Browsing by Subject "Industrial engineering"

Now showing 1 - 6 of 6

Open Access
Batch scheduling to minimize the weighted number of tardy jobs
(Pergamon Press, 2007) Erel, E.; Ghosh, J. B.
In this paper, we address a single-machine scheduling problem with due dates and batch setup times to minimize the weighted number of tardy jobs. We give a pseudo-polynomial dynamic program and a fully-polynomial approximation scheme for the case where the due dates are uniform within a family.
Open Access
A beam search algorithm to optimize robustness under random machine breakdowns and processing time variability
(Institute of Industrial Engineers, 2007) Gören, S.; Sabuncuoğlu, İhsan
The vast majority of the machine scheduling research assumes complete information about the scheduling problem and a static environment in which scheduling systems operate. In practice, however, scheduling systems are subject to considerable uncertainty in dynamic environments. The ability to cope with the uncertainty in scheduling process is becoming increasingly important in today's highly dynamic and competitive business environments. In the literature, two approaches have appeared as the effective way: reactive and proactive scheduling. The objective in reactive scheduling is to revise schedules as necessary, while proactive scheduling attempts to incorporate future disruptions when generating schedules. In this paper we take a proactive scheduling approach to solve a machine scheduling problem with two sources of uncertainty: processing time variability and machine breakdowns. We define two robustness measures and develop a heuristic based on beam search methodology to optimize them. The computational results show that the proposed algorithms perform significantly better than a number of heuristics available in the literature.
Open Access
Effect of discrete batch WIP transfer on the efficiency of production lines
(Taylor & Francis, 1993) Erel, E.
In this paper, the effect of discrete batch transfer of WIP between workstations on the efficiency of asynchronous production lines is analysed via a simulation model. The processing times are assumed to be random variables distributed according to specific distribution functions. The WIP transfer design problem involves determining the number of containers to allocate to each buffer location and the container capacity. Interesting and valuable information for practitioners has been obtained. It is found that loss in capacity occurs in the first few stations. Another finding is that an important portion of the lost capacity can be regained by allocating two containers to each buffer location, and if it is impossible to assign two containers to each location, then no single-container location should be adjacent to another single-container location.
Open Access
Multi-population parallel genetic algorithm using a new genetic representation for the euclidean traveling salesman problem
(İstanbul Technical University, 2005) Kapanoğlu, M.; Koç, İ. O.; Kara, İ.; Aktürk, Mehmet Selim
This paper introduces a multi-population genetic algorithm (M-PPGA) using a new genetic representation, the kth-nearest neighbor representation, for Euclidean Traveling Salesman Problems. The proposed M-PPGA runs M greedy genetic algorithms on M separate populations, each with two new operators, intersection repairing and cheapest insert. The M-PPGA finds optimal or near optimal solutions by using a novel communication operator among individually converged populations. The algorithm generates high quality building blocks within each population; then, combines these blocks to build the optimal or near optimal solutions by means of the communication operator. The proposed M-PPGA outperforms the GAs that we know of as competitive with respect to running times and solution quality, over the considered test problems including the Turkey81.
Open Access
On stabilizing with PID controllers
(IEEE, 2007-06) Saadaoui, K.; Özgüler, A. Bülent
In this paper we give an algorithm that determines the set of all stabilizing proportional-integral-derivative (PID) controllers that places the poles of the closed loop system in a desired stability region S. The algorithm is applicable to linear, time invariant, single-input single-output plants. The solution is based on a generalization of the Hermite-Biehler theorem applicable to polynomials with complex coefficients and the the application of a stabilizing gain algorithm to three auxiliary plants. ©2007 IEEE.
Open Access
A problem space algorithm for single machine weighted tardiness problems
(Taylor & Francis Inc., 2003) Avcı, S.; Aktürk, M. S.; Storer, R. H.
We propose a problem space genetic algorithm to solve single machine total weighted tardiness scheduling problems. The proposed algorithm utilizes global and time-dependent local dominance rules to improve the neighborhood structure of the search space. They are also a powerful exploitation (intensifying) tool since the global optimum is one of the local optimum solutions. Furthermore, the problem space search method significantly enhances the exploration (diversification) capability of the genetic algorithm. In summary, we can improve both solution quality and robustness over the other local search algorithms reported in the literature.