共查询到20条相似文献，搜索用时 82 毫秒
1.
WANG Chao GAO Peng ZHANG Xue-song SHAO Wei 《浙江大学学报(A卷英文版)》2007,8(8):1340-1345
In this paper,two new concepts—“main out-of-step mode” and “minor out-of-step mode”—are proposed for power system reliability analysis. Large-scale power system studies found that out-of-step generator groups may have characteristics of the main out-of-step mode and the minor out-of-step mode. The generator groups with main out-of-step modes can determine the out-of-step interface of the large-scale power system,while generators with the minor out-of-step modes cannot play such a role. Therefore,the method of capturing the out-of-step interface by seeking the lowest voltage point(the out-of-step center) can only group the generators with the main out-of-step modes,and may fail to combine the generators with the minor out-of-step modes into proper coherent generator groups. Thus,it is necessary in engineering applications to equip the generators that are likely to have the characteristics of the minor out-of-step modes with separation devices based on off-line simulation studies in order to reduce the risk of further accidents caused by these generators after system separation. 相似文献
2.
基于被删减二元关系的可达性矩阵求解 总被引：1，自引：0，他引：1
利用邻接矩阵求解有向图的可达性矩阵,计算量大,提出将有向图表达成二元关系,忽略环和回路的处理,通过计算被删减二元关系的传递闭包来求解可达性矩阵,利用新方法可以较快地实现可达性矩阵的求解。 相似文献
3.
In civil engineering, the nonlinear dynamic instability of structures occurs at a bifurcation point or a limit point. The instability at a bifurcation point can be analyzed with the theory of nonlinear dynamics, and that at a limit point can be discussed with the theory of elastoplasticity. In this paper, the nonlinear dynamic instability of structures was treated with mathematical and mechanical theories. The research methods for the problems of structural nonlinear dynamic stability were discussed first, and then the criterion of stability or instability of structures, the method to obtain the bifurcation point and the limit point, and the formulae of the directions of the branch solutions at a bifurcation point were elucidated. These methods can be applied to the problems of nonlinear dynamic instability of structures such as reticulated shells, space grid structures, and so on. 相似文献
4.
In civil engineering, the nonlinear dynamic instability of structures occurs at a bifurcation point or a limit point. The instability at a bifurcation point can be analyzed with the theory of nonlinear dynamics, and that at a limit point can be discussed with the theory of elastoplasticity. In this paper, the nonlinear dynamic instability of structures was treated with mathematical and mechanical theories.The research methods for the problems of structural nonlinear dynamic stability were discussed first, and then the criterion of stability or instability of structures, the method to obtain the bifurcation point and the limit point, and the formulae of the directions of the branch solutions at a bifurcation point were elucidated. These methods can be applied to the problems of nonlinear dynamic instability of structures such as reticulated shells, space grid structures, and so on. 相似文献
5.
The symplectic approach proposed and developed by Zhong et al. in 1990s for elasticity problems is a rational analytical method, in which ample experience is not needed as in the conventional semi-inverse method. In the symplectic space, elasticity problems can be solved using the method of separation of variables along with the eigenfunction expansion technique, as in traditional Fourier analysis. The eigensolutions include those corresponding to zero and nonzero eigenvalues. The latter group can be further divided into α-and β-sets. This paper reformulates the form of β-set eigensolutions to achieve the stability of numerical calculation, which is very important to obtain accurate results within the symplectic frame. An example is finally given and numerical results are compared and discussed. 相似文献
6.
城市公园作为居民的主要活动游憩场所,对于现代社会有重要的意义.公园本身能否让游客容易快捷地进入,是除了公园面积、个数之外的重要评价指标.基于GIS以及AHP评价方法的公园可达性分析,能够合理客观的评价福州市城市公园在空间位置上的可达性以及城市居民心理上可达性,为合理的规划城市提供参考方法及理论依据.结果表明：福州市的各公园分布较为合理,大部分具有良好的可达性,但仍然存在一定区域的服务空白;相较直接划分公园的服务范围,加权泰森多边形能够更好的反映福州公园的可达性. 相似文献
7.
考虑太阳能吸收能量的混沌特性和递归小波网络学习能力强、动态适应性强的优点,提出采用相空间重构与递归小波网络结合的预测模型。分别用该模型与未进行相空间重构、普通递归网络等模型分析实测数据比较,发现采用相空间重构后数据进行模型训练与预测对各种天气、环境的适应性强;而且预测间隔越短,计算量降低的效果越明显;当预测间隔为1.25 min时,计算量降低25%以上。此外,该模型具有相对简单、需要历史数据少、存储空间少的优点,而且预测精度高。 相似文献
8.
The security constrained distributed optimal power flow (DOPF) of interconnected power systems is presented. The centralized OPF problem of the multi-area power systems is decomposed into independent DOPF subproblems, one for each area. The dynamic security region (DSR) to guarantee the transient stability constraints and static voltage stability region (SVSR) constraints, and line current limits are included as constraints. The solutions to the DOPF subproblems of the different areas are coordinated through a pricing mechanism until they converge to the centralized OPF solution. The nonlinear DOPF subproblem is solved by predictor-corrector interior point method (PCIPM). The IEEE three-area RTS-96 system is worked out in order to demonstrate the effectiveness of the proposed method. 相似文献
9.
邓慧琼王璜 《福建工程学院学报》2017,(1):39-43
针对电网潮流转移场景下支路传输功率和电网节点注入功率之间的关联作用关系,提出了一种分析节点注入功率模式的方法。根据支路传输功率和电网节点注入功率之间的关联作用关系矩阵,利用矩阵奇异值分解,将节点注入功率分解为各种模式;在此基础上,进一步分析节点注入功率的各种模式的表现形式并进行算例分析。算例分析初步表明,在节点注入功率模式的各种表现形式中,比较常见的是以部分奇异值为主导的作用模式,在实际分析和处理中,把握这样的主导模式,将有利于进一步的分析和预防潮流转移引起的不利后果。 相似文献
10.
研究共振条件下的一类椭圆边值问题,利用临界点理论中的Morse理论方法,通过计算零点和无穷远处的临界群,根据Morse不等式,得到该方程两个非零解的存在性. 相似文献
11.
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
12.
为了研究Ad Hoc网络中的按需路由协议的性能,基于NS2仿真平台,研究分析了移动速度对两种典型按需路由协议AODV和DSR的性能影响,并对DSR协议进行了改进.性能参数包括分组投递率、端到端的平均时延、路由发起率、归一化路由开销等性能.仿真结果表明,DSR协议在移动环境下的性能较好,并且改进后的DSR协议在分组投递率、端到端时延方面均优于原DSR协议. 相似文献
13.
The symplectic approach proposed and developed by Zhong et al. in 1990s for elasticity problems is a rational analytical method, in which ample experience is not needed as in the conventional semi-inverse method. In the symplectic space, elasticity problems can be solved using the method of separation of variables along with the eigenfunction expansion technique, as in traditional Fourier analysis. The eigensolutions include those corresponding to zero and nonzero eigenvalues, The latter group can be further divided into α- and β-sets. This paper reformulates the form of β-set eigensolutions to achieve the stability of numerical calculation, which is very important to obtain accurate results within the symplectic frame. An example is finally given and numerical results are compared and discussed. 相似文献
14.
Using Baire metric, this paper proposes a generalized framework of transition system approximation by developing the notions of approximate reachability and approximate bisimulation equivalences. The proposed framework captures the traditional exact equivalence as a special case. Approximate reachability equivalence is coarser than approximate bisimulation equivalence, just like the hierarchy of the exact ones. Both approximate equivalences satisfy the transitive property, consequently, they can be used in transition system approximation. 相似文献
15.
A novel single-channel blind separation algorithm for permuted motion blurred images is proposed by using blind restoration
in this paper. Both the motion direction and the length of the point spread function (PSF) are estimated by Radon transformation
and extrema a detection. Using the estimated blur parameters, the permuted image is restored by performing the L-R blind restoration
method. The permutation mixing matrices can be accurately estimated by classifying the ringing effect in the restored image,
thereby the source images can be separated. Simulation results show a better separation efficiency for the permuted motion
blurred image with various permutation operations. The proposed algorithm indicates a better performance on the robustness
against Gaussian noise and lossy JPEG compression. 相似文献
16.
根据卤代甲烷临界温度的变化规律,探讨了卤代甲烷的临界温度与其分子结构之间的关系,发展了一种既能计算卤代甲烷临界温度,又能预测未知卤代甲烷临界温度的方法,结果表明,临界温度计算值与实验值的一致性令人满意,平均误差为０．３９５％。 相似文献
17.
黄家满 《晋城职业技术学院学报》2020,13(2):78-81,89
预计参数反演是利用概率积分法预计煤矿开采后地表移动与变形的关键。总结分析了预计参数反演的最小二乘法、模式法和遗传算法,利用Matlab软件中的最优化算法工具箱,在缓倾斜煤层非充分开采条件下,对3种反演方法的计算结果进行比较。结果表明,最小二乘法计算结果准确性较好,但初始点选择不当会导致计算失败;模式法和遗传算法都无需计算函数的梯度信息,遗传算法的初值是种群,其计算结果比模式法更加准确;在各参数中,开采影响传播角θ的误差较大,通过采用遗传算法工具箱和fminbnd函数联合走向断面和倾向断面的数据进行反演,可以提高预计参数的准确性。 相似文献
18.
张变莲 《西安文理学院学报》2009,12(4):55-58
针对三维重建技术的需要,提出一种基于SUSAN角点匹配的技术,实现了对多视角二维图像的精确匹配定位.该技术首先利用了相关匹配技术,对多幅图像中的相似区域进行粗略定位,再在该粗略区域内,分别提取SUSAN角点的位置,各视角图像中的角点均对应于空间的同一点.实验证明,该技术可以有效地计算出空间特征点的位置. 相似文献
19.
针对异步电动机直接转矩控制（DTC）系统在低速时由于开关频率不稳定而引起转矩脉动较大的缺点，提出了一种预测控制方法。该方法根据转矩和定子磁链的误差来确定应该施加的参考电压矢量，最后利用空间矢量脉宽调制（SVPWM）方法来合成该矢量，这样即保证了逆变器的开关频率恒定，从而大大降低转矩脉动。仿真结果表明，在低速下定子磁链轨迹近似为圆，转矩脉动不明显。 相似文献
20.
利用传输矩阵方法研究了多个周期性分布的负折射率缺陷的一维光子晶体的透射谱.以32个周期的1/4波堆存在5个负折射率缺陷的光子晶体为例进行了数值计算.结果表明:在带隙中产生多个缺陷模,这些缺陷模的分布依赖于缺陷在晶体中的分布.当缺陷密集时,缺陷耦合较强,缺陷模相距较远;当缺陷稀疏时,缺陷耦合较弱,缺陷模相距较近,分立的缺陷模趋于简并,由此形成一个很窄的通带.与正折射率缺陷情形相比较,负折射率缺陷间的相互作用对缺陷模的影响更大,缺陷模谱线也更宽. 相似文献