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981.
萃取—石墨炉原子吸收光谱法测定高纯氧化钐中的铜和铅 总被引:4,自引:0,他引:4
本文研究了APDC/MIBK萃取-石墨炉原子吸收光谱法测定高纯稀土氧化钐中的铜和铅。详细探讨了测定条件和萃取条件。该法简单,准确和适用。 相似文献
982.
983.
均匀折射率包层铌酸锂单晶光纤远离截止区的模特性讨论 总被引:1,自引:0,他引:1
给出了具有均匀折射率包层铌酸锂单晶光纤的场强颁上和本征值方程,分析了远离截止区的模特性。 相似文献
984.
Ground-based CO2 inversion accuracy determines the understanding of CO2 source and sink. However the study about factors affecting ground-based CO2 inversion. In order to improve CO2 inversion accuracy, the effects from aerosol, spectral shift, spectral band selection, spectrometer response function type, half width and truncation error have been analyzed by using radiative transfer model. The results show that: (1) the multiple scattering of aerosol can be ignored when instrument field of view is less than 1.5 degrees and aerosol optical depth is less than 0.5. (2) The inversion results are smaller when there are spectral offsets. The inversion errors increase nonlinear with spectral offsets. And the higher the spectral resolution, the larger the effect of spectral shift. (3) Different spectral bands have various average signal-to-noise ratio, selecting channels with appropriate signal-to-noise ratio and enhancing instrument signal-to-noise ratio can reduce the effect of instrument noise. (4) The higher the instrument resolution, the more important the degree of accuracy of instrument line function for simulated spectrum. Therefore, for hyper-spectral observation, the constancy of environmental temperature is key of acquiring high precision inversion results. (5) For over-high spectral resolution, simulated spectrum is anamorphic due to crosstalk effect. Therefore the crosstalk effect must be considered when the spectrometer resolution is advanced. 相似文献
985.
Analysis on high speed response of a uni-traveling-carrier double hetero-junction phototransistor 下载免费PDF全文
In this paper, the positive influence of a uni-traveling-carrier(UTC) structure to ease the contract between the responsivity and working speed of the In P-based double hetero-junction phototransistor(DHPT) is illustrated in detail. Different results under electrical bias, optical bias or combined electrical and optical bias are analyzed for an excellent UTC-DHPT performance. The results show that when the UTC-DHPT operates at three-terminal(3T) working mode with combined electrical bias and optical bias in base, it keeps a high optical responsivity of 34.72 A/W and the highest optical transition frequency of 120 GHz. The current gain of the 3T UTC-DHPT under 1.55-μm light illuminations reaches 62 d B. This indicates that the combined base electrical bias and optical bias of 3T UTC-DHPT can make sure that the UTC-DHPT provides high optical current gain and high optical transition frequency simultaneously. 相似文献
986.
有限厚度板穿透裂纹前缘附近三维弹性应力场分析 总被引:7,自引:1,他引:7
通过三维有限元计算来研究有限宽度、有限厚度含有穿透裂纹板的裂纹前缘应力场,从中找出应力强度因子与板的厚度、裂纹长度之间的关系,同时还分析了裂尖的三维约束程度和三维约束区的大小。分析结果表明:应力强度因子沿厚度的分布是不均匀的,应力强度因子的最大值及其位置与厚度有关;有限厚度板中面应力强度因子(KI)m-p及最大应力强度因子(KI)max均大于平面应力或平面应变的应力强度因子。对有限厚度裂纹问题,按平面应力或平面应变来考虑是不安全的;板中面的应力强度因子(KI)m-p及最大应力强度因子(KI)max是厚度B/a的函数;板的中面离面约束系数Tx最大,自由面(z=B)Tx=0。沿厚度方向裂尖附近的离面约束系数Tx也是z/B和B/a的函数,随着厚度的增加离面约束系数Tx增大,离中面越近离面约束系数Tx越大。Tx随着x的增大急剧减小,三维约束影响区域大小大约为板厚的一半,且裂纹长度a/W对应力强度因子沿厚度变化规律及Tx影响区域大小影响较小。 相似文献
987.
We study here the thermally-induced martensitic transformation process of shape memory alloys. Taking the internal energy
of phase mixtures as the potential function and introducing coherency energies between martensite and austenite and between
different variants of the martensitic phase, we are able to use thermodynamical arguments to obtain hysteresis diagrams which
could be measured experimentally. The characteristic temperatures for martensitic transformation, (martensite start and finish) and (austenite start and finish) can be identified explicitly and are closely related to the coherency parameters of the coherency
energies.
Received September 12, 1997 相似文献
988.
This is a continuation of [1]. In [1] we suggested a method of direct perturbation of partial differential equation and weighted integration to calculate the periodic solution for continuum mechanics. In this paper, by using the above method we calculate the resonant and nonresonant periodic solutions of beam with fixed span and different boundary conditions and the resonant periodic solution of square plate under the action of concentrated periodic load. Besides, the influences of nonprincipal mode upon periodic solution and of static load upon amplitudefrequency curve are given. 相似文献
989.
Cuihong Zhang Yuan Ge Xiaoping Huo Jing Xue Kexuan Li Yongming Zhang Zongcheng Miao 《先进技术聚合物》2020,31(3):544-552
In this paper, polymer‐dispersed liquid crystal (PDLC) films consisting of liquid crystal (LC)/monomers/indium tin oxide (ITO) nanoparticles with good near‐infrared absorption property had been fabricated, and the influence of the ITO nanoparticles modified with 3‐methacryloxypropyltrimethoxysilane (KH570) on the PDLC films was systematically studied. First, different liquid crystal content was studied to obtain PDLC films with good electro‐optical properties. And then, various weight ratio of ITO nanoparticles was added to samples. While the content of ITO nanoparticles was increased, the saturation voltage increased and the CR decreased. Though the electro‐optical properties of PDLC samples reduced with the addition ITO nanoparticles, the near‐infrared absorption property of films was enhanced. 相似文献
990.
过渡金属催化的卡宾对X-H(X=C,Si,N,O,S)键的插入反应是卡宾的一类特征反应,在有机合成中应用广泛[1].其中N-H键插入是构建C—N键的一种高效方法,特别是相应的不对称催化,对合成含氮手性化合物具有重要意义.近年来,人们以芳香胺或酰胺作为底物,在手性过渡金属催化剂的存在下,实现了卡宾对其N—H键高对映选择性的插入反应,从而发展了天然或非天然α-手性氨基酸衍生物合成的新方法[2]. 相似文献