Order Reduction of Power Systems by Modal Truncated Balanced Realization

In this paper, a general approach for constructing reduced-order models of power system models based on a truncated balanced realization (TBR) linear reduction procedure is described. The method enables efficient computation of Gramian covariance matrices in terms of the system frequency response, and it can be used for control design and sensitivity analysis. The method guarantees convergence of the controllability and observability Gramians and avoids the need for frequency sweep of the transfer function matrix. A key innovation for the TBR-based reduced-order models introduced in this paper is the use of modal information to approximate the controllability and observability Gramians. With this approach, the connection between the linear system modes and the Gramians is clarified, and the contribution of critical system motion modes to the collective dynamics is readily determined. Conditions for convergence of the model and approximation methods are then investigated, and the issues of accuracy, applicability, and computational effort are discussed. The technique is tested on two real-world test power systems.     

麦克斯韦方程和波动方程的唯一延拓定理

研究了麦克斯韦方程和波动方程的唯一延拓性质。用卡勒曼估计方法获得了波动方程的唯一延拓,用积分变换方法导出了麦克斯韦方程唯一延拓,利用所获得的唯一延拓性导出了半线性波动方程的能控性。所得结果具有较重要的理论意义。     

定向碳纳米管薄膜的制备及可控浸润性

利用热化学气相沉积系统(CVD),用乙炔为碳源,氮气为载气,氢气为还原气体,氨气为刻蚀气体,在单晶硅上制备定向碳纳米管薄膜.通过扫描电镜(SEM)观察不同反应温度对碳纳米管薄膜的形貌影响,并通过接触角测量仪评估薄膜的浸润性.结果表明,生长温度对碳纳米管薄膜的定向性程度及其尺度有很大的影响,温度太低不利于定向碳纳米管的形成,太高也会阻碍定向生长,适合定向碳纳米管生长的温度在850℃左右;通过生长温度改变碳纳米管薄膜的表面微观形貌就可以大幅度地调控其表面的浸润性能,从亲水79.9°到超疏水155.4°.碳纳米管的定向程度、尺寸和浸润性等特性可以用生长温度来加以调控.     

Critical subway stations identification for passenger flow control by applying network controllability

ABSTRACT

Passenger flow control on a limited number of stations is a common way to maintain the service of a subway system at a desired level. Critical subway stations identification is the key for controlling a complex subway system. Based on network controllability analysis, this paper proposes a passenger flow network (PFN) for a subway system to capture the state dependencies among stations, and develops the analysis procedure for solving the station selection problem. Practical analysis is conducted using data from the Shanghai subway system. The results show that the critical station identifications are dependent on the time period for control. The stations connected with few stations, or with low passenger volume may also be critical for subway system performance, especially stations with low inflow. This study contributes a quantitative method for subway system managers to develop effective passenger flow control strategies.     

Exact boundary controllability results for a Rao–Nakra sandwich beam

The Rao–Nakra model of a three layer sandwich beam is analyzed for exact boundary controllability. The damped and undamped cases are considered. The multiplier method is used to obtain required observability inequalities that imply controllability. It is shown that if the control time T is large enough, under certain other parametric restrictions, the system is exactly controllable.     

现场可控非致命的次声武器研究

根据次声对人体作用的特点,提出了现场可控非致命次声武器的概念.用PZT晶体的逆向压电效应作为次声元,由M×N个次声元排成阵列进行叠加,得到高声压次声.又依相位控制干涉原理,使次声聚束定向传播,从而解决了次声武器的两个技术关键,使可控非致命次声武器成为可行.这种次声武器,现场可控制次声的强弱和有无,隐蔽性很强.     

Monomial reachability and zero controllability of discrete-time positive switched systems

In this paper, monomial reachability and zero controllability properties of discrete-time positive switched systems are investigated. Necessary and sufficient conditions for these properties to hold, together with some interesting examples and some testing algorithms, are provided.     

改进的部分扫描触发器选择的方法

研究了部分扫描触发器的选择，对原有的基于状态密度的方法做了一些改进，提出一种综合的，基于故障可控性和可观性的扫描触发器选择的方法，并分析了扫描触发器对电路时序特性的影响，在对ISCAS 89标准电路的模拟中，该方法对大部分电路可以减少选择的扫描触发器的个数，提高测试效率和测试覆盖率。     

对流式高温相变蓄热电暖器的可控特性分析

文章对蓄热电暖器的设备性能、可控特性及内自然对流对储热释热过程的影响进行了研究,结论是内自然对流及可控特性有助于放缓储热释热速率,延长释热时间。在15m^2的公寓内进行测试,电暖气能保证室内温度在209~279之间。     

复杂网络系统可控性研究综述

复杂网络是一类由很多错综复杂的网络交织而成的结合,通过研究复杂网络的可控性,探究如何对复杂网络施加控制使其到达我们所期望的状态。现阶段的复杂网络可控性研究主要集中在复杂网络点动态的线性时不变系统,本文对复杂网络点动态的可控性进行了探究。