WTO — a deterministic approach to 4-fermion physics

The program WTO, which is designed for computing cross sections and other relevant observables in the e⁺e⁻ annihilation into four fermions, is described. The various quantities are computed over both a completely inclusive experimental set-up and a realistic one, i.e. with cuts on the final state energies, final state angles, scattering angles and final state invariant masses. Initial state QED corrections are included by means of the structure function approach while final state QCD corrections are applicable in their naive formulation. A gauge restoring mechanism is included according to the Fermion-Loop scheme. The program structure is highly modular and particular care has been devoted to computing efficiency and speed.     

Singular eigenfunction analysis of transport problems with spatially dependent cross sections — An overview

A substantial amount of recent work has been done in applying singular eigenfunctions to transport problems whose cross sections vary continuously with position. In this article we survey the methodology and results so far obtained, and we briefly discuss some of the many open questions.     

A procedure for outlier identification in data sets from continuous distributions

We propose a procedure, based on sums of reciprocals ofp-values, for the identification of outliers in univariate or multivariate data sets coming from continuous distributions. Using results of Csörg? (1990), we find the limiting distribution of the relevant statistic for completely specified models. By simulations, we obtain approximate quantiles for the asymptotic distribution, (which does not depend on the specific model or the dimension where the data live) and for the finite sample distribution in different dimensions of our statistic when parameters are estimated, for the multivariate Gaussian model and a multivariate double exponential model with independent coordinates. Monte Carlo evaluation shows that the procedure proposed is effective in the identification of outliers, and that it is sensitive to sample size, a feature seldom found in outlier identification methods.     

Discontinuity, decision and conflict

Summary The motivation for this paper arises out of the authors experiences in modelling real decision makers where the decisions show not only a continuous response to a continuously changing environment but also sudden or discontinuous changes. The theoretical basis involves a parametric characterisation of the environment, a decision makers perception of it in terms of a twice differentiable Distribution Function and a bounded Loss Function. Under a specified, minimizing dynamic, the resultant Expected Loss Function satisfies the conditions for a potential function and Thoms Catastrophe Classification Theorem may be used to assess the singularity points and the thresholds at which jump decisions are taken. The paper describes the theory, summarises some results on unimodal distributions illustrated by jump decisions and population polarisation. Mixture distributions are then examined and the E^* models defined. These are then briefly illustrated by reference to models which have been constructed in relation to Prison Riots, Agricultural and Economic modelling.     

On discrete multivariate distributions symmetric in frequencies

In this paper we describe a new class of discrete multivariate distributions which verify that their probability mass function is invariant when their univariate variables are permuted. These distributions may be generated by a multivariate extension of the Gauss function₂ F ₁ with matrix argument. A methodology that permits the fit of these distributions to real data is developed. A fit of a distribution for bivariate real data is shown and is compared with fits obtained by means of other usual bivariate distributions generated by extensions of the Gauss function.     

Influence diagnostics in log-Birnbaum-Saunders regression models with censored data

In this paper we discuss log-Birnbaum-Saunders regression models with censored observations. This kind of model has been largely applied to study material lifetime subject to failure or stress. The score functions and observed Fisher information matrix are given as well as the process for estimating the regression coefficients and shape parameter is discussed. The normal curvatures of local influence are derived under various perturbation schemes and two deviance-type residuals are proposed to assess departures from the log-Birnbaum-Saunders error assumption as well as to detect outlying observations. Finally, a data set from the medical area is analyzed under log-Birnbaum-Saunders regression models. A diagnostic analysis is performed in order to select an appropriate model.     

基于Borel测度峰值判定的欠定混合盲语音信号分离

简要介绍稳定分布的特征函数及其Borel测度表示,给出了Borel测度的估计方法,并利用Borel测度的峰值确定混合矩阵的基矢量,从而可以确定各个独立分量,实现信号的盲分离。计算机模拟和分析表明,这种算法是一种在高斯和分数低阶Alpha稳定分布噪声条件下具有良好韧性的独立分量分析与盲源分离方法,在盲语音混合信号的分离应用中也得到了很好的效果。     

Realization theory for two-time-scale distributions through approximation of Markov parameters

In this article, the problem of approximating the Markov parameters of a two-time-scale (TTS) distribution is studied. It is shown that the Markov parameters of a TTS distribution can be approximated in terms of the Markov parameters of its fast distribution only. This is an O(ε^1?i ) approximation, which deteriorates by a factor of 1/ε at each step as higher order Markov parameters are computed. In order to use the Markov parameters of the slow distribution in the approximation scheme, an inversion map is introduced by which a TTS distribution and its slow distribution are mapped into two new distributions. It is then shown that every Markov parameter of the inverted distribution approximates that of the inverted slow distribution with an O(ε) accuracy. An approximate expression for the Hankel matrix of the Markov parameters of a TTS distribution is also obtained. This expression is in the form of a telescopic series and involves the Markov parameters of the fast distribution only.     

Evolutionary algorithms for continuous-space optimisation

From a global viewpoint, evolutionary algorithms (EAs) working on continuous search-spaces can be regarded as homogeneous Markov chains (MCs) with discrete time and continuous state. We analyse from this viewpoint the (1?+?1)EA on the inclined plane fitness landscape, and derive a closed-form expression for the probability of occupancy of an arbitrary target zone, at an arbitrary iteration of the EA. For the hitting-time of an arbitrary target zone, we provide lower and upper bounds, as well as an asymptotic limit. Discretization leads to an MC with discrete time, whose simple structure is exploited to carry out efficient numerical investigations of the theoretical results obtained. The numerical results thoroughly confirm the theoretical ones, and also suggest various conjectures which go beyond the theory.     

RGB颜色模型应用于评价顶吹混匀时间的方法

针对评价顶吹宏观混匀时间的方法进行了气体顶吹搅拌水动力学实验研究,利用基于混合过程中示踪粒子的分布随时间演化规律的RGB颜色模型来确定搅拌容器内的宏观混匀时间。通过定义像素阈值分离每一像素,构建混匀像素比M值作为确定混匀时间的指标,观察M值的变化规律,利用3σ方法确定混匀时间。针对喷枪插入深度及流量,用量纲为1强度单位表述为0.5和1的实验工况一,当阈值分数X=90%时,测定混匀时间为13.30s。分析结果发现,RGB颜色模型能够基于混合过程中示踪粒子的分布情况确定混匀时间,且与贝蒂数法和电导率法测定的混匀时间偏差不超过10%。为解决在视觉上评价多相流混合效果等工程问题提供了一种新的思路,为提高ISA炉使用寿命、强化ISA炉冶炼生产以及优化ISA炉工艺过程提供了一定的实验依据。