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971.
运用密度泛函离散变分(DV-Xα)方法研究了NaCl晶体中可能存在的色心,模拟计算得到含色心的NaCl晶体的电子结构.计算结果表明,F、F2心在禁带中引入了新的能级;分析了可能存在的光学跃迁,并用过渡态方法计算得到相应的跃迁能量为2.74eV和1.74eV.该计算结果与实验测得的吸收光谱的峰值位置吻合较好.而F^+心不存在光学跃迁吸收,但使晶体的禁带宽度变窄.计算结果还解释了NaCl晶体吸收光谱的结构起因. 相似文献
972.
封闭法测量平面度误差的研究 总被引:2,自引:0,他引:2
本文按顺序推导出封闭法测量平面度误差的全部计算公式,并举实例说明它的应用。该项研究为平板检定提供了一种新方法,并为修订平面度国家标准和平板检定规程提供了理论依据。 相似文献
973.
Deli Li 《Revue canadienne de statistique》1996,24(3):279-292
Let {X, Xn; n ≥ 1} be a sequence of real-valued iid random variables, 0 < r < 2 and p > 0. Let D = { A = (ank; 1 ≤ k ≤ n, n ≥ 1); ank, ? R and supn, k |an,k| < ∞}. Set Sn( A ) = ∑nk=1an, kXk for A ? D and n ≥ 1. This paper is devoted to determining conditions whereby E{supn ≥ 1, |Sn( A )|/n1/r}p < ∞ or E{supn ≥ 2 |Sn( A )|/2n log n)1/2}p < ∞ for every A ? D. This generalizes some earlier results, including those of Burkholder (1962), Choi and Sung (1987), Davis (1971), Gut (1979), Klass (1974), Siegmund (1969) and Teicher (1971). 相似文献
974.
Often, in industrial stress testing, meteorological data analysis, and other similar situations, measurements may be made sequentially and only values smaller than all previous ones are recorded. When the number of records is fixed in advance, the data are referred to as inversely sampled record-breaking data. This paper is concerned with nonparametric estimation of the distribution and density functions from such data (successive minima). For a single record-breaking sample, consistent estimation is not possible except in the extreme left tail of the distribution. Hence, replication is required, and for m such independent record-breaking samples, the estimators are shown to be strongly consistent and asymptotically normal as m ∞ →. Computer simulations are used to investigate the effect of the bandwidth on the mean squared errors and biases of the smooth estimators, and are also used to provide a comparison of their performance with the analogous estimators obtained under random sampling for record values. 相似文献
975.
This paper shows that Daniels's (1954) saddlepoint expansion for the density of a sample mean is, for all practical purposes, always uniformly valid on compact subsets in the interior of the domain of the mean. This uniform validity is the key for establishing the relation between the saddlepoint expansion for the density function and Lugannani and Rice's expansion for the tail probability, and for establishing the validity of a high-order asymptotic expansion for the density of a standardized mean. 相似文献
976.
977.
Gilles R. Ducharme 《Revue canadienne de statistique》1995,23(4):421-424
In a regression model with univariate response, the quantities derived from the least-absolute-deviations method need not be unique. In this note, we show that, contrary to the univariate case, in a regression model with multivariate response, the least-distances method typically yields quantities that exhibit uniqueness properties that are similar to those obtained by the least-squares method. 相似文献
978.
Jonas Debrulle 《LABOUR》2016,30(2):180-197
This study investigates patterns of movement from self‐employment to wage employment or to unemployment in Belgium. Non‐parametric techniques and complimentary log–log analyses are used to determine the significance of stable individual traits (e.g. gender) and of time‐dependent characteristics (e.g. family and organizational context, labour market mobility) in moving back to wage employment or to unemployment. Evidence is provided on the possibility of entrepreneurship acting as a ‘steppingstone’ between long‐term unemployment and paid work. Yet, significant relationships also emerge between ex‐ante time spent in unemployment and the possibility of continued unemployment upon self‐employment exit. 相似文献
979.
Graciela Laura Kaminsky Pablo Vega‐García 《Journal of the European Economic Association》2016,14(1):80-114
The theoretical literature on sovereign defaults has focused on adverse shocks to debtors' economies, suggesting that defaults are of an idiosyncratic nature. Still, sovereign debt crises are also of a systemic nature, clustered around panics in the financial center, such as the European Sovereign Debt Crisis in the aftermath of the US Subprime Crisis in 2008. Crises in the financial centers are rare disasters and, thus, their effects on the periphery can only be captured by examining long episodes. In this paper, we examine sovereign defaults from 1820 to the Great Depression, with a focus on Latin America. We find that 63% of the crises are of a systemic nature. These crises are different. Both the international collapse of liquidity and the growth slowdown in the financial centers are at their core. These global shocks trigger longer default spells and larger losses for investors. 相似文献
980.
Sovereign debt restructurings can be implemented preemptively—prior to a payment default. We code a comprehensive new data set and find that preemptive restructurings (i) are frequent (38% of all deals 1978–2010), (ii) have lower haircuts, (iii) are quicker to negotiate, and (iv) see lower output losses. To rationalize these stylized facts, we build a quantitative sovereign debt model that incorporates preemptive and post‐default renegotiations. The model improves the fit with the data and explains the sovereign's optimal choice: preemptive restructurings occur when default risk is high ex ante, while defaults occur after unexpected bad shocks. Empirical evidence supports these predictions. 相似文献