This paper deals with a troduction scheduling problem in a two-stage hybrid flow shop. The first stage comprises one machine and the second comprises a number of m machines. The setup is required when switching one product to another at the first stage and individual products can be assigned to only one machine at the second stage because the machines are not interchangeable. First, this paper formulates the makespan and the maximum work-in-process level. Second, this paper clarifies how the length of production run and sequencing rules will affect the manufacturing performance.

View full abstract

Considerable development resources are consumed during the software-testing phase, fundamentally consisting of module testing, integration testing, and system testing. It is very important for a manager to decide how to spend testing-resources on software-testing for developing a quality and reliable software. In this paper, using an optimal software release problem which decides when to economically stop testing, we consider testing-resource allocation policies to best use the specified testing-resources during module testing. We introduce a software reliability growth model based on a nonhomogeneous Poisson process. The model describes the time-dependent behavior of software faults detected and testing-resource expenditures spent during the testing. The optimal testing-resource allocation policies can improve reliability and shorten the testing stage. We also provide numerical examples of the optimal policies.

View full abstract

This paper deals with a sequencing problem for a mixed-model assembly line in a Just-In-Time production system. The line is stopped, whenever workers fail to complete their operations within their stations. The problem is to minimize a total cost consisting of idle times of workers and stopping times of the line. A branch-and-bound algorithm is devised for the problem. Moreover, an approximate algorithm based on simulated annealing is develored to solve real scale sequencinm problems. An optimal solution computed by the branch-and-bound algorithm is used to tune values of several parameters of the approximate algorithm. Its application to an actual assembly line demonstrates its efficiency.

View full abstract

This paper shows the existence of an optimal arrival schedule for the conveyor system without stopper. It also points out an economical reason why it is desirable to use a regular arrival schedule. Based on inspection theory, is given an interesting result that the optimal arrival schedule is a nonincreasing arrival schedule. Moreover, the optimal schedule can be achieved by introduction of a design factor, ε(0&le;ε<1), under regular arrival. Finally, a comparison between regular and nonincreasing arrival schedule is made by some numerical examples, and the Generalized CSPS under the regular arrival is discussed.

View full abstract

This paper analyses and compares the performances of two types of production ordering systems for unbalanced serial production systems. One is the sequential ordering system, which is modeled on the Kanban systems, and the other is the concurrent ordering system. Queueing network models of the production ordering systems for 5 stages serial production systems are constructed, and the performances are investigated by simulation experiments. As a result, it is clarified that the concurrent ordering system is more adjustable to the imbalance of production processes.

View full abstract

In this paper, the job-shop control policies of periodic vs. dynamic type under order-selection and fixed switching-costs are evaluated and discussed by the respective simulation models. The respective models incorporate fixed quoting/switching time in the previous analytic models, and have the two objective functions of the net reward (=price-cost) per unit time and the mean flow-time. Although the monotonicity of the optimal policy of periodic type does not necessarily hold, that of dynamic type is ascertained. Also, a comparison of the optimal policy of periodic vs. dynamic type is given.

View full abstract

An experimental study was made on the subjects doing VDT work. The main task is the retrieval and addition of randomized one digit numbers from 3 to 9 under work shift of 60 minutes work with 15 minutes rest. The following three experimental conditions were chosen as the rest conditions ; 1) full rest with the eyes completely closed all through the rest period of 15 minutes, 2) a 5 minutes' physical load by harvard step test was inserted during the 15 minutes rest, and 3) 10 minutes' mental load where the subjects must divide various figures into decided patterns according to the certain rules. From the results, it was clearly be said that the rest taken by the subjects with their eyes closed was a negative countermeasure which could not reduce the VDT fatigue, while physical task could give positive effects on improving the both psycho-physiological conditions. Mental load also gave a positive effect on VDT workers.

View full abstract