Recently, the transportation capability of the automated material handling system (AMHS) has emerged as a major barrier to the semiconductor fabrication facility (FAB), because it can limit the FAB production capacity. In this study, we propose a prediction method for a machine allocation problem of production scheduling in consideration with the AMHS’s constraints. The proposed method dynamically targets a machine for the next process by identifying diverse production conditions. We use a deep neural network-based dynamic scheduling method considering the overall production environment, which includes the remaining processing time, facility states, transportation time and traffic congestion, work-inprocess distribution, and intermediate buffer states. To demonstrate the superiority and efficiency of the proposed method, we conducted experimental studies to compare the proposed model with the existing priority rule-based and analytic models under the static and dynamic environments. From the results, we verify that the proposed dynamic scheduling system can enhance the performance of existing AMHS and reduce machine starvation and production losses.

Unmanned aerial vehicles (UAVs) are expected to make groundbreaking changes in the logistics industry. Leading logistics companies have been developing and testing their usage of UAVs recently as an environmentally friendly and cost-effective option. In this paper, we investigate how much the UAV delivery service is environmentally friendly compared to the traditional ground vehicle (GV) delivery service. Since there are fuel (battery) and loadable weight restrictions in the UAV delivery, multi-hopping of UAV is necessary, which may cause a large consumption of electrical energy. We present a two-phase approach. In Phase I, a new vehicle routing model to obtain optimal delivery schedules for both UAV-alone and GV-alone delivery systems is proposed, which considers each system’s restrictions, such as the max loadable weight and fuel replenishment. In Phase II, CO₂ emissions are computed as a sustainability measure based on the travelling distance of the optimal route obtained from Phase I, along with various GV travel-speeds. A case study finds that the UAV-alone delivery system is much more CO₂ efficient in all ranges of the GV speeds investigated.

This study analyzes the performance of a queue length-dependent overload control policy using a leaky bucket (LB) scheme. This queueing model is applied to the operation of a battery swapping and charging station for electric vehicles (EVs). In addition to the LB scheme, we propose two congestion control policies based on EV queue length thresholds. With these policies, the model determines both EV-arrival and battery-supply intervals, and these depend on the number of EVs waiting in the queue. The queue length distributions, including those at arbitrary epochs, are derived using embedded Markov chain and supplementary variable methods. Performance measures such as blocking probability and mean waiting time are investigated using numerical examples. We study the characteristics of the system using numerical examples and use a cost analysis to investigate situations in which the application of each congestion control policy is advantageous.

Clustered multi-task learning, which aims to leverage the generalization performance over clustered tasks, has shown an outstanding performance in various machine learning applications. In this paper, a clustered multi-task sequence-to-sequence learning (CMSL) for autonomous vehicle systems (AVSs) in large-scale semiconductor fabrications (fab) is proposed, where AVSs are widely used for wafer transfers. Recently, as fabs become larger, the repositioning of idle vehicles to where they may be requested has become a significant challenge because inefficient vehicle balancing leads to transfer delays, resulting in production machine idleness. However, existing vehicle repositioning systems are mainly controlled by human operators, and it is difficult for such systems to guarantee efficiency. Further, we should handle the small data problem, which is insufficient for machine learning because of the irregular time-varying manufacturing environments. The main purpose of this study is to examine CMSL-based predictive control of idle vehicle repositioning to maximize machine utilization. We conducted an experimental evaluation to compare the prediction accuracy of CMSL with existing methods. Further, a case study in a real largescale semiconductor plant, demonstrated that the proposed predictive approach outperforms the existing approaches in terms of transfer efficiency and machine utilization.

In recent years, innovation diffusion models and their applications are increasingly studied because of the rapid development of technology. Since the publication of Norton and Bass (1987), the models on multi-generation diffusion have resulted in a body of articles, books, and reports. In this study, the progress of multi-generation innovation diffusion studies based on 44 research papers published from 1971 to 2018 is reviewed. Insights from different research streams are summarized and outlines an entry point for new researchers focusing on multi-generation innovation diffusion is provided.

We consider the discrete-timeGeoX/G/1queue underN-policy with single and multiple vacations. In this queueing system, the server takes multiple vacations and a single vacation whenever the system becomes empty and begins to serve customers only if the queue length is at least a predetermined threshold valueN. Using the well-known property of stochastic decomposition, we derive the stationary queue-length distributions for both vacation models in a simple and unified manner. In addition, we derive their busy as well as idle-period distributions. Some classical vacation models are considered as special cases.