Browsing by Subject "Production scheduling--Data processing."

Now showing 1 - 3 of 3

Open Access
An analysis of order review
(1995) Karapınar, H Yavuz
Order Review/Release (ORR) activities have mostly been ignored in past job shop research. In the majority of these studies, arriving jobs are immediately released to the shop floor without considering any information about the job and the system status. In practice, however, jobs arriving at the shop are first collected in a pool and then released periodically according to some release criterion. Although practitioners use ORR mechanisms to improve shop floor performance, researchers have found limited supports for the use of these input regulation policies. In this thesis, we reexamine the problem in a capacitated system. Specifically, we compare the performances of the ORR policies in a job shop with finite buffer capacities and material handling considerations. A new ORR mechanism is also proposed and compared with other methods.
Open Access
Common due date early
(2013) Şirvan, Fatma
This study considers a scheduling problem with position-dependent deteriorating jobs and a maintenance activity in a single machine. Even in the absence of maintenance activity and deterioration problem is NP-hard. A solution comprises the following: (i) positions of jobs, (ii) the position of the maintenance activity, (iii) starting time of the first job in the schedule. After the maintenance activity, machine will revert to its initial condition and deterioration will start anew. The objective is to minimize the total weighted earliness and tardiness costs. Jobs scheduled before (after) the due-date are penalized according to their earliness (tardiness) value. Polynomial (O(n log n)) time solutions are provided for some special cases. No polynomial solution exists for instances with tight due-dates. We propose a mixed integer programming model and efficient algorithms for the cases where mathematical formulation is not efficient in terms of computational time requirements. Computational results show that the proposed algorithms perform well in terms of both solution quality and computation time.
Open Access
Reactive scheduling in cellular manufacturing systems
(1993) Görgülü, Elif
A real-time scheduling problem, specifically rescheduling under machine breakdowns, is considered in this thesis. A heuristic approach is developed for a manufacturing cell with a modified flow shop structure. The strategy reschedules part of the initial schedule to match up with the preschedule at some point. In contrast to other studies, the objective is to create a new schedule that is consistent with the other production planning decisions like material flow and purchasing by utilizing the time critical decision making concept. In the proposed heuristic approach, a new rescheduling strategy is developed and different match-up points are defined for each machine in order to maximize the flexibility during rescheduling. It is compared with alternative reactive scheduling methods in an experimental design and significance of some factors are tested by analysis of variance tests.