Monitoring of zero-inflated binomial processes with a DEWMA control chart

Control charts are widely used for monitoring quality characteristics of high-yield processes. In such processes where a large number of zero observations exists in count data, the zero-inflated binomial (ZIB) models are more appropriate than the ordinary binomial models. In ZIB models, random shocks occur with probability θ, and upon the occurrence of random shocks, the number of non-conforming items in a sample of size n follows the binomial distribution with proportion p. In the present article, we study in more detail the exponentially weighted moving average control chart based on ZIB distribution (ZIB-EWMA) and we also propose a new control chart based on the double exponentially weighted moving average statistic for monitoring ZIB data (ZIB-DEWMA). The two control charts are studied in detecting upward shifts in θ or p individually, as well as in both parameters simultaneously. Through a simulation study, we compare the performance of the proposed chart with the ZIB-Shewhart, ZIB-EWMA and ZIB-CUSUM charts. Finally, an illustrative example is also presented to display the practical application of the ZIB charts.     

Single-Stage and Serial Production Line Systems with Unreliable Machines and General Probability Distributions

This paper presents stochastic models for analyzing production to stock and production on demand systems with arbitrary demand, production, machine breakdown and repair processes, and a finite buffer. Expressions are developed for the transition probabilities among the different states, the proportion of transitions that take the process to a particular state, the probabilities that the process is at a particular state, and the expected state residence times. Also, expressions are developed for some quantities of interest, like average inventory, percentage of lost sales, and expected waiting time. Applications are discussed for various demand, production, machine breakdown, and repair processes and numerical examples are presented. Guidelines are given for utilizing the models in evaluating the economic performance of production systems. Using an approximation procedure, the models are used for modeling multi-stage serial production to stock and production on demand lines. Simulation results indicated that the quality of the approximation is very good. The multi-stage models are useful in practical situations, because they allow the use of different probability distributions for the various processes (production, machine failure, etc.) of each stage.     

Close Approximations of Minimum Rectangular Coverings

We consider the problem of covering arbitrary polygons with rectangles. The rectangles must lie entirely within the polygon. (This requires that the interior angles of the polygon are all greater than or equal to 90 degrees.) We want to cover the polygon with as few rectangles as possible. This problem has an application in fabricating masks for integrated circuits.In this paper we will describe the first polynomial algorithm, guaranteeing an O(log n) approximation factor, provided that the n vertices of the input polygon are given as polynomially bounded integer coordinates. By the same technique we also obtain the first algorithm producing a covering which is within a constant factor of the optimal in exponential time (compared to the doubly-exponential known before).     

Native and Migrant Fertility Patterns in Greece: A Cohort Approach

This article examines fertility patterns and differentials between native women, and Albanian and Bulgarian immigrants, using data from the 2001 census of Greece on the reported numbers of children ever-born alive by citizenship. The analysis focuses on changing fertility timing and quantum of women born between 1950 and 1970, and reveals that cohort fertility is highest among Albanians and lowest among Bulgarians, while levels for native women are somewhere in between. Completed cohort fertility is decreasing over time for all nationalities, while the gap observed among the ethnic groups has been narrowing. Evidence based on the 2001 censuses of Albania and Bulgaria indicates that immigrants in Greece constitute, to some extent, selected groups, compared to the inhabitants of their countries of origin.     

The First Exit Time Theory Applied to Life Table Data: The Health State Function of a Population and Other Characteristics

In this article, we summarize the main parts of the first exit time theory developed in connection to the life table data and the resulting theoretical and applied issues. New tools arise from the development of this theory and especially the Health State Function and some important characteristics of this function.

We provide both simple and complex models and propose a methodology for reconstructing the health state function from the provided first exit time density distribution (for the appropriate computer program, see http://www.cmsim.net). In the simpler case, this theory is applied for the reconstruction of the so-called Inverse-Gaussian function.     

The effects of board size and ‘busy’ directors on the market value of Italian companies

This paper presents evidence that corporate governance quality measured by (1) the board size and (2) the fraction of directors that serve on more corporate boards, influences the market value of firms. The analysis is based in Italy, a country that is characterized by family and concentrated ownership, low legal protection of investors and pyramidal firm structures. Our empirical results suggest that the level of ‘busy-ness’ of corporate directors as a measure of board effectiveness has a significant influence on firm’s market performance. By contrast, we find limited evidence that board size has a substantial impact on the market valuation, except in small and medium enterprises and in some specific industry sectors.

Civil Society Organizations and Labour Market Integration for Refugees and Asylum Seekers in Greece

VOLUNTAS: International Journal of Voluntary and Nonprofit Organizations - The 2015 crisis of refugee policies saw an upgrade in the role of civil society organizations (CSOs) as service providers...     

Wage Structure,Incomes Policy and Decentralised Bargaining: the Case of Greece

Abstract. Developments in Greek industrial relations suggest that decentralised bargaining is not a panacea. The manufacturing wage structure in Greece has an exceptional course associated with the rise of informal decentralised bargaining. Interindustry wage differentials increased in a period of incomes policies aiming to narrow the wage structure. The influence exerted by inflation and unemployment is, compared to past evidence from the US. and the U.K., quite unconventional. Under informal bargaining, high-wage powerful industrial branches “benefit” from higher inflation and lower unemployment.     

Aspects of Relative Wage Flexibility in Greece

Abstract. Flexibility in relative wages can be either competitive or non-competitive. In Greece, in the period 1966–1988, wage and employment regulation as well as developments in industrial relations did not favour competitive flexibility and provided an environment conducive to non-competitive flexibility. With the noticeable exception of the period 1967–74, during which competitive forces emerged and played a dominant role, in 1966–88 the manufacturing labour market operated under the influence of industry-specific factors. Non-competitive flexibility associated with industry-specific changes in productivity in the long run and industry-specific rates of strike activity in the short run, influenced manufacturing relative wages. Furthermore, in 1977–88, the asymmetric response of industry wages to changes in industry productivity hindered employment growth.