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991.
Positron binding by the HCN molecule was studied within a modified adiabatic approximation. This approach, in which the positron is treated as a light pseudonucleus with fractional charge, leads to the binding energy of 0.65?mHartree. Using effective positron mass which reproduces the Quantum Monte Carlo binding energy gives an estimation of the two-photon annihilation rate of e +HCN, equal to 0.091?ns?1. 相似文献
992.
A semiclassical dynamics simulation study is reported for a trans–cis photoisomerization cycle of four azo compounds, including azobenzene, 2-methylazobenzene, 2,6-dimethylazobenzene, and 2,2′-dimethylazobenzene. For both trans?→?cis and cis?→?trans isomerization processes, each compound is excited by a 50?fs (fwhm) laser pulse with a photon energy leading to a ππ* excitation. It is found that the compound in both cases follows a rotational path from reactant to product and that the isomerization dynamics is significantly affected by substitution. The relative times for completing a trans–cis isomerization cycle for four compounds, 2,6-dimethylazobenzene?>?2,2-dimethylazobenzene and 2,6-dimethylazobenzene?>?2-methylazobenzene>?azobenzene, follow the same order as for the photoinduced formation of the surface relief grating of polymers based on these four compounds. The simulation results provide a basis for understanding the surface relief grating formation of azobenzene-based materials upon irradiation with laser beams. 相似文献
993.
Hydrophobic bimetallic catalysts of Pt-M on styrenedivinylbenzene were prepared, where M represents successively: Ir, Rh, Pd, Cu and Ag. The total metal loading was 0.5 wt% and the weight fractions of the metal M were: 0.0,0.05,0.1,0.25,0.5,0.75 and 1.0. For each sample, the catalytic activity for H/D exchange between hydrogen and water vapor was measured. In case of monometallic catalysts, no activity was detected for M = Cu and M = Ag, and the order of the activity values for the other metals was: Pt < Ir < Rh < Pd. For each bimetallic catalyst, the activity measurements indicated a clear interaction between the platinum and the second metal, thus the activity was significantly increased for M = Ir, increased for M = Rh, decreased for M = Pd, drastically decreased for M = Cu and M = Ag. 相似文献
994.
K. Krawielitzki T. Zebrowska R. Schadereit J. Kowalczyk F. Kreienbring 《Isotopes in environmental and health studies》2013,49(1-2):157-162
Abstract Three female pigs (LW~30 kg) were fitted with re-entrant cannulas in the duodenum and the ileum and with bladder catheters. Animal No. 1 was labelled by continuous infusion of [15N]leucine via a catheter into the vena jugularis. After reaching a steady state in the level of endogenous N (4–5 d after beginning of the infusion) the digesta of the labelled animal No. 1 and the two unlabelled animals were exchanged in a 3 day experiment. During this time the course of transit rates of digesta, digesta N and 15N through duodenum and ileum as well as the proportion of endogenous N: exogenous N were estimated. Using these data it was possible to calculate the secretion and absorption rates of endogenous and exogenous N in the three segments of the digestive tract: mouth-duodenum, duodenum-ileum, ileum-anus and in addition the reabsorption (intestinal recycling) of the endogenous N during its passage through the gut could be computed. 相似文献
995.
996.
空地链路上的微波信号受降雨影响, 会产生功率衰减和去极化效应. 基于这些物理特性, 本文提出利用1–10 GHz空地链路信号的降雨干扰项获取雨强的方法, 并开展了相关理论研究. 根据空地链路信号与雨滴复杂的相互作用, 研究了空地链路信号频率为1–10 GHz时, 雨强 (rain rate, R) 对衰减 (attenuation, A) 和交叉极化分辨率 (cross-polarization discrimination, XPD)的影响, 分别建立了A-R和XPD-R关系模型. 通过数值模拟, 分别分析了利用上述两个关系模型估测雨强的可行性, 并系统研究了不同频率、极化方式和仰角条件下的适用性. 研究结果表明, 对于水平极化或圆极化, 且频率较高的空地链路信号, 利用A-R关系反演强降雨具有理论上的可行性; 对于不同频率和极化方式的信号, XPD-R关系模型都可以用于反演雨强, 并且对于1–50 mm·h-1范围内的雨强, XPD较为敏感; 不同仰角条件下, A-R和XPD-R 模型都适用. 在4–10 GHz时, 本文的XPD-R模型和国际电信联盟ITU-R中XPD预测模型的结果非常接近. 所得出的结论对于下一步开展相关的验证实验, 拓展卫星系统的气象应用, 实时估测降雨强度, 实现全球降雨观测具有重要的参考价值.
关键词:
空地链路信号
雨强
衰减特性
交叉极化分辨率(XPD) 相似文献
997.
998.
999.
Plasma‐solution interface plays the important role in the systems of the electrical discharges with or in liquids (electrolyte solutions). Processes, which pass at this interface, influence on as plasma as liquid. In this paper, the theoretical and experimental results of studies of the double layer on the liquid surface are presented. Data of cathode region properties, kinetics of nonequilibrium vaporization, correlation between radiation intensity and fluxes from electrolyte cathode surface and energy consumptions per on one water molecule transfer are summarized. It is able to suggest the transfer mechanism at the plasma‐solution interface. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
1000.
采用共沉淀法制备了不同Eu3+掺杂浓度的Gd2(WO4)3纳米发光材料. 测量了纳米材料样品的X射线衍射谱(XRD) 和场发射扫描电镜, 对样品的结构和形貌进行了表征. 测量了各样品的发射光谱和激发光谱(声子边带光谱), 绘制了浓度猝灭曲线, 确定了最佳的掺杂浓度为20 mol%. 通过声子边带光谱计算了不同掺杂浓度样品的黄昆因子. 测量了不同浓度样品的荧光寿命, 利用Auzel模型对Eu3+ 5D0能级荧光寿命数据进行了拟合, 确定了5D0能级的固有寿命和猝灭过程中生成的声子数. 本文还根据荧光寿命数据计算了Eu3+之间的能量传递速率, 确定了能量传递速率与浓度的关系.
关键词:
钨酸盐
3+')" href="#">Eu3+
黄昆因子
能量传递速率 相似文献