接地与电气安全探讨

接地是电力系统中不可缺少的电气安全技术。接地是否合理,不仅影响电力系统的正常运行,而且也影响到人身安全。正确的接地方式和安全的接地装置,是保证电气安全的重要措施。     

Microstructure and mechanical properties of graphitic a-C:H:Si films

A series of graphitic a-C:H:Si films with different Si content were prepared by altering the sputtering current in a hybrid RF-PECVD and magnetron sputtering system. Microstructures and mechanical properties of them were characterized by IR, Raman, XPS, nanoindentation and scratch tests. Results show that although the sp³/sp² ratio increases with increasing Si content and as high as 8.2 at.% of silicon was doped, the a-C:H:Si films remain graphitic in nature and the I_D/I_G ratio is nearly constant for all. The coupling effects of sputtering-induced heating and strong ion bombarding due to negatively biasing were considered to be responsible for the film graphitization. The graphitic nature also accounts for the lower nanohardness of prepared a-C:H:Si films than the diamond-like a-C:H and a-C:H:Si films.     

Microstructure and magnetic properties of (0 0 1)-oriented L10 FePt films: Role of Ag underlayer and Fe/Pt ratio

FePt multilayer films were deposited on Si(1 0 0) substrate with thermally grown SiO₂ film and sputtered Ag underlayer at room temperature by dc magnetron sputtering and subsequently annealing in vacuum. Experimental results suggest that proper thickness of Ag underlayer and slightly rich of Fe content can effectively induce the (0 0 1) texture of FePt films. A Fe_57.4Pt_42.6 thin film on the 8 nm Ag underlayer exhibits a large perpendicular coercivity of 7.6 kOe with magnetic remanence close to 1.     

Compressive Viscoplastic Response of 6082‐T6 and 7075‐T6 Aluminium Alloys Under Wide Range of Strain Rate at Room Temperature: Experiments and Modelling

Abstract: In this work, the viscoplastic behaviour of 6082‐T6 and 7075‐T6 aluminium alloys is examined over a wide range of strain rates. Three different testing techniques were applied to this investigation: low‐rate experiments were performed using a regular servo‐hydraulic testing machine, high‐rate tests were conducted using a split Hopkinson bar apparatus and very‐high‐rate experiments were carried out using a miniaturised direct impact test arrangement. The latter testing set‐up allowed for the characterisation of material flow at strain rates up to . These experimental results showed a sharp increase in the rate sensitivity of the materials once a threshold loading rate of is exceeded. This behaviour may be attributed to the presence of viscous drag on high‐velocity dislocation motion. In addition, the thermo‐viscoplastic behaviour of the 6082‐T6 and 7075‐T6 aluminium alloys was analytically described using the extended Rusinek–Klepaczko model of viscous drag effects. Satisfactory correlation was observed between the experiments and the constitutive model results over the entire range of strain rates studied,      

Preparation of lipid aspirin sustained-release pellets by solvent-free extrusion/spheronization and an investigation of their stability

A novel solvent-free extrusion/spheronization technique was investigated for preparing stable aspirin sustained-release pellets. Lipids as binders and the matrix in this technique were extruded below their melting points, and spheronized in a thermomechanical process. Four types of lipids (adeps solidus, Compritol(?) 888 ATO, Precirol(?) ATO5 and Compritol(?) HD5 ATO) and their admixture in different ratios were used to obtain spherical and extended-release pellets. Pellets containing 80% aspirin, 15% adeps solidus and 5% Compritol(?) 888 ATO had the best spherical geometry and met the dissolution requirements of aspirin extended-release tablets in USP 31. Storage stability studies showed that the content of free salicylic acid increased sharply in the traditional pellets produced by wet extrusion/spheronization, from 1.91 to 7.84%, whereas there was little increase in the lipid pellets (from 0.48 to 1.08%). The dissolution rate from the optimal pellets (F11) stored at 26°C did not change, but became faster at 40°C/RH75% after 5 months. Powder X-ray diffraction, scanning electron microscopy (SEM) and differential scanning calorimetry were used to investigate the physical properties of the pellets during stability testing. The increase in the rate of drug release from aged pellets (40°C/RH75%) may result from the partially melted adeps solidus observed in SEM photographs. This study suggests that it is possible to prepare sustained-release pellets by solvent-free extrusion/spheronization using an appropriate mixture of lipids with high stability. In particular, this novel technique is excellent for hygroscopic drugs.     

Effects of Temperature on Release of Eugenol and Isoeugenol from Soy Protein Isolate Films into Simulated Fatty Food

Soy protein isolate (SPI)–based cast films were incorporated with eugenol and isoeugenol. The release of eugenol and isoeugenol from the SPI films into simulated fatty food (olive oil) at 5°C, 20°C, 40°C and 60°C was determined by high performance liquid chromatography (HPLC) to investigate the effect of temperature on the said release. The partition coefficients decreased linearly with temperature in the range of 5°C–60°C. Diffusion coefficients of eugenol and isoeugenol in the SPI films were determined by fitting the model to the experimental data. The linear relationship between the logarithm of the diffusion coefficient and temperature indicated that the release of eugenol and isoeugenol from SPI films into olive oil followed the Arrhenius equation. The comparison of release of eugenol and isoeugenol between the prediction and the experiment at 30°C was made, and a good agreement was obtained. The activation energies for the release of eugenol and isoeugenol were 52.4 and 53.9 kJ/mol, respectively. Copyright © 2012 John Wiley & Sons, Ltd.     

聚四氟乙烯无机纳米复合材料的研究进展

无机纳米粒子填充的聚四氟乙烯(PTFE)复合材料因其独特的性质受到广泛关注。综述了无机纳米粒子填充改性聚四氟乙烯复合材料的研究进展。重点介绍了无机纳米粒子的大小、粒子表面修饰、粒子的晶体形态以及粒子混合方式等因素对复合材料特性的影响,并对聚四氟乙烯无机纳米复合材料研究的发展趋势进行了展望。     

地板辐射采暖地面散热量的简化计算方法

对加装了地板辐射采暖设施的空间采用三维稳态湍流模型,进行空气流动和传热特性的数值研究,并在与实验数据相比较的基础上,提出了一个便于实施计算的地板表面散热量的简化计算方法.提出的简化计算方法的思路即是对原计算公式中难以确定的房间内非加热表面的面积权重平均温度值Tp,用室温的修正量来代替.研究结果表明,数值结果和实验数据吻...     

Improved electrical and reliability characteristics in metal/oxide/nitride/oxide/silicon capacitors with blocking oxide layers formed under the radical oxidation process

We propose a Metal-Oxide-Nitride-Oxide-Silicon (MONOS) structure whose blocking oxide is formed by radical oxidation on the silicon nitride (Si3N4) layer to improve the electrical and reliability characteristics. We directly compare the electrical and reliability properties of the MONOS capacitors with two different blocking oxide (SiO2) layers, which are called a "radical oxide" grown by the radical oxidation and a "CVD oxide" deposited by chemical vapor deposition (CVD) respectively. The MONOS capacitor with a radical oxide shows a larger C-V memory window of 3.6 V at sweep voltages from 9 V to -9 V, faster program/erase speeds of 1 micros/1 ms at bias voltages of -6 V and 8 V, a lower leakage current of 7 pA and a longer data retention, compared to those of the MONOS capacitor with a CVD oxide. These improvements have been attributed to both high densification of blocking oxide film and increased nitride-related memory traps at the interface between the blocking oxide and Si3N4 layer by radical oxidation.