected if a needle/syringe is shared by how many people for how many times under certain probability of *** formula was then applied to the historical data of mass tuberculin skin tests(TsTs)and BCG inoculation,from which a best estimate of how much needle/syringe sharing was practiced in different birth cohorts was ***:For the oldest cohort born between 1951 and 1955,the prevalence of HBV carriers-0.65%at birth through vertical transmission-more than doubled in 1995(1.46%)through horizontal *** the probability of infection through needle/syringe sharing is assumed to be 10%,it is theoretically likely that an average of five or more people shared a needle/syringe four times to achieve the prevalence of HBV carriers in ***,for the youngest cohort born between 1981 and 1985,the effects of needle/syringe sharing were negligible because the later prevalence of HBV carriers was lower than the prevalence at ***:More than half of the HBV carriers born in the early 1950s might have contracted the disease by mass ***’s experience needs to be shared with other countries as a caution in conducting mass vaccination programs under scarce needle/syringe supply(291 words).

关键词： Hepatitis Mass tuberculin skin test Needle sharing Mathematical model Iatrogenic infection

Computationally Efficient Large-Eddy simulation of Periodic Unsteady Flow using Harmonic Balance Method

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Journal of Thermal science 2022年第1期31卷 62-71页

作者： YUMA Iwamoto sUsUMU Teramoto KOJI okamoto Department of Aeronautics and Astronautics University of TokyoTokyo 113-8656Japan Department of Advanced Energy University of TokyoTokyo 113-8656Japan

To improve the efficiency and fidelity of the numerical analysis for cascade flutter, we propose an efficient scale-resolving simulation method dedicated to time-periodic flows by incorporating the harmonic balance approach into the large-eddy simulation. This method combined convergence calculations of the steady-state problem based on the harmonic balance method for periodic components, and the nonlinear time-marching method for turbulent fluctuations. Using the proposed method, deterministic periodic components and stochastic turbulent fluctuations were calculated simultaneously, and the effect of turbulent fluctuations on deterministic periodic components was directly calculated without using turbulence models. In this paper, we explain the algorithm and feature of this simulation technique and present the results of the computation for channel flow excited in the streamwise direction as an analysis example using the proposed method. In order to validate the proposed method, an analysis of sinusoidally pulsating channel flow at the central friction-velocity Reynolds numbers Rer = 180 was conducted, confirming that the amplitude and phase of the mean velocity oscillation computed by the proposed method were in good agreement with those of the conventional LEs. The present calculation achieved an order of magnitude improvement in computational efficiency compared to conventional LEs.

关键词： harmonic balance LEs turbulent channel flow

Characteristic of Local Boiling Heat Transfer of Ammonia and Ammonia/Water Binary Mixture on the Plate Type Evaporator

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Journal of Thermal science 2011年第4期20卷 332-342页

作者： Akio okamoto Hirofumi ARIMA Yasuyuki IKEGAMI Titanium Division KOBE STEEL Ltd.Japan Institute of Ocean Energy Saga UniversityJapan

Power generation using small temperature difference such as ocean thermal energy conversion(OTEC)and discharged thermal energy conversion(DTEC)is expected to be the countermeasures against global warming *** ammonia and ammonia/water are used in evaporators for OTEC and DTEC as working fluids,the research of their local boiling heat transfer is important for improvement of the power generation *** of local boiling heat transfer coefficients were performed for ammonia/water mixture(z=0.9-1)on a vertical flat plate heat exchanger in a range of mass flux(7.5-15 kg/m2s),heat flux(15-23 kW/m 2),and pressure(0.7-0.9 MPa).The result shows that in the case of ammonia/water mixture,the local heat transfer coefficients increase with an increase of mass flux and composition of ammonia,and decrease with an increase of heat flux.

关键词： Local Heat Transfer Ammonia/Water Mixture Plate Type Evaporator OTEC

Floating Type Ocean Wave Power station Equipped with Hydroelectric Unit

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Journal of Thermal science 2013年第5期22卷 467-471页

作者： shun okamoto Toshiaki Kanemoto Toshihiko Umekage Kyushu Institute of Technology Sensui 1-1 Tobata Kitakyushu 804-8550 Japan

The authors have invented the unique ocean wave power station,which is composed of the floating type platform with a pair of the floats lining up at the interval of one wave pitch and the counter-rotating type wave power unit,its runners are submerged in the seawater at the middle position of the *** profiles make the flow velocity at the runner is twice faster than that of the traditional fixed/caisson type OWC,on the ideal flow ***,the runners counter-rotate the inner and the outer armatures of the peculiar generator,respectively,and the relative rotational speed is also twice faster than the speed of the single runner/*** characteristics make the runner diameter large,namely the output higher,as requested,because the torque of the power unit never act on the floating type *** the preliminary reseach,this paper verifies to get the power using a Wells type single runner installed in the model *** runner takes the output which is affected by the oscillating amplitude of the platform,the rotational speed and the inertia force of the runner,etc.

关键词： Renewable energy Ocean wave Float Platform Counter-rotation Power unit

Analysis of molten metal spreading and solidification behaviors utilizing moving particle full-implicit method

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Frontiers in Energy 2021年第4期15卷 959-973页

作者： Ryo YOKOYAMA Masahiro KONDO shunichi sUZUKI Koji okamoto Department of Nuclear Engineering and Management The University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan Research Center for Computational Design of Advanced Functional materials(CD-FMat) Department of Materials and ChemistryNational Institute of Advanced Industrial Science and Technology(AIST)Central 21-1-1UmezonoTsukubaIbaraki 305-8568Japan Institute of Engineering Innovation School of EngineeringThe University of Tokyo7-3-1 HongoBunkyo-kuTokyo 113-8656Japan Nuclear Professional school The University of Tokyo2-22 ShirakataTokai-muraIbaraki 319-1188Japan

To retrieve the fuel debris in Fukushima Daiichi Nuclear Power Plants(1F),it is essential to infer the fuel debris *** particular,the molten metal spreading behavior is one of the vital phenomena in nuclear severe accidents because it determines the initial condition for further accident scenarios such as molten core concrete interaction(MCCI).In this study,the fundamental molten metal spreading experiments were performed with different outlet diameters and sample amounts to investigate the effect of the outlet for spreading-solidification *** the numerical analysis,the moving particle full-implicit method(MPFI),which is one of the particle methods,was applied to simulate the spreading *** the MPFI framework,the melting-solidification model including heat transfer,radiation heat loss,phase change,and solid fraction-dependent viscosity was developed and *** addition,the difference in the spreading and solidification behavior due to the outlet diameters was reproduced in the *** simulation results reveal the detailed solidification procedure during the molten metal *** is found that the viscosity change and the solid fraction change during the spreading are key factors for the free surface condition and solidified ***,it is suggested that the MPFI method has the potential to simulate the actual nuclear melt-down phenomena in the future.

关键词： molten metal spreading solidification particle method severe accident fuel debris decommissioning