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991.
992.
This paper examines the influence and direction of social and economic determinants of the HIV/AIDS global epidemic across nations and assesses each country’s efficiency in battling the pandemic. The initial dataset consisted of 151 countries with five dependent variables and 90 explanatory variables (reduced to 50 after extensive exploratory data analysis of missing value patterns, undesirable multi-colinearities and multivariate outliers). 相似文献
993.
Ronald DeVore Gerard Kerkyacharian Dominique Picard Vladimir Temlyakov 《Foundations of Computational Mathematics》2006,6(1):3-58
Let ρ be an unknown Borel measure defined on the space Z := X × Y with X ⊂ ℝd and Y = [-M,M]. Given a set z of m samples zi =(xi,yi) drawn according to ρ, the problem of estimating a regression function fρ using these samples is considered. The main focus
is to understand what is the rate of approximation, measured either in
expectation or probability, that can be obtained under a given prior
fρ ∈ Θ, i.e., under the assumption that fρ is in the set
Θ, and what are possible algorithms for obtaining optimal or
semioptimal (up to logarithms) results. The optimal rate of decay in terms
of m is established for many priors given either in terms of smoothness of
fρ or its rate of approximation measured in one of several ways. This optimal rate is determined by two types of results.
Upper bounds are established using various tools in approximation such as entropy, widths, and linear and nonlinear approximation.
Lower bounds are proved using
Kullback-Leibler information together with Fano inequalities and a certain type
of entropy. A distinction is drawn between algorithms which employ knowledge
of the prior in the construction of the estimator and those that do not.
Algorithms of the second type which are universally optimal for a certain range
of priors are given. 相似文献
994.
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997.
Concentration profiles of sputtered and pulsed laser deposited nanoscale Co/Cu multilayers have been measured by EDXS and
EELS line scans in scanning mode at electron microscopic cross section foils and by AES depth profile analysis. The interpretation
of the results has been supported by model calculations. After deposition, the pulsed laser deposited multilayers are stronger
mixed than the sputtered layers. They decompose during annealing. 相似文献
998.
Gabriel Vivó-Truyols Bastiaan Staal Peter J. Schoenmakers 《Journal of chromatography. A》2010,1217(25):4150-4159
A method aimed to obtain the relative abundances of all molecular species in highly overlapped mass spectra is presented. Its performance is demonstrated with an example of matrix-assisted laser desorption ionization (MALDI) spectra obtained from a polysterene-co-polyisoprene sample, retrieving the full co-polymer architecture. The method is based on a multiple regression operation, applied locally at consecutive regions. The method is designed in such a way that it is not necessary to locate regions in the spectrum that are not influenced by adjacent ones. This increases its applicability, since the method is able to tackle the analysis of highly complex spectra, tending to minimise the need of user intervention. The method allows to correct for non-idealities (such as wrong calibration) or to adjust the variations of spectral resolution with mass. Additionally, the algorithm calculates the precision of the computation in a straightforward way. 相似文献
999.
研究基于输入-输出数据的重心法模糊系统及其泛逼近性.首先,将一组单输入-单榆出数据转换成模糊推理规则,通过选择适当的模糊蕴涵算子生成模糊关系,再利用这种模糊关系求出二雄随机变量的联合概率密度函数.当将模糊蕴涵分别取为Larsen蕴涵和Mamdani蕴涵时,分别得到了两种具体的概率密度函数(称之为Larsen分布和Mamdani分布).其次,利用这两种概率分布.分别求出了对应的两种回归函数,指出这种回归函数实际上是模糊控制中的重心法模糊系统.我们分别给出了这种模糊系统具有泛逼近性的充分条件.从而进一步揭示了模糊系统的概率论意义. 相似文献
1000.
Calibration is required to obtain analyte concentrations in atomic spectrometry. To take full benefit of it, the adequacy of the coefficient of determination r2 is discussed, and its use is compared with the uncertainty due to the prediction bands of the regression. Also discussed from a tutorial point of view are the influence of the weighting procedure and of different weighting factors, and the comparison between linear and quadratic regression to cope with curvatures. They are illustrated with examples based on the use of ICP-AES with nebulization and laser ablation, and of LIBS. Use of a calibration graph over several orders of magnitude may be problematic as well as the use of a quadratic regression to cope with possible curvatures. Instrument softwares that allow reprocessing of the calibration by selecting standards around the expected analyte concentration are convenient for optimizing the calibration procedure. 相似文献