Evaluation of atmospheric galvanic aluminum corrosion in electrical transmission towers at different sites in the Valparaíso region,Chile. Wire-on-Bolt Test (CLIMAT)

This study evaluates environmental aggressiveness and atmospheric galvanic corrosivity categories in Chile (Classification of Industrial and Marine ATmospheres test) by installing bolts in electrical transmission towers in the Valparaiso region across four exposure sites: Playa Ancha, San Sebastián, Las Vegas, and San Felipe. Classifications of marine corrosion index (MCI), industrial corrosion index (ICI), and atmospheric corrosion index (ACI) used different galvanic couples: aluminum/steel for MCI, aluminum/copper for ICI, and aluminum/polyethylene for ACI. Corrosion indices varied by season (summer, autumn, winter, and spring), for which couples were exchanged every 3 months. Intraseason variation depended mainly on the meteorochemical variables of the zone, the Cl⁻/SO₂ ratio, and the presence of general and pitting corrosion in the aluminum. The results indicate that, regardless of environmental condition, the aluminum in Al/steel (MCI) and Al/copper (ICI) couples presented a higher corrosion rate than when not forming a galvanic couple (ACI). Moreover, under higher environmental chloride, these differences increase. The Playa Ancha station presented the highest ACI.     

电气设备接地装置的运行与维护探讨

随着现代化进程的加快,电气设备接地装置的应用越来越广泛,从安全的角度考虑,其运行和维护受到了全社会的广泛关注,如何介绍应用当中存在的安全隐患成为当前关注的主要内容。本文系统概括的分析了电气设备接地装置的运行和维护情况,为其安全应用提供一定的参考。     

高压气淬设备与工艺

简要介绍了气体淬火介质及ECM气体淬火设备的特性,同时介绍了ECM气体分级淬火工艺的原理,并结合实际生产案例,论述了分级气淬工艺较普通气淬工艺的优越性。     

聚乙烯醇对芳纶复合纱聚苯胺导电层耐久性影响

为提高聚苯胺导电层与基材之间的黏结牢度,以聚乙烯醇为共混高聚物,通过连续原位聚合法在对位芳纶纱线表面形成聚乙烯醇/聚苯胺导电层,制备得到芳纶/聚苯胺/聚乙烯醇复合导电纱。分析了导电纱的结构与性能,并研究了聚乙烯醇对聚苯胺导电层耐水洗和耐磨性的影响。结果表明:适量添加聚乙烯醇有助于提高导电纱导电层的结构规整性及电导率,随着聚乙烯醇质量分数的提高,导电纱的电导率呈先上升后下降的趋势,当聚乙烯醇占苯胺的质量分数为4.30%时,制得的复合导电纱线的电导率最高,达到(1.120±0.198) S/cm;聚乙烯醇的添加和质量分数的提高,有助于聚苯胺导电层耐水洗性及在较小外力作用下的耐磨性的提高。     

Investigation of structural,optical, electrical,and magnetic properties of Fe-doped La0.7Sr0.3MnO3 manganites

In this work, the physical properties of nanocrystalline samples of La_0.7Sr_0.3Mn_1−xFe_xO₃ (0.0 ≤ x ≤ 0.20) perovskite manganites synthesized by the reverse micelle (RM) technique were explored in detail. The phase purity, crystal structure, and crystallite size of the samples were determined using X-ray diffraction (XRD) and Fourier transform infrared (FTIR) spectroscopy. All the samples had rhombohedral crystal structure and crystallite size increased with increase in Fe content in La_0.7Sr_0.3MnO₃. The scanning electron micrographs (SEMs) exhibited smooth surface morphology and nonuniform shape of the particles. The optical properties studied using UV-visible absorption spectroscopy revealed a decrease in the absorbance and optical band gap with an increase in Fe content in La_0.7Sr_0.3MnO₃ compound. The temperature-dependent resistivity measurements revealed semiconducting nature of x = 0 and 0.1 samples up to the studied temperature range, while a metal-to-insulator transition was observed at higher Fe doping. Magnetic studies revealed weak ferromagnetism in all the samples and a reduction in the maximum magnetization with an increase in Fe content. A close correlation between electrical transport and magnetic properties was observed with the doping of Fe ion in La_0.7Sr_0.3MnO₃ at Mn site. These results advocate strong interactions associated with the double exchange mechanism among Fe³⁺ and Mn³⁺ ions.     

等温退火对8030铝合金导线组织性能的影响

研究了不同等温退火工艺对8030铝合金导线组织及性能的影响。结果表明:等温退火前后合金均由α-Al基体和Al₆Fe相组成。在同一等温温度下,随着等温时间的延长组织逐渐趋于均匀化;同一等温时间下,随着等温温度的升高,组织趋于均匀化的时间缩短。经过等温退火处理后铝合金导线的导电率均有所提高,在470 ℃均匀化退火24 h后再经240 ℃等温4 h,合金导电率达到最高值57.21%IACS,比未经热处理试样的导电率提高了2.4%IACS。经过等温退火处理后铝合金导线的硬度及抗拉强度均有所降低,塑性大幅度提高。在470 ℃均匀化退火24 h后再经260 ℃等温8 h,合金的伸长率最高可达23.64%。热处理前后合金均为塑性断裂。     

矿用直线振动筛结构故障分析

针对煤矿选煤厂直线振动筛工作过程中出现的结构故障问题,采用有限元仿真与现场测试结合的方法对振动筛出现故障的原因进行了分析研究。介绍了振动筛的主要结构及常见故障,并以某矿选煤厂发生大梁断裂的振动筛为例,对该振动筛进行三维建模和有限元模态分析,分析结果表明:随着模态阶次的增加,振型的变化逐渐由移动转为结构本身的扭曲变形。在该振动筛空载工作状态下,选用本质安全型便携式测振记录仪进行振动测试并处理测试信号,得到该振动筛的工作频率。结合模态分析结果和实际测试结果,判断出空载时频繁运行振动筛是造成其大梁断裂的主要原因。根据故障原因给出维护建议:应当尽量避免振动筛在空载或物料较少的状态下长时间运行;在振动筛投入使用前,应预先了解振动筛的工作状态及可能存在的薄弱环节,尽可能避免结构故障,保证振动筛可靠运行。     

单晶SiC的电助光催化抛光及去除机理

为满足电子半导体等领域对SiC超光滑、无损伤和材料高效去除的要求，提出了电助光催化抛光SiC的新方法。研究了光催化剂种类及其pH值对抛光液氧化性和抛光效果的影响，讨论了材料的去除机理。结果表明：以p25型TiO2为光催化剂配制抛光液所获得的最大氧化还原电位为633.11 mV，材料去除率为1.18 μm/h，表面粗糙度Ra=0.218 nm；抛光后SiC表面氧化产物中，Si-C-O、Si-O和Si4C4O4的含量明显增加，SiC表面被氧化并被机械去除是主要的材料去除方式。     

An up to date review of continuously variable speed wind turbines with mechatronic variable transmissions

As a promising and potential alternative to conventional fixed or variable speed wind turbines, continuously variable speed wind turbines (CVSWTs) with variable transmissions offer improved power efficiency and enhanced power control capabilities. The CVSWTs can be generally achieved by adapting mechatronic variable transmissions in the turbine drive train for continuously variable speed operations for wind turbines. Therefore, this paper serves to provide an up to date and exhaustive review of the CVSWTs with mechatronic variable transmissions such as mechanical variable transmission, electrical variable transmission, and power splitting transmission. In this paper, the analysis of CVSWTs with different mechatronic transmission topologies is performed regarding basic configurations, dynamic characteristics, control principles, and experimental or simulation results. Review results indicate the feasibility of applying CVSWTs with such mechatronic transmissions and highlight superiorities of the CVSWTs with power splitting transmission. The CVSWT with power splitting transmission will be particularly suitable for megawatt‐scale turbine systems and will hence increase the economic competitiveness of these turbines due to its large power capacity and high reliability. The directions or challenges for future investigations of CVSWTs with such mechatronic transmissions are also presented to foster in‐depth understanding of such CVSWTs and their control strategies.