Characterization of functionally gradient epoxy/carbon fibre composite prepared under centrifugal force

Centrifugal force was employed in order to induce a spatial gradient of fibre distribution in the epoxy/carbon fibre system. The gradient structure of the epoxy/carbon fibre composite can be controlled by varying the rotation time and the material parameters, such as fibre length, fibre content and matrix viscosity. The spatial gradient distribution of carbon fibres in an epoxy matrix was achieved by the combined mechanism of packing and settling. The mechanical properties of the functionally gradient epoxy/carbon fibre composite were also investigated. At the same content of carbon fibre, the flexural strength of the functionally gradient composite was higher than that of conventional isotropic composite. This revised version was published online in November 2006 with corrections to the Cover Date.     

SYNERGISM OF CRANBERRY PHENOLICS WITH ELLAGIC ACID AND ROSMARINIC ACID FOR ANTIMUTAGENIC AND DNA PROTECTION FUNCTIONS

Several studies have shown the antimutagenic DNA protective functions of some naturally occurring phenolic phytochemicals. Emerging research also indicates that synergistic functionality of these phytochemicals in whole foods benefits the management of many diseases. Here we have investigated the potential antimutagenic properties of cranberry phenolics, ellagic acid (EA), rosmarinic acid (RA) and their synergistic interactions on enhancing antimutagenic properties in Salmonella typhimurium tester system against mutagens sodium azide and N‐methyl‐N′‐nitro‐N‐nitrosoguanidine. Ability of these phytochemical treatments to protect oxidative damage to DNA was also investigated using the supercoiled DNA strand scission assay. Results showed that EA was most effective in inhibiting the mutations in S. typhimurium system, whereas RA and EA were equally effective in protecting the DNA from oxidative damage. Results also showed that the antimutagenic functionality of cranberry powder (CP) made from juice extracts was significantly enhanced when 30% (w/w) of phenolics in CP was substituted with RA and EA possibly because of synergistic redox modulation that can influence mutagen function. It is also suggested that the synergistic mixture of cranberry phenolics with RA could also be protecting the cell from mutations by modulating DNA repair systems.     

热子及热子组合件的常见问题及解决方法

介绍了阴极加热所用的各种热子及热子组合件,分析了实际应用过程中的常见问题,研制了更加可靠和具有快热性能的熔融热子组件。     

钢芯铝型线绞线与钢芯铝绞线的主要性能对比

提出了导线截面利用率的概念,基于S、Z铝型线导体,给出了几种与常用规格圆线同心绞钢芯铝绞线对应的型线同心绞钢芯铝型绞线,将两者的部分基本参数和特性作了对比。结果表明:型线同心绞的钢芯铝型线绞线比圆线同心绞钢芯铝绞线的导体截面利用率约高15%,若截面积相等,钢芯铝型线绞线的直径约减小9%,其他性能几乎相同;若两者直径相等,则钢芯铝型线绞线的导体截面积、单位质量和抗拉力较大,同时直流电阻减小而载流量增大。钢芯铝型线绞线的安装可采用常规金具,具有一定的缓覆冰性能和较好的弧垂特性,将是输电线路使用中的一种重要线种。     

半导体芯片银凸点微电极生长技术

银点微电极生长技术主要用于ISS181系列高压超高速开关二极管的电极成型,是一项制约ISS181封装国产化的瓶颈技术。该项目研究采用了自主开发的流动独立供液、独立供电,整体控制工艺,用于100 mm芯片电极成型,保证银凸点微电极高度40 靘,误差?5%。做到微区银点生长有效控制,大面积一致性好。在流量8 L/min,电压6.5 V,占空比10%的条件下,得到了最佳结果。     

Torsional vibration analysis of lathe spindle system with unbalanced workpiece

For the purpose of analyzing the torsional vibration caused by the gravitational unbalance torque arisen in a spindle system when it is machining heavy work piece, a 10-DOF lumped parameter model was made for the machine tool spindle system with geared transmission. By using the elementary method and Runge-Kutta method in Matlab, the eigenvalue problem was solved and the pure torsional vibration responses were obtained and examined. The results show that the spindle system cannot operate in the desired constant rotating speed as far as the gravitational unbalance torque is engaged, so it may cause bad effect on machining accuracy. And the torsional vibration increases infinitely near the resonant frequencies, so the spindle system cannot operate normally during these spindle speed ranges.     

Calculation of optimal current density of double side permanent magnet linear synchronous motor

The use of design method considering a coil temperature to maximize the thrust density of a double side coreless permanent magnet linear synchronous motor (PMLSM) was presented. The optimal current density where the coil temperature reaches an allowable temperature with heat analysis was applied to a magnetic circuit design. Changing optimal current density is verified whenever the design parameters of the motor are altered. The design parameters of the motor were applied to thrust calculation. In this way, the optimal model, which is a reversal of the existing design method, is deduced. The results were compared with the experimental data to verify their validity. When the convection heat transfer coefficient is applied to other models, the results of the analysis and test values show good concordance. The method proposed has some limitations.     

Optimal design of auxiliary-teeth to solve circulation current reduction of permanent magnet linear synchronous motor

A discontinuity of magnetic circuits according to the end effect is generated in the permanent magnet linear synchronous motor (PMLSM).Due to the unbalanced back electro-motive force (EMF) and impedance produced,unbalanced current is generated.The circulating current,which is caused by a decrease in the thrust,is generated by the unbalanced current.The optimal design of auxiliary-teeth at the end of the mover was carried out to solve the unbalance of phase by using design of experiment (DOE),and compared wi...     

脉冲溢出型DDS输出信号频谱分析

脉冲溢出型DDS利用相位累加器的溢出信号作为输出信号,很容易用FPGA器件实现,但它输出的脉冲信号存在相位抖动的缺点.作者根据脉冲溢出型DDS的工作原理对其输出脉冲信号的抖动进行了理论分析,得到了输出脉冲信号的频谱表达式,并给出了计算机仿真结果.     

Optical properties of Eu2+-doped strontium borate glasses containing F- and Li+ ions

In this experiment, strontium borate glasses were prepared using the conventional quenching method in air atmosphere. Optical absorption, photoluminescence excitation and emission spectra, X-ray excited luminescence (XEL), and luminescence decay curve of the as-prepared glasses were investigated at room temperature. The as-prepared glasses had two kinds of Eu ions, i.e., Eu2 and Eu3 . Compared with the reported results of strontium borate glasses, Eu2 luminescence was enhanced in the studied strontium borate glasses coprepared with F- and Li ions. The coexisting of Li or F- in the borate glasses could create more negative defect VSr″ and stabilize Eu2 ions, which might act as donor of electrons;For the F- doping, the new center of B(O, F)4 (or BO3F) and BO2F2 units could be considered to be the distorted (BO4), which were needed as a rigid framework to stabilize the divalent rare earth ions.