Statistical estimation of internal available bandwidth

This paper presents a method for using end-to-end available bandwidth measurements in order to estimate available bandwidth on individual internal links. The basic approach is to use a power transform on the observed end-to-end measurements, model the result as a mixture of spatially correlated exponential random variables, carryout estimation by moment methods, then transform back to the original variables to get estimates and confidence intervals for the expected available bandwidth on each link. Because spatial dependence leads to certain parameter confounding, only upper bounds can be found reliably. Simulations with ns2 show that the method can work well and that the assumptions are approximately valid in the examples.     

Bayesian model comparison for compartmental models with applications in positron emission tomography

We develop strategies for Bayesian modelling as well as model comparison, averaging and selection for compartmental models with particular emphasis on those that occur in the analysis of positron emission tomography (PET) data. Both modelling and computational issues are considered. Biophysically inspired informative priors are developed for the problem at hand, and by comparison with default vague priors it is shown that the proposed modelling is not overly sensitive to prior specification. It is also shown that an additive normal error structure does not describe measured PET data well, despite being very widely used, and that within a simple Bayesian framework simultaneous parameter estimation and model comparison can be performed with a more general noise model. The proposed approach is compared with standard techniques using both simulated and real data. In addition to good, robust estimation performance, the proposed technique provides, automatically, a characterisation of the uncertainty in the resulting estimates which can be considerable in applications such as PET.     

采用单测量源的拓扑推断算法

为了减少拓扑推断中需要时钟同步和节点间合作的限制,提出了一种仅需要单个测量源并且不需要时钟同步的运输车测量方法,该方法可以测量目的地址共享链路的排队时延。设计了根据排队时延推断拓扑结构的算法。理论证明了基于运输车测量方法和排队时延推断网络拓扑的可行性和正确性,并通过NS2进行了仿真,仿真结果表明基于运输车测量方法和排队时延能够准确的推断网络拓扑结构。     

多排螺旋CT冠状动脉CTA在老年人冠状动脉狭窄筛查中的作用

目的以选择性冠状动脉造影为标准,评价40（排）层螺旋CT冠状动脉血管成像于老年人冠状动脉狭窄筛查中的价值。方法对40例老年可疑冠心病患者行40-MSCT冠状动脉CTA检查后,利用心电图门控期相重建、最大密度投影、容积成像、曲面成像、多平面重组等后处理方法对所有冠状动脉及其分支进行重建,统计可供临床评价的管径〉1.5mm。冠状动脉段,以选择性冠状动脉造影（SCA）作对照,对比分析其诊断各类型冠状动脉狭窄的敏感性、特异性和准确性。结果40例患者共分析血管节段364个,较SCA显示率为93.8%。40层（排）螺旋CT对冠状动脉狭窄病变的总体判断敏感性为91.0%,特异性为85.6%,阳性预测值为82.6%,阴性预测值为92.7%,准确性87.9%,其中以阴性预测值最高。结论40-MSCT冠状动脉CTA可获得较好的图象质量用于诊断冠状动脉狭窄,是一种无创、可靠、有效的冠状动脉检查方法,可作为老年人冠状动脉狭窄筛查的非创伤性方法用于临床。     

光学CT中干涉投影图像的计算机处理

论述了光学计算机层面分析方法（ＯＣＴ）重建物体内部三维图像的原理，讨论了利用计算机ＯＣＴ技术处理全息干涉图像的方法．     

An application of lomax distributions in receiver operating characteristic(roc)curve analysis

Receiver operating characteristic(ROC)curves are useful for studying the performance of diagnostic tests. ROC curves occur in many fields of applications including psychophysics, quality control and medical diagnostics. In practical situations, often the responses to a diagnostic test are classified into a number of ordered categories. Such data are referred to as ratings data. It is typically assumed that the underlying model is based on a continuous probability distribution. The ROC curve is then constructed from such data using this probability model. Properties of the ROC curve are inherited from the model. Therefore, understanding the role of different probability distributions in ROC modeling is an interesting and important area of research. In this paper the Lomax distribution is considered as a model for ratings data and the corresponding ROC curve is derived. The maximum likelihood estimation procedure for the related parameters is discussed. This procedure is then illustrated in the analysis of a neurological data example.     

31例胸内结节病的影像学分析

目的 :探讨胸内结节病的平片与CT影像特征及临床诊断价值。方法 :回顾性分析 31例结节病的影像学特征并随访其激素治疗后影像学表现。结果 :肺门淋巴结增大 ,CT显示 2 6例 ,平片显示 2 2例 ;纵隔淋巴结增大 ,CT显示 2 8例 ,平片显示 1l例 ;肺内病灶呈多形性表现 ,无特异性 ,以CT敏感度高 ;胸膜病变较少见。 3年随访发现 2 5例治疗有效 ,8例有反复。结论 :淋巴结增大是本病的主要影像学表现。X线结合CT检查在诊断胸内结节病、判断活动期、评价激素治疗效果方面 ,具有一定的临床价值。     

The Diffusion of Innovations: A Methodological Reappraisal

Studies of diffusion have traditionally relied on specific distributions, primarily the logistic, to characterize and estimate those processes. We argue that such an approach gives rise to serious problems of comparability and interpretation and may result in large biases in the estimates of the parameters of interest. We propose instead the Gini's expected mean difference as a measure of diffusion speed. We discuss its advantages over the traditional approach, present a nonparametric estimation procedure, and tackle with it the problems of truncated processes and of intergroup comparisons. We also elaborate on the use of the hazard rate and suggest various extensions. The diffusion of computed tomography scanners is presented as an illustration.     

An invitation to quantum tomography

Summary.  We describe quantum tomography as an inverse statistical problem in which the quantum state of a light beam is the unknown parameter and the data are given by results of measurements performed on identical quantum systems. The state can be represented as an infinite dimensional density matrix or equivalently as a density on the plane called the Wigner function. We present consistency results for pattern function projection estimators and for sieve maximum likelihood estimators for both the density matrix of the quantum state and its Wigner function. We illustrate the performance of the estimators on simulated data. An EM algorithm is proposed for practical implementation. There remain many open problems, e.g. rates of convergence, adaptation and studying other estimators; a main purpose of the paper is to bring these to the attention of the statistical community.     

基于探测包群的单播链路丢包率估计

针对单播链路丢包率估计问题,在现有方法的基础上,给出了探测包群的方法,在保证测量有效性的前提下,极大地减少了探测包的发送数量;同时提出网络层析成像的三叉树模型,增加了丢包率估计所使用的方程数目。仿真结果验证了三包组方法及三又树模型,提高了求解的精度和稳定性。