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排序方式: 共有374条查询结果,搜索用时 250 毫秒
81.
S. Ban-Ya F. Ishii Y. Iguchi T. Nagasaka 《Metallurgical and Materials Transactions B》1988,19(2):233-242
The rate of nitrogen desorption from inductively stirred liquid iron, iron-carbon, and iron-chromium alloys with argon carrier gas has been measured by the sampling method for a wide range of nitrogen, carbon, and chromium contents mainly at 1600 °C. The results obtained by the present work and other data of previous investigators are used to clarify the reaction mechanism of nitrogen desorption from liquid iron. The rate of nitrogen desorption from liquid iron and iron alloys is second order with respect to nitrogen content in the metal under the present condition, and mutual relationships among interfacial chemical reaction, liquid-phase mass transfer, and gas-phase mass transfer are elucidated. The effects of oxygen and sulfur on the rate of nitrogen desorption are given byk ' c ’ = 3.15?N 2 [1/(1 + 300a0 + 130as)]. Carbon dissolved in iron increases the rate of nitrogen desorption, and chromium decreases it. The effects of these alloying elements can be explained by the change of the nitrogen activity in the metal. 相似文献
82.
A. Toshimitsu Yokobori Jr Takeo Yokobori Kiyoshi Sato Kazuo Syoji 《Fatigue & Fracture of Engineering Materials & Structures》1985,8(4):315-325
Fatigue crack growth behaviour under mixed modes I and II was studied by applying in-phase alternating tensile and torsional loading to a thin-walled hollow cylindrical specimen with an initial crack. In the linear region of a log-log plot where da/dN=A(ΔK)m, da/dN at first decreases with increasing ΔK110 component and then approaches a minimum close to the value of ΔK110/ΔK10~ 0.58; here ΔK110/ΔK10 is the ratio of the initial ΔKII to the initial ΔK1., When ΔK110/ΔK10 increases further, da/dN increases. Under shear mode, da/dN becomes higher than that under mode I. The ΔK1, and ΔK11 components during fatigue crack growth under mixed mode loading increase and decrease, respectively, with an increase in da/dN In the low crack growth rate region the fatigue crack growth rates accelerate with an increase of the initial ΔK11 component, ΔK110. Fatigue life increases with increase of ΔK110/ΔK10 under the test condition of equivalent stress range being kept constant and the pre-crack length being the same. 相似文献
83.
Toshimitsu K. Yamazato T. Katayama M. Ogawa A. 《Selected Areas in Communications, IEEE Journal on》1994,12(4):665-672
This paper presents a novel spread slotted Aloha system with channel load sensing protocol (CLSP). CLSP is an effective scheme to improve the throughput performance in spread unslotted Aloha systems. In spread slotted Aloha systems, however, it does not make sense to utilize CLSP because the slot size is usually the same as the packet size. The slot size of the proposed system is set less than the packet size, thereby enabling the authors to apply CLSP and improving the throughput performance. Another feature of the proposed system is that the system is not likely affected by the time difference between channel load sensing and timing of packet access, which they call the access timing delay. Throughput performance of the proposed system is evaluated in the presence of the access timing delay and a significant increase of the throughput is shown compared with that of spread unslotted Aloha with CLSP 相似文献
84.
Osamu Yamada Toshimitsu Suzuki Jose H. Then Toshihiro Ando Yoshihisa Watanabe 《Fuel Processing Technology》1985,11(3):297-311
The catalytic activity of metal carbonyl complexes of chromium, molybdenum, tungsten, manganese, iron, cobalt, and nickel in the liquefaction of coal (Illinois No. 6, Wandoan and Mi-ike) was investigated. The carbonyl compounds of molybdenum, tungsten, iron, cobalt, and nickel acted as highly active catalysts for the liquefaction of Illinois No. 6 coal, resulting in high coal conversion (>90%) and high oil yield (>32%), under hydrogen pressure of 50 kg cm?1 in a nonhydrogen-donating solvent at 425°C for 60 min. Among the catalysts surveyed, Mo(CO)6 gave the highest oil yield (57.7%) and the largest amount of hydrogen transferred to coal (3.1 wt.% of d.a.f. coal). However, the molybdenum and tungsten carbonyls did not exhibit high catalytic activity for low sulfur Wandoan coal in the absence of added sulfur. On the other hand, cobalt and nickel carbonyls showed high catalytic activity irrespective of the amount of sulfur in the reaction system. Fe(CO)5Mo(CO)6 binary catalyst promoted hydroliquefaction of Wandoan coal, resulting in increases in oil yield and transfer of hydrogen to coal in the presence of sulfur. 相似文献
85.
Monolithic glass-ceramics containing Al2O3 or TiO2 were prepared in the ZrO2-SiO2 system by the sol-gel process from metal alkoxides. Tetragonal ZrO2 was precipitated by heat treatment at 900–1200 °C and its crystal growth was increased by adding TiO2 or Al2O3. Further heating at higher temperature resulted in the precipitation of zircon and monoclinic ZrO2 which was transformed from tetragonal ZrO2. The addition of Al2O3 had less effect on both the tetragonal-to-monoclinic ZrO2 transformation and the precipitation of zircon. The fracture toughness increased as the size of tetragonal ZrO2 particles increased and then decreased with the appearance of monoclinic ZrO2 or zircon. The fracture toughness of the glass-ceramics was measured in the glass-forming regions of the ZrO2-Al2O3-SiO2 system. The fracture toughness was sensitively dependent on both Al2O3 and ZrO2 content, of which the highest value achieved was 9 MPa m1/2 for the 50ZrO2·10Al2O3·40SiO2 composition. 相似文献
86.
We have developed a surface laser-light scattering apparatus to measure simultaneously surface tension and kinematic viscosity. In this method, we can obtain the surface properties by the laser heterodyne detection of light scattered from thermally excited capillary waves (called ripplon), which are typically of low amplitude (1 nm) and a characteristic wavelength (100m). Two gratings (d=100 and 200m) were employed to select the wave number of the capillary waves and to produce a reference beam for heterodyne detection. It was found through an experimental study on water that this contact-free method has considerable potential for application to measurements under extreme conditions such as high temperatures and high pressures.Paper presented at the Twelfth Symposium on Thermophysical Properties, June 19–24, 1994, Boulder, Colorado, U.S.A. 相似文献
87.
Dehydrogenation of light alkanes over oxidized diamond-supported catalysts in the presence of carbon dioxide 总被引:4,自引:0,他引:4
Kiyoharu Nakagawa Chiaki Kajita Na-oki Ikenaga Mikka Nishitani-Gamo Toshihiro Ando Toshimitsu Suzuki 《Catalysis Today》2003,84(3-4):149-157
Oxidized diamond demonstrated excellent support for the dehydrogenation of light alkanes to alkenes in the presence of CO2. Oxidized diamond-supported Cr2O3 and V2O5 catalysts exhibited comparatively higher catalytic activities in the dehydrogenation of lower alkanes in the presence of CO2. In the dehydrogenation of propane, the oxidized diamond-supported Cr2O3 and V2O5 catalysts in the presence of CO2 afforded nearly twofold higher activities than that in the absence of CO2. The activity of the oxidized diamond-supported V2O5 catalyst in the dehydrogenation of propane increased with increasing reaction temperatures. Furthermore, in the dehydrogenation of n-butane and iso-butane, a promoting effect of CO2 on butane conversion and butenes yields was observed over the oxidized diamond-supported Cr2O3 and V2O5 catalysts, though the promotion effect was small.
UV-Vis analyses of the fresh and the reacted catalysts in the presence and absence of CO2 revealed that CO2 kept the surface V2O5 and Cr2O3 in a state of oxidation slightly higher than that in the absence of CO2. 相似文献
88.
Catalytic steam gasification of Yallourn coal using sodium hydridotetracarbonyl ferrate was carried out in a semi-flow-type fixed-bed reactor at 873 and 973 K at atmospheric and high pressures. With Na[HFe(CO)4] (Fe 1.67 wt%, Na 0.68 wt%), the steam gasification of the coal was more highly promoted than with Na2CO3 (Na 2.17%) and the coal was almost completely burnt out. The gasification rate decreased with increasing carbon burnoff with or without catalyst at 873 K, but increased in the presence of the catalyst at 973 K. Under pressurized steam (0.4 MPa), the catalyst exhibited higher activity. The char, obtained from Yallourn coal under argon at 823 K for 2 h, gasified under steam partial pressures of 0.4 and 0.8 MPa behaved the same as the original coal and no increase in gasification rate with steam pressure was observed. X-ray diffraction analysis showed that Na[HFe(CO)4] was converted to Fe3O4 and Na2CO3 during the reaction. 相似文献
89.
Shinjiro Kato Kiyoharu Nakagawa Na-oki Ikenaga Toshimitsu Suzuki 《Catalysis Letters》2001,73(2-4):175-180
Alkylation of benzene with ethane was carried out using various zeolite catalysts at temperature ranges of 400–550°C. Loading of platinum onto zeolite greatly enhanced the yield of ethylbenzene. Among the zeolites tested, H-ZSM5 and H-MCM22 showed catalytic activities. By contrast, mordenite did not yield ethylbenzene. Moderate acid strength distribution is the key factor of zeolite catalysts. Optimum catalyst and conditions for this reaction are as follows. The platinum-loaded H-ZSM5 catalyst containing 6.8 wt% Pt, at a reaction temperature of 500°C, afforded ethylbenzene and styrene formation rates of 14.2 and 0.8 mmolh–1g-cat–1, respectively (benzene-based yields 7.3 and 0.4%). In the alkylation of benzene with ethane over platinum-loaded H-ZSM5, ethene was initially formed from ethane over the metallic platinum. Then the alkylation proceeded over the acid sites of H-ZSM5. 相似文献
90.
Mass spectrometry was used to monitor in-situ gaseous species that were generated at the head-disk interface (HDI) in a high vacuum. It was found that the end groups of the lubricants significantly affected the wear durability at the HDI; piperonyl (–CH2-phe = (O)2 = CH2) terminated Fomblin AM3001 lubricant exhibited longer life than hydroxyl (–OH) terminated Fomblin ZDOL lubricant. The continuous removal of the lubricants resulted in a continuously increasing friction coefficient. Further, the characteristics of tribochemical reactions of the lubricants (Fomblin Z series) with different end groups was investigated in details using Time-of-Flight Secondary Ion Mass Spectroscopy (TOF-SIMS) just after the sliding tests. It was found that the decomposition of the end groups was more significant than that of the backbone. The lubricants terminated with the following groups showed the following order of increasing decomposition: –CH2O-CH2-phe = (O)2 = CH2 (AM3001), –CH2OH (ZDOL) < –CH2OCH2CH(OH)CH2OH (Z Tetraol) < –CH2(OCH2CH2)nOH (ZDOL-TX), –COOH (Z Diac). The decomposition of the lubricants appeared to start from the end groups. 相似文献