Synthesis and electrochemical properties of Zn3V3O8 as novel anode material

Zn₃V₃O₈ two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The Zn₃V₃O₈ has better electrochemical performances after calcinations.     

Optimal feedback gains of a delayed proportional-derivative (PD) control for balancing an inverted pendulum

In the dynamics analysis and synthesis of a con-trolled system, it is important to know for what feedback gains can the controlled system decay to the demanded steady state as fast as possible. This article presents a sys-tematic method for finding the optimal feedback gains by taking the stability of an inverted pendulum system with a delayed proportional-derivative controller as an example. First, the condition for the existence and uniqueness of the stable region in the gain plane is obtained by using the D-subdivision method and the method of stability switch. Then the same procedure is used repeatedly to shrink the stable region by decreasing the real part of the rightmost charac-teristic root. Finally, the optimal feedback gains within the stable region that minimizes the real part of the rightmost root are expressed by an explicit formula. With the optimal feedback gains, the controlled inverted pendulum decays to its trivial equilibrium at the fastest speed when the initial val-ues around the origin are fixed. The main results are checked by numerical simulation.     

Surface modification by graphene oxide:An efficient strategy to improve the performance of activated carbon based supercapacitors

An efficient and cost-effective strategy to modificate the surface of active carbon (AC), form a 3D-conductive network, and therefore improve the electrochemical performance of AC based supercapacitor was developed.     

Stability of linear time variant dynamic systems with multiple time delays

By means of the frozen time approach and the Kronecker product, two criteria of asymptotic stability are derived for the linear, time variant dynamic systems with either short time delays or with weak feedback involving arbitrary time delays, respectively. It is found that the asymptotic stability of these retarded dynamic systems is governed by the maximal and minimal singular values of the coefficient matrices and their time derivatives. The project supported by the National Natural Science Foundation of China under the Grant of 59625511.     

Robust Stability Test for Dynamic Systems with Short Delays by Using Padé Approximation

The paper presents a simple approach to testifying the asymptotic stability and interval stability (robust stability against the change of system parameters in given intervals) for linear dynamic systems involving short time delays. The stability analysis starts with the study of the characteristic roots of a transcendental equation having exponential functions. By means of the Padé approximation to the exponential functions, the transcendental characteristic equation is approximated as an algebraic equation. Then, the test of asymptotic stability and interval stability of the system is completed in a very simple way. The stability analysis of a vibration system with short time delays in the feedback paths of displacement and velocity, taken as an example, is given in detail. The analysis and numerical examples indicate that the approach gives excellent accuracy for linear dynamic systems with short time delays.     

氦气置换过程中未知杂质分析

用美国GOW—MAC公司的气相色谱仪和Agilent公司的气相色谱仪对某卫星气体贮箱在氦气置换化验过程中发现的未知杂质进行试验分析,经分析未知杂质的来源可能是所用气体贮箱处理时的残留物。试验发现,氧化剂贮箱氦气和燃烧剂贮箱氦气经3次氦气置换后未知杂质的色谱峰消失。提出了消除未知杂质的的建议。     

Kinetics and rate-limiting mechanisms of dolomite dissolution at various CO2 partial pressures

Techniques of rotating-disk and catalyst were used in investigating the kinetics of dolomite dissolution in flowing CO₂-H₂O system. Experiments run in the solutions equilibrated with various CO₂ partial pressures (P_{CO 2} ) from 30 to 100000 Pa. It shows that dissolution rates of dolomite are related with rotating speeds at conditions far from equilibrium. This was explained by modified diffusion boundary layer (DBL) model. In addition, the dissolution rates increase after addition of carbonic anhydrase (CA) to solutions, where the CA catalyzes CO₂ conversion. However, great differences occur among various CO₂ partial pressures. The experimental observations give a conclusion that the modified DBL model enables one to predict dissolution rates and their behaviour at various P_{CO 2} with satisfactory precision at least far from equilibrium.     

机构投资者参与公司治理监督的非合作对策

本文研究了 n个机构投资者在参与公司治理 ,对公司实施监督的过程中非合作博弈情况 .在 n个机构投资者不卖出股份等相关假设下 ,其非合作博弈结果是 ,持有股份最大机构投资者才会对公司进行监督 ,其他股东采取搭便车策略 .     

Multiplicity-induced optimal gains of an inverted pendulum system under a delayed proportional-derivative-acceleration feedback

This paper studies the stabilization to an inverted pendulum under a delayed proportional-derivative-acceleration (PDA) feedback, which can be used to understand human balance in quiet standing. The closed-loop system is described by a neutral delay differential equation (NDDE). The optimal feedback gains (OFGs) that make the exponential decaying rate maximized are determined when the characteristic equation of the closed-loop has a repeated real root with multiplicity 4. Such a property is called multiplicity-induced dominancy of time-delay systems, and has been discussed intensively by many authors for retarded delay differential equations (RDDEs). This paper shows that multiplicity-induced dominancy can be achieved in NDDEs. In addition, the OFGs are delay-dependent, and decrease sharply to small numbers correspondingly as the delay increases from zero and varies slowly with respect to moderate delays. Thus, the inverted pendulum can be well-stabilized with moderate delays and relatively small feedback gains. The result might be understandable that the elderly with obvious response delays can be well-stabilized with a delayed PDA feedback controller.