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Flow Visualization around a Double Wedge Airfoil Model with Focusing Schlieren System

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Journal of Thermal Science 2006年第1期15卷 31-36页

作者： Masashi kASHITANI Yutaka yamaguchi Department of Aerospace Engineering National Defense Academy 1-10-20 Hashirimizu Yokosuka Kanagawa 239-8686Japan

在现在的学习，双楔机翼模型的空气动力学的特征被把吃惊试管用作一条断断续续的风隧道在接近音速的流动调查。司机和吃惊试管的驾驶气体是干燥空气。两倍楔的机翼模型有 58 公里的跨度， 75 公里和它的最大的厚度是的弦长度 c = 7.5 ... 详细信息

在现在的学习，双楔机翼模型的空气动力学的特征被把吃惊试管用作一条断断续续的风隧道在接近音速的流动调查。司机和吃惊试管的驾驶气体是干燥空气。两倍楔的机翼模型有 58 公里的跨度， 75 公里和它的最大的厚度是的弦长度 c = 7.5 公里。双楔机翼模型的顶从前缘位于 35% 弦长度。马赫数字从 0.80 ～ 0.88 的热气体的范围，和雷纳兹数字基于弦长度是 3.11 脳 105 锝 ? 3.49 脳 105 分别地。流动可视化被能设想三个维的流动领域的锋利的集中 schlieren 方法执行。结果证明现在的系统能设想比以前的系统清楚的接近音速的 flowfield，并且冲击波在测试节跨度的中心介绍是设想的关键词冲击波 - schlieren 方法 - 接近音速的流动 - 两倍楔 - 机翼模型 CLC 数字 V211.

关键词：振动波纹影法跨音速流双重楔机翼模型

Computer-generated image hologram

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Chinese Optics Letters 2011年第12期9卷 20-23页

作者： Takeshi yamaguchi Hiroshi Yoshikawa Department of Electronics and Computer Science College of Science and Technology

We investigate the computer-generated hologram with full parallax and which can be reconstructed with white light. The object of the hologram is processed from three-dimensional computer graphics polygon data and has shaded surface for hidden surface removal. The optically reconstructed image from the printed hologram is evaluated.

关键词： Computer-generated image hologram CGH

Computer-generated holograms for 3D display(Invited Paper)

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Chinese Optics Letters 2009年第12期7卷 1079-1082页

作者： Hiroshi Yoshikawa Takeshi yamaguchi Department of Electronics and Computer Science Nihon University

We have been studying various types of computer-generated holograms for three-dimensional （3D） displays both for a real-time holographic video display and a hard copy, or a printed hologram. For the hard copy output, we have developed a direct fringe printer, which is achieved to print over 100 gigapixels computer-generated hologram with 0.44μm pitch. In this paper, we introduce our recent progresses on the rainbow hologram, the cylindrical holograms, and the disk hologram for 3D display.

关键词： Computer-generated holograms for 3D display Figure

Potential Oscillations of a Stainless Steel Electrode during Galvanostatic Polarization in a Mixed Solution of Sulfuric and Chromic Acids

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International Journal of Minerals,Metallurgy and Materials 1998年第3期12卷 134-139页

作者： k Ogura W Lou M Nakayama T Fukume(Department of Applied Chemistry, yamaguchi University, Ube 755, Japan Department of Applied Chemistry Yamaguchi University Ube 755 Japan

Potential oscillations of a stainless steel electrode galvanostatically anodized have been observed in amixture of chromic and sulfuric acids. The potential regularly oscillated between 1.6 V vs. SCE (lower) and 2.1V(upper) with a certain frequency. The potential values are affected neither by the composition of chromic and sulfu-ric acids nor by the magnitude of applied current density although the potential frequency is very sensitive to theseparameters. This phenomenon is interpreted in terms of the repeated formation and disappearance of the saturatedlayer of dichromate ions on the electrode surface. Such scheme is consistent with the in situ FTIR spectroscopicresult that the concentration of Cr2O ions on the electrode surface increased with time during the polarization atthe lower potential but the change in concenetion of Cr2O ions was negligible at the higher potential.

关键词： stainless steel electrode potential galvanostatic polarization

Performance of Bayesian Propensity Score Adjustment for Estimating Causal Effects in Small Clinical Trials

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Open Journal of Statistics 2023年第1期13卷 1-15页

作者： Airi Takagi Takuhiro yamaguchi Clinical Research Data Center Tohoku University Hospital Sendai Japan Department of Biostatistics Tohoku University Graduate School of Medicine Sendai Japan

Propensity score (PS) adjustment can control confounding effects and reduce bias when estimating treatment effects in non-randomized trials or observational studies. PS methods are becoming increasingly used to estimate causal effects, including when the sample size is small compared to the number of confounders. With numerous confounders, quasi-complete separation can easily occur in logistic regression used for estimating the PS, but this has not been addressed. We focused on a Bayesian PS method to address the limitations of quasi-complete separation faced by small trials. Bayesian methods are useful because they estimate the PS and causal effects simultaneously while considering the uncertainty of the PS by modelling it as a latent variable. In this study, we conducted simulations to evaluate the performance of Bayesian simultaneous PS estimation by considering the specification of prior distributions for model comparison. We propose a method to improve predictive performance with discrete outcomes in small trials. We found that the specification of prior distributions assigned to logistic regression coefficients was more important in the second step than in the first step, even when there was a quasi-complete separation in the first step. Assigning Cauchy (0, 2.5) to coefficients improved the predictive performance for estimating causal effects and improving the balancing properties of the confounder.

关键词： Bayesian Estimation Causal Inference Propensity Score Quasi-Complete Separation Prior Distribution

Numerical Study on Low-Reynolds Compressible Flows around Mars Helicopter Rotor Blade Airfoil

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Journal of Flow Control, Measurement & Visualization 2023年第2期11卷 30-48页

作者： Takuma yamaguchi Masayuki Anyoji Interdisciplinary Graduate School of Engineering Sciences Kyushu University Fukuoka Japan

High-speed rotor rotation under the low-density condition creates a special low-Reynolds compressible flow around the rotor blade airfoil where the compressibility effect on the laminar separated shear layer occurs. However, the compressibility effect and shock wave generation associated with the increase in the Mach number (M) and the trend change due to their interference have not been clarified. The purpose is to clear the compressibility effect and its impact of shock wave generation on the flow field and aerodynamics. Therefore, we perform a two-dimensional unsteady calculation by Computational fluid dynamics (CFD) analysis using the CLF5605 airfoil used in the Mars helicopter Ingenuity, which succeeded in its first flight on Mars. The calculation conditions are set to the Reynolds number (Re) at 75% rotor span in hovering (Re = 15,400), and the Mach number was varied from incompressible (M = 0.2) to transonic (M = 1.2). The compressible fluid dynamics solver FaSTAR developed by the Japan aerospace exploration agency (JAXA) is used, and calculations are performed under multiple conditions in which the Mach number and angle of attack (α) are swept. The results show that a flow field is similar to that in the Earth’s atmosphere above M = 1.0, such as bow shock at the leading edge, whereas multiple λ-type shock waves are observed over the separated shear layer above α = 3° at M = 0.80. However, no significant difference is found in the Cp distribution around the airfoil between M = 0.6 and M = 0.8. From the results, it is found that multiple λ-type shock waves have no significant effect on the airfoil surface pressure distribution, the separated shear layer effect is dominant in the surface pressure change and aerodynamic characteristics.

关键词： CFD CLF5605 Rotor Blade Airfoil Compressibility Effect Low-Reynolds Number Mars Helicopter Separation Bubble Shock Wave

pH-controlled hydrothermal synthesis of titanium phosphates and their powder properties

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Journal of Advanced Ceramics 2014年第4期3卷 326-331页

作者： Hiroaki ONODA Taisuke yamaguchi Department of Informatics and Environmental Sciences Kyoto Prefectural University1-5Shimogamo Nakaragi-cyoSakyo-kuKyoto 606-8522Japan

Titanium phosphates were prepared from titanium chloride and sodium pyrophosphate at various pH in hydrothermal process as a novel white pigment for *** chemical composition,powder properties,photo catalytic activity,colour phase and smoothness were *** obtained materials had a higher Ti/P ratio than that used in preparation conditions because of the formation of titanium oxide and *** samples prepared at pH=4 had particles smaller than 100μ*** phosphates had less photo catalytic activity to protect the sebum on the *** obtained materials in hydrothermal process and their thermal products at 100℃showed high reflectance in the range of visible light.

关键词： titanium phosphates pyrophosphate pH photo catalytic activity smoothness

Estimating reflectance and shape of objects from a single cartoon-shaded image

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Computational Visual Media 2017年第1期3卷 21-31页

作者： Hideki Todo Yasushi yamaguchi Tokyo University of Technology The University of Tokyo

Although many photorealistic relighting methods provide a way to change the illumination of objects in a digital photograph, it is currently difficult to relight digital illustrations having a cartoon shading style. The main difference between photorealistic and cartoon shading styles is that cartoon shading is characterized by soft color quantization and nonlinear color variations that cause noticeable reconstruction errors under a physical reflectance assumption, such as Lambertian reflection. To handle this non-photorealistic shading property, we focus on shading analysis of the most fundamental cartoon shading technique. Based on the color map shading representation, we propose a simple method to determine the input shading as that of a smooth shape with a nonlinear reflectance property. We have conducted simple ground-truth evaluations to compare our results to those obtained by other approaches.

关键词： non-photorealistic rendering cartoon shading relighting quantization

Review: Prediction of Unexpected Fluid-Induced Vibration in Pipeline Network

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World Journal of Mechanics 2022年第2期12卷 17-40页

作者： Ryuhei yamaguchi Makoto Ohta Institute of Fluid Science Tohoku University Sendai Japan

This review considers unexpected destructive disasters involving fluid power plants, such as nuclear electric power plants and fluid power plants. It specifically addresses the possibility of fluid vibration induced in a pipeline network of such a plant. The authors investigate the flow oscillation induced within a T-junction for laminar steady flow at a Reynolds number less than 103 and clarify that there is a periodic fluid oscillation with a constant Strouhal number independent of several flow conditions. Generally, a nuclear electric power plant is constructed using straight pipes, elbows, and T-junctions. Indeed, a T-Junction is a basic fluid element of a pipeline network. The flow in a fluid power plant is turbulent. There are peculiar flow phenomena that occur at high Reynolds numbers, which are also seen in other flow situations;e.g., kaman vortices are observed around a circular cylinder in low Reynolds numbers, around structures like bridges and downstream of islands in oceans. Although the flow situation of a T-junction and elbow in a fluid power plant, such as the fluid suddenly changing its flow direction is turbulent flow, the authors mention the possibility of the fluid-induced vibration of a pipeline network.

关键词： Fluid-Induced Vibration Flow Oscillation Tube Flow Laminar Steady Flow Fluid Power Plant