共查询到20条相似文献，搜索用时 901 毫秒
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Wind-induced internal pressure fluctuations of structure with single windward opening 总被引：1，自引：0，他引：1
INTRODUCTION The wind loads of the exterior-protected con-struction of buildings are decided based on the pres-sure difference between the external and internalpressure. The failures of low-rise building roof andwall in high wind events are caused by a combinationof large internal and external force acting in the samedirection. A large opening in the building envelope,caused by the failure of a door or window may gen-erate large internal pressures in strong wind condi-tions, and therefore … 相似文献
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阴可 《重庆大学学报(英文版)》2003,2(2)
1. Introduction Rock mass is composed of rock blocks and various kinds of structural planes. Most structural planes are joints defined as cracks or fractures in rock along which there has been little or no displacement [1]. Under different engineering condition, the mechanical behavior of rock mass is different. In excavation of slope and cave, most region of the rock mass is unloaded. Especially in a high steep slope or a large underground project, the larger the excavation and the dimension… 相似文献
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孟祥军 《中学英语园地(高三版)》2006,(Z1)
Have you heard of the earthquake(地震) of the Indian Ocean that happened 1 the last Sunday of 2004? About 300,000 people lost their lives in the earthquake. Do you know 2 in an earthquake? Let me 3 you.D uring a quake,ifyou are in a room ,you m ustget into the open air and stay away 4 buildings,trees,and 5 dangerous things.Y ou 6 stay in a door way 7 in a corner or get 8 a heavy desk or table. If you drive a car,a truck or a bus,you m ust drive it 9 the side of the road and stop.… 相似文献
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Investigations on the effects of W/C ratio and silica fume on the autogenous shrinkage and internal relative humidity of high performance concrete (HPC), and analysis of the self-desiccation mechanisms of HPC showed that the autogenous shrinkage and internal relative humidity of HPC increases and decreases with the reduction of W/C respectively; and that these phenomena were amplified by the addition of silica fume. Theoretical analyses indicated that the reduction of RH in HPC was not due to shortage of water, but due to the fact that the evaporable water in HPC was not evaporated freely. The reduction of internal relative humidity or the so-called self-desiccation of HPC was chiefly caused by the increase in mole concentration of soluble ions in HPC and the reduction of pore size or the increase in the fraction of micro-pore water in the total evaporable water (Tr/Tte ratio). 相似文献
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Yang Gao 《浙江大学学报(A卷英文版)》2010,11(10):835-840
This paper deals with the combination of point phonon and phason forces applied in the interior of infinite planes and half-planes of 1D quasicrystal bi-materials. Based on the general solution of quasicrystals, a series of displacement functions are adopted to obtain Green＇s functions for infinite planes and bi-material planes composed of two half-planes in the closed form, when the two half-planes are supposed to be ideally bonded or to be in smooth contact. Since the physical quantities can be readily calculated without the need of performing any transform operations, Green＇s functions are very convenient to be used in the study of point defects and inhomogeneities in the quasicrystal materials. 相似文献
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INTRODUCTION Regulation, handling and bioremediation of hazardous materials require an assessment of the risk to some living species other than human being, or assessment of hazard to the entire ecosystem. As- sessment endpoints are values of the ecosystem that are to be protected and are identified early in the analysis. Such endpoints may include life cycle stages of a species and reproductive or growth patterns. Ecosystem risk assessment is at its dawn with this area of environment sci… 相似文献
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Frame skipping in low bit video coding could significantly reduce the visual quality of reconstructed video. At the same time, if the complexity of the video sequence remains high for a long period, then driving up the long term average bit rate, the only resort of MPEG-4 Q2 rate control algorithm results in using a high quantization scale, which shows a poor visual quality of the reconstructed video. This paper analyzes the main causes of frame skipping in current MPEG-4 frame rate control scheme, and presents a new rate control algorithm based on the quadratic R-D model over a CBR channel. Key features of the present work are. 1) the bits allocated to each P-frame or B-frame are in proportion to its distance from the end of this GOP, i.e. more bits are allocated to the frames that are nearer to their reference Ⅰ -frame: 2) the target buffer level is changeable in the GOP, at the end of each GOP( five P-frames or B-frames), the target buffer level is linearly reduced from 1/2 to 1/4 of buffer size, to other frames, the target buffer level is set to 1/2 of buffer size: 3 ) a selective and judicious use of the reduced resolution mode, in addition to a modulation of the quantization scale parameter, is to control the average long term bit rate. Experimental results with different video sequences of varied complexity, encoded at low bit rates show better efficacy of the proposed algorithm than MPEG-4 Q2 rate control scheme, and the experimental results also show that the improved algorithm has significantly reduced the number of frame skipping, increased the overall PSNR, and improved the perceptual quality. 相似文献
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Yadolla Saeednia Mariani MD NOR 《美中教育评论》2010,7(5):94-100
Almost all schemes that have been issued by scholars or researchers to present Maslow＇s hierarchy of basic needs include a pyramid （triangle） in which the physiological needs are in the base and the self-actualization needs are in the top of the triangle. Although this scheming is inspiring to some results, basic needs have more characteristics that are significant however, this scheming is not able to inspire. Based on elaborating Maslow＇s theory and research＇s findings, this study aims to disclose weaknesses and strengths of traditional scheme （triangle）, and develop two innovated schemes of basic needs, which are more close to Maslow＇s ideas and more inspiring to realize the actuality of this hierarchy. 相似文献
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* In the separation operations of process industry,we often encounter some systems in which the relativevolatilities between components are close to one,or azeotropes are generated, and it is unreasonable ineconomy or unfeasible in technology that the conven-tional distillation is used to separate these systems. Ifthe azeotropic distillation is utilized for separatingthese mixtures, the knowledge about the compositionand boiling temperature of the azeotropes must be wellknown. The accurate pre… 相似文献
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利用酸性甲醛溶液将废弃花生壳改性,研究了改性花生壳对Cr（Ⅵ）浓度为50mg/L的模拟水样的静态吸附实验效果。实验结果表明,对于Cr（Ⅵ）浓度为50mg/L的50mL模拟水样,当温度为25℃用粒径为2-3mm改性花生壳吸附剂用量为1.0g、介质pH值为1.0、吸附时间为300min处理废水时,Cr（Ⅵ）的去除率可以达到99.71%。吸附后的水中Cr（Ⅵ）浓度为0.144mg/L,满足《污水综合排放标准》GB8978-1996的要求。改性花生壳比普通花生壳对废水中Cr（Ⅵ）的吸附能力更强。 相似文献
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利用柚子皮纤维素制备新型黄原酸酯(SCX),对废水中Cd2 进行吸附研究。通过对影响其吸附效果的SCX用量、Cd2 初始浓度、pH值、反应温度、吸附时间等因素进行吸附实验。结果表明:当废水中Cd2 初始浓度为15mg/L时,0.022gSCX对Cd2 去除率高达99.36%,其吸附容量达33.87mg/g,具有良好的吸附性。SCX对Cd2 的吸附符合Langmiur和Freundlich方程。 相似文献
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合成巯基纤维素(SC)对含铜(Ⅱ)废水的吸附研究 总被引：1，自引：0，他引：1
以柚子皮纤维素、硫代乙醇酸为基本原料,制备巯基纤维素(SC)新型吸附剂,用其对含Cu2 的溶液进行了静态吸附研究。本文探讨了Cu2 初始浓度、pH值、吸附时间、反应温度、吸附剂用量等因素对吸附性能的影响,结果表明:在pH为6.5、Cu2 浓度为100mg/L和吸附剂为0.2g时,常温条件下吸附2h后Cu2 去除率和吸附容量分别达到98.03%和24.5068mg/g,吸附反应符合Langmuir和Freundlich等温方程。 相似文献
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利用锯末半焦的吸附性能对亚甲基蓝溶液进行吸附实验,结果表明,pH为11,投加量为1.5g/L,温度40℃,吸附时间为60min,亚甲基蓝废水的初始浓度为15mg/L为吸附最佳条件.在此条件下锯末半焦具有良好的吸附效果,对亚甲基蓝的吸附行为符合Langmuir等温方程,脱色率可高达96.06％. 相似文献
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采用废弃花生壳对Cr（Ⅵ）浓度为50mg/L的模拟水样进行了静态吸附实验研究。实验结果表明,对于Cr（Ⅵ）浓度为50mg/L的50mL模拟水样,在25℃下,用粒径为2-3mm花生壳吸附剂用量为1.0g、介质pH值为1.0、吸附时间为300min处理废水时,Cr（Ⅵ）的去除率可以达到99.55%。吸附后的水中Cr（Ⅵ）浓度为0.224mg/L,满足《污水综合排放标准》GB8978-1996的标准。随着体系温度的升高,花生壳对Cr（Ⅵ）的吸附量增加,同时对吸附等温线及其模型的拟合进行了实验说明,Freundlich模型能较好地反映吸附过程特征。 相似文献
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通过对粉煤灰的硫酸改性得到酸改性粉煤灰,用其对含铅模拟废水进行吸附实验,探讨改性的最佳条件,并在最佳改性条件下制得改性粉煤灰,研究改性粉煤灰投加量、吸附时间、吸附温度以及pH值对Pb2＋吸附效果的影响.结果表明,在投加量为10 g/L,吸附时间为50 min,吸附温度为50℃,pH-6时,改性粉煤灰对40 μg/mL的Pb2＋的去除率可达90.34％,能够较好的去除废水中的Pb2＋. 相似文献
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选择盐泽螺旋藻进行培养,比较其在正常培养液与含亚甲基兰培养液中的生长曲线、叶绿素a含量以及对染料脱色率的不同.将悬浮藻和固定化藻加入到染料废水中,测定处理前后染料废水的吸光度,并计算脱色率.结果表明:固定化盐泽螺旋藻对染料废水的脱色率明显高于悬浮藻,实验数据显示了藻类的固定化提高了它的合成代谢活性. 相似文献
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对改性粉煤灰处理含铅废水进行了实验研究,结果表明,对铅离子的去除效果优于等量未改性粉煤灰和活性炭。吸附时间、废水的pH值、吸附剂用量、温度以及废水中Pb2＋浓度都能影响改性粉煤灰的吸附效果。最适宜的吸附条件是：在室温,pH=8．0,吸附剂用量为1．0g,Pb2＋含量小于0．005mol／L,吸附15min时,改性粉煤灰对废水中Pb2＋的吸附达到饱和。 相似文献
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铅铜离子对鲫鱼的急性毒性研究 总被引：2，自引：0，他引：2
分别用浓度为1．0,4．0,8．Omg／L的Cu^2＋溶液,浓度为1．0,4．0,8．0mg／L的Pb^2＋溶液以及Cu^2＋＋Pb^2＋的浓度（mg／L）为1．0＋1．0,4．0＋4．0,8．0＋8．0,8．0＋1．0,1．0＋8．0的混合溶液对鲫鱼进行急性染毒实验,在染毒24,48,72h后,分别取鲫鱼尾部血液制作血涂片,镜检并统计红细胞微核．结果显示,Cu^2＋,Pb^2＋不论是单一染毒,还是联合染毒,都能诱发鲫鱼红细胞产生较高频率的微核;Cu^2＋与Pb^2＋的联合染毒对鲫鱼的遗传毒性表现出协同作用,尤其是低浓度的Cu^2＋与Pb^2＋联合染毒效果最为明显;鲫鱼红细胞对Cu^2＋损伤后的修复能力明显好于Pb^2＋． 相似文献