MP3播放器硬件电路的电磁兼容设计与应用

以MP3播放器硬件电路的电磁兼容(Electromagnetic Compatibicity——简称EMC)设计为例,结合EMC的角度进行设计和电磁干扰分析预测,重点研究了PCB上元件和布局、走线、PCB中的电磁干扰因素以及对PCB的抗干扰措施和软件的EMC设计等,提出了符合电磁兼容设计要求的MP3电路板,最终目的是通过EMC测试,在抗干扰和辐射方面达到国家相关产品标准。     

印刷电路板布线技术对电磁兼容性的影响

电磁干扰是现代电路工业面对的一个主要问题。为了克服干扰,电路设计者不得不移走干扰源,或设法保护电路不受干扰。其目的都是为了使电路按照预期的目标来工作——即达到电磁兼容性。该文主要讨论一般性的PCB布线规则以增强板子的电磁兼容性。     

PCB排版对提高单片机应用系统可靠性的研究

可靠性设计是单片机应用系统设计的重要内容，它保证在规定使用条件下，系统具有良好的运行可靠性与安全性．印刷电路板PCB是单片机应用系统的核心部分．在建立单片机应用系统可靠性设计模型的基础上。提出了PCB可靠性设计应包括总体设计、布线设计和PCB尺寸及器件布置，并介绍了提高PCB可靠度的方法．     

GC-MS analysis of the PCB substitute Ugilec 141 and its occurrence in waste mineral oils

After the restrictions on production and use of PCBs, Ugilec 141, a technical mixture of dichlorobenzyldichlorotoluenes (DBDTs), has been used as a PCB substitute in hydraulic systems. In the Netherlands, the production, import and use of Ugilec 141 has been forbidden since 1988. A method has been developed for the analysis of Ugilec 141 in waste mineral oils to control waste oil import and processing. The method development was based on modification of procedures for the analysis of PCBs in oil and dioxins in fatty matrices and analysis was performed with gas chromatography with mass spectrometry. For sample clean-up, several combinations of column chromatography with activated carbon, alumina, and silica gel have been tested to obtain extracts free from matrix interferences. An internal standard of ¹³C-labeled DBDT was examined to check recoveries from the clean-up procedures. Quantification was performed by comparison with the six most abundant peaks of an external Ugilec 141 standard mixture. Validation experiments showed a linear range from 0.25 to 60 mg Ugilec 141 kg^?1 oil, a reproducibility of 3% and a limit of determination of 0.25 mg Ugilec 141 kg^?1 waste oil. The method was applied in a survey of 70 samples of waste mineral oils from producers all over the Netherlands; this revealed levels below the limit of determination and one positive sample with a concentration of 5.7±0.1 mg Ugilec 141 kg^?1 oil. In an inspection inquiry, one contaminated oil was found containing 116 ± 9 g Ugilec 141 kg^?1 oil.     

Applications of polydimethylsiloxane in analytical chemistry: A review

Silicones have innumerable applications in many areas of life. Polydimethylsiloxane (PDMS), which belongs to the class of silicones, has been extensively used in the field of analytical chemistry owing to its favourable physicochemical properties. The use of PDMS in analytical chemistry gained importance with its application as a stationary phase in gas chromatographic separations. Since then it has been used in many sample preparation techniques such as solid phase microextraction (SPME), stir bar sorptive extraction (SBSE), thin-film extraction, permeation passive sampling, etc. Further, it is gaining importance in the manufacturing of lab-on-a-chip devices, which have revolutionized bio-analysis. Applications of devices containing PDMS and used in the field of analytical chemistry are reviewed in this paper.     

Degradation of PCB by Bacteria Isolated from Long-Time Contaminated Soil

Abstract

Four bacterial isolates belonging to the genera Pseudomonas and Alcaligenes were obtained by the enrichment method, using biphenyl as the sole carbon source, from the soil, which underwent long-time contamination with technical mixtures of PCB. Kinetics of PCB degradation by individual isolates was measured using n-hexane extraction of the cultivation media in proper time intervals and analysed by congener specific gas chromatography with electron capture detection. All isolates exhibit interesting biodegradative potential. Specific degradation of individual congeners with respect to the number and position of chlorine substituents is discussed. The influence of glucose, biphenyl and 3-chlorobenzoic acid on the PCB degradation has been assessed.     

Bioassay (CALUX) measurements of 2,3,7,8-TCDD and PCB 126: Interference effects

Interference effects in CALUX measurements were studied. 2,3,7,8-TCDD and PCB 126 solutions were added, according to an experimental design, to the genetically modified cells. CALUX responses were measured for pure solutions of each of these pollutants, for their mixtures and for successive additions where the first added pollutant is removed after 4 h and replaced by medium solution, the same pollutant or the other one. It appeared that in cases where the cells were exposed to TCDD and PCB 126 in series, additivity was obeyed. This was not the case when the pollutants were added to the cells simultaneously as these results show antagonistic effects.     

汽车音响导航系统中DDR高速信号的PCB设计方法

伴随半导体工业的飞速发展,越来越多的高速度、高功能、高精密的封装器件被应用到现代汽车音响的系统设计中,特别是频率达到200MHz以上的高速DDR在电子导航系统中的运用,更要求PCB设计者在实现设计目标、SI和电磁干扰（EMI）设计规则上,做到严格的时序匹配以满足波形的信号完整性。本文以DDR200为例,介绍高速DDR在车载音响电子导航系统中的PCB设计方法。     

PCB检测中的自动光学检测系统的设计

本文介绍了用自动光学系统检测PCB板的设计方法.主要包括AOI系统的功能,自动光学检测系统的组成及工作原理,通过自动检测来确定PCB板的质量,从而避免传统人工方式的繁琐,具有智能化的特点.     

多线程技术在基于HALCON的AOI中的应用

电子封装不断朝微型化方向发展,传统的印刷电路板(PCB)焊点检测方法已越来越难以满足生产的要求.基于机器视觉的自动光学检测(AOI)系统可对PCB焊点进行统一、可靠的快速检查,其检测速度是一个非常关键的问题.比较了单线程和多线程技术在AOI中程序运行的时间,实验表明,多线程技术的运用能使印刷电路板(PCB)的检测速度得...