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421.
半正Neumann边值问题的解和正解的存在性与多解性 总被引:9,自引:0,他引:9
利用锥拉伸与锥压缩型的Krasnosel'skii不动点定理考察了一类非线性Neumann边值问题的解和正解,其中允许非线性项有非正的下界.研究表明,只要非线性项在某些有界集上的最大高度和最小高度是适当的,这个问题便具有n(n为任意自然数)个解或者正解. 相似文献
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The nickel ore slurry sloshing in a rolling partially loaded prismatic cargo hold with a longitudinal baffle is investigated. A numerical model based on the volume of fluid (VOF) method and the non-Newtonian Herschel-Bulkley and Bingham equations is proposed to study the dynamic behavior of nickel ore slurry sloshing. The numerical model is solved by using the finite volume approximations and the dynamic mesh technique is utilized to handle the cargo hold's motion. After taking grid and time step independence study, the numerical results are compared with experimental data. Comparisons show good agreement in the cases investigated. Further, the relationship between the moment amplitude induced on the hold boundary and the excitation frequency is checked numerically. The ratio of baffle height to the initial cargo depth has been changed in the range of 0.0 ≤ hB/d ≤ 1.2. The variation of the sloshing-induced moment and the deformation of the free surface under different baffle heights have been obtained and discussed. To clearly understand the sloshing behavior of nickel ore slurry, the sloshing of liquid water has also been carried out. Meanwhile, the dynamic viscosity of the nickel ore slurry is monitored. The critical baffle height with regard to the sloshing-induced moment and the elevation difference of the free surface at two sides of the cargo hold has also been presented and discussed. 相似文献
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客运交通价格是实现城市客运交通资源优化整合的关键要素,文中基于交通调查和统计分析得出影响城市客运价格联动的因素,将结构方程模型运用到交通运输经济方面,构建了城市客运交通价格联动的结构方程模型.选取经济水平、服务水平、交通需求作为外生变量;以公交价格,地铁价格和出租车价格为内生变量,重点分析了经济水平、服务水平和交通需求对3种客运价格的影响关系和各类客运价格之间的关联性.结果表明经济水平和服务水平对于3种客运价格有显著影响. 相似文献
427.
采用计算流体力学与声学边界元方法相结合求解了潜艇尾部大侧斜螺旋桨的直接辐射噪声.与一般螺旋桨噪声计算不同的是,螺旋桨非定常计算时引入了潜艇尾部桨盘面的速度分布作为非均匀来流,能够提供更加真实的螺旋桨脉动压力源场.提取桨叶表面的声偶极源项后,采用边界元方法,求解FW-H方程,得到了螺旋桨空间测点的声压谱和总声级.桨盘面速度分布由全附体潜艇粘性流场数值计算得到,其可信性由艇体表面的压力系数与试验值的比较给予了验证.螺旋桨数值模型的可信性由敞水特性预报值与试验值的比较进行了验证. 相似文献
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The accuracy of travel time information given to passengers plays a key role in the success of any Advanced Public Transportation Systems (APTS) application. In order to improve the accuracy of such applications, one should carefully develop a prediction method. A majority of the available prediction methods considered the variation in travel time either spatially or temporally. The present study developed a prediction method that considers both temporal and spatial variations in travel time. The conservation of vehicles equation in terms of flow and density was first re-written in terms of speed in the form of a partial differential equation using traffic stream models. Then, the developed speed based equation was discretized using the Godunov scheme and used in the prediction scheme that was based on the Kalman filter. From the results, it was found that the proposed method was able to perform better than historical average, regression, and ANN methods and the methods that considered either temporal or spatial variations alone. Finally, a formulation was developed to check the effect of side roads on prediction accuracy and it was found that the additional requirement in terms of location based data did not result in an appreciable change in the prediction accuracy. This clearly demonstrated that the proposed approach based on using vehicle tracking data is good enough for the considered application of bus travel time prediction. 相似文献
430.
Growing concerns over climate change have led to an increasing interest in the role of the built environment to reduce transportation greenhouse gas (GHG) emissions. Many studies have reported that compact, mixed-use, and well-connected developments reduce vehicle miles traveled (VMT). Others, however, argue that densification and mixture of land uses can slow down vehicle movements, and consequently generate more driving emissions. Methodologically, VMT is only a proxy, not an exact measure of emissions. This study quantifies the net effects of the built environment on household vehicle emissions through a case study of Austin, TX. The study employed structural equation modeling (SEM) techniques and estimated path models to improve understanding of the relationship between the built environment and vehicle emissions. The results show a rather complex picture of the relationship. Densification can reduce regional vehicle emissions despite its secondary effect of reduced vehicle travel speed. A 1% increase in density was found to reduce household vehicle emissions by 0.1%. However, intensification of the design feature of the built environment in developed areas may work in the opposite direction; the modeling results showed a 1% increase in grid-like network being associated with 0.8% increase in household vehicle emissions. Based on the results, the study addressed the potential of and the challenges to reducing vehicle emissions through modifying the built environment in local areas. 相似文献