Breakdown characteristics of oil and paper insulation for a very fast transient voltage

This paper describes the dielectric breakdown characteristics of oil and oil‐impregnated paper for very fast transient (VFT) voltages. Blumlein circuits generate VFT voltages of 60 and 300 ns in a pulse width that simulates disconnecting switching surges in gas‐insulated switch gears. We measured the breakdown voltages of needle‐to‐plane, plane‐to‐plane oil gaps and several pieces of paper between plane electrodes for VFT and lightning impulse voltages. The measured data were formulated in V‐t characteristics and Weibull probability distributions. The inclination n of V‐t characteristics of insulating paper is 150, which is less than n = 13.7 of the plane‐to‐plane oil gap in the VFT time range. The shape parameters of Weibull distribution obtained in this study show that the scattering of breakdown voltages of paper is much less than that of oil. © 2002 Wiley Periodicals, Inc. Electr Eng Jpn, 141(4): 16–24, 2002; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/eej.10043     

V. Yeast sequencing reports. Identification of a gene encoding a new Ypt/Rab-like monomeric G-protein in Saccharomyces cerevisiae

A Saccharomyces cerevisiae sequence cloned by serendipity was found to encode a protein that is a new member of the Ypt/Rab monomeric G-protein family. This sequence shows high homology to the yeast genes SEC4 and YPT1 and, like SEC4 and YPT1, is essential for viability. The sequence was localized to chromosome V based upon hybridization to pulse-field gel-separated yeast chromosomes. The sequence has been deposited in the GenBank data library under Accession Number L17070.     

Genetic and physical mapping of the WBP1 locus close to CENV.

The WBP1 locus, encoding an essential component of the N-oligosaccharyl transferase, was mapped both genetically and physically. The gene is located on chromosome V between CENV and gcn4. The distance from CENV sequences is 2 kb.     

Infrared heat treatment of Ti-6Al-4V with electroplated Cu

The objective of this study is to investigate an innovative infrared (IR) technique to enhance adhesion of electroplated copper (Cu) on Ti-6Al-4V without dichromate dipping. The ultimate goal is to develop a Cu coating process on Ti-6Al-4V without hazardous hexavalent chromium (Cr) solution treatments. Cu coatings of around 50 μm were electroplated on Ti-6Al-4V specimens at a current density of 0.03 A/cm² in an acidic Cu solution. To improve adhesion of coatings, IR heat treatments were performed on the Cu-coated samples at different temperatures and durations: 860 °C for 600 s and 875 °C for 20–120 s. This process was accomplished in an attempt to replace the use of dichromate dipping before electroplating. For samples heat treated at 860 °C, no bonding existed, even after 600 s. It is believed that solid-state diffusion prevailed at 860 °C and that 600 s was not enough for sufficient diffusion to occur. Adhesion was poor when samples were heat treated at 875 °C for 20 s. Excellent adhesion was observed when the heat treatment holding time was increased to 40 s. For 90 s, the surface appearance of coatings partially changed from Cu-colored to a grayish color. There was no Cu left on the surface after a 120 s heat treatment. From optical microscopic observations on sample cross sections, an interlayer between the Cu and Ti-6Al-4V formed when heat treated at 875 °C for 40 s and longer. The interlayer thickness increased as the holding time increased, until depletion of Cu. The sheet resistivity of coated specimens was on the order of pure Cu for samples heat treated at 875 °C and less than 90 s. During the 875 °C heat treatment, the following occurred: solid-state diffusion of Cu in Ti-6Al-4V, formation of eutectic solutions, dissolution of Cu and Ti-6Al-4V into the liquid phase, and the formation of intermetallic compounds. The lowest eutectic temperature of 875 °C played a key role in this innovative process of Cu coating on Ti-6Al-4V. This paper was presented at the 2nd International Surface Engineering Congress sponsored by ASM International, on September 15–17, 2003, in Indianapolis, Indiana and appears on pp. 403–10 of the Proceedings.     

ZTC4筒形件温成形扩口数值模拟

对铸造Ti-6Al-4V筒形件温成形扩口成形工艺进行了数值模拟分析,得出了优化的工艺参数,并对凸模锥角进行了优化模拟,得出了合适的锥角。     

一种环保化学储能电池——钒氧化还原液流电池

可再生能源需要性能优良的储能电池与之配套，因此，研究和开发价廉、高效率的储能系统是十分必要的。本文通过介绍钒氧化还原液流电池的原理和特点，指出钒电池是一种潜力巨大的新型环保储能电池。同时介绍钒电池制备和应用时的三大技术关键及一定的解决方法。     

SPI接口以太网控制器ENC28J60及其应用

目前大多数以太网控制器都是为个人计算机而设计的,在精简的嵌入式系统中使用比较繁杂,常常需要采用扩展总线的方式,本文介绍了全球目前最小封装的以太网控制器ENC28J60,由于采用SPI串行接口方式,简化了设计,本文介绍了其特性、内部结构和引脚功能,详细分析了其寄存器设置和工作过程,给出了与微控制器接口的应用电路。     

橡塑磁条在永磁音像微特电机中的应用

本文简述了橡塑磁条的制造工艺及在永磁音像电机规模生产中的应用，与铁氧体烧结磁环进行比较，阐述了橡塑磁条在音像微特电机中使用的优势。     

Structural and electrochemical properties of vanadium oxide thin films grown by d.c. and r.f. reactive sputtering at room temperature

Vanadium oxide thin films were grown at room temperature by direct current and radio-frequency reactive sputtering systems to compare the structural and electrochemical properties. Rutherford backscattering spectrometry and Fourier transform infrared measurements reveal that the composition of the as-deposited films consists of the V₂O₅ phase regardless of the deposition methods. Wide-angle X-ray diffraction measurements show that the crystallinity of the as-deposited V₂O₅ films is different depending on the deposition method. Films deposited by direct current reactive sputtering were amorphous, whereas films deposited by radio-frequency reactive sputtering were crystalline. Scanning electron microscopy measurements show that the V₂O₅ films grown by radio-frequency reactive sputtering had a large grain size but the films grown by direct current reactive sputtering were amorphous. Charge–discharge measurements taken at room temperature with a constant current clearly indicate that the films grown by direct current sputtering demonstrated typical amorphous behavior, whereas the V₂O₅ films grown by radio-frequency sputtering demonstrated the discharge behavior of crystalline V₂O₅. The origin of the structural and electrochemical properties of film grown by radio-frequency reactive sputtering is a self-bias effect. The self-bias effect induces ion bombardment during the growth of vanadium oxide thin film. These results suggest that direct current reactive sputtering is more desirable for growing amorphous V₂O₅ thin film than radio-frequency reactive sputtering.     

Microstructure developed in the surface layer of Ti-6Al-4V alloy after sliding wear in vacuum

Microstructural changes in the surface layer of Ti-6Al-4V alloy after sliding wear in vacuum have been studied by means of scanning and transmission electron microscopy (SEM and TEM). The wear rates of Ti-6Al-4V alloy in vacuum were measured under different sliding velocities and loads. The experimental results showed that a severely deformed layer with a grain size of 50–100 nm and thickness about 70 μm was formed underneath the worn surface. Under the slower sliding velocities, the substructure of the layer had a high dislocation density, while under higher sliding velocities, twins were found to exist in the substructure. A process by which the deformed layer formed has been proposed and the deformation of materials at the contacting spots of the Ti-6Al-4V sample is discussed.