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51.
Many control applications, including feedforward and learning control, involve the inverse of a dynamical system. For nonminimum-phase systems, the response of the inverse system is unbounded. For linear time-invariant (LTI), nonminimum-phase systems, a bounded, noncausal inverse response can be obtained through an exponential dichotomy. For generic linear time-varying (LTV) systems, such a dichotomy does not exist in general. The aim of this paper is to develop an inversion approach for an important class of LTV systems, namely linear periodically time-varying (LPTV) systems, which occur in, e.g. position-dependent systems with periodic tasks and non-equidistantly sampled systems. The proposed methodology exploits the periodicity to determine a bounded inverse for general LPTV systems. Conditions for existence are provided. The method is successfully demonstrated in several application cases, including position-dependent and non-equidistantly sampled systems. 相似文献
52.
张少平 《徐州工程学院学报》2009,(5)
林南的社会资本理论从理性选择出发,在行动与结构的互动、微观与宏观的连接、个体与整体的同构中,建立了强调差别、选择和建构,突出实践、社会网络和制度场域的具有鲜明观点的社会资本理论,突破了社会学方法论的二元对立困境,为社会学研究开辟了新的途径,成为一个新的解释范式。 相似文献
53.
提出以角度判别法对纸箱打样图形进行外轮廓识别,并介绍了识别多个外轮廓的算法步骤.同时,采用射线法识别外轮廓多边形中的内轮廓图形,为避免在判断过程的复杂运算,利用二分法对射线法进行了优化,并分析了算法的求解过程.相比传统的无序加工过程,外轮廓的识别功能提高了纸箱打样机的加工精度和加工效率. 相似文献
54.
Abstract Causality in changing natural systems can be seen to involve all four Aristotelian causal categories—material, efficient, formal and final. Final causality of materialistic origin can be found in the need to maintain energy flow continuity within dissipative systems. Each interacting dissipative system acts finalistically so as to attract needed energy. In so acting, it continually disturbs its neighborhood by generating potential energy flow disruptions as results of its activities. Final causality based, in this way, on the energy requirements of dissipative systems will generate formal causes as well. In contrast, the emergence of formal causes in mechanistic systems driven solely by efficient causes is extremely unlikely. We suggest viewing the subordination of phenotypic dissipative systems by genotypic counterparts as an historical example of the emergence of formal causes out of the material necessity of maintaining flow continuity. Functional separation between genotypic and phenotypic dissipative systems can occur if the energies to be dissipated are localized, as is the chemical binding energy of molecules with respect to biological functions at a higher scalar level. 相似文献
55.
Harlow Iain M.; MacKenzie Graham; Donaldson David I. 《Canadian Metallurgical Quarterly》2010,36(6):1381
Episodic recognition memory is mediated by functionally separable retrieval processes, notably familiarity (a general sense of prior exposure) and recollection (the retrieval of contextual details), whose relative engagement depends partly on the nature of the information being retrieved. Currently, the specific contribution of familiarity to associative recognition memory (where retrieval of the relationships between pairs of stimuli is required) is not clearly understood. In this study, we tested domain dichotomy theory, which predicts that familiarity should contribute more to associative memory when stimuli are similar (within-domain) than when they are distinct (between-domain). Participants studied stimulus pairs, and at test, discriminated intact from rearranged pairs. Stimuli were either within-domain (name–name or image–image pairs) or between-domain (name–image pairs). Across experiments we used 2 different behavioral measures of familiarity based on receiver operating characteristic curves and a modified remember–know procedure. Both experiments provided evidence that familiarity can contribute to associative recognition; however, familiarity was stronger for between-domain pairs, in direct contrast to the domain dichotomy prediction. (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
56.
57.
需求响应对配电网供电可靠性的影响 总被引:6,自引:1,他引:5
鉴于峰谷分时电价能够引导用户用电行为,促使用户积极参与到电力系统的削峰填谷行为中,而负荷与可靠性之间存在着复杂的非线性关系,文中重点研究了需求侧响应对配电网供电可靠性的影响。首先,建立分时电价优化模型:进行时段划分、确定电力价格弹性矩阵和制定各时段电价,再以峰负荷最小及峰谷负荷差最小确定多目标优化函数,考虑电网和电力市场基本约束条件建立分时电价优化模型;然后,在基于二分法的聚类负荷分析法中引入依据电力报价的负荷修正环节;最后,将不同负荷水平下的可靠性指标按持续时间进行加权平均,得到精确的可靠性指标。利用上述模型和方法,对改进的RBTS BUS6测试系统进行分时电价建模和可靠性评估。结果表明,需求响应策略改善了配电网的供电可靠性。 相似文献
58.
电缆沟敷设方式下电缆载流量计算及其影响因素分析 总被引:1,自引:0,他引:1
根据传热学的基本原理,利用有限单元自动划分法,建立了一种基于有限元法的电缆载流量计算模型,能按照实际敷设情况的变化对模型参数进行修改。根据电缆的结构参数和周围敷设区域的物性参数分析了电缆沟中电缆区域温度场分布情况,并提出基于二分法计算电缆载流量的方法。对比分析结果表明,相对于IEC60287中的热路法,该模型不仅计算结果准确,而且能更方便地考虑外界环境因素对电缆载流量的影响。通过实例仿真得出不同影响因素对电缆温度场分布的影响规律,并验证了该模型的准确性和可靠性。 相似文献
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60.
利用ABAQUS有限元程序,建立数值模型,模拟了分岔隧道不同洞段的开挖过程,分析了围岩变形与应力分布特点。基于数值分析,提出了针对不同洞段的支护形式。工程实例证明:这种支护形式有效地改善了围岩的应力分布,控制了围岩的变形。 相似文献