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在一些测量密度的实验题目中,在所给的器材中常会出现水.实际上这类题目能否顺利解决的关键,就是能否将水巧妙地用到实验中来,帮助我们解决遇到的困难.下面介绍几个用水帮助完成密度测量的实验题. 相似文献
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First-principles study of structural and opto-electronic characteristics of ultra-thin amorphous carbon films 下载免费PDF全文
Most amorphous carbon(a-C)applications require films with ultra-thin thicknesses;however,the electronic structure and opto-electronic characteristics of such films remain unclear so far.To address this issue,we developed a theoretical model based on the density functional theory and molecular dynamic simulations,in order to calculate the electronic structure and opto-electronic characteristics of the ultra-thin a-C films at different densities and temperatures.Temperature was found to have a weak influence over the resulting electronic structure and opto-electronic characteristics,whereas density had a significant influence on these aspects.The volume fraction of sp3 bonding increased with density,whereas that of sp2 bonding initially increased,reached a peak value of 2.52 g/cm3,and then decreased rapidly.Moreover,the extinction coefficients of the ultra-thin a-C films were found to be density-sensitive in the long-wavelength regime.This implies that switching the volume ratio of sp2 to sp3 bonding can effectively alter the transmittances of ultra-thin a-C films,and this can serve as a novel approach toward photonic memory applications.Nevertheless,the electrical resistivity of the ultra-thin a-C films appeared independent of temperature.This implicitly indicates that the electrical switching behavior of a-C films previously utilized for non-volatile storage applications is likely due to an electrically induced effect and not a purely thermal consequence. 相似文献
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学生解题时,常出现各种各样的错误,大致上可归为以下几种类型.1 概念不清而致误 正确理解概念是正确解题的关键,有的同学常因概念认识不清,导致错误的解答.1.1 不顾条件用物理模型致误 任何模型均具有局限性,不存在无局限性的模型,忘了它的局限性就会犯错误.如:质点模型,当一个物体的形状、大小在所研究的 相似文献
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在2015年版《中国药典》的基础上,采用原子荧光光谱法和电感耦合等离子体质谱法对黄芪口服液中的铅、砷、镉、汞、铜、锌、镍和铬进行测定,并对所用试剂、器皿,赶酸时间,内标的种类和加入方式进行了优化。结果表明,在样品处理前对器皿采用硝酸(30%)处理,赶酸时间在1.5h以上,以手动方式加入单内标103 Rh溶液,可以得到较准确、稳定的测定结果,8种元素测定的相对标准偏差(RSD)均小于4%,Hg、As、Cu、Pb、Zn、Cd、Ni、Cr的检出限分别为0.089、0.21、0.45、0.15、0.45、0.025、0.35和0.39μg/L,8种元素的加标回收率在92.0%~114%。方法对于黄芪口服液中痕量元素的检测,结果稳定,过程简单,引入污染小。 相似文献
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A readout system for X-ray CCDs based on an improved architecture is presented; by optimizing several critical circuit blocks along the analog signal chain, the conflict between the readout speed and readout noise is greatly alleviated. Using CCD47-10 as its target CCD, the readout system has achieved 8.6e- readout noise and 142 eV FWHM at 5.9 keV Mn m Kα under a pixel rate of 80 kHz. Also its performance of imaging has been investigated. 相似文献
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1 选购 高像素选购数码相机(DC),高像素是不可缺少的基本要求,输出为A4照片起码需要300万像素,如果有500万像素更好,此外如果拍摄技巧不足,可以用像素来弥补,缩小相片尺寸,同样能够得到较好的效果. 相似文献