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A constrained self-adaptive harmony search algorithm (CSAHS) with 2-opt swapping (CSAHS-2opt) for driver scheduling problem of university shuttle bus (DSPUSB) was proposed in this study. In generating a schedule, there are some constraints that should be catered to obtain an optimum result. In DSPUSB, fairness of task distribution among drivers is one of the main issues that are very crucial and can affect the performance and quality of services. Therefore, to maximise the fairness, the violation of soft constraints for DSPUSB including shift and route should be minimised. CSAHS with 2-opt swapping was proposed focusing on minimising soft constraint violation. In standard harmony search (HS), the value of distance bandwidth (BW) parameter was static, while in this study the BW was dynamically changed and determined based on the current solution of each driver every week. Here, a set of distance BW value was formed based on shift constraint. In each iteration, the BW values were often changed and randomly chosen within the set, whereas the 2-opt swapping normally used in travelling salesman problem was applied for route constraint based on some rules. These improvements are capable of reducing the repetition task that leads to fairness issue. The result demonstrated that CSAHS-2opt gave better solutions compared with standard HS, improved HS and parameter-adaptive HS.

Manufacturers of high mix and high volume products are forced to focus on strategic capacity planning in their production system to remain competitive. This work is based on a case study in a hard disk drive manufacturing company with the objective of improving the throughput and tester utilization in the testing assembly line. The problem is complex as there were multiple products, each product model undergoing different testing routes and testing duration. This is further complicated by 2 different fixed capacity testers where each tester is mix-loaded with different products. As the scenario is too complex to be solved by analytical methods, a hybrid simulation approach was proposed to find a feasible solution to the problem. The problem was first formulated with a mathematical model to optimize the number of testers with predefined configurations. Each configuration was then simulated to determine the throughput and tester utilization. Finally the TOPSIS and AHP methods were employed to determine the best configuration. The results of the proposed method improved throughput and tester utilization by 6.71% and 26.67%, respectively.

With increasing competition and customers’ demand, manufacturers are faced with the challenge of improving throughput and on-time deliveries. This issues is further complicated for job shop manufacturing due to variabilities in demands, process flow and process time. This paper proposes a hybrid material flow control mechanism that combines a dispatching rule with the POLCA system in job shop environment. Data are collected from a case company and discrete event simulation is used to evaluate the Work In Process (WIP), throughput (TP), average Manufacturing Critical path Time (MCT) per job and On-Time Delivery (OTD) for three different flow controls. The performance of each model is evaluated and statistically validated. In this study, the hybrid POLCA performs the best for all performance measures.

As the pressure is increasing to compete with others to get customer orders in the global market, companies are struggling to build up competitive advantages that are hard to imitate. The trend shows more and more customers demand faster product delivery in the last decade. The Quick Response Manufacturing (QRM) approach provides significant benefits to engineer-to-order (ETO) companies through its focus on lead time reduction. A precision parts manufacturer was selected as case study to what extent QRM is a suitable solution to improve the delivery performance. This paper describes the implementation of the QRM concepts and illustrates how they were deciphered into practices that streamline the process across the organization. The study measures the effectiveness of the QRM framework through its ability to achieve better performance through concurrently reducing manufacturing critical-path time, lowering capacity utilization level and increasing throughput.

Micro heat pipes (MHPs) are, essentially, miniature heat transfer devices which use phase change to transfer thermal energy. In recent years, there have been numerous proposals for their applications in cooling electronic devices. In this paper, the axial liquid distribution of a triangular MHP is investigated for the case of inclined orientation. The study is limited to the case of positive inclination, whereby the condenser section is elevated from horizontal position. In this case, the inclusion of gravity renders the governing equation unsolvable analytically, and the 4th order Runge-Kutta method has been selected to solve it numerically. The results show that for a horizontally oriented MHP, so that the effect of gravity can be neglected, the liquid distribution along the axial direction increases monotonically from the minimum value at the evaporator end to the maximum at the condenser end. However, if the MHP is positively inclined, the axial distribution of the liquid phase is changed qualitatively. While the liquid distribution still increases monotonically starting from the evaporator end, it reaches its maximum value not at the condenser end but at a certain point in the condenser section, beyond which the liquid distribution decreases monotonically. Moreover, as the angle of inclination is increased, the maximum-distribution point moves further away from the condenser end. This maximum point, where potentially flooding will first take place, results from the balance between the effects of gravity and the heat load on the MHP, the former having the propensity to move all the liquid from the condenser towards the evaporator while the latter the tendency to place more liquid in the condenser section. As the liquid distribution assumes its greatest value at the maximum point, a throat like formation appears there. This formation is detrimental to the performance of an MHP, because it hinders, and at worst may block, the axial flow of the vapor phase.Copyright © 2004 by ASME

Advancement of technology and trends in globalization has resulted in higher customer demands and expectations. Manufacturers now offer mass customization to stay competitive. In the semiconductor industry, where product mix and volume are high, production is further complicated by the different process routes and processing times for different product families. Coupled with rapid changeovers of products, it is essential to keep the work in process (WIP) low in order to reduce the inventory level on the shop floor. CONWIP is a production control strategy applicable in many manufacturing environment, that uses cards to control WIP level. In this paper, discrete event simulation models for processes at the End of Line (EOL) assembly in a semiconductor manufacturing company were developed. Experiments were conducted using these models to compare the current system with the single loop and multi loop CONWIP control mechanisms. Performance parameters of throughput, cycle time and WIP level were compared in all experiments. The result, firstly, shows that, generally, CONWIP production control is more effective to reduce WIP level compared to the current system. The reduction in WIP is accompanied by corresponding improvements of cycle times. Secondly, the multi-loop system performs better than the single loop system with higher cycle time reduction. Multi loop control is also more robust and provides a better control mechanism compared to the single loop system.