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排序方式: 共有494条查询结果,搜索用时 31 毫秒
21.
Koh-ichi Sugimoto Tomohiko Hojo Junya Kobayashi 《Materials Science & Technology》2017,33(17):2005-2009
Transformation-induced plasticity (TRIP)-aided bainitic ferrite steels developed for automotive applications have attractive mechanical properties such as ductility, formability, toughness, fatigue strength and delayed fracture strength. These mechanical properties are principally associated with a ductile lath-structure matrix and the strain-induced transformation of the metastable-retained austenite films of 3–20 vol.%. In this paper, data on the microstructural and mechanical properties of the low-carbon TRIP-aided bainitic ferrite steels are critically assessed, as well as their deformation mechanism. 相似文献
22.
The objective of this study is to evaluate simultaneously the time dependence of the thermal diffusivity of carbon-carbon composites (C/C composites) and their porosity during heat treatment using the electromagnetic ultrasonic technique. This paper describes two kinds of experiments conducted to confirm the principle for simultaneous measurement of both the ultrasonic velocity (used to evaluate the porosity) and the thermal diffusivity at room temperature. For each material, the samples used in both experiments were identical. The ultrasonic velocity of type 304 stainless steel and its thermal diffusivity were 5.85 km/s and 3.8 mm2/s with precisions of ±1.6 and ±8 percent, respectively. The ultrasonic velocity of a two-dimensional woven C/C composite and its thermal diffusivity were 2.86 km/s and 4.8 mm2/s with precisions of ±5.0 and ±8 percent, respectively. The results appear to indicate that the electromagnetic ultrasonic technique can measure the ultrasonic velocity and the thermal diffusivity simultaneously and that it is also applicable to C/C composites. © 1997 Scripta Technica, Inc. Heat Trans Jpn Res, 25(5): 308–322, 1996 相似文献
23.
Katsuda T Shiraishi H Ishizu N Ranjbar R Katoh S 《Journal of Bioscience and Bioengineering》2008,105(3):216-220
Flashing light from blue light emitting diodes is an effective method for the reduction of energy consumption in the bioproduction of astaxanthin by Haematococcus pluvialis. We investigated the effects of light intensity and frequency on the final astaxanthin concentration in bioproduction by H. pluvialis grown mixotrophically. The final astaxanthin concentration under illumination with flashing light, with frequencies ranging from 25 to 200 Hz, was dependent on the light intensity and on the duty cycle and was equivalent, or higher, in comparison with that under illumination with continuous light at the same incident intensity. The light intensity determined the maximum attainable concentration of astaxanthin under continuous illumination. Under illumination with flashing light, the ratio of the final astaxanthin concentration to the maximum concentration at a specific light intensity was correlated to the duty cycle in the frequency range from 25 to 200 Hz. The effect of lower frequencies on enhanced astaxanthin production under flashing light was also studied; at levels as low as 1 Hz, higher final astaxanthin concentrations were observed under flashing light compared to concentrations attained under continuous light. 相似文献
24.
We prepared relatively uniform supported Ru catalysts by ion‐exchange and CVD methods, using an NaY zeolite and a mesoporous
FSM‐16 as substrates, and carried out CO2 hydrogenation. They showed high activity for CO2 hydrogenation. A Ru‐ion‐exchanged catalyst showed high activity for methanol production. Co addition promoted methanol formation.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
25.
Toughening of Silicon Nitride Matrix Composites by the Addition of Both Silicon Carbide Whiskers and Silicon Carbide Particles 总被引:1,自引:0,他引:1
Hironori Kodama Takaaki Suzuki Hiroshi Sakamoto Tadahiko Miyoshi 《Journal of the American Ceramic Society》1990,73(3):678-683
Si3 N4 matrix composites reinforced by SiC whiskers, SiC particles, or both were fabricated using the hot-pressing technique. The mechanical properties of the composites containing various amounts of these SiC reinforcing materials and different sizes of SiC particles were investigated. Fracture toughness of the composites was significantly improved by introducing SiC whiskers and particles together, compared with that obtained by adding SiC whiskers or SiC particles alone. On increasing the size of the added SiC particles, the fracture toughness of the composites reinforced by both whiskers and particles was increased. Their fracture toughness also showed a strong dependence on the amount of SiC particles (average size 40 μm) and was a maximum at the particle content of 10 vol%. The maximum fracture toughness of these composites was 10.5 MPa·m1/2 and the flexural strength was 550 MPa after addition of 20 vol% of SiC whiskers and 10 vol% of SiC particles having an average particle size of 40 μm. These mechanical properties were almost constant from room temperature to temperatures around 1000°C. Fracture surface observations revealed that the reinforcing mechanisms acting in these composites were crack deflection and crack branching by SiC particles and pullout of SiC whiskers. 相似文献
26.
Koji Ouchi Shoichi Ibaragi Ataru Kobayashi Kazuyuki Tanimoto Masataka Makabe Hironori Itoh Kenji Matsubara Tomei Takekawa 《Fuel》1984,63(1):78-83
After solvent extraction of Taiheiyo, Miike and Balmer coals using wash oil under nitrogen atmosphere at 370 °C for 30 min, the extraction yield is always within the additivity law. Further studies used Yallourn, Soyakoishi, Taiheiyo, Horonai, Miike, Shin Yubari, Balmer coals and their blends which were hydrogenated in tetralin, wash oil or creosote oil, with or without catalyst, at 400–450 °C under 10 or 3 MPa of initial hydrogen pressure. When hydrogen is available, the additivity law exists for blended coals, but when the hydrogen supply is deficient, the experimental conversion of blended coals is always lower than calculated conversions. This may be due to the faster consumption of the hydrogen by more reactive coals and thus the less reactive coals were unable to react with hydrogen. 相似文献
27.
Three North Dakota lignites with almost the same percentage carbon have been used to determine the relation between chemical structure and reactivity to hydrogenation. Average structural indices of the lignites were estimated using the pyridine-soluble products after alcohol-alkali treatment, the structural indices obtained at various reaction times being extrapolated to zero reaction time. Hydrogenation was influenced by the average structure, with the lignite having higher aromaticity, higher molecular weight of the pyridine extract from the alcohol-alkali reaction product, larger aromatic ring size and lower content of aliphatic structure, showing a smaller degree of conversion. 相似文献
28.
Koji Matsui Nobukatsu Ohmichi Michiharu Ohgai Naoya Enomoto Junichi Hojo 《Journal of the American Ceramic Society》2005,88(12):3346-3352
The sinterabilities of fine zirconia powders including 5 mass% Y2 O3 were investigated, with emphasis on the effect of Al2 O3 at the initial sintering stage. The shrinkage of powder compact was measured under constant rates of heating (CRH). The powder compact including a small amount of Al2 O3 increased the densification rate with elevating temperature. The activation energies at the initial stage of sintering were determined by analyzing the densification curves. The activation energy of powder compact including Al2 O3 was lower than that of a powder compact without Al2 O3 . The diffusion mechanisms at the initial sintering stage were determined using the new analytical equation applied for CRH techniques. This analysis exhibited that Al2 O3 included in a powder compact changed the diffusion mechanism from grain boundary to volume diffusions (VD). Therefore, it is concluded that the effect of Al2 O3 enhanced the densification rate because of decrease in the activation energy of VD at the initial sintering stage. 相似文献
29.
Y Hojo 《The Science of the total environment》1986,52(1-2):83-91
Breast milk samples collected sequentially from five lactating women were analysed for selenium and Se-dependent glutathione peroxidase (GSH-Px), which is the only active form of Se known in man. Both GSH-Px and Se contents of breast milk decreased with increasing time of lactation and reached a plateau at a month post-partum. This sequential change was not due to the Se intake of the mother as reflected in urinary Se content. GSH-Px and Se contents of mature milk were strictly regulated irrespective of the Se intake of the mother. There was a significant positive correlation between GSH-Px and Se contents of breast milk. Mean GSH-Px and Se contents and the proportion of GSH-Px-bound Se content of the total Se content in mature milk were 38.8 U ml-1, 22.5 ng ml-1 and 23.4%, respectively. Preservation of mature milk at -20 degrees C decreased linearly its GSH-Px activity with increasing time at a rate of 5.8 U ml-1 day-1. 相似文献
30.
Susumu Kashihara Shoji Otani Hironori Orikasa Yasuto Hoshikawa Jun-ichi Ozaki Takashi Kyotani 《Carbon》2012,50(9):3310-3314
A technique to determine a trace amount of hydrogen in carbon materials heat-treated above 1000 °C was developed. Three types of carbons prepared from poly(furfulyl alcohol), poly(vinyl chloride) and mesophase carbon microbeads were heat-treated at various temperatures ranging from 1000 to 1800 °C. Then they were gasified by O2 in a fixed bed flow reactor, and the H2O gases formed during the gasification processes were carefully monitored with a Karl Fischer moisture analyzer. As a result, this method makes it possible to determine the hydrogen contents in the carbons down to three places of decimals as a weight percent and can detect even a trace amount of hydrogen as low as 0.002 wt.%. A possible chemical structure of carbon edge sites was also discussed based on the experimentally determined hydrogen contents. 相似文献