非线性宽频压电振动能量采集器的研究

为改善双稳态压电振动能量采集器在基础低幅值激励条件下的输出性能,提出了一种带有线性放大器的非线性宽频压电振动能量采集器,通过线性放大器对基础低幅值激励进行一级放大后,激发双稳态压电振动能量采集器进入高能轨道的大幅值周期振动,从而提高能量采集器的输出性能。根据力学和电学平衡方法建立了非线性宽频压电振动能量采集器的两自由度集总参数模型和运动微分方程,并对系统模型进行时域和频域求解,仿真分析了系统质量比、刚度比等参数对系统输出特性(振动位移、速度、相图和输出电压等)的影响。最后,通过与双稳态压电振动能量采集器输出性能的实验结果对比分析,表明非线性宽频压电振动能量采集器在较小的激励幅值作用下具有更高的输出特性和更宽的工作频带。     

开关电源印刷电路板电磁兼容问题的研究

印刷线路间的串扰问题是影响开关电源传导干扰水平的主要因素之一,而旨在降低串扰水平的布线设计却一直是设计中难点。本文提出了一种基于电场分析的开关电源印刷电路板EMC辅助设计的思想方法,其基本思想是以干扰强度分布图为参考选择布线区域,以耦合系数的实时计算结果为指导及时调整布线设计,帮助工程师在印刷线路板的设计阶段就把潜在的干扰抑制在尽可能低的水平上。计算和实验的结果证实了这种思想的可行性。     

System Performance Enhancement in CDMA Mobile System with Uplink Adaptive Power Control Based on Fuzzy Logic

In this paper, an uplink adaptive SIR (signal-to-interference)-based powercontrol mechanism fora CDMA mobile system using fuzzy logic techniques is developed and analyzed.The proposed algorithm providesbetter system performance in terms of outage probability, response time, andstability than current power controlalgorithms and has the advantage of easy implementation.     

基于光学聚焦方法的热驱动微执行器位移测量

随着微机电系统（MEMS）设计日趋成熟,度量问题越来越成为微系统技术中的热点。使用改进的拉普拉斯求和方法（SML）和深度估计法来测量热度驱动微夹持器末端的弯曲程度。实验中,使用了10幅在42℃时微夹持器的水下工作图像来验证这种光学聚焦方法,结果证明使用光学聚焦方法可以测量出作为驱动器反馈输入的末端弯曲大小,实现对驱动器运动的精确控制。     

Influence of the silicon and oxygen content on the properties of non-hydrogenated amorphous carbon coatings

This work reports the development of non-hydrogenated magnetron-sputtered silicon and silicon-oxygen containing amorphous carbon coatings with increasing silicon and oxygen contents respectively. The Si content of a-C:Si coatings increases linearly with the increase of the power applied to the Si target up to 24 at.%, while to the system a-C:Si:O the O content increases with the increase of the oxygen flow to a maximum of 27 at.%. The hardness of the a-C:Si coatings shows two distinct trends with the increase of the Si content, a decrease of hardness for Si contents lower than 10 at.% and an increment above this value are observed. The coatings of the system a-C:Si:O present a decrease of hardness and Young modulus with the increase of the O content. The tribological performance of the coatings is significantly improved by doping the amorphous carbon coatings with silicon and oxygen with a reduction of the friction from 0.17 for the undoped carbon coating to 0.034 for the coating of the system a-C:Si:O with the highest O content.     

Nanotribology of silver and silicon doped carbon coatings

Amorphous hydrogenated carbon coatings a-C:H become very popular materials mainly because of their excellent properties such as low coefficient of friction, high hardness, good anti-wear and corrosion properties. More and more often are carried works aimed at improvement of biocompatibility and adhesion of bacterial cells by doping diamond-like carbon (DLC) coating with third element. Among them recently a great majority is devoted to carbon coatings doped with silver or silicon. The presence of silver in the coating ensures protection of the implant against the disadvantageous influence of bacteria and fungi causing biofilm associated infections, local inflammation and other implant-tissue reactions. Incorporation of silicon promotes osteointegration and leads to the enhancement of mechanical and tribological properties of the coating, which is beneficial for biomedical applications.Silver and silicon incorporated DLC coatings were prepared by a hybrid Radio Frequency Plasma Assisted Chemical Vapor Deposition/Magnetron Sputtering deposition technique on AISI316L substrates. Obtained coatings were characterized in terms of morphology, surface topography and mechanical properties. Tribological properties of the coatings were measured by lateral force microscopy and reciprocating sliding test using nanoindenter.     

Effects of nano-TiO2 on strength,shrinkage and microstructure of alkali activated slag pastes

For alkali-activated slag (AAS), high drying shrinkage is an obstacle which impedes its application as a construction material. In this investigation, nano-TiO₂ was added to AAS, and its mechanical properties and shrinkage were tested to examine its effect on hardened alkali-activated slag paste (AASP). To understand the impact of nano-TiO₂ on AASP at micro scale, FTIR, MIP and SEM were carried out. Experimental results indicate that the addition of nano-TiO₂ to AAS enhances the mechanical strength, and decreases the shrinkage of AASP. FTIR and SEM results demonstrated that the addition of nano-TiO₂ into the AASP accelerates its hydration process, resulting in more hydration products and denser structure. MIP results showed that the addition of nano-TiO₂ reduces the total porosity of AASP and changes the pore structure. The porosity of 1.25–25 nm mesopores, which is believed to be responsible for the high shrinkage of AASP, is remarkably reduced due to the addition of nano-TiO₂.     

潮州寺庙庭园空间分析

以潮州开元镇国禅寺为例,介绍了该寺庙庭园的造园理念与庭园设置,总结了潮州寺庙庭园的造园技法、空间布局以及建筑艺术,并对潮州寺庙庭园的发展与兴衰进程进行了研究,有利于现代园林住宅的规划设计。     

热处理对PMMA@PCM纳米胶囊相变特性的影响及机理

采用界面聚合法制备了以石蜡为芯材、聚甲基丙烯酸甲酯为壳层的纳米胶囊相变材料。胶囊的直径为100~400nm,相变焓可达29J/g,封装比率约为35%。采用差示热扫描量热仪(DSC)对PMMA@PCM经40℃、60℃及100℃热处理后相变特性的变化进行了探讨。结果显示,随着热处理时间的延长,相变温度均有所升高。凝固温度的升高是由于胶囊表面形成了一定量的相变晶种,而熔化温度的升高则是由于纳米胶囊体积的增加而引起的热传导率降低。这一研究结果将有助于分析纳米胶囊相变过程的微结构变化理论。     

纤维素织物形态记忆整理中的液氨处理研究

采用间歇式液氨处理纤维素纤维织物后，再用聚氨酯进行形态记忆整理，探讨了织物结构性能的变化规律。研究结果表明，整理产品的综合效果高于或超过传统整理方式，具有形态记忆恢复功能和较高的强力保留率，而且改善了织物的手感和外观，游离甲醛含量低于50mg／kg。