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31.
利用ASP技术与ADO技术,采用Browser/Server模式设计了一个网上教学系统,它包括网上报名、网络课堂、在线答疑和师生信箱.用户可通过交互式动态形式来学习课程内容、进行随机抽取试题、即时打分、查看以往成绩、修改个人信息记录等功能. 相似文献
32.
研究了元素含量变化对8011铝合金防盗盖板综合性能的影响,在8011合金中改变Cu、Mn元素含量后可提高防盗盖板的强度,同时研究了烘烤处理后的强度变化问题。本文研究出了8011铝合金防盗盖板新的生产工艺制度。 相似文献
33.
The primary aim of this paper is to present results describing in detail the behaviour of ±45° E-glass/MY750 (GRP) tubes, of various wall thicknesses, subjected to equal biaxial tension–compression loading, generated under combined internal pressure and axial compression. The role played by the non-linear lamina shear has also been assessed by comparing various shear stress–strain curves for embedded laminae (extracted from tests on ±45° tubes subjected to circumferential: axial stress ratios SR=1:0, 1:−1 and 2.3:−1) with that of an ‘isolated’ lamina (measured from torsion of 90° tubes). Extracted shear failure strains, for embedded laminae, were more than four fold larger than those measured at ultimate failure for an ‘isolated’ lamina. Soft characteristics were observed in the embedded lamina and these were believed to be due to interaction between early matrix damage initiation (and propagation) and shear. Factors affecting the behaviour of the tubes, such as bulging, scissoring, thermal stresses and stress variation through the thickness are discussed. 相似文献
34.
J.-P. Croisille 《Computing》2006,78(4):329-353
We introduce a new box-scheme, called ``hermitian box-scheme' on the model of the one-dimensional Poisson problem. The scheme
combines features of the box-scheme of Keller, [20], [13], with the hermitian approximation of the gradient on a compact stencil,
which is characteristic of compact schemes, [9], [21]. The resulting scheme is proved to be 4th order accurate for the primitive
unknown u and its gradient p. The proved convergence rate is 1.5 for (u,p) in the discrete L
2 norm. The connection with a non standard mixed finite element method is given. Finally, numerical results are displayed on
pertinent 1-D elliptic problems with high contrasts in the ellipticity, showing in practice convergence rates ranging from
1 to 2.5 in the discrete H
1 norm.
This work has been performed with the support of the GDR MOMAS, (ANDRA, CEA, EDF, BRGM and CNRS): Modélisation pour le stockage des déchets radioactifs. The author thanks especially A. Bourgeat for his encouragements and his interest in this work. 相似文献
35.
研究了公安网上追逃系统的体系结构和系统的程序流程,阐述了ASP COM 后台比对服务的3层B/S模式面像网上比对的实现方法,最后给出系统的性能指标和特点。 相似文献
36.
The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the grain boundary is an essential factor of the HD activity of the alloy at room temperature. On degassing, hydrogen is released from the HD powder continuously with increasing temperature. And the residual hydrogen is as low as 0.0015% at 1073K, which shows that the hydrogen is almost exhaused. It is feasible to remove the hydrogen from the HD powder by heating treatment at the temperature of 523-723K for 1h prior to the magnetic field forming in order to decrease the harmful effect of hydrogen on the easy axis alignment of HD magnet. 相似文献
37.
高炉冷却壁的检漏及维护,是炼铁工作者十分关心的问题,本文针对邯钢高炉具体情况,探讨了高炉冷却壁漏水的原因,检漏方法,漏水冷却壁的维护及预防措施。 相似文献
38.
39.
The GILDES computer model, incorporating Stumm's concept of proton- and ligand-promoted dissolution, has been used to simulate the exposure of copper at room temperature to 210 ppb sulfur dioxide and 80% relative humidity. The agreement is good between the calculations and laboratory exposures performed under these exposure conditions. Surface reactions are relatively more important at lower relative humidities and the dominant corrosion products formed are solid state Cu2SO3, CuSO3 and Cu2U. Free-radical redox processes are important participants and control the relative distribution of Cu(I)- and Cu(H)-containing corrosion products. 相似文献
40.
Y. Nakamura Ichiro Tanaka N. Takeuchi S. Koshiba H. Sakaki 《Journal of Electronic Materials》1998,27(11):1240-1243
We studied morphology of GaAs surfaces and the transport properties of two-dimensional electron gas (2DEG) on vicinal (111)B
planes. Multi-atomic steps (MASs) are found on the vicinal (111)B facet grown by molecular beam epitaxy, which will affect
electron transport on the facet. We also studied how the morphology of GaAs epilayers on vicinal (111)B substrates depends
on growth conditions, especially on the As4 flux. The uniformity of MASs on the substrates have been improved and smooth surfaces were obtained when the GaAs was grown
with high As4 flux, providing step periodicity of 20 nm. The channel resistance of the 2DEG perpendicular to the MASs is reduced drastically
with this smooth morphology. These findings are valuable not only for fabricating quantum devices on the (111)B facets but
also those on the vicinal (111)B substrates. 相似文献