二氧化锰电池的过去、现在和未来

论述了二氧化锰作为一次电池和二次电池正极材料的历史和现状,指出了二氧化锰电池过去曾占着原电池的统治地位,现在由于二氧化锰改性,因而二氧化锰电池仍有着强大的竞争力;将来,由于将二氧化锰形成复合材料或嵌入电极材料,还将有光辉的前景,有可能出现以二氧化锰为主体的新电池系列.由于二氧化锰固有的特性;贮量较丰富,价格较低廉,符合环境保护要求,在今后的几十年里,尽管有各类高性能电池与之竞争,但以二氧化锰为主体正极材料组成的电池,仍将在电池市场上占有重要的地位.     

Structural, luminescent, and NO2 sensing properties of SnO2-core/V2O5-shell nanorods

SnO₂-core/V₂O₅-shell nanorods were synthesized using a two-step process: thermal evaporation of Sn powders and sputter-deposition of V₂O₅. The core-shell nanorods were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy and photoluminescence spectroscopy. The diameters of these core-shell nanorods ranged from 80 to 200 nm with a shell layer thickness in the range of 7–13 nm. The cores and shells of the annealed core-shell nanorods consisted of a single crystal tetragonal-structured SnO₂ and a single crystal orthorhombic-structured V₂O_5, respectively. Photoluminescence measurements revealed the SnO₂ nanorods to have a yellow emission band centered at approximately 590 nm, which was enhanced significantly by the V₂O₅ coating and further by thermal annealing. The sensitivity of the networked SnO₂-core/V₂O₅-shell nanorod sensor to NO₂ gas was slightly higher than that of the bare SnO₂ nanorod sensor. The enhanced sensitivity of the SnO₂ nanorods by the V₂O₅ coating was attributed to the modulation of electron transport by the SnO₂-V₂O₅ heterojunction with an adjustable energy barrier height.     

Dielectric,impedance and modulus spectroscopy of BaBi2Nb2O9

Barium Bismuth Niobate (BaBi₂Nb₂O₉) has been synthesized by solid state reaction method. The X-ray diffraction study confirms the formation of compound. Morphological analysis has been carried out from the scanning electron microscopy images and the elemental analysis from the energy dispersive spectroscopy profiles. Investigation of dielectric and ferroelectric properties of the sample was done by varying the temperature from 25 °C - 500 °C in a frequency range of 1 kHz- 1 MHz. At 100 kHz, the phase transition was observed at 214.02°C. Further, this ferroelectric bi-layered perovskite exhibits an interesting relaxor behavior with a strong dispersion of the dielectric permittivity. A detailed study on the impedance spectroscopy over a wide range of temperature and frequency exhibits the contribution of grain ad grain boundary on different electrical parameters. From modulus spectroscopy, the presence of non-Debye type of relaxation in the material has been manifested. The complex modulus plots support the negative temperature coefficient of resistance (NTCR) type behavior of the material.     

YB2、YA2系列高效、节能、环保型电动机

本系列高压隔爆型三相异步电动机采用圆筒式铸铁机座,改变了周围布管的传统结构,与同功率电机相比,它具有体积小、重量轻、外形美观、线条流畅、运行可靠、安装、维修方便等优点,比同功率电机中心高均降一档或二档,这在防爆电机设计制造史上可谓从未有过的先例,是质的飞跃。它的成功试制,将会拉动国内整个高压隔爆型三相异步电动机设计制造领域迈出可喜的一步。它的五大性能指标均处于国内领先水平,基本上接近国际领先水平,它的机座通用性极强,基本上可以涵盖目前H355-H630（YB至H710）、Y系列、Y（A）KS系列、Y（A）KK系列、YA系列,可以派生出YA2、YBPT、YAPT、YPT、Y2、YW系列（无火花型）;在激烈的国内市场及国际市场竞争中,它将会代表我国防爆电机行业最先进的生产力,参与市场竞争而立于不败之地。     

Thermodynamic and transport properties of CO2, CO2–O2, and CO2–H2 mixtures at temperatures of 300 to 30,000 K and pressures of 0.1 to 10 MPa

This paper provides the theoretical calculation results of thermodynamic and transport properties of CO₂, CO₂–O₂ mixture, CO₂–H₂ mixture under thermal equilibrium condition at temperatures of 300 to 30,000 K and at pressures of 0.1 to 10 MPa. The gas CO₂ is one of the candidates for the environmentally benign arc‐quenching medium in a circuit breaker. Furthermore, the effect of additional gases O₂ and H₂ on the thermodynamic and transport properties of CO₂ was also investigated in this paper. The hydrogen atom included CO₂ is similar to the polymer ablated vapor in switching devices. First, equilibrium compositions of CO₂, CO₂–O₂ mixture, CO₂–H₂ mixture were calculated through the Gibbs free energy minimization method. Second, thermodynamic properties were computed using the calculated composition. Finally, transport properties were calculated by the first‐order approximation of Chapman– Enskog method using the collision integrals between species. Inclusion of H₂ increases the electrical conductivity of CO₂ in the range 3000 to 6000 K because CHO molecules produced in this temperature range emit more electrons due to the lower ionization potential of CHO. It also increases the thermal conductivity of CO₂ especially due to dissociation reactions of H₂ around 3900 K and ionization of H around 15,000 K. These properties provided here can be used for CO₂ thermal plasma simulation. © 2008 Wiley Periodicals, Inc. Electr Eng Jpn, 163(4): 18–29, 2008; Published online in Wiley InterScience ( www.interscience. wiley.com ). DOI 10.1002/eej.20467     

火电厂联合脱除SO2、NOX新工艺

针对国内火电厂燃煤锅炉治理SO2、NOX现状,提出火电厂联合脱除SO2、NOX的新工艺,介绍该工艺的系统结构、原理、流程及特点,并分析该工艺的可行性和应用前景。     

双水内冷同步调相机定子温度场分析

温度场的研究对双水内冷同步调相机安全运行具有重要的意义。针对双水内冷同步调相机,采用有限元法建立了电磁场二维模型以及流体-温度三维温升计算模型,求取了电机不同运行工况下的电枢电流、励磁电流以及对应的电机定子损耗。在此基础上,根据流体-温度耦合的传热理论,以定子线圈和铁心损耗为热源,求解定子各部分温度分布,研究电枢电流、冷却水流速、冷却水进水温度对定子温升的影响。结果表明,双水内冷同步调相机运行时定子下层线圈温度高于定子上层线圈温度,定子线圈最高温升与电枢电流的二次方呈正比,且其温升与冷却水的流速相关,与进水温度成正比。本文中关于温度场的研究可为大型同步调相机散热结构优化及过载能力分析提供理论参考价值。     

Multiscale modeling of biomedical, biological, and behavioral systems (part 2)

The six articles in this special issue focus on modeling at the macroscale end of the biological continuum, covering tissues, organs, and behavior.     

Structural, dielectric and conductivity studies of Na2Pb2La2W2Ti4Nb4O30 ferroelectric ceramic

A new single phase orthorhombic ferroelectric ceramic Na₂Pb₂La₂W₂Ti₄Nb₄O₃₀ (NPLWTN) was prepared via high-temperature solid-state reaction method. The grain morphology of the compound was analyzed by scanning electron microscopy (SEM). Studies of dielectric properties (??_r and tan??) of the compound at different frequencies (10²?C10⁶?Hz) in a wide temperature range (300?C700?K) showed multiple phase transitions in it. First phase transition observed at 335?K related to structural type (ferroelectric-ferroelectric) and the second one observed at 536?K is related to the ferroelectric to paraelectric. The ferroelectric property of the compound at room temperature was confirmed by polarization (hysteresis) study. Broadened dielectric peaks at low frequencies were observed above ferroelectric to paraelectric phase transition temperature (Tc). The values of exponent n(T) and pre-factor A(T) at and around Tc were obtained by the fitting ac conductivity data with Jonscher??s universal power law. From the variation of n(T) and A(T) with temperature, the strength of interaction among the charge carriers with the crystal lattice and the strength of polarisability at phase transition are observed. The activation energy of the compound in low and high temperature range suggests the conduction mechanism in the material.     

Chemical Processing and Properties of (Sr,Ca) 2 (Nb,Ta) 2 O 7 Thin Films

Ca-doped Sr 2 (Nb,Ta) 2 O 7 thin films have been synthesized by the chemical solution deposition. Homogeneous and stable (Sr,Ca) 2 (Nb,Ta) 2 O 7 precursor solutions were prepared by optimizing the reaction of starting metal alkoxides in ethanol with a key additive of 2-ethoxyethanol. The improvement of ferroelectric properties of the Sr 2 (Nb,Ta) 2 O 7 based films were achieved through the Ca substitution into Sr 2 (Nb 0.3 Ta 0.7 ) 2 O 7 as well as the optimization of heating conditions. The crystallization temperature of the layered perovskite (Sr 0.9 Ca 0.1 ) 2 (Nb 0.3 Ta 0.7 ) 2 O 7 thin films on Pt/Ir/Ti/SiO 2 /Si substrates was found to be above 750C. (Sr 0.9 Ca 0.1 ) 2 (Nb 0.3 Ta 0.7 ) 2 O 7 thin films crystallized at 750C exhibited P r of 0.51 w C/cm 2 and E c of 69 kV/cm.     

N_2、CO_2和SF_6喷口电弧电流开断能力的比较分析

文中研究了瞬态条件下电弧在3种不同气体中(N_2、CO_2和SF_6)熄弧时的形态及能量交换机理。首先根据实验结果对湍流电弧模型进行了严格校准、确认其适用性。在此基础上对3种电弧进行仿真计算,对计算结果进行能量守恒分析,指出了不同气体燃弧过程中对电弧特性起主导作用的能量输运机理。基于湍流电弧中径向温度分布曲线的特征,阐述并确认了喷口电弧的电流开断能力与气体的物性参数之间的内在联系。     

一起典型的特高压高阻接地故障分析及处理

通过对一起特高压交流系统中高阻接地故障的分析,有效辨别出两故障点是各自独立故障还是一起发展性故障,并且对保护装置动作过程进行详细分析,证明该合闸电阻继电保护配置及整定配合方案的合理性及可靠性,对类似故障的分析处理提供参考价值,对特高压合闸电阻继电保护设计具有借鉴意义。     

掺杂Co、Zn、Y氢氧化亚镍的合成与性能

采用均匀沉淀法制备了掺杂钴、锌、钇高比表面氢氧化亚镍,对该材料进行了SEM、XRD等结构测试及分析。测试了采用该氢氧化亚镍材料的氢镍电池性能。所制备的氢氧化亚镍为α-Ni(OH)2和β-Ni(OH)2的混合物,颗粒粒径为亚微米级。将该材料掺杂在普通球形氢氧化亚镍中作为碱性二次电池的正极材料制成氢镍电池,电池在容量、高功率性能、高温性能等方面都有所提高。     

Dielectric, thermal and sintering behavior of BaO-B2O3-SiO2 glasses with the addition of Al2O3

In the Pb-free low temperature sinterable glass of the (55)BaO-(35)B₂O₃-(10)SiO₂ system, different amounts of Al₂O₃ were added and the crystallization behavior, sintering behavior and physical characteristics of the glass were examined. It was found that Al₂O₃ suppressed crystallization of the glasses because it played the role of a network former. The glass transition temperatures, crystallization temperatures, and optimum sintering temperatures increased as the amount of Al₂O₃ increased. In the case of a specimen with a large amount of Al₂O₃, which was not easily crystallized, an over-firing phenomenon was observed when the sintering temperature was higher than the optimum sintering temperature. While the over-firing phenomenon was not observed due to the crystallization in the sample with a little amount of Al₂O₃. The dielectric constant and thermal expansion coefficient of the glasses were also examined and explained in correlation with the crystallization and densification.     

片式小型化二路功分器的设计优化与实现

传统的Wilkinson功分器使用微带电路结构,体积大、成本高,难以满足通信设备小型化的要求.本文通过对功分器的集中参数Wilkinson电路原型进行优化,提出了更利于小型化的电路结构,并对该电路进行了三维物理建模及电磁场仿真,确定了实现方案;采用低温共烧陶瓷(LTCC)技术实现了中心频率2.4GHz、相对带宽约20%的二路功分器,其尺寸只有2.6mm×2.0mm×0.8mm,实验结果与优化结果基本一致.     

Chemical processing and properties of Sr2(Ta,Nb)2O7 thin films

Abstract

The crystallographic orientation, microstructure and electrical properties of Sr₂(Ta, Nb)₂O₇ thin films strongly depended on the composition (Ta:Nb). Post-annealing at 850°C was effective for the improvement of some properties. The thin films with relatively Nb-rich compositions, such as Sr₂(Ta_0.6Nb_0.4)₂O₇ and Sr₂(Ta_0.5Nb_0.5)₂O₇, showed the (0k0) preferred orientation. The Sr₂(Ta_0.5Nb_0.5)₂O₇ thin film had a lamination layer structure after the post-annealing at 850°C for 6 min in oxygen. The characteristic microstructure originated in the crystallographic orientation of (0k0), which is the cleavage plane, and influenced electrical properties. The dielectric constant little change with the composition, however, the P-E hysteresis properties improved with the Nb content.     

Photoluminescence and photocurrent characteristics of Eu2 + activated MAl2O4 (M = Ba, Ca, Sr) phosphors

Photoluminescence and photocurrent characteristics of Eu^{2 +} activated MAl₂O₄ (M = Ba, Ca, Sr) phosphors during and after Ultraviolet ray and visible light irradiation have been investigated. The photoluminescence (PL) and the photocurrent (PC) of the phosphors, in order to elucidate the relationship between the PL and the PC, were measured simultaneously on the same samples within a specially designed measuring box. Composition effects, such as a presence of Dy^{3 +} as a co-activator and Al-rich composition on the PL and PC characteristics have been investigated. Also, sensing characteristics on UV and visual light have been tested. The simultaneous measurement of PL and PC on the same sample clearly indicated that the presence of co-activator and vacant site, namely Al-rich composition, acted as a hole trap; the introduction of co-activator and vacant site decreased the PC and increased the PL during and after UV and visible light irradiation, whose PC was much lower than that of MAl₂O₄ with only Eu^{2 +} as an activator. The electrical intensity affected on the PL characteristics after UV and visual light irradiation(afterglow); with increasing in the electrical intensity, the afterglow lasted more longer and intensively. The PC of MAl₂O₄ showed a good proportional relationship to UV and visible light intensity. Especially, SrAl₂O₄ showed an excellent linearity within 1–5 mW/cm², but showed somewhat delayed response and hysterisis as seen in CdS photoelectric cell.