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Papers by Salah Elmaghraby

Research paper thumbnail of Composite mix design in the production of asbestos/cement pipes

Applied Mathematical Modelling, 1984

A mathematical model is presented for the determination of optimal mix of asbestos fibres to sati... more A mathematical model is presented for the determination of optimal mix of asbestos fibres to satisfy a set of desired pipe properties which vary with pipe size, class, and material availability. The approach utilizes a linear/separable programming model which is aimed at minimizing the total cost of fibres used. The fibre properties, such as reinforcing strength, processability, and length as well as cost and stocks available are taken into account in the model. Also represented are the profile of the ideal mix relative to the required composite strength, processability, and ‘dust content’. Asbestos mixes designed using the model have been implemented in the production of asbestos/cement pipes in one of the asbestos/cement pipe manufacturing plants in the Gulf area. Optimum model mixes have demonstrated significant technical and economic merits over the conventionally designed mixes.

Research paper thumbnail of Constraint Logic and Its Applications In Production: An Implementation Using the Galileo4 Language and System

Research paper thumbnail of DAGEN: A Generator of Testsets for Project Activity Nets; Working Paper

We offer a methodology, and the relevant software, to generate source-terminal directed project n... more We offer a methodology, and the relevant software, to generate source-terminal directed project nets of specified number of nodes, number of activities, complexity index, and ranges of costs and resources utilization.

Research paper thumbnail of Industrial diagnostic research: an approach

International Journal of Production Research, 1985

We refer to the process of uncovering the causes of failure in service of a manufactured item as ... more We refer to the process of uncovering the causes of failure in service of a manufactured item as ‘industrial diagnostic’. Based on our experience with such a problem over the past two years, we concluded that traditional approaches are inadequate, while the more modern approaches of ‘system failure diagnosis’ are tailored more towards the detection of failure in a complex piece of equipment than towards the detection of failure over the ‘life cycle’ of a product.In this paper we briefly review the traditional as well as the more modern theories of diagnosis, and expound on our approach to the problem. This approach contained both ‘field’ as well as ‘production plant’ research. The objective of the former was to determine the influence of the various factors on product degradation in service; while the objective of the latter was to determine the ‘significant plant parameters’ and to construct the ‘quality function’ (QF) of the producing plant.It is our contention that industrial diagnostics has received little attention from researchers in this field; that its methodology is in need of intensive as well as extensive development; and that the construction of the QF is of primary importance if quality is to be controlled and progressively enhanced in the manufacturing plants.

Research paper thumbnail of Some operations research approaches to automobile gear train design

We address the problem of the design of an automobile gear transmission to achieve optimal perfor... more We address the problem of the design of an automobile gear transmission to achieve optimal performance, where the latter is measured by the minimum time required to reach a prescribed final velocity. We apply two Operations Research methodologies, dynamic programming and parametric optimization, to two different vehicle characteristics. The results of the two approaches differ insignificantly between themselves on either

Research paper thumbnail of A Note on the "Explosion" and "Netting" Problems in the Planning of Materials Requirements

Operations Research, 1963

Research paper thumbnail of On Hyperbolic Programming with a Single Constraint and Upper-Bounded Variables

Research paper thumbnail of Handbook of Operations Research : foundations and fundamentals

Research paper thumbnail of Research Needs and Challenges in Application of Computer and Information Sciences for Industrial Engineering

Iie Transactions, 1989

By invitation from the Editor of IIE Transactions, a research forum was established in 1987 to de... more By invitation from the Editor of IIE Transactions, a research forum was established in 1987 to develop and prepare this article. The objective: to write on the directions, needs and challenges for research by the IE com-munity in applying computer and information sciences. The motivation: realizing the major advancements in computer and information sciences in the recent decade and their

Research paper thumbnail of Scheduling of a two-machine flowshop with availability constraints on the first machine

International Journal of Production Economics, 2006

We treat the problem of scheduling nn immediately available jobs in a flowshop composed of two ma... more We treat the problem of scheduling nn immediately available jobs in a flowshop composed of two machines in series with the objective of minimizing the makespan, when it is known that there shall be an interruption in machine availability on the first machine. We also consider two types of processing regimes: “stop resume” and “stop restart”. We present efficient dynamic program models for both regimes. But we focus on the performance of the Johnson rule as a heuristic. We establish the conditions under which it yields the optimum, and demonstrate that in other cases its performance is bounded by 2.

Research paper thumbnail of An Approach to Linear Programming under Uncertainty

Operations Research, 1959

Research paper thumbnail of Sensitivity Analysis of Multiterminal Flow Networks

Operations Research, 1964

Research paper thumbnail of The role of modelling in I.E. design

Research paper thumbnail of SCHEDULING HYBRID FLOWSHOPS IN PRINTED CIRCUIT BOARD ASSEMBLY LINES

Production and Operations Management, 2009

We treat a three-stage hybrid flowshop for the production of printed circuit boards (PCB), sugges... more We treat a three-stage hybrid flowshop for the production of printed circuit boards (PCB), suggested to us by a real-life production situation. The problem is to determine a schedule that minimizes the makespan for a given demand profile over a finite planning horizon. We propose a global procedure that utilizes genetic algorithms and three subproblems. The performance of the procedure is evaluated via experimentation over thousands of problem realizations that are randomly generated. The experimental results show the efficiency of the global procedure and provides qualitative answers to the allocation of machines to the various stages.

Research paper thumbnail of The Planning and Scheduling of Production Systems

Research paper thumbnail of Optimal project compression with due-dated events

Naval Research Logistics Quarterly, 1979

The paper proposes an algorithm for the determination of the solution of the activities to be sho... more The paper proposes an algorithm for the determination of the solution of the activities to be shortened and the amount by which they are to be shortened in order to minimize the total cost of project completion. This cost involves a linear penalty for tardienss of a set of key events and a linear cost of activity compression from its normal duration. The procedure is a generalization of the work of Fulkerson.

Research paper thumbnail of Optimal start times under stochastic activity durations

International Journal of Production Economics, 2000

We treat the problem of sequencing n activities on a single facility with the objective of determ... more We treat the problem of sequencing n activities on a single facility with the objective of determining their start times to maximize an economic gain, subject to restrictions on their availabilities. The activities possess random durations. We present a dynamic programming model that determines the optimal value and yields the desired start times, which also imply the optimal sequence. An approximation is also offered to lighten the computing burden somewhat.

Research paper thumbnail of Optimal Time-Cost Trade-Offs in GERT Networks

Research paper thumbnail of Knapsack-Based Approaches to the Makespan Problem on Multiple Processors

Iie Transactions, 1980

... Nichols, Bulfin and Parker [17] proposed a three-stage approach that starts with a heuristic,... more ... Nichols, Bulfin and Parker [17] proposed a three-stage approach that starts with a heuristic, followed by a man-machine interactive process to swap jobs ... Heuristics based on the longest processing times (LPT) ranking for all jobs were suggested by Kedia [14] and Greenberg [12 ...

Research paper thumbnail of The economic lot scheduling problem under power-of-two policy

Computers & Mathematics With Applications, 2001

We present further analysis on the economic lot scheduling problem (ELSP) without capacity constr... more We present further analysis on the economic lot scheduling problem (ELSP) without capacity constraints under power-of-two (PoT) policy. We explore its optimality structure and discover that the optimal objective value is piece-wise convex. By making use of the junction points of this function, we derive an effective (polynomial-time) search algorithm to secure a global optimal solution. The conclusions of this research lay the foundation for deriving an efficient heuristic, and also creates a benchmark for evaluating the quality of the heuristics for the conventional ELSP under PoT policy.

Research paper thumbnail of Composite mix design in the production of asbestos/cement pipes

Applied Mathematical Modelling, 1984

A mathematical model is presented for the determination of optimal mix of asbestos fibres to sati... more A mathematical model is presented for the determination of optimal mix of asbestos fibres to satisfy a set of desired pipe properties which vary with pipe size, class, and material availability. The approach utilizes a linear/separable programming model which is aimed at minimizing the total cost of fibres used. The fibre properties, such as reinforcing strength, processability, and length as well as cost and stocks available are taken into account in the model. Also represented are the profile of the ideal mix relative to the required composite strength, processability, and ‘dust content’. Asbestos mixes designed using the model have been implemented in the production of asbestos/cement pipes in one of the asbestos/cement pipe manufacturing plants in the Gulf area. Optimum model mixes have demonstrated significant technical and economic merits over the conventionally designed mixes.

Research paper thumbnail of Constraint Logic and Its Applications In Production: An Implementation Using the Galileo4 Language and System

Research paper thumbnail of DAGEN: A Generator of Testsets for Project Activity Nets; Working Paper

We offer a methodology, and the relevant software, to generate source-terminal directed project n... more We offer a methodology, and the relevant software, to generate source-terminal directed project nets of specified number of nodes, number of activities, complexity index, and ranges of costs and resources utilization.

Research paper thumbnail of Industrial diagnostic research: an approach

International Journal of Production Research, 1985

We refer to the process of uncovering the causes of failure in service of a manufactured item as ... more We refer to the process of uncovering the causes of failure in service of a manufactured item as ‘industrial diagnostic’. Based on our experience with such a problem over the past two years, we concluded that traditional approaches are inadequate, while the more modern approaches of ‘system failure diagnosis’ are tailored more towards the detection of failure in a complex piece of equipment than towards the detection of failure over the ‘life cycle’ of a product.In this paper we briefly review the traditional as well as the more modern theories of diagnosis, and expound on our approach to the problem. This approach contained both ‘field’ as well as ‘production plant’ research. The objective of the former was to determine the influence of the various factors on product degradation in service; while the objective of the latter was to determine the ‘significant plant parameters’ and to construct the ‘quality function’ (QF) of the producing plant.It is our contention that industrial diagnostics has received little attention from researchers in this field; that its methodology is in need of intensive as well as extensive development; and that the construction of the QF is of primary importance if quality is to be controlled and progressively enhanced in the manufacturing plants.

Research paper thumbnail of Some operations research approaches to automobile gear train design

We address the problem of the design of an automobile gear transmission to achieve optimal perfor... more We address the problem of the design of an automobile gear transmission to achieve optimal performance, where the latter is measured by the minimum time required to reach a prescribed final velocity. We apply two Operations Research methodologies, dynamic programming and parametric optimization, to two different vehicle characteristics. The results of the two approaches differ insignificantly between themselves on either

Research paper thumbnail of A Note on the "Explosion" and "Netting" Problems in the Planning of Materials Requirements

Operations Research, 1963

Research paper thumbnail of On Hyperbolic Programming with a Single Constraint and Upper-Bounded Variables

Research paper thumbnail of Handbook of Operations Research : foundations and fundamentals

Research paper thumbnail of Research Needs and Challenges in Application of Computer and Information Sciences for Industrial Engineering

Iie Transactions, 1989

By invitation from the Editor of IIE Transactions, a research forum was established in 1987 to de... more By invitation from the Editor of IIE Transactions, a research forum was established in 1987 to develop and prepare this article. The objective: to write on the directions, needs and challenges for research by the IE com-munity in applying computer and information sciences. The motivation: realizing the major advancements in computer and information sciences in the recent decade and their

Research paper thumbnail of Scheduling of a two-machine flowshop with availability constraints on the first machine

International Journal of Production Economics, 2006

We treat the problem of scheduling nn immediately available jobs in a flowshop composed of two ma... more We treat the problem of scheduling nn immediately available jobs in a flowshop composed of two machines in series with the objective of minimizing the makespan, when it is known that there shall be an interruption in machine availability on the first machine. We also consider two types of processing regimes: “stop resume” and “stop restart”. We present efficient dynamic program models for both regimes. But we focus on the performance of the Johnson rule as a heuristic. We establish the conditions under which it yields the optimum, and demonstrate that in other cases its performance is bounded by 2.

Research paper thumbnail of An Approach to Linear Programming under Uncertainty

Operations Research, 1959

Research paper thumbnail of Sensitivity Analysis of Multiterminal Flow Networks

Operations Research, 1964

Research paper thumbnail of The role of modelling in I.E. design

Research paper thumbnail of SCHEDULING HYBRID FLOWSHOPS IN PRINTED CIRCUIT BOARD ASSEMBLY LINES

Production and Operations Management, 2009

We treat a three-stage hybrid flowshop for the production of printed circuit boards (PCB), sugges... more We treat a three-stage hybrid flowshop for the production of printed circuit boards (PCB), suggested to us by a real-life production situation. The problem is to determine a schedule that minimizes the makespan for a given demand profile over a finite planning horizon. We propose a global procedure that utilizes genetic algorithms and three subproblems. The performance of the procedure is evaluated via experimentation over thousands of problem realizations that are randomly generated. The experimental results show the efficiency of the global procedure and provides qualitative answers to the allocation of machines to the various stages.

Research paper thumbnail of The Planning and Scheduling of Production Systems

Research paper thumbnail of Optimal project compression with due-dated events

Naval Research Logistics Quarterly, 1979

The paper proposes an algorithm for the determination of the solution of the activities to be sho... more The paper proposes an algorithm for the determination of the solution of the activities to be shortened and the amount by which they are to be shortened in order to minimize the total cost of project completion. This cost involves a linear penalty for tardienss of a set of key events and a linear cost of activity compression from its normal duration. The procedure is a generalization of the work of Fulkerson.

Research paper thumbnail of Optimal start times under stochastic activity durations

International Journal of Production Economics, 2000

We treat the problem of sequencing n activities on a single facility with the objective of determ... more We treat the problem of sequencing n activities on a single facility with the objective of determining their start times to maximize an economic gain, subject to restrictions on their availabilities. The activities possess random durations. We present a dynamic programming model that determines the optimal value and yields the desired start times, which also imply the optimal sequence. An approximation is also offered to lighten the computing burden somewhat.

Research paper thumbnail of Optimal Time-Cost Trade-Offs in GERT Networks

Research paper thumbnail of Knapsack-Based Approaches to the Makespan Problem on Multiple Processors

Iie Transactions, 1980

... Nichols, Bulfin and Parker [17] proposed a three-stage approach that starts with a heuristic,... more ... Nichols, Bulfin and Parker [17] proposed a three-stage approach that starts with a heuristic, followed by a man-machine interactive process to swap jobs ... Heuristics based on the longest processing times (LPT) ranking for all jobs were suggested by Kedia [14] and Greenberg [12 ...

Research paper thumbnail of The economic lot scheduling problem under power-of-two policy

Computers & Mathematics With Applications, 2001

We present further analysis on the economic lot scheduling problem (ELSP) without capacity constr... more We present further analysis on the economic lot scheduling problem (ELSP) without capacity constraints under power-of-two (PoT) policy. We explore its optimality structure and discover that the optimal objective value is piece-wise convex. By making use of the junction points of this function, we derive an effective (polynomial-time) search algorithm to secure a global optimal solution. The conclusions of this research lay the foundation for deriving an efficient heuristic, and also creates a benchmark for evaluating the quality of the heuristics for the conventional ELSP under PoT policy.