Hajime Yamashina’s research while affiliated with Kyoto University and other places

This paper deals with the role of inventory banks in balanced and unbalanced flow-line production systems by presenting results of a theoretical study of the problem and numerical experiments by computer simulation. It is shown that if the costs of both storage capacity and division of the line for a buffer are high, and therefore installing a buffer is not possible, then the line should be designed to have the same cycle times over all stages. When installing a buffer is possible, the line should be designed in such a way that the stage production rates are the same. Provision of a buffer in this case will improve line output.

This paper deals with the scheduling problem to minimize the weighted mean of total set-up time and total tardiness on a single machine. It has been shown that it is possible to develop a Branch and Bound method to solve this ill-structured scheduling problem by combining the well-known Branch and Bound method for the minimization of total set-up time and the one for the minimization of total tardiness, but that the size of jobs to be handled by this method within 15 seconds by a large computer is about 11. The conventional insertion and exchange methods are effective for only small-scale problems. For a large-scale problem, it is recommended to apply the multi-insertion method which improves a given sequence by inserting a set of jobs requiring a relatively small sum of set-up times into other positions of the sequence. Run times of the new heuristic combined with the conventional insertion and exchange methods grow approximately as N3.3 with the size (N) of jobs.

The purpose of this paper is to describe a new formulation of the mixed-model sequencing model in such a way as to minimize the risk of stopping the conveyor under the circumstances of system variability and to develop an efficient heuristic method for large-scale, mixed-model assembly lines. The proposed method always produced optimal solutions for. randomly constructed small-scale, mixed-model sequencing problems for which the optimal solutions were available through the application of the improved branch and bound method. The method should produce excellent (and almost always optimal) results for actual large-scale, mixedi-model sequencing problems.

To minimize makespan on parallel non-identical processors, a three-phase optimum-seeking algorithm based on a heuristic method, restricted backtracking and total backtracking methods has been developed. To investigate the practical application of the algorithm, a factory study was also made. (1) It has become possible by this algorithm to find an optimal schedule which minimizes makespan. (2) In practice, the application of the heuristic method constituting the first phase of the algorithm will suffice. Run times of the heuristic method grows approximately as (N/M) 23 with the number of jobs, N, and the number of machines, M. While, they grow as M2 with a fixed value of (N/M).

This paper investigates the role of buffer storage capacity in the unbalanced production line where cycle times vary from stage to stage, by analyzing the effects of degree of unbalance and buffer storage capacity on the production rate and the mean number of units in the storage area. It is shown that if buffer installation, is not possible, the line should be designed to have the same cycle times over all stages. When buffer installation is possible, the line should be designed in such a way that the stage production rates are the same by being unbalanced deliberately if the characteristics of breakdown and repair of the stages are not identical. The improvement of production rate by the provision of a buffer can be expected in this case. Due to technical considerations, if the line cannot be designed such that the stage production rates are almost the same, then it is unlikely that the installation of a buffer will be justified.

The purpose of this paper is to gain insight into the effect of buffer storage capacity in two-stage transfer lines by presenting results of a theoretical study of the problem. A Markov model of the problem is proposed to analyze the effect of in-process inventory banks on the production rate and the mean number of units in the storage area. Based on the model developed, the effect of internal storage is evaluated, and the question of how much buffer storage capacity should be provided is discussed.