Stratification and mobility in contemporary Egypt

The objectives in this statement are to characterize and explain the patterns of change in stratification and mobility in Egypt, over the last half century, by placing them within conceptual, explanatory, and historical contexts. First, literature relevant to the primary concepts of "class" and "status", is reviewed. Second, four institutions whose influence is fundamental in shaping these patterns are identified to form an explanatory context: family, polity, economy, and education. And third, an historical account is presented to demonstrate the interplay of these institutions and their consequences for stratification and mobility. For this, four periods are identified that are marked by change in the dominance of institutions and their corresponding influence on stratification and mobility. In addition to data available in relevant literature, this analysis utilizes primary data generated through a national probability household survey.     

Scheduling to minimize stringer utilization for continuous annealing operations

In this paper we present a mathematical program and heuristic algorithms to schedule coils for the production operations in a copper (or steel) coil manufacturing industry. The processing facility uses continuous operations for processing (e.g., galvanizing and annealing) while the handling unit is a discrete coil. The ends of coils are “stitched” or welded together to enable continuous processing, and the joint is later sheared off to obtain the processed coils. Processing constraints impose restrictions on the compatibility between a pair of coils that are overcome by introducing a dummy coil called stringer, which is very expensive to a mill. This paper deals with modeling the sequencing/scheduling problem of coils on parallel non-identical machines to minimize stringer utilization. Both computational and practical experiences show the efficiency and effectiveness of the solution approaches. Implementing these methods in an actual coil annealing facility resulted in 65% reduction in stringer utilization.     

Estimation of parameters of the inverse gaussian-weibull mixture model

The main objective of this work is to estimate the 5-dime-nsional vector of parameters (p,μ,λ,α,c) of the mixture of an Inverse Gaussian IG(μ,λ) and Weibull W(α,c) distributions with mixing proportion p. We use the maximum Likelihood method (MLM) and the weighted maximum likelihood method (WMLM), both under the sampling schemes suggested by Hosmer (1973). Simulation study shows that the WMLM performs best, when Hosmer's model 2 is used, in the sense of minimizing the mean square error.     

Efficiency of schemes of sampling from the inverse gaussian-weibull mixture model

The objective of this paper is to study the efficiency of sampling schemes suggested by Hosmer(1973), termed models Ml and M2, relative to the regular random sampling, termed model MO, when samples are drawn from a population having the Inverse Gaussian-Weibull (IG-W) mixture distribution.

It has been shown that whether the efficiency is based on relative variances of the maximum likelihood estimates (ML,E's) of the components of the vector of parameters or on the generalized variances of the MLE's of that vector, Hosmer's models Ml or M2 perform better than model MO.     

Multi-echelon supply chain network design in agile manufacturing

In this paper, we consider a supply chain network design problem in an agile manufacturing scenario with multiple echelons and multiple periods under a situation where multiple customers have heavy demands. Decisions in our supply chain design problem include selection of one or more companies in each echelon, production, inventory, and transportation. We formulate the problem integrating all decisions to minimize the total operational costs including fixed alliance costs between two companies, production, raw material holding, finished products holding, and transportation costs under production and transportation capacity limits. A Lagrangian heuristic is proposed in this paper. Optimizing a Lagrangian relaxation problem provides a lower bound, while a feasible solution is generated by adjustment techniques based on the solution of subproblems at each iteration. Computational results indicate the high quality solutions with less than 5% optimality gap are provided quickly by the approach in this paper. Further, compared to initiative managerial alternatives, an improvement of 15% to 25% is not unusual in certain cases for the proposed approach.