共查询到20条相似文献，搜索用时 31 毫秒
1.
文忠宇 《楚雄师范学院学报》2003,18(3):91-93,100
本文用1961—2002年楚雄州10个站逐日雨量资料及历史天气图，统计分析了楚雄州暴雨的时空分布特征，得到的结果在暴雨预报及防灾减灾及气候区划方面有一定的参考价值。 相似文献
2.
李跃 《昆明师范高等专科学校学报》2009,31(6):86-87,91
应用常规动态理论对重型车辆系统进行探测和跟踪过程的解析分析,把重型车辆系统的动态方程变为一个广义和常规的基于基本特征参数、自然频率、阻尼系数并考虑了外部干扰的非线性二阶动态系统．解析解法是对过去一直在重型车辆系统上所做的时域和频域函数分析方法的完善和补充,它们提供了大量快速的规范和定量分析模式,并决定着动态重型车辆系统研究的质量和特性． 相似文献
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Phosphorus transport with runoff of simulated rainfall from purple-soil cropland of different surface conditions 总被引：5，自引：0，他引：5
We investigated the patterns of phosphorus transport from purple-soil cropland of 5° and 10° slopes with bare and vegetated surfaces, respectively. Each type of land was tested under a simulated moderate rainfall of 0.33 mm/min, a downfall of 0.90 mm/min, and a rainstorm of 1.86 mm/min. Runoff dynamics and changes in the export amount of phosphorus are influenced by the rainfall intensity, the slope and surface conditions of cropland. The vegetation diverts rain water from the surface into soil and helps the formation of a subsurface runoff, but has little influence on runoff process at the same sloping degree. Vegetated soil has a smaller phosphorous loss, particularly much less in the particulate form. A heavier rainfall flushes away more phosphorous. Rainwater percolating soil carries more dissolved phosphorous than particulate phosphorous. Understanding the patterns of phosphorous transport under various conditions from purple soil in the middle of Sichuan basin is helpful for developing countermeasures against non-point-source pollution resulting in the eutrophication of water bodies in this region that could, if not controlled properly, deteriorate the water quality of the Three Gorges Reservoir. 相似文献
4.
ZHANG Ri-dong WANG Shu-qing 《浙江大学学报(A卷英文版)》2006,7(12):1984-1988
INTRODUCTION Bilinear systems are a kind of important nonlinear systems with relatively simple structure, and many industrial processes can be described as a bilinear system. Thus research on the control of this kind of systems is very important. On the other hand, model predictive control (MPC) (Clarke et al., 1987) has been widely used in industrial applications and many predictive control methods focusing on bilinear systems are emerging (Bloemen et al., 2001; Fontes et al., 2004; He… 相似文献
5.
为了实现屋面雨水利用系统量化评估中径流系数的精确取值,通过连续3年(2010—2012年)对河北省邯郸市不同屋面类型(屋面坡度和材料)及降雨特征(降雨深度和强度)的屋面径流进行实地监测,得到了各场实际降雨屋面径流系数的不同取值.研究结果表明,屋面径流系数的取值分布与各降雨事件的降雨深度相关性较强,其他影响因素对其影响较小.场次径流系数的取值与降雨深度呈显著的分段线性关系.根据1960—2008年的日降雨数据资料,计算得出邯郸市年均屋面径流系数可近似按照0.62这一常数进行取值.该研究成果可用于屋面雨水利用系统的量化评估及运行分析. 相似文献
6.
王建亚 《泰州职业技术学院学报》2004,4(1):7-11
讨论了部分电视发射机的非线性指标及其测试方法，如互调、微分增益、微分相位、亮度非线性等，指出了实践中存在的问题和应当注意的方面。 相似文献
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梅州地区花岗岩残积土分布广泛,花岗岩残积土滑坡是威胁建筑安全的主要地质灾害,滑坡稳定性评价方法历来是工程地质领域的研究热点.针对这一问题,以梅州大埔某残积土滑坡为例,对该滑坡的土体进行了直接快速剪切试验,获得其强度指标,残积土试样浸水后抗剪强度降低,主要是粘聚力的减小,内摩擦角降幅很小.利用Slide滑坡稳定性计算软件对天然工况、降雨条件、地震条件下的稳定性进行评价.稳定性结果分别为1.101、1.040和1.039,稳定性差. 相似文献
9.
The fracture processes of concrete were described by a cohesive crack model based on initial toughness criterion. The corresponding analytical method to predict the instability state was proposed. In this model, the initial toughness was adopted as the crack propagation criterion and the weight function method was used to calculate the stress intensity factor and the crack opening displacement caused by the cohesive stress. The unstable toughness can be easily obtained using the proposed method without measuring parameters at the critical state that was necessary in traditional methods. The proposed method was verified by existing experimental data of wedge splitting specimens with different grades of concrete and the sensitivity of the results on the tensile softening curve was discussed. The results demonstrate that the proposed method can well predict the peak load, the critical effective crack length, and the unstable toughness of concrete specimens. Moreover, the calculated unstable toughness is not sensitive to the tensile softening curve. 相似文献
10.
Ratna Nandakumar 《Journal of Educational Measurement》1994,31(1):17-35
This study compares the performance of three methodologies for assessing unidi-mensionality: DIMTEST, Holland and Rosenbaum's approach, and nonlinear factor analysis. Each method is examined and compared with other methods on simulated and real data sets. Seven data sets, all with 2,000 examinees, were generated: three unidimensional and four two-dimensional data sets. Two levels of correlation between abilities were considered:ρ= 3 and ρ= . 7. Eight different real data sets were used: Four of them were expected to be unidimensional, and the other four were expected to be two-dimensional. Findings suggest that all three methods correctly confirmed unidimensionality but differed in their ability to detect lack of unidimensionality. DIMTEST showed excellent power in detecting lack of unidimensionality; Holland and Rosenbaum's and nonlinear factor analysis approaches showed good power, provided the correlation between abilities was low. 相似文献
11.
利用同伦分析法求解了耦合非线性方程组,得到的近似解与其他方法得到的精确解十分吻合.结果表明这种方法是求解非线性问题的一种更行之有效的方法,可以更广泛地应用于求解其他的非线性问题. 相似文献
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Thebasicstressvariablesintheconstitutivemodelde velopedbyAlonsoetal[5] aresoilnetstressandsoilmatricsuctions ,whicharedefinedby σ″ =σ -ua (1) s=ua-uw (2 )whereσisthetotalstress,uwistheporewaterpressureanduaistheporeairpressure . Thenetmeanstresspanddeviatoricstressqarede finedas p =σ1+2σ33-ua (3) q =σ1-σ3(4 ) Asgenerallyregarded ,thesoilsuctioniscomposedoftwoparts ,matricsuctionandosmosissuction .TheosmosissuctionisneglectedoriginallyinAlonsoetal′smodelandhe… 相似文献
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The explosion inside tunnel would generate blast wave which transmits through the longitudinal tunnel. Because of the close-in effects of the tunnel and the reflection by the confining tunnel structure, blast wave propagation inside tunnel is distinguished from that in air. When the explosion happens inside tunnel, the overpressure peak is higher than that of explosion happening in air. The continuance time of the blast wave also becomes longer. With the help of the numerical simulation finite element software LS-DYNA, a three-dimensional nonlinear dynamic simulation analysis for an explosion experiment inside tunnel was carried out. LS-DYNA is a fully integrated analysis program specifically designed for nonlinear dynamics and large strain problems. Compared with the experimental results, the simulation results have made the material parameters of numerical simulation model available. By using the model and the same material parameters, many results were adopted by calculating the model under different TNT explosion dynamites. Then the method of dimensional analysis was used for the simulation results. As overpressures of the explosion blast wave are the governing factor in the tunnel responses, a formula for the explosion blast wave over-pressure at a certain distance from the detonation center point inside the tunnel was derived by using the dimensional analysis theory. By comparing the results computed by the formula with experimental results which were obtained before, the formula was proved to be very applicable at some instance. The research may be helpful to estimate rapidly the effect of internal explosion of tunnel on the structure. 相似文献
14.
借鉴遗传算法中的杂交概念,将其引入标准粒子群方法(Particle Swarm Optimization, PSO),形成混合粒子群算法(MPSO).该方法改善了PSO方法的全局搜索能力,提高了算法的收敛速度和计算精度,并用其计算可靠度指标及相应的验算点.以典型的边坡为例,通过工程算例并与其他方法对比,表明了MPSO方法较标准PSO方法的计算精度高,收敛速度快;分析了算法中各控制参数对可靠度指标的影响;算例结果表明:MPSO方法对求解功能函数呈高度非线性的边坡可靠性问题具有很好的适应性,是科学可行的,具有很好的应用前景. 相似文献
15.
WANG Yong HUANG Qi-bai ZHOU Ming-gang XIE Shou-yong 《重庆大学学报(英文版)》2006,5(3):125-130
1 Introduction ? Low frequency vibration has an important effect on body comfort and on the fatigue of a vibrating system. Nearly all actual vibrating systems are nonlinear. However, nonlinear behaviors are not always observed in the system dynamics. Thus… 相似文献
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１ Ｉｎｔｒｏｄｕｃｔｉｏｎ Ｔｈｅａｄａｐｔｉｖｅｆｕｚｚｙｃｏｎｔｒｏｌｉｓａｓｕｃｃｅｓｆｕｌｉｓｓｕｅｏｆｔｈｅｆｕｚｚｙｃｏｎｔｒｏｌ．Ｔｈｅａｄａｐｔｉｖｅｆｕｚｚｙｃｏｎｔｒｏｌｏｆｏｎｌｉｎｅｌｅａｒｎｉｎｇａｎｄｏｎｌｉｎｅｃｏｎｔｒｏｌｉｓｔｈｅｏｒｉｅｎｔａｔｉｏｎｏｆｔｈｅｄｅｖｅｌｏｐｍｅｎｔｉｎｔｈｅａｄａｐｔｉｖｅｆｕｚｚｙｃｏｎｔｒｏｌｆｉｅｌｄ．Ｂｕｔｔｈｅｃｏｍｐｌｅｘｏｆｔｈｅｐｌａｎｔｓｕｃｈａｓｓｔｒｏｎｇｃｏｕｐｌｅｄｒｅｌａｔｉｏｎｓ,ｌｏｎｇ… 相似文献
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Alternate path(AP) method is the most widely used method for the progressive collapse analysis,and its application in frame structures has been well proved.However,the application of AP method for other structures,especially for cable-stayed structures,should be further developed.The four analytical procedures,i.e.,linear static,nonlinear static,linear dynamic,and nonlinear dynamic were firstly improved by taking into account the initial state.Then a cable-stayed structure was studied using the four improved methods.Furthermore,the losses of both one cable and two cables were discussed.The results show that for static and dynamic analyses of the cable-stayed bridges,there is large difference between the results obtained from simulations starting with either a deformed or a nondeformed configuration at the time of cable loss.The static results are conservative in the vicinity of the ruptured cable,but the dynamic effect of the cable loss in the area farther away from the loss-cable cannot be considered.Moreover,the dynamic amplification factor of 2.0 is found to be a good estimate for static analysis procedures,since linear static and linear dynamic procedures yield approximately the same maximum vertical deflection.The results of the comprehensive evaluation of the cable failure show that the tread of the progressive failure of the cable-stayed bridges decreases when the location of the failed cables is closer to the pylon. 相似文献
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给出了横向磁场作用下矩形薄板的磁弹性振动方程,针对一边固定、三边简支的矩形薄板,通过位移模态展开,并利用Galerkin法得到两自由度内共振非线性振动微分方程组。算例分析中,利用数值方法得到了系统内共振时两阶模态的时间历程响应图和相平面图,并分别讨论了系统初值及磁场强度对系统振动的影响。结果表明,系统呈现明显的非线性内共振特征。 相似文献
19.
Parameter estimation of cutting tool temperature nonlinear model using PSO algorithm 总被引：2，自引：0，他引：2
INTRODUCTION In modern metal cutting theory,research on cutting tool is one of the major concerns.To under-stand the characteristics of a new cutting tool,many experiments(such as cutting force experiment,cut-ting temperature experiment,anti-striking experiment,etc.)should be conducted to obtain an enormous amount of experiment data.The development of a proper cutting tool temperature model is a very dif-ficult task due to the large number of interrelated parameters(cutting speed,feed,dept… 相似文献