Synthesis and characterization of EuBa2Ca2Cu3O9−x: The influence of temperature on dielectric properties and charge transport mechanism

High dielectric constant materials have a crucial importance for various microelectronic applications such as memory devices, supercapacitors etc. Among other insulators, perovskite structured oxide materials attract great interest not only for their high dielectric constants but also their unique electrical and magnetic properties such as superconductivity etc. From this point of view, a new Europium based copper oxide layered material with perovskite structure (EuBa₂Ca₂Cu₃O_9−x coded as Eu-1223) has been synthesized by solid state reaction method in this work. The physical and chemical properties of Eu-1223 have been determined by FTIR, SEM, XRF, XRD, TGA and DTA techniques. The influence of temperature on impedance and dielectric properties of Eu-1223 has been investigated by impedance spectroscopy measurements performed within the frequency interval of 5 Hz–13 MHz between 298 K and 408 K temperatures. It has been found that the Eu-1223 material has high dielectric constants at each temperature operated. In addition, Eu-1223 sample behaves as a colossal dielectric material up to 300 kHz for 408 K due to observation of dielectric constant values which are greater than 10³. Furthermore, it has been revealed that Eu-1223 material can be used as thermally sensitive resistors in electronic circuits due to its decreasing resistance with increasing temperature. Moreover, it has been observed that the relaxation frequency of the system shifts from 46.5 kHz (low frequency radio wave band) to 1.57 MHz (mid frequency radio wave band) as the temperature increasing from 298 K to 408 K. According to dc conductivity investigations, the variation of dc conductivity with the inverse of temperature satisfies linear relationship that indicates a thermally activated nearest neighbor hopping conduction. On the other hand, it has been determined that ac conductivity has frequency dependent relation which obeys ω^s for the high frequency region. Furthermore, the frequency exponent, s, which takes values between 0.7 and 0.4, shows a decreasing behavior with increasing temperature. In conclusion, ac charge transport mechanism has been predicted as correlated barrier hoping for Eu-1223.     

基于PROTEUS的数控恒流源设计与仿真

为了克服传统单片机开发过程中存在的硬件成本高、开发速度慢等诸多弊端,介绍了采用EDA仿真软件PROTEUS开发的数控恒流源系统。给出了系统硬件电路设计方案和在Keil环境下开发的主要程序代码。AT89C52单片机控制TLC5615串行D/A转换器输出锯齿形电压信号,此电压信号经电压电流转换电路转换产生稳定的线性电流信号。在PROTEUS环境中完成了软件和硬件的仿真,验证了设计方案的可行性。设计过程简单方便,降低了开发成本,设计效率得到大大提高。     

片上网络存储器的BIST电路设计

片上网络（Network-on-Chip ,NoC）作为解决片上系统存在的问题而提出的一种解决方案,正受到越来越多的关注,测试技术是NoC设计工作的重要组成部分。该设计针对NoC系统中SRAM存储器模块,研究了SRAM的故障模型,建立了片上网络通信架构的功能模型,复用片上网络作为测试存取路径,设计完成了基于M arch C＋算法的BIST电路设计。该方案采用Verilog语言完成设计,并且在基于FPGA的NoC系统平台上实现了对SRAM的测试。实验结果表明,在面积开销增加较小的情况下,该方法具有较高的故障覆盖率。     

应用Smartio C104H多串口卡实现多路信号采集及处理

本文论述了利用Smartio C104H多串口卡的串口通信技术,实现了多路岩石热解信号的采集分析处理。文中还对Smartio C104H多串口卡在YKR-Ⅰ岩石快速热解仪的应用进行了研究,并介绍了基于visualc++实现的上位机通信设计原理。     

碳二加氢催化剂选择性的快速评价法及其应用

介绍了碳二加氢反应的原理，从反应物转化量与反应热生成量的关系入手，找出催化剂选择性与床层温差和进料乙炔含量的定量关系，建立了一种碳二加氢催化剂选择性的快速评价方法，并用此法对三种催化剂的选择性进行了评价，评价结果与实际情况吻合。     

有线电视网络资源管理系统

对有线电视网络资源管理系统的主要功能进行阐述 ,该系统采用C S和B S相结合的体系结构 ,有利于网络资源的整合与共享 ;采用GIS技术 ,对网络资源数据进行地图化管理 ,文中还对选用的地理平台进行介绍     

基于Q2358C模块的短信收发系统设计

为了克服用手机发送短信时键盘空间的限制,设计了基于Q2358C无线收发模块的短信收发系统。该系统由硬件系统和软件系统两部分组成。硬件系统主要由Q2358C收发模块及其外围电路组成收发终端,并通过RS232串口与PC机连接;软件部分主要由设计的系统应用程序通过动态链接库向模块发送AT(Attention)指令,从而使系统完成短信收发功能。系统具有结构简单、操作方便、性能稳定等特点。     

高速电视图像和实时信息融合与回放的工程实现

基于高速电视图像文件与跟踪转台实时运动数据信息的存储结构,在VC 6.0环境下编程开发一种测量软件,解决了在实际工程应用中实现图像信息与跟踪转台实时信息的融合与回放时所遇到的对4G大文件的读写操作问题以及图像与实时数据融合时的时间同步问题,提出了一种将高速电视图像及实时信息的融合与回放的通用方法,在工程应用中取得了良好的效果.     

C50引导功能的使用

Ｃ５０内部具有９Ｋ单指令周期访问的片内ＲＡＭ，在应用程序不太大的情况下，将程序在运行前由存取速度较慢的片外的ＥＰＲＯＭ读入片内ＲＡＭ，再在零等待状态下运行不失为一种方便快速的方法。本文就此进行了说明。     

Can Markov regime-switching models improve power-price forecasts? Evidence from German daily power prices

Non-linear autoregressive Markov regime-switching models are intuitive. Time-series approaches for the modelling of electricity spot prices are frequently proposed. In this paper, such models are compared with an ordinary linear autoregressive model with regard to their forecast performances. The study is carried out using German daily spot-prices from the European Energy Exchange in Leipzig. Four non-linear models are used for the forecast study. The results of the study suggest that Markov regime-switching models provide better forecasts than linear models.