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Noise Reduction and Surge Margin Improvement Using Tapered Diffuser Vane in a Centrifugal Compressor

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Journal of Thermal Science 2010年第1期19卷 21-25页

作者： Takashi Goto Eri Ohmoto yutaka Ohta Eisuke Outa Department of Applied Mechanics and Aerospace Engineering Waseda University Graduate Student Graduate School of Applied Mechanical EngineeringWaseda University

Improvement of surge margin and reduction of interaction tone noise radiated from a centrifugal compressor with a vaned diffuser is discussed from experiments and CFD *** types of one-side tapered diffuser vanes,which are shroud-and hub-side tapered vanes,were used in the *** height of the leading edge of the tapered vanes varied from 100% to 10%.Both types of tapered vanes are effective for the reduction of the interaction tone noise radiated from the compressor,because of the smaller interaction area between impeller-discharge flow and diffuser vane ***,the hub-side tapered diffuser vane suppresses the evolution of the leading-edge vortex,which causes reverse-flow in the diffuser ***,the hub-side tapered diffuser vane,which has an optimized diffuser leading edge shape,can improve the compressor pressure-rise characteristics at low-flow operation and can enlarge the surge margin.

关键词： Centrifugal compressor tapered diffuser vane interaction tone noise CFD

Boundary-representable partition of unity for image magnification

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Science China(Information Sciences) 2013年第11期56卷 216-227页

作者： NAGAI Yukie OHTAKE yutaka YOKOTA Hideo SUZUKI Hiromasa School of Engineering The University of Tokyo153-8904 Japan Bio-Research Infrastructure Construction Team ASI RIKEN 351-0198 Japan RCAST The University of Tokyo153-8904 Japan

This paper proposes a simple yet efective algorithm to magnify 2D/3D images with preserving discontinuities of *** algorithm is based on the partition of unity(PU)approximation,which ofers many advantages such as smooth representation,noise-robustness,and precise ***,PU encounters difculties when scaling images and maintaining boundaries within images owing to the nature of its *** overcome this problem,we propose an approximation that preserves *** is realized by dividing the local spherical support of PU into two parts along a locally detected discontinuity and by individually approximating intensities on each side of the *** algorithm is suitable for magnifying a variety of images,including scanned documents,pictures,and CT-scanned *** demonstrate the efectiveness of the proposed method,we show some experimental results for 2D/3D images.

关键词： image approximation partition of unity piecewise smooth function volume data magnification

Bandgap-tunable lateral and vertical heterostructures based on monolayer Mo1-xWxS2 alloys

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Nano Research 2015年第10期8卷 3261-3271页

作者： Yu Kobayashi Shohei Mori yutaka Maniwa Yasumitsu Miyata DepartmentofPhysics TokyoMetropolitanUniversityHachiojiTokyo192-0397Japan JST PRESTOKawaguchiSaitama332-0012Japan

The fabrication of heterostructures of two-dimensional semiconductors with specific bandgaps is an important approach to realizing the full potential of these materials in electronic and optoelectronic devices. Several groups have recently reported the direct growth of lateral and vertical heterostructures based on monolayers of typical semiconducting transition metal dichalcogenides （TMDCs） such as WSe2, MoSe2, WS2, and MoS2. Here, we demonstrate the single-step direct growth of lateral and vertical heterostructures based on bandgap-tunable Mo1-xWxS2 alloy monolayers by the sulfurization of patterned thin films of WO3 and MoO3. These patterned films are capable of generating a wide variety of concentration gradients by the diffusion of transition metals during the crystal growth phase. Under high temperatures, this leads to the formation of monolayer crystals of Mo1-xWxS2 alloys with various compositions and bandgaps, depending on the positions of the crystals on the substrates. Heterostructures of these alloys are obtained through stepwise changes in the ratio of W/Mo within a single domain during low-temperature growth. The stabilization of the monolayer Mo1-xWxS2 alloys, which often degrade even under gentle conditions, was accomplished by coating the alloys with other monolayers. The present findings demonstrate an efficient means of both studying and optimizing the optical and electrical properties of TMDC-based heterostructures to allow use of the materials in future device applications.

关键词： transition metaldichalcogenide Mo1-xWxS2 alloy heterostructure thin-film sulfurization photoluminescence stability

Next-generation regenerative therapy for ischemic stroke using peripheral blood mononuclear cells

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Neural Regeneration Research 2024年第11期19卷 2341-2342页

作者： Masato Kanazawa Itaru Ninomiya yutaka Otsu Masahiro Hatakeyama Department of Neurology Brain Research InstituteNiigata UniversityNiigataJapan

Stroke is the second leading cause of death and the third leading cause of disability worldwide after heart *** predict that stroke deaths and permanent disabilities will increase worldwide by the year ***-target therapies may be insufficient,because ischemic cerebral injury involves several ***-mediated therapies are ideal,because they target multiple cell types to enhance protection and recovery.

关键词： ischemic death cerebral

Synchrotron X-ray diagnostics of cutoff shape of nonthermal electron spectrum at young supernova remnants

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Research in Astronomy and Astrophysics 2014年第2期14卷 165-178页

作者： Ryo Yamazaki yutaka Ohira Makoto Sawada Aya Bamba Department of Physics and Mathematics Aoyama Gakuin University5-10-1 FuchinobeSagamihara 252-5258Japan

Synchrotron X-rays can be a useful tool to investigate electron accelera- tion at young supemova remnants （SNRs）. At present, since the magnetic field con- figuration around the shocks of SNRs is uncertain, it is not clear whether electron acceleration is limited by SNR age, synchrotron cooling, or even escape from the ac- celeration region. We study whether the acceleration mechanism can be constrained by the cutoff shape of the electron spectrum around the maximum energy. We derive analytical formulae of the cutoff shape in each case where the maximum electron en- ergy is determined by SNR age, synchrotron cooling and escape from the shock. They are related to the energy dependence of the electron diffusion coefficient. Next, we discuss whether information on the cutoff shape can be provided by observations in the near future which will simply give the photon indices and the flux ratios in the soft and hard X-ray bands. We find that if the power-law index of the electron spectrum is independently determined by other observations, then we can constrain the cutoff shape by comparing theoretical predictions of the photon indices and/or the flux ratios with observed data which will be measured by NuSTAR and/or ASTRO-H. Such study is helpful in understanding the acceleration mechanism. In particular, it will supply another independent constraint on the magnetic field strength around the shocks of SNRs.

关键词： acceleration of particles -- ISM: cosmic rays -- ISM: supernova rem-nants -- turbulence -- X-rays: ISM

A Blowdown Cryogenic Cavitation Tunnel and CFD Treatment for Flow Visualization around a Foil

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Journal of Thermal Science 2005年第4期14卷 346-351页

作者： yutaka ITO Kazuya SAWASAKI Naoki TANI Takao NAGASAKI Toshio NAGASHIMA Tokyo Institute of Technology G3-334259Nagatsuta-choMidori-kuYokohama226-8502Japan Honda Motor Co.Ltd. 2-1-1Minami-AoyamaMinato-kuTokyo107-8556Japan Japan Aerospace Exploration Agency 2-1-1SengenTsukuba305-8505Japan University of Tokyo 7-3-1HongoBunkyo-kuTokyo113-8656Japan

Cavitation is one of the major problems in the development of rocket engines. There have been few experimental studies to visualize cryogenic foil cavitation. Therefore a new cryogenic cavitation tunnel of blowdown type was built. The foil shape is “piano-convex”. This profile was chosen because of simplicity, but also of being similar to the one for a rocket inducer impeller. Working fluids were water at room temperature, hot water and liquid nitrogen. In case of Angle of Attack （AOA）=8°, periodical cavity departure was observed in the experiments of both water at 90℃ and nitrogen at -190℃ under the same velocity 10 m/sec and the same cavitation number 0.7. The frequencies were observed to be 110 and 90 Hz, respectively, and almost coincided with those of vortex shedding from the foil. Temperature depression due to the thermodynamic effect was confirmed in both experiment and simulation especially in the cryogenic cavitation.

关键词： cavitation tunnel cryogen CFD visualization simulation foil.

Context-sensitiveWeb service discovery over the bipartite graph model

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Frontiers of Computer Science 2013年第6期7卷 875-893页

作者： Rong ZHANG Koji ZETTSU yutaka KIDAWARA Yasushi KIYOKI Aoying ZHOU Software Engineering Institute East China Normal University National Institute of Information and Communications Technology Keio University

As service oriented architecture(SOA)matures,service consumption demand leads to an urgent requirement for service *** Web documents,services are intended to be executed to achieve objectives and/or desired goals of *** leads to the notion that service discovery should take the“usage context”of service into account as well as service content(descriptions)which have been well *** this paper,we introduce the concept of service context which is used to represent service *** query processing,both service content and service context are examined to identify *** propose to represent service context by a weighted bipartite graph *** on the bipartite graph model,we reduce the gap between query space and service space by query expansion to improve *** also design an iteration algorithm for result ranking by considering service context-usefulness as well as contentrelevance to improve ***,we develop a service search engine implementing this mechanism,and conduct some experiments to verify our idea.

关键词： Web service usage context bipartite graph model context-usefulness

Efficient gasification of wet biomass residue to produce middle caloric gas

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Particuology 2008年第5期6卷 376-382页

作者： Guangwen Xu Takahiro Murakami Toshiyuki Suda Hidehisa Tani yutaka Mito Research Laboratory IHI Co. Ltd. (IHI) Isogo-Ku Yokohama 235-8501 Japan State Key Laboratory of Multiphase Phase Complex System Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China Energy Research Division Kobe steel Co. Ltd. Kobe Hyogo 651-2271 Japan

Various process residues represent a kind of biomass resource already concentrated but containing water as much as 60 wt.%. These materials are generally treated as waste or simply combusted directly to generate heat. Recently, we attempted to convert them into middle caloric gas to substitute for natural gas, as a chemical or a high-rank gaseous fuel for advanced combustion utilities. Such conversion is implemented through dual fluidized bed gasification （DFBG）. Concerning the high water content of the fuels, DFBG was suggested to accomplish either with high-efficiency fuel drying in advance or direct decoupling of fuel drying/pyrolysis from char gasification and tar/hydrocarbon reforming. Along with fuel drying, calcium-based catalyst can be impregnated into the fuel, without much additional cost, to increase the fuel＇s gasification reactivity and to reduce tar formation. This article reports the Ca impregnation method and its resulting effects on gasification reactivity and tar suppression ability. Meanwhile, the principle of directly gasifying wet fuel with decoupled dual fluidized bed gasification （D-DFBG） is also highlighted.

关键词： High-water content biomass Catalytic gasification Dual fluidized bed gasification Decoupled gasification Calcium

Characterization of deformation transition in the rolled LZ91 magnesium alloy under tensile loading

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Journal of Magnesium and Alloys 2024年第8期12卷 3173-3179页

作者： yutaka Yoshida Jun-ichi Shibano Jyunpei Hagikura Ryuhei Misutani Yuto Monden Faculty of Engineering Kitami Institute of TechnologyKoen-choKitamiHokkaido 090-8507Japan Department of Mechanical Engineering Kitami Institute of TechnologyKoenchoKitamiHokkaido 090-8507Japan School of Regional Innovation and Social Design Engineering Intelligent Machines and Biomechanics Course Program Kitami Institute of TechnologyKoen-choKitamiHokkaido 090-8507Japan

In this study,the mechanical behavior of crystal group of hexagonal close-packed(hcp;αphase)and body-centered cubic(bcc;βphase)during tensile loading was investigated to elucidate the mechanism from elastic to plastic deformation transition of the rolled LZ91 Mg alloy using transmission-X-ray diffraction(transmission-XRD)measurement,transmission electron microscopy(TEM),scanning transmission electron microscopy(STEM),energy dispersive X-ray spectroscopy(EDS).The approximate proof stress of the LZ91 Mg alloy sample was found that the lattice strain retained the expanded state from 0.6%nominal strain,and the transmission-XRD measurement characterized the crystalline behavior during the transition by the integrated intensity of crystal group hcp(100).The lattice strain of bcc(110)decreased from the 0.6%nominal strain due to dislocation activity,which occurred nearβ/βgrain *** addition,we performed the analyses of electron energy loss spectroscopy(EELS)modes,the Li-K peak disappeared from the segregated Li regions of 10–60 nm nearβ/βgrain boundary at the nominal strain of 0.8%.Understanding this mechanical behavior during the elastic to plastic deformation transition by transmission-XRD is crucial for the development of Mg-Li alloys.

关键词： Magnesium-lithium alloy Plastic deformation X-ray diffraction Scanning/transmission electron microscopy Electron energy loss spectroscopy