Minimizing the number of tardy jobs on unrelated parallel machines with dirt consideration
JOURNAL OF INDUSTRIAL AND PRODUCTION ENGINEERING
Authors: Su, Ling-Huey; Hsiao, Ming-Chih; Zhou, Hongming; Chou, Fuh-Der
Abstract
This paper considers an unrelated parallel machine scheduling problem with the objective of minimizing the number of tardy jobs. Each machine should stop periodically to perform maintenance activities. The problem, motivated from a wafer manufacturing company, considers the job scheduling and maintenance activities simultaneously under dirt constraint. That is, the dirt accumulation in the machine does not exceed the prespecified dirt limit. A mixed binary integer programming (MBIP) model is developed to find optimal solutions, and two three-phase heuristics are proposed. The heuristics assign each job to its most efficient machine first. Then, an intension of Moore's algorithm is applied for each machine, and finally the solution is improved by the forward/backward insert mechanism. The experimental results showed that the proposed heuristics perform well. Furthermore, the efficiency of the MBIP model and the impact of the dirt accumulation as well as maintenance time are studied in detail.
On the Transitions of Deformation Modes of Fully Austenitic Steels at Room Temperature
METALS AND MATERIALS INTERNATIONAL
Authors: Park, Kyung-Tae; Kim, Gyosung; Kim, Sung Kyu; Lee, Sang Woo; Hwang, Si Woo; Lee, Chong Soo
Abstract
The present study was undertaken to provide a more comprehensive understanding of the deformation modes of advanced fully austenitic steels exhibiting an enhanced combination of strength and ductility. For this purpose, a new plasticity, called microband induced plasticity (MBIP), was introduced. In addition, the origin of its superb combination of strength and ductility over the well-known transformation induced plasticity (TRIP) and twin induced plasticity (TWIP) was elucidated. With the aids of previously developed models, we focused on predicting the transitions among TRIP, TWIP, and MBIP, primarily in terms of the stacking fault energy. The analysis revealed that the TRIP-TWIP transition can be reasonably predicted by the energy balance for FCC austenite - IICP epsilon martensite transformation. The TWIP-MBIP transition can be addressed by the critical stress for mechanical twinning, which causes the infinite divergence of the Shockley partials. Lastly, the TWIP-MBIP transition model was validated by comparing it with the experimental data.
COA
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