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Formation of ceramic-metal composite layers on die steels by electron beam irradiation

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材料与冶金学报 2015年第2期14卷 152-158页

作者： Takahiro Akao Yuki Sakurai tetsuhiko onda Kazutake Uehara Zhongchun Chen Department of Mechanical and Aerospace Engineering Graduate School of EngineeringTottori University Koyama - minami d - 101 Tottori 680 - 8552 Japan Next Generation Advanced Medical Promotion Center Tottori University Hospital Nishi - cho 36 - 1 Yonago Tottori 683 - 8504 Japan

Surface modifications,which result in formation of a hard layer such as CrN,TiN,TiCN etc. on tool surfaces,have been widely utilized in machining tools. How ever,the hard layer has clear interface with the matrix,thereby the delamination between the hard layer and matrix often occurs because of a mismatch of the thermal expansion coefficients. A composite layer with complicated interfaces between hard material and matrix is desired to avoid such a delamination due to a complicated interface existed between workpiece and coating materials. In this study,the formation of ceramic- metal composite layers on the surfaces of die steels by an electron beam( EB) irradiation technique has been investigated. When WC- Co powder was embrocated onto the substrate surfaces,a composite layer of WC- Co and matrix was formed through solidification after the irradiation-induced melting. The composite layer shows a marble- like texture with WC- rich regions. The hardness of the layer reaches up to 1000 HV. For other ceramic pow ders such as TiN and SiC,only small amount of particles has been incorporated into the composite layer,resulting in a relatively low hardness enhancement after the EB irradiation.

关键词： surface modification die steel composite layer electron beam irradiation

Functionally graded Al_2O_3-ZrO_2 composite prepared by centrifugal slip casting and its mechanical properties

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材料与冶金学报 2006年第4期5卷 296-299页

作者： HAYAKAWA Motozo HARA Yasuyuki LI Xiao-dong onda tetsuhiko Department of Mechanical Engineering Tottofi University Koyama Tottofi 680 - 8552 Japan Graduate student Tottofi University Koyama Tottofi 680 -8552 Japan The Key Laboratory for Anisotropy and Texture of Materials （Ministry of Education） Northeastern University Shenyang 110004 China

Compositionally graded composite of alumina-20%zirconia (volume fraction) was fabricated by using centrifugal casting incorporated with relatively thin slip. An EPMA analysis exhibited a nearly linear variation of the alumina/zirconia ratio along the centrifugal direction; zirconia tended to accumulate in the bottom section, while alumina in the top section. Such a graded structure exhibited a considerably higher flexural strength when the alumina rich surface was subjected to a tensile stress than compositionally uniform composite of the same average composition. Fracture toughness measurement across the specimen thickness by indentation method revealed that the crack lengths along the vertical and horizontal directions were different. The anisotropy of the fracture toughness was accounted for by the variation of the residual stress across the specimen thickness.

关键词： Al2O3-ZrO2 复合材料离心滑动铸件弯曲强度

Synthesis and characterization of alumina-matrix oxide/oxide composites

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材料与冶金学报 2010年第4期9卷 290-295页

作者： Makoto EZUMI Daisuke NOMOTO Takahiro AKAO tetsuhiko onda Zhong-Chun CHEN Department of Mechanical and Aerespace Engineering Graduate School of Engineering Tottori University Koyama - minami 4 - 101 Tottori 680 - 8552 Japan

Al2O3 matrix oxide/oxide composites containing rod-like Ba-β-Al2O3 and equiaxed ZrO2 particles have been successfully synthesized by an in-situ process from a mixture of Al2O3 and BaZrO3 powders. The long-axis direction of rod-like Ba-β-Al2O3 phase is parallel to [1010], while the longitudinal interface between Ba-β-Al2O3 phase and Al2O3 matrix is parallel to (0001) of the Ba-β-Al2O3 phase. The mechanical properties of the composites, such as Vickers hardness and fracture toughness, are enhanced with increasing the sintering temperature. Furthermore, the presence of rod-like Ba-β-Al2O3 particles results in enhancement of fracture toughness of the in-situ synthesized composites due to crack deflection and crack bridging.

关键词： ceramic matrix composite oxide/oxide composite in-situ synthesis Al2O3 Ba-β-Al2O3

Isothermal and athermal martensitic transformations of ceria cerla doped zilrconian

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材料与冶金学报 2010年第3期9卷 211-216页

作者：音田哲彦原纯平陈中春早川元造日本鸟取大学 Graduate Student of Mechanical and Aerospace Engineering Tottori University Sumitomo Electric Sintered Alloy Ltd.

Martensitic transformation behavior was studied for zirconia containing 4%～10% CeO2 (in mole fraction) by using a dilatometric method. The Ms (Martensite start temperature) decreased near linearly with increasing CeO2. Different transformation modes were observed depending on the composition and cooling rate. ZrO2 containing 6% CeO2 showed isothermal transformation behavior, whereas ZrO2 containing 9% and 10% CeO2 showed athermal transformation behavior. However, ZrO2 containing 8% CeO2 showed either isothermal or athermal transformations behavior depending on the cooling rate. A TTT (Time-Temperature-Transformation) diagram was proposed for ZrO2 containing 8% CeO2.

关键词： martensitic transformation ceria doped zirconia isothermal transformation athermal transformation thermally activated process burst type transformation

Tumor size discrepancy between endoscopic and pathological evaluations in colorectal endoscopic submucosal dissection

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World Journal of Gastrointestinal Endoscopy 2024年第3期16卷 136-147页

作者： Takeshi onda Osamu Goto Toshiaki Otsuka Yoshiaki Hayasaka Shun Nakagome Tsugumi Habu Yumiko Ishikawa Kumiko Kirita Eriko Koizumi Hiroto Noda Kazutoshi Higuchi Jun Omori Naohiko Akimoto Katsuhiko Iwakiri Department of Gastroenterology Nippon Medical SchoolGraduate School of MedicineBunkyo-ku 113-8603TokyoJapan Endoscopy Center Nippon Medical School HospitalBunkyo-ku 113-8603TokyoJapan Department of Hygiene and Public Health Nippon Medical SchoolBunkyoku 113-8603TokyoJapan Center for Medical Education Nippon Medical SchoolBunkyo-ku 113-8603TokyoJapan

BACKGROUND Tumor size impacts the technical difficulty and histological curability of colorectal endoscopic submucosal dissection(ESD);however,the preoperative evaluation of tumor size is often different from histological *** influential factors on failure to obtain an accurate tumor size evaluation could help prepare optimal conditions for safer and more reliable *** This was a retrospective study conducted at a single institution.A total of 377 lesions removed by colorectal ESD at our hospital between April 2018 and March 2022 were *** first assessed the difference in size with an absolute per-centage of the scaling ***,we compared the clinicopatho-logical characteristics of the correct scaling group(>-33%and33%),which was further subdivided into the underscaling group(-33%or less of the discrepancy)and overscaling group(33%or more of the discrepancy),*** secondary outcome measures,parameters on size estimation were compared between the underscaling and correct scaling groups,as well as between the overscaling and correct scaling ***,multivariate analysis was performed in terms of the following relevant parameters on size estimation:Pathological size,location,and possible influential factors(P<0.1)in the univariate *** The mean of absolute percentage in the scaling discordance was 21%,and 91 lesions were considered to be incorrectly estimated in *** incorrect scaling was significantly remarkable in larger lesions(40 mm vs 28 mm;P<0.001)and less experience(P<0.001),and these two factors were influential on the underscaling(75 lesions;P<0.001).Conversely,compared with the correct scaling group,16 lesions in the overscaling group were significantly small(20 mm vs 28 mm;P<0.001),and the small lesion size was influential on the overscaling(P=0.002).CONCLUSION Lesions indicated for colorectal ESD tended to be underestimate

关键词： Endoscopic submucosal dissection Colorectal tumor Tumor size Size estimation Size discrepancy

Combining post-disturbance land cover and tree canopy cover from Landsat time series data for mapping deforestation,forest degradation,and recovery across Cambodia

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International Journal of Digital Earth 2022年第1期15卷 832-852页

作者： Katsuto Shimizu Tetsuji Ota Nariaki onda Nobuya Mizoue Department of Forest Management Forestry and Forest Products Research InstituteIbarakiJapan Faculty of Agriculture Kyushu UniversityFukuokaJapan Tohoku Research Center Forestry and Forest Products Research InstituteIwateJapan

Mapping of deforestation,forest degradation,and recovery is essential to characterize country-level forest change and formulate mitigation *** studies have mainly used a simple forest/non-forest classification after forest disturbance to identify deforestation and forest ***,a more flexible approach that is applicable to different forest conditions is *** this study,we examined an approach for mapping deforestation,forest degradation,and recovery using disturbance types and tree canopy cover estimates from annual Landsat time-series data from 1988 to 2020 across *** developed models to estimate both disturbance types and tree canopy cover based on a random forest algorithm using predictor variables derived from a trajectory-based temporal segmentation *** estimated disturbance types and canopy cover in each year were then used in a rule-based classification of deforestation,forest degradation,and *** producer’s and user’s accuracies ranged from 59.1%to 72.9%and 60.8%to 91.6%,respectively,for the forest change classes of mapping deforestation,forest degradation,and *** approach developed here can be adjusted for different definitions of deforestation,forest degradation,and recovery according to research objectives and thus has the potential to be applied to other study areas.

关键词： Deforestation degradation time series Google Earth Engine tropical forest

A tree detection method based on trunk point cloud section in dense plantation forest using drone Li DAR data

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Forest Ecosystems 2023年第1期10卷 37-45页

作者： Yupan Zhang Yiliu Tan Yuichi onda Asahi Hashimoto Takashi Gomi Chenwei Chiu Shodai Inokoshi Center for Research in Isotopes and Environmental Dynamics University of Tsukuba1-1-1TennodaiTsukubaIbaraki305-8572Japan Graduate School of Systems and Information Engineering University of Tsukuba1-1-1TennodaiTsukubaIbaraki305-8572Japan Department of International Environmental and Agricultural Science Tokyo University of Agriculture and Technology3-5-8SaiwaieFuchuTokyo183-8509Japan

Single-tree detection is one of the main research topics in quantifying the structural properties of forests. Drone Li DAR systems and terrestrial laser scanning systems produce high-density point clouds that offer great promise for forest inventories in limited areas. However, most studies have focused on the upper canopy layer and neglected the lower forest structure. This paper describes an innovative tree detection method using drone Li DAR data from a new perspective of the under-canopy structure. This method relies on trunk point clouds, with undercanopy sections split into heights ranging from 1 to 7 m, which were processed and compared, to determine a suitable height threshold to detect trees. The method was tested in a dense cedar plantation forest in the Aichi Prefecture, Japan, which has a stem density of 1140 stems·ha^(-1) and an average tree age of 42 years. Dense point cloud data were generated from the drone Li DAR system and terrestrial laser scanning with an average point density of 5000 and 6500 points·m^(-2), respectively. Tree detection was achieved by drawing point-cloud section projections of tree trunks at different heights and calculating the center coordinates. The results show that this trunk-section-based method significantly reduces the difficulty of tree detection in dense plantation forests with high accuracy(F1-Score=0.9395). This method can be extended to different forest scenarios or conditions by changing section parameters.

关键词： Tree detection Trunk sections Forest Drone LiDAR

Hydrological setting of infertile species-rich wetland——a case study in the warm temperate Japan

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Journal of Environmental Sciences 2003年第2期15卷 279-283页

作者： Kikuchi A. Nakagoshi N. onda Y. Graduate School for International Development and Cooperation Hiroshima UniversityGraduate School for International Development and Cooperation Hiroshima UniversityInstitute of Geoscience University of Tsukuba Higashi-Hiroshima City 739_8529 JapanHigashi-Hiroshima City 739_8529 JapanIbaraki 305_8571 Japan

The detailed groundwater flow and water chemistry to illustrate landscape structure of the infertile peatless mire by using piezometers and groundwater wells were measured. The instruments were installed in lines through a small spring-fed wetland underlying little peat from the hillslope to the valley bottom in southwestern Japan. Flow net and EC data clearly indicated that the wetland was situated in a high-EC groundwater upspring area. The low-productivity graminous vegetation was related with four hydrological factors such as: (1) high water level; (2) low-EC(<25 micro S/cm) groundwater; (3) weakly upward hydraulic gradient; and (4) overflowing of negatively pressured groundwater. In other words, the “old or deep groundwater” constructed the foundation of slope-wetland, and maintained the high groundwater level. In contrast, overflowing “youthful groundwater” is supplied from head of slope-wetland preferentially through the shallow substratum. The plant communities of the peatless mire in southwestern Japan are similar to those of raised bog in northern cool temperate Japan. There have been some reports verifying that the underlying mineral substrata of such wetlands were quartzile rocks such as granite, rhyolite, chart and well-leached sand. Results showed (1) low cation availability affects the water acidity; (2) upward seepage of high-EC groundwater composed the foundation of the investigated peatless mire; and (3) the poor mineral condition seems to play a similar role to northern ombrotrophic(rain-fed) condition.

关键词： eco-hydrology electrical conductivity groundwater flow plant community wetland

Hyperpolarization caused by serotonin contributes to endothelium-dependent relaxations in the porcine coronary artery

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中国药理学报 1999年第12期20卷 1093-1096页

作者： Seung-Jung PARK Mikio NAKASHIMA tetsuhiko NAGAO Paul M VANHOUTTE Center for Experimental Therapeutics Department of MedicineBaylor College of MedicineOne Baylor PlazaHoustonTX 77030USA

AIM:The present study was designed to investigate the contribution of membrane hyperpolarization to endothelium-dependent relaxations induced by serotonin in the porcine coronary ***:Rings with and without endothelium of porcine coronary arteries were suspended in conventional organ chambers for the measurement of isometric *** cell membrane potential of the vascular smooth muscle cells was measured using glass microelectrodes,in the presence of indometacin,ketanserin,and/or N^(ω)-***:Serotonin induced a transient endothelium-,and concentration-dependent relaxation in rings contracted with prostaglandin F_(2α)in the presence of N^(ω)-nitro-L-arginine(maximal relaxation;19%).The N^(ω)-nitro-L-arginine resistant relaxation was abolished by high K^(+)and tetrabutylammonium *** also caused an endothelium-,concentration-dependent membrane hyperpolarizations with a maximal amplitude *** nitro-L-arginine resistant relaxations and hyperpolarizations were abolished by methiothepin,but not by *** time course of the endothelium-dependent relaxations and hyperpolarizations was ***:These results suggest a contribution of cell membrane hyperpolarization to theendothelium-dependent relaxations induced by serotonin in the porcine coronary artery.

关键词： indomethacin ketanserin membrane potentials methiothepin nitric oxide potassium channels serotonin vascular endothelium