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91.
When a coating film on a metal fibre or wire is brittle, it exhibits multiple-fracture under loading. In order to describe the exerted tensile stress on the segments of a coating film as a function of the distance from the end of the segments and as a function of applied stress, a new approximate calculation method is presented, assuming that the interfacial bonding strength is high enough and no interfacial debonding occurs. Using the present calculation method, effects of geometrical factors such as fibre diameter, thickness of coating film and length of segment as well as those of mechanical factors such as Young's modulus, shear modulus and the yield stress of the fibre and the coating film on the exerted tensile stress on the segments and also on the exerted shear stress at the interface are described in a quantitative manner. 相似文献
92.
Akito Takasaki Kozo Ojima Youji Taneda 《Metallurgical and Materials Transactions A》1994,25(11):2491-2496
Ti-42A1, Ti-45A1, and Ti-5OA1 (at. pct) titanium aluminides, which were cathodically hydrogen charged in a 5 pct H2SO4 solution for charging times between 1.8 ks (0.5 hours) and 14.4 ks (4 hours), were oxidized in a static air under atmospheric
pressure at temperatures between 1170 K (897 °C) and 1350 K (1077 °C). All the hydrogen-charged alloys, as well as alloys
without hydrogen charging, followed parabolic oxidation kinetics. The weight gains of the alloys after hydrogen charging for
normally less than 3.6 ks (1 hour) were 20 to 30 pct less than those without hydrogen charging. In the alloys charged with
hydrogen for more than 7.2 ks (2 hours), the weight gains increased with increasing the charging time. The activation energies
of oxidation indicated that the oxidation-controlling factor would change after a charging time of 7.2 ks (2 hours) in all
the alloys. The decrease in the activation energies with charging time was more drastic in the Ti-5OA1 alloy, which suggested
that hydrogen damage, such as cracking, was more severe in the Ti-50Al alloy than in the Ti-42A1 or Ti-45A1 alloys. The formation
of cracks during hydrogen charging provides titanium-diffusion paths and accelerates formation of rutile (TiO2) scale on the surface of the alloys. The TiO2 on the alloys after hydrogen charging formed at a comparatively lower temperature than that on the alloys without charging. 相似文献
93.
Localization of matrix metalloproteinases-1, -2, and -9 and tissue inhibitor of metalloproteinase-2 in interstitial lung diseases 总被引:1,自引:0,他引:1
Y Fukuda M Ishizaki S Kudoh M Kitaichi N Yamanaka 《Canadian Metallurgical Quarterly》1998,78(6):687-698
In interstitial lung diseases, deposition of extracellular matrix (ECM) in alveoli and degradation of ECM lead to pulmonary structural remodeling. The changes in ECM and the localization of matrix metalloproteinases (MMPs) and a tissue inhibitor of metalloproteinases (TIMP) in the lung tissues of patients with bronchiolitis obliterans organizing pneumonia (BOOP) and idiopathic pulmonary fibrosis (IPF) were investigated. Immunohistochemical analysis for the detection of fibronectin, collagen-I, -III, and -IV, smooth muscle actin, MMP-1 (interstitial collagenase), -2 (gelatinase A), and -9 (gelatinase B), and TIMP-2, and in situ hybridization for the detection of MMP-9 mRNA were performed. Western blotting of lung tissue homogenates was performed for MMP-2 and MMP-9. The gelatinolytic activities of the homogenates were also determined using gelatin zymography. Fibronectin and collagen-I, -III, and -IV were detected in the intra-alveolar fibrosis in addition to the interstitium of these diseases. MMP-1, MMP-2, MMP-9, and TIMP-2 were detected in the regenerated epithelial cells covering intra-alveolar fibrosis. Myofibroblasts in intra-alveolar fibrosis in BOOP showed predominant reaction for MMPs, and they ultrastructurally appeared to be phagocytosing collagen fibrils, and those of IPF showed a predominant reaction for TIMP-2. New vascularization in intra-alveolar fibrosis was exclusively observed in cases of BOOP, and the endothelial cells were positive for MMP-2. Western blotting showed the existence of a latent form of MMP-9 and latent and active forms of MMP-2, and gelatin zymography revealed that the ratio of active/latent forms of MMP-2 in BOOP is significantly larger than that in the control lungs. Predominant MMPs in BOOP may constitute the mechanism of reversibility of fibrotic changes in this disease. TIMP-2 in myofibroblasts in IPF may contribute to the stable ECM deposition and the irreversible pulmonary structural remodeling. 相似文献
94.
Kozo Osamura Hiroshi Okuda Yoshiyuki Amemiya Hiroo Hashizume 《Metallurgical and Materials Transactions A》1988,19(8):1973-1980
The structural changes during the precipitation of G. P. zones in Al-Zn binary alloys have been investigated by means of anin situ small-angle scattering technique using synchrotron radiation. Defining a specific time, normalized by the half-completion
time, the time-dependent evolution of the precipitation process can be divided into three periods, independent of alloy composition
and quench-ing conditions. The structural and kinetic features of the first two periods have been analyzed in detail. The
first stage represents a growing process of clusters with diffuse interface into the well-defined G. P. zones. The average
size of these clusters increases, and the density decreases. The second stage corresponds to the Ostwald ripening process.
This mechanism is described by utilizing a modified Lifshitz-Slyozov-Wagner theory. 相似文献
95.
The strength of surface-damaged fibers was studied by means of a computer simulation experiment based on the Monte-Carlo method
using a simple model which assumes that the surface flaws can be regarded as mode I notches on fiber surfaces, the strength
of undamaged fibers obeys the Weibull distribution function, and the largest flaw determines the strength of damaged fibers.
Normal and exponential distribution functions were taken as the flaw size distribution function. By employing the present
simulation method, the effects of average flaw size, coefficient of variation of flaw size, density of flaws, and gage length
on average strength and its coefficient of variation were studied. It was found that the surface-damaged fibers can retain
their full strength only when the average flaw size is small, the coefficient of variation of flaw size is small, density
of flaw size is low, and gage length is short. Otherwise the average strength of damaged fibers was reduced seriously. It
was emphasized that the scatter of size of flaws and density of flaws strongly affect the strength of fibers as well as flaw
size and gage length. 相似文献
96.
The influence of several parameters on the fermentative production of nisin Z by Lactococcus lactis IO-1 was studied. Considerable attention has been focused on the relationship between the primary metabolite production of bacteriocin and lactate and cell growth, which has so far not been clarified in detail. Production of nisin Z was optimal at 30 degrees C and in the pH range 5.0-5.5. The addition of Ca2+ to the medium showed a stimulating effect on the production of nisin Z. A maximum activity of 3150 IU/ml was obtained during pH-controlled batch fermentation in the medium supplemented with 0.1 M CaCl2. It was about three times higher than that obtained under the optimal conditions for cell growth and lactic acid production. 相似文献
97.
98.
Mitsuo GEN Yasuhiro TSUJIMURA Syunsuke Ishizaki 《Computers & Industrial Engineering》1996,31(3-4):855-859
Optimal design of a Star-LAN includes a few important and difficult sub-problems. An optimal HUB allocation problem is one of the sub-problems. Neural networks based on the Boltzmann machine are suitable for solving such problems. In this paper, we apply the Boltzmann Machine Neural Networks(BMNN) to optimal HUB allocation problems on a Star-LAN computer networks. We also show some numerical experiments to demonstrate performances on solving the problems. 相似文献
99.
The influence of non-uniform fibre spacing on the strength of unidirectional fibre-reinforced metal matrix composites was
studied by means of a Monte-Carlo computer simulation experiment. The influence of yield stress of the matrix and scatter
of the fibre strength on the strength of composites were also studied for both uniform and non-uniform fibre spacings. It
was demonstrated that (1) the strength of composites with non-uniform fibre spacing is lower than that with uniform spacing
due to the high stress concentration arising from the breakage of fibres, and (2) the reduction in strength of composites
due to the non-uniformity increases with increasing scatter of fibre strength. For both cases of uniform and non-uniform spacings,
the following tendencies were observed : (a) the strength of composites increases but then decreases with increasing yield
stress of matrix, (b) it is very sensitive to yield stress of the matrix when the scatter of fibre strength is large but not
when it is small, and (c) it decreases but then increases with increasing scatter of fibre strength when the yield stress
of the matrix is high, while it decreases monotonically with increasing scatter of fibre strength when the yield stress is
low. 相似文献
100.
Effects of electron beam irradiation to-tin thin foils have been studied using high-resolution electron microscopy. By the beam irradiation, the-tin crystal at the extreme-thin foil region disappear, and amorphous oxide films covering the-tin crystal are converted into SnO2 micro-crystallites of about 5 to 10 nm in diameter. The present study also shows that the causes for the development of SnO2 are not due to the increment in the temperature of amorphous and-tin regions resulting from the electron irradiation. It seems that the conversion into SnO2 is caused by the ionization action of electron beam to atom species. 相似文献