从玉米芯中提取木糖的试验研究

本文提出了通过玉米芯稀酸常压水解制取木糖的工艺和方法,讨论了影响木糖提取率的因素。     

Hardiness and the relationship between stressors and outcomes

Using a sample of 468 participants, from two organizations, this study examined direct and moderating relationships between hardiness (a composite of challenge, control, and commitment), life and work stressors, and a variety of health-related outcomes. The results indicated that hardiness did not moderate the relationship between stressors and outcomes as reported by others (e.g. Kobasa 1982a). However, hardiness did have significant direct effects on emotional and psychological factors thought to be related to personal well-being and work performance. Hardy individuals reported higher levels of job satisfaction and fewer tensions at work dun did the less hardy. In general, hardy individuals experienced a higher quality of life and a more positive affect while being more energized and less negative about life. Hardy individuals also reported fewer somatic complaints and tended to be less depressed and anxious than individuals low in hardiness. In addition, hardiness was negatively related to all four measures of life and work stress implying that hardiness may not be independent of life demands.     

M-Estimates of regression when the scale is unknown and the error distribution is possibly asymmetric: A minimax result

Huber (1964) found the minimax-variance M-estimate of location under the assumption that the scale parameter is known; Li and Zamar (1991) extended this result to the case when the scale is unknown. We consider the robust estimation of the regression coefficients (β₁,…,β_p) when the scale and the intercept parameters are unknown. The minimax-variance estimates of (β₁,…,β_p) with respect to the trace of their asymptotic covariance matrix are derived. The maximum is taken over ?-contamination neighbourhoods of a central regression model with Gaussian errors (asymmetric contamination is allowed), and the minimum is taken over a large class of generalized M-estimates of regression of the Mallow type. The optimal choice of estimates for the nuisance parameters (scale and intercept) is also considered.     

The ‘Extended’ Atkinson family: The class of multiplicatively decomposable inequality measures,and some new graphical procedures for analysts

This paper introduces and characterises a class of inequality measures which extends the Atkinson family. This class contains canonical forms of all aggregative inequality measures, each bounded above by one, provides a new dominance criterion for ordering distributions in terms of inequality and offers some new graphical procedures for analysts. The crucial axiom for the characterisation is an alternative to the standard additive decomposition property that we call ‘multiplicative decomposability,’ where the within-group component is a generalised weighted mean with weights summing exactly to one. An erratum to this article can be found at     

中美棉花期货价格引导和均衡关系的实证分析

对中国棉花期货上市至实证结束期间796个价格数据,运用Eviews软件的协整分析、Granger因果检验、误差修正模型和方差分解法,实证检验了中国和美国棉花期货价格之间的关系,结果表明:中美棉花期货价格之间的协整关系成立,两者具有显著的长期稳定关系;中美棉花期货价格间存在显著的相互引导关系;短期内美国棉花期货价格变动是中国棉花期货价格变动Granger意义上的原因;中国期货价格虽受到美国棉花期货价格的影响,但具有较强的独立性。     

股票收益的自校正研究

提出一种联系股票价格、股票收益及股息的单变量回归模型来研究股票收益的自校正，并采用变量分解法探讨股票预期收益与非预期收益两者之间的变动关系。     

Note on the Cramér-Rao inequality in the nonregular case: the family of uniform distributions

We consider the family of uniform distributions with range of unit length. The main result of this note asserts that the average variance of any unbiased estimator of the midpoint of the range is not less than (2(n+1))(n+2))^-1 and this lower bound is sharp. The proof is based upon a nonregular version of the Cramér-Rao inequality.     

The interpretation of maximum-likelihood estimation

Maximum-likelihood estimation is interpreted as a procedure for generating approximate pivotal quantities, that is, functions u(X;θ) of the data X and parameter θ that have distributions not involving θ. Further, these pivotals should be efficient in the sense of reproducing approximately the likelihood function of θ based on X, and they should be approximately linear in θ. To this end the effect of replacing θ by a parameter ϕ = ϕ(θ) is examined. The relationship of maximum-likelihood estimation interpreted in this way to conditional inference is discussed. Examples illustrating this use of maximum-likelihood estimation on small samples are given.     

Estimation of the MSE matrix of the stein estimator

Uniformly minimum-variance unbiased (UMVU) estimators of the total risk and the mean-squared-error (MSE) matrix of the Stein estimator for the multivariate normal mean with unknown covariance matrix are proposed. The estimated MSE matrix is helpful in identifying the components which contribute most to the total risk. It also contains information about the performance of the shrinkage estimator with respect to other quadratic loss functions.     

On the distribution of quadratic forms in normal random variables

This paper provides necessary and sufficient conditions for a quadratic form in singular normal random variables to be distributed as a given linear combination of independent noncentral chi-square variables. Using this result, an extension of Cochran's theorem to quadratic forms of noncentral chi-square variables is derived.