Approximate Algorithms for the Combined arrival-Departure Aircraft Sequencing and Reactive Scheduling Problems on Multiple Runways

The problem addressed in this dissertation is the Aircraft Sequencing Problem (ASP) in which a schedule must be developed to determine the assignment of each aircraft to a runway, the appropriate sequence of aircraft on each runway, and their departing or landing times. The dissertation examines the ASP over multiple runways, under mixed mode operations with the objective of minimizing the total weighted tardiness of aircraft landings and departures simultaneously. To prevent the dangers associated with wake-vortex effects, separation times enforced by Aviation Administrations (e.g., FAA) are considered, adding another level of complexity given that such times are sequence-dependent. Due to the problem being NP-hard, it is computationally difficult to solve large scale instances in a reasonable amount of time. Therefore, three greedy algorithms, namely the Adapted Apparent Tardiness Cost with Separation and Ready Times (AATCSR), the Earliest Ready Time (ERT) and the Fast Priority Index (FPI) are proposed. Moreover, metaheuristics including Simulated Annealing (SA) and the Metaheuristic for Randomized Priority Search (Meta-RaPS) are introduced to improve solutions initially constructed by the proposed greedy algorithms. The performance (solution quality and computational time) of the various algorithms is compared to the optimal solutions and to each other. The dissertation also addresses the Aircraft Reactive Scheduling Problem (ARSP) as air traffic systems frequently encounter various disruptions due to unexpected events such as inclement weather, aircraft failures or personnel shortages rendering the initial plan suboptimal or even obsolete in some cases. This research considers disruptions including the arrival of new aircraft, flight cancellations and aircraft delays. ARSP is formulated as a multi-objective optimization problem in which both the schedule\u27s quality and stability are of interest. The objectives consist of the total weighted start times (solution quality), total weighted start time deviation, and total weighted runway deviation (instability measures). Repair and complete regeneration approximate algorithms are developed for each type of disruptive events. The algorithms are tested against difficult benchmark problems and the solutions are compared to optimal solutions in terms of solution quality, schedule stability and computational time

Factors Affecting Selection of Elective Courses: The Use of Multi-Criteria Decision Making Model

Elective course selection has always been a serious and important decision making process for students in institutions.  The study of Multi Criteria Decision Making Model (MCDM) for the selection of elective course is put together with the aim of lending a helping hand to the students. It comprises the main MCDM methods, the problem of selecting an elective course, the survey about the problem, the method which is selected to be implemented, the implementation and the results. In this study, we determine the criteria of this problem for graduate students while deciding on the elective courses. A total of 13 different criteria have been established, including 5 main criteria. In this direction, a questionnaire study was conducted as required by the multi-criteria decision-making analysis method decided in the light of the examined articles. This survey study was answered by graduate students. The responses were evaluated by the "Super Decisions" program and priorities were determined using the Analytic Hierarchy Process (AHP). The survey was applied to graduate students, and it was found that the two most important criteria of the graduate students were 28.03% of the curriculum and 20.42% of the faculty members. This study aims to prove a mathematical method for a real-life situation which can help people make their decisions accurately. It will help students who are indecisive and hesitates while selecting an elective course

Heuristics and Simulated Annealing Algorithm for the Surgical Scheduling Problem

HANCERLIOGULLARI KOKSALMIS, GULSAH/0000-0002-2551-541XWOS: 000371920400013Planning and scheduling play a very important role in health care. Effective scheduling optimizes the utilization of scarce resources such as operating rooms (ORs), devices in hospitals, and surgeons. Therefore, operations research/operations management techniques have been frequently used in health care systems management. In this chapter, we examine the surgical scheduling problem over multiple operating rooms. In order to find an optimal solution to surgical scheduling problem, mixed-integer programming (MIP) formulation of the surgical scheduling problem is presented. The model includes constraints for several operational rules and requirements found in most hospitals, and specifically minimizes the total weighted start time as a performance measure (or objective function). Since the problem is known to be an NP-hard in most of its forms, heuristic algorithms (i.e., greedy heuristics and a metaheuristic) are also introduced to find near-optimal solutions efficiently

Operations Management Perspectives in the Air Transport Management

The area of operations management has had a substantial effect on the today’s air transportation management. Having moved with huge demand from management to obtain a competitive advantage in the market, the airlines are utilizing advanced optimization techniques to develop decision support systems for operations management and control. In order to provide a service with high quality and low cost, airlines spend a tremendous amount of resources and effort to generate profitable and cost-effective fare classes, flight schedules, fleet plans, aircraft routes, crew scheduling, gate assignment, etc. In this paper, the techniques and operations management applications that are used in the air transportation industry are reviewed including demand forecasting, fleet assignment, aircraft routing, crew scheduling, runway scheduling problem and gate assignment

Medical decision making: Selection of the appropriate surgical mode for undescended testicle treatment

HANCERLIOGULLARI KOKSALMIS, GULSAH/0000-0002-2551-541XWOS: 000483755100005This study is designed to provide paediatric surgeons' perspectives on the relative importance of the criteria for choosing a surgical mode for undescended testicle treatment between open surgery (orchiopexy) or laparoscopic surgery and determine the suitable surgical mode by using the multicriteria decision-making method. The analytic hierarchy process (AHP), the technique for order preference by similarity to ideal solution (TOPSIS), and Vise Kriterijumska Optimizacija I Kompromisno Resenje (VIKOR) methods are utilized. A decision hierarchy is set with a goal, criteria, and alternatives. Our model is developed on the basis of four main criteria (time-related, patient-related, recovery-related, and complication-related factors) and 11 subcriteria (operation duration, length of stay in hospital, preoperative preparation time, recovery period after surgery, age of patient, weight of patient, aesthetic appearance, quality of life satisfaction, recurrence, possibility of infection, and vital function) as well as two alternatives, laparoscopy and open surgery. An online questionnaire was sent to the paediatric surgeons; responses from the 31 experts (i.e., paediatric surgeons) indicate that the most important criteria are found to be the time-related factors, especially preoperative preparation time. On the other hand, the least important criteria are found to be complication-related factors. Moreover, laparoscopy is chosen as the most suitable method for the undescended testicle using the AHP, TOPSIS, and VIKOR methods. This study helps paediatric surgeons' decision making by elucidating their priority criteria and representing their decision-making process in terms of quantity with the help of AHP, TOPSIS, and VIKOR methodologies