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排序方式: 共有233条查询结果,搜索用时 31 毫秒
71.
Fabrication of Silicon Carbide Whisker/Alumina Composite by Thermal-Gradient Chemical Vapor Infiltration 总被引:1,自引:0,他引:1
Teruoki Tago Motoaki Kawase Kenshi Morita Kenji Hashimoto 《Journal of the American Ceramic Society》1999,82(12):3393-3400
SiC( w )/Al2 O3 composites were made from an AlCl3 -H2 -CO2 mixture by a thermal-gradient chemical vapor infiltration (CVI) method. Al2 O3 was deposited from the reaction of AlCl3 and H2 O, which was produced from the oxidation of H2 by CO2 . The densification rate was measured at various reactant compositions and total pressures. When the reaction rate or total pressure increased, the rate-controling step shifted from H2 O production to AlCl3 diffusion, which led to premature pore closing. To obtain dense composites in a short infiltration time, the diffusion rate of AlCl3 had to be increased by decreasing the total pressure. 相似文献
72.
Kadota Y. Ishikawa M. Hosaka H. Morita T. 《IEEE transactions on ultrasonics, ferroelectrics, and frequency control》2009,56(1):9-13
Ultrasonically assisted hydrothermal synthesis of PZT thin films was performed using an ultrasonic transducer integrated into the lid of an autoclave. Direct ultrasonic irradiation of 23 W at 53 kHz was carried out during the hydrothermal synthesis at a reaction temperature of 140°C for 24 h. The resultant PZT thin film was characterized using scanning electron microscopy (SEM) and x-ray diffraction (XRD). The PZT thin film had fine nanoparticles of approximately 100 nm in diameter when the substrate was placed perpendicular to the plane of ultrasonic irradiation. The film exhibited predominantly (001) orientation when the substrate was placed parallel to the plane of ultrasonic irradiation. 相似文献
73.
Hiroyuki Sasakura Yoshiya Akagi Shigeki Tsukui Takashi Oka Motoaki Adachi 《Journal of Superconductivity》2004,17(4):509-512
There have been no report about synthesis of the Bi-2212 compound in the Bi–r–La–Cu–O system. We have succeeded in synthesizing the Bi-2212 compound by partial substitution of Pb for Sr and/or Bi in the Bi–Sr–La–Cu–O system. Two samples of nearly the single 2212 phase have been obtained at a nominal composition of Bi1.5Pb0.5Sr2.5La0.5Cu2O
z
. Both of the samples crystallize in a psedotetragonal lattice, and their lattice parameters are a = 0.5476 nm and c = 3.085 nm or a = 0.5479 nm and c = 3.055 nm. They are both superconductors. The sample with longer lattice parameter c shows an onset of the resistivity drop and zero resistivity at higher temperatures of about 40 K and about 13 K, respectively. This sample also shows a diamagnetic signal starting at about 35 K with lowering temperature. 相似文献
74.
Murakami A. Hosaka K. Fukushima M. Maeda M. Tsuya N. 《IEEE transactions on magnetics》1989,25(3):2739-2744
A digitizer with a cordless cursor to input coordinates of graphics is described. The digitizer utilizes magnetostrictive delay lines made of iron-base amorphous ribbons. During propagation of the magnetoelastic wave in the ribbon, the output signal is generated by a solenoid coil wound through the entire ribbon length when the wave arrives at a position immediately underneath the cursor magnet. Resolution of the above position was 0.1 mm, and a high cursor position of 12 mm was realized 相似文献
75.
Noboru Tohge Masahiro Tatsumisago Tsutomu Minami Motoaki Adachi Yasuo Kousaka Kikuo Okuyama 《Journal of the American Ceramic Society》1991,74(9):2117-2122
The morphology and crystalline phases of superconducting fine particles with a composition of Bi2 Ca1 Sr2 Cu2 Ox were studied in terms of preparation conditions, using an aerosol flow reactor with varying temperature profiles: constant, increasing, and humped temperature distributions. The temperature profile in the reactor was found to affect greatly the morphology of the superconducting particles produced. The humped distribution with maximum temperatures over 900°C provided solid particles consisting mainly of the 80 K phase, when other preparation conditions were optimized. This finding indicates the possibility of controlling the morphology, as well as the crystalline phases, of superconducting particles by spray pyrolysis. 相似文献
76.
Synapsins I and II are abundant phosphoproteins that are localized to synaptic vesicles and have essential functions in regulating synaptic vesicle exocytosis. Synapsins contain a single evolutionarily conserved, large central domain, the C-domain, that accounts for the majority of their sequences. Unexpectedly, the crystal structure of the C-domain from synapsin I revealed that it is structurally closely related to several ATPases despite the absence of sequence similarities (Esser, L., Wang, C.-R., Hosaka, M., Smagula, C. S., Südhof, T. C., and Deisenhofer, J. (1998) EMBO J., in press). We now show that the C-domains of both synapsin I and synapsin II constitute high affinity ATP-binding modules. The two C-domains exhibit similar ATP affinities but are differentially regulated; ATP binding to synapsin I is Ca(2+)-dependent whereas ATP binding to synapsin II is Ca(2+)-independent. In synapsin I, the Ca2+ requirement for ATP binding is mediated by a single, evolutionarily conserved glutamate residue (Glu373) at a position where synapsin II contains a lysine residue. Exchange of Glu373 for lysine converts synapsin I from a Ca(2+)-dependent protein into a Ca(2+)-independent ATP-binding protein. Our studies suggest that synapsins I and II function on synaptic vesicles as ATP-binding proteins that are differentially regulated by Ca2+. 相似文献
77.
Masanori Hosaka Jun-ichi Nakagami & Masami Kurano 《International Transactions in Operational Research》2002,9(1):113-123
In this paper, the average case of finite state controlled Markov set-chains with R p -set-valued rewards are considered. The optimization is done by a pseudo-order relation on the set of all convex and compact subsets of R p induced by a closed convex cone. We introduce a v -step contractive property (minorization condition) for the average case and by use of this method the average expected reward set from a periodic policy is characterized. And, applying the scalarization technique, a Pareto optimal policy is obtained. Also, a numerical example is given to comprehend our results. 相似文献
78.
Tanizawa H Shima M Ikehara C Kobata M Sato M 《Shokuhin eiseigaku zasshi. Journal of the Food Hygienic Society of Japan》2005,46(5):185-197
A simple and rapid method was developed for the screening of 82 pesticides/metabolites in a wide variety of crops, using solid-phase extraction and liquid chromatography with tandem mass spectrometry (LC/MS/MS). After extraction with methanol, the filtered extracts were made up to 100 mL and a 2 mL aliquot was subjected to solid-phase extraction. Co-extractives were removed with a C18 mini-column, while pesticides were retained on 3 kinds of mini-columns (HLB, SAX, activated carbon), and then eluted with acetonitrile. Analysis was performed by LC/MS/MS, and MS acquisition parameters were established in positive and negative ESI modes. The utility of the method was demonstrated by the analysis of 6 crops (carrot, cabbage, onion, spinach, lemon, brown rice) and one mixed vegetable juice. Of 82 compounds tested, 75 in carrot and 62 in lemon were obtained with recoveries ranging from 70-120%. For all samples tested, 75 compounds could be obtained with recoveries of over 50%, and the detection limits of most compounds were lower than 0.01 microg/g. This method provides acceptable performance for analysis of these 75 compounds. Further, by using aliquots of the extracts with small-scale mini-columns, purified samples could be obtained. This proposed method with small matrix effects, is effective and suitable for screening of multiple residual pesticides by using LC/MS/MS. 相似文献
79.
Stress analysis of optical fibers by a finite element method 总被引:6,自引:0,他引:6
Stress-induced birefringence in single-mode optical fibers having arbitrary shape of core has been investigated using a finite element method. The calculated modal birefringence due to the thermal stress and/or stress caused by external forces in noncircular core fibers is compared with the values obtained by measurement of polarization properties, showing good agreement. 相似文献
80.