Occupancy numbers for dynamic heterogeneous populations: Estimate of particles lifetimes

A dynamic model of a heterogeneous population is studied. Particles belonging to a population are divided, at every time t, into a finite number of classes according to their types and the partition changes over time. The role of the occupancy numbers, namely the cardinality of each class, is highlighted. The relationship between the stochastic process of occupancy numbers and the process of particle types is analyzed. The main goal of this paper is the estimation of the lifetime of each particle at a given time t, when the observed data are the history of the process of the number of dead particles up to t. Furthermore, a discrete time approximation of the filter is given.     

Comparing relative importance of the same component in a series system in two environments

The relative performance of a component of a series system in two different environments is considered. The conditional probability of the failure of the system due to the failure of the specified component given that the system failed before time t is regarded as a measure of relative importance of the component to the system. A U-statistic test for checking the equality of the relative importance of the component to the system in two different environments against the alternative that the relative importance is smaller in one of the environments, is proposed. Some simulation results for estimating the power of the test are reported. The proposed test is applied to one real data set and it is seen that a different aspect of the data is brought out by this comparison than that by the comparisons of the absolute importance functions such as the subsurvival functions, considered in earlier studies.     

RNA电泳结果和Northern blot效果的关系探讨

对RNA电泳结果和Northernblot效果的关系进行了探讨，结果表明利用RNA电泳结果可判断最终Northernblot的质量。     

Gamesmanship for internal evaluators: Knowing when to “hold 'em” and when to “fold 'em”

This article discusses the ethical conflicts between an internal evaluator's altruistic social reform motivation and an organization's practical survival motivation. The internal evaluator might encounter (a) pressure to downplay negative and emphasize positive findings; (b) reinforcement for nonthreatening, routine evaluation activities; (c) greater interest in making the evaluation unit visible than in using evaluation results; or (d) reduced access to privileged information.     

俄英语中倍数增减的译法

在英语和俄语科技语体中 ,“增加 N倍和减少几分之几”经常出现 ,汉语译法根据不同语境而有所变化。本文通过分析其不同的表达方式 ,提供了一些常用的翻译方法     

Ethnic differences in the academic achievement process in Canada

This research examines the extent to which differences in achievement between German-speaking and French-speaking students are accounted for by theoretically related intervening variables and the extent to which the entire achievement process differs across the two ethnic groups. For the two ethnic groups, both main effects and interaction effects have significant consequences for the academic achievement process, even when a number of other variables are controlled. The results suggest that the whole process works to the benefit of the German-speaking students and to the detriment of the French-speaking students.     

International cooperation in stockpiles and tariffs for coping with oil supply disruptions

This paper provides a unified treatment of oil stockpiling and demand restraint as policy responses for enhancing energy security and examines the implications of recent changes in the structure and performance of the international oil market for the design of policies. These issues are addressed using a dynamic programming framework in which international policy actions of key oil-importing countries are modeled as a Nash dynamic game. Significant policy implications from the analysis include: (1) the result that, with realistic assumptions about disruption risks and inventory capacities, differences between noncooperative and coordinated stockpile policies appear to be minor and (2) significant mutual gains could be reaped from a modest degree of collective restraint on normal market oil demand. The broader role of international cooperation in enhancing energy security is also discussed.     

The determinants of international creditworthiness and their policy implications

The present paper utilizes an empirical measure of creditworthiness based on bankers' perceptions to estimate the effect of various variables hypothesized to influence assessments of countries' debt-servicing capacity. The data pertain to a cross section of countries within the period 1979–1983. Such estimates necessarily employ a ceteris paribus assumption, which prevents a realistic assessment of the effects generated by policy changes. The second part of the paper develops, therefore, a dynamic simulation model of a hypothetical average economy. The simulations allow analysis of changes in macroeconomic variables and creditworthiness over time within a system that maintains accounting identities and behavioral constraints. Several changes in policy variables are considered that highlight the importance of export expansion. The latter is, of course, an often suggested policy objective, but the present paper demonstrates its effectiveness in terms of a somewhat nonstandard criterion.     

Commodity prices and the world distribution of income

Some advocates of a new international economic order recommend raising prices of commodities exported by developing countries as a means of reducing the inequality of world income distribution. A simulation model using commodity trade data and income distribution data for 68 industrial and developing countries examines this policy alternative. Initial data compilation reveals that internal inequality is as important as international: The world income share of the poorest 40% of people would be twice as high in the absence of intracountry inequality. Calculations using actual price experience in the “great inflation” of 1972–1975 show that despite the large relative price changes for some commodities (especially oil), these changes left the world size distribution of income virtually unchanged. Separate policy simulations show that even a quadrupling of the price of ali “equalizing” commodities (those mainly exported by LDCs) would leave the size distribution of world income practically unaltered (even under optimistic assumptions about intracountry distributional incidence), although some individual LDCs would gain. Increasing commodity prices therefore appears to be an ineffective means of increasing international equity, quite apart from questions about the feasibility of cartels or commodity agreements.