LEARNING STRUCTURED BAYESIAN NETWORKS: COMBINING ABSTRACTION HIERARCHIES AND TREE-STRUCTURED CONDITIONAL PROBABILITY TABLES

Context-specific independence representations, such as tree-structured conditional probability distributions, capture local independence relationships among the random variables in a Bayesian network (BN). Local independence relationships among the random variables can also be captured by using attribute-value hierarchies to find an appropriate abstraction level for the values used to describe the conditional probability distributions. Capturing this local structure is important because it reduces the number of parameters required to represent the distribution. This can lead to more robust parameter estimation and structure selection, more efficient inference algorithms, and more interpretable models. In this paper, we introduce Tree-Abstraction-Based Search (TABS), an approach for learning a data distribution by inducing the graph structure and parameters of a BN from training data. TABS combines tree structure and attribute-value hierarchies to compactly represent conditional probability tables. To construct the attribute-value hierarchies, we investigate two data-driven techniques: a global clustering method, which uses all of the training data to build the attribute-value hierarchies, and can be performed as a preprocessing step; and a local clustering method, which uses only the local network structure to learn attribute-value hierarchies. We present empirical results for three real-world domains, finding that (1) combining tree structure and attribute-value hierarchies improves the accuracy of generalization, while providing a significant reduction in the number of parameters in the learned networks, and (2) data-derived hierarchies perform as well or better than expert-provided hierarchies.     

在海域红外杂波背景中小目标探测的空间匹配滤波技术

利用空间匹配滤波技术，针对海域复杂的红外杂波背景进行了小目标探测。由计算机模拟获得了滤波器设计参数，结果表明滤波后信杂比增益有显著提高，虚警率随之下降，滤波算法硬件易于实现，证明这是一种抑制红外背景杂波的有效技术。     

山西断陷带地裂缝的成因及其发育条件

在综合分析地裂缝发育特征、地裂缝发育区的地质环境及新构造活动背景基础上，作者认为：山西断陷带的地裂缝是在新构造活动加强的背景下形成的，地下水超采及地层、地貌等非构造环境对地裂缝的发育起着重要的制约作用．     

工业企业厂界噪声监测的背景值修正与测量不确定度分析

根据噪声背景值修正理论,分析修正的误差和测量不确定度,提出了工业企业厂界噪声监测背景值修正的合理方法。     

近十年气候变化对黄河中上游水沙影响分析

本文针对１９８６￣１９９５年黄河中上游平均年径流量为５０年代以来最小值，而入黄泥沙量去未出现相应减少的异常现象，着重分析了同期的气候背景，发现流域降水、气温、以及与其相关联的西太平洋副热带高压，青茂高原区与印缅槽区的高度场、台风活动等要素都出现了气候突变。自９０年代开始热带太平洋发生了百年罕见的持续性长ＥＮＳＯ现象，并连续发生了３次ＥＮＳＯ事件，均属百年罕见。正是由于诸因素的异常变化，从而导致黄河     

Race and the workforce: Occupational status, aspirations, and stereotyping among African American children.

This study examined whether African American children's perceptions of occupational status and their own vocational interests are affected by racial segregation of the workforce. Children (N = 92) rated familiar occupations with respect to status, desirability, and stereotyping. Children also rated novel jobs that had been depicted with African Americans, European Americans, or both African and European Americans. As predicted, for familiar jobs, children's judgments were linked to their knowledge of racial segregation of these jobs. In addition, novel occupations that had been depicted with African Americans were judged as lower in status than the identical occupations that had been depicted with European Americans, demonstrating a causal influence of workers' race on children's judgments. Children's age and socioeconomic background moderated their occupational judgments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

用基本断裂功表征聚合物的韧性

基本断裂功 (EWF)是一种新型的高分子材料断裂韧性的评价方法 ,它与通常使用的应力强度因子、应变能量释放速率及J -积分相比 ,具有显著的优点 ,因此逐渐受到高分子材料研究领域的广泛重视。简要介绍了EWF方法的理论背景和计算方法 ,同时还讨论了影响EWF参数的因素     

合肥电子同步辐射实验室周围土壤中的放射性核素

能量较高的加速器装置对环境的影响,主要来源于两个方面:一是当装置运行时产生的瞬发辐射场。其辐射成分为γ、n、μ介子及其他强子。二是由于强子级联和电磁级联的传输与发展而形成的剩余辐射场,包括在加速器部件、隧道墙壁、冷却水及土壤屏蔽层中产生的感生放射性。     

红外变像管封管后的热处理：提高其性能和可靠性的一项重大措施

提出了一种封管后的热处理工艺，应用这种工艺，可提高红外变像管的低照度鉴别率，降低等效背景照度，并使管子内的真空状态得到改善，从而使光电阴极的稳定性得到提高，增加了管子的可靠性。     

用位置敏感传感器进行位移测试的技术研究

目的 研究位置敏感传感器在位移测试中的优化应用。方法 从暗电流背景光的角度进行了分析，简化了电路和光路。结果 利用该方法，设计了一套位移测试系统。结论 所设计的系统正确可用，弥补了用位置敏感传感器作位移测试常见的不足。