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Impacts of uneven surface heating of an ideal street canyon on airflows and indoor ventilation:Numerical study using OpenFOAM coupled with EnergyPlus

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Building Simulation 2022年第2期15卷 265-280页

作者： yuya Xiong Hong Chen School of Architecture and Urban Planning Huazhong University of Science and TechnologyWuhanHubei430000China

In the daytime,building facades and ground surfaces are heated by solar radiation,and the resulting buoyancy can change the flow field inside street *** this study,the impacts of uneven and time-varying heating of surfaces inside an ideal urban street canyon(aspect ratio=1)on single-sided indoor natural ventilation are *** work introduces a methodology for a numerical approach based on the coupling between a computational fluid dynamics(CFD)model and an energy balance ***,EnergyPlus is employed to calculate the time-varying and uneven surface *** are performed at four typical study times(05:00,09:00,15:00,20:00)during a hot summer day(July 15)in Wuhan,***,the surface temperature results are transferred to OpenFOAM for CFD *** inlet wind velocities(U_(ref))are *** results show that for a relatively strong ambient wind(U_(ref)=3 m/s),the buoyancy caused by surface heating does not significantly change the airflow structures and indoor ventilation compared with those in the isothermal ***,for a weak ambient wind(U_(ref)=0.5 m/s),the airflow structures inside the street canyon vary with the time of ***,the average air exchange rate(ACH)differs by-25.0% to 15.9%compared with that in the isothermal case,and the ACH of a single room increases by up to 2710%.The results indicate that the surface-heating-induced buoyancy is nonnegligible and should be carefully investigated,especially for weak ambient winds.

关键词： uneven surface temperature indoor ventilation urban canyon OpenFOAM EnergyPlus

Fatigue Property of Additively Manufactured Ti-6Al-4V under Nonproportional Multiaxial Loading

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Chinese Journal of Mechanical Engineering 2021年第6期34卷 76-84页

作者： yuya Kimura Fumio Ogawa Takamoto Itoh Graduate School of Science&Engineering Ritsumeikan UniversityShiga 5258577Japan Fracture and Reliability Research Institute Graduate School of Tohoku UniversityMiyagi 9808579Japan Department of Mechani-cal Engineering Ritsumeikan UniversityShiga 5258577Japan

The low cycle fatigue strength properties of the additively manufactured Ti-6Al-4V alloy are experimentally investi-gated under proportional and nonproportional multiaxial *** fatigue tests were conducted using hollow cylinder specimens with and without heat treatments,at room temperature in *** fatigue tests were conducted:one for proportional loading and one for nonproportional *** proportional loading was represented by a push-pull strain path(PP)and the nonproportional loading by a circle strain path(Cl).The failure lives of the additively manufactured specimens were clearly reduced drastically by internal voids and ***,the sizes of the defects were measured,and the defects were found not to cause a reduction in fatigue strength above a critical *** fracture surface was observed using scanning electron microscopy to investigate the fracture mechanisms of the additively manufactured specimens under the two types of strain *** fracture patterns were recognized for each strain paths;however,both showed retention of the crack propagation,despite the presence of numerous defects,probably because of the interaction of the *** crack propagation properties of the materials with numerous defects under nonproportional multiaxial loading were clarified to increase the reliability of the additively manufactured components.

关键词： Additive manufacturing Ti-6Al-4V Low cycle fatigue Multiaxial stress Nonproportional loading Internal defect

Wide and Fast Wavelength-Swept Fiber Lasers Based on Dispersion Tuning and Their Application to Optical Coherence Tomography

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Photonic Sensors 2013年第4期3卷 320-331页

作者： Shinji YAMASHITA yuya TAKUBO Research Center for Advanced Science and Technology (RCAST) The University of Tokyo 4-6-1 Komaba Meguro-kuTokyo 153-8904 Japan

We recently proposed a new class of wavelength-swept lasers for swept-source optical coherence tomography （SS-OCT）. It uses the same gain medium with the conventional swept lasers, but does not require any tunable filters. It is based on a principle called ＂dispersion tuning＂, in which a highly dispersive medium is inserted in the laser cavity, and loss/gain modulation is applied to mode-lock the laser. Since the cavity contains no mechanical components, such as tunable filters, we could achieve the very high sweep rate. In this review paper, we describe the principle of the dispersion-tuned swept lasers in detail and present our recent work on the application to the SS-OCT system.

关键词： OCT swept lasers dispersion tuning

Numerical Analysis of Turbulent Sonic Jets from Two-Dimensional Convergent Nozzles

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Journal of Thermal Science 2011年第2期20卷 133-138页

作者： Hideo KASHIMURA yuya MASUDA Yoshiaki MIYAZATO Kazuyasu MATSUO Department of Control and Information Systems Engineering Kitakyushu National College of Technology 5-20-1ShiiKokuraminami-kuKitakyushuFukuoka802-0985JAPAN Department of Mechanical Systems Engineering The University of Kitakyushu1-1HibikinoWakamatsu-kuKitakyushuFukuoka808-0135JAPAN

The numerical analysis of a turbulent sonic jet from a two-dimensional convergent nozzle has been carried out using the compressible k-? turbulence model and TVD finite difference scheme. Numerical conditions have been varied over a range of operating pressure ratios from 1.893 to 6.0 which cover the jet flow conditions from correctly expanded to underexpanded. Numerical flow visualization of sonic jet structure using the computer schlieren, a relation between shock cell length in the jet with the operating pressure ratio and the pressure distribution along jet centerline are obtained. Also, a transition process of a two-dimensional sonic jet from correctly expanded to underexpanded conditions is shown in detail and a flow model of jet structure is proposed.

关键词： Sonic nozzle Underexpanded jet Shock cell length κ-ε turbulence model Numerical analysis

A New One-dimensional Chain Compound Constructed by {Mo_8O_(28)} units via Corner-sharing

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Chinese Journal of Structural Chemistry 2005年第2期24卷 214-218页

作者： yuya-Qin YANGWen-Bin WUChuan-De LUCan-Zhong StateKeyLaboratoryofStructuralChemistry FujianInstituteofResearchontheStructureofMatterTheChineseAcademyofSciencesFuzhouFujian350002China

The title compound, {(H3O)4(NH4)4[Mo8O28]?2H2O}n 1, has been synthesized from the reaction of Zn(OAc)2 and (NH4)6Mo7O24?4H2O in aqueous solution at ambient tempe- rature, and its crystal structure was determined by X-ray single-crystal analysis with the following crystallographic data: monoclinic system, space group P21/n, a = 9.5234(6), b = 11.3235(8), c = 14.8812(10) ?, β = 107.467(2)o, V = 1530.77(18) ?3, Z = 4, F(000) = 1336, μ = 3.293 mm-1 and Dc = 3.037 g/cm3. The final R = 0.0619 for 2691 observed reflections (I > 2σ(I)). X-ray crys- tal structure analysis showed that the novel one-dimensional chain compound is built up by basic {Mo8O28} units via single μ2-O, and such chains are further linked into a three-dimensional net- work by hydrogen bonds.

关键词： polyoxomolybdate octamolybdate one-dimensional chain

Effect of bending and tension deformation on the texture evolution and stretch formability of Mg-Zn-RE-Zr alloy

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International Journal of Minerals,Metallurgy and Materials 2022年第7期29卷 1334-1342页

作者： yuya Ishiguro Xinsheng Huang Yuhki Tsukada Toshiyuki Koyama Yasumasa Chino Department of Materials Design Innovation Engineering Nagoya UniversityFuro-choChikusa-kuNagoya464-8603Japan Multi-Material Research Institute National Institute of Advanced Industrial Science and Technology2266-98AnagahoraSimo-shidami Moriyama-kuNagoya463-8560Japan

Bending and tension deformations were performed on Mg-1.3 wt%Zn-0.2 wt%RE-0.3 wt%Zr(ZEK100)alloy sheets that initially had a transverse direction(TD)-split *** effects of bending and tension deformations on the texture formation and room-temperature formability of specimens were *** specimen subjected to 3-pass bending and tension deformations exhibited an excellent Erichsen value of 9.6 ***,the Erichsen value deterioration was observed in the specimen subjected to 7-pass *** rolling direction-split texture developed on the surface with an increasing pass number of ***,the clear TD-split texture remained at the central *** a result,a quadrupole texture was macroscopically developed with an increasing pass number of *** reduction in anisotropy by the formation of the quadrupole texture is suggested to be the main reason for the improvement in stretch *** contrast,the generation of coarse grains near the surface is suggested to be the direct cause for the deterioration of the stretch formability of the specimen subjected to 7-pass deformations.

关键词： magnesium alloy texture stretch formability bending and tension deformation mechanical properties

Channel Attention GAN-Based Synthetic Weed Generation for Precise Weed Identification

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Plant Phenomics 2024年第2期6卷 257-268页

作者： Tang Li Motoaki Asai Yoichiro Kato yuya Fukano Wei Guo Graduate School of Agricultural and Life Sciences The University of TokyoTokyo 188-0002Japan Institute for Plant Protection National Agriculture and Food Research OrganizationFukushima 960-2156Japan Graduate School of Horticulture Chiba UniversityChiba 271-0092Japan

Weed is a major biological factor causing declines in crop ***,widespread herbicide application and indiscriminate weeding with soil disturbance are of great concern because of their environmental ***-specific weed management(SSWM)refers to a weed management strategy for digital agriculture that results in low energy *** learning is crucial for developing SSWM,as it distinguishes crops from weeds and identifies weed ***,this technique requires substantial annotated data,which necessitates expertise in weed science and agronomy.

关键词： identification attention generation channel gan-based precise synthetic weed

Classification of solar sail attitude dynamics with and without angular momentum

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Astrodynamics 2019年第3期3卷 207-216页

作者： Yuichi Tsuda Go Ono yuya Mimasu Institute of Space and Astronautical Science Japan Aerospace Exploration AgencySagamihara252-5210Japan Japan Aerospace Exploration Agency Sagamihara252-5210Japan

This paper describes attitude dynamics properties of spinning,momentum-biased and zero-momentum solar sail *** model called“Generalized Sail Dynamics Model”(GSDM)is introduced,which can deal with general and practical sail configurations,such as arbitrary optical property distribution,shape and surface *** stability criteria and other key dynamical characteristics are derived and compared by compact analytical equations induced from the *** newly derived zero-momentum sail dynamics is compared with that of spinning and momentum-biased *** is shown that the spinning and momentum sails have an advantage in terms of dynamical stability whereas zero-momentum sails are only statically *** this special property,angular momentum-stabilized sails can realize a sun-pointing stable attitude with almost zero-fuel,which are discussed with actual space flight experience of the JAXA’s two interplanetary missions,IKAROS and Hayabusa2.

关键词： solar sail attitude dynamics stability solar system exploration

Simultaneous estimation of spacecraft position and asteroid diameter during final approach of Hayabusa2 to Ryugu

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Astrodynamics 2020年第2期4卷 163-175页

作者： Yuki Takao yuya Mimasu Yuichi Tsuda Institute of Space and Astronautical Science Japan Aerospace Exploration AgencySagamihara252-5210Japan

This paper presents the optical navigation results of the asteroid explorer Hayabusa2 during the final rendezvous approach phase with the asteroid *** orbit determination of Hayabusa2 during the cruising phase uses a triangulation-based method that estimates the probe and asteroid orbits using the directions from which they are ***,the asteroid size is available as optical information just prior to *** size information allows us to estimate the relative distance between the probe and the asteroid with high accuracy,that is strongly related to the success or failure of the *** this study,the relative distance and asteroid size in real space are simultaneously estimated in real time by focusing on the rate of change of the asteroid size observed in sequential *** real-time estimation results coincided with those of precise analyses performed after arrival.

关键词： asteroids small bodies optical navigation size estimation orbit determination real time