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The structural and electronic properties of the CdSe nanoclusters, which have been intended to model quantum dots, have been examined by means of time-dependent density functional (TDDFT) calculations. The optical spectra were first simulated using the standard linear response implementation of the TDDFT (LR-TDDFT) in a series of calculations performed using different basis sets and exchange–correlation functionals. In a second step, the real-time TDDFT implementation (RT-TDDFT) was used to simulate the optical absorption spectra of the CdSe nanoclusters, both naked and capped with ligands. In general, we found that the RT-TDDFT approach successfully reproduced the optical spectrum of CdSe clusters offering a good compromise to render both the optical and the geometrical properties of the CdSe clusters at lower computational costs. While for small systems, the standard TDDFT is better suited, for medium- to large-sized systems, the real-time TDDFT becomes competitive and more efficient. 相似文献
945.
This paper presents a stochastic dynamic mathematical model, in which a Family Policy Index (XFPI) is included to measure and compare two different models of provision of resources to support families with children from 0 to 3 years old. The main variables in this model are the XFPI, fertility, mortality, emigration and immigration rates. This mathematical model was validated in two different countries, Spain and Norway, during the 2007–2015 period. A sensitivity analysis was applied to simulate the future trend (2016–2030), examining the influence of providing public pre-school services (0 to 3 years) on (XISF). The results obtained show that these services may indeed have an influence on fertility rates, as long as they are developed extensively. 相似文献
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David Díez Ana B. Antón Javier Peña Pilar García Narciso M. Garrido Isidro S. Marcos F. Sanz Pilar Basabe Julio G. Urones 《Tetrahedron: Asymmetry》2010,21(7):786-793
This paper describes an anomalous behaviour of the Sharpless dihydroxylation of a terminal olefin. The synthesis of a new chiral pyrrolidine and its application as an organocatalyst in the Michael addition of cyclohexanone into nitrostyrenes are described. 相似文献
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建立了基于能耗和剩余能量约束的无线传感器网络数据收集模型.提出了一种新的基于目标偏差度函数的启发式算法,该算法根据前次计算的结果和约束要求以及自适应动态调整目标函数加权系数的取值,避免了无效重复计算,使算法始终朝着有效的方向搜索.仿真分析表明本算法在网络存活时间指标上优于最小能耗算法;在算法的时间复杂度和搜索成功率上优于k-Dijkstra算法. 相似文献
950.
Velasco-Negueruela A Pérez-Alonso MJ Pérez de Paz PL Palá-Paúl J Sanz J 《Journal of chromatography. A》2006,1108(2):273-275
The volatiles from the fruits of Ammodaucus leucotrichus subsp. leucotrichus and subsp. nanocarpus (two endemic species, the first from North Africa and the second from the Canary Islands, Spain) were studied by gas chromatography and gas chromatography-mass spectrometry. The major components of the volatiles of subsp. nanocarpus were found to be, beta-pinene (22.2-33.6%), bornyl angelate (20.6-21.8%) and camphor (8.3-11.7%) whereas in the fruits of subsp. leucotrichus, the main constituents were perillaldehyde (63.6%) and limonene (26.8%). We also suggest that subsp. nanocarpus should have the status of species and should be named Ammodaucus nanocarpus. 相似文献