A comparison of analysis procedures for correlated binary data in dedicated multi‐rater imaging trials

In this paper, three analysis procedures for repeated correlated binary data with no a priori ordering of the measurements are described and subsequently investigated. Examples for correlated binary data could be the binary assessments of subjects obtained by several raters in the framework of a clinical trial. This topic is especially of relevance when success criteria have to be defined for dedicated imaging trials involving several raters conducted for regulatory purposes. First, an analytical result on the expectation of the ‘Majority rater’ is presented when only the marginal distributions of the single raters are given. The paper provides a simulation study where all three analysis procedures are compared for a particular setting. It turns out that in many cases, ‘Average rater’ is associated with a gain in power. Settings were identified where ‘Majority significant’ has favorable properties. ‘Majority rater’ is in many cases difficult to interpret. Copyright © 2014 John Wiley & Sons, Ltd.     

人脸识别系统的构建

简单介绍了构建一个完整的人脸识别系统的硬件架构,初步谈了人脸识别系统设计中需要考虑的一些共性关键问题,如现场环境设计、摄像设备的选择与安装、人脸识别系统的设计流程、总体规划设计等。从工程应用的角度对人脸识别系统的开发步骤和相关技术做了较为详细的描述。     

小儿先天性心脏病的探查分析

目的:通过彩超对先天性心脏病进行探查、分类,明确诊断,早期治疗。方法:采用美国惠普公司生产的HP7500彩色多普勒超声心动仪与美国GE公司生产的GE vivid7型彩色多普勒超声心动仪,对2008-2010年临床疑诊为先天性心脏病的患儿256例进行检查,检出先天性心脏病患儿210例。结果:检出室间隔缺损83例,占39.5%,室间隔膜部瘤并室缺15例,并房间隔缺损20例。②房间隔缺损55例,占26.1%,③动脉导管未闭38例,占18.9%,④法四15例,占0.07%;⑤心内膜垫缺损9例,占0.04%;⑥永存动脉干3例,占0.014%;⑦三尖瓣闭锁2例,占0.01%;⑧右室双出口2例,占0.01%;⑨原发性肺动脉高压2例,占0.005%;⑩右位心,肺静脉异位引流1例,占0.005%。结论:彩超诊断小儿先天性心脏病准确并且无创,对手术方式的选择和术后评价提供了有价值的临床资料。     

火电企业环境成本估算模型研究

在全面介绍环境成本相关理论的基础上,阐述了火电企业环境成本的计算方法,提出了火电企业环境成本估算模型,并结合火电企业环境成本的现状,论证了火电企业全面使用排污设备对实现资源的优化配置和减少污染物排放的作用.     

基于模糊集理论的MCM热分布算法研究

基于模糊集理论,提出了MCM模糊热分布算法。算法中MCM的每个芯片受到芯片间的排斥力、基板边缘对芯片的吸引力及基板中心对芯片的吸引力三种视在作用力。通过模糊推理规则分析了这些力和芯片分布间的模糊关系。高度法解模糊化后,以三力之和最小时的芯片分布作为最佳芯片分布方案。利用有限元法验证了模糊热分布算法的有效性,并将仿真结果与采用四分法得到的结果比较,表明利用该算法得到的MCM热分布比采用四分法得到的热分布更合理、更稳定。     

Statistical approaches in quantitative positron emission tomography

Positron emission tomography is a medical imaging modality for producing 3D images of the spatial distribution of biochemical tracers within the human body. The images are reconstructed from data formed through detection of radiation resulting from the emission of positrons from radioisotopes tagged onto the tracer of interest. These measurements are approximate line integrals from which the image can be reconstructed using analytical inversion formulae. However these direct methods do not allow accurate modeling either of the detector system or of the inherent statistical fluctuations in the data. Here we review recent progress in developing statistical approaches to image estimation that can overcome these limitations. We describe the various components of the physical model and review different formulations of the inverse problem. The wide range of numerical procedures for solving these problems are then reviewed. Finally, we describe recent work aimed at quantifying the quality of the resulting images, both in terms of classical measures of estimator bias and variance, and also using measures that are of more direct clinical relevance.     

Nonparametric bootstrap of sample means of positive-definite matrices with an application to diffusion-tensor-imaging data analysis

This paper presents nonparametric two-sample bootstrap tests for means of random symmetric positive-definite (SPD) matrices according to two different metrics: the Frobenius (or Euclidean) metric, inherited from the embedding of the set of SPD metrics in the Euclidean set of symmetric matrices, and the canonical metric, which is defined without an embedding and suggests an intrinsic analysis. A fast algorithm is used to compute the bootstrap intrinsic means in the case of the latter. The methods are illustrated in a simulation study and applied to a two-group comparison of means of diffusion tensors (DTs) obtained from a single voxel of registered DT images of children in a dyslexia study.     

铸型—冷铁—金属传热特性的研究

本文通过实验,测出冷铁在铸件凝固过程中的温度变化,找出铸件与冷铁间的等效界面热阻值,此值可供模拟铸件凝固时应用。     

内燃机活塞三维热分析

介绍高温状态下内燃机活塞的热分析原理,利用有限元法计算活塞温度、热变形和热应力,建立活塞三维热分析有限元模型和相应热边界条件,给出了活塞温度分布、综合应力和综合变形,提出对活塞设计的合理结论。     

稀土元素对喷焊层组织性能的影响

在 Ni基合金粉中加入一定比例的稀土元素 ,具有细化晶粒 ,改善组织形态作用 ,从而使其硬度、耐磨性和抗热疲劳性能均优于不含稀土元素的同类合金粉末