Browsing by Author "Wang, Chung-Ho"

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Basin-scale groundwater response to precipitation variation and anthropogenic pumping in Chih-Ben watershed, Taiwan
(2012-05-01)
Hsu, Kuo-Chin
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Yeh, Hsin-Fu
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Chen, You-Cheng
;
Lee, Cheng-Haw
;
Wang, Chung-Ho
The sustainable use of groundwater has become increasingly challenging due to extreme hydrological events and anthropogenic activity. In this study, the basin-scale groundwater response to precipitation variation was analyzed using an integrated model that comprises lumped models for land and river recharges and a distributed model for groundwater. The integrated model was applied to the Chih-Ben watershed, Taiwan, using 20 years (1988-2007) of data. The hydrological data were analyzed for trends using statistical tests. Based on decreasing trends in precipitation and groundwater levels and an increasing trend in stream flow, the oblique-cut method was applied to precipitation and excess infiltration to assess land and streambed recharge. Distributed numerical groundwater modeling was used to simulate the basin-scale groundwater responses to precipitation variation and anthropogenic pumping. The model was calibrated using stable-isotope and groundwater-level data. The safe yields were estimated for the Chih-Ben watershed for dry, wet, and normal precipitation scenarios. The safe yield of groundwater was shown to vary with precipitation, which does not guarantee the sustainable use of groundwater resources. Instead, water resources should be assessed at a basin scale, taking into account the whole ecosystem, rather than only considering water for human consumption in the alluvium.
Development of a new cluster index for wafer defects
(2007-01-01)
Tong, Lee-Ing
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Wang, Chung-Ho
;
Chen, Da-Lun
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工業工程與管理學系
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Department of Industrial Engineering and Management
Defect number and defect clustering are two key determinants of wafer yield. Preventing and detecting wafer defects thus is an important issue in integrated circuit manufacturing. Defect clustering tends to grow with increasing wafer size. Methods have been developed for assessing defect clustering on wafers. However, these methods require either statistical assumptions regarding defect distribution or complex computations. This study develops a new cluster index, utilizing the rotating axis technique from multivariate analysis to accurately quantify defect clusters on a wafer. The developed defect-clustering index does not require making assumptions regarding defect distribution. Thus, the proposed method can be efficiently used by engineers with little statistical background. A simulation experiment is conducted to demonstrate the effectiveness of the proposed defect-clustering index.
Optimization of multi-response processes using the VIKOR method
(2007-02-01)
Tong, Lee-Ing
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Chen, Chi-Chan
;
Wang, Chung-Ho
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Design of experiments and Taguchi methods are extensively adopted as off- line quality improvement techniques in industry. However, these methods were developed to optimize single-response processes. In many situations, multiple responses must be optimized simultaneously, since some product designs, especially in the integrated circuit industry, are becoming increasingly complex to meet customers' demands. Although several procedures for optimizing multi- response processes have been developed in recent years, the associated quality measurement indices do not consider variations in the relative quality losses of multiple responses. These procedures may therefore result in an optimization in which quality losses associated with a few responses are very small but those associated with others are very large, even if the overall average quality loss is small. Such an optimization with a large variation of quality losses among the responses is usually unacceptable to engineers. Accordingly, this study employs the VIKOR method, which is a compromise ranking method used for multicriteria decision making ( MCDM), to optimize the multiresponse process. The proposed method considers both the mean and the variation of quality losses associated with several multiple responses, and ensures a small variation in quality losses among the responses, along with a small overall average loss. Two case studies of plasma- enhanced chemical vapor deposition and copper chemical mechanical polishing demonstrate the effectiveness of the proposed method.
Using DEA to optimize a mixture design with multiple responses incorporating cost considerations
(2008-07-01)
Tsai, Chih-Wei
;
Tong, Lee-Ing
;
Wang, Chung-Ho
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
Mixture design (MD), which is commonly adopted in chemical-manufacturing, food-processing or pharmaceutical industry, is more suitable than other design of experiment methods when component proportion is a crucial influence on product quality. This study develops an optimization procedure, which utilizes Data envelopment analysis to analyze multiple inputs/outputs and costs for experiments with mixtures. Proposed procedure can optimize MD with multiple responses while maintaining low manufacturing costs, and thus enhance manufacturer competitive advantage. As demonstrated in the case of formulation design for automobile rubber bowls, proposed procedure optimizes experiments with mixtures while minimizing costs.