This research examines the production control problem in two-station tandem queueing systems under time constraints. In these two-station tandem queueing systems, jobs must first be processed at the upstream station and then the downstream station. For each job, the sum of the waiting and processing time in the downstream queue is limited by an upper bound. This time constraint is called the process queue time constraint. When the process queue time constraint is violated, a significant scrap cost will be accrued. In this research, we develop a Markov decision model to study the production control problem under process queue time constraints. The objective is to minimise the sum of the expected longrun average inventory holding costs and scrap costs. According to the Markov decision model, an interesting exhaustive structure of the optimal production control policy is found. Based on this exhaustive structure, an efficient algorithm is developed to solve the production control problem numerically. The performance of the proposed algorithm is verified by a simulation study. Compared with other heuristics in the literature, the proposed algorithm can significantly reduce production costs while improving system throughput and utilisation.
Abstract-The overhead crane is one of dangerous machines. It may cause personnel injury, or even property damages if any accidents happen in working area. Thus, to ensure safe operation, the load size, route and working environment should be taken into consideration. This study developed a safety alarm device for overhead crane to prevent impacting persons or objects, and used image processing technology to create a video surveillance system. It can track the target object automatically and maintain the preset distance between the warning limit and the hanging object as the hanging object ascends or descends. It can be applied on an overhead crane for early warning on collision and prevention of the hanging object from impacting the workers or other equipments. The distance between the obstacle and hanging object is estimated by using perspective projection, translation of axes and rotation skills, thus ensuring the safety effect.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.