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Thermal ageing of soft and hard epoxy resins

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High Voltage 2023年第1期8卷 12-20页

作者： Yoshimichi Ohki Naoshi hirai Research Institute for Materials Science and Technology Waseda UniversityShinjuku-kuTokyoJapan

Two kinds of epoxy resin,a soft one with rubber-based additives and an ordinary hard one,are used as electrical insulators and airtight sealants in electrical penetrations in nuclear power plants(NPPs).Knowing how they behave under adverse environments is important for the safe operation of *** this regard,we gave artificial thermal ageing treatment to the two resins by heating them in air at various *** resins were then subjected to mechanical,thermal,and dielectric *** a result,it has become clear that the soft epoxy resin becomes hard,while its permittivity and loss factor decrease as the heating becomes *** glass transition tends to occur at a high temperature in the soft epoxy resin when it was *** these changes,the soft resin tends to exhibit similar behaviour in various properties to that of the unaged hard *** the other hand,the hard one is hardly affected by the simulated thermal ***,both resins can be useable in NPPs.

关键词： resin resins heated

Synthesis and sintering of samarium rich SmS_x and its electrical property

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Journal of Rare Earths 2016年第10期34卷 1042-1047页

作者： Liang Li Shinji hirai Yohei Tasaki Department of Materials Science and Engineering Muroran Institute of Technology

Non-stoichiometric samarium monosulfide（SmS_x, 0.55≤x≤1.2） was synthesized from Sm_2S_3 and SmH_3 at 1273 K for 3 h under vacuum. The influence of reaction ratio of Sm_2S_3 to SmH_3 on the fabrication of SmS_x was investigated. The fabrication of SmS required the molar ratio of Sm_2S_3 to SmH_3 above 1. Lattice parameter of synthetic SmS_x increased firstly and then decreased to saturate following with the addition of SmH_3 content. SmS_x compact was sintered at 1373 K by spark plasma sintering. Density of synthetic SmS_x was about 99% of theory density. Seebeck coefficient of n-type semiconductor Sm Sx decreased as temperature rose. The absolute value was distributed between 170–280 μV/K. The electrical resistivity of SmS_x（0.86≤x≤1.07） decreased with temperature increasing and showed similar temperature dependence. The surplus Sm which randomly distributed in the SmS_x（0.55≤x≤0.75） matrix led to a remarked reduction of electrical resistivity. The optimized power factor for SmS_（0.6） and Sm S_（0.75） could reach 1500 μW/（K^2·m） at 600 K.

关键词： samarium monosulfide SmH_3 Seebeck coefficient electrical resistivity rare earths

"Cap and glycosylate"strategy for direct radical functionalization of native sugars

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Science Bulletin 2024年第20期69卷 3163-3165页

作者： Hiroaki Matoba Go hirai Graduate School of Pharmaceutical Sciences Kyushu UniversityFukuoka 812-8582Japan

Glycoconjugates are biologically significant molecules,but their precise role in many biological phenomena remains unclear,largely due to their heterogeneity and complexity,as well as the dynamic enzymatic remodeling/hydrolysis of glycan ***,for mechanistic studies,it is desirable to use metabolically stable mimics of *** this context,S-,Se-,and notably C-linked glycoconjugates have emerged as attractive targets,leading to the development of numerous synthetic methods[1–3].

关键词： sugar hydrolysis attractive

Broadband FIR absorption spectra of lowdensity polyethylene sheets containing six different antioxidants and estimation of their contents by chemometric analysis

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High Voltage 2019年第3期4卷 161-166页

作者： Takaaki Ogishima Chiaki Kuroda Naoshi hirai Yoshimichi Ohki Department of Electrical Engineering and Bioscience Waseda UniversityShinjuku-kuTokyo 169-8555Japan Research Institute for Materials Science and Technology Waseda UniversityShinjuku-kuTokyo 169-8555Japan Cooperative Major in Nuclear Energy Waseda UniversityShinjuku-kuTokyo169-8555Japan

Antioxidants are usually added to polymeric insulating materials to suppress oxidative ***,the details of antioxidant added to a polymer are often not *** the other hand,compared to mid-infrared absorption spectroscopy,terahertz(THz)absorption spectroscopy,and far-infrared(FIR)absorption spectroscopy have not been performed so *** on the above backgrounds,six different kinds of antioxidants were added into low-density polyethylene sheets with four different contents,and their THz and FIR absorption spectra were *** a result,it has become clear that each antioxidant shows its specific absorption peaks,by which the antioxidants can be ***,the antioxidant content can be estimated by the absorption intensity of the specific peak.A chemometric analysis can make the estimation more accurately than a simple comparison of absorption intensity.

关键词： FIR absorption estimation

Activation of hypoxia-inducible factor 1 attenuates periapical inflammation and bone loss

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International Journal of Oral Science 2018年第2期10卷 92-101页

作者： Kimito hirai Hisako Furusho Kiichi Hirota Hajime Sasaki Department of Cariology Restorative Sciences & Endodontics University of Michigan School of Dentistry Department of Immunology and Infectious Diseases The Forsyth Institute Department of Oral and Maxillofacial Pathobiology Hiroshima University Department of Human Stress Response Science Institute of Biomedical Science Kansai Medical University

Hypoxia（low oxygen level） is an important feature during infections and affects the host defence mechanisms. The host has evolved specific responses to address hypoxia, which are strongly dependent on the activation of hypoxia-inducible factor 1（HIF-1）.Hypoxia interferes degradation of HIF-1 alpha subunit（HIF-1α）, leading to stabilisation of HIF-1α, heterodimerization with HIF-1 beta subunit（HIF-1β） and subsequent activation of HIF-1 pathway. Apical periodontitis（periapical lesion） is a consequence of endodontic infection and ultimately results in destruction of tooth-supporting tissue, including alveolar bone. Thus far, the role of HIF-1 in periapical lesions has not been systematically examined. In the present study, we determined the role of HIF-1 in a wellcharacterised mouse periapical lesion model using two HIF-1α-activating strategies, dimethyloxalylglycine（DMOG） and adenovirusinduced constitutively active HIF-1α（CA-HIF1 A）. Both DMOG and CA-HIF1 A attenuated periapical inflammation and tissue destruction. The attenuation in vivo was associated with downregulation of nuclear factor-κappa B（NF-κB） and osteoclastic gene expressions. These two agents also suppressed NF-κB activation and subsequent production of proinflammatory cytokines by macrophages. Furthermore, activation of HIF-1α by DMOG specifically suppressed lipopolysaccharide-stimulated macrophage differentiation into M1 cells, increasing the ratio of M2 macrophages against M1 cells. Taken together, our data indicated that activation of HIF-1 plays a protective role in the development of apical periodontitis via downregulation of NF-κB, proinflammatory cytokines, M1 macrophages and osteoclastogenesis.

关键词： CA Activation hypoxia-inducible factor attenuates periapical inflammation bone loss HIF

Experimental investigation of the degradation mechanism of silicone rubber exposed to heat and gamma rays

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High Voltage 2017年第2期2卷 92-101页

作者： Shugo Hanada Maki Miyamoto Naoshi hirai Liuqing Yang Yoshimichi Ohki Department of Electrical Engineering and Bioscience Waseda University3-4-1 OhkuboShinjuku-kuTokyoJapan Research Institute for Materials Science and Technology Waseda University2-8-26 Nishi-WasedaShinjuku-kuTokyoJapan State Key Laboratory for Electrical Insulation and Power Equipment Xi'an Jiaotong UniversityXi'anPeople's Republic of China Cooperative Major in Nuclear Energy Waseda University3-4-1 OhkuboShinjuku-kuTokyoJapan

Cable-grade silicone rubber was aged thermally or by combining heat and gamma-ray radiation,and resultant changes in chemical,thermal,mechanical and electrical properties were *** experimental results obtained in these analyses are clearly consistent with the mechanism that silicone rubber is degraded by forming cross-linked structures via formation of abundant siloxane *** further progress of degradation,decomposition becomes *** these mechanisms,mechanical properties deteriorate dramatically by losing *** the real and imaginary parts of complex permittivity decrease,which is a contrastive difference from typical ageing behaviour of organic insulating *** addition,both the elongation at break and indenter modulus are good indicators of degradation of silicone rubber.

关键词： rubber mechanism modulus

Biomimetic Riblets Inspired by Sharkskin Denticles： Digitizing, Modeling and Flow Simulation

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Journal of Bionic Engineering 2018年第6期15卷 999-1011页

作者： Mariko Miyazaki Yuji hirai Hiroshi Moriya Masatsugu Shimomura Akihiro Miyauchi Hao Liu Hitachi Ltd. 832-2 Horiguchi Hitachinaka Ibaraki 312-0034 Japan Chitose Institute of Science and Technology 758-65 Bibi Chitose Hokkaido 066-8655 Japan Tokyo Medical Dental University 2-3-10 Kanda-Surugadai Chiyodaku Tokyo 101-0062 Japan Chiba University 1-33 Yayoi-cho Inage-ku Chiba 263-8522 Japan

While sharkskin surface roughness in terms of denticle morphology has been hypothesized but remains yet controversial to be capable of achieving turbulent flow control and drag reduction, sharkskin-inspired ＂riblets＂ have been reported to be an effective biomimetic design. Here we address an integrated study of biomimetic riblets inspired by sharkskin denticles by combining 3D digitizing and mod- eling of＂fresh＂ denticles and computational fluid dynamic modeling of turbulent flows on a rough surface with staggered denticles and hound-tooth-patterned grooves. Realistic microstructures of denticles in five shark species of Galapagos, great white, whitetip reef, blacktip reef, and hammerhead sharks were first measured and digitized in three fold：（1） 2D imaging of lubricated sharkskin in a wet state by means of a ＂nano-suit＂ technique with a Field-Emission Scanning Electron Microscope （FE-SEM）; （2） 3D structures of sharkskin denticles with a micro-focus X-ray CT; and （3） single denticles of the five shark species in a 3D manner with 3D-CAD. The denticles at mid-body location in the five species were observed to have a structure of five non-uniform-ridges （herein termed ＂non-uniform grooves＂） with Angles Of Inclination （AOI） ranging over 20° - 32°. Hydrodynamics associated with the unique five-ridge denticles were then in- vestigated through modeling turbulent flow past a denticle-staggered skin surface. We further constructed a biomimetic riblet model inspired by the non-uniform grooves and investigated the hydrodynamic effects of height-to-spacing ratios of mid-ridge and side-ridges. Our results indicate that the morphological non-uniformity in sharkskin denticles likely plays a critical role in passively controlling local turbulent flow and point to the potential of denticle-inspired biomimetic riblets for turbulent-flow control in aquatic vehicles as well as other fluid machinery.

关键词： sharkskin denticles biommetic riblets 3D digitizing computational fluid dynamics

Wetting of Au and Ag particles on monocrystalline graphite substrates

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Rare Metals 2006年第5期25卷 469-472页

作者： Joonho Lee Toshihiro Tanaka Kazufumi Seo Nobumitsu hirai Jung-Goo Lee Hirotaro Mori Department of Materials Science & Engineering Korea University5-1 Anam-dongSeongbuk-kuSeoul 136-713Republic of Korea Div.of Materials and Manufacturing Science Osaka University2-1 YamadaokaSuitaOsaka 565-0871Japan Research Center for Ultra High Voltage Electron Microscopy Osaka University7-1 MihogaokaIbarakiOsaka 567-0047Japan

The wetting behavior of Au and Ag particles on a monocrystalline graphite substrate was investigated using the microscopic sessile drop method under a purified Ar atmosphere at 1300 K. The measured contact angles of the liquid Au and Ag on monocrystalline graphite substrates of （0001） face were 129° and 124°, respectively. It is believed that the interaction at the interface is dominated by the physical bonding （van der Waal＇s interaction）.

关键词： graphite microscopic sessile drop method surface structure wetting

Machine learning super-resolution of laboratory CT images in all-solid-state batteries using synchrotron radiation CT as training data

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Energy and AI 2023年第4期14卷 612-619页

作者： M.Kodama A.Takeuchi M.Uesugi S.hirai Tokyo Institute of Technology 2-12-1 OokayamaMeguro-kuTokyo 152-8550Japan Japan Synchrotron Radiation Research Institute(JASRI/SPring-8) 1-1-1 KoutoSayoHyogo 679-5198Japan

High-performance all-solid-state lithium-ion batteries require observation,control,and optimization of the electrode structure.X-ray computational tomography(CT)is an effective nondestructive method for observing the electrode structure in three ***,the limited availability of synchrotron radiation CT,which offers high-resolution imaging with a high signal-to-noise ratio,makes it difficult to conduct experiments and restricts the use of X-ray CT in battery ***,laboratory CT systems are widely available,but they use X-rays emitted from a metal target,resulting in lower image quality and resolution compared with synchrotron radiation *** study explores a method for achieving comparable resolution in laboratory CT images of all-solid-state batteries to that of synchrotron radiation *** method involves using the synchrotron radiation CT images as training data for machine learning *** results demonstrate that,by employing an appropriate machine learning algorithm and activation function,along with a sufficiently deep network,the image quality of laboratory CT becomes equivalent to that of synchrotron radiation CT.

关键词： All-solid-state lithium-ion battery X-ray CT Laboratory CT Synchrotron radiation CT Super-resolution Machine learning