An integer programming based algorithm for the resource constrained project scheduling problem

Ankara : The Department of Industrial Engineering and the Institute of Engineering and Sciences of Bilkent Univ., 2005.Thesis (Master's) -- Bilkent University, 2005.Includes bibliographical references leaves 48-54.In this thesis, we study the problem of scheduling the activities of a single project in order for all resource and precedence relationships constraints to be satisfied with an objective of minimizing the project completion time. To solve this problem, we propose an Integer Programming based approximation algorithm, which has two phases. In the first phase of the algorithm, a subproblem generation technique and enumerative cuts used to tighten the formulation of the problem are presented. If an optimal solution is not found within a predetermined time limit, we continue with the second phase that uses the cuts and the lower bound obtained in the first phase. In order to evaluate the efficiency of our algorithm, we used the benchmark instances in the literature and compared the results with the best known solutions available for these instances. Finally, the computational results are reported and discussed.Büyüktahtakın, İsmet EsraM.S

Assessment of Activities’ Criticality to Cash-Flow Parameters

Cash flow modeling is a very useful financial management tool that contractors use to run a sustained business. Contractors manage multiple activities within a single project. The activities’ start times are the inherent variables which determine the values of periodical negative cumulative balances and the other cash-flow parameters of cash flow model. Since the start times of activities vary while the dependency is maintained, in any given schedule the maximum value of the negative cumulative balance varies, as do the values of the other cash-flow parameters. This work reveals a system that can identify those activities that have the most influence on cash flow. The Monte Carlo Simulation technique has been employed here to generate schedules and their associated cash flow models for a case study by randomly specifying the activities’ start times between their respective early and late start times. Uniform discrete probability distributions are assumed for the activities’ start times, with the minimum and maximum values representing the early and late start times, respectively. In addition to the randomness of the activities’ start times, the simulation model considered the stochastic nature of the periodic cash in and cash out transactions in the cash flow model by adjusting their values to account for the impact of 43 qualitative factors identified in an earlier study. The @RISK commercial software was used to implement the simulation of the cash flow model built in an MS-Excel environment. Upon completing the specified number of runs, @RISK displays the probability distributions for the cash-flow parameters including the financing costs, maximum negative cumulative balance, project duration, and project profit. In addition, three scenarios are defined; each incorporating a different number of qualitative factors which impact the project cash inflow and cash outflow transactions. Scenario I incorporates none, Scenario II incorporates six factors impacting cash inflow transactions and nine factors impacting cash out flow transactions, and scenario III incorporates all of the qualitative factors that impact cash inflow and cash outflow transactions. Moreover, the ranges of the activities’ start times have been extended by supplementing the total floats with extension increments for the three scenarios. The results are presented and analyzed based on the three scenarios. The activities’ criticality to cash-flow parameters is assessed by evaluating the number of times a given activity determined a particular cash-flow parameter over the number of runs. This criticality measurement offers project managers very useful criteria with which to identify the activities that are most urgent to be completed on time

Scheduling with tool changes to minimize total completion time

Ankara : Department of Industrial Engineering and Institute of Engineerin and Sciences, Bilkent Univ., 1998.Thesis (Master's) -- Bilkent University, 1998.Includes bibliographical references leaves 87-90.In the literature, scheduling models do not consider the unavailability of tools. The tool management literature separately considers tool loading problem when tool changes are due to part mix. However in manufacturing settings tools are changed more often due to tool wear. In this research, the problem of scheduling a set of jobs to minimize total completion time on a single CNC machine is considered where the cutting tool is subject to wear. We show that this problem is NP-hard in the strong sense. We discuss the behavior of SPT heuristic and show that its worst case performance ratio is bounded above by a constant. A pseudo-polynomial dynamic programming formulation is provided to solve the problem optimally. Furthermore, heuristic algorithms are developed including dispatching heuristics and local search algorithms. It is observed that the performance of SPT rule gets worse as the tool change time increases and tool life decreases. The best improvement over the SPT rule’s performance is achieved by the proposed genetic algorithm with problem space search.Güneş, Evrim DidemM.S

Prioritätsregelbasierte Ressourcenplanung für Projekte mit komplexer Ablaufstruktur

In nahezu allen mittleren bis großen Unternehmen werden Projekte zur Lösung komplexer, teils interdisziplinärer Probleme durchgeführt . Man kann durchaus sagen, daß sich das Projektmanagement mittlerweile als Organisationsform neben der hierarchischen Struktur eines Unternehmens etabliert hat. Häufig wird es dabei zur Lösung von Aufgaben verwendet, welche einen hohen Grad an Neuartigkeit und Komplexität aufweisen, da traditionelle Linienorganisationen eher auf langfristige Zielsetzungen und Aufgaben ausgerichtet sind. Solche im Rahmen eines Projekts behandelten Probleme können in der Regel nicht intuitiv gelöst werden. Sie bedürfen einer systematischen Planung, um das Risiko von Fehlentscheidungen zu verringern. Das Projektmanagement bietet Methoden und Verfahren zur Organisation, Planung, Überwachung und Steuerung eines solchen Projekts . Die Verwendung von Methoden des Projektmanagements ist heute eine der wesentlichen Voraussetzungen, Effizienz und Innovationsfähigkeit von Unternehmen zu steigern, um sich im internationalen Wettbewerb zu behaupten. Durch den Einsatz von Projektplanungsmethoden können durchschnittlich Einsparungen in Höhe von etwa 15 erzielt werden . Dem steht ein durchschnittlicher Anteil der Planungskosten an den Projektkosten von circa 0,1 - 4 gegenüber. Probleme der Ablaufplanung sind daher seit mehreren Jahrzehnten verstärkt auch in der theoretischen Betrachtung im Rahmen des Operations Research häufig behandelte Themen. Diese Arbeit betrachtet die Planung eines Vorhabens mit komplexer Ablaufstruktur für den Fall, daß die Einzelvorgänge des Projekts in verschiedenen Durchführungsmodi ausgeführt werden können und die zur Durchführung des Vorhabens benötigten Ressourcen nur begrenzt zur Verfügung stehen. Zur Lösung des betrachteten Ressourcenplanungsproblems für diese Planungssituation stehen noch keine geeigneten Algorithmen zur Verfügun