A moment-generating function with application to the birnbaum-saunders distribution

The Birnbaum-Saunders distribution is a fatigue life distribution that was derived from a model assuming that failure is due to the development and growth of a dominant crack. This distribution has been shown to be applicable not only for fatigue analysis but also in other areas of engineering science. Because of its increasing use, it would be desirable to obtain expressions for the expected value of different powers of this distribution.

In this article, the moment-generating function for the sinh-normal distribution is derived. It is shown that this moment-generating function can be used to obtain both integer and fractional moments for the Birnbaum-Saunders distribution. Thus it is now possible to obtain an expression for the expected value of the square root of a Birnbaum-Saunders random variable. A general expression for integer noncentral moments for the Birnbaum-Saunders distribution is derived using the moment-generating function of the sinh-normal distribution. Also included is an approximation of the moment-generating function that can be used fcx small values of the shape parameter.     

Unconditional analogues of Cochran–Mantel–Haenszel tests

The Cochran–Mantel–Haenszel tests are a suite of tests that are usually defined as conditional tests, tests that assume all marginal totals are known before sighting the data. Here unconditional analogues of these tests are defined for the more usual situation when the marginal totals are not known before sighting the data.     

A time series model with random coefficients

There are many time series applications where an experi­menter observes the simultaneous responses of several sub­systems over time. In these instances one is often not interested in the parameters of individual subsystems, but rather in an overall characterization of the system in question. Under the assumption that subsystems are independent and first order autoregressive, the present paper presents two methods for estimating the distribution of the subsystem coefficients.     

开缝平板－圆柱传输线解的进一步研究

运用保角变换分析了位于开缝无限大平板上方的圆柱形传输线，给出了这种公输线特性阻抗闭合形式的近似和严格解，这些分析是建立在假设线中只有准ＴＥＭ模传播的基础之上的。     

WORKING TO EXIT POVERTY WHILE CARING FOR CHILDREN'S HEALTH AND DEVELOPMENT IN VIETNAM

Since the implementation of economic reforms in 1986, levels of urbanization, industrialization, and women's labour force participation have increased in Vietnam. This article focuses on the experiences of parents in Vietnam and how labour and social conditions affect their ability to work and exit poverty while caring for their children's health and development. We interviewed a sample of 147 parents in Ho Chi Minh City using in-depth, semi-structured questionnaires. Sixty-three percent of parents had faced loss of income or promotions or had difficulty retaining jobs because they had to care for children. Fifty-eight percent of parents lost income while caring for their sick children because they had to take unpaid leave from work to care for their children or because they had to decrease productivity if they were able to continue working. Fifty percent of parents with school-age children experienced barriers to helping with homework, to attending meetings, or to participating in other aspects of their children's education. The aftermath of the Vietnamese – American War affected parents through loss of extended family members, limiting access to a major traditional source of support. The war had affected other parents by preventing them from completing their education, which left them with job choices that offer little or no work benefits. Although Vietnam has made significant progress in providing early childhood care and education and legislating labour laws, working families’ experiences demonstrate the need to ensure that paid leave and work flexibility policies are available and implemented in all work sectors and to expand affordable, quality child care in order to help low-income working parents in Vietnam meet work demands and exit poverty while meeting their children's needs.     

国际贸易网络与股价崩盘传染:竞争性货币贬值视角

目的/意义当市场面临重大冲击时,虽然不同行业指数在上涨与下挫过程中存在着类似趋势,但依然有着不同的波动特征与溢出特征。设计/方法利用GARCHSK模型刻画我国股票市场各行业不同阶矩的波动特征,并通过溢出指数从静态和动态角度测度2004～2018年期间我国股票市场行业间一阶矩、二阶矩和高阶矩风险溢出的强度和方向。结论/发现研究表明我国股市各行业指数具有明显的高阶矩波动特征,且各阶矩风险联动效应较强,单个行业的风险容易通过行业间的相互作用扩散到整个市场;当危机发生时,相比收益溢出指数较小的变化幅度,波动溢出指数能够及时对市场冲击做出反应,且高阶矩波动溢出指数能更准确地体现出不同行业的特质以及所受冲击的大小。     

Ultrastructural elliptical models

Dolby's (1976) ultrastructural model with no replications is investigated within the class of the elliptical distributions. General asymptotic results are given for the sample covariance matrix S in the presence of incidental parameters. These results are used to study the asymptotic behaviour of some estimators of the slope parameter, unifying and extending existing results in the literature. In particular, under some regularity conditions they are shown to be consistent and asymptotically normal. For the special case of the structural model, some asymptotic relative efficiencies are also reported which show that generalized least squares and the method of moment estimators can be highly inefficient under nonnormality.     

On random variate generation for the generalized hyperbolic secant distributions

We give random variate generators for the generalized hyperbolic secant distribution and related families such as Morris's skewed generalized hyperbolic secant family and a family introduced by Laha and Lukacs. The rejection method generators are uniformly fast over the parameter space and are based upon a complex function representation of the distributions due to Harkness and HarknessThe author's research was sponsored by NSERC Grant A3456 and FCAR Grant 90-ER-0291.     

用求荷载控制段的方法确定临界荷载

提出在移动荷载组作用下求简支梁内某一指定截面的最大弯矩的一种解法，这种解法的关键是求出梁上各个荷载的控制段．