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Solid State Synthesis and Thermoelectric Properties of Mg-Si-Ge System

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Journal of Materials Science & Technology 2005年第5期21卷 618-622页

作者： Renbo SONG Yazheng LIU tatsuhiko aizawa School of Materials Science and Engineering University of Science and Technology Beijing Beijing 100083 China Center for Collaborative Research The University of Tokyo Komaba 4-6-1 Meguro-ku Tokyo 153-8904 Japan

Thermoelectric materials, Mg2Si1-xGex （x=0, 0.2, 0.4, 0.6, 0.8, 1）, have been prepared by bulk mechanical alloying （BMA） and hot pressing （HP）. The electrical conductivity, Seebeck coefficient and thermal conductivity were measured from room temperature up to about 700 K. The electrical conductivity of all the samples increases with increasing temperature, while the Seebeck coefficient and thermal conductivity decrease with increasing temperature. Mg2Si and Mg2Si0.8Ge0.2 possess negative type of conductivity, while for other compounds it is positive. At the same time, the effect of hot processing condition on thermoelectric properties was also investigated. The maximum figure of merit of Mg2Si0.6Ge0.4 was obtained with the processing parameter of BMA at 600 cycles and hot pressing at 773 K and i GPa for i h.

关键词： Solid-state synthesis Mg2Si1-xGex Bulk mechanical alloying Thermoelectric Hot pressing

Thermoelectric Properties of Mg_2Si_(1-x)Sn_x Synthesized by Bulk Mechanical Alloying

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Chinese Journal of Aeronautics 2006年第B12期19卷 134-138页

作者： SONG Ren-bo LIU Ya-zheng tatsuhiko aizawa School of Material Science and Engineering University of Science and Technology Beijing Beijing 100083 China Jayram Office University of Toronto Shanghai International Building 6F 1-24-12 Shinkawa Chuo-ku Tokyo 104-0033 Japan

Bulk mechanical alloying （BMA） has been successfully applied to solid-state synthesis of p-type and n-type thermoelectric materials Mg2Si1-xSnx （x = 0, 0.2, 0.4, 0.6, 0.8, 1） from element-powders at the room temperature in a relatively short time. The electrical conductivity, the Seebeck coefficient and the thermal conductivity of the Mg2Si1-xSnx are quite sensitive to the x-content. With the x-content rising, the electrical conductivity increases. When x = 0.6, it reaches the lowest and Mg2Si shows an n-type of semi-conducting However, when x = 0.2 and T 〉525 K, the Seebeck coefficient of the samples will change the opposite way. While x≥0.4, the samples present a p-type of semi-conducting. The figure of merit, Z of Mg2Si1-xSnx will be obtained in the range from 300 K to 700 K. When x = 0.6, Z proves to be higher than that of other samples at 300 K≤ T≤650 K.

关键词： solid-state synthesis thermoelectric bulk mechanical alloying Mg2Si1-xSnx

Dry Machining Tool Design via Chlorine Ion Implantation

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材料热处理学报 2004年第05B期25卷 879-882页

作者： tatsuhiko aizawa Atsushi Mitsuo Shigeo Yamamoto Shinji Muraishi Taro Sumitomo Center for Collaborate Research University of Tokyo Tokyo JapanTokyo Metropolitan Industrial Research Institute Tokyo JapanTokyo Metropolitan Industrial Research Institute Tokyo JapanDepartment of Materials Science Technology Tokyo Institute of Technology Tokyo JapanCenter for Collaborate Research University of Tokyo Tokyo Japan

Dry machining has become a key issue to significantly reduce the wastes of used lubricants and cleaning agents and to improve the environmental consciousness for medical and food applications of special tooling. Since the tools and metallic works are in direct contact in dry, severe adhesive wear and oxidation are thought to occur even at the presence of hard protective coatings. Self-lubrication mechanism with use of lubricous oxide films is found to be effective for dry machining. Through the chlorine ion implantation to tools, titanium base oxides are in-situ formed on the tool surface. This oxide deforms elasto-plastically so that both friction coefficient and wear volume are reduced even in the high-speed cutting.

关键词：氯离子注入自动润滑 TiN涂层 TiCN涂层干机械加工

THREE DIMENSIONAL ELASTO-PLASTIC CONTACT BOUNDARY ELEMENT ANALYSIS FOR ROLLING WITH CONSIDERATION OF FRICTION

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Chinese Journal of Mechanical Engineering 1998年第1期11卷 63-69页

作者： Xiao, Hong Chen, Yiming Shen, Guangxian aizawa, tatsuhiko Kihara, Junji Yanshan Univ China

The boundary element method in framework is given to evaluate three dimensional frictional contact problems. Elasto plastic material behavior is taken into account by mean of an initial stress formulation and Von Mises yield criterion. The amount of tangential traction at contact surface is limited by Coulomb's friction law and constant shear rule. From some numerical results of a plate rolling problem, it is demonstrated here that the BEM can be used to efficiently and accurately analyze this class of forming problems.

关键词： Strip Rolling Boundary element method Elasto plasticity Contact Friction

Plasma Nitriding-Assisted Printing of Stainless Steel Punches for Micro-piercing Process

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Journal of Mechanics Engineering and Automation 2017年第1期7卷 1-11页

作者： tatsuhiko aizawa Tomomi Shiratori Department of Engineering and Design Shibaura Institute of Technology 3-9-14 Shibaura Minato-City Tokyo 108-8548 Japan R & D Center Komatsu Seiki Kosakusho Co. Ltd. Shiga-Kuwahara Ohaza Suwa-City Nagano 942-2 Japan

MEMS （micro-electric-mechanical-system） required for miniature, thin mechanical parts as a structural member; e.g., the miniature pumping system consisted of ten to twelve thin metallic plates before joining. At present, those thin shaped sheets were fabricated by the chemical etching. Their geometric inaccuracy as well as long leading time often became an engineering issue. Micro-piercing process was expected to make mass production of thin sheet products with complex and accurate geometry for much shorter leading time once the die for this micro-piercing was built in. In the present paper, a new plasma nitriding-assisted printing was proposed as an automatic production line to fabricate the micro-piercing punch. After preparation of CAD-data of the punch head, its two dimensional geometry was ink-jet printed directly on the AISI420 stainless steel die-substrate. The unprinted surface area was only plasma nitrided at 693 K for 14.4 ks to transform this two dimensional micro-pattern to the three dimensional hardness distribution in the AISI420 substrate. Through the mechanical removal of ink-jet printed area, the flat punch head with sharp edge comers was fabricated in much shorter duration time than the end-milling. SEM-EDX, surface profiling measurement as well as micro-hardness testing were employed to describe each step in the above plasma printing. The thin MEMS stainless steel part with a micro-pendulum as well as three S-letter shaped springs was taken for an example to describe this automatic production procedure of plasma printing from the CAD data mining to the micro-piercing punch finishing.

关键词： Plasma printing ink-jet printing plasma nitriding sand-blasting micro-piercing stainless steel punch.

High Density Plasma Nitriding of Al-Cu Alloys for Automotive Parts

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Journal of Physical Science and Application 2014年第4期4卷 255-261页

作者： tatsuhiko aizawa Shinji Muraishi Yoshio Sugita Department of Engineering and Design Shibaura Institute of Technology Tokyo 108-8548 Japan Department of Materials Science and Engineering Tokyo Institute of Technology Tokyo Japan YS-Electrical Industry Co. Ltd. Koufu 400-0043 Japan

Duralumin alloys have been utilized as structural components and parts for aircrafts, train-cars and so forth. Their high specific strength was attractive to those applications; however, their little corrosion resistance and low wear endurance became a fatal demerit in practical applications. In order to overcome these issues of high strength aluminum alloys, high density plasma nitriding is proposed as an effective surface treatment for duralumin. This process has a capability to control the RF- and DC-plasmas independently for nitriding. This enables us to temporally control and describe the plasma state by in-situ plasma diagnosis. This plasma diagnosis was instrumented to search for optimum processing condition to plasma nitriding the duralumin alloys of type A2011. Both type A2011 aluminum alloy plates and pipes were employed to describe the inner nitriding behavior for hardening the duralumin alloys by the present plasma nitriding.

关键词： Duralumin alloys A2011 high density plasma nitrding AIN precipitation hardening plates pipes heat sink.

Ionization of protoplanetary disks by galactic cosmic rays,solar protons,and supernova remnants

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Geoscience Frontiers 2017年第2期8卷 247-252页

作者： Ryuho Kataoka tatsuhiko Sato National Institute of Polar Research 10-3 Midori-choTachikawaTokyo190-8513Japan SOKENDAI 10-3 Midori-choTachikawaTokyo190-8513Japan Japan Atomic Energy Agency Shirakata 2-4TokaiIbaraki319-1195Japan

Galactic cosmic rays and solar protons ionize the present terrestrial atmosphere,and the air showers are simulated by well-tested Monte-Carlo simulations,such as PHITS *** use the latest version of PHITS to evaluate the possible ionization of protoplanetary disks by galactic cosmic rays（GCRs）,solar protons,and by supernova *** attenuation length of GCR ionization is updated as 118 g cm^-2,which is approximately 20% larger than the popular *** and soft possible spectra of solar protons give comparable and 20% smaller attenuation lengths compared with those from standard GCR spectra,respectively,while the attenuation length is approximately 10% larger for supernova ***,all of the attenuation lengths become 10% larger in the compound gas of cosmic abundance,e.g.128 g cm^-2 for GCRs,which can affect the minimum estimate of the size of dead zones in protoplanetary disks when the incident flux is unusually high.

关键词： Galactic cosmic rays Solar protons Supernova remnants Young Sun Protoplanetary disk T Tauri stars

Direct Simulation Methods for Scalar-Wave Envelopes in Two-Dimensional Layered Random Media Based on the Small-Angle Scattering Approximation

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Communications in Computational Physics 2008年第1期3卷 63-84页

作者： tatsuhiko Saito Haruo Sato Tsutomu Takahashi Earthquake Research Institute The University of TokyoYayoi 1-1-1Bunkyo-kuTokyo113-0032Japan. CREST Japan Science and Technology Agency(JST). Department of Geophysics Graduate School of ScienceTohoku UniversityAramaki-Aza-Aoba 6-3Aoba-kuSendaiMiyagi980-8578Japan. Institute for Research on Earth Evolution Japan Agency for Marine-Earth Science and TechnologyShowa-machi 3173-25Kanazawa-kuYokohamaKanagawa236-0001Japan.

This study presents stochastic methods to simulate wave envelopes in layeredrandom media. High-frequency Seismograms of small earthquakes are so complexdue to lithospheric inhomogeneity that seismologists often analyze wave envelopesrather than wave traces to quantify the subsurface inhomogeneity. Since thestatistical properties of the inhomogeneity vary regionally, it is important to developand examine direct envelope simulation methods for non-uniform random media. Asa simple example, this study supposes planewave propagation through two-layer randommedia in 2-D composed of weak and strong inhomogeneity zones. The characteristicspatial-scale of the inhomogeneity is supposed to be larger than the wavelength,where small-angle scattering around the forward direction dominates large-angle *** envelope simulation methods based on the small-angle scattering approximationare examined. One method is to solve a differential equation for the twofrequencymutual coherence function with the Markov approximation. The other isto solve the stochastic ray bending process by using the Monte Carlo method basedon the Markov approximation for the mutual coherence function. The resultant waveenvelopes of the two methods showed excellent coincidence both for uniform and fortwo-layer random media. Furthermore, we confirmed the validity of the two methodscomparing with the envelopes made from the finite difference simulations of *** two direct envelope simulation methods presented in this study can be a mathematicalbase for the study of high-frequency wave propagation through randomlyinhomogeneous lithosphere in seismology.

关键词： Seismic wave envelope random media.

Chronic hepatitis C virus infection and lipoprotein metabolism

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World Journal of Gastroenterology 2015年第36期21卷 10299-10313页

作者： Yoshio aizawa Nobuyoshi Seki Tomohisa Nagano Hiroshi Abe Department of Internal Medicine The Jikei University Katsushika Medical Center

Hepatitis C virus(HCV) is a hepatotrophic virus and a major cause of chronic liver disease,including hepatocellular carcinoma,worldwide. The life cycle of HCV is closely associated with the metabolism of lipids and lipoproteins. The main function of lipoproteins is transporting lipids throughout the body. Triglycerides,free cholesterol,cholesteryl esters,and phospholipids are the major components of the transported lipids. The pathway of HCV assembly and secretion is closely linked to lipoprotein production and secretion,and the infectivity of HCV particles largely depends on the interaction of lipoproteins. Moreover,HCV entry into hepatocytes is strongly influenced by lipoproteins. The key lipoprotein molecules mediating these interactions are apolipoproteins. Apolipoproteins are amphipathic proteins on the surface of a lipoprotein particle,which help stabilize lipoprotein structure. They perform a key role in lipoprotein metabolism by serving as receptor ligands,enzyme co-factors,and lipid transport carriers. Understanding the association between the life cycle of HCV and lipoprotein metabolism is important because each step of the life cycle of HCV that is associated with lipoprotein metabolism is a potential target for anti-HCV therapy. In this article,we first concisely review the nature of lipoprotein and its metabolism to better understand the complicated interaction of HCV with lipoprotein. Then,we review the outline of the processes of HCV assembly,secretion,and entry into hepatocytes,focusing on the association with lipoproteins. Finally,we discuss the clinical aspects of disturbed lipid/lipoprotein metabolism and the significance of dyslipoproteinemia in chronic HCV infection with regard to abnormal apolipoproteins.

关键词： Hepatitis C virus Apolipoprotein Lipo-viral partic