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排序方式: 共有640条查询结果,搜索用时 15 毫秒
51.
Chinatsu Yonezawa Masahiro Negishi Kenta Azuma Manabu Watanabe Naoki Ishitsuka Shigeo Ogawa 《International journal of remote sensing》2013,34(18):5696-5711
Spaceborne synthetic aperture radar (SAR) can be used for agricultural monitoring. In this study, three single-polarimetric and four full-polarimetric observation data sets were analysed. A rice paddy field in northern Japan was used as the study site; the data for this site were obtained using RADARSAT-2, which carries a full-polarimetric C-band SAR. Soybean and grass fields were also present within the paddy fields. The temporal change in the backscattering coefficient of the rice paddy fields for the single-polarization data agreed with the temporal change obtained for a rice growth model based on radiative transfer theory. A three-component decomposition approach was applied to the full-polarimetric data. With each rice growth stage, the volume scattering component ratio increased, whereas the surface scattering component ratio generally decreased. The soybean and grass fields showed a smaller double-bounce scattering component than the rice fields for all the acquired data. The results of this study show that multitemporal observation by full-polarimetric SAR has great potential to be utilized for estimating rice-planted areas and monitoring rice growth. 相似文献
52.
Hagiwara M Takahashi S Hoshina T Takeda H Tsurumi T 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2011,58(9):1721-1729
The electric transient response method is an effective technique to evaluate material constants of piezoelectric ceramics under high-power driving. In this study, we tried to incorporate nonlinear piezoelectric behaviors in the analysis of transient responses. As a base for handling the nonlinear piezoelectric responses, we proposed an assumption that the electric displacement is proportional to the strain without phase lag, which could be described by a real and constant piezoelectric e-coefficient. Piezoelectric constitutive equations including nonlinear responses were proposed to calculate transient responses of a piezoelectric resonator. The envelopes and waveforms of current and vibration velocity in transient responses observed in some piezoelectric ceramics could be fitted with the calculation including nonlinear responses. The procedure for calculation of mechanical quality factor Q(m) for piezoelectric resonators with nonlinear behaviors was also proposed. 相似文献
53.
Hidetsugu Nanba Natsumi Anzen Manabu Okumura 《International Journal on Digital Libraries》2008,9(2):151-161
The need for academic researchers to retrieve patents and research papers is increasing, because applying for patents is now
considered an important research activity. However, retrieving patents using keywords is a laborious task for researchers,
because the terms used in patents for the purpose of enlarging the scope of the claims are generally more abstract than those
used in research papers. Therefore, we have constructed a framework that facilitates patent retrieval for researchers, and
have integrated research papers and patents by analysing the citation relationships between them. We obtained cited research
papers in patents using two steps: (1) detection of sentences containing bibliographic information, and (2) extraction of
bibliographic information from those sentences. To investigate the effectiveness of our method, we conducted two experiments.
In the experiment involving Step 1, we prepared 42,073 sentences, among which a human subject manually identified 1,476 sentences
containing citations of papers. For Step 2, we prepared 3,000 sentences, in which the titles, authors, and other bibliographic
information were manually identified. We obtained a precision of 91.6%, and a recall of 86.9% in Step 1, and a precision of
86.2% and a recall of 85.1% in Step 2. Finally, we constructed an information retrieval system that provided two methods of
retrieving research papers and patents. One method was retrieval by query, and another was from the citation relationships
between research papers and patents. 相似文献
54.
Manabu Tanaka 《Journal of Materials Science》1996,31(13):3513-3521
The effects of grain boundary configuration and creep conditions on the fractal dimension of the grain boundary fracture (D
f) were investigated using commercial cobalt-based heat resistant alloys, namely, HS-21 and L-605 alloys. Creep-rupture experiments were carried out under the initial creep stresses of 19.6–176 MPa in the temperature range from 1089–1422 K in air. The value of D
f was larger in specimens with serrated grain boundaries than in those with straight grain boundaries in the HS-21 alloy under the same creep condition, and the difference in the value of D
f between these specimens was large in the scale range of the analysis which was less than about one grain boundary length. However, there was almost no difference in the value of D
f between the specimens with serrated grain boundaries and those with straight grain boundaries in the L-605 alloy, because there was no obvious difference in the microstructure between these specimens. The value of D
f increased with decreasing creep stress in the scale range of the fractal analysis larger than about one grain boundary length in both HS-21 and L-605 alloys, while the stress dependence of D
f was larger in the HS-21 alloy. The stress dependence of D
f was explained by the stress dependence on the number of grain boundary microcracks linked to the fracture surface. The value of D
f estimated in the scale range smaller than about one grain boundary length showed essentially no stress dependence in both L-605 and HS-21 alloys. 相似文献
55.
Chang-eun Kim Ken Kurosaki Manabu Ishimaru Hiroaki Muta Shinsuke Yamanaka 《Journal of Electronic Materials》2011,40(5):999-1004
Our group has focused attention on Ga2Te3 as a natural nanostructured thermoelectric material. Ga2Te3 has basically a zincblende structure, but one-third of the Ga sites are structural vacancies due to the valence mismatch
between Ga and Te. It has been confirmed that (1) vacancies in Ga2Te3 exist as two-dimensional (2D) vacancy planes, and (2) Ga2Te3 exhibits an unexpectedly low thermal conductivity (κ), most likely due to highly effective phonon scattering by the 2D vacancy planes. However, the effect of the size and periodicity
of the 2D vacancy planes on κ has been unclear. In addition, it has also been unclear whether only the 2D vacancy planes reduce κ or if point-type vacancies can also reduce κ. In the present study, we tried to prepare Ga2Te3 and Ga2Se3 with various vacancy distributions by controlling annealing conditions. The atomic structures of the samples were characterized
by means of transmission electron microscopy, and κ was evaluated from the thermal diffusivity measured by the laser flash method. The effects of vacancy distributions on κ of Ga2Te3 and Ga2Se3 are discussed. 相似文献
56.
Kenichi Noguchi Yukihisa Matsuda Manabu Oishi Takaki Masaki Sadao Nakayama Masahiro Mizushina 《Journal of the American Ceramic Society》1990,73(9):2667-2676
Tensile strength of Y2 O3 -stabilized ZrO2 polycrystals (Y-TZP) was measured by a newly developed tensile testing method with a rectangular bar. The tensile strength of Y-TZP was lower than that of the three-point bend strength, and the shape of the tensile strength distribution was quite different from that of the three-point bend strength distribution. It was difficult to predict the distribution curve of the tensile strength using the data of the three-point bend strength by one-modal Weibull distribution. The distribution of the tensile strength was analyzed by two- or three-model Weibull distribution coupled with an analysis of fracture origins. The distribution curve of the three-point bend strength which was estimated by multimodal Weibull distribution agreed favorably with that of the measured three-point bend strength values. A two-modal Weibull distribution function was formulated approximately from the distributions of the tensile and three-point bend strengths, and the estimated two-modal Weibull distribution function for the four-point bend strength agreed well with the measured four-point bend strength. 相似文献
57.
Hiroyuki Fujishiro Manabu Ikebe Masayuki Yagi Kiminari Nakasato Yuzo Shibazaki Tetsuo Fukase 《Journal of Low Temperature Physics》1996,105(3-4):981-986
The thermal conductivity of high density La2–xMxCuO4 (M=Ba, Sr) sintered materials was measured between 15K and 150K for the various concentrations of Ba and the phonon thermal conductivity was analyzed comparing with that of Nd2–xCexCuO4. The pretty large value for pure La2CuO4 was drastically diminished by substituting La by a small amount of Ba atoms especially at low temperatures. It was found that a new type of the phonon scattering center such as a two-level tunneling must be taken account of in order to explain the observed reduction. 相似文献
58.
Keiji Ogi Tomonaga Okabe Manabu Takahashi Shigeki Yashiro Akinori Yoshimura Toshio Ogasawara 《Composites Part A》2010,41(4):489-498
This paper discusses high-speed impact damage in a three-dimensionally woven SiC/SiC composite (3D-CMC). The impact damage was introduced by a steel ball projectile in 3D-CMC plates with and without thermal exposure. The surface and internal damages were observed by optical microscopy and X-ray CT. A crater was observed on the collision surface. The X-ray CT measurement revealed that multiple pyramid-shaped cone cracks were generated beneath the crater when the impact speed was relatively low. At an impact speed exceeding the critical speed, a spall fragment was ejected from the back surface, while no internal damage was observed in the fragment. The spall fracture mode differed between the virgin and the thermally-exposed specimens. This difference is the result of embrittlement of the fiber/matrix interface due to oxidation of the carbon coating layer in the thermally-exposed specimen. In addition, it is found that z-yarns improve impact resistance by constraining delamination. 相似文献
59.
Tado Kanzaki Manabu Bannai Kenzo Kitayama 《Journal of the American Ceramic Society》1999,82(7):1925-1927
When manganese-bearing ferrites (Mn x Fe3- x O4-delta , with x = 0.17-1.09) were prepared in the present study via a solid-state reaction, manganese ions were incorporated into the lattice sites of the ferrites in the divalent state. The lattice constant ( a 0 ) of those ferrites increased linearly as the manganese composition x increased. A ferrite with x = 1.28 contained manganese ions with a valence state higher than 3+; however, no further increase in a 0 occurred at valences higher than 2+. 相似文献
60.
Effect of Cation Doping on the Superplastic Flow in Yttria-Stabilized Tetragonal Zirconia Polycrystals 总被引:1,自引:0,他引:1
Junpei Mimurada Manabu Nakano Kazutaka Sasaki Yuichi Ikuhara Taketo Sakuma 《Journal of the American Ceramic Society》2001,84(8):1817-1821
The superplastic characteristics of various cation-doped yttria-stabilized tetragonal zirconia polycrystals (Y-TZP) were examined. For 1 mol% cation doping the true stress of Y-TZP is very dependent on the ionic radii of the doped cations; for instance, smaller cation radii give rise to lower true stress when compared with the other compositions for the same grain size, strain rate, and testing temperature. The altered true stress level must be due to the change in diffusivity of the accommodation process for grain boundary sliding caused by the addition of cations in ZrO2 . The strain to failure of the doped zirconia is affected by both ionic radius and valence of the dopant cations. 相似文献