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111.
112.
汪达成 《重庆交通大学学报(自然科学版)》2005,24(2):151-152,160
建立了一个新的极大极小不等式,并利用它研究了仿紧集上一类新型广义双拟变分不等式解的存在性问题. 相似文献
113.
Spillback congestion in dynamic traffic assignment: A macroscopic flow model with time-varying bottlenecks 总被引:1,自引:0,他引:1
Guido Gentile Lorenzo Meschini Natale Papola 《Transportation Research Part B: Methodological》2007,41(10):1114-1138
In this paper, we propose a new model for the within-day Dynamic Traffic Assignment (DTA) on road networks where the simulation of queue spillovers is explicitly addressed, and a user equilibrium is expressed as a fixed-point problem in terms of arc flow temporal profiles, i.e., in the infinite dimension space of time’s functions. The model integrates spillback congestion into an existing formulation of the DTA based on continuous-time variables and implicit path enumeration, which is capable of explicitly representing the formation and dispersion of vehicle queues on road links, but allows them to exceed the arc length. The propagation of congestion among adjacent arcs will be achieved through the introduction of time-varying exit and entry capacities that limit the inflow on downstream arcs in such a way that their storage capacities are never exceeded. Determining the temporal profile of these capacity constraints requires solving a system of spatially non-separable macroscopic flow models on the supply side of the DTA based on the theory of kinematic waves, which describe the dynamic of the spillback phenomenon and yield consistent network performances for given arc flows. We also devise a numerical solution algorithm of the proposed continuous-time formulation allowing for “long time intervals” of several minutes, and give an empirical evidence of its convergence. Finally, we carry out a thorough experimentation in order to estimate the relevance of spillback modeling in the context of the DTA, compare the proposed model in terms of effectiveness with the Cell Transmission Model, and assess the efficiency of the proposed algorithm and its applicability to real instances with large networks. 相似文献
114.
115.
考虑锈蚀影响的拉索状态UL列式分析法 总被引:1,自引:0,他引:1
针对拉索在服役期间经常出现的钢丝锈蚀及索力松弛病害现象,通过求解拉索微分方程边值问题及讨论索的收敛迭代解,引入Lemaitre的疲劳损伤应变等价原理和几何损伤理论,提出了在工程中拉索的锈蚀程度可通过适当折减拉索材料的弹性模量来表征,在此基础上,建立了计入拉索锈蚀和索力松弛影响的拉索状态UL列式分析方法,并成功运用到实际工程的拉索状态分析中。研究和工程实践表明拉索的锈蚀和索力松弛在服役期间拉索结构状态分析中不容忽视。所提供的方法,考虑了拉索锈蚀及索力松弛病害影响,为大跨度斜拉桥服役期间拉索状态较为精确的非线性分析提供了重要依据。 相似文献
116.
施闻明 《船舶与海洋工程学报》2010,9(1):105-108
The accuracy of parameter estimation is critical when digitally modeling a ship. A parameter estimation method with constraints
was developed, based on the variational method. Performance functions and constraint equations in the variational method are
constructed by analyzing input and output equations of the system. The problem of parameter estimation was transformed into
a problem of least squares estimation. The parameter estimation equation was analyzed in order to get an optimized estimation
of parameters based on the Lagrange multiplication operator. Simulation results showed that this method is better than the
traditional least squares estimation, producing a higher precision when identifying parameters. It has very important practical
value in areas of application such as system identification and parameter estimation. 相似文献
117.
结构构件在外荷载的作用下,其材料逐渐衰变,表现出损伤演化进而最后失效的行
为,描述这一行为的损伤本构关系非常复杂并且有高度的非线性;本文基于连续损伤
力学(。ntinuuln压甘以seMechan油),提出用于结构损伤失效分析的数值原理,包括损
伤模型、失效准则、结构分析变分原理及相应的有限元列式;涉及到具有损伤翔合的
弹塑性问题及蠕变问题. 相似文献
118.
Sarah Harper Charlotte Grubb Margot Stiles Ussif Rashid Sumaila 《Coastal management》2017,45(2):91-106
The contribution by women to fisheries economies globally continues to be overlooked, in part, because “fishing” is often narrowly defined as catching fish at sea, from a vessel, using specialized gears. Both men and women are involved in fisheries, but often in different roles and activities. Fisheries research, management, and policy have traditionally focused on direct, formal, and paid fishing activities—that are often dominated by men, ignoring those that are indirect, informal, and/or unpaid—where women are concentrated. This has led to a situation where men's and women's contributions to fisheries are not equally valued or even recognized and has resulted in women being largely excluded from fisheries decision-making processes. Here, we examine the contributions by women in the fisheries sector of five globally significant marine fishing countries—Mexico, Peru, Senegal, South Africa, and Vietnam. These countries each have strong links between livelihoods and marine capture fisheries, yet represent different geographic, socioeconomic, and governance contexts. Through a synthesis of existing data, case studies, and consultation with local experts, we found that the contribution by women to the fisheries of these five countries is substantial. However, this investigation also revealed major gaps in understanding of gender inequalities in the fisheries sector and the need for better gender-disaggregated data to inform fisheries policy. 相似文献
119.
应用两个已知的几何不等式与反演变换,建立了一个强于Bottema不等式的新结果,给出了新结果的几个推论,指出了一个有趣的极值问题的结论,提出了一个未解决的问题与一个猜想. 相似文献
120.
离散系统动力学的位移变分原理 总被引:2,自引:1,他引:1
通过对位移、功、势能和虚位移、虚功等概念的阐述,用变积运算定义了瞬时势能,然后用变积法从达朗贝尔-拉格朗日原理导出位移变分原理。该原理是势能驻值定理在动力学中的发展,也是达朗贝尔-拉格朗日原理的延伸,使动力学问题得到简化。 相似文献