共查询到20条相似文献,搜索用时 171 毫秒
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对速度的合成与分解以及区分合速度与分速度的原则与基础进行了讨论,阐明了拉绳速度的意义,它名副其实,充分体现了拉绳二字的作用.对绳上任一点的运动轨迹给出了一个简明的物理解释.阐明了船靠岸的加速度随距离的减小而迅速增大的物理含义,并给予了解释.最后还探讨了一种奇异的(无中生有的)倒解法,即从船的加速度a的表达式(式中不含a’)求出雪橇的加速度a’;反之亦然.附带对一些似是而非的疑难问题进行了简要的讨论,回答了这究竟是不是速度合成与分解的问题. 相似文献
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本文较系统地研究了色谱/原子吸收光谱联用的工作条件对测定烷基铅的影响,选择了分析条件,并对烷基铅样品进行了分离与测定。分析结果的相对标准差为3.31~4.12%,回收率为94.6~104.0% 相似文献
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本文报道了对87Rb冷原子云聚焦的微磁透镜实验.磁透镜的核心部件是一个半径为2mm的微型线圈.当冷原子云沿线圈轴向运动到线圈附近时,线圈产生的非均匀磁场会对原子云实现纵向压缩.在线圈电流加载时间为10ms的情况下,原子云纵向尺寸随线圈电流增加先表现为会聚趋势;在某一电流值(0.9A)之后,表现为扩散趋势.与不加载线圈电流的情形相比较,电流为0.9A时的冷原子云纵向尺寸缩小了一个多量级,透镜焦距约为1.3mm.通过同时调节线圈电流的大小和作用时间,可实现对透镜焦距的调节.同时用数值模拟方法模拟了实验过程,模拟结果与实验结果基本符合. 相似文献
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氟分子与乙烯可以发生三类反应,即氟原子排除反应、氟化氢分子排除反应和加合反应,但除了基机制以外,已有的其它机理都不能合理的解释低温下的反应是如何开始的.通过对氟分子与乙烯反应的直接动力学模拟,以密度泛函方法研究了长期困扰的氟分子与乙烯反应的机理.通过计算支持了基机制,轨线模拟细致地描述了三个反应通道.根据此机制对低温池中的反应给出了解释. 相似文献
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The coupling of visible nanosecond laser pulses to metallic targets irradiated in vacuum is studied. The expressions of the vapour and plasma ignition times are obtained. Two cases for vapour breakdown in the plasma ignition process are considered. The first case is that 40 generations of new electrons are born in vapour generation time before plasma formation as assumed in the literature. The second case is that 10 generations of new electrons are born in vapour generation time. Molybdenum (Mo), niobium (Nb) and aluminium (Al) targets are considered for illustrations of our results. The expression of the plasma ignition time for the Al target is substantially different from that reported in the literature. The vapour and plasma ignition threshold laser intensities are calculated and compared with those reported in the literature. Reasons for disagreement are discussed. The plasma ignition threshold estimated in the second case is noted to be in good agreement with the reported experimental result. 相似文献
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用于高速数据通信的梯度塑料光纤 总被引:1,自引:0,他引:1
概述了梯度塑料光纤的开发历史和现状。从应用于高速数据通信的角度 ,介绍了聚甲基丙烯酸甲酯(PMMA)、全氘化和全氟化梯度塑料光纤的损耗、带宽、稳定性和寿命。详细介绍了梯度塑料光纤的损耗光谱和损耗机制 ,介绍了制作梯度塑料光纤的界面凝胶聚合技术和两种扩散法 ,分析了梯度塑料光纤的制作方法同折射率剖面和带宽的关系 ,讨论了梯度塑料光纤的稳定性同掺杂物质的关系。同时介绍了高稳定性梯度塑料光纤的研究进展及今后的发展动向 相似文献
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亲水性材料固相萃取-紫外导数光谱法检测血中茚满二酮灯抗凝 … 总被引:6,自引:1,他引:5
本文报导了血中茚满二酮类抗凝血杀鼠剂敌鼠、氯敌鼠、杀鼠酮的亲水性材料固相萃取-紫外导数光谱检测法。血样用pH5缓冲液等体积稀释后加于西雷脱硅藻土柱上,柱用乙酸乙 酯洗脱,将洗脱液挥发干净,剩余物用pH10缓冲液溶解,测定所得溶液的二阶导数光谱进行定性和定量分析。三种杀鼠剂以10mg/L的量加于空白血中测得萃取率为85%以上,血中三种杀鼠剂的检出限低于2mg/L。萃取中亲水性硅藻土可用硅胶和氧化铝代替, 相似文献
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光学合成孔径系统的光束控制 总被引:1,自引:0,他引:1
本文给出真空中光学合成孔径系统光束控制的物理模型。计算机数值模拟结果与理论分析吻合。另外,对孔径的活塞型和倾斜型误差的影响也进行了探讨。 相似文献
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(1)H-(14)N nuclear quadrupole double resonance using magnetic field cycling between high and low magnetic field and solid effect in the low magnetic field is analyzed in details. The transition probabilities per unit time for the solid-effect transitions are calculated. The double resonance spectra are calculated in the limiting cases of fast and slow nitrogen spin-lattice relaxation. The double resonance spectra are measured in histamine and quinolinic acid. The experimental spectra are analyzed and the (14)N NQR frequencies are determined. 相似文献
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The electronic structure of hydrogen and muonium in simple metals is investigated. The spherical solid model potential is
used for the discrete lattice and the Blatt correction for lattice dilation. The proton and muon are kept at the octahedral
sites in the fcc and hcp lattices and self-consistent non-linear screening calculations are carried out. The scattering phase
shifts, electronic charge density, effective impurity potential, self-energy, charge transfer, residual resistivity and Knight
shift are calculated. The spherical solid potential changes the scattering character of impurity. The phase shifts are found
slowly converging. The scattering is more prominent in Al than in Mg and Cu. The virtual bound states of proton and muon are
favoured in all the three metals. The calculated value of residual resistivity for CuH is in good agreement with the experimental
value. The results for Knight shift forμ
+ in Cu and Mg are in reasonable agreement with the experimental values while those forμ
+ in Al are lower than the experimental value. The analytical expressions for effective impurity potential and electronic charge
density are suggested. 相似文献
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Adam W. Marczewski 《Applied Surface Science》2007,253(13):5818-5826
Static and kinetic studies on adsorption of nitrobenzene, 4-nitrophenol and 4-chlorophenol on two mesoporous carbons are performed. The carbon properties are analyzed by means of nitrogen adsorption. The adsorption experiments are performed in acidic buffer solutions in a wide range of concentrations. The static experiments are analyzed by means of Langmuir-Freundlich and Freundlich isotherms. The Lagergren, pseudo-second-order, intraparticle-diffusion and multi-exponent equations are used in the analysis of kinetic equilibria. 相似文献
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The results of Monte Carlo simulations of xenon monolayers deposited on graphite are presented. Systems of various surface densities and in a wide range of temperatures are investigated. The results are compared to the experimental data and to the previous results for nitrogen. The results of simulations are in good agreement with the experimental ones and confirm that melting in two dimensions is vacancy-driven. Typical real-space configurations of Xe atoms and calculated specific heat results are shown. 相似文献