传输线中特殊的电磁波与相对论

本文分别在面电流分布情形和体电流分布情形研究了两根平行传输线以及同轴电缆的单位长度电感和单位长度电容。研究了平行传输线以及同轴电缆的等效电路和传输线方程。研究了平行传输线和同轴电缆中特殊的电磁波以及信号传送与相对论的关系。

电荷守恒定律的边界条件

在现行教材中，电荷守恒定律的边界条件一般仅考虑体分布的电流，而没有考虑面分布的电流．本文论述了同时考虑面电流的必要性，推导了在这样的条件下，电荷守恒定律的边界条件的形式，并讨论了该边界条件的意义及其应用．

Geometric Design of Anode-Supported Micro-Tubular Solid Oxide Fuel Cells by Multiphysics Simulations

High volumetric power density （VPD） is the basis for the commercial success of micro-tubular solid oxide fuel cells （mtSOFCs）. To find maximal VPD （MVPD） for anode-supported mtSOFC （as-mtSOFC）, the effects of geometric parameters on VPD are analyzed and the anode thickness, tan, and the cathode length, lea, are identified as the key design parameters. Thermo-fluid electrochemical models were built to examine the dependence of the electrical output on the cell parameters. The multiphysics model is validated by reproducing the experimental I-V curves with no adjustable parameters. The optimal lea and the corresponding MVPDs are then determined by the multiphysics model for 20 combinations of rin, the inner tube radius, and tan. And all these optimization are made at 1073.15 K. The results show that： （i） significant performance improvement may be achieved by geometry optimization, （ii） the seemingly high MVPD of 11 and 14 W/cm^3 can be easily realized for as-mtSOFC with single- and double-terminal anode current collection, respectively. Moreover, the variation of the area specific power density with/cac（2 mm, 40 mm） is determined for three representative （tin, tan） combinations. Besides, it is demonstrated that the current output of mtSOFC with proper geometric parameters is comparable to that of planar SOFC.

Effects of mask wall angle on matrix-hole shape changes during electrochemical machining by mask

The influences of the mask wall angle on the current density distribution,shape of the evolving cavity and machining accuracy were investigated in electrochemical machining(ECM) by mask.A mathematical model was developed to predict the shape evolution during the ECM by mask.The current density distribution is sensitive to mask wall angle.The evolution of cavity is determined by the current density distribution of evolving workpiece surface.The maximum depth is away from the center of holes machined,which leads to the island appearing at the center of cavity for mask wall angles greater than or equal to 90°(β≥90°).The experimental system was established and the simulation results were experimentally verified.The results indicate that the simulation results of cavity shape are consistent with the actual ones.The experiments also show that the repetition accuracy of matrix-hole for β≥90° is higher than that for β<90°.A hole taper is diminished,and the machining accuracy is improved with the mask wall angle increasing.

机电组件

Y2002-63302-101 0302670超薄 MOS 电容器的退火效应=Annealing effects on ul-trathin MOS capacitors[会,英]/Ng,A.C.-H.& Xu,J.//2001 IEEE Hong Kong Electron Devices Meet-ing.—101～105(E)Y2002-63333-2244 0302671纳米电机系统中纳米级电磁机械的模拟、分析和控制=Modeling,analysis,and control of nanoscale electro-magnetic machines in nanoelectromechanical systems[会,英]/Lyshevski,S.E.& Lyshevsk,M.A.//Proceed-ings of the 2001 American Control Conference Vol.3 of6.—2244～2248(HE)0302672RF-MEMS 电感三维衬底耦合的扩展 PEEC 法分析[刊]/龙海波//电子学报.—2002,30(9).—1308～1312(C) Y2002-63302-101 0302670超薄 MOS 电容器的退火效应=Annealing effects on ul-trathin MOS capacitors[会,英]/Ng,A.C.-H.& Xu,J.//2001 IEEE Hong Kong Electron Devices Meet-ing.—101～105(E)Y2002-63333-2244 0302671纳米电机系统中纳米级电磁机械的模拟、分析和控制=Modeling,analysis,and control of nanoscale electro-magnetic machines in nanoelectromechanical systems[会,英]/Lyshevski,S.E.& Lyshevski,M.A.//Proceed-ings of the 2001 American Control Conference Vol.3 of6.—2244～2248(HE)0302672RF-MEMS 电感三维衬底耦合的扩展 PEEC 法分析[刊]/龙海波//电子学报.—2002,30(9).—1308～1312(C)0302673基于超程时间减小速率建模的电磁继电器可靠性寿命分析方法的研究[刊]/翟国富//电子器件.—2002,25(3).—301～304(L)电磁继电器触点的磨损和老化是影响继电器可靠性的重要因素之一。超程时间的减小是电磁继电器触点磨损和老化的主要表现形式。本文提出以超程时间减小速率为随机变量,建立了电磁继电器可靠性寿命分析数学模型,给出了寿命可靠度计算方法。实例计算结果表明,该模型是有效的。参6一种使用平面线圈结构的微型电磁继电器[刊]/张宇峰//电子器件.—2002,25(3).—214～219(L)本文介绍一种采用平面线圈结构的微型电磁继电器的制造工艺和理论分析。这种继电器的大小大约是4min×4mm×0.5mm,工艺比较简单,主要采用光刻、蒸镀、电镀和腐蚀牺牲层等普通的微加工技术来完成全部制作工艺。因此可以大大地降低继电器的生产成本、物理尺寸和制造的复杂性。另外,还进行了一些有关线圈通过激励电流后对活动电极产生电磁力的理论计算和仿真,利用这些结果可以对这种电磁继电器的结构和参数进行优化设计。参40302675电爆炸断路开关[刊]/龚兴根//强激光与粒子束.—2002,14(4).—577～582(E)叙述了金属导体电爆炸的物理过程,分析了金属导体电爆炸时电阻率与比作用量、压力、能量、密度、爆炸产物膨胀速度、导体电流密度及周围介质等影响因素的关系,从而确定电爆炸断路开关的一般设计原则。参90302676功率连接器故障分析与模拟[刊]/罗国平//中国邮电高校学报(英文版).—2002,9(3).—79～80(E)0302677电流监测在笼型异步电动机转子故障诊断中的应用[刊]/王旭红//长沙电力学院学报(自然科学版).—2002,17(3).—41～43(K)

Flexible thermocells for utilization of body heat

Plastic thermo-electrochemical ceils （thermocells） involving aqueous potassium ferricyanide/ferrocyanide electrolyte have been investigated as an alternative to conventional thermoelectrics for thermal energy harvesting. Plastic thermocells that consist of all pliable materials such as polyethylene terephthalate （PET）, fabrics, and wires are flexible enough to be wearable on the human body and to be wrapped around cylindrical shapes. The performance of the thermocells is enhanced by incorporating carbon nanotubes into activated carbon textiles, due to improved charge transfer at the interface. In cold weather conditions （a surrounding temperature of 5 ℃）, the thermocell generates a short-circuit current density of 0.39 A/m2 and maximum power density of 0.46 mW/m2 from body heat （temperature of 36℃）. For practical use, we have shown that the thermocell charges up a capacitor when worn on a T-shirt by a person. We also have demonstrated that the electrical energy generated from waste pipe heat using a serial array of the thermocells and voltage converters can power a typical commercial light emitting diode （LED）.

Cement-and-pebble nanofluidic membranes with stable acid resistance as osmotic energy generators

Osmotic energy between river water and seawater has attracted interest as a new source of sustainable energy.Nanofluidic membranes in a reverse electrodialysis configuration can capture energy from salinity gradients.However,current membrane materials suffer from high resistances,low stabilities,and low charge densities,which limit their further application.Here,we designed a high-performance nanofluidic membrane using carboxylic cellulose nanofibers functionalized with graphene oxide nanolamellas with cement-and-pebble microstructures and stable skeletons for enhanced ion transmembrane transport.By mixing artificial river water and seawater,the composite membrane achieved a high output power density up to 5.26 W m^(−2).Additionally,the membrane had an excellent acid resistance,which enabled long-term use with over 67 W m^(−2) of power density.The performance of this composite membrane benefited from the mechanically strong cellulose fibers and the bonding between nanofibers and nanolamellas.In this work,we highlight promising directions in industrial waste treatment using energy extracted from chemical potential gradients.

Porous honeycomb-like C3N4/rGO composite as host for high performance Li-S batteries

Lithium-sulfur (Li-S) batteries have attracted extensive attention along with the urgent increasing demand for energy storage owing to the high theoretical specific capacity and energy density, abundant reserves and low cost of sulfur. However, the practical application of Li-S batteries is still impeded due to the low utilization of sulfur and serious shuttle-effect of lithium polysulfides (LiPSs). Here, we fabricated the porous honeycomb-like C3N4 (PHCN) through a hard template method. As a polar material, graphitic C3N4 has abundant nitrogen content (-58%), which can provide enough active sites to mitigate shuttle-effect, and then conductive reduced graphene oxide (rGO) was introduced to combine with PHCN to form PHCN/rGO composite in order to improve the utilization efficiency of sulfur. After sulfur loading, the PHCN/rGO/S cathode exhibited an initial discharge capacity of 1,061.1 mA h g^-1 at 0.2 C and outstanding rate performance at high current density of 5 C (495.1 mA h g^-1), and also retained 519 mA h g^-1, after 400 cycles at 1 C. Even at high sulfur loading (4.3 mg cm^-2), the capacity fade rate was only 0.16% per cycle at 0.5 C for 200 cycles. The above results demonstrate that the special design of PHCN/rGO composite as sulfur host has high potential application for Li-S rechargeable batteries.

Robust superconductivity and transport properties in (Li_(1-x)Fe_x)OHFeSe single crystals

The recently discovered(Li_(1-x) Fe_x)OHFe Se superconductor with T c about 40 K provides a good platform for investigating the magnetization and electrical transport properties of Fe Se-based superconductors. By using a hydrothermal ion-exchange method,we have successfully grown crystals of(Li_(1-x) Fe_x)OHFe Se. X-ray diffraction on the sample shows the single crystalline Pb O-type structure with the c-axis preferential orientation. Magnetic susceptibility and resistive measurements show an onset superconducting transition at around T c=38.3 K. Using the magnetization hysteresis loops and Bean critical state model, a large critical current J s is observed in low temperature region. The critical current density is suppressed exponentially with increasing magnetic field.Temperature dependencies of resistivity under various currents and fields are measured, revealing a robust superconducting current density and bulk superconductivity.

Optimization design of GaN betavoltaic microbattery

Betavoltaic radioisotope microbatteries have gradually become the research direction of micro-power sources because of their several advantages,including small scale,stable output performance,long service life,high energy density,strong anti-jamming capability,and so on.Based on the theory of semiconductor physics,the current paper presented a design scheme of isotope microbattery with wide-gap semiconductor material GaN and isotope 147Pm.In consideration of the isotope's self-absorption effect,the current paper studied and analyzed the optimization thickness of semiconductor and isotope source,junction depth,depletion region thickness,doping concentration,and the generation and collection of electron hole pairs with simulation of transport process of beta particles in semiconductor material using Monte Carlo simulation program MCNP.In the proposed design scheme,for a single decay,an average energy of 28.2 keV was deposited in the GaN,and the short circuit current density,open circuit voltage,and efficiency of a single device were 1.636 μA/cm2,3.16 V,and 13.4%,respectively.

SnSe2 nanocrystals coupled with hierarchical porous carbon microspheres for long-life sodium ion battery anode

Tin selenides have been attracting great attention as anode materials for the state-of-the-art rechargeable sodium-ion batteries(SIBs)due to their high theoretical capacity and low cost.However,they deliver unsatisfactory performance in practice,owing to their intrinsically low conductivity,sluggish kinetics and volume expansion during the charge-discharge process.Herein,we demonstrate the synthesis of SnSe2 nanocrystals coupled with hierarchical porous carbon(SnSe2 NCs/C)microspheres for boosting SIBs in terms of capacity,rate ability and durability.The unique structure of SnSe2 NCs/C possesses several advantages,including inhibiting the agglomeration of SnSe2 nanoparticles,relieving the volume expansion,accelerating the diffusion kinetics of electrons/ions,enhancing the contact area between the electrode and electrolyte and improving the structural stability of the composite.As a result,the as-obtained SnSe2 NCs/C microspheres show a high reversible capacity(565 mA h g^-1 after 100 cycles at 100 mA g^-1),excellent rate capability,and long cycling life stability(363 mA h g^-1 at1 A g^-1 after 1000 cycles),which represent the best performances among the reported SIBs based on SnSe2-based anode materials.

Cubic imidazolate frameworks-derived CoFe alloy nanoparticles-embedded N-doped graphitic carbon for discharging reaction of Zn-air battery

The construction of transition metal-based catalysts with high activity and stability has been widely regarded as a promising method to replace the precious metal Pt for oxygen reduction reaction(ORR).Herein,we synthesized CoFe alloy nanoparticle-embedded N-doped graphitic carbon(CoFe/NC)nanostructures as ORR electrocatalysts.The ZIF-67(zeolitic imidazolate framework,ZIF)nanocubes were first synthesized,followed by an introduction of Fe2+ions to form CoFe-ZIF precursors via a simple ion-exchange route.Subsequently,the CoFe/NC composites were synthesized through a facile pyrolysis strategy.The ORR activity and the contents of cobalt and iron could be effectively adjusted by controlling the solution concentration of Fe2+ions used for the ion exchange and the pyrolysis temperature.The CoFe/NC-0.2-900 composite(synthesized with 0.2 mmol of FeSO4·7H2O at a pyrolysis temperature of 900℃)exhibited ORR activity that was superior to the other samples owing to a synergistic effect of the bimetal,especially considering the extremely high limiting current density of 6.4 mA cm^-2 compared with that of Pt/C(5.1 mA cm^-2).Rechargeable Zn-air batteries were assembled employing CoFe/NC-0.2-900 and NiFeP/NF(NiFeP supported on nickel foam(NF))as the catalysts for the discharging and charging processes,respectively,The above materials achieved reduced discharging and charging platforms,high power density,and prolonged cycling stability compared with conventional Pt/C+RuO2/C catalysts.

Tandem organic light-emitting diodes with buffermodified C_(60)/pentacene as charge generation layer

Buffer-modified C_(60)/pentacene as charge generation layer(CGL) is investigated to achieve effective performance of charge generation. Undoped green electroluminescent tandem organic light-emitting diodes(OLEDs) with multiple identical emissive units and using buffer-modified C_(60)/pentacene organic semiconductor heterojunction(OHJ) as CGL are demonstrated to exhibit better current density and brightness, compared with conventional single-unit devices. The current density and brightness both can be significantly improved with increasing the thickness of Al. However, excessive thickness of Al seriously decreases the transmittance of films and damages the interface. As a result, the maximum current efficiency of 1.43 cd·A^(-1) at 30 mA ·cm^(-2) can be achieved for tandem OLEDs with optimal thickness of Al. These results clearly demonstrate that Cs_2CO_3/Al is an effective buffer for C_(60)/pentacene-based tandem OLEDs.

Ignition of Hydrocarbon-Air Supersonic Flow by Volumetric Ionization

The paper describes the results of the electron-beam initiation of the combustion in the mixtures of hydrogen,natural gas or kerosene vapors with air.Electron beam characteristics were studied in closed volume with immobile gas.The researches included definition of an integrated current of an electronic beam,distribution of a current density and an estimation of average energy of electrons.Possibility of fuel mixtures ignition by means of this approach in the combustor at high velocity at the entrance was demonstrated.Experiments were carried out at Mach numbers of 4 and 5.Process of ignition and combustion under electron beam action was researched.It was revealed that ignition of mixture occurs after completion of electron gun operation.Data obtained have confirmed effectiveness of electron beam application for ignition of hydrogen and natural gas.The numerical simulation of the combustion of mixture in channel was carried out by means of ANSYS CFD 12.0 instrumentation on the basis of Reynolds averaged Navier-Stokes equation using SST/k-ωturbulence model.For combustion modeling,a detailed kinetic scheme with 38 reactions of 8 species was implemented taking into account finite rate chemistry.Computations have shown that the developed model allow to predict ignition of a mixture and flame propagation even at low flow temperatures.

GaN-based LEDs for light communication

Rapid improvement in the efficiency of GaN-based LEDs not only speed up its applications for general illumination, but offer the possibilities for data transmission. This review is to provide an overview of current progresses of GaN-based LEDs for light communications. The modulation bandwidth of GaN-based LEDs has been first improved by optimizing the LED epilayer structures and the modulation bandwidth of 73 MHz was achieved at the driving current density of 40 A/cm2 by changing the multi-quantum well structures. After that, in order to increase the current density tolerance, different parallel flip-chip micro-LED arrays were fabricated. With a high injected current density of ~7900 A/cm2, a maximum modulation bandwidth of ~227 MHz was obtained with optical power greater than 30 mW. Besides the increase of carrier concentrations, the radiative recombination coefficient B was also enhanced by modifying the photon surrounding environment based on some novel nanostructures such as resonant cavity, surface plasmon, and photonic crystals. The optical 3 dB modulation bandwidth of GaN-based nanostructure LEDs with Ag nanoparticles was enhanced by 2 times compared with GaN-based nanostructure LEDs without Ag nanoparticles.Our results demonstrate that using the QW-SP coupling can effectively help to enhance the carrier spontaneous emission rate and also increase the modulation bandwidth for LEDs, especially for LEDs with high intrinsic IQE. In addition, we discuss the progress of the faster color conversion stimulated by GaN-based LEDs.

Nano-photonic crystal formation on highly-doped n-type silicon

We present a novel electrochemical technique for the fabrication of nano-photonic crystal structures. Based on a specially designed electrolyte, porous silicon(PSi) layers with different porosities are possible to be produced on highly-doped n-type silicon substrate by varying the applied current density which determines the size and the morphology of pores. By applying an alternative current density modulation during anodization, porous silicon photonic crystals are obtained using HF-containing electrolyte without oxidizing components. The current burst model(CBM) is employed to interpret the mechanism of the formation of the macropore porous silicon.