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1.
电子技术基础是电气专业的必修课。因为本课程非常抽象,学生难于接受。例如。二极管整流电路的教学目的是：使学生掌握（1）半波整流电路和桥式整流电路的电路形式;（2）整流前后的电压波形;（3）整流前的交流电压的有效值U2与负载电压有效值V0之间的关系（半波整流电路V0=0．45U2）; 相似文献
2.
变压器根据电磁感应的原理制成．中学物理当中所说的变压器往往是指理想变压器,所谓理想变压器是指磁通量全部集中在铁芯中而本身不消耗能量的变压器．理想变压器的基本关系式有：（1）功率关系：P入=P出;（2）电压关系：U1／U2=n1／n2;（3）电流关系：当只有一个副线圈时,I1／I2=n2／n1; 相似文献
3.
投影仪是电化教学中常用的教学设备,当其变压器损坏后,通常是拆下重绕或者换新,经试验,用可控硅调压电路进行代换,其效果令人满意。上图是其电路原理,图中２ＣＴＳ是双向触发二极管,ＫＳ_１是小电流双向可控硅,耐压为６００Ｖ,电流为２Ａ,ＫＳ_２为大电流双向可控硅,耐压也是６００Ｖ,电流为２０Ａ,负载Ｒ_Ｌ为２４Ｖ／２５０Ｗ溴钨灯泡。此电路工作原理大致如下：接通电源,电源电压无论是上正下负,还是上负下正,都通过Ｗ、Ｒ_１、Ｒ_２给Ｃ_２充电,当Ｃ_２上的电压达到双向二极管的正向或反向转折电压时,２ＣＴＳ突然转… 相似文献
4.
一、知识结构二、学习指导（一）电功1．电功实验电动机通电转动并提升重物的实验,一方面表明电流可以做功;另一方面也说明决定电流做功多少的因素有电压、电流和通电时间三个．2．电动概念电流所做的功,叫做电功．电流做功的过程,实际是把电能转化为其他形式的能的过程．电流做功的多少,跟导体两端电压、通过导体的电流和通电时间成正比．3．电功公式和单位（1）基本公式：W=UIt=UQ（Q为电量：Q＝It）（2）变形公式;W=I2Rt=U2t/R=Pt．（3）单位变换：1焦一1伏·安·秒一1伏·库一l安’·欧·秒一1伏’·秒／欧一l瓦·秒．（4）… 相似文献
5.
一、正弦交流电的规律
1．表达式：e=Emsinωt，Em=nBStω。
2．四值：瞬时值、有效值、平均值和最大值。
3．正弦交流电有效值与最大值关系：I=Im/√2
4．一般交流电有效值只能根据电流热效应求。
5．交流电图像表示法，注意考查变形交流电产生过程（大小不变、方向变化的交流电产生）。 相似文献
6.
欧姆定律是电学的重要定律,应用欧姆定律解题,要十分注意定律中物理量的“同一性”和“同时性”．所谓“同一性”,是指定律中的人U、R为同一段电路的电流、电压、电阻;所谓“同时性”,是指定律中的I、U、R为同一时刻的电流、电压、电阻．张冠李戴、彼时此用都是错误的诸丢I‘J下而倒倒1女日图1所示电路中,RZ＝10欧,R3＝20欧,电源电压6伏．求：（l）S;、S都打开时,通过RZ的电流是多少？（2〕S,、3都闭合时,中路中的电流为1．2安,凡的阻值是多大？错解（1）通过几的电流：分析造成上述错解的原因,是对定律中各物理量的“… 相似文献
7.
1．特点
（1）在直流电路中,当电容器两极间电压升高时,电容器充电．反之则对外放电．此时,电路中有充电或放电电流．
（2）电容器对稳恒直流电路起断路作用,与电容器串联的电阻相当于导线,电容器两极间的电压等于与它并联的电阻两端的电压． 相似文献
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9.
电功率是初中物理电学中的三大重点和难点之一．电功率的计算题是中考考点，本文就一道串联电功率中考试题的七种解法介绍如下．题目如图1，一个小灯泡与一个5欧的电阻串联后，接在10伏的电源上，恰能正常发光，这时小灯泡的功率为5瓦．求小灯泡正常发光时的电阻和它的额定电压．（93年河北省中考题）解法1—比例法1R1与R2串联，I1＝I2，由U＝IR可知，U与R成正比，解法2—比例法2R1与R2串联，I1＝I2，由P＝I2R可知，P与R成正比，解法3—电流规律法解法4——电压现邦法’．’R；与R：串联，．’．U—UI＋UPI’一L十人凡，解得11—… 相似文献
10.
阳水连 《中学物理教学参考》2008,(5):24-25
计算非正弦交变电流的有效值时不能应用I=Im/√2、U=Um/√、E=Em/√2公式,而要根据有效值的定义进行求解．计算非正弦交变电流有效值的步骤如下： 相似文献
11.
在市场经济迅猛发展的今天,货币的本质和职能都发生了异变,货币成了“一切价值的公分母”,使人的生活世界物化和价值通约化,从而解释了现代人“信仰危机”和情感世界失范的根源。为消除货币这一幽灵对生活世界的颠覆所产生的负面效应,借用“内圣外王”模式来重构现代人情感世界将是现代人的理智选择。 相似文献
12.
随着中国一东盟自由贸易框架协议的签订,建立自由贸易区的各项工作陆续启动,这个拥有17亿消费者,1．7万亿美元经济总量和1．23万亿美元贸易总额的经济区将为区域经济和金融合作奠定坚实的基础。中国与东盟经贸合作的开展和经济发展的深化必然要求金融领域内的交流与合作的深化,这也需要人民币区域化的进程进一步加快。中国需要在东盟货币合作中积极推进人民币区域化,这既符合整个东盟货币合作的长远利益,也符合中国的利益。这篇文章首先对最优货币区理论、人民币区域化的相关研究和人民币区域化的现状进行综述,然后借鉴国外最优货币区的实证研究方法,从劳动力要素流动的角度对中国-东盟区域的货币合作进行了实证分析,以对人民币未来的发展路径及人民币区域化的研究提供一种可行的实施方案。 相似文献
13.
Heinz von Foerster 《Instructional Science》1972,1(1):31-43
The definition of a problem and the action taken to solve it largely depend on the view which the individuals or groups that discovered the problem have of the system to which it refers. A problem may thus find itself defined as a badly interpreted output, or as a faulty output of a faulty output device, or as a faulty output due to a malfunction in an otherwise faultless system, or as a correct but undesired output from a faultless and thus undesirable system. All definitions but the last suggest corrective action; only the last definition suggests change, and so presents an unsolvable problem to anyone opposed to change (Herbert Brün, 1971).This article is an adaptation of an address given on March 29, 1971, at the opening of the Twenty-fourth Annual Conference on World Affairs at the University of Colorado, Boulder, Colorado, U.S.A. 相似文献
14.
In this study, we used a simple impregnation method to prepare Fe–Ce–O x catalysts and tested them regarding their low-temperature (200–300 °C) selective catalytic reduction (SCR) of NO using NH3. We investigated the effects of Fe/Ce molar ratio, the gas hourly space velocity (GHSV), the stability and SO2/H2O resistance of the catalysts. The results showed that the FeCe(1:6)O x (Ce/Fe molar ratio is 1:6) catalyst, which has some ordered parallel channels, exhibited good SCR performance. The FeCe(1:6)O x catalyst had the highest NO conversion with an activity of 94–99% at temperatures between 200 and 300 °C at a space velocity of 28,800 h?1. The NO conversion for the FeCe(1:6)O x catalyst also reached 80–98% between 200 and 300 °C at a space velocity of 204,000 h?1. In addition, the FeCe(1:6)O x catalyst demonstrated good stability in a 10-h SCR reaction at 200–300 °C. Even in the presence of SO2 and H2O, the FeCe(1:6)O x catalyst exhibited good SCR performance. 相似文献
15.
东亚货币放弃钉住美元的汇率制度之后,日元和人民币(尤其是人民币)在稳定东亚汇率方面发挥着更为重要的作用.建立分别以日元和人民币为核心的"次货币区"(即"双轨机制"),有利于使东亚货币合作实现真正的东亚汇率协调.从长远看,"双轨机制"引入了日元与人民币之间以及这两种货币与美元之间的双重"竞争与协调"机制,有可能对美元的"霸主"地位构成逐渐强化的挑战. 相似文献
16.
D. R. Watson 《International Review of Education/Internationale Zeitschrift für Erziehungswissenschaft/Revue internationale l'éducation》1976,16(5):41-62
In this paper, three sociological models or theoretical templates for the analysis of social order are outlined: (a) the order-consensus model, (b) the conflict model and (c) interactionist models. The paper then discusses how each model can be applied to what is here called educational redress. Special reference is made to those redress strategies addressed to pre-school-age children-strategies customarily termed Compensatory Education Programmes. The paper goes on to show how proponents of each model would approach the analysis of such programmes, and how proponents of each model would criticize the other models' analyses. It is shown that the three sociological models are located in, and formalizations of, commonsense conceptions of social structure tacitly held by lay members of society, and that even professional educators typically do not make their model of society very explicit. Finally the paper upholds the belief that the above elements constitute what sociologists can add to the understanding of educational redress strategies. 相似文献
17.
Diesel emission fluid (DEF) soaking and urea deposits on selective catalytic reduction (SCR) catalysts are critical issues for real diesel engine NH3-SCR systems. To investigate the impact of DEF soaking and urea deposits on SCR catalyst performance, fresh Cu-zeolite catalyst samples were drilled from a full-size SCR catalyst. Those samples were impregnated with DEF solutions and subsequently hydrothermally treated to simulate DEF soaking and urea deposits on real SCR catalysts during diesel engine operations. Their SCR performance was then evaluated in a flow reactor with a four-step test protocol. Test results show that the DEF soaking leached some Cu from the SCR catalysts and slightly reduced their Cu loadings. The loss of Cu and associated metal sites on the catalysts weakened their catalytic oxidation abilities and caused lower NO/NH3 oxidation and lower high-temperature N2O selectivity. Lower Cu loading also made the catalysts less active to the decomposition of surface ammonium nitrates and decreased low-temperature N2O selectivity. Cu loss during DEF impregnation released more acid sites on the surface of the catalysts and increased their acidities, and more NH3 was able to be adsorbed and involved in SCR reactions at medium and high temperatures. Due to lower NH3 oxidation and higher NH3 storage, the DEF-impregnated SCR catalyst samples showed higher NO x conversion above 400 °C compared with the non-soaked one. The negative impact of urea deposits during DEF impregnation was not clearly observed, because the high-temperature hydrothermal treatment helped to remove the urea deposits. 相似文献
18.
传统价格理论认为,价格是价值的货币表现,即价值决定价格。然而运用这一理论解释某些经济现象时遇到了困难,分析发现,价格首先是交换价值的货币表现,然而交换价值并不等同于价值,因此价格也并非完全是价值的货币表现,商品是用于交换的物品。同时,提出“交换价值=自然价值+劳动价值”的公式和“负价值”的概念。 相似文献
19.
抗战期间,根据地货币同法币的关系十分复杂,晋冀鲁豫根据地实行的“保护法币”政策有利有弊。“保护法币”不是目的。而应当看作一种策略、一种手段,在不同时期有不同内涵。 相似文献
20.
CUI Qiang HAN Yan DONG Shu-rong LIOU Juin-jie 《浙江大学学报(A卷英文版)》2007,8(12):1879-1883
A novel polysilicon-assisted silicon-controlled rectifier (SCR) is presented and analyzed in this paper, which is fabricated in HHNEC's 0.18 μm EEPROM process. The polysilicon-assisted SCRs take advantage of polysilicon layer to help bypass electro-static discharge (ESD) current without occupying extra layout area. TLP current-voltage (I-V) measurement results show that given the same layout areas, robustness performance of polysilicon-assisted SCRs can be improved to 3 times of con- ventional MLSCR's. Moreover, one-finger such polysilicon-assisted SCRs, which occupy only 947 μm2 layout area, can undergo 7-kV HBM ESD stress. Results further demonstrate that the S-type I-V characteristics of polysilicon-assisted SCRs are adjustable to different operating conditions by changing the device dimensions. Compared with traditional SCRs, this new SCR can bypass more ESD currents and consumes smaller IC area. 相似文献