空中防撞系统避撞机制的数学模型

在TCAS系统中,到达最接近点的时间Tau、HMD和VMD是描述空中碰撞物理过程的主要参数,利用该组参数能够完整地描述TCAS系统的防撞机制。该文通过对到CPA时间的近似,引入对Tau时间的物理解释;并通过坐标变换,采用本机和入侵飞机的相对距离、相对距离变化率和相对距离加速度推导出了HMD的数学表达式;分析了工程实际应用中的修正模型。     

Connectivity in urbanizing landscapes: The importance of habitat configuration,urban area size,and dispersal

Human activities affect both the amount and configuration of habitat. These changes have important ecological implications that can be measured as changes in landscape connectivity. I investigated how urbanization interacts with the initial amount and aggregation of habitat to change dispersal potential, restoration potential, and the risk of spatially extensive disturbances. I used a factorial set of simulated landscapes and subjected each landscape to habitat loss by overlaying 66 different US urban areas. I used a common connectivity metric, CONNECT, to assess the magnitude and direction of changes for a range of dispersal distances. My results show that the relationship between habitat loss and connectivity loss is non-linear and subject to interactions between the spatial patterns of habitat distribution, urban morphology, and dispersal capabilities. The implications of a given urban form vary widely as a function of habitat distribution and dispersal capabilities. This implies that impact assessments, restoration activities, and conservation planning should consider historical habitat distribution when evaluating observed changes in connectivity. While my results clearly show that more aggregated or continuous habitats are more vulnerable to connectivity loss, this approach can also be used to identify landscapes where restoring connectivity will be particularly effective, for example through placement of stepping stone habitats.     

Robust Methods of Building Regression Models—An Application to thè Housing Sector

This article studies robustification strategies for the linear model in the presence of outliers. The advantages of an internal analysis of the robustness of least squares for a given sample are pointed out. The application of this methodology is illustrated by building an explicit model of the determinants of rental housing values in the Madrid Metropolitan Area.     

我国现代远程教育中存在的问题及对策

随着现代信息技术的发展,我国的现代远程教育也迅速发展起来,并有着广阔的发展前景。文章从实际教学经历出发,讨论了我国现代远程教育的发展现状及存在的问题,并提出了一些建议和措施。     

构建贵州现代远程教育体系实现高等教育的跨越式发展

高等教育超常规的发展需要新的战略和思路,即发展现代远程教育能有效地解决高等教育资源短缺与巨大社会需求的矛盾,为贵州实现高等教育跨越式的发展提供了广阔的空间和可能.     

语篇中指称选择的认知语用解释

叙述语篇中的指称选择主要受到三个因素的影响:指称距离,指称对象是否引起歧义,指称对象与话题焦点的关系。这三个因素归根结底可以从心理学方面得到解释。人类的记忆系统和认知特点决定了人类对指称选择的认知加工方式。     

A characteristic function approach to the biased sampling model,with application to robust logistic regression

Many sampling problems from multiple populations can be considered under the semiparametric framework of the biased, or weighted, sampling model. Included under this framework is logistic regression under case–control sampling. For any model, atypical observations can greatly influence the maximum likelihood estimate of the parameters. Several robust alternatives have been proposed for the special case of logistic regression. However, some current techniques can exhibit poor behavior in many common situations. In this paper a new family of procedures are constructed to estimate the parameters in the semiparametric biased sampling model. The procedures incorporate a minimum distance approach, but are instead based on characteristic functions. The estimators can also be represented as the minimizers of quadratic forms in simple residuals, thus yielding straightforward computation. For the case of logistic regression, the resulting estimators are shown to be competitive with the existing robust approaches in terms of both robustness and efficiency, while maintaining affine equivariance. The approach is developed under the case–control sampling scheme, yet is shown to be applicable under prospective sampling logistic regression as well.     

文化差异、地理距离对我国各省分国别(地区）出口贸易的影响——基于空间面板数据的实证研究

利用2001-2009年中国30个省分分国别（地区）的出口贸易数据,采用空间探索性数据分析方法分析了各国及地区在我国的出口贸易空间格局,发现各国（地区）在我国的出口贸易中表现出较为显著的空间相关性。进一步,本文构建了考虑空间滞后因子的引力模型实证分析了文化差异和运输距离对我国各省分国别（地区）出口贸易的影响。研究结果表明：我国邻省出口对本省的空间溢出效应随着时间的推移不断增强;而邻省与本省在出口伙伴国选择上的“竞争效应”并不明显;文化差异在各国及地区在我国各省的出口贸易中所起的限制性作用表现突出;而陆运距离对各省分国别（地区）出口贸易的负向影响要明显大于海运距离,且随着时间的推移有不断扩大的迹象。     

心理期望：政治认同生成的内隐机制

政治认同是公民对国家政治诸要素所产生的一种心理上的归属感。心理期望作为政治认同的内隐机制,从需要因素看,可分为自发性政治认同需要和引致性政治认同需要。而对需要的满足,则取决于主体的自我政治期望和社会政治期望的契合程度及运行路向。现实问题往往因对期望的认知错位而产生各异的政治认同距离进而给个体和政府等带来心理压力。如何把这种压力保持在一定的安全阈值范围内而使政府和个人在期望心理供求方面处于大体均衡,成为优化政治认同效果的现实选择。