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各种材料的金属丝在市场上容易购得,所以本线胀系数测定实验采用细截面金属丝.实验装置如图1所示.在待测金属丝上用刀刃压出两个痕迹,测量出两压痕间距l,然后该金属丝的一端固定在玻璃管下端橡胶塞上,另一端穿过玻璃管,玻璃导管和滑轮与砝码相连.砝码的作用是使玻璃管内的金属丝保持直线状态,因此砝码的重力尽可能小一些为宜,所加砝码量能使金属丝保持直线即可.在未通恒温水时,用温度计测出玻璃管内的温度T1,用移测显微镜测量两压痕位置A1,B1.然后接通恒温水,待温度稳定后测出玻璃管内的温度T2和两压痕的位置A2… 相似文献
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比重瓶测固体密度影响实验结果的因素 总被引:1,自引:0,他引:1
本主要介绍了在用比重瓶测定不规则小粒固体密度时,影响实验结果的几个因素,并分析和讨论了诸因素对实验结果产生的误差大小。 相似文献
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BN films were synthesized on the (100)-oriented surface of n-Si (0.008-0.02Ωm) by rf magnetron sputtering physical vapor deposition (PVD). A BN film was first treated with H2 plasma for 60 rain and then the H2 treated sample was treated with O2 plasma for 15rain. The films were characterizes by using Fourier transform infrared spectra (FTIR) and atomic force microscopy (AFM). The field emission characteristics of BN films were measured in an ultrahigh vacuum system. A turn-on electric field of 8 V/μm and a current of 400μA/cm^2 were obtained for the BN film treated with H2 plasma. The results show that the surface plasma treatment makes no apparent influence on the surface morphology of the BN films. The transformations of the sample emission characteristics have to do with the surface negative electron affinity (NEA) of the films possibly. The turn-on electric field of the BN film treated with H2 plasma is lower than that without treatment, which possibly attributes to the surface NEA effect. The surface NEA of the H2 treated BN film is lost after O2 plasma treatment. 相似文献
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通过移动变倍组和补偿组,在保证所要求的变焦倍率的同时,考虑高级像差对最佳像面的影响,调整各组之间的间隔,使之尽量符合各焦距最佳像面的位移变化,最终达到在各种焦距位置时对高斯像面的严格一致。 相似文献
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