LMI Approach to Output Feedback Control for Linear Uncertain Systems with D-Stability Constraints

This paper deals with the problem of designing output feedback controllers for linear uncertain continuous-time and discrete-time systems with circular pole constraints. The uncertainty is assumed to be norm bounded and enters into both the system state and input matrices. We focus on the design of a dynamic output feedback controller that, for all admissible parameter uncertainties, assigns all the closed-loop poles inside a specified disk. It is shown that the problem addressed can be recast as a convex optimization problem characterized by linear matrix inequalities (LMI); therefore, an LMI approach is developed to derive the necessary and sufficient conditions for the existence of all desired dynamic output feedback controllers that achieve the specified circular pole constraints. An effective design procedure for the expected controllers is also presented. Finally, a numerical example is provided to show the usefulness and applicability of the present approach.     

Matrix Approximation Techniques for Symbolic Extraction of Poles and Zeros

Several recently published approaches to symbolic pole/zero analysis of analog circuits exploit the order reduction effect of Simplification Before Generation (SBG) techniques [1]. SBG methods allow the extraction of symbolic expressions for poles and zeros by computing local low-order approximations of transfer functions whose roots can be calculated analytically. In this article we present a new matrix-based SBG method for pole/zero analysis which simplifies a symbolic generalized eigenvalue problem with respect to a selected root. The method uses a fast linear error estimation formula based on eigenvalue sensitivities to obtain a term ranking. Accurate and efficient error control is achieved by tracking eigenvalue shifts numerically using an iterative generalized eigenvalue solver. The new algorithm is capable of computing real and complex dominant as well as unobservable poles and zeros.     

锂离子电池快充石墨负极研究与应用

Driven by the excessive environmental pollution caused by the over-use of non-renewable fossil-derived energy, renewable energy and electrochemical energy storage devices have made great progress in the past decades. Electrochemical energy storage devices, such as lithium-ion batteries, have the advantages of high capacity, long life cycle, and good safety performance; therefore, they have been used in various applications. For example, economical and environment-friendly electric vehicles have recently taken up increasing market share. However, when compared with vehicles propelled using fossil-derived energy, the slow charging speed of electric vehicles has always restricted their further promotion. The realization of rapid charging for electric vehicles can alleviate the high-pressure usage of charging piles as well as increase the application and market share of electric vehicles. Therefore, it is important to develop high-performance lithium-ion batteries with rapid charge and discharge capacities. The fast-charging capacity of lithium-ion batteries is limited by the slow migration of lithium ions in the electrode and the electrode/electrolyte interface. Therefore, the key to developing fast-charging lithium-ion batteries lies in the successful design of suitable electrode materials. Because of its low cost and excellent electrochemical performance, graphite has been widely used to develop the cathode of lithium-ion batteries. However, the migration of lithium ions in graphite is slow, resulting in large polarization during the high-current charge and discharge processes. In addition, the low lithium intercalation potential of graphite leads to lithium precipitation during fast charging, which can decrease the electrochemical performance and cause potential safety hazards. Therefore, graphite must be improved to meet the needs of such fast-charging devices. In this article, we systematically introduce the research progress made in recent years within the scope of rapid-charging improvement of graphite(-based) cathodes and then highlight the modification strategies for graphite with the goal of achieving functional coating, desired morphological and structural design, optimized electrolyte properties, and an improved charging protocol. Additionally, this article evaluates the advantages and disadvantages of the modification strategies as well as their application prospects. The scheme of functional coating for modifying graphite must simplify the process and improve production efficiency to meet the needs of industrial development. Morphology design should ensure satisfactory initial Coulomb efficiency, while the improvement of the electrolyte properties and optimization of the charging protocol need to consider the commercialization costs. Finally, this paper proposes further evaluation of the effects of the modification strategies based on soft-pack or cylindrical batteries to strengthen the commercialization prospect of the modification strategies.      

Characteristics of microwave filters based on microstrip photonic bandgap ring structures

We study the characteristics of microstrip ring exhibiting photonic band gap properties. Since the stop band is caused by the reflection of electromagnetic waves at the narrow gap introduced in the ring, the geometry of the ring can influence on the characteristics of stop band. The center frequency of the stop band is determined mainly by the outer ring radius when the line width of the circular ring is rather narrow. But it is determined mainly by the mean ring radius when the ring is not a circular form or the line width of circular ring is wide. The frequency range of the stop band can be varied by a reactive component mounted on the gap. The presence of capacitor (inductor) on the gap decreases (increases) the center frequency and the frequency range of the stop band. Moreover, the stop band can be widened by modifying the geometry of ring. These properties can be useful in the applications to the compact microwave circuits, tunable filters and microwave switches.     

数字信号处理中的最小相位系统初探

最小相位系统在数字信号处理理论和应用中具有重要意义。本文详细地阐述了最小相位系统的含义和基本性质,给出利用Matlab中FDATool工具设计最小相位系统的实现方法。通过对比信号经过IIR滤波器和最小相位系统后的时域波形变化,对最小相位系统的重要性质进行验证。     

[Amim]Cl离子液体中微波辐射加热促进稻草秸秆酸水解制备还原糖

在1-烯丙基-3-甲基咪唑氯盐([Amim]Cl)离子液体介质中,用微波辐射加热促进稻草秸秆纤维素的酸水解,探讨了微波辐射加热及离子液体对酸催化植物纤维素水解的促进作用;并对水解产物中的还原糖进行了测定,着重考察了离子液体用量、硫酸浓度、微波功率、反应温度、反应时间等因素对还原糖收率的影响.结果表明,在[Amim]Cl...     

一种弯曲模态直线超声电机的研究

提出了一种改进的弯曲模态直线超声电机。该电机利用兰杰文振子两相正交的3阶弯曲振动,在其驱动足处形成椭圆运动,推动动子运动。采用超声变幅放大了定子驱动足处的振幅。利用有限元方法用来设计定子的结构尺寸。实验表明,在电压峰-峰值200V下,该电机最大空载速度为113mm/s,最大输出力为10N。     

Narrow-track perpendicular write heads

Narrow-track perpendicular write heads are reviewed. Because of the strong magnetic interaction between the write head and double-layered medium in perpendicular recording, various types of media are also considered. Current technology is discussed to illustrate design issues; then, for areal densities beyond 1 Tb/in², future technological requirements, including single-pole-type (SPT) heads for discrete track and bit-patterned media, are examined based on numerical simulations.     

Study of excited nucleon states at EBAC: status and plans

We present an overview of a research program for the excited nucleon states in Excited Baryon Analysis Center （EBAC） at Jefferson Lab. Current status of our analysis of the meson production reactions based on the unitary dynamical coupled-channels model is summarized, and the N＊ pole positions extracted from the constructed scattering amplitudes are presented. Our plans for future developments are also discussed.     

Extraction of resonance parameters from meson production reaction

We have developed an analytic continuation method for extracting parameters of nucleon resonances within a Hamiltonian formulation of meson-nucleon reactions. The method was tested for simple solvable models and then applied for our recent coupled channels model （πN, ηN, π△, ρN, and σN ） of the π＊N and γ＊N reactions. The resonance pole positions and their properties are studied for P11and P11 channels.