类比法在场效应管及其放大电路教学中的应用

模拟电子技术教学内容多,知识点琐碎,学生普遍感觉入门难,而场效应管及其放大电路又是模拟电子技术教学难点之一,传统的教学使教学效果不尽人意.双极型晶体管（BJT）和场效应管（FET）都是半导体器件,二者有很多相似之处,因此巧用类比法将FET与BJT进行对比教学,不但可以提高教学效率,达到事半功倍的效果,而且可以使学生温故知新,找到新旧知识之间的联系,减少对新知识的畏难情绪,提高学习兴趣和学习效率.     

电池电动势和内阻测量实验方案创新改进

伏安法测量电池的电动势、内阻及其实验创新,是高中物理实验探究的重要内容,考查学生的理解能力、推理能力和动手能力,培养学生的科学探究、科学态度的学科素养.本文从该实验的原理出发,介绍电池电动势和内阻测量实验方案的创新设计,并列举两道典型例题,希望帮助学生发散思维,打开想象的大门.     

电位差计测电池电动势的探讨

结合教材与实验教学分析用电位差计测量电池电动势原理中,补偿回路中一段电阻两端的电压平衡的不是电池的电动势而是电池的端电压,从而阐明电位差计测出的是电池的端电压,而非电池的电动势。     

不同状态下电池的电动势

电池只所以能够进行工作,就是由于电池内进行着化学反应。一定数量的电荷在电池内由阴极流到阳极,而在电池外面的电路中电荷则由正端流向负端。由于电路中有电流通过,就必然会放出热量,其热量大小与电流强度的平方成正比,这个现象称为焦耳效应。很显然,焦耳效应是一个不可逆现象。为了尽量减除焦耳效应,并使电池内化学反应达到平衡,从而得到最大的电动势,我们可外加一个反电动势-E,恰好几乎抵消电池的电动势E。这时通过的电量dq为无穷小量,过程是可逆的,外界对电池所作的功为-Edq,而电池对外界所作之功必为Edq。     

板式电位差计测量电池电动势的不确定度评定

用适当简化处理的不确定度计算方法，分析板式电位差计测量电池电动势实验测量结果的不确定度，给出一种合理的不确定度评定方案．     

电源电动势和内阻的测量方案

测量电源的电动势和内电阻是高考考试大纲中指定的实验,关注大纲中指定的实验以及相关的例题、习题抓好对实验原理的理解,对基本仪器的应用,不要坠入“只重视背、记实验操作步骤,忽略观察能力和推理能力的提高”的误区。本文从课本上一道例题出发用多种方法研究了电源电动势和内阻的测量方法,并给出了具体的实例,这对学生深入理解全电阻欧姆定律有很好的启发性。     

谈测量电池的电动势和内阻误差的分析方法

由于实验原理不完善,实验仪器本身不精确,实验者自身的操作行业不规范,致使实验存在着误差．如何使实验做得更精确呢？进行误差分析就为完善实验原理、精确实验操作提供了有力的依据,同时进行误差分析需要选取合适的分析方法．因此,归纳误差分析的方法是非常重要的．本文就U-I,法测量电池的电动势和内阻的误差分析的方法进行探讨．     

浅谈测量电池电动势和内电阻的实验方法及误差分析

本文总结了测量电池电动势和内电阻的实验方法;应用闭合电路欧姆定律,通过定量计算,对各种实验方法进行了误差分析,指出了各种实验方法减小系统误差的方向;还对误差分析进行了应用举例。     

高中生视阈下《测量电池的电动势和内阻》实验研究

对高中《测量电池的电动势和内阻》的实验从实验原理、实验设计、误差分析几个角度进行了分析研究。     

The effect of Jujuboside A on the evoked field potentials of granule cells in dentate gyrus

Jujuboside A (JuA) is a main component of Jujubogenin extracted from the seeds of Ziziphus. The authors have not seen any report on JuA's direct effect on the neurons of the central nervous system. This study aimed to assess the effect of JuA on paired-pulse responses of dentate gyrus granule cells in urethane-anaestherized rats, used intracerebroventricular (i. c. v.) JuA to mimic in vitro bath conditions in vivo. Paired-pulse stimuli with 80ms interpulse interval were used to stimulate the perforant pathway. Evoked responses were recorded in the dentate gyrus cell layer after i. c. v. administration of 0.9% normal saline or JuA. In the first responses, the slopes of excitatory postsynaptic potential (EPSP1) and the amplitudes of population spike (PS1) decreased significantly after administration of JuA while the PS1 latencies increased significantly. In the second responses, the EPSP2 slopes and PS2 latencies were changed similarly to those of the first ones, but PS2 amplitudes increased. The results showed that JuA may have some inhibitory effect on the granule cell excitability mediated by presynaptic mechanism but may have little effect on the excitability mediated by postsynaptic mechanism since the second evoked N-methyl-D-aspartic mediating paired-pulse facilitation is a postsynaptic mechanism. Project supported by the National Key Scientific and Technological Planning Fund of China (Grant 99-929-04-03), and by the Visiting Scholar Fund of Key Laboratory from the Education Ministry of China     

Performance evaluation of minimum quantity lubrication by vege- table oil in terms of cutting force, cutting zone temperature, tool wear, job dimension and surface finish in turning AISI-1060 steel

In all machining processes, tool wear is a natural phenomenon and it leads to tool failure. The growing demands for high productivity of machining need use of high cutting velocity and feed rate. Such machining inherently produces high cutting temperature, which not only reduces tool life but also impairs the product quality. Metal cutting fluid changes the performance of machining operations because of their lubrication, cooling and chip flushing functions, but the use of cutting fluid has become more problematic in terms of both employee health and environmental pollution. The minimization of cutting fluid also leads to economical benefits by way of saving lubricant costs and workpiece/tool/machine cleaning cycle time. The concept of minimum quantity lubrication （MQL） has been suggested since a decade ago as a means of addressing the issues of environmental intrusiveness and occupational hazards associated with the airborne cutting fluid particles on factory shop floors. This paper deals with experimental investigation on the role of MQL by vegetable oil on cutting temperature, tool wear, surface roughness and dimen- sional deviation in turning AISI-1060 steel at industrial speed-feed combinations by uncoated carbide insert. The encouraging results include significant reduction in tool wear rate, dimensional inaccuracy and surface roughness by MQL mainly through reduction in the cutting zone temperature and favorable change in the chip-tool and work-tool interaction.