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排序方式: 共有451条查询结果,搜索用时 15 毫秒
21.
Yan Liu Yoshihiro Kageyama Sumio Murakami 《International Journal of Mechanical Sciences》1998,40(2-3)
A new approach to creep cavitation damage is developed by combining the basic features of continuum damage mechanics and mechanism-based cavitation models. Based on a polycrystal microstructures simulated by Voronoi tessellation, an anisotropic continuum damage variable is defined, and its evolution is given by applying the mechanism-based equations of cavity nucleation and growth to each grain boundary. Macroscopic creep deformation coupled with the damage variable is calculated by damage mechanics equations. The proposed method has been applied to investigate the damage evolution under uniaxial tension and reversed shear loading conditions. 相似文献
22.
Oleg Vasylkiv Yoshio Sakka Valeriy V. Skorokhod 《Journal of the American Ceramic Society》2006,89(6):1822-1826
CeCl3 ·7H2 O and GdCl3 ·6H2 O that were dissolved in water were precipitated with urea (NH2 CONH2 ) to produce matrix agglomerates for three-component nano-reactors. Mixing hexamethylenetetramine with dilute nitric acid resulted in the formation of well-dispersed nano-particles of cyclotrimetilene trinitramine (C3 H6 N6 O6 ) (RDX) in the solvent. Nano-reactors were produced by impregnating the nano-C3 H6 N6 O6 into the matrix agglomerates of an intermediate complex of cerium and gadolinium compounds. Blast initiation of the C3 H6 N6 O6 resulted in extremely rapid detonation and gaseous products formation at temperatures of 2000°–5000°C, which were compressed into a volume nearly equal to the initial volume of each RDX nano-particle. Multiple "nano-blasts" occurred in the volume of each nano-reactor. The impact of the blast waves led to fragmentation of the surrounding matter. The evolution of a large volume of gaseous products dissipated the heat of the process and limited temperature increase, thus reducing the possibility of local sintering among the primary particles. The short-term high temperature generated during the blasts enhanced the solid solubility of the metal oxides. Uniform aggregates of 22∼74 nm consisting of 6∼14 nm crystallites of gadolinia in ceria solid solution were synthesized. 相似文献
23.
Qian Wang Chunfeng Hu Shu Cai Yoshio Sakka Salvatore Grasso Qing Huang 《International Journal of Applied Ceramic Technology》2014,11(5):911-918
High‐purity ternary laminated compound Ti3SiC2 was successfully synthesized by a microwave heating method in the flowing argon for the first time. The mixtures of titanium, silicon, and graphitic carbon (Cgc) or activated carbon (Cac) with different molar ratios were used to investigate the reaction mechanisms. It was confirmed that Ti3SiC2 with high purity of 98 vol.% was achieved without the aids of Al. The optimum experimental parameters were determined as Ti/Si/Cgc having the molar ratio of 3/2.2/2, first holding at 1480°C for 30 min, and subsequent dwelling at 1300°C for 60 min. 相似文献
24.
Minako Nagamori Taro Shimonosono Soichiro Sameshima Yoshihiro Hirata Naoki Matsunaga Yoshio Sakka 《Journal of the American Ceramic Society》2009,92(S1):S117-S121
A thin film (60 μm thick) of a gadolinium-doped ceria (GDC) electrolyte was prepared by the doctor blade method. This film was laminated with freeze-dried 42 vol% NiO–58 vol% GDC mixed powder and pressed uniaxially or isostatically under a pressure of 294 MPa. This laminate was cosintered at 1100 °–1500 °C in air for 4–12 h. The laminate warped because of the difference in the shrinkage of the electrolyte and electrode during the sintering. A higher shrinkage was measured for the electrode at 1100 °–1200 °C and for the electrolyte at 1300 °–1500 °C. The increase of the thickness of anode was effective in decreasing the warp and in increasing the density of the laminated composite. The maximum electric power density with a SrRuO3 cathode using 3 vol% H2 O-containing H2 fuel was 100 mW/cm2 at 600 °C and 380 mW/cm2 at 800 °C, respectively, for the anode-supported GDC electrolyte with 30 μm thickness. 相似文献
25.
Molecular breeding of cellulolytic microbes, plants, and animals for biomass utilization 总被引:1,自引:0,他引:1
Cellulosic materials are the major components of fibrous biomass produced as a result of photosynthesis and are considered as a reservoir of solar energy and organic materials. In order to cope with the problems of food and energy shortages expected in the near future, biotechnologists are encouraged to develop new technologies for the more effective utilization of the world's sustainable resources, i.e., biomass. One way is to engineer microorganisms and animals with the capability of digesting and utilizing cellulosic materials, and plants which can be easily degraded by cellulolytic enzymes. In this article, we summarize recent studies on the molecular breeding of cellulolytic organisms for biomass utilization along with some considerations regarding cellulolytic enzymes. 相似文献
26.
Effect of Ultrasonication on the Microstructure and Tensile Elongation of Zirconia-Dispersed Alumina Ceramics Prepared by Colloidal Processing 总被引:1,自引:0,他引:1
Tohru S. Suzuki Yoshio Sakka Keishi Nakano Keijiro Hiraga 《Journal of the American Ceramic Society》2001,84(9):2132-2134
To obtain dense, fine-grained ceramics, fine particles and advanced powder processing, such as colloidal processing, are needed. Al2 O3 and ZrO2 particles are dispersed in colloidal suspensions by electrosteric repulsion because of polyelectrolyte absorbed on their surfaces. However, additional redispersion treatment such as ultrasonication is required to obtain dispersed suspensions because fine particles tend to agglomerate. The results demonstrate that ultrasonication is effective in improving particle dispersion in suspensions and producing a homogeneous fine microstructure of sintered materials. Superplastic tensile ductility is improved by ultrasonication in preparing suspensions because of the dense and homogeneous fine microstructure. 相似文献
27.
Modeling and energy simulation of the variable refrigerant flow air conditioning system with water-cooled condenser under cooling conditions 总被引:1,自引:0,他引:1
As a new system, variable refrigerant flow system with water-cooled condenser (water-cooled VRF) can offer several interesting characteristics for potential users. However, at present, its dynamic simulation simultaneously in association with building and other equipments is not yet included in the energy simulation programs. Based on the EnergyPlus's codes, and using manufacturer's performance parameters and data, the special simulation module for water-cooled VRF is developed and embedded in the software of EnergyPlus. After modeling and testing the new module, on the basis of a typical office building in Shanghai with water-cooled VRF system, the monthly and seasonal cooling energy consumption and the breakdown of the total power consumption are analyzed. The simulation results show that, during the whole cooling period, the fan-coil plus fresh air (FPFA) system consumes about 20% more power than the water-cooled VRF system does. The power comparison between the water-cooled VRF system and the air-cooled VRF system is performed too. All of these can provide designers some ideas to analyze the energy features of this new system and then to determine a better scheme of the air conditioning system. 相似文献
28.
Tohru S. Suzuki Tetsuo Uchikoshi Yoshio Sakka 《Journal of the European Ceramic Society》2009,29(12):2627-2633
The preparation of oriented AlN bulk ceramics with and without additives was achieved by slip casting in a high magnetic field. The a and b axes of the AlN were aligned parallel to the direction of the magnetic field. The degree of crystallographic orientation was controlled by the viscosity of the slurry and the grain growth during sintering attributed to the sintering additives. The mechanical properties of the textured AlN depended on the direction of the crystallographic orientation. 相似文献
29.
Honda Y Kitaoka M Sakka K Ohmiya K Hayashi K 《Journal of Bioscience and Bioengineering》2002,93(3):313-317
The kinetic parameters of Cex, a family 10 xylanase from Cellulomonas fimi, were determined at various pH levels using soluble birchwood xylan (BWX) as a natural polymeric substrate along with three other synthetic aryl-beta-D-xylobioside substrates. Using BWX, a high level of substrate inhibition was observed which increased with decreasing pH. In contrast, typical Michaelis-Menten-type profiles were obtained using the three aryl-beta-D-xylobiosides as substrates. The k(cat) values determined using o-nitrophenyl-beta-D-xylobioside did not change as the pH increased, whereas the k(cat) values obtained with BWX, phenyl-beta-D-xylobioside and p-nitrophenyl-beta-D-xylobioside decreased, suggesting that the presence of an ortho nitro group affects the activity displayed by Cex. These differences were not observed with XynB from Clostridium stercorarium F9, a member of the same family of xylanases as Cex. These results indicate that a careful evaluation is required when employing substituted aryl-beta-D-xylobiosides in the characterization of xylanases. 相似文献
30.
Yamaoka H Hayashi H Karita S Kimura T Sakka K Ohmiya K 《Journal of Bioscience and Bioengineering》1999,88(3):328-330
Chitinase B (ChiB) was purified from the culture supernatant of Xanthomonas sp. strain AK by Phenyl-Toyopearl 650M and DEAE-Toyopearl 650M column chromatographies. The purified enzyme preparation gave a single band on SDS-polyacrylamide gel electrophoresis and the molecular weight of ChiB was estimated to be 48,000. The enzyme was optimally active at pH 6.0 and 60 degrees C. N-Terminal amino acid sequence analysis suggested that ChiB is a member of glycosyl hydrolase family 18 and that it is genetically different from ChiA recently reported (Sakka et al., J. Ferment. Bioeng., 86, 527-533, 1998). Immunological analysis suggested that ChiB was the major chitinase species in the culture supernatant of Xanthomonas sp. strain AK and that production of the enzyme was induced by the presence of chitin. 相似文献