A Universal Descriptor in Determining H2 Evolution Activity for Dilute Aqueous Zn Batteries

Large-scale energy storage with aqueous Zn batteries (AZBs) have bright future, but their practical application is impeded by H₂ evolution reaction (HER), which results in poor stability of Zn–metal anodes. Here, using linear sweep voltammetry in dilute salt aqueous electrolytes, it is discovered that as the salt concentration decreases, HER is gradually suppressed, which is contrary to prior beliefs. Combining calculations and experiments, it is demonstrated that HER derives predominantly from the sum of Zn²⁺-solvated water rather than the average amount of water in the Zn²⁺-solvation structural unit or free water without interaction with Zn²⁺, which answers the puzzle from above. This result, which differs fundamentally from the previous understandings, sheds new light on the mysterious role of water chemistry in controlling HER and contributes to a more rational design of advanced electrolytes for AZBs.     

电力电子磁技术教学探讨

磁性元件为电力电子电路的关键器件之一.它们在现有教材中的相关内容不仅少而且零散,与其地位不相称.由于电力电子电路的开关方式以及控制方式的多样性,使得电路中磁性元件的工作模式比较复杂,成了学习的难点.为此,笔者在教学中增加了磁基础知识回顾、磁芯损耗和线圈设计技术以及磁性元件设计方法等磁技术基础内容,并积极研究了采用图形法与电磁场有限元仿真软件等磁技术教学方法.教学实践证明补充的教学内容和采用的教学方法均取得了良好的教学效果.     

欧洲主要电信运营商专线资费的演变

欧洲主要电信运营商所处国度的经济和人口布局情况不同，竞争环境也有差别，在专线资费方面的做法也有许多不同之处。考虑到地区之间竞争的差异。目前多数国家都取消了地区交叉补贴的做法，但还有一部分国家仍然坚持统一费率。在资费方面的基本促销手段为接合同年限和用户的支出额打折。从2000年到2003年资费演变的基本情况是；接入费扣2Mbit／s以下较低速率的专线租费保持平稳略有下降，较高速率专线的租费则有较大的下调幅虚。     

Markov Approach to Percolation Theory Based Propagation in Random Media

For line-of-sight links in random media or urban areas, propagation may be approximated through sequential reflections of an optical ray in a two-dimensional medium of disordered lossless scatterers. Franceschetti approximated such percolation-based optical-ray propagation by a Markov process with two absorbing barriers, provided numerical solutions for the probability of a ray passing through the percolation lattice and solved-both approximately and exactly-a corresponding problem based on the theory of martingales. In this paper we solve exactly the Markov-theoretical formulation of the problem and prove that both the Markov and martingale approaches are equivalent. Our proof is an application of the Perron-Frobenius theory which provides an elegant framework for the study of the asymptotic behavior of stochastic processes. We demonstrate that for a wide range of vacancies and incident angles the exact solution of the Markov-theoretical formulation performs significantly better than the commonly used Wald approximation in the martingale approach. This has a number of implications on the accuracy of the model, especially for low density propagation media.     

极限环频率对自激振荡线路驱动器的影响分析

目前自激振荡线路驱动器由于极限环频率较低,在输入信号频率较高时,系统增益下降较大,由延时决定的自激振荡线路驱动器可提高极限环频率。本文分析了提高极限环频率后系统增益、线性度和功耗等的变化,并采用0.25μm CMOS工艺设计了一个VDSL线路驱动器进行验证。实验结果表明,提高极限环频率可减小高频输入信号时系统增益的下降,且在一定范围内可提高线性度,但过高的极限环频率会引入过大的电源噪声和地噪声,恶化线性度。     

Properties of Near and Far Fields for the Electric Line Source Illumination of a Lossy Metamaterial Covered Dielectric Cylinder

The electric field properties of the electric line source radiation in the presence of a lossy metamaterial covered dielectric cylinder are investigated. Firstly, the electromagnetic model configuration is given. The exact solution of the electromagnetic is presented. Secondly, the near field and the far field properties are investigated according to the electromagnetic and geometrical parameters. The different “focus” phenomenon, the directivities and the normalized radiation resistance are discussed and important conclusions are obtained. During all the numerical computation, the lossy conventional material covered dielectric cylinder is utilized as the reference.     

Limit Cycles in a MEMS Oscillator

In this paper, we apply methods of nonlinear dynamics to study the behavior of a microelectromechanical oscillator. We show how the analysis predicts the appearance of a devil's staircase-like relationship between frequencies, but also show how the output frequency of the oscillator, and hence the devil's staircase, may not be uniquely determined. Both of these features—the sequence of steps corresponding to different output frequencies and the fact that the output frequency may not be uniquely defined for a given set of parameters—have a direct bearing on the ease with which a designer can produce an useful oscillator of this form.      

Numerical Simulation of Magnetoresonance Absorption for Multilayered Co/Cu Nanostructures in the Millimeter Waveband

The numerical simulation of the Ferromagnetic Resonance (FMR) absorption in the millimeter waveband has been performed for magnetic multilayered nanostructures. The model taking into account a random bilinear exchange interaction between layers was applied for the theoretical approach elaboration. Results of the simulation are in good agreement with experimental data registered for samples of nanostructure Co/Cu with buffer layer Fe in the frequency band 20-37 GHz. The explanation of the origin of unexpectedly broad magnetoresonance peaks formed in specimen under study is suggested.     

集团大客户专线接入的发展及演进

集团大客户专线在联通占有非常重要的位置,文章以联通集团客户专线在IP RAN网络和MSTP网络共存下的建网研究为目的,对襄阳联通及其他联通网络、集团专线的业务进行分析,提出未来集团专线业务接入的演进模式。     

Near fields of a linear antenna

The near fields of a strip antenna in free space have been computed by modifying a variational-impedance formulation. Current distributions, which vary linearly with distance near the ends of the antenna, excite strong tangential electric fields on the antenna surface. Such surface fields are avoided by choosing the axial antenna current to vary in proportion to the square root of the distance from the antenna ends. This modification of the antenna current is not necessary, however, for field calculations at distances comparable to the antenna width. The fields parallel to the antenna surface decrease with increasing distance from the antenna near the driving point and the antenna ends, but are found to increase in an intermediate range.     

激光导引星非等晕性的限制

在利用激光导引星的自适应光学系统中，焦距非等晕性是对自适应光学系统性能的主要限制，利用湍流探测配置的孔径滤波函数导出了剩余波前畸变方差．并依此导出了成像系统的有效直径ｄ０，根据昆明和兴隆实测的大气湍流模型对ｄ０进行了计算，说明了校正平移和倾斜对自适应光学系统的重要性。     

Effect of Signal Polarization State Evolution in Amplified Recirculating Delay Line Signal Processors

A study of signal polarization state evolution in an amplified recirculating delay line (RDL) signal processor is presented. It shows that the change in the RDL signal polarization states behaves periodically, which can be described by a sinusoidal function. This change significantly alters the RDL signal processor frequency response shape when a polarization dependent component is connected at the signal processor output. Results demonstrate the validity of the equation that is used to predict the frequency response shape of the amplified RDL filter for different signal polarization state evolutions.     

Transponder Antennas in and Near a Three-Layered Body

The electric field in a three-layered half-space iluminated by an incident plane wave is reviewed and numerical data provided when the layers are skin, fat and muscle. The impedance and voltage across the load of a dipole antenna is discussed when this is located in each of the three Iayer and in the air near the surface. Bare and insulated antennas are considered over a frequency range up to 3 GHz with layer thicknesses of skin from 0.2 to 1.0 cm, and of fat from 0 to 1.5 cm. The transmitting problem is discussed as well as application of the results to finite bodies.     

单模光纤反常色散区零色散波长附近的啁啾演变

当单模光纤的反常色散区二阶，三阶色散同时存在时，首次推出了群速度色散致啁啾的解析表达式，并讨论了啁啾演变过程。利用数值方法，模拟了零色散波长附近群速度色散效应与自相位调制效应共同作用时啁啾的演变。结果表明，三阶色散会导致脉冲铅的畸变。     

对电信资费上下限区间规制的探讨

在对电信资费上限和下限管制的研究基础上,提出了电信资费上下限区间的概念和规制方法,以此达到变单一的价格竞争模式为多元的竞争模式,变信息不完全的博弈为信息完全博弈的目的,希望通过这些方法能够对未来更加有效的电信竞争规制有所帮助.     

Transmission Line Coupled to a Cylinder in an Incident Field

An approximate formula is derived for the currents in the loads terminating a two-wire line located parallel to and near a circular conducting cylinder of finite length. The line and the cylinder are illuminated by an incident plane wave. The analysis takes account of the coupling between the line and the cylinder and hence of the effects of possible axial resonances in the latter. The configuration simulates exposed conductors used to interconnect the electronic apparatus in a rocket. The analysis is directed toward determining possible hazards due to induced currents.     

低压差稳压电源的折返式限流保护电路的设计

为了防止因负载短路和过载对芯片造成永久性的伤害,芯片中通常需要加入限流保护电路。文中从限流保护的原理出发,设计了一款用于LDO的折返式(FOLDBACK)限流保护电路。该电路不仅很好地完成了限流保护功能,同时大大降低了芯片的短路功耗。该设计采用0.6μmBiCMOS高压工艺。Hspice仿真结果表明:与常规的恒定电流限制相比,折返式限流电路在限流状态下能使系统的功耗减少70%以上。     

Vortex Formation Near an Iris in a Rectangular Waveguide

The generalized dual-series approach to the capacitive and inductive iris waveguide problems is presented. Currents on the iris and plots of the fields and power flow in the vicinity of the iris are given for the capacitive iris case. It is found that vortices form in the iris region when higher order scattered modes are present. The formation of these vortices and their properties will be described in this paper.     

Limit of optical-frequency comb generation due to materialdispersion

The limit of optical frequency comb (OFC) generation (i.e., the limit of frequency difference measurement) due to the material dispersion in the EO crystal is experimentally studied. By using a modified monolithic OFC generator, we observed the OFC spectrum, and confirmed that the envelope of the OFC around 780 nm extended to a span as wide as 16 nm (or 7.6 THz) reaching the limit of the OFC generation. We also proposed a method of stabilizing the Fabry-Perot cavity for the monolithic OFC generator     

平面近场测量中截断误差对口径场的不确定性分析

截断误差作为近场测试中较大的误差源之一,对它的分析和研究有一定的必要性。为构造出真实的口径场,找出阵中失效单元的位置,以更好地“诊断”天线,文中对截断误差对口径场的影响进行了分析,并用计算机模拟的方法通过构建模型分析了不同的截断角对天线口径场幅度相位的影响。