Approximation of the distribution of excesses through a generalized probability-weighted moments method

The POT (peaks-over-threshold) approach consists in using the generalized Pareto distribution (GPD) to approximate the distribution of excesses over a threshold. In this paper, we consider this approximation using a generalized probability-weighted moments (GPWM) method. We study the asymptotic behaviour of our new estimators and also the functional bias of the GPD as an estimate of the distribution function of the excesses. A simulation study is provided in order to appreciate the efficiency of our approach.     

Ownership structure and investment-cash flow sensitivity

This study investigates the effect of ownership structure on the use of cash flow in financing corporate investments—the investment-cash flow sensitivity—in a concentrated ownership context. Using a sample of 6797 French listed firms from 2000 to 2013, results show that investment-cash flow sensitivity decreases with the cash-flow rights of the controlling shareholder and increases with the separation of its cash-flow and control rights (excess control rights). Firms are, thus, less likely to use cash flow in investments when the interests of controlling shareholders are aligned with those of minority shareholders. However, they appear to use considerable internal funds for their investments when they have severe agency problems, driven by excess control rights of the controlling shareholders. Overall, our findings help advance the understanding of the role of agency relationship in shaping corporate financial policy.     

Particle swarm optimization based-algorithms to solve the two-machine cross-docking flow shop problem: just in time scheduling

Cross-docking is an innovative logistical strategy which provides less inventory holding costs, less transportation costs and fast customer deliveries without storage in between or less than 24 hours. In this paper, we address the two-machine cross-docking scheduling problem within a Just-In-Time (JIT) context. This latter requires the punctuality and exactness of product deliveries. To satisfy this target, we aim to minimize the total earliness and tardiness, then early or tardy deliveries are discouraged. This study presents a great contribution in solving such NP-hard problem while applying different versions of the PSO (Particle Swarm Optimization) algorithm. One of them is hybridized with the Genetic Algorithm (GA). This latter is then shown to be the best one over computational experiments using different sized instances and by determining a percentage deviation from a developed lower bound.

     

A new process for modeling heartbeat signals during exhaustive run with an adaptive estimator of its fractal parameters

This paper is devoted to a new study of the fractal behavior of heartbeats during a marathon. Such a case is interesting since it allows the examination of heart behavior during a very long exercise in order to reach reliable conclusions on the long-term properties of heartbeats. Three points of this study can be highlighted. First, the whole race heartbeats of each runner are automatically divided into several stages where the signal is nearly stationary and these stages are detected with an adaptive change points detection method. Secondly, a new process called the locally fractional Gaussian noise (LFGN) is proposed to fit such data. Finally, a wavelet-based method using a specific mother wavelet provides an adaptive procedure for estimating low frequency and high frequency fractal parameters as well as the corresponding frequency bandwidths. Such an estimator is theoretically proved to converge in the case of LFGNs, and simulations confirm this consistency. Moreover, an adaptive chi-squared goodness-of-fit test is also built, using this wavelet-based estimator. The application of this method to marathon heartbeat series indicates that the LFGN fits well data at each stage and that the low frequency fractal parameter increases during the race. A detection of a too large low frequency fractal parameter during the race could help prevent the too frequent heart failures occurring during marathons.     

2010～2011年突尼斯变革:起因与现状

2010年12月17日,突尼斯"茉莉花革命"爆发后,总统本.阿里带家人离境,飞抵沙特阿拉伯,结束了其长达23年的统治。随后,在突尼斯变革的"雪球效应"的影响下,埃及、利比亚、也门、叙利亚以及其他阿拉伯国家相继发生了反政府的变革。本文着重探讨导致2010～2011年突尼斯变革的内外原因,阐述变革后突尼斯的政局现状并展望其未来走向。