基于MCS-51单片机的家庭安防电话委托系统的设计

本文介绍了一种以MCS-51单片机为微控制器的家庭安防电话委托系统，给出了系统的原理图，单机与语音芯片的硬件连接图以及系统部分软件流程图。     

Resonance properties and mass sensitivity of monolithic microcantilever sensors actuated by piezoelectric PZT thick film

The PZT thick film cantilever devices fabricated via MEMS process have much attraction because they are appropriate for biological transducer or sensor, resulting from their large actuating force and relatively high sensitivity especially in liquid. By means of resonance behavior, theoretical calculation and experimental verification of the PZT thick film cantilever devices have not been studied before. Accordingly, we focused on the sensitivity analysis and interpretation of the PZT thick film cantilevers in this study. Especially, the investigation for mass sensitivity of the PZT thick film cantilever is of importance for physical, chemical and biological sensing application. The PZT thick film cantilever devices were constructed on Pt/TiO₂/SiN _X /Si substrates using screen printing method and MEMS process. The harmonic oscillation response (resonance frequency) was measured using an optical laser interferometric vibrometer. The effect of cantilever geometry on the resonance frequency change was investigated. Compared with the theoretical resonant frequency change by mass loading, the experimental resonant frequency change of the PZT micromechanical thick film cantilever shows a variation of less than 2%. Mass sensitivities are estimated to be 30.7, 57.1 and 152.0 pg/Hz for the 400 × 380 μm, 400 × 480 μm and 400 × 580 μm cantilever, respectively.     

Characteristic of grain oriented (Bi0.5Na0.5)TiO3-BaTiO3 ceramics

Dielectric and piezoelectric properties of grain oriented (Bi_0.5Na_0.5)TiO₃-BaTiO₃ ceramics were investigated in a process that the templated grain growth and hot pressing methods were employed. A ceramic composition in Bi-based perovskite structure family, (Bi_0.5Na_0.5)TiO₃-BaTiO₃, was chosen as a matrix material and plate shaped SrTiO₃ as a template. To examine the combined process effect on piezoelectric properties, three processes, conventional solid reaction, templated grain growth and the combine treatment of templated grain growth and hot-pressing, were compared. Specimen processed by templated grain growth and hot pressing methods exhibited better piezoelectric coefficient, d ₃₁ (−79.6 pC/N) and electromechanical coefficient, k ₃₃ (0.35) than those of the other specimens, fabricated by solid reaction and templated grain growth, respectively. The improved properties were attributed to reduction of pore existing in matrix, which is related to abnormal grain growth from SrTiO₃ template and its resultant heterogeneous shrinkage.     

Impedance spectroscopy study and electrical behavior of PMN-PZT actuators joined by ceramic slurry

The solid solution of Pb(Mg,Nb)O₃-Pb(Zr,TiO) O₃ materials have high piezoelectric constant of 600 ∼650 pC/N and electromechanical coupling coefficient k _p of 0.65. Due to such high piezoelectric constant and electromechanical coupling coefficient, Pb(Mg,Nb)O₃-Pb(Zr,TiO)O₃ materials have been attracted attentions for the applications of multilayer ceramic actuators. Actuators can be produced by staking piezoelectric ceramic materials and inner electrodes, alternatively. However, it is difficult to fabricate huge ceramic actuators without any serious problems during the process conditions. Because ceramic are easily cracked during the sintering process, due to strikingly different shrinkage rate between the ceramic materials and metal electrodes. In this research, new jointing methods will be proposed for huge ceramic actuators, and then their electrical properties were investigated. Time dependent leakage current and impedance spectroscopy were employed to expect device performances.     

A simple method to fabricate high-performance carbon nanotube field emitters

A simple new method to fabricate carbon nanotube field emitters was developed. Single wall carbon nanotubes with high graphitization were attached on Sn or Ni layered glass substrate in-situ in arc-discharge chamber. Post heat treatments below the deformation temperature of soda-lime glass guaranteed a good mechanical adhesion and electrical contact of the nanotubes. The morphology of the metal electrode layers was examined with the heat treatment temperatures to optimize the heat treatments. The emitters formed on Sn layers showed lower turn-on voltage and higher current density than those formed on Ni layers. A good field emission performance was realized in an emitter where nanotubes were deposited on Sn layer of the thickness 100 nm and annealed at 300^∘C. The current density was 2.5 mA/cm² at 3.5 V/μm. The emitter structure was maintained stable for 8 h.     

脱氮除磷污泥（混合液）回流方法

简要分析了脱氮除磷工艺三种污泥(混合液)回流方法(泵提升法,叶轮搅拌提升法和空气提升法)各自的特点,并认为由于叶轮搅拌提升法和空气提升法便于实现构筑物一体化,可以简化工艺流程,节省基建投资,而且能耗低,操作简单,在拟建的中小规模污水处理厂中具有良好的应用前景。     

提高IOCP多媒体网络服务器性能的方法及其实现

面临IOCP多媒体网络服务器所的大复杂度环境设计问题，本文论述该网络服务器的网络底层开发、结构设计及逻辑模块设计，提出提高其性能的方法：优化数据封装以及投递方式，增加数据的处理效率；整体结构模块化设计．提高代码的可重用性以及可扩展性;通过端口分流的方式．实现对逻辑模块性能改进。方法的实用性已通过实验室测试证实。     

A separation theorem for single-source network coding

In this paper, we consider a point-to-point communication network of discrete memoryless channels. In the network, there are a source node and possibly more than one sink node. Information is generated at the source node and is multicast to each sink node. We allow a node to encode its received information before loading it onto an outgoing channel, where the channels are independent of each other. We also allow the nodes to pass along messages asynchronously. In this paper, we characterize the admissibility of single-source multi-sink communication networks. Our result can be regarded as a network generalization of Shannon's result that feedback does not increase the capacity of a discrete memoryless channels (DMCs), and it implies a separation theorem for network coding and channel coding in such a communication network.