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111.
深基坑土钉支护的有限元分析 总被引:14,自引:3,他引:11
本文阐述了土钉支护的发展简史,针对济南济享大厦土钉支护开挖深基坑进行有限元分析并取得较准确的结果,说明在深基坑土钉支护设计中应注意的问题. 相似文献
112.
利用Love波特性计算地基动力响应 总被引:5,自引:2,他引:3
本文利用Love波弥散特性在频域上对地基出平面振动及扭振问题进行了研究。在计算区域内结构将采用有限单元划分,而在边界上则根据Love 面波特性使用传递边界有限单元。本文同时讨论了不同模态波对结构动力响应的贡献。本文方法也适合于静力分析。 相似文献
113.
水保种草有山地治理、改土开发、松林改造、封禁培育四种类型,是水土保持主要植物措施之一,见效快,效果好,效益显著。要提高认识,建立基地。做好草的转化利用. 相似文献
114.
Zakaria Chajar Michel Primet Hélène Praliaud Michèle Chevrier Catherine Gauthier Frédéric Mathis 《Catalysis Letters》1994,28(1):33-40
The role of nitrogen dioxide in the selective reduction of NO by propane over a Cu-MFI zeolite is investigated. NO2 and NO reductions were carried out under similar conditions of reaction. In the presence of oxygen, the reduction of NO by C3H8 does not differ significantly from that of NO2. In the absence of oxygen, the reduction of NO2 by propane occurs with a partial decomposition of the nitric dioxide molecule. Such a decomposition leads to the formation of oxygen, which is responsible for the increase in catalytic activity by comparison with the same reaction performed with NO. NO2 formed and released in the gas phase during the reduction of NO by propane in the presence of oxygen does not play a predominant role in the catalytic process. 相似文献
115.
116.
R. Niebuhr K. H. Bachem U. Kaufmann M. Maier C. Merz B. Santic P. Schlotter H. Jürgensen 《Journal of Electronic Materials》1997,26(10):1127-1130
Oxygen doped GaN has been grown by metalorganic chemical vapor deposition using N2O as oxygen dopant source. The layers were deposited on 2″ sapphire substrates from trimethylgallium and especially dried
ammonia using nitrogen (N2) as carrier gas. Prior to the growth of the films, an AIN nucleation layer with a thickness of about 300? was grown using
trimethylaluminum. The films were deposited at 1085°C at a growth rate of 1.0 μm/h and showed a specular, mirrorlike surface.
Not intentionally doped layers have high resistivity (>20 kW/square). The gas phase concentration of the N2O was varied between 25 and 400 ppm with respect to the total gas volume. The doped layers were n-type with carrier concentrations
in the range of 4×1016 cm−3 to 4×1018 cm−3 as measured by Hall effect. The observed carrier concentration increased with increasing N2O concentration. Low temperature photoluminescence experiments performed on the doped layers revealed besides free A and B
exciton emission an exciton bound to a shallow donor. With increasing N2O concentration in the gas phase, the intensity of the donor bound exciton increased relative to that of the free excitons.
These observations indicate that oxygen behaves as a shallow donor in GaN. This interpretation is supported by covalent radius
and electronegativity arguments. 相似文献
117.
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119.
The interaction between denitrification and methanogenesis, with methanol functioning as an electron donor, has been examined through usage of a mixed culture system of denitrifying sludge and methanogenic sludge in an anaerobic bioreactor. Competition for methanol between these two kinds of biocommunity could not be observed, whereas methanogenesis was suppressed as long as nitrate and nitrite were made available in the mixed system. The inhibition of methanogenesis in the methanogenic sludge caused by nitrogen oxides was studied. The redox potential (Eh) of the culture was monitored and/or controlled for the sake of characterizing the behavior of the biocommunities. An addition of nitrite elevated the Eh of the culture less than nitrate did. Nitrite addition, however, exerted a stronger inhibitory effect on methanogenesis as compared to nitrate at the same concentration. The influence of redox potential on the methanation of methanol was examined by using a methanogenic sludge in the Eh-stat batch culture. The hypothesis that the inhibitory effect being expressed by the nitrogen oxides is not simply attributed to an elevation of the redox potential of the culture is supported by the experimental results. The toxic effect of the nitrogen oxides themselves could also have possibly contributed significantly. 相似文献
120.
The resistance to pitting corrosion of austenitic stainless steel Cr18Mn12N has been studied in model solutions of sulphuric
acid (0.5 m) containing chloride ions (0.5 m). The cyclic potentiodynamic method has been employed to investigate the effects of chloride ions and agitation rate on the
pitting and repassivation potentials. Electron and optical microscopy, electron diffraction spectroscopy and atomic absorption
spectrometry have been used to detect the surface sites for pit formation and the growth of pit nuclei. The results obtained
with chromium–manganese–nitrogen steel have been compared with those of austenitic Cr18Ni9 stainless steel. A similarity in
pit initiation is established, while steel composition exhibits no significant effect. Cr18Mn12N steel is less prone to repassivation
as compared with Cr18Ni9 steel. 相似文献