共查询到20条相似文献，搜索用时 31 毫秒
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Earthquake simulation tests were conducted on a 1 : 15‐scale 25‐story building model to verify the seismic performance of high‐rise reinforced‐concrete flat‐plate core‐wall building structures designed per the recent seismic code KBC 2009 or IBC 2006. The following conclusions can be drawn from the test results: (1) The vertical distribution of acceleration during the table excitations revealed the effect of the higher modes, whereas free vibration after the termination of the table excitations was governed by the first mode. The maximum values of base shear and roof drift during the free vibration are either similar to or larger than the values of the maximum responses during the table excitation. (2) With a maximum roof drift ratio of 0.7% under the maximum considered earthquake in Korea, the lateral stiffness degraded to approximately 50% of the initial stiffness. (3) The crack modes appear to be a combination of flexure and shear in the slab around the peripheral columns and in the coupling beam. Energy dissipation via inelastic deformation was predominant during free vibration after the termination of table excitation rather than during table excitation. Finally, (4) the walls with special boundary elements in the first story did not exhibit any significant inelastic behavior, with a maximum curvature of only 21% of the ultimate curvature, corresponding to an ultimate concrete compressive strain of 0.00638 m/m intended in the displacement‐based design approach. Copyright © 2014 John Wiley & Sons, Ltd. 相似文献
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Garrison Sposito 《Advances in water resources》1997,20(5-6)
Solute plume spreading in an aquifer exhibits a ‘scale effect’ if the second spatial concentration moment of a plume has a non-constant time-derivative. Stochastic approaches to modeling this scale effect often rely on the critical assumption that ensemble averages can be equated to spatial averages measured in a single field experiment. This ergodicity assumption should properly be evaluated in a strictly dynamical context, and this is done in the present paper. For the important case of trace plume convection by steady groundwater flow in an isotropic, heterogeneous aquifer, ergodicity does not obtain because of the existence of an invariant function on stream surfaces that is not uniform throughout the aquifer. The implications of this result for stochastic models of solute transport are discussed. © 1997 Elsevier Science Ltd. All rights reserved 相似文献
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Thomas Stegmaier Werner Wunderlich Tom Hager Abu Bakr Siddique J. Sarsour Heinrich Planck 《洁净——土壤、空气、水》2008,36(3):279-286
Chitosan, a natural polymer, was investigated as a possible sizing agent in fabric production by appropriate modification in the textile industry. Based on recipe developments at a laboratory‐scale, the ecological and economical potential of mainly cotton yarns were demonstrated and developed. Subsequent tests within the scope of industrial production confirmed the findings of the basic developments. As an interesting alternative to the conventional sizing process involving the removal of the size after weaving, the use of appropriate processing technologies makes it possible to apply chitosan in the form of a sizing agent resistant to wash‐out processes. Therefore, the wash‐out process and the combined wastewater loading can be avoided and the properties of chitosan can be used beneficially in the later applications of the fabric. The traditional method of sizing and weaving developments as well as the analyses of material recycling showed the possibilities of using closed circuits in textile production involving sizing agent and water. It is possible that a chitosan‐specific enzyme suitable for production conditions, which facilitates the wash‐out process in combination with the biodegradation of the wastewater in a sewage plant, could be developed. 相似文献
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B. S. Khangarot 《洁净——土壤、空气、水》1981,9(5):495-503
The lethal toxicity of mixtures of Zn2+ —Ni2+, Cu2+ —Ni2+ and Zn2+ —Cu2+ —Ni2+ to common guppy at 21£C in hard water (total hardness = 260 mg/l as CaCO3) was studied under static bioassays test conditions with renewal of the test solutions every 24 h. The heavy metals were tested separately and in mixtures. The 48 h median lethal concentrations (LC50) for individual salts were 75 mg/l Zn2+, 37 mg/l for Ni2+ and 2.5 mg/l for Cu2+. Concentrations were expressed in “toxic units” by taking them as proportions of LC50 values. Experiments showed that in the Zn2+-Ni2+ mixture, when Ni2+ was more in proportion, the toxicity was more than additive. The 48 h LC50 value and 95% confidence limits in the Ni2+-Cu2+ mixture were 0.684 (0.484 … 0.807) toxic units and the mixture produced more than the additive toxicity (synergism.). The LC50 value and its 95% confidence limits in a Zn2+?Cu2+?Ni2+ mixture also suggested that the mixture was again strictly additive. The results indicate that heavy metallic mixtures would pose a greater toxicological danger to fish than the respective individual metals. 相似文献
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Glenn E. Moglen 《水文研究》2002,16(15):3097-3098
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