# Hesham AlfaresKing Fahd University of Petroleum and Minerals | KFUPM · Department of Systems Engineering

Hesham Alfares

Doctor of Philosophy

## About

93

Publications

56,797

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2,157

Citations

Citations since 2016

Introduction

**Skills and Expertise**

## Publications

Publications (93)

An important and challenging real-life problem is considered, involving workforce assignment and job scheduling for shutdown maintenance in a large oil refinery. A limited number of maintenance employees must be divided into several teams that work in parallel on different maintenance tasks. The objective is to minimize the shutdown cost by minimiz...

The classical economic production quantity model is formulated based on several simplifying assumptions such as constant demand rate, constant holding cost, constant setup cost, and constant production cost. However, these assumptions do not always represent the reality. Therefore, a generalized production-inventory control model is developed in th...

Determining staffing requirements for a fire station is quite difficult as one must balance the cost of additional human resources and the risk of not having an effective force to respond to a given incident. This paper presents an application of a new AHP-based method, incorporating multiple decision-makers and multiple decisions, to fire station...

This paper presents models and solution algorithms for a two-machine scheduling problem with position-dependent job processing times subject to both aging and maintenance effects. Aiming to minimize the overall makespan for two identical parallel machines, two cases are analyzed. In the first case, no maintenance is scheduled. In the second case, m...

Inventory models of growing items are used when the stored items (such as poultry, fish, and livestock) have the capability to grow during the inventory replenishment cycle. This paper extends inventory models for growing items by considering quality aspects, permissible shortages with complete backordering, and holding cost during both the growth...

This paper presents an integer linear programming model to optimize portfolio investment in the stock market for maximizing expected return. The model considers risk tolerance, expected dividends, and limits on both the capital investment and the number of stocks for each company. As a new feature, the model ensures that the companies whose shares...

Inventory control is relatively difficult when the product is perishable, the demand is stochastic, the product life cycle is short, and the pricing policy is dynamic. Several prior studies utilized simulation approaches to deal with the high complexity, stochastic, and multi-factor nature of this problem. However, most previous studies considered...

This paper extends inventory models for growing items by considering quality inspections, permissible shortages with complete backordering, and holding cost during both the growth period and the consumption period. By backordering shortages, the firm can avoid the loss of sales by paying delay penalties to customers who wait for late items. After i...

A novel technique is proposed to optimize energy efficiency for wireless networks based on hierarchical mobile clustering. The new bi-level clustering technique minimizes mutual interference and energy consumption in large-scale tracking systems used in large public gatherings such as festivals and sports events. This technique tracks random moveme...

A new technique is presented to design energy-efficient large-scale tracking systems based on mobile clustering. The new technique optimizes the formation of mobile clusters to minimize energy consumption in large-scale tracking systems. This technique can be used in large public gatherings with high crowd density and continuous mobility. Utilizing...

This article presents a new model and an efficient solution algorithm for a bi-objective one-dimensional cutting-stock problem. In the cutting-stock—or trim-loss—problem, customer orders of different smaller item sizes are satisfied by cutting a number of larger standard-size objects. After cutting larger objects to satisfy orders for smaller items...

This article presents a two-stage workforce scheduling approach for security guards at motor traffic gates. In the first stage, staffing requirements are determined based on analyzing workload variations for each gate. In the second stage, an integer programming model is formulated to assign guards to different work shifts in order to satisfy the s...

A novel technique is proposed to optimize energy efficiency for wireless networks based on hierarchical mobile clustering. The new bi-level clustering technique minimizes mutual interference and energy consumption in large-scale tracking systems used in large public gatherings such as festivals and sports events. This technique tracks random moveme...

A new technique is presented to design energy-efficient large-scale tracking systems based on mobile clustering. The new technique optimizes the formation of mobile clusters to minimize energy consumption in large-scale tracking systems. This technique can be used in large public gatherings with high crowd density and continuous mobility. Utilizing...

This chapter discusses the application of linear programming (LP) techniques to find the optimal solution of the economic dispatch (ED) problem without considering transmission losses. The ED problem is concerned with optimizing the power generated by several generating units. The objective is to find the optimal power produced by each unit to supp...

In production-inventory control, economic order quantity (EOQ) and economic production quantity (EPQ) models are used to determine the optimal order quantities for purchasing and manufacturing. Most EOQ and EPQ models are constructed assuming constant costs. Recently, however, EOQ/EPQ models assuming varying costs (i.e. holding, ordering, and purch...

A general model is presented for a realistic multi-item lot-sizing problem with multiple suppliers, multiple time periods, quantity discounts, and backordering of shortages. Mixed integer programming (MIP) is used to formulate the problem and obtain the optimum solution for smaller problems. Due to the large number of variables and constraints, the...

This paper considers the integration between quality control and production inventory control in supply chain management. Specifically, we study the effect of inspection errors on the costs incurred in a supply chain system with a single vendor and multiple buyers. In this system, the vendor enters into a vendor-managed inventory (VMI) and a consig...

This paper presents a new model and an efficient solution algorithm for a bi-objective one-dimensional trim-loss problem. In the trim-loss-or cutting-stock-problem, customer orders of different smaller item sizes are satisfied by cutting a number of larger standard-size objects. After cutting larger objects to satisfy orders for smaller items, the...

Lot-sizing is a very important problem in production and inventory planning under variable demand. In this work, a general model is proposed for a single-item lot-sizing problem with multiple suppliers, quantity discounts, and backordering of shortages. Mixed integer programming (MIP) is used to formulate the problem and obtain the optimum solution...

A multi-period production and inventory control problem for a multi-grade, multi-supplier petrochemical product is formulated and optimally solved. Raw materials are available from several suppliers, and several plants (chemical reactors) are used for making the petrochemical product. Several grades of the petrochemical product can be produced by c...

In typical EOQ-based inventory models, the demand rate and the holding cost are assumed to have constant values and the unit purchase cost is assumed constant regardless of the order size. In actual applications, however, the demand rate for a specific item can be affected by many variables such as seasonality, selling price, and availability. More...

This paper presents an optimum solution of the economic dispatch (ED) problem without considering transmission losses using linear programming (LP). In the ED problem, several on-line units (generators) are available, and it is needed to determine the power to produce by each unit in order to meet the required load at minimum total cost. To apply L...

This paper presents a simulation study to assess the performance of the five known methods for converting ranks of several criteria into weights in multi-criteria decision-making. The five methods assessed for converting criteria ranks into weights are: rank- sum (RS) weights, rank reciprocal (RR) weights, rank order centroid (ROC) weights, geometr...

A new production-planning model with a unique set of realistic features is considered. First, the demand rate is a function of the current inventory level. Second, a new order is gradually produced according to a finite production rate. Third, the unit holding cost per time period is a function of both the unit purchase cost and the storage time du...

A new production-inventory planning model is considered, in which the holding cost is variable and the purchase cost is subject to quantity discounts. The new production-inventory planning model has three important and realistic features. First, the production rate is finite, so the whole order is not received in one instant, but is gradually produ...

Maintenance capacity planning deals with the determination of the required resources to perform the needed maintenance tasks at a high standard of quality. The resources include labor, equipment and tools, but the most important maintenance resource is labor. Therefore, the focus in this paper is on the determination of craft mix and the sources of...

An integer programming model and optimal solution procedure are presented for assigning employees to the (10, 14) days-off schedule. This schedule is used by a large oil company to schedule employees in remote work locations. The primary objective is to minimize the total number of employees. Since employees are flown to their remote work sites, th...

In general, traditional production-inventory systems are based on a number of simplifying
– but somewhat unrealistic – assumptions, including constant demand rate, constant holding
cost, and instantaneous order replenishment. These assumptions have been individually
challenged in numerous variations of production-inventory models. Finite production...

A comparative analysis is presented of community service activities in Saudi Arabian Universities. The methodology includes literature surveys, benchmarking, questionnaires, and focus group meetings. Community service definitions and activities are surveyed around the world. A benchmarking comparison is made between community service programs in 10...

An Integer Programming (IP) model is formulated and optimally solved for a real-life production planning problem. The model is used to determine the optimum production plan for the formation stage of battery manufacturing in a local battery-producing company. Battery manufacturing is a complicated process that involves several stages and several ch...

This paper describes Patent Number U.S. 8,046,316 B2, titled "Cyclic Combinatorial Method and System", issued by the US Patents and Trademarks Office on October 25, 2011. The patent is based on a combinatorial algorithm to solve cyclic optimization problems. First, the algorithm identifies cyclically distinct solutions of such problems by enumerati...

Instantaneous order replenishment and constant holding cost are two fundamental assumptions of the economic order quantity (EOQ) model. This paper presents modifications to both of these basic assumptions. First, non-instantaneous order replenishment is assumed, i.e. a finite production rate of the economic production quantity (EPQ) model is consid...

This paper presents an integer programming (IP) model for production planning, which is used to maximize the profitability of battery manufacturing in a mid-size company. Battery production is a complicated multi-stage process. The formation stage, during which the batteries are filled with acid and charged with electricity, is considered to be the...

In this paper, an efficient particle swarm optimization (PSO) methodology is presented for solving workforce job rotation scheduling problem. The workforce job rotation problem is concerned with assigning and sequencing a set of tasks of varying levels of occupational hazards or physical demands among several employees. Rotating tasks assures fairn...

This paper presents an integer programming (IP) model for production planning, which is used to maximize the profitability of battery manufacturing in a mid-size company. Battery production is a complicated multi-stage process. The formation stage, during which the batteries are filled with acid and charged with electricity, is considered to be the...

In this paper, a systematic methodology is proposed for developing an outcome-based undergraduate Industrial and Systems Engineering Program at the Systems Engineering Department of King Fahd University of Petroleum & Minerals (KFUPM) in Saudi Arabia. This program is an upgrade of the Industrial Engineering and Operations Research (IE/OR) option, w...

In this paper, the problem of determining the optimum number and locations of banking automatic teller machines (ATMs) is considered. The objective is to minimize the total number of ATMs to cover all customer demands within a given geographical area. First, a mathematical model of this optimization problem is formulated. A novel heuristic algorith...

A simulation model is used for stochastic days-off scheduling of maintenance crews. In order to determine optimum employee work schedules, the model considers limited employee availability, stochastic workload demand, and labor scheduling regulations. The stochastic simulation model was implemented for actual days-off scheduling of a multi-craft pi...

The modeling and solution is presented for a real-life operator scheduling problem at a call center. Queuing and integer programming models are combined to minimize the total weekly labor cost while providing an acceptable service level for each hour of each day of the week. The models determine optimum staffing levels and employee weekly work sche...

Q1 Please check the accuracy of this reference -it seems to be missing several co-authors. In addition, please provide the publisher details (name and location) for the proceedings and the page range of this article. Q2 Please provide the publisher details (name and location) for the proceedings. A mixed-integer linear programming model is presente...

Carrying out an effective maintenance operation requires efficient planning of maintenance activities and resources. Since planning is performed in order to prepare for future maintenance tasks, it must be based on good estimates of the future maintenance workload. The maintenance workload consists of two major components: (1) scheduled and planned...

In this paper, we present an empirical methodology to determine aggregate numerical criteria weights from group ordinal ranks of multiple decision criteria. Assuming that such ordinal ranks are obtained from several decision makers, aggregation procedures are proposed to combine individual rank inputs into group criteria weights. In this process, w...

A methodology is proposed to convert ordinal ranking of a number of criteria into numerical weights. Specifically, a simple mathematical expression is developed to provide the weight for each criterion as function of its rank and the total number of criteria. The proposed methodology is empirically developed, evaluated, and validated based on a set...

Locating public services for nomadic population groups is a difficult challenge as the locations of the targeted populations seasonally change. In this paper, the population groups are assumed to occupy different locations according to the time of the year, i.e., winter and summer. A binary integer programming model is formulated to determine the o...

An empirical methodology is presented to determine aggregate numerical weights from group ordinal ranks of multiple decision criteria. Assuming such ordinal rankings are obtained from several decision makers, aggregation procedures are proposed to combine individual rank inputs into group weights. In developing this methodology, we utilize empirica...

This paper presents a dynamic programming (DP) algorithm for solving a labor scheduling problem with several realistic days-off
scheduling constraints and a cost structure that depends on the work sequence for each employee. The days-off scheduling constraints
include the following: (1) each employee is assigned no more than three workdays per week...

Inventory models in which the demand rate depends on the inventory level are based on the common real-life observation that greater product availability tends to stimulate more sales. Previous models incorporating inventory-level dependent demand rate assume that the holding cost is constant for the entire inventory cycle. This paper considers the...

A mixed integer programming model is presented for the optimum planning of multi-grade, multi-plant petrochemical production. When producing several grades of a given petrochemical product in the same reactor, the amount of transitional off-spec production depends on the sequencing of different grades. The model determines the optimum mix of petroc...

This paper describes the staffing and scheduling of IT help desk operators for a large petrochemical company. The objective is to reduce the labour cost by determining the best staffing level and employee weekly tour schedules required to meet the workload that varies over a 24-hr operating period. Several steps are taken for the staffing and tour...

This paper presents a simulation approach for employee days-off scheduling when the daily labour demands are random variables. A simulation model is constructed, and a case study application of the proposed approach is described. The model recognizes limited staff availability, stochastic workload variability, and policy restrictions on the choice...

This paper describes the optimization of maintenance workforce scheduling at Afam power station in Nigeria. The objective is to determine the optimum schedule to satisfy growing maintenance labour requirements with minimum cost and highest efficiency. Three alternative maintenance workforce schedules are compared. The first alternative is to contin...

This paper presents a simulation approach for employee days-off scheduling when the daily labour demands are random variables. A simulation model is constructed, and a case study application of the proposed approach is described. The model recognizes limited staff availability, stochastic workload variability, and policy restrictions on the choice...

This paper presents a three-day workweek scheduling problem with four types of days-off scheduling constraints: (1) out of the four off days given to each employee per week, at least two must be consecutive, (2) two alternative types of constraints are imposed to ensure that employees get a sufficient proportion of weekends off, (3) the maximum wor...

Interaction between the University and both the Industry and Business is of paramount importance in enhancing learning, research, and the mutual relationship with the society. This interaction needs to occur across the broad spectrum of industries and businesses and should not be restricted to major industry sectors. Venues of interaction and coope...

In typical production-inventory models of deteriorating items, deterioration of the production process has not been considered. In this paper, a model is pro-posed in which both the produced items and the production equipment deteriorate. When the production system deteriorates, it shifts to an out-of-control state and begins to produce a proportio...

In the classical newsboy problem, no cost is assumed if the ordered quantity is less than the demand. However, in reality failure to meet demand is always associated with a penalty. The aim of this work is to extend the analysis of the distribution-free newsboy problem to the case when shortage cost is taken into consideration. The analysis is base...

This paper reports the results of a workforce staffing and scheduling project accomplished at the IT Help Desk of a large local company. The objective is to reduce the labor cost by determining the best staffing level and employee weekly schedules required to meet the demand that varies over a 24-hours operating period. Extensive data is collected...

In this paper we consider a three-day workweek scheduling problem with three realistic days-off scheduling constraints: (1) at least two off days per week must be consecutive, (2), employees must get a given proportion of weekends off, and (3) the number of consecutive workdays in any work stretch cannot exceed four. An integer programming model is...

The problem of assigning weights from ordinal ranks appears in many contexts in multi-criteria decision making. In this paper, we present an empirical methodology for converting an ordinal ranking of a number of criteria into numerical weights. Based on this methodology, the weight for each criterion is expressed as a simple mathematical function o...

The employee tour scheduling problem involves the determination of both work hours of the day and workdays of the week for each employee. This problem has proven difficult to solve optimally due to its large size and pure integer nature. During the last decade, numerous approaches for modeling and solving this problem have been proposed. In this pa...

This work deals with the analysis of production and inventory control systems using the Z-transform approach. This methodology offers well developed and powerful analysis techniques that could be utilized to minimize the inventory drift, i.e., the difference between the actual and the desired inventory levels. Control tools such as stability tests,...

A simulation-based methodology is presented for employee days-off scheduling subject to stochastic daily labor demands, and a real-life implementation of this methodology is described. This methodology has been applied in the days-off scheduling of a multi-craft maintenance workforce of an oil and gas pipelines department, which belongs to a large...

The objective of this paper is to develop optimum solutions for the labor scheduling problem in which workers are given three or four consecutive workdays per week. These solutions apply to the special cases in which labor demand has two different levels: D for weekdays and E for weekends. They do not include linear or integer programming, and do n...

A four-day workweek days-off scheduling problem is considered. Out of the three days off per week for each employee, either two or three days must be consecutive. An optimization algorithm is presented which starts by utilizing the problem's special structure to determine the minimum workforce size. Subsequently, workers are assigned to different d...

A new integer programming model and a two-stage solution method are presented for the flexible 4-day workweek days-off scheduling problem with weekend work frequency constraints. In this problem, employees are given 3 days off per week, out of which either 2 or 3 must be consecutive. Two alternative constraints are imposed to ensure that employees...

A new combinatorial algorithm is presented, which has potential applications in cyclic scheduling. Specifically, the question is: given n cyclic objects, how many cyclically distinct combinations of m (m ≤ n) objects can be selected? In other words, if a subset m of these objects has one color, and the remaining (n – m) objects have another color,...

A new mixed integer linear programming model is formulated and used to model the development of the petrochemical industry in Saudi Arabia. The proposed model features a new mathematical programming formulation, new products and processes, new variables and constraints, and more accurate estimates of production costs based on local conditions. The...

A mixed integer linear programming model is formulated for determining the optimum plan for the expansion of the Saudi Arabian petrochemical industry. The products selected for consideration fall into four categories: propylene derivatives, ethylene derivatives, synthesis gas derivatives, and aromatic derivatives. The model incorporates new variabl...

An efficient optimum solution is presented for a real-life employee day-soff scheduling problem with a three-week cycle. Over a given work cycle, each worker is given 14 successive workdays and 7 successive off days. This three-week days-off timetable is referred to as the (14, 21) schedule. Given different labor demands for each day of the week, t...

Using simulation, optimum preventive maintenance (PM) schedules are developed for the major components of a detergent-packing line. For each component, two PM policies are considered. In the first policy, the interval between any two successive PM inspections is constant and unaffected by failures between inspections. In the second policy, the PM i...

A review and categorization of electric load forecasting techniques is presented. A wide range of methodologies and models for forecasting are given in the literature. These techniques are classified here into nine categories: (1) multiple regression, (2) exponential smoothing, (3) iterative reweighted least-squares, (4) adaptive load forecasting,...

A new mixed integer linear programming model is formulated for the optimum utilization of ethylene derivatives in the Saudi Arabian petrochemical industry. The model incorporates new variables and constraints, and accurate estimates of production costs, which are calculated based on local conditions in Saudi Arabia. The input data for each ethylene...

An efficient method is presented for the optimum solution of the cyclic manpower days-off scheduling problem. This method,
which is based on linear programming, allows unequal costs to be considered for different days-off patterns. First, the solution
of the dual linear programming model is used to determine the minimum workforce size. Then, a proc...

An actual workforce scheduling study at an industrial security gate is presented. The objectives are to determine the gate's most appropriate staffing levels and optimum employee schedules. The gate's staffing requirements at different times of the day on workdays and weekends are determined based on the number of open lanes, the amount of traffic,...

An optimization method is presented for the cyclic labour days-off scheduling problem, in which workers are given three consecutive days off per week. This method does not include linear or integer programming, and it does not assume that the costs of different days-off work patterns are equal. The dual problem is first solved to determine the mini...

An optimization method is presented for the cyclic labour days-off scheduling problem, in which workers are given three consecutive days off per week. This method does not include linear or integer programming, and it does not assume that the costs of different days-off work patterns are equal. The dual problem is first solved to determine the mini...

An optimum solution is developed for an actual employee days-off scheduling problem with a three-week cycle. Over a given work cycle, the workdays/off-days pattern is referred to as the 7/3–7/4 schedule. Given varying labor demands for each day of the week, the first objective is to minimize the workforce size. The second objective is to minimize t...

An efficient heuristic technique is developed for a real-life labor days-off scheduling problem with a four-week cycle. Using a workdays/off-days notation, this days-off arrangement is referred to as the (7/3, 7/3, 6/2) schedule. Given two different levels of labor demands, D for weekdays and E for weekends, the primary objective is to minimize the...

K eyw ords project scheduling, personnel scheduling, integer programming, project management A bstract. The main theme of this paper is improving project schedules by integrating the scheduling of project jobs and labour resources. An ILP model is presented of the integrated project operations and personnel scheduling problem with mul-tiple labour...

Frequent inspections of relief valves are necessary to ensure safety. However, inspections are costly and potentially destructive. A delicate balance between safety and cost must be obtained. This is a very complex problem, involving multiple factors that include valve pressure, temperature, medium, age, size and type. This paper presents a simulat...

This paper describes an actual aircraft maintenance labor scheduling study. The study’s objective is to determine the optimum maintenance workforce schedule to satisfy growing labor requirements with minimum cost. The main recommendation of the study is to switch from a five-day to a seven-day workweek for aircraft maintenance workers. A new intege...

Providing the best service in order to satisfy users is the main objective of any library. The loan policy is a major tool available to achieve this objective. Previous studies have all focused on the loan period, ignoring the loan policy's other equally important aspect, which is the maximum number of books a user can borrow. Moreover, only book a...

Workforce scheduling is a very important and practical problem, especially in service industries. The days-off scheduling problem arises in organizations that operate 7 days a week. Since workers must be given weekly breaks, they are assigned to different days-off shifts (work patterns). The objective is to satisfy daily labor demands with a minimu...

The objective of project task scheduling is to determine task start dates and durations to complete a project on time with the minimum cost of performing tasks plus overhead. By altering task start dates and durations, the daily labor-demand profile can be changed. The objective of personnel scheduling is to determine how many workers must be assig...

This paper extends the work done by Alfares (1994) for the 5-day workweek (5, 7) problem, to the 3-day work week or the (3, 7) problem. It assumes that each employee is given 3 work days and 4 consecutive days off per week. A manual, yet optimum solution method is presented. To find the optimum primal solution, the method utilizes the easily obtain...

The objective of project scheduling is to determine start dates and the labor resources assigned to each activity in order to complete a project on time. By moving start dates within available slack times and altering labor levels, the daily labor-demand profile can be changed. The objective of personnel scheduling is to determine how many of each...

The scheduling of project activities and manpower, traditionally performed in 2 separate stages, is combined into in a single scheduling problem. An integer LP formulation of the integrated problem is presented. Then, a DP-based heuristic algorithm is introduced. Near-optimal efficient solutions are obtained, significantly outperfoming 2-stage solu...