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61.
Mechanical shaping of an aluminium alloy reinforced with Al2O3 particulates, (Al2O3)p-Al, was carried out by a cold rolling operation. Rolling was performed unidirectionally in a direction perpendicular to the extrusion direction of the composite, until edge cracks formed. Cold rolling was found to cause particulate cracking and interfacial debonding, as wellas the redistribution of (Al2O3)p. These parameters have significant roles in determining the elastic properties of the resultant composite. 相似文献
62.
M. Prikryl A. Kroupa G. C. Weatherly S. V. Subramanian 《Metallurgical and Materials Transactions A》1996,27(5):1149-1165
The precipitation behavior of a medium carbon steel microalloyed with Ti, V, and N has been studied by analytical transmission
electron microscopy in the as-cast and isothermally heat-treated states, as well as at different stages in the thermomechanical
processing of the steel. Mixed (Ti,V) nitrides were found in all the structures, but there was no evidence for mixed carbonitride
formation. The Hillert-Staffansson model was used to predict the composition of the nitrides as a function of tem-perature.
Upon prolonged aging many of the precipitates became “fragmented” and were no longer single crystals. At the same time, the
volume fraction of precipitates dropped, while their average Ti content increased. Possible explanations for this unexpected
behavior are discussed in this article. 相似文献
63.
Cubic oxide pyrochlores, Ln2Mo2O7, Ln=SmYb,Y, (Nd1?xAx), A=Er and Yb; 0 < x < 1.0, have been synthesized and electrical properties were examined in the range 77-600K. Semiconductor behavior is observed for Ln=EuYb, Y but the resistivity and Ea are low. Sm2Mo2O7 and Nd1?xYbxMo2O7 (0.05 ≤ x ≤ 0.1) exhibit semimetallic or metallic behavior. The mechanism of conduction in these compounds is explained on the basis of band model proposed by Sleight et al. 相似文献
64.
[3-14C] Eicosatrienoic acid (Δ11,14,17) chemically synthesized from [1-14C] linolenic acid was injected intracranially into 14-day old rats and sacrificed 8 hr later. The analysis of brain fatty
acids by radio-gas liquid chromatography before and after ozonolysis showed that the tetraene fraction consisted of a desaturated
product, Δ5,11,17–20∶4, and its elongated product, Δ7,13,16,19–22∶4. Both of these products, with a combined total of 61%
of the total radioactivity recovered in the tetraene fraction, contain a nonmethylene interrupted double bond system and,
therefore, are unsuitable for further desaturation. The other two components, Δ6,9,12,15–18∶4 and Δ8,11,14,17–20∶4, must have
been formed from Δ9,12,15–18∶3, formed by retroconversion of the starting material 20∶3, followed by desaturation and elongation.
These results suggest a lack of Δ8 desaturase in the developing brain, leading to formation of Δ5,11,14,17–20∶4 rather than Δ8,11,14,17–20∶4. Howeve, the nonmethylene
interrupted double bond isomer does not restrict chain elongation. 相似文献
65.
Some age replacement policies are investigated and conditions for the unique existence of an optimum policy are derived. The optimum policy is the one which minimizes the expected cost per unit time over an infinite time span or maximizes the proportion of time during which the system is in operation. Losses have been expressed through increasing operating cost, if the objective is to minimize the expected total cost per unit time and through increasing renewal times if the objective is to maximize the availability of the system. 相似文献
66.
A two-unit warm standby redundant system with repair and preventive maintenance is considered. The pdf of the life time of a unit while in standby is assumed to be Erlangian. The pdfs of all the other random variables are arbitrary. Identifying suitable regeneration points, expressions for the Laplace transforms of the availability and reliability of the system are derived. 相似文献
67.
68.
The problems involved in the analysis of three dimensional frames having offset prismatic members are investigated. The sources of offset considered are the rigid gusset plate effects and misalignment of members from specified joint positions. The secondary effects due to axial forces are also considered in the analysis. The displacement method of structural analysis is used with an iterative procedure to take into account the secondary effects. The complete stiffness matrix has been derived. The computer program developed, based on this analysis, is also explained. From the example of steel frame folded plate it is seen that the difference in maximum axial forces and bending moments due to the offset members are about 20%. It appears that the method, developed herein, for analysing space frames having offset members, offers a very direct and versatile approach to the problem of analysing structures having misaligned members. 相似文献
69.
The computer analysis of steel braced barrel vaults is presented. This analysis is compared with the approximate method of analysis suggested by Baer. The drawbacks of Baer's method are discussed. The behaviour of these frames due to the effect of laterals, edge trusses and different types of bracing systems is predicted. Based on this parametric study an economic system of braced barrel vault is suggested for practical applications. 相似文献
70.
Anbumani?Subramanian Lakshmi?R.?Iyer A.?Lynn?Abbott Amy?E.?BellEmail author 《Machine Vision and Applications》2003,15(1):46-53
The use of a novel motorized lens to perform segmentation of image sequences is presented in this paper. The lens has the effect of introducing small, repeating movements of the camera center so that objects appear to translate in the image by an amount that depends on the distance from the plane of focus. For a stationary scene, optical flow magnitudes are therefore directly related to three-dimensional object distance from the observer. We describe a segmentation procedure that exploits these controlled observer movements and present experimental results that demonstrate the successful extraction of objects at different depths. Potential applications of our approach include image compositing, teleconferencing, and range estimation.Received: 4 July 2002, Accepted: 16 December 2002, Published online: 23 July 2003
Correspondence to: Amy E. Bell 相似文献