关于曲线积分和曲面积分教学中几个难点的突破

加强曲线、曲面积分概念讲解,标准化曲线、曲面积分的计算程序,沟通有关积分之间关系,以消除学生 对斯托克斯等公式的深奥感,有效地突破了曲线、曲面积分教学中的几个难点。     

安徽省耕地保护前景分析

随着社会经济的发展，安徽省耕地供需矛盾日益突出，科学地分析安徽省耕地保护前景，探寻合理的耕地保护对策．具有重要的现实意义。本文立足于安徽省耕地资源现状，从粮食生产、非农建设占地两方面探讨安徽经济发展对耕地的需求前景，并采用灰色系统模型对耕地的供给变化进行预测，通过耕地供需形势的分析，针对性地提出保护耕地的相应对策。     

DEFAULT RISK INSURANCE AND INCOMPLETE MARKETS1

This paper uses the existence of secondary markets for debt instruments with default risk (e.g. corporate bonds) to define default insurance along the lines of financial economics. It examines whether, in the case of several risk-neutral measures, characteristics of default can be uniquely determined by the prices of contracts involving default-prone securities.     

关于商品价值、生产价格及其售卖价格公式量化的探讨

传统的商品价值公式C V m,只能理解为商品在生产领域所形成的价值,而不能理解为是商品价格因供求变化围绕其价值中枢上下波动的那个商品价值.真正的商品价值,应既包括商品的生产价值,又包括商品的流通价值.因为,在流通领域中的保管、运输劳动也是创造价值的劳动;同时,纯粹商业劳动亦是创造价值的劳动.依据这一思路,生产价格应改为"生产--流通价格"或"商品平均价格".     

Future of Economic Growth for South Korea*

More than 80 percent of US growth between 1950 and 1993 can be attributed to transition dynamics (increases in R&D intensity and educational attainment), with less than 20 percent of growth deriving from population growth. Similarly, growth accounting shows that 80 percent of economic growth in Korea can be attributed to transition dynamics. However, the specific factors that have moved Korea far from its steady state are significantly different from the factors that have done so for the USA. In addition to the growth rates of the two countries, we also analyzed the (steady‐state) level of output per worker to determine where the Korean economy is headed relative to the USA. In 1960, Korea was characterized as poor (0.111) relative to its own steady state (0.765), and incomes were at 11.1 percent of those in the USA. Since then, however, Korea has been growing more rapidly than the USA. In our analysis, we also consider the extreme case where total factor productivity levels converge completely. Interestingly, in this case, the USA and Korea exhibit unconditional convergence similar to what is generally observed in the OECD. As the economy approaches the steady‐state income level, however, the growth rate of output per capita will decline.     

Computing the covariance of two Brownian area integrals

We compute the expected product of two correlated Brownian area integrals, a problem that arises in the analysis of a popular sorting algorithm. Along the way we find three different formulas for the expectation of the product of the absolute values of two standard normal random variables with correlation θ . These two formulas are found: (a) via conditioning and the non-central chi-square distribution; (b) via Mehler's formula; (c) by representing the correlated normal random variables in terms of independent normal's and integration using polar coordinates.     

Covariance formulas via marginal martingw

Prenctice and Cai recently introduced and studied the function C defined as the covariance function of the two marginal counting process martingales of a pair of dependent survival times (T₁, T₂ ). They show that the function C together with the marginal distributions determines the joint survival function F of (T₁, T₂ ). In this note we show how the key characterizing equation of Prentice and Cai yields a formula for the covariance of T₁ and T₂ in termsof the marginal mean residual life functions and C. The resulting formula generalizes a formula for the variance of a one-dimensional random variable Tdueto Pyke (1965). We also explore several generalizations of the covariance formula, and obtain a valid k-dimensional version of the Prentice and Cai formula.     

Bridging the gap between a stationary point process and its Palm distribution

In the context of stationary point processes measurements are usually made from a time point chosen at random or from an occurrence chosen at random. That is, either the stationary distribution P or its Palm distribution P° is the ruling probability measure. In this paper an approach is presented to bridge the gap between these distributions. We consider probability measures which give exactly the same events zero probability as P°, having simple relations with P . Relations between P and P° are derived with these intermediate measures as bridges. With the resulting Radon-Nikodym densities several well-known results can be proved easily. New results are derived. As a corollary of cross ergodic theorems a conditional version of the well-known inversion formula is proved. Several approximations of P° are considered, for instance the local characterization of P^o as a limit of conditional probability measures P° N The total variation distance between P° and P₁ can be expressed in terms of the P-distribution function of the forward recurrence time.     

Organizational coordination, development proficiency, and on-time completion of development and international rollout: A contingency analysis of external environments

This study examines the moderating effects of external environmental variables on the relationships between organizational coordination, quality of implementation of new product development (NPD) activities, and on-time completion of (or timeliness in) product development and international new product rollout (INPR) among manufacturing firms in Korea. The results indicate that quality of marketing execution is of greater importance for achieving on-time NPD and multi-country rollout in markets where competitive intensity is high than when it is low. The positive effect of HQ-subsidiary relationships on INPR timeliness is strengthened in rapid rather than slower technology-change environments. By contrast, the positive effect of HQ-subsidiary relationships on INPR timeliness is weakened in high rather than lower competitive-intensity environments. In addition, the beneficial effect of cross-functional integration on NPD timeliness is weakened in markets characterized by a high rate of technological change. The article also discusses the theoretical and managerial implications of the findings.     

北京市能源消费的因素分解分析

本文利用迪氏对数指标分解法(LMDI)对北京市17个行业2005～2009年间的能源消费变动进行因素分解分析.将能源消费增长的总效应分解为3个部分:生产效应、结构效应和强度效应.生产效应是经济增长对能源消费增长的贡献,结构效应反映产业结构调整对能源消费增长的贡献,强度效应是指能源效率提高时能源消费增长的贡献.实证研究结果表明,生产效应是导致北京市能源消费增长的主要因素,结构效应和强度效应则延缓了能源消费总量的增长,但生产效应明显大于结构效应和强度效应之和,因此能源消费在此期间表现为增加.值得注意的是强度效应高于结构效应.