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排序方式: 共有891条查询结果,搜索用时 312 毫秒
91.
The microscopic fatigue damage characteristics and short fatigue crack growth of an unnotched SiC(SCS-6) fiber-reinforced
Ti-15-3 alloy composite were investigated in tension-tension fatigue tests (R = 0.1) carried out at room temperature for applied maximum stress of 450, 670, and 880 MPa.In situ observation of the damage-evolution process was done using optical and scanning laser microscopies, which were attached in
the fatigue machine. The first damage for the composite started from a cracking of the reaction layer followed by fiber fracture.
The matrix cracking initiated near the broken fiber when the microhardness of the matrix just to the side of the fracture
fiber reached ≈6 GPa, and the number of cycles for the initiation of this cracking decreased with the increase of applied
stress. The slope of the relation of surface crack growth lengthvs number of cycles fell into two characteristic stages; in the first stage, the rate was lower than the second stage and accelerated.
The surface crack growth rate,d(2c)/dN,vs surface crack length relation also fell into two stages (stages I and II). With the increase in surface crack length, the
crack-growth rate,d(2c)/dN, decreased in stage I and increased in stage II. The transition from stage I to stage II occurred due to the fracture of
fibers located around the first fractured fiber. It was concluded that the fatigue crack growth resistance of the composite
in the short-crack region was controlled by the fiber fracture and matrix work hardening near the fractured fiber. When the
fiber fracture occurred, the surface crack growth rate was accelerated and became faster than that of the monolithic matrix. 相似文献
92.
Oral intake of some lactic acid bacteria can have beneficial effects on the host by activating immune responses and enhancing resistance to infection by pathogens. In this study, effects of Lactobacillus sp. on the development of autoimmune disease were examined in mice with collagen-induced arthritis (CIA). CIA, a model of some types of rheumatoid arthritis (RA), can be induced in DBA/1J mice by immunizing them with bovine type II collagen (bCII). Oral intake of skimmed milk (SM) fermented with Lactobacillus delbrueckii subsp. bulgaricus OLL1073R-1 (SM/OLL1073R-1) was found to markedly inhibit the development of CIA in these mice, compared with a control group fed the control foodstuff. The inhibitory effect of SM fermented with L. delbrueckii subsp. bulgaricus OLLI 102 (SM/OLL1102) or fresh SM was weaker than that of SM/ OLL1073R-1. A deMan Rogosa Sharpe (MRS) broth culture of OLL1073R-1 without any major components of SM had the same inhibitory effect as SM/OLL1073R-1, suggesting that the inhibitory effect of SM/OLL1073R-1 is attributable not only to SM components but also to OLL1073R-1 cells, their metabolites, or both. We found that SM/OLL1073R-1 and SM caused reduced secretion of the cytokine IFN-gamma by lymph node cells (LNCs) in response to bCII. However, SM/OLL1102 did not affect the secretion of IFN-gamma. A polysaccharide fraction secreted by OLL1073R-1 also exhibited the inhibitory effects on both development of CIA and secretion of IFN-gamma. 相似文献
93.
Shuichi Nojima Masashi ToeiShigeo Hara Satoshi TanimotoShintaro Sasaki 《Polymer》2002,43(14):4087-4090
We have investigated the size dependence of crystallization within spherical microdomains formed in various poly(ε-caprolactone)-block-polybutadiene diblock copolymers (PCL-b-PB). The crystallinity (χ) and melting temperature (Tm) of the PCL block are considerably lower than those of PCL homopolymer, and χ decreases steadily and Tm decreases only slightly with decreasing radius of PCL spheres (R) for a series of PCL-b-PB with a same molecular weight (Mn). When PCL-b-PB is compared with the similar R but different Mn, χ is significantly different, suggesting that the sphere size is not the unique factor to control crystallization within spherical microdomains. 相似文献
94.
T. Kagawa H. Asai Y. Kawamura 《Photonics Technology Letters, IEEE》1991,3(9):815-817
The authors describe the fabrication of an InGaAs/InAlAs superlattice avalanche photodiode with a gain-bandwidth product of 90 GHz. The device is composed of an InGaAs/InAlAs superlattice multiplication region and an InGaAs photoabsorption layer. The effect of the superlattice multiplication region thickness on the gain-bandwidth product was studied. A gain-bandwidth product of 90 GHz was obtained for the device with a multiplication region thickness of 0.52 mu m. Low noise performance is compatible with the high gain-bandwidth product due to improvement of the ionization rate ratio made by introducing a superlattice structure into the multiplication region.<> 相似文献
95.
Estimation of residual stresses in SiC/Ti-15-3 composites and their relaxation during a fatigue test
Residual stresses induced by cooling down from the elaboration process in SiC/Ti-15-3 composite were calculated by the finite
element model using MARC and MENTAT software. An analytical model (derived from those of Eshelby and of Mikata and Taya) already
used for ceramic matrix composites has also been used in this study for elementary composites. The influence of uncertainty
on thermomechanical properties and also the influence of fibre packing and spacing were also studied. Then, evolution (relaxation)
of the thermal residual stresses (TRS) during a fatigue test were investigated. Results show that the TRS decreased rapidly
during the first cycles and then became almost constant at about one-third of their initial values.
This revised version was published online in November 2006 with corrections to the Cover Date. 相似文献
96.
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
97.
Hitomi Murakami Gunkichi Sato Shuichi Matsumoto Tatsuhiko Hirabayashi Hideo Yamamoto Wallance W. Donald Erik Bachmann 《International Journal of Satellite Communications and Networking》1986,4(3):127-137
This paper describes field test results of multi-channel digital TV transmission using a PSK/FDMA system and the related subjective test results of received TV pictures. The picture quality of the multi-channel 15 or 30 Mb/s transmission for both NTSC and PAL systems through the INTELSAT POR satellite are subjectively evaluated for various bit-error rates. In addition, subjective evaluations were made at various values of earth-station e.i.r.p. to compare the picture quality of digital transmissions with that of current half-transponder FM transmission. 相似文献
98.
Jian-Yu Zheng Shuichi Noguchi Kenjo Miyauchi Masahiro Hamada Kazushi Kinbara Kazuhiko Saigo 《Fullerenes, Nanotubes and Carbon Nanostructures》2001,9(4):467-475
A series of [60]fullerene bis-adducts having a π-electron-rich aromatic ring as a donor in a face-to-face arrangement were synthesized by the bis-cyclopropanation of [60]fullerene with tether-linked bis-malonates. One of the bis-adducts showed a photoinduced intramolecular electron transfer which caused the dramatic quenching of its fluorescence in a polar solvent. 相似文献
99.
To functionalize the surface of nanoparticles with phenyl groups for subsequent cross-linking with aromatic molecules by mutual interactions, we prepared functional nanoparticles (d = 3 nm) by silanization with phenyl-triethoxysilane. The nanoparticles had Fe(2)O(3) cores conjugated to phenyl groups; this was confirmed by Fourier transform infrared (FT-IR) spectroscopy and absorption spectrophotometry. The typical C-H and C-C peaks and the absorption at 240 nm, which corresponds to aromatic rings, were detected in the spectroscopic results for the phenyl group-modified nanoparticles. The nanoparticles could ionize aromatic (colchicine, reserpine, and bradykinin peptide) and nonaromatic (L-α-phosphatidylethanolamine,dioleoyl, and polyethylene glycol) molecules by nanoparticle-assisted laser desorption/ionization mass spectrometry. The nanoparticles worked as a selective trap and an ionization-assisting reagent in mass spectrometry for the aromatic molecular targets. 相似文献
100.
Variation of Fructooligosaccharides and their Metabolizing Enzymes in Onion Bulb (Allium cepa L. cv. Tenshin) During Long-term Storage 总被引:1,自引:0,他引:1
Noureddine Benkeblia Keiji Ueno Shuichi Onodera Norio Shiomi 《Journal of food science》2005,70(3):S208-S214
ABSTRACT: The objective of this study was to assess the status of fructooligosaccharides (FOS) in onion bulbs ( Allium cepa L. cv. Tenshin) and their metabolizing-enzymes—1-fructoexohydrolase (1-FEH), 1-kestose hydrolyzing enzyme (1-KH), fructan:fructan 1F -fructosyltransferase (1-FFT) and fructan:fructan 6G -fructosyltransferase (6G-FFT)—during storage at 15°C. Fructose varies slightly, whereas 1-kestose peaked after 6 wk and then decreased progressively during the last 18 wk of storage. Lower degree of polymerization (DP) 3 to 6) FOS, higher (DP 7 to 12) FOS, total FOS, and total carbohydrates showed similar and close patterns during 24 wk. They varied slightly at the beginning of the storage period; afterward they decreased progressively and regularly during the last 20 wk of storage. 1-FEH and 1-KH activities were low but peaked abruptly after 12 and 16 wk, respectively, after which they decreased to levels higher (1-FEH) or similar (1-KH) to those observed at the beginning of the storage. Surprisingly, 1-FFT activity showed similar pattern to the variation of 1-KH hydrolyzing activity; on the other hand, 6G-FFT, although higher, was stable during 16 wk but decreased after that. The results allowed us to associate FOS to the dormancy and sprouting states, and the peaks of the degrading enzymes were shown to signal the release of dormancy of onion bulb. 相似文献