计算机辅助机械设计中的成本分析

本文提出了通过机械设备生存期评估其成本的概念，描述了在机械设计过程中用计算机进行经济辅助分析，用参数化的方法进行面向机械设计的成本评估，同时讨论了基于零件特征的成本分析。     

Patterns of plant invasions at small spatial scale correspond with that at the whole country scale

Urban Ecosystems - Invasions were studied at different spatial scales, however these scales were rarely compared. The aim of this study is to compare the rate of expansion of eight alien plant...     

Higher order moments of the estimated tangency portfolio weights

In this paper, we consider the estimated weights of the tangency portfolio. We derive analytical expressions for the higher order non-central and central moments of these weights when the returns are assumed to be independently and multivariate normally distributed. Moreover, the expressions for mean, variance, skewness and kurtosis of the estimated weights are obtained in closed forms. Later, we complement our results with a simulation study where data from the multivariate normal and t-distributions are simulated, and the first four moments of estimated weights are computed by using the Monte Carlo experiment. It is noteworthy to mention that the distributional assumption of returns is found to be important, especially for the first two moments. Finally, through an empirical illustration utilizing returns of four financial indices listed in NASDAQ stock exchange, we observe the presence of time dynamics in higher moments.     

Birth control and regional differentials in the Soviet Union

Abstract Following the territorial division pointed out by Urlanis into those parts of the Soviet Union where birth control is practised and where it is not as widespread, it is possible to ascertain the importance of different factors bearing on fertility within each region. This study was based on data obtained from the 1959 USSR Census of Population including information on social and demographic characteristics of the urban and rural populations for over 150 political-administrative areas. In Central Asia, Azerbaidjan and Armenia, outside the region of birth control, the level of fertility depends mainly on the proportion of women who are married and also on their social position measured by the discrepancy in the educational status of men and women. In contrast, the birth control region of a relatively low level of fertility in urban areas, for example, displays the characteristic of women's educational achievement most strongly associated with the child-woman ratio. Except for the rural areas in this region, the present study fails to support the popular hypothesis that economic dependency of women is directly related to fertility.     

Effects of Social Influence and Measured Exposure Level on Response to Radon*

The eclectic theoretical model presented indicates that responses to hazards are affected by friends, the mass media, and by the measured level of exposure to the hazard. This model guides the analysis of survey data garnered from a New York State county whose residents were offered free tests to determine the level of radon in their homes. Results indicate that measured radon level is consistently correlated with specific responses to a direct threat of radon on one's home, whereas the influence of family or the mass media have little effect. The situation is reversed when radon is regarded as a diffuse hazard without specific reference to the respondent's own home.     

RNA multiple structural alignment with longest common subsequences

In this paper, we present a new model for RNA multiple sequence structural alignment based on the longest common subsequence. We consider both the off-line and on-line cases. For the off-line case, i.e., when the longest common subsequence is given as a linear graph with n vertices, we first present a polynomial O(n ²) time algorithm to compute its maximum nested loop. We then consider a slightly different problem—the Maximum Loop Chain problem and present an algorithm which runs in O(n ⁵) time. For the on-line case, i.e., given m RNA sequences of lengths n, compute the longest common subsequence of them such that this subsequence either induces a maximum nested loop or the maximum number of matches, we present efficient algorithms using dynamic programming when m is small. This research is partially supported by EPSCOR Visiting Scholar's Program and MSU Short-term Professional Development Program.     

Electoral competition in 2-dimensional ideology space with unidimensional commitment

We study a model of electoral competition between two candidates with two orthogonal issues, where candidates are office motivated and committed to a particular position in one of the dimensions, while having the freedom to select (credibly) any position on the other dimension. We analyse two settings: one where both candidates are committed to the same dimension, and the other where each candidate is committed to a different dimension. We focus on characterisation and existence of pure strategy Nash equilibria when the core is empty. We show that if the distribution of voters’ ideal policies is continuously differentiable and has a bounded support, then an equilibrium exists if the candidates are differentiated enough. Our results for the case where the candidates have a common committed issue have implications for the literature on valence.