Model-based computed tomography image estimation: partitioning approach

ABSTRACT

There is a growing interest to get a fully MR based radiotherapy. The most important development needed is to obtain improved bone tissue estimation. The existing model-based methods perform poorly on bone tissues. This paper was aimed at obtaining improved bone tissue estimation. Skew-Gaussian mixture model and Gaussian mixture model were proposed to investigate CT image estimation from MR images by partitioning the data into two major tissue types. The performance of the proposed models was evaluated using the leave-one-out cross-validation method on real data. In comparison with the existing model-based approaches, the model-based partitioning approach outperformed in bone tissue estimation, especially in dense bone tissue estimation.     

A weakly informative prior for Bayesian dynamic model selection with applications in fMRI

In recent years, Bayesian statistics methods in neuroscience have been showing important advances. In particular, detection of brain signals for studying the complexity of the brain is an active area of research. Functional magnetic resonance imagining (fMRI) is an important tool to determine which parts of the brain are activated by different types of physical behavior. According to recent results, there is evidence that the values of the connectivity brain signal parameters are close to zero and due to the nature of time series fMRI data with high-frequency behavior, Bayesian dynamic models for identifying sparsity are indeed far-reaching. We propose a multivariate Bayesian dynamic approach for model selection and shrinkage estimation of the connectivity parameters. We describe the coupling or lead-lag between any pair of regions by using mixture priors for the connectivity parameters and propose a new weakly informative default prior for the state variances. This framework produces one-step-ahead proper posterior predictive results and induces shrinkage and robustness suitable for fMRI data in the presence of sparsity. To explore the performance of the proposed methodology, we present simulation studies and an application to functional magnetic resonance imaging data.     

Empirical likelihood ratio under infinite second moment

In this article, we show that the log empirical likelihood ratio statistic for the population mean converges in distribution to χ²₍₁₎ as n → ∞ when the population is in the domain of attraction of normal law but has infinite variance. The simulation results show that the empirical likelihood ratio method is applicable under the infinite second moment condition.     

21世纪旅游发展的新领域:景区周边环境——综述研究与评论

随着旅游业的快速发展和城镇现代化的推进、景区周边涌现出了大量与景区不协调的问题,同时,由于人们对景区所处背景环境标准的提高,忽视周边环境与景区完整性的做法已不能适应新时代旅游者的需求。未来景区的竞争已经延伸到景区周边环境范围,为此,景区周边环境亦成为新世纪旅游发展及研究的一个新领域。提出景区周边环境的概念,通过检索和查阅国内外相关文献及全文电子期刊,发现旅游环境领域对景区周边环境这一范围地带的专门探讨尚属空白;针对景区周边环境的研究中,国内多从文物保护、资源开发、景观生态学角度出发,但或对周边环境的范围划定很大或过大,旅游实践的指导意义不强,或虽着眼于景区的可持续发展,但仍停留于“引起注意”的层面上,或未被重点对待,总体看来,国内研究不仅数量较少,且发掘得不够深入,缺乏从旅游角度对其进行的全方面审视,国外旅游理论对景区周边环境的关注也甚显微弱。针对这些讨论比较沉寂的局面,认为景区周边环境的理论研究应该跟上紧迫的现实需要,以促进景区的科学发展。     

双层稀土锰氧化物La2-2xSr1+2xMn2O7的ESR研究

电子自旋共振(简称ESR)是一种研究磁性关联的很有效的的实验手段.通过测量样品的变温ESR谱线,分析谱线参数随温度的变化关系,能够获得很多关于静态和动态磁耦合的信息.本文采用光学浮区炉制备锰氧化物La2-2x Sr+2x Mn2 O7(x=0.38)单晶样品,利用电子自旋共振研究层状锰氧化物单晶的MnO2双层问(interlayer)的耦合能.谱线中出现了代表层间反铁磁关联的高场光学模和低场声学模.通过分析声学模与光学模的共振场与积分强度随温度的变化,发现这些层间的反铁磁随着温度的变化逐渐发展,这表明利用铁磁共振方法能够研究层状锰氧化物La2-2x Sr+2x Mn2 O7的层间耦合,研究结果为这个体系内磁性关联的研究提供了一种新的方法.     

Q235钢静载拉伸磁记忆检测试验

为了研究磁记忆信号和应力之间的关系,采用磁记忆方法检测单向静载拉伸后Q235钢板表面磁场强度法向分 量Hp(y),并设计了更方便检测的拉伸试样。结果表明Q235试件断裂前磁场法向分量检测曲线为斜直线,具有唯一的 极性翻转点。同时还发现Q235材料处在弹性阶段时磁参数m值变化较慢,在塑性变形阶段时磁参数m值变化较快。     

肇庆市的旅游吸引与旅游形象建设

分析了肇庆的旅游区位优势及其丰富的旅游资源,指出了广东南线深圳、珠海旅游吸引的强化及其对肇庆旅游客源的明显分流作用使肇庆旅游业发展受到强有力的挑战,认为旋庆应从旅游区位、旅游资源、旅游项目方面构造更高层次的旅游吸引,树立新的旅游形象,使旅游业成为经济发展的支柱产业。     

人类应有的前行姿态——论《呼啸山庄》对野性与文明的取舍

艾米莉.勃朗特在《呼啸山庄》里建构起分别象征着野性生存状态的呼啸山庄与文明生存形态的画眉山庄,而生长于其中的人也因此形成了鲜明的个性精神特征。这两种相对的生存形态相互撞击之后就形成了持久而激烈的既相互吸引又相互抗争的格局。该文从生长于其中的两代人在文明与野性的取舍的成败得失——凯瑟琳.恩萧的悲剧性选择、希刺克厉夫野性复仇的失落以及哈里顿与小凯蒂的完美结合——的分析出发,认为《呼啸山庄》蕴涵了这样一种理念:在人类从野性走向文明的历程中,个体须保有这样的一种前行姿态,即保留野性生存状态中的自由奔放的生命意识和不屈不挠的生存意志,经过从善从美的文明行为方式的引导来实现个体的自我完善和积极扬弃,人类才能获得灵魂的真正自由和心灵的持久安宁。     

The science of attracting foster carers

Across the world the number of children needing a foster home is increasing; however, the number of individuals willing to foster a child is decreasing. It is therefore critical to gain insight into the barriers preventing people from fostering a child. Using data from a 2009 survey of 756 Australians, combinations of barriers are investigated by conducting a posteriori segmentation analysis within the market of potential foster carers. Four segments are identified and profiled to determined significant differences in terms of psychological and socio‐demographic characteristics. Findings, including the fact that almost one‐third of respondents indicated that they had not considered foster caring before because no one had ever asked them to, have practical implications. Improved marketing strategies tailored to the characteristics of each segment are required to harvest the full potential of individuals willing to foster a child and thus contribute to solving one of the most difficult social challenges facing developed nations.     

AMC用于传输、辐射及散射问题的研究进展

介绍了人工磁导体用于波导传输、天线辐射和隐身材料的研究进展。通过金属导体和人工磁导体构造虚拟电/磁壁,设计了新型的平行板波导;利用人工磁导体作反射板,可实现低剖面天线系统的设计,并且通过改变极化依赖型人工地板上偶极子的取向,能够获得圆极化辐射特性;通过在人工磁导体上加载合适的电阻,可设计超薄的雷达吸波材料;利用人工磁导体反射相位特性,可设计低RCS的反射屏。