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排序方式: 共有1629条查询结果,搜索用时 15 毫秒
931.
Hirofumi Sumi Toshiaki Yamaguchi Koichi Hamamoto Toshio Suzuki Yoshinobu Fujishiro 《Journal of the American Ceramic Society》2013,96(11):3584-3588
The effects of anode microstructure on mechanical and electrochemical properties were investigated for anode‐supported microtubular solid oxide fuel cells (SOFCs). The anode microstructures can be varied by the change in pore formers. For example, the acrylic resin pore former was burnt more rapidly at lower temperature than the graphite pore former during sintering. The acrylic resin pore former can introduce macropores with a diameter of several micrometers in nickel–yttria‐stabilized zirconia (Ni–YSZ) anode. The walls of the macropores were packed with the nickel and YSZ particles. Although the Ni–YSZ anode microtube using the 10 wt% acrylic resin pore former was compatible with high porosity and mechanical strength, the maximum fuel utilization was limited to 72%. On the other hand, the graphite pore former can produce a relatively uniform distribution of micropores with a diameter of several hundred nanometers. The mechanical strength was reduced with a rise in porosity for the Ni–YSZ microtube using the graphite pore former in comparison with the acrylic resin. However, a high fuel utilization of 93% was realized for the microtubular SOFCs using the 10 wt% graphite pore former in spite of lower porosity than the acrylic resin. The selection of a pore former is important to obtain higher power generation efficiency for anode‐supported microtubular SOFCs. 相似文献
932.
Masahiro Tajima Miki Niwa Yasushi Fujii Yutaka Koinuma Reiji Aizawa Satoshi Kushiyama Satoru Kobayashi Koichi Mizuno Hideo Ohu chi 《Applied catalysis. B, Environmental》1996,9(1-4):167-177
The decomposition of chlorofluorocarbons (CFCs) in the presence of water was examined over a variety of solid acid catalysts. More than 40% of the conversion of CFC was observed on HY zeolite, H-mordenite, H-ZSM-5, γ-Al2O3, and SiO2TiO2 catalysts, and the selectivity to CO and CO2 was nearly 100% except on γ-Al2O3. Although the H-mordenite had the highest activity among the tested catalysts, it was gradually deactivated during the reaction due to the elimination of Al atoms from the zeolite framework. A good relationship was found between the reactivity on H-mordenite and the bond energy of CCl in compounds of CCl4, CCl3F, CCl2F2, and CClF3, suggesting that the rate controlling step was the cleavage of the CCl bond. 相似文献
933.
Tatsuki Kitayama Koichi Ute Masanori Yamamoto Nobutaka Fujimoto Koichi Hatada 《Polymer Bulletin》1991,25(6):683-688
Summary Highly isotactic block and random copolymers of methyl methacrylate (MMA) and ethyl methacrylate (EMA) were prepared witht-C4H9MgBr in toluene at-60°C.1H NMR spectra of the copolymers were measured in nitrobenzene-d5 at 110°C and 500 MHz and analyzed in regard to monomer sequence and the end group. NMR signals due to the monomeric units provide clear indications for distinguishing the block copolymers from the random copolymers. The chemical shift of the initiator fragment signal is so sensitive to the adjacent monomeric unit that PMMA-block-poly(EMA) and poly(EMA)-block-PMMA can be differentiated spectroscopically. The main part of the spectrum for a mixture of PMMA and poly(EMA) prepared witht-C4H9MgBr is identical to those for the block copolymers but the mixture shows twot-C4H9-signals arising from both homopolymers and thus can be distinguished from the block copolymers. 相似文献
934.
Makoto Kuwabara Hirofumi Matsuda Koichi Hamamoto 《Journal of the American Ceramic Society》1997,80(7):1881-1884
Thin, semiconducting barium titanate (BaTiO3 ) ceramic bars, with a diameter of 10 to 20 μm, consisting of single grains joined together in series have been prepared to investigate the piezoresistivity in the materials, which was evaluated from their current ( I )-voltage ( V ) characteristics under the loading condition of various bending stresses. I-V characteristics of single grain boundaries in some of the materials were found to exhibit distinct differential negative resistance (DNR) at room temperature with its feature changing with stress. The DNR appeared on the I-V curves at an electric field of several volts per one grain, and has been confirmed to be connected with the transition of current between two conduction states in the grain boundary region. The obtained results indicate that this phenomenon cannot be interpreted by a rise in the temperature of the materials up to their positive temperature coefficient of resistivity (PTCR) region above the Curie point by Joule heating due to current flow, that is their self-heating effect. This newly observed DNR phenomenon has thus been tentatively interpreted by the morphological change in the ferroelectric domain structure in the vicinity of grain boundaries under mechanical and electric stresses, on an assumption that different configurations of ferroelectric domains yield different conduction states in the grain boundary due to a difference in the degree of surface acceptor charge compensation or the anisotropic carrier mobilities in the crystal. 相似文献
935.
Arsenic intake via water and food by a population living in an arsenic-affected area of Bangladesh 总被引:3,自引:0,他引:3
Ohno K Yanase T Matsuo Y Kimura T Rahman MH Magara Y Matsui Y 《The Science of the total environment》2007,381(1-3):68-76
More and more people in Bangladesh have recently become aware of the risk of drinking arsenic-contaminated groundwater, and have been trying to obtain drinking water from less arsenic-contaminated sources. In this study, arsenic intakes of 18 families living in one block of a rural village in an arsenic-affected district of Bangladesh were evaluated to investigate their actual arsenic intake via food, including from cooking water, and to estimate the contribution of each food category and of drinking water to the total arsenic intake. Water consumption rates were estimated by the self-reporting method. The mean drinking water intake was estimated as about 3 L/d without gender difference. Arsenic intakes from food were evaluated by the duplicate portion sampling method. The duplicated foods from each family were divided into four categories (cooked rice, solid food, cereals for breakfast, and liquid food), and the arsenic concentrations of each food category and of the drinking water were measured. The mean arsenic intake from water and food by all 18 respondents was 0.15 +/-0.11 mg/d (range, 0.043 - 0.49), that by male subjects was 0.18 +/- 0.13 mg/d (n = 12) and that by female subjects was 0.096 +/- 0.007 mg/d (n = 6). The average contributions to the total arsenic intake were, from drinking water, 13%; liquid food, 4.4%; cooked rice, 56%; solid food, 11%; and cereals, 16%. Arsenic intake via drinking water was not high despite the highly contaminated groundwater in the survey area because many families had changed their drinking water sources to less-contaminated ones. Instead, cooked rice contributed most to the daily arsenic intake. Use of contaminated water for cooking by several families was suspected based on comparisons of arsenic concentrations between drinking water and liquid food, and between rice before and after cooking. Detailed investigation suggested that six households used contaminated water for cooking but not drinking, leading to an increase of arsenic intake via arsenic-contaminated cooking water. 相似文献
936.
Seiichi Suda Masahiko Matsumiya Koichi Kawahara Kaori Jono 《International Journal of Applied Ceramic Technology》2010,7(1):49-54
We have developed glass/ceramic composite seals composed of glass precursors (NS particles) and ceramic precursors (S particles). The composite seals exhibited low gas permeability at room temperature −650°C, irrespective of the fusion profiles. However, short-term fusion led to the formation of pores in the seals and the pores in the seals depressed the thermal cycle durability. As for the NS/S composite ratios, the addition of S particles obviously improved the thermal cycle durability, but excess addition will bring about delamination at the seal/substrate interface. Appropriate NS/S ratios as well as an adequate fusion profile would result in composite seals with high strength and adhesion. 相似文献
937.
We developed an oleic acid oil-in-water (o/w)-type emulsion of a new tacrolimus formulation that presented an improvement
in the delivery of the drug for oral absorption. This investigation was undertaken to assess a sustained release drug delivery
system and selective drug transfer into the lymphatic system. The whole blood concentration profiles after oral administration
at a dose of 2mg/kg and bone marrow, spleen, liver, lung, small intestine, kidney, brain, and whole blood distribution after
oral administration at a dose of 1 mg/kg of o/w emulsion formulation of tacrolimus (O/W group) were compared with those of
commercially available formulation (T group) in the rat. The mean diameter of the o/w emulsion droplets was 0.47 μm immediately
after preparation. The tacrolimus entrapping efficiency of o/w emulsion was 71.3+5.0% in 12 h and did not change for 2 d.
The area under the whole blood concentration-time curve (AUC) in the O/W group was significantly higher (P<0.01) than that in the I group. In contrast, the values of constant elimination rate and total clearance in the O/W group
were significantly lower (P<0.01) than those in the T group, with a comparative bioavailability of 115.9%. The tissue concentration of tacrolimus in
the O/W group was significantly higher levels in the bone marrow, spleen, liver, lung, and small intestine, and significantly
lower in the brain and kidney, relative to the T group. The o/w emulsion of tacrolimus may be an improved dosage form via the enteral route. 相似文献
938.
Characteristics of MnOy–ZrO2 and Pt–ZrO2–Al2O3 as reversible sorbents of NOx were investigated under dynamic changes in atmosphere. These sorbents can be used reversibly with a change of C3H8 concentration in the reaction gases. Catalytic reduction of NO occurred in the presence of propane, which was more pronounced on Pt–ZrO2–Al2O3 than on MnOy-ZrO2 due to high activity of Pt surface for this reaction on MnOy in MnOy–ZrO2. The sorption was observed as soon as the atmosphere changed from a reducing to an oxidizing one. This implies that a high equilibrium partial pressure of O2 is necessary for NO uptake since the sorbed NO−3 species becomes stable. The beginning of NOx desorption atmospheres was somewhat dependent on the amount of stored NOx. The presence of propane in the gas phase strongly affected the characteristic sorption and desorption properties of MnOy–ZrO2 and Pt–ZrO2–Al2O3. The sorption and desorption properties are different for MnOy–ZrO2 and Pt–ZrO2–Al2O3, since the noble metal or metal oxide possesses unique activity for the NO reaction with C3H8 and the amount of oxygen available for oxidative sorption of NO. 相似文献
939.
Bo Wang Shao-Chun Xu Feng Jin Jian-Feng Yang Kozo Ishizaki Koichi Niihara 《Ceramics International》2014
Near zero thermal expansion porous ceramics were fabricated by using SiC and LiAlSiO4 as positive and negative thermal expansion materials, respectively, bonded by glassy material. The microstructure, mechanical properties, and thermal expansion behavior of LAS/SiC porous ceramics with different particle sizes of LiAlSiO4 were investigated. The results indicated that the coefficient of thermal expansion of the LAS/SiC porous ceramics decreased from 0.5206×10−6 to −1.1053×10−6 K−1 with increasing the LiAlSiO4 particle size from ~45 µm to ~125 μm. It was attributed to the reduction in the reaction between LiAlSiO4 and SiO2 as the particle size of LiAlSiO4 increased. Young’s modulus increased from 36 MPa to 54 MPa as the sintering temperature increased from 850 °C to 950 °C because of the good bonding between the SiC grains and the glass materials. 相似文献
940.
Safety and reliability have become important software quality characteristics in the development of safety-critical software
systems. However, there are so far no quantitative methods for assessing a safety-critical software system in terms of the
safety/reliability characteristics. The metrics of software safety is defined as the probability that conditions that can
lead to hazards do not occur. In this paper, we propose two stochastic models for software safety/reliability assessment:
the data-domain dependent safety assessment model and the availability-related safety assessment model. These models focus
on describing the time- or execution-dependent behavior of the software faults which can lead to unsafe states when they cause
software failures. The application of one of these models to optimal software release problems is also discussed. Finally,
numerical examples are illustrated for quantitative software safety assessment and optimal software release policies.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献