On Order Statistics for GS-Distributions

In this article, a class of distributions is used to establish several recurrence relations satisfied by single and product moments of order statistics and progressive Type-II right censoring. The recurrence relations for moments of some specific distributions including uniform (a;b); exponential (λ); generalized exponential (α;λ;ν); beta (1;b); beta (b;1); logistic (α;β) and other distributions from order statistics and progressive Type-II right censoring can be obtained as special cases. A short explanation of GS-distribution can be found in reference [27]. As an example, means, variances and covariances for standard exponential distribution of progressive Type-II right censored order statistics are computed. Various characterizations of the recently introduced GS-distributions are presented. These characterizations are based on a simple relationship between two truncated moments ; on hazard function ; and on functions of order statistics. A characterization of the GS-distributions based on conditional moment of order statistics is extended to truncated moment of order statistics

Computing the Real Isolated Points of an Algebraic Hypersurface

Let $\mathbb{R}$ be the field of real numbers. We consider the problem of computing the real isolated points of a real algebraic set in $\mathbb{R}^n$ given as the vanishing set of a polynomial system. This problem plays an important role for studying rigidity properties of mechanism in material designs. In this paper, we design an algorithm which solves this problem. It is based on the computations of critical points as well as roadmaps for answering connectivity queries in real algebraic sets. This leads to a probabilistic algorithm of complexity $(nd)^{O(n\log(n))}$ for computing the real isolated points of real algebraic hypersurfaces of degree $d$. It allows us to solve in practice instances which are out of reach of the state-of-the-art.Comment: Conference paper ISSAC 202

Performance of privatised and private firms : empirical evidence from Egypt

Privatisation has been a major political and economic phenomenon over the past few decades, and researchers continue to target it for both theoretical and empirical work. The objective of this thesis is to evaluate the Egyptian experiment concerning its privatisation programme, and to determine whether this programme has affected the performance of privatised firms. Using 15 years of data, which cover the period 1990/1991 to 2004/2005; this thesis empirically investigates three main issues. Firstly, it examines whether the performance of privatised firms improves following privatisation through comparing pre- and postprivatisation performance in terms of profitability, operating efficiency, output, leverage and level of employment. Secondly, it evaluates the performance changes of privatised Egyptian firms after matching them to control firms (private firms) based on size and industry. Thirdly, it evaluates the impact of the post-privatisation sectoral environment and the pre-privatisation experience on post-privatisation performance. For the first two issues, several statistical techniques, such as parametric t-test, the non-parametric Wilcoxon signed-rank test, and Mann-Whitney test are performed. The results from this analysis indicate clearly that there are significant increases in both profitability and operating efficiency as well as significant declines in the leverage and employment, but there is no significant change in the output. Furthermore, the results show a significant difference in performance changes between privatised firms and private firms according to most performance measures. As to the third issue, several multi-regressions are used to model the relationship between the post-privatisation performance (as dependent variable) and ownership structure, the performance experience of the privatised firms pre-privatisation, the performance of their counterparts from competitor firms (private firms), and firm size (as independent variables). The results from this analysis demonstrate that the ownership structure really matters and that the performance of privatised firms depends on the degree of state ownership involvement; also, through the passage of time, the competitive environment has a significant impact on most performance measures of privatised firms. As such, this thesis represents the first study in Egypt to evaluate and compare the performance of privatised firms with the performance of their counterparts from private firms. The study contributes to the work on privatisation by comparing the performance changes of privatised firms to those of already private ones, so that the study can determine whether the post-privatisation performance matches that of the private firms. A caveat to the finding of this thesis is that the privatised firms might need a longer period to reflect more fully the impact of the privatisation programme on some of their performance measures.Arab Academy for Science and Technology, Egyp

Analysis of thermomechanical fatigue of unidirectional titanium metal matrix composites

Thermomechanical fatigue (TMF) data was generated for a Ti-15V-3Cr-3Al-3Sn (Ti-15-3) material reinforced with SCS-6 silicon carbide fibers for both in-phase and out-of-phase thermomechanical cycling. Significant differences in failure mechanisms and fatigue life were noted for in-phase and out-of-phase testing. The purpose of the research is to apply a micromechanical model to the analysis of the data. The analysis predicts the stresses in the fiber and the matrix during the thermal and mechanical cycling by calculating both the thermal and mechanical stresses and their rate-dependent behavior. The rate-dependent behavior of the matrix was characterized and was used to calculate the constituent stresses in the composite. The predicted 0 degree fiber stress range was used to explain the composite failure. It was found that for a given condition, temperature, loading frequency, and time at temperature, the 0 degree fiber stress range may control the fatigue life of the unidirectional composite

The Black Seed Nigella sativa Linnaeus - A Mine for Multi Cures: A Plea for Urgent Clinical Evaluation of its Volatile Oil

AbstractThis review almost covers what is actually known to date about the black seed and its constituents. It is clear that most of the potent and fruitful activity resides in its volatile oil and a protein component. However, the volatile oil suffers the drawback of the bronhoconstricting effect of thymoquinone. However, the latter can be easily removed from the oil to obtain a dethymoquinoneated oil that has already been shown to possess the major characteristics of the whole oil. At this moment there are a lot of experimental data that hopefully, may stimulate the beginning of the era of pilot clinical studies to evaluate the clinical potential of the volatile oil, some of the protein fractions and the dethymoquinoneated volatile oil. It is hoped that this plea will have a rapid response