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1.
Keizo Uematsu Masayori Miyashita Jin-Young Kim Zenji Kato Nozomu Uchida 《Journal of the American Ceramic Society》1991,74(9):2170-2174
Green bodies prepared by compaction of alumina granules were made transparent by an immersion liquid technique, and the internal structure was characterized with an optical microscope to study the effect of forming pressure on the internal structure. Clear images obtained by the technique provide more detailed information than other existing methods for structures ranging from one to tens of micrometers. Intergranular pores were present between unfractured granules. Their sizes and concentration tended to decrease with increasing forming pressure. However, pores were clearly present even in the green body prepared at 600 MPa. A rod- and needlelike feature was also found and was concluded to correspond to a high-density region. The significance of large pores and high-density regions on processing as well as the details of the technique is discussed. 相似文献
2.
One of the current issues in the peer-to-peer streaming systems is to supply sufficient upload bandwidth for continuous streaming of high-quality video channels. The helpers as upload bandwidth boosters can improve the streaming capacity of system, so that the imbalance of upload bandwidth between different video channel overlays is compensated. With the deployment of helpers as an intermediate level between server and peers, building and maintaining the optimal peer-helper topology becomes a challenging task since the one-directional nature of video streaming from the helpers to users makes the well-known reciprocity-based algorithms useless. Because of selfish behavior of peers and lack of a central authority among them, selection of helpers requires implicit coordination. In this paper, we design a decentralized, stochastic approximation helper selection mechanism which is adaptable to supply and demand pattern of various video channels. Our regret-tracking-based solution for allowing peers to strategically exploit their shared resources is guaranteed to converge to the correlated equilibria (CE) among the helper selection strategies. Online convergence to the set of CE is achieved through the regret-tracking algorithm which tracks the equilibrium in the presence of stochastic dynamics of helpers’ bandwidth. The resulting CE can help to select proper cooperation policies. Simulation results demonstrate that our algorithm achieves good convergence, load distribution on helpers and sustainable streaming rates for peers. 相似文献
3.
Keizo Uematsu Jin-Young Kim Masayori Miyashita Nozomu Uchida Katsuichi Saito 《Journal of the American Ceramic Society》1990,73(8):2555-2557
The internal structure of spray-dried alumina granules was characterized by optical microscopy by immersing them in a liquid having a refractive index close to that of alumina. This method provides a unique technique for the detailed analysis of the internal structure of spray-dried granules. 相似文献
4.
Yasutake Teraoka Hiroshi Ogawa Hiroshi Furukawa Shuichi Kagawa 《Catalysis Letters》1992,12(4):361-366
The coexistence of alkaline earth (Ca and Sr) and transition metal (Fe, Co and Ni) cations with Cu ions in ZSM-5 zeolite is effective in the promotion of the maximum activity and the expansion of the active temperature range for the reduction of nitric oxide with ethene in the presence of excess oxygen. 相似文献
5.
Dr. Yoshiaki Yasutake Dr. Taiki Nishioka Dr. Noriko Imoto Prof. Tomohiro Tamura 《Chembiochem : a European journal of chemical biology》2013,14(17):2284-2291
Vitamin D3 hydroxylase (Vdh) from Pseudonocardia autotrophica is a cytochrome P450 monooxygenase that catalyzes the two‐step hydroxylation of vitamin D3 (VD3) to produce 25‐hydroxyvitamin D3 (25(OH)VD3) and 1α,25‐dihydroxyvitamin D3 (1α,25(OH)2VD3). These hydroxylated forms of VD3 are useful as pharmaceuticals for the treatment of conditions associated with VD3 deficiency and VD3 metabolic disorder. Herein, we describe the creation of a highly active T107A mutant of Vdh by engineering the putative ferredoxin‐binding site. Crystallographic and kinetic analyses indicate that the T107A mutation results in conformational change from an open to a closed state, thereby increasing the binding affinity with ferredoxin. We also report the efficient biocatalytic synthesis of 25(OH)VD3, a promising intermediate for the synthesis of various hydroxylated VD3 derivatives, by using nisin‐treated Rhodococcus erythropolis cells containing VdhT107A. The gene‐expression cassette encoding Bacillus megaterium glucose dehydrogenase‐IV was inserted into the R. erythropolis chromosome and expressed to avoid exhaustion of NADH in a cytoplasm during bioconversion. As a result, approximately 573 μg mL?1 25(OH)VD3 was successfully produced by a 2 h bioconversion. 相似文献
6.
Modeling of hydrogen vacancy for dissociative adsorption of H2 on Pd (1 1 1) surface by a quantum chemical molecular dynamics 总被引:1,自引:0,他引:1
7.
Kazuo Fujiura Yasutake Ohishi Shigeki Sakaguchi Yukio Terunuma 《Journal of the American Ceramic Society》1989,72(8):1368-1372
A technique for synthesizing ultra-high-purity ZrF4 using chemical vapor deposition in a ZrBr4 –HF system is developed and a purification mechanism is clarified. The Fe concentration in ZrF4 is evaluated at less than 10 ppb based on analysis of the transmission loss spectrum of a fiber prepared using synthesized ZrF4 . Purification is achieved mainly in a sublimation process of ZrBr4 , and purification efficiency is determined by sublimation temperature and activity of impurities in ZrBr4 . The concentration of transition-metal impurities in ZrF4 , synthesized by chemical vapor deposition in the ZrBr4 –HF system, is expected to be less than 1 ppb. 相似文献
8.
Keizo Uematsu Masaki Takagi Tsunehiro Honda Nozomu Uchida Katsuichi Saito 《Journal of the American Ceramic Society》1989,72(8):1476-1478
Hydroxyapatite powder was synthesized and formed into a compact in an aqueous medium using a filter-cake method. The compact was hot isostatically pressed at 700° to 1000°C and 100 MPa for 2 h. Fully dense, transparent materials were obtained above 800°C. Both forming and densification methods were found to be important in obtaining transparent materials. 相似文献
9.
Silica‐filled styrene–butadiene rubber (SBR) unvulcanizates and their vulcanizates with different rubber/filler interactions were prepared by using several kinds of coupling agents. Tensile tests and electron spin resonance (ESR) measurements were carried out for both unvulcanized and vulcanized samples to get information on the effects of filler/rubber interactions on the breakdown of carbon–carbon (C? C) linkages in SBR and carbon–sulfur (C? S? C, C? S? S? C) linkages at the crosslinked points between rubber and sulfur by a tensile force. The combination of ESR results and stress–strain data suggested that with increasing the mechanical energy applied to the samples by the stretching, the carbon–sulfur linkages around silica particles were broken first, followed by the breakdown of carbon–sulfur and C? C linkages in the rubber matrix. The assignment of ESR spectrum was also discussed. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 相似文献
10.
A Nanashima H Yamaguchi T Tsuji E Yamaguchi T Sawai T Yasutake T Nakagoe H Ayabe 《Canadian Metallurgical Quarterly》1998,12(12):1381-1385
BACKGROUND: Differences in the physiological stress response to pneumoperitoneal (PP) and gasless abdominal wall-lifting (AWL) procedures used for laparoscopic cholecystectomy have not been properly evaluated. METHODS: We compared leukocyte count, interleukin-6 (IL-6) levels, arterial blood gases, creatinine clearance, plasma renin activity, cardiothoracic ratio, and clinical outcome in 27 patients without systemic complications who underwent laparoscopic cholecystectomy, including 11 by AWL and 16 by PP. RESULTS: Transient leukocytosis and high IL-6 levels were observed at POD 1 (postoperative day) in both groups, but both values returned to baseline by POD 2. IL-6 levels correlated significantly with operation time (p < 0.01). Changes in blood gases, creatinine clearance, plasma renin activity, and cardiothoracic ratio were not different for the two groups. The clinical outcome was similar for both groups. CONCLUSIONS: Our results indicate that both PP and AWL are appropriate for patients without serious complications. 相似文献