数字下变频器GC1012B原理及配置方法

数字下变频技术是软件无线电的一项核心技术,其性能的好坏直接影响数字接收机的精度。GC1012B是美国TI公司推出的新型数字下变频器。文中从GC1012B的结构特点和内部功能框图出发,分析其工作原理,并介绍GC1012B几个主要寄存器的配置方法,从而实现对频率、滤波模式、增益大小等参数的设置。最后给出了一个具体配置实例作为参考。     

The effect of segment length on some properties of thermoplastic poly(ester–siloxane)s

A series of novel thermoplastic elastomers, based on poly(dimethylsiloxane) (PDMS) as the soft segment and poly(butylene terephthalate) (PBT) as the hard segment, were synthesized by catalyzed two‐step, melt transesterification reactions of dimethyl terephthalate and methyl esters of carboxypropyl‐terminated poly(dimethylsiloxane)s (M?_n = 550–2170 g mol^?1) with 1,4‐butanediol. The lengths of both the hard and soft segments were varied while the weight ratio of the hard to soft segments in the reaction mixture was maintained constant (57/43). The molecular structure, composition and molecular weights of the poly(ester–siloxane)s were examined by ¹H NMR spectroscopy. The effectiveness of the incorporation of the methyl‐ester‐terminated poly(dimethylsiloxane)s into the copolymer chains was verified by chloroform extraction. The effect of the segment length on the transition temperatures (T_m and T_g) and the thermal and thermo‐oxidative degradation stability, as well as the degree of crystallinity and hardness properties of the synthesized TPESs, were studied. Copyright © 2003 Society of Chemical Industry     

镍层耐硝酸腐蚀性测试——一种简单的预先探测ENIG镍层“黑盘”现象的测试方法

随着更加精细的SMT、BGA等表面贴装技术的运用,化学沉镍金(ENIG)作为线路板最终表面处理得到了越来越广泛的应用,同时可怕的“黑盘”现象也随之更广泛地“流行”起来,直接导致贴装后元器件焊接点不规则接触不良。为了贯彻执行最好的流程控制和采取有效的预防措施,了解这种焊接失败的产生机理是非常重要的,及早的观测到可能发生“黑盘”现象的迹象变得同样关键。本文介绍了一种简单的预先探测ENIG镍层“黑盘”现象的测试方法-镍层耐硝酸腐蚀性测试,这种测试可以用于作为一种常规的测试方法监测一般化学沉镍溶液在有效使用寿命范围内新鲜沉积的镍层的质量。利用Weibull概率统计分析在不同的金属置换周期(MTO)下镍层的可靠性能表现。结合试验结果得出了一个镍层耐硝酸腐蚀性的判定标准。     

网络管理中事件关联检测机制的研究

网络事件的关联检测是网络管理需要解决的一个关键问题,本文根据分布式网络管理的特点,首次明确定义了网络事件的基本关联关系,在此基础上提出了一种基于Petri Net的事件关联检测机制,实现了基于事件内容的细粒度关联检测,并且在事件检测中充分考虑了时间因素,有效地提高了事件关联检测的准确性。     

在二(2-乙基己基)磷酸钠的微乳液中金属萃合物对水增溶的影响

测算了由二（2－乙基己基）磷酸钠，金属盐（CoSO4,NiSO4,ZnSO4,MgCl2或Cr(NO3)3)水溶液，正辛醇和正辛烷组成的微乳液中正辛醇从连续油相到界面的ΔGo→i^o和水的极限增容量φ'H2O。用金属萃取络合物反胶束的形成及其亲油性解释了金属离子对φ'H2O和ΔGo→i^o的影响。     

丙烯腈－苯乙烯共聚物水解磺化产物对泥浆的稳定作用

在实验室条件下对用丙烯腈－苯乙烯共聚物在硫酸存在下的水解磺化产物（ＨＳＡＳ）处理的泥浆性能进行了评定。ＨＳＡＳ处理的泥浆有较小的滤失性，较好的耐盐和抗高温性。     

烧结工艺对液相合成（SrPb）TiO3基陶瓷热敏特性影响的研究

本文在液相合成（ＳｒＰｂ）ＴｉＯ３粉的基础上，研究了升温速率、保温时间、烧结温度及降温方式对（ＳｒＰｂ）ＴｉＯ３基陶瓷的Ｖ型ＰＴＣ热敏特性的影响。实验表明：升温速率对其热敏特性影响不大，保温时间和烧结温度的作用是一致的，具有一最佳范围。而降浊方式对材料的热敏特性影响较大。综合各因素的影响，本配方中，样品的烧结制度定为：以２００℃／ｈ的速率升温，在１２５０℃保温１ｈ，炉冷至９５０℃，保温０．５ｈ，再     

邻—(4—乙基苯甲酰基)苯甲酸的研究

本文阐述了通过Friedel-Crafts反应合成邻-(4-乙基苯甲酰基)苯甲酸的方法.研究了影响产物质量的因素,提出了适宜的工艺条件.     

插补法CAI研究

数字程序控制计算机辅助教学是将计算机技术用于数字程序控制的教学过程，它帮助学生学习并模拟教学实验．本文介绍了数字程序控制中直线插补和圆孤插补的ＣＡＩ实现方法．     

A formal description of open distributed processing (ODP) trading based on guidelines for the definition of managed objects (GDMO)

New requirements of growing computer networks and information systems have an influence on extended client/server models with increased functionality. This forms the basis for service management in distributed systems which is realized by a service trading concept. This paper studies the requirements derived from the Open Distributed Processing (ODP) Reference Model in order to consider an open service market. Furthermore, it examines management possibilities for describing the service trading scenario. Because of similar architectures and properties ODP services, service offers, types, exporters and traders are mapped onto management components and modeled as managed objects. Therefore, the Guidelines for the Definition of Managed Objects (GDMO) are used. The final concept allows a precise and unambiguous study of the service trading scenario and provides means for exporting and importing of service offers in a distributed environment.