Likelihood ratio tests for symmetry against one-sided alternatives

A random variableX is said to have a symmetric distribution (about 0) if and only ifX and –X are, identically distributed. By considering various types of partial orderings between the distributions ofX and –X, one obtains various notions of skewness or one-sided bias. In this paper we study likelihood ratio tests for testing the symmetry of a discrete distribution about zero against the alternatives, (i)X is stochastically greater than –X; and (ii) pr(X=j)pr(X=–j) for allj>0. In the process, we obtain maximum likelihood estimators of the distribution function under the above alternatives. The asymptotic null distributions of the test statistics have been obtained and are of the chi-bar square type. A simulation study was performed to compare the powers of these tests with other tests.     

Improved Tougaard background calculation by introduction of fittable parameters for the inelastic electron scattering cross‐section in the peak fit of photoelectron spectra with UNIFIT 2011

The shape of the background in x‐ray photoemission spectra is strongly affected by scattered electrons from inelastic energy loss processes. A polynomial of low order has very often been applied to model the secondary‐electron background, giving satisfying results in some cases. An improved analysis employing the Tougaard background model has been successfully used to characterize the inelastic loss processes. However, the correct usage of the Tougaard background needs a well defined inelastic electron scattering cross‐section function λ(E) · K(E, T) (λ = inelastic mean free path, E = kinetic energy, T = energy loss). This paper presents a four‐parameter loss function λ(E) · K(E, T) = B · T/(C + C′ · T²)² + D · T² with the fitting parameters B, C, C′ and D implemented in the background function allowing the improved estimation of the λ(E) · K(E, T) function for homogenous materials. The fit of the background parameters is carried out parallel to the peak fit. The results will be compared with the parameters recommended by Tougaard. The calculation of inelastic electron scattering cross‐sections of clean surfaces from different materials using UNIFIT 2011 will be demonstrated. Copyright © 2011 John Wiley & Sons, Ltd.     

Flexible statistical modelling detects clinical functional magnetic resonance imaging activation in partially compliant subjects

Clinical functional magnetic resonance imaging (fMRI) occasionally fails to detect significant activation, often due to variability in task performance. The present study seeks to test whether a more flexible statistical analysis can better detect activation, by accounting for variance associated with variable compliance to the task over time. Experimental results and simulated data both confirm that even at 80% compliance to the task, such a flexible model outperforms standard statistical analysis when assessed using the extent of activation (experimental data), goodness of fit (experimental data), and area under the operator characteristic curve (simulated data). Furthermore, retrospective examination of 14 clinical fMRI examinations reveals that in patients where the standard statistical approach yields activation, there is a measurable gain in model performance in adopting the flexible statistical model, with little or no penalty in lost sensitivity. This indicates that a flexible model should be considered, particularly for clinical patients who may have difficulty complying fully with the study task.     

轿车钢板表面形貌特征参数的提取

通过对典型轿车钢板表面形貌的分析,以形貌与其摩擦学性能的关系为出发点,对粗糙表面、粗糙峰和粗糙谷的分布特性进行了统计分析。结果表明：粗糙表面、粗糙峰和粗糙谷数的统计分布特性与润滑及接触等性能密切相关;针对轿车钢板表面、粗糙峰和粗糙谷数在高度方向概率分布曲线的非Gauss特性,提出采用Weibull概率密度函数的非线性曲线拟合对分布特征进行分析处理。所得拟合参数具有非常明确的物理意义,所此可以采用少量参数来较全面地描述其对应的轿车钢板表面形貌特征分布。     

中性张量介子f2(1270),f′2(1525)和胶球候选者ξ(2230)的混合

假定ξ(2230)的自旋宇称为2++,研究了中性张量介子f2(1270), f′ 2(1525)和胶球候选者ξ(2230)的混合,通过对可得到的这3个态的衰变数据的拟合,得到了这3个态的夸克和胶球内容. 并给出了一些关于ξ(2230)衰变的预言.     

Pt100温度计电阻和温度关系的拟合

全超导托卡马克(Tokam ak)装置EAST是国家"九五"大科学工程,温度参数是超导磁体最重要也是最基本的运行参数之一。工作在液氮温区的装置部件的温度通过铂电阻温度计Pt100进行监测。根据温度计的一组实测R-T数据进行拟合,得到与实际温度逼近度高的R-T关系函数,从而提高了EAST装置液氮温区温度测量的准确度。     

Jacobi polynomials and non-singlet structure function F2(x,Q2)up to N3LO

In this paper we present the non-singlet QCD analysis to determine valence quark distribution up to four loop.We obtain the fractional difference between the 4-loop and the 1-,2-and 3-loop presentations of xuv(x,Q2)and xdv(x,Q2).