Piezoelectric sensor based on electrospun PVDF-MWCNT-Cloisite 30B hybrid nanocomposites

Piezoelectric materials have attracted substantial interest in applications such as sensors and actuators. Ferroelectric and piezoelectric polymeric fibers doped with nanoparticles are made for use in nanoscale electronic devices. In this paper, we report on poly (vinylidene fluoride) (PVDF) nanocomposites doped with different ratios of multi-walled carbon nanotube (MWCNT) and Cloisite 30B (OMMT) nanoclay prepared by electrospinning technique. The effect of different ratios of OMMT and MWCNT nanofillers and potential synergistic effect of these fillers on the crystalline structure of PVDF and the performance of resulting piezo-device were studied. Results showed that OMMT increases beta phase crystals and piezoelectric properties of PVDF as compared with MWCNT. Meanwhile, MWCNT decreases impedance and increases dielectric constant of PVDF as compared with OMMT. The acoustic absorption behavior of PVDF/MWCNT/OMMT hybrid nanocomposite was also investigated. It was found that the sound absorption efficiency of PVDF/MWCNT/OMMT hybrid nanocomposites was increased compared with that of pure PVDF fibers and film. No synergistic effect of OMMT and MWCNT on the properties of PVDF was observed.     

110kV某变电站电容式电压互感器的故障分析

通过对110kV某变电站的故障电容式电压互感器进行现场检查、电气试验等,逐步对其进行分析,找出发生缺陷的根本原因。     

On the hybrid multi-watermarking

Multi-watermarking is the technique to embed multiple messages into the same media content repeatedly. It can be used to identify media content's ownership or trace the illegal redistributors in media distribution. However, some performances of multiple watermark embedding, e.g., the distortion and security, are not considered carefully in the previous work. In this paper, the application scenario and framework of hybrid multi-watermarking are figured out, which show the secure media distribution model suitable for hierarchical media distribution. Additionally, the multi-watermarking based on hybrid multiplicative rule is firstly proposed and then analyzed theoretically with respect to two cases, i.e., the multi-embedding of same watermark sequence and the multi-embedding of different watermark sequences. The analysis emphasizes on four aspects, i.e., robustness, capacity, distortion and security, each of which considers two cases, i.e., the authorized embedding and unauthorized embedding. What is more, the locally optimum detector for multi-watermarking of hybrid multiplicative rule is reduced, and some potential attacks are investigated. Additionally, for each case, some suggestions are proposed to improve the system's performance. Finally, some comparative experiments are done, and results are given to show the validity of the theoretical analysis.     

混合云对陕西旅游电子商务的支持研究

私有云运营效率低且公共云安全风险高,为实现混合云架构对电子商务系统经济性和安全性的支持,通过对相关技术和各云服务商解决方案的研究分析,面向陕西旅游业的需求,选择AWS的公共云服务和基于OpenStack构建的私有云,并提出混合云架构。可帮助陕西低成本地搭建旅游电子商务平台,推动旅游信息化,提高陕西旅游服务质量和竞争力。     

CL81型高压聚酯膜电容器的阻燃试验

介绍了ＣＬ８１型高压聚酯膜电容器行业标准中关于阻燃试验的技术要求和试验方法。     

钽粉氧含量对其钽阳极漏电流的影响

在多年实践经验基础上，用氧含量Ｘ１（质量分数）０．２０％～０．３８％的四种钽粉，控制钽阳极中残余氧含量Ｘ２（质量分数）在０．０８％～０．２０％间，采用正交设计实验研究了对其漏电流的影响，并建立了漏电流峰值ＩＬ和Ｘ１、Ｘ２间的预示方程，描述了漏电流和钽粉氧含量（Ｘ１）、残余氧含量（Ｘ２）间的关系。随后，用预示方程讨论了钽中氧和钽阳极中残余氧对其漏电流的影响。     

专用视频放大器模块的设计原理

专用视频放大器模块集高增益、大动态、低噪声于一体，而且处理的信号比较复杂，在设计上具有相当难度。选择合适的器件是基础，而使器件工作在最佳状态，设计一个良好的信号通道则是关键；同时，一个品质优良的放大器必须要有关键的参数来表征，因此参数的选择、定义以及相关的测试技术极为重要。本文介绍的视频放大器模块总增益高达９０ｄＢ，带宽１０ＭＣ，系统ＡＧＣ控制范围７０ｄＢ，输出幅度１￣８Ｖｐ－ｐ，噪声电压３０μＶ     

铁电电容的电极结构

作为铁电电容的电极材料 ,铂是使用最为广泛的金属。在 PZT薄膜的上下两层分别用离子束溅射淀积厚度为 50 nm和 10 0 nm的 Pt。在铂层上按常规工艺需蒸发 1～ 2 μm的 Al作为布线金属。为避免在热处理过程中的固相反应 ,Al/ Pt之间还需嵌入阻挡金属。观察了 Si,Co,Ni,Ti和 Ti/ W合金膜的阻挡特性。实验证明一定组分的 Ti/ W合金膜能有效地抑制 Al/ Pt固相反应 ,获得较为理想的接触特性。     

微机械可变电容制作工艺中的牺牲层释放和残余应力分析

运用高选择比的特别配方来释放MEMS可变电容制作工艺中的牺牲层,以保护上级板金属铝层,同时很好地释放牺牲层磷硅玻璃。探讨了上级板的粘附问题,对工艺中影响成品率的关键因素残余应力进行了模拟,当温度T为350℃时,平面应力P为811.6 MPa;当温度T为500℃时,平面应力P为1 185.9 MPa。分析了残余应力对上级板的影响和对悬臂梁的等效弹性系数的影响。     

Integrated power and handoff control for next generation wireless networks

In this paper, joint downlink power control and handoff design is formulated as optimization problems that are amenable to dynamic programming (DP). Based on the DP solutions which are impractical, two new algorithms suitable for next generation wireless networks are proposed. The first one is an integrated hard handoff/power control scheme that endeavors a tradeoff between three performance criteria: transmitted power, number of handoffs, and call quality. The second is a soft handoff/power control algorithm that also takes into account the additional cost of utilizing soft handoff. The proposed algorithms present a paradigm shift in integrated handoff/power control by capturing the tradeoff between user satisfaction and network overhead, therefore enjoy the advantages of joint resource allocation, and provide significant improvement over existing methods. The achievable gains and the tradeoffs in both algorithms are verified through simulations.