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排序方式: 共有1497条查询结果,搜索用时 31 毫秒
1.
Ichiro Fujii Saki Nakashima Takahiro Wada 《Journal of the American Ceramic Society》2019,102(3):1240-1248
0.24Pb(In1/2Nb1/2)O3-0.42Pb(Mg1/3Nb2/3)O3-0.34PbTiO3 transparent ceramics were fabricated by a conventional sintering technique. Through optimization of sintering conditions of calcination and sintering temperatures and time, the obtained ceramics showed high optical transmittance of 53% and 71% at light wavelengths of 1300 and 2000 nm, respectively. The ceramics showed a rhombohedral to tetragonal phase transition at ~120°C and a tetragonal to cubic phase transition at 222°C. These transition temperatures were higher than those of 0.67Pb(Mg1/3Nb2/3)-0.33PbTiO3 ceramics. In addition, the ceramics had a ferroelectric hysteresis loop, a large piezoelectric constant d33 of 407 pC/N, and a planar electromechanical coupling factor kp of 52%. These results suggest that the transparent ceramics may be used as a temperature-stable, linear electro-optic material. 相似文献
2.
Tatsuya Funai Megumi Aotani Risa Kiriu Junko Nakamura Yuki Miyazaki Dr. Osamu Nakagawa Dr. Shun-ichi Wada Prof. Dr. Hidetaka Torigoe Prof. Dr. Akira Ono Prof. Dr. Hidehito Urata 《Chembiochem : a European journal of chemical biology》2020,21(4):517-522
Spectroscopic characterization of AgI-ion-mediated C-AgI-A and C-AgI-T base pairs found in primer extension reactions catalyzed by DNA polymerases was conducted. UV melting experiments revealed that C-A and C-T mismatched base pairs in oligodeoxynucleotide duplexes are specifically stabilized by AgI ions in 1:1 stoichiometry in the same manner as a C-C mismatched base pair. Although the stability of the mismatched base pairs in the absence of AgI ions is in the order C-A≈C-T>C-C, the stabilizing effect of AgI ions follows the order C-C>C-A≈C-T. However, the comparative susceptibility of dNTPs to AgI-mediated enzymatic incorporation into the site opposite templating C is dATP>dTTP≫dCTP, as reported. The net charge, as well as the size and/or shape complementarity of the metal-mediated base pairs, or the stabilities of mismatched base pairs in the absence of metal ions, would be more important than the stability of the metallo-base pairs in the replicating reaction catalyzed by DNA polymerases. 相似文献
3.
Tsuneaki Matsudaira Masashi Wada Naoki Kawashima Miyuki Takeuchi Daisaku Yokoe Takeharu Kato Masasuke Takata Satoshi Kitaoka 《Journal of the European Ceramic Society》2021,41(5):3150-3160
Mass transfer in polycrystalline Yb2SiO5 wafers with precise composition control was evaluated and analyzed by oxygen permeation experiments at high temperatures using an oxygen tracer. Oxygen permeation proceeded due to mutual grain boundary diffusion of oxide ions and Yb ions without synergistic effects such as acceleration or suppression. The oxygen shielding properties of Yb2SiO5 were compared with those of the other line compounds such as Yb2Si2O7 and Al2O3 based on the determined mass transfer parameters. It was found that the more preferentially an oxide ion diffuses in the grain boundary compared to the interior of the grain, the greater the effect of suppressing the movement of the oxide ion by applying an oxygen potential gradient becomes. 相似文献
4.
Ichiro Fujii Shin Ariizumi Shintaro Ueno Chikako Moriyoshi Yoshihiro Kuroiwa Satoshi Wada 《Ceramics International》2018,44(9):10657-10662
We fabricated xBaTiO3 (BT)/(1-x)[BaTiO3-Bi(Mg1/2Ti1/2)O3-BiFeO3] (BT-BMT-BF)?+?0.1?wt%MnCO3 composites by spark plasma sintering and investigated the effect of BT content x, BT powder size, and BT-BMT-BF composition on piezoelectric properties. For xBT/(1-x)(0.3BT-0.1BMT-0.6BF) +?0.1?wt%MnCO3 (x?=?0–0.75) composites with a 0.5-µm BT powder, the dielectric constant was increased with x, and the relative density was decreased at x?=?0.67 and 0.75, creating optimum BT content of x?=?0.50 with a piezoelectric constant d33 of 107?pC/N. When a larger 1.5-µm BT powder was utilized for the composite with x?=?0.50, the d33 value increased to 150?pC/N due to the grain size effect of the BT grains. To compensate for a compositional change from the optimum 0.3BT-0.1BMT-0.6BF due to partial diffusion between the BT and 0.3BT-0.1BMT-0.6BF grains, a 0.5BT/0.5(0.275BT-0.1BMT-0.625BF)?+?0.1?wt%MnCO3 composite with the 1.5-µm BT powder was fabricated. We obtained an increased d33 value of 166?pC/N. These results provided a useful composite design to enhance the piezoelectric properties. 相似文献
5.
Kanji Wada 《Tunnelling and Underground Space Technology incorporating Trenchless Technology Research》1986,1(3-4):315-322
Kanmon Highway Tunnel is a 3.5-km-long undersea road tunnel linking Honshu Mainland and Kyushu Island under the Kanmon Straits. Carrying a traffic volume of approx. 25 000 cars per day, the tunnel plays an important role as a main trunk road (National Highway Route 2). On the other hand, poor environmental conditions of the undersea section during the tunnel's 28 yr of service, and the increasing number of large-size vehicles have caused deterioration of the tunnel structures and facilities. Japan Highway Public Corporation, which is in charge of operation of the tunnel, is considering establishing a future plan of tunnel maintenance and reform, and is now examining such a plan. This paper outlines, first, the daily maintenance and control issues such as organization, inspections, maintenance works, operation of facilities, and expenses for maintenance and control of the tunnel. The repair and renovation works already completed and to be executed in the near future are then discussed. The paper also examines environmental problems such as noise and polluted air around ventilation shafts. 相似文献
6.
The behaviour of microbial populations responsible for degradation of the aromatic compounds, phenol, benzoate, and salicylate, and changes of microbial community structures in seawater microcosms were analysed quantitatively and qualitatively using MPN–PCR and PCR–DGGE. The purpose of the study was to investigate the ecology of the entire microbial community during bioremediation. Bacterial populations possessing catechol 1,2-dioxygenase (C12O) DNA were evidently the primary degraders of phenol and benzoate, but others possessing catechol 2,3-dioxygenase (C23O) DNA increased to enhance substrate degradation under high-load conditions when the substrates were present for long periods. However, salicylate degradation was evidently facilitated by specific bacterial populations possessing C23O DNA. PCR–DGGE analyses suggested that bacterial populations already relatively dominant in the original microcosm contributed to phenol degradation. Bacteria composing a minor fraction of the original population apparently increased and contributed to benzoate degradation. Bacterial populations possessing C23O DNA were responsible for salicylate degradation, however, and different degrading bacteria were evidently selected for, depending on the initial salicylate concentration. Microbial community structure tended to be simplified by aromatic compound degradation. Thus, microbial monitoring can elucidate the behaviour of bacterial populations responsible for aromatic compound degradation and be used to assess the effects of bioremediation on intact microbial ecosystems. 相似文献
7.
8.
Kyohei Ueda Kaito Sawada Toma Wada Tetsuo Tobita Susumu Iai 《Soils and Foundations》2019,59(5):1260-1279
The generalized scaling law is based on the concept of two-stage scaling and allows currently available centrifuge facilities to model a large-scale prototype expanding over the spatial dimension ranging from 30 m or larger subject to earthquake motions. This paper presents the results of investigation on the applicability of the generalized scaling law to the fully nonlinear regime of soil-structure system with the induced strain level of 10% in the order of magnitude. The centrifuge model tests performed in this study under the modeling of models scheme consist of a pile model embedded in a inclined ground subject to liquefaction-induced lateral spreading. Four different centrifugal accelerations ranging from 13g to 50g are used whereas the actual size of the physical model is kept constant with an overall scaling factor of 1/100. The models are exposed to tapered sinusoidal input accelerations of frequency 0.59 Hz and amplitude 3.0 m/s2 in prototype scale, and the results are compared in terms of prototype by applying the generalized scaling law. As for the response of the ground during shaking, essentially identical accelerations and excess pore water pressures are recorded for all cases, while the lateral displacement shows a variation ranging from 5% to 9% in terms of shear strain due to a slight variation in experimental conditions (e.g., input peak acceleration, achieved density distribution). Practically the same responses are measured among the cases in the dissipation phase of excess pore water pressure. With regard to pile behavior, nearly identical responses for the lateral displacements and bending moments are obtained for all cases both during and after shaking. These results demonstrated that the generalized scaling law is applicable to the fully nonlinear regime of soil-structure system subject to the cumulative shear strain in the order of 10% due to cyclic mobility of sands during earthquakes. 相似文献
9.
Takafumi Ishii Takuya Maie Naofumi Kimura Yuki Kobori Yasuo Imashiro Jun-ichi Ozaki 《International Journal of Hydrogen Energy》2017,42(23):15489-15496
The use of carbon cathode catalysts in polymer electrolyte fuel cells instead of the current platinum catalysts is attracting increasing attention. We claim that two factors are important for enhancing the activity of carbon cathode catalysts in the oxygen reduction reaction (ORR): the formation of a nanoshell structure and co-doping with boron and nitrogen. Herein, we investigate the preparation and characterization of active ORR carbon catalysts that combine the above factors. Boron and nitrogen (BN)-doped nanoshell-containing carbon (BN-NSCC) was prepared by carbonizing a mixture of poly(furfuryl alcohol), cobalt phthalocyanine, melamine, and a trifluoroborane–methanol complex at 1000 °C. Transmission electron microscopy and X-ray photoelectron spectroscopy revealed the formation of nanoshell structures with distorted graphitic layers and the introduction of boron and nitrogen atoms, respectively. The ORR activity was evaluated in oxygen-saturated 0.5 mol dm?3 H2SO4 using Koutecky–Levich analysis. The BN-NSCC showed an eight to ten times higher ORR activity than undoped NSCC, with an increased number of electrons participating in the reaction. Tafel analysis revealed a change in the rate-determining step caused by BN-doping. Thus, the combination of a nanoshell structure and co-doping with boron and nitrogen was found to improve the ORR activity of carbon catalysts. 相似文献
10.
Kazushige Ishida Yoichi Wada Masahiko Tachibana Nobuyuki Ota Motohiro Aizawa 《Journal of Nuclear Science and Technology》2013,50(11):1071-1082
The effects of water chemistry distribution on the potential of a reference electrode and of the potential distribution on the measured potential should be known qualitatively to obtain accurate electrochemical corrosion potential (ECP) data in BWRs. First, the effects of oxygen on a platinum reference electrode were studied in 553 K pure water containing dissolved hydrogen (DH) concentration of 26–105 μg kg?1 (ppb). The platinum electrode worked in the same way as the theoretical hydrogen electrode under the condition that the molar ratio of DH to dissolved oxygen (DO) was more than 10 and that DO was less than 100 ppb. Second, the effects of potential distribution on the measured potential were studied by using the ECP measurement part without platinum deposition on the surfaces connected to another ECP measurement part with platinum deposition on the surfaces in 553 K pure water containing 100–130 ppb of DH or 100–130 ppb of DH plus 400 ppb of hydrogen peroxide. Measured potentials for each ECP measurement part were in good agreement with literature data for each surface condition. The lead wire connecting point did not affect the measured potential. Potential should be measured at the nearest point from the reference electrode in which case it will be not affected by either the potential distribution or the connection point of the lead wire in pure water. 相似文献