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71.
Khang Hoang 《固体物理学:研究快报》2016,10(12):915-918
Erbium (Er) doped GaN has been studied extensively for optoelectronic applications, yet its defect physics is still not well understood. In this work, we report a first‐principles hybrid density functional study of the structure, energetics, and thermodynamic transition levels of Er‐related defect complexes in GaN. We discover for the first time that ErGa–CN–VN, a defect complex of Er, a C impurity, and an N vacancy, and ErGa–ON–VN, a complex of Er, an O impurity, and an N vacancy, form defect levels at 0.18 eV and 0.46 eV below the conduction band, respectively. Together with ErGa–VN, a complex of Er and an N vacancy which has recently been found to produce a donor level at 0.61 eV, these defect complexes provide explanation for the Er‐related defect levels observed in experiments. The role of these defects in optical excitation of the luminescent Er center is also discussed. 相似文献
72.
需求势能理论的配送中心选址方法的研究 总被引:4,自引:0,他引:4
物流配送中心选址的合理性直接影响着物流分销网络规划和优化.提出了针对物流网点选址的需求势能理论,并提出了一种基于需求势能的分销物流系统中配送中心的选址实现方法.最后通过实例证明,该方法简便快捷,结果正确合理,为解决此类配送中心选址问题提供了科学的指导依据. 相似文献
73.
Zhijun Yi Tingyu LiuQiren Zhang Yuanyuan Sun 《Journal of Electron Spectroscopy and Related Phenomena》2006
The electronic structures of PbWO4 crystals containing F type color centers with the lattice structure optimized are studied within the framework of the fully relativistic self-consistent Direc–Slater theory, using a numerically discrete variational (DV-Xα) method. The calculated results show that F and F+ centers have donor energy level in forbidden band. Their optical transition energy are 1.84 eV, 2.21 eV, respectively, which corresponds to the 680 nm, 550 nm absorption bands. It predicts that the 680 nm, 550 nm absorption bands originate form the F and F+ centers in PbWO4 crystals. 相似文献
74.
75.
Bobik V. V. Bobonich F. M. Belokopytov Yu. V. 《Theoretical and Experimental Chemistry》2003,39(6):364-368
We have used potentiometric titration with tetrabutylammonium hydroxide to determine the acid center content on the outer surface of dealuminated natural and synthetic mordenites. We have established a symbatic relationship between the 2,2-dimethylbutane content in the hydroisomerization products of n-hexane on dealuminated palladium-containing mordenites and the number of their external acid centers. We have studied the possibility of partial deactivation of such centers during ion-exchange deposition of palladium on the catalysts, using a tetraammine palladium solution. 相似文献
76.
R. G. Thompson P. S. Dharmapala J. Diaz M. D. González-Lima R. M. Thrall 《Annals of Operations Research》1996,66(2):163-177
The setE of extreme points which are also efficient are of basic importance in defining the efficiency frontier, from which the observations for all other DMUs are evaluated in DEA. A significant question which we address is “What variations in the data can be tolerated before the membership inE is changed?” This topic is explored using (1) a simple illustrative example, and (2) production data for 30 independent oil companies during the period 1983–1985. Data were allowed to vary simultaneously for all observations and in different subsets determined by random drawings of data for points both inE and not inE. The results were found to be robust in this study, thereby lending further support to earlier studies which also found these classifications into efficient and inefficient performers to be robust in DEA. Technical developments for these new methods of sensitivity analysis are supplied. These developments feature an application of analytic center (interior point) algorithms which ensure that the Strong Complementary Slackness Condition (SCSC) is fulfilled. The solutions satisfy a mathematical condition called “centrality”. Generally, the solutions are at interior points calledanalytic centers. At these interior points, continuity of the input-output ratios ensures that DMUs inE remain inE for at least small relative variations in the data, while empirically these properties have been found to extend to much larger variations in the data sets. 相似文献
77.
The diffuse reflection spectroscopy technique was used to investigate the color centers (CC) in the products of thermolysis
and photolysis of disperse Al(OH)3 in a vacuum. The spectra were recorded in situ in the region of 2.5–6.0 eV and 4000–12,000 cm−1. It was found that in thermolysis of Al(OH3) production of Al is accompanied, by transformation of the IR spectra of the compound and overtone vibrations of OH groups
and by the appearance of an absorption band (AB) at 4.0 eV with a shoulder at 4.4 eV. A similar AB is induced by UV irradiation
of Al(OH)3 in a vacuum. In the position of the maximum and shape, the AB at 4.0 eV in aluminum oxide produced by thermolysis of Al(OH)3 coincides with the AB of CC responsible for light- and temperature-stimulated degradation of white anode oxide coatings on
Al(Al-AOC). This suggests that in Al-AOC, CC are formed in decay of structural OmHn groups. In Al oxide and in Al-AOC, their nature is discussed with the use of data on optical absorption of radiation-induced
defects in Al2O3.
Research Institute of Physics at St. Petersburg State University, St. Petersburg 1, Ul’yanovskaya St., Petrodvorets St. Petersburg,
198904, Russia. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 3, pp. 400–404, May–June, 1998. 相似文献
78.
针对多阶段区间信息集结与决策问题,提出一种考虑最小化集结矩阵与阶段区间矩阵之间距离的新方法,寻求更趋近帕累托最优的集结结果,使最终评价值更符合多阶段评价的目标。 首先,根据多阶段专家评价值将区间信息转化为二维坐标点,并将其映射到二维坐标系中。然后,构建区间信息离差最小化集结模型,并基于植物模拟生长算法(PGSA)进行群体判断信息的集结,再通过合成各方案的属性评价值,给出各决策方案的综合评价值并进行排序,进而给出最优决策方案。最后,以物流服务商的多阶段绩效评价为例,验证了该方法的合理性和有效性。 相似文献
79.
80.