方波脉冲电压下聚酰亚胺薄膜老化特征研究

针对脉宽调制(PWM)技术在电力机车变频调速应用中,导致电机绝缘在连续脉冲电压下过早老化的问题,对变频电机绝缘主要材料聚酰亚胺薄膜进行方波脉冲电压下的电老化试验.通过对不同老化阶段聚酰亚胺薄膜tanδ的测量,从介质损耗规律方面对材料在脉冲电压下老化特征进行研究.结果表明,在不同的老化阶段,介质损耗随电压、频牢的变化趋势保持一致,介质损耗随老化时间的增加而变大;老化使聚酰亚胺薄膜的起始放电电压降低,介质损耗随电压增加而增大的趋势更加明显;聚酰亚胺薄膜的介质损耗在高频区的激增点会随着老化时间的增加而向高频区移动.     

纳米颗粒对聚酰亚胺膜老化特性的影响

为了研究高频方波脉冲电压下高速铁路牵引电机绝缘的老化、失效机理,给电机绝缘结构的设计和优化提供理论基础,本文研究了高频方波脉冲下牵引电机定子绝缘的老化特性。在高频方波脉冲下,对普通和纳米复合薄膜进行了老化,通过扫描电镜分析了试样表面形貌的变化情况,并对试样的剩余击穿场强进行了测试分析。研究表明:老化1小时后两种薄膜的表面形貌都发生了明显改变但变化不同,纳米粒子的添加延缓了局部放电对纳米复合薄膜的老化速率,老化2小时后普通薄膜和纳米复合薄膜的击穿场强分别下降了27.55%和12.90%。     

内径20mm导向套筒内壁处理（2）：空心阴极混合气体放电特性研究

针对高端阀门内径20mm导向套内壁DLC处理,采用高频高压脉冲电源,分别研究了氩气和混合气气氛下脉冲电压、脉宽、频率以及工作气压等参数对管内空心阴极放电伏安特性的影响规律。结果表明:轴向对齐的五个小管内均实现了空心阴极放电,氩气条件下放电电流表现出明显空心阴极放电特征,而混合气条件下电流幅值较为平整。脉冲电压或气压的提高有利于提高放电电流,而脉冲频率的增加会使得峰值电流略有下降,脉宽的增加使得单纯氩气条件下电流峰值逐渐增加,而对于混合其他条件下的峰值电流影响不大,仅使平均电流增加。固定气压10Pa条件下,乙炔流量的变化对放电电流的影响不大,有利于扩大DLC薄膜沉积的工艺窗口范围。以上研究结果为高端阀门小直径导向套等内壁DLC薄膜制备提供工艺基础。     

内径20mm导向套筒内壁处理(1):空心阴极氩气放电特性研究

针对高端阀门内径20mm导向套内壁处理,采用高频高压脉冲电源,研究了氩气气氛下工作气压、脉冲电压和频率等参数对导向套空心阴极放电伏安特性的影响,并对工件间距及与阳极距离等放电结构进行了研究。结果表明:管内空心阴极放电需要一个稳定过程,脉冲电流随着时间的增加逐步降低,而后达到稳定放电阶段。提高脉冲电压或工作气压,管内空心阴极脉冲峰值电流增加。脉宽或频率的增加,脉冲峰值电流不变,但平均电流增加,且频率的增加使得激励时间减少。放电结构的分析表明,管间距的减少,放电电流变化不大,而管口与阳极之间距离的减少,使得放电峰值电流略有增加。以上研究结果为高端阀门小直径导向套等内壁薄膜制备提供了有效指导。     

耐电晕复合绝缘材料的研究

介绍了利用原位聚合法制备了纳米TiO2/聚酰胺酰亚胺复合绝缘漆,与聚酯亚胺底漆和聚酰胺酰亚胺面漆配合,涂制成三层结构的复合绝缘材料.试验结果表明,这种复合绝缘材料具有高绝缘性能、柔韧性好、耐电晕性能高等特点,应用在交流变频电机中,可使高压脉冲下的局部放电、介质发热和空间电荷积聚等得到明显缓解,大大提高了交流变频电机的绝缘寿命.     

聚酰亚胺/二氧化钛纳米复合薄膜制备与耐电晕性

采用原位聚合法制备不同TiO2组分聚酰亚胺(PI)/纳米TiO2复合薄膜,薄膜厚度50μm。测试结果表明,TiO2呈球状颗粒,直径约为100 nm,聚酰亚胺呈片状,尺寸约为2μm×1μm。随着TiO2含量的增加,复合薄膜介电常数和介电损耗增大,击穿场强先增加后降低;在40 kV/mm电场强度下,复合薄膜耐电晕老化寿命增加,纯PI薄膜寿命为3 h,20wt%TiO2含量薄膜寿命达到25 h;TiO2颗粒耐电晕能力强,与聚合物形成界面相,改变材料陷阱能级,有利于空间电荷的扩散和热量的传输,在薄膜表面形成放电阻挡层,降低局部放电对薄膜内部的侵蚀,显著提高薄膜耐电晕老化寿命。     

RF—PECVD聚合类聚乙烯氧（PEO—like）薄膜及其对血小板吸附性研究

本文采用平板式电容耦合射频(RF,13.56MHz)等离子体源,以乙二醇二甲基醚(Ethylene Glycol DiMethyl Ether)为聚合单体,氩气为辅助气体,在连续与脉冲射频等离子体两种放电模式下合成类聚乙烯氧(PEO-like)功能聚合薄膜.实验研究了等离子体放电参数:等离子体放电功率、工作气压、放电模式(连续或脉冲)和聚合时间等对聚合物表面结构、功能团含量、表面成分性能以及和血小板吸附等影响.利用接触角测定仪(WCA)、傅里叶变换红外光谱(FTIR)、原子力显微镜(AFM)等手段对聚合薄膜的结构、成分和形貌进行细致的分析.同时本文还进行体外细胞培养法,研究了类PEO功能薄膜对富血血小板的吸附,通过倒置显微镜观察细胞黏附的数量和形态变化.得到的结论为:采用RF-PECVD可以在较小功率的连续等离子体放电模式,或较长脉冲间隔的脉冲放电模式下得到结构稳定的PEO生物功能薄膜,所制备的PEO生物功能薄膜具有良好的抗血小板吸附性能.     

中频DBD等离子体聚合马来酸酐薄膜的研究

用马来酸酐乙醇溶液为单体,采用脉冲介质阻挡放电(DBD)合成聚马来酸酐薄膜,研究了放电的不同频率,聚合的区域对聚合薄膜性能的影响。通过对薄膜性能的表征:接触角、红外光谱、表面形貌、薄膜厚度,发现在频率为80 kHz,气压50 Pa能聚合表面连续致密的聚马来酸酐薄膜,薄膜的生长速率为8 nm/min。     

笼网型空心阴极氩气放电特性研究

采用高功率脉冲电源,研究了氩气气氛下工作气压、脉冲电压和频率等参数对笼网型空心阴极放电特性的影响,并对等离子体发射光谱进行了分析。结果发现:在脉冲电压增加到一定程度,脉冲电流随时间呈指数型(n1)激增。提高工作气压、脉冲频率及脉冲电压,笼型空心阴极放电增强。脉冲峰值电流随气压和脉冲电压的升高而增大,但随频率增大呈现降低趋势。光谱分析表明,氩气笼型空心阴极放电主要物种是Ar*和Ar+粒子,随脉冲电压、工作气压及频率的增大,Ar*和Ar+粒子数量增多。     

30kV高压脉冲电源及其废水降解电离试验

根据高压间隙放电的特性,设计了一种频率可调的高压脉冲电源.试验表明,高压脉冲电源输出电压可达30kV,频率范围为10～200Hz,应用于难降解有机废水的高压电离处理及与臭氧协同处理中,取得了较好的效果.     

Estimation of Parameters of Universal Distribution of Moments of Failure of Products

A method is proposed for estimating the parameters of a mixture of exponential and Weibull distributions for which the accuracy of preliminary estimates obtained by graphical analysis is refined in accordance with the criterion of maximum likelihood. The efficiency of the proposed method is supported by the results of statistical modeling.     

Assessment of intakes of mixtures of radionuclides

Australia has several uranium mines and a large number of mineral sand mines, with associated processing facilities. Exposures resulting from these mining and processing operations usually involve intakes of mixtures of radionuclides. This work describes the development of a suite of first order, linear compartment models, based on the ICRP Publication 66 respiratory tract model, and an analytical solution to the decay equations, for assessing the consequences of such intakes. The computer programs based on these models directly compute excretion, organ retention and organ and whole-body doses for intakes of either single radionuclides or any mixture of radionuclides belonging to the same radioactive decay chain. The intake can be via inhalation, ingestion or injection, and can be acute, chronic or of limited duration. The starting concentration and degree of secular (dis)equilibrium can be specified for each radionuclide. No assumptions need to be made about the relative magnitudes of the radioactive half-lives of the different nuclides.     

Analysis of anisotropy of properties on the basis of studies of texture of coarse-grained ingots of thermoelectric materials

An analysis of anisotropy of the properties of a Bi₂Se_0.3Te_2.7 solid solution was carried out using construction of demonstrative surfaces for thermoelectric effectiveness and thermal expansion coefficients. It is shown that the texture is an important factor forming anisotropy of properties and technological fitness of ingots for manufacturing modules. Anisotropy of properties based on the studies of the ingot textures obtained using the float-zone method and Bridgman method (growing thermoelectric plates in a flat cavity) was studied.     

Evaluation of optical properties of highly scattering media by moments of distributions of times of flight of photons

A novel method for the determination of the optical properties of tissue from time-domain measurements is presented. The data analysis is based on the evaluation of the first moment and the second centralized moment, i.e., the mean time of flight and the variance of the measured distribution of times of flight (DTOF) of photons injected by short (picosecond) laser pulses. Analytical expressions are derived for calculation of absorption and of reduced scattering coefficients from these moments by application of diffusion theory for infinite and semi-infinite homogeneous media. The proposed method was tested on experimental data obtained with phantoms, and results for absorption and reduced scattering coefficients obtained by the proposed method are compared with those obtained by fitting of the same data with analytical solutions of the diffusion equation. Furthermore, the accuracy of the moment analysis was investigated for a range of integration limits of the DTOF. The moment analysis may serve as a comparatively fast method for evaluating optical properties with sufficient accuracy and can be used, e.g., for on-line monitoring of optical properties of biological tissue.     

Analysis of the rate of propagation of the wave of change of boiling modes

An approximate analytical expression is derived for the velocity of the front of the wave of change of boiling modes on a rod and on a plate. The impact of the Thomson effect and of the heater orientation in the gravity field is included. Adequate agreement is demonstrated between the derived relations and experimental data.     

卧式金属罐容量的测量结果不确定度

本文根据多年的实践检定经验 ,参照JJF1 0 59- 1 999《测量不确定度评定与表示》以及《测量不确定度表达 1 0讲》 ,对卧式金属罐容量的测量结果不确定度进行了评定。     

盐酸浓度不确定度的评估

通过对盐酸浓度标定的过程分析，找出影响结果的各个分量，进行不确定度的评定，按照计量技术规范给出标准的表示法。