Model Selection for Unsupervised Learning of Visual Context

This study addresses the problem of choosing the most suitable probabilistic model selection criterion for unsupervised learning of visual context of a dynamic scene using mixture models. A rectified Bayesian Information Criterion (BICr) and a Completed Likelihood Akaike’s Information Criterion (CL-AIC) are formulated to estimate the optimal model order (complexity) for a given visual scene. Both criteria are designed to overcome poor model selection by existing popular criteria when the data sample size varies from small to large and the true mixture distribution kernel functions differ from the assumed ones. Extensive experiments on learning visual context for dynamic scene modelling are carried out to demonstrate the effectiveness of BICr and CL-AIC, compared to that of existing popular model selection criteria including BIC, AIC and Integrated Completed Likelihood (ICL). Our study suggests that for learning visual context using a mixture model, BICr is the most appropriate criterion given sparse data, while CL-AIC should be chosen given moderate or large data sample sizes.     

Recent-onset ecstasy use: Association with deviant behaviors and psychiatric comorbidity.

Background: Despite increases in ecstasy (MDMA) use in the United States, little is known about characteristics linked with recent-onset ecstasy use, especially psychiatric symptoms and deviant behaviors. Aims: To test whether individuals with high levels of other drug use are more likely to be recent-onset ecstasy users; to test whether psychiatric symptoms in adults are associated with recent-onset ecstasy use; to explore the association between recent-onset ecstasy use and concomitant deviant behaviors in adolescents and adults. Methods: Data from the 2001 National Survey on Drug Use and Health. Findings: Recent-onset ecstasy use was significantly more likely to occur among adolescents and adults (18-34 years old) who engaged in deviant behaviors during the past year as compared with those who did not engage in deviant behaviors during the past year. Higher levels of deviancy indicated a higher likelihood of being a recent-onset ecstasy user, and associations were strongest with nonviolent deviant behaviors such as selling illegal drugs and stealing. Associations between deviant behaviors and recent-onset ecstasy use were similar in strength to associations between deviant behaviors and recent-onset cocaine and marijuana use, respectively. Adults who had past-year psychiatric symptoms (both depressive and panic symptoms) were twice as likely to be recent-onset ecstasy users as compared with those without past-year psychiatric symptoms. Greater levels of drug involvement increased the odds of being a recent-onset ecstasy user. Conclusion: Recent-onset ecstasy use seems to be associated with a range of other behavioral problems and may reflect one aspect of a larger problem behavior syndrome. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

NMDA Receptor Modulation of Incidental Learning in Pavlovian Context Conditioning.

Rats exposed to a footshock show conditional fear when reexposed to the shock context. Immediate presentation of shock after placement in the context significantly reduces this fear. Preexposure to the context in the absence of shock, coupled with a minimum preshock interval during training, overcomes this immediate shock deficit. Because rats learn about the context during preexposure and express that learning after being reinforced, the context preexposure effect is an aversive analogue of latent learning. The authors examined the effect of the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-5-phosphovalerate (APV) on the facilitatory effect of context preexposure. Rats were preexposed to a chamber after APV administration. The next day they were placed in the same chamber without drug and received shock 35 s later. APV blocked the facilitatory effect of preexposure. Therefore NMDA receptors are important for contextual latent learning. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

云南磷肥工业副产氟资源综合利用途径初探

根据云南磷肥工业发展情况 ,提出对磷肥工业副产氟资源综合利用的设想 ,并介绍目前国内已有的一些氟资源综合利用的工艺技术     

一种新颖的MEMS光开关测量平台的设计与实现

随着光电器件的广泛应用，微机械光开关成为核心光交换器件的主流。在研发过程中，其器件检测手段成为人们所关注的话题。本文介绍了一种新颖的测量平台，通过高幅值利用单片机控制脉冲频率的方法来选择器件。与当前同类方法相比，具有精度高、可靠性强、成本低、易操作等特点，具有广阔的使用前景。     

乡镇供水工程设计中应注意的若干问题

乡镇供水作为水利开发建设中的一个新领域，设计工作是龙头，有许多技术问题需要研究和探索，阐述了乡镇供水工程设计应注意的若干问题，并对设计中存在的一些具体问题进行了分析和探讨。     

与历史的对话与自然的交流—解析衢州市花园岗中心区城市设计

以衢州市花园岗中心区为例,提出城市设计要在尊重历史文化的基础上,结合自然地理条件,通过创造性的设计手段,来描绘未来城市中心区富有文化和生态内涵的全新形象。     

搪瓷釜的使用维护与常用修补方法

介绍搪瓷釜的使用维护要点，简单介绍目前国内外常用的搪瓷釜修补方法，从用、管、修相结合出发来延长搪瓷釜的使用寿命。     

几种重要的有机氯系阻燃剂

介绍了氯化石蜡、氯化聚乙烯、四氯邻苯二甲酸酐、四氯双酚A、六氯环戊二烯 及由六氯环戊二烯衍生的几种氯系阻燃剂的生产过程和用途。     

浅析2020年前美军事战略重点的转变--从装备发展看美国军事战略重点可能的变化

美国21世纪前期的军事战略重点将是争夺外空优势，夺取制天权和制信息权。分析了美国夺取外空优势的原因，及其为夺取外空优势在国家政策、航天发展和技术准备等方面采取的措施。