航空联盟对国际枢纽机场间机票价格的影响——以我国主要非经停国际航线为例的实证研究

本文通过构建多元回归模型,实证分析了航空联盟对我国主要非经停国际航线客运价格的影响。结果发现,在控制其他一些影响因素之后,航空联盟的存在并不一定会引起航线票价的上升。本文最后依据实证结果,给出相关对策建议。     

高密度电法在龙岩适中矿区锰矿探测中的应用

文章简要介绍了高密度电阻率法的基本原理,并详细分析了一个锰矿探测实例,通过理论与实践的结合,指出高密度电阻率法是一种有效的金属矿探测手段。     

组织密度对针织物悬垂性的影响

为了给针织面料的设计提供一定指导,利用手摇横机编织满针罗纹、罗纹空气层、畦编组织3种针织物,然后用YG（L）811-DN型织物动态悬垂风格测定仪来测定所编织针织物的悬垂性,通过实验数据来分析针织物组织密度对织物悬垂性的影响.结果表明,同一密度下,满针罗纹组织悬垂性最好,且3种织物密度越小,悬垂性也越好.     

Criminal incident prediction using a point-pattern-based density model

Law enforcement agencies need crime forecasts to support their tactical operations; namely, predicted crime locations for next week based on data from the previous week. Current practice simply assumes that spatial clusters of crimes or “hot spots” observed in the previous week will persist to the next week. This paper introduces a multivariate prediction model for hot spots that relates the features in an area to the predicted occurrence of crimes through the preference structure of criminals. We use a point-pattern-based transition density model for space–time event prediction that relies on criminal preference discovery as observed in the features chosen for past crimes. The resultant model outperforms the current practices, as demonstrated statistically by an application to breaking and entering incidents in Richmond, VA.     

Do Tighter Restrictions on Density Retard Development?

Williams (1991) builds a real-options model to investigate the timing and the scale decisions of property development. Williams asserts that tighter restrictions on density retard development. This article finds that there are some typos in Williams’s article such that his assertion does not hold in general. In particular, his assertion will not hold as long as the density restrictions are not set too low relative to the density level that would be chosen by landowners in the absence of any regulation.     

On the Out-of-Sample Importance of Skewness and Asymmetric Dependence for Asset Allocation

Recent studies in the empirical finance literature have reportedevidence of two types of asymmetries in the joint distributionof stock returns. The first is skewness in the distributionof individual stock returns. The second is an asymmetry in thedependence between stocks: stock returns appear to be more highlycorrelated during market downturns than during market upturns.In this article we examine the economic and statistical significanceof these asymmetries for asset allocation decisions in an out-of-samplesetting. We consider the problem of a constant relative riskaversion (CRRA) investor allocating wealth between the risk-freeasset, a small-cap portfolio, and a large-cap portfolio. Weuse models that can capture time-varying moments up to the fourthorder, and we use copula theory to construct models of the time-varyingdependence structure that allow for different dependence duringbear markets than bull markets. The importance of these twoasymmetries for asset allocation is assessed by comparing theperformance of a portfolio based on a normal distribution modelwith a portfolio based on a more flexible distribution model.For investors with no short-sales constraints, we find thatknowledge of higher moments and asymmetric dependence leadsto gains that are economically significant and statisticallysignificant in some cases. For short sales-constrained investorsthe gains are limited.     

Books Reviewed

Vosti, Stephen A., and Thomas Reardon, eds. Sustainability, Growth, and Poverty Alleviation: A Policy and Agroecological Perspective.
Swinbank, Alan, and Carolyn Tanner. Farm Policy and Trade Conflict: The Uruguay Round and CAP Reform.
Frisvold, George, and Betsey Kuhn, eds. Global Environmental Change and Agriculture: Assessing the Impacts.     

Characterizations of normal distributions and EDF goodness-of-fit tests

Two characterizations of a normal distribution with an unknown variance based on the corresponding UMVU estimators of the density functions are given, depending on whether its mean is known, or unknown. Applications of these characterization results in the procedures to construct empirical distribution function (EDF) goodness-of-fit tests for normal distributions are mentioned. Received April 2000/Revised April 2002     

Nonparametric density estimates consistent of the order of <Emphasis Type="Italic">n</Emphasis><Superscript>−1/2</Superscript> in the <Emphasis Type="Italic">L</Emphasis><Subscript>1</Subscript>–norm

We introduce an approximate minimum Kolmogorov distance density estimate of a probability density f₀ on the real line and study its rate of consistency for n. We define a degree of variations of a nonparametric family of densities containing the unknown f₀. If this degree is finite then the approximate minimum Kolmogorov distance estimate is consistent of the order of n^–1/2 in the L₁-norm and also in the expected L₁-norm. Comparisons with two other criteria leading to the same order of consistency are given.Received June 2002     

外来颗粒尺寸、级配和浓度影响的动态模拟实验研究

采用岩心流动试验，研究了微粒运移堵塞的几个重要规律；介绍了关于微粒在多孔介质中运移堵塞规律方面的实验研究：采用室内模拟流体流动试验，研究了颗粒粒径、浓度对低渗透性砂岩（9～11md和19～21md）堵塞规律。