Browsing by Author "Hsieh, Ming-Hsiu"

Now showing 1 - 3 of 3

Can the Radical Channel Contribute to the Catalytic Cycle of N-Heterocyclic Carbene in Benzoin Condensation?
(2018-12-21)
Hsieh, Ming-Hsiu
;
Huang, Gou-Tao
;
Yu, Jen-Shiang K.
;
交大名義發表
;
生物科技學系
NHC can catalyze benzoin condensation via the key Breslow intermediate. EPR spectroscopy recently confirmed the existence of the radical species, but its catalytic role is still unclear. Herein, we use density functional approaches to study the radical-associated pathway in comparison with the nonradical mechanism reported previously. Theoretical investigations show that the nonradical path (Delta G(double dagger) = 18.7 kcal/mol) is more kinetically favorable than the radical route (Delta G(double dagger) = 27.6 kcal/mol), which is initialized by the hydrogen abstraction from the Breslow intermediate by benzaldehyde, leading to a radical pair. The product formation is thus dominated by the nonradical pathway. In addition, the Breslow intermediate is less stable than its keto form, which blocks the benzoin condensation, and the radical species could play an important role in assisting the tautomerization and promoting the catalytic reaction.
Interim equipment shutdown planning for a wafer fab during economic downturns
(2010-11-01)
Chung, Shu-Hsing
;
Hsieh, Ming-Hsiu
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Because of the low equipment utilization during periods of economic recession, managers of wafer labs are forced to plan equipment shutdowns in order to reduce variable cost and reallocate resources. Unfortunately, few studies have proposed effective solutions for equipment shutdown planning in response to economic downturns. Taking into consideration the product mix, corresponding output target, excessive capacity, production performance impact and the variable cost savings, this paper presents a new mechanism for equipment shutdown planning using a developed integer programming model. The proposed mechanism effectively provides valuable recommendations for the managements of wafer fabs regarding the type and quantity of equipment to shut down. Crown Copyright (C) 2010 Published by Elsevier Ltd. All rights reserved.
Long-term tool elimination planning for a wafer fab
(2008-04-01)
Chung, Shu-Hsing
;
Hsieh, Ming-Hsiu
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Wafer manufacturers must make decisions regarding tool elimination due to changes caused by demand, product mixes, and overseas fab capacity expansion. Such a problem is raised by leading semiconductor manufacturers in Taiwan. This paper is aimed at developing a sound mechanism for tool portfolio elimination based on determining which equipment can be pruned. In the proposed mechanism, product mix, wafer output, capital expenditure, tool utilization, protective capacity, and cycle time are taken into the overall evaluation. This paper develops an integer programming model to avoid trial-and-error and to obtain the optimal solution. Compared to the current industry approach, the results show that the proposed mechanism can effectively identify the correct tools for elimination with a large capital savings and little cycle time impact. (C) 2007 Elsevier Ltd. All rights reserved.