高速电路PCB设计中串扰问题的抑制

在电子产品设计的高速化和小型化时代,如何抑制传输信号的串扰,使其降低到最低,这是每一位高速电路PCB设计者,所要追求的目标。本文通过对影响传输信号串扰因素的分析,结合多年高速电路PCB设计的经验,对抑制信号串扰的方法做了比较详尽的表述。为高速电路PCB设计人员提供一些经验,使得在高速电路PCB设计中少走弯路。     

基于单片机的PCB雕刻机系统设计

设计了一套利用单片机实现的PCB雕刻机系统.重点设计了雕刻机的机械结构和整个系统的方案.编写了将PCB制图软件输出格式文件转换为单片机程序和能够与单片机进行数据交互的转换程序软件.选择合适的步进电机并设计了驱动电路.     

555定时器典型应用电路及其PCB设计

针对PCB教学中因忽略电路原理分析而使学生盲目进行PCB学习的问题,提出了相应的解决方法。即总结归纳了555定时器三个典型应用电路,并对其工作原理进行了分析,最后给出这些典型电路相应的PCB设计。文本所提及的教学设计能够使学生较快地掌握PCB设计方法,并对PCB学习产生浓厚的学习兴趣,可供教师作为教学参考,同时也为课程整合提供了一些思路。     

浅谈中职电子专业学生掌握PCB原理图反推的方法

PCB原理图反推是指根据现有PCB文件或者PCB板实物反向推导出原理图,它在电路分析,产品调试、维修、改进升级过程中有着不可或缺的作用。特别是在不知道电路图的家电维修中,根据电路板描画电路图,不一定是整块电路,绘画出出故障中心的局部电路进行分析、维修效果大大提高。     

Altium Designer教材编写应突出职教特色

针对目前高职PCB设计课中教材严重脱离电路设计应用实践,本文结合电路设计实际工程案例,新编Altium Designer教材以典型案例驱动,借助由浅入深、由易到难的案例训练,逐步掌握原理图,最后以机器人电路设计为例,讨论了层次原理图和多通道电路的设计方法,提高了学生对高级原理图及PCB图的设计技巧。教学实践表明,采用以设计案例为主的新编教材进行教学,可优化学生的知识结构,强化电路及PCB的设计能力,有利于培养学生的学习能力和创新能力。     

基于Protel 2004的PCB设计

Protel是Altium公司推出的电路辅助设计系统。设计者绘制原理图后,紧接着是设计印制电路板,简称PCB。PCB设计一般按照规划电路板、装载元器件封装库及网络表、元器件的布局、布线等步骤进行。本文通过对整个PCB设计过程的探讨,为正确高效地设计印制电路板提供了有效的途径。     

PLC在热转印机控制系统中的应用

对热转印机的工作原理和控制工艺进行探讨,通过使用触摸屏人机界面与可编程控制器的连接,设计出了精美的控制界面,从而简化了控制线路,便于理解与操作,有效提高设备控制性能。     

学排序

收集破旧儿童图书画册,标记图,彩色纸边角料,粘贴材料,16开大的白卡纸,过塑机,彩色笔等。     

PCB中防止共阻抗干扰的地线设计

电子电路中,共阻抗干扰对电路的正常工作带来很大影响.在PCB电路设计中,尤其在高频电路的PCB设计中,必须防止地线的共阻抗所带来的影响.通过对共阻抗干扰形式的分析,详细介绍一点接地在电子电路中,特别是在高频电路中对共阻抗干扰的抑制作用,以及采用一点接地防止共阻抗应注意的问题.同时对PCB板内地线布局的主要形式和要求进行了简要阐述.     

用Protel DXP 2004制作PCB板的基本原则

熟练掌握用Protel DXP 2004这个软件制作PCB板的技巧就能更好地设计PCB电路板,也使设计的电路板更专业化,电路工作更为稳定。     

Burning a Candle in a Vessel, a Simple Experiment with a Long History

The experiment in which a candle is burned inside an inverted vessel partially immersed in water has a history of more than 2,200 years, but even nowadays it is common that students and teachers relate the change in volume of the enclosed air to its oxygen content. Contrary to what many people think, Lavoisier concluded that any change in volume in this experiment is negligible; moreover, the explanation relating oxygen consumption in the air with its change in volume is known to be wrong. In this work we briefly review the history behind the candle experiment and its relationship with some typical erroneous explanations. One of the key factors behind Lavoisier’s success was the use of experiments carefully designed to test different hypotheses. Following these steps, we performed several closed volume experiments where the candle wick was replaced by a capillary stainless steel cylinder supported and heated by a nichrome filament connected to an external power supply. Our recorded experiments are displayed as web pages, designed with the purpose that the reader can easily visualize and analyze modern versions of Lavoisier’s experiments. These experiments clearly show an initial phase of complete combustion, followed by a phase of incomplete combustion with elemental carbon or soot rising to the top of the vessel, and a final phase where the hot artificial wick only evaporates a white steam of wax that cannot ignite because no oxygen is left in the closed atmosphere. After either a complete or incomplete combustion of the oxygen, our experiments show that the final gas volume is nearly equal to the initial air volume.     

天保房地产开发公司发展战略研究

天保房地产开发公司根植于天津滨海新区。依托控股公司带来的资源优势，基于滨海新区列入国家发展战略部署的背景，在近年来取得了迅速的发展。但是随着国家一系列政策的出台，中国的房地产行业面临着一次大的重新洗牌过程，同时企业内部仍然存在着制度缺陷、管理不规范、流程不清晰、人员激励不足等各方面的问题，所以，天保房地产公司在面临着滨海新区良好发展机遇的同时，也面临着很大的挑战。如何在机遇与挑战并存的环境中，认真分析和评估企业的外部环境及内部资源与能力的优劣势，对企业内部的资源与能力进行积累与培养，制定相应的竞争与发展战略，引导企业的健康长远发展具有一定的必要性与迫切性。 本文从竞争战略的角度，综合分析天保房地产开发公司所面临的外部环境和内部条件，研究探讨天保房地产开发公司的发展战略框架，包括战略的指导思想、战略定位、战略目标及相应的实施措施，以期实现天保房地产开发公司的发展愿景和核心价值。     

指鹿为马

秦二世时,丞相赵高野心勃勃,日夜盘算着要篡夺皇位。可朝中大臣有多少人能听他摆布,有多少人反对他,他心中没底。于是,他想了一个办法,准备试一试自己的威信,同时也可以摸清敢于反对他的人。     

Short a and Long a

Easy Phonics带你学习自然拼读,让你学会字母的发音规律,正确地拼读单词。本期让我们继续来看看、读读、写写重读音节中包含字母a的单词,区分它们读短音short a-/e/,还是长音long a-/ei/。     

Short a and Long a

Easy Phonics栏目带你轻松地学习自然拼读!在读读、听听、拼拼和玩游戏中,你将了解字母的发音规律,并正确地拼读单词。这一期,我们来学习元音字母a的短音(short a)和长音(long a).     

做校长·做学问·做人

从前,有一句话,叫做"吃得苦中苦,方为人上人".这句话被认为动机不纯,怎么可以做"人上人"呢?其实,对于"人上人"可以作不同的理解,一种理解是"骑在人民头上,作威作福",这种"人上人"当然不好;但也可以解释为比别人做更多的贡献,吃更多的苦,经过更多的挫折与困难而比一般人更成熟、更坚强,更知道怎么做人.实际上,对这句话应是作后一种理解的,因为这种"人上人"是与"苦中苦"联系在一起的.     

毕飞宇:一镜、一钟、一影、一胡琴而已

本文从毕飞宇小说中一再出现的镜、钟、影和胡琴的意向入手,考察毕飞宇小说的叙述人称、叙述速度、叙述结构和叙述意图。深入阐释＂我＂与＂他＂的分离与揉合,＂快＂与＂慢＂的交替与演变,＂是＂与＂非＂的分明与模糊,＂语言＂与＂沉默＂的相反而相成。     

Paving a clear path in a thick forest: a conceptual analysis of a metacognitive component

The concept of metacognition refers to one’s knowledge and control of one’s own cognitive system. However, despite being widely used, this concept is confusing because of several reasons. First, sometimes it is not at all clear what is cognitive and what is metacognitive. Second, researchers often use the same term, namely, “metacognition” even when they refer to very different aspects of this complex concept. Alternatively, researchers may use different terms to indicate the same metacognitive elements. Another foggy matter is the interrelationships among the various components of metacognition discussed in the literature. This conceptual confusion regarding the concept of metacognition and its sub-components calls for in-depth theoretical and conceptual clarifications. The goal of this article is to portray a detailed example of a conceptual analysis of meta-strategic knowledge (MSK) which is one specific component of metacognition. This specific example is used to draw a general model for conceptual analyses of additional metacognitive components. The approach suggested here is to begin with a clear definition of the target sub component of metacognition, followed by a systematic examination of this sub component according to several dimensions that are relevant to metacognition in general and to that sub component in particular. The examination should include an analysis of how the details of the definition of the target sub-component refer to: (a) general theoretical metacognitive issues raised by prominent scholars; (b) definitions formulated and issues raised by other researchers who have investigated the same (or a similar) sub-component and, (c) empirical findings pertaining to that sub-component. Finally, it should be noted that since metacognition is a relational rather than a definite concept it is important to situate the context within which the conceptual analysis takes place.