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101.
物理实验的种类很多,其中测量性实验主要以测量为主;演示性实验主要以观察现象为主;验证性实验和探究性实验既有定性研究又有定量分析的成份,学生不仅要观察现象还要进行测量,并对测量结果分析概括.从物理研究的角度来看,必须经过多次实验才能总结某一结论或归纳某一规律.然而从编写教材与执教的方便考虑,现行课本上的实验在其具体过程中有一部分仅需做一次,但大部分仍安排三次以上,这些实验大都与测量有关.进行多次实验与进行多次测量的作用很多,现分类探讨. 相似文献
102.
As an advanced optical method, a multi-point pump method is presented for measurements of thermo-physical properties of liquids. Meanwhile, based on the laser-induced thermal grating method, a new theory model is presented and used to analyse the thermal effects caused by the multi-point laser pump, by which the thermal conductivity of liquids can be obtained. The results of some typical liquids, such as water, ethanol and acetone, are presented and are consistent with those of acknowledged values, demonstrating that the multi-point method is simple and useful for characterizing thermal properties of liquids. 相似文献
103.
Growth of Semi-Insulating GaN Using N2 as Nucleation Layer Carrier Gas Combining with an Optimized Annealing Time
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Semi-insulating (SI) GaN is grown using N2 as the nucleation layer (NL) carrier gas combined with an optimized annealing time by metalorganic chemical vapour deposition. Influence of using 1-12 and N2 as the NL carrier gas is investigated in our experiment. It is found that the sheet resistance of unintentionally doped GaN can be increased from 10^4 Ω/sq to 10^10 Ω/sq by changing the NL carrier gas from 1-12 to N2 while keeping the other growth parameters to be constant, however crystal quality and roughness of the tilm are degraded unambiguously. This situation can be improved by optimizing the NL annealing time. The high resistance of GaN grown on NL using N2 as the carrier gas is due to higher density of threading dislocations caused by the higher density of nucleation islands and small statistic diameter grain compared to the one using 1-12 as carrier gas. Annealing the NL for an optimized annealing time can decrease the density of threading dislocation and improve the tilm roughness and interface of AlGaN/GaN without degrading the sheet resistance of as-grown GaN signiticantly. High-quality SI GaN is grown after optimizing the annealing time, and AlGaN/GaN high electron mobility transistors are also prepared. 相似文献
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以应用型设计性实验 《教室的采光及照度的综合评价》为例, 阐述了教改新的设计思想, 并分析总结实施所取得的成果 相似文献
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(1) Introduction Most of the existing literature on input design for identification has been concentrated on the problem of obtaining accurate parameter estimates. Many of them discussed how to determine optimal inputs which minimize a scalar valued function of the inverse Fisher information matrix.The minimization has been performed under certain constraints to prevent the diverge of the input or output amplitude. 相似文献
108.
In order to systematically investigate the effects of simulated weightlessness on thefunction state of human brain, 15° head-down tilt (HDT) was used to simulate weightless-ness, and the response changes of event-related EEG power spectra, medium-frequencysynchronous potentials and slow-waves were examined in the present study. It was foundthat HDT had characteristic effects on the above EEG responses, suggesting that the ef-fects mainly occurred in the brain's regulatory system, therefore, resulting in changes ofthe brain function state. 相似文献
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测定动、植物中葡萄糖的方法较多,但灵敏度低,手续麻烦。本文提出在氨性介质中,加热活化葡萄糖分子,在pH9的NH_4OH—NH_4Cl—Na_2SO_3体系中,用差示脉冲极谱,峰电位为-1.08伏,产生一个灵敏度较高的脉冲极谱峰电流。本法分析手续简便,可用于人尿、血液、植物体和食品中低含量葡萄糖的测定,也适用于制糖、养蜂和酿酒业中高含量葡萄糖的测定。 相似文献