Browsing by Author "Chang, Y. -C."

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Reliability assessment of an aircraft propulsion system using IFS and OWA tree
(2008)
Chang, K. -H.
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Cheng, C. -H.
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Chang, Y. -C.
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工業工程與管理學系
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Department of Industrial Engineering and Management
In conventional system reliability analysis, the failure probabilities of components of a system are treated as exact values when the failure probability of the entire system is estimated. However, it may be difficult or even impossible to precisely determine the failure probabilities of components as early as the product design phase. Therefore, an efficient and simplified algorithm to assess system reliability is needed. This article proposes a deductive top-down estimation methodology, which combines intuitionistic fuzzy set (IFS) and ordered weighted averaging (OWA) operators to evaluate system reliability. A case of an aircraft propulsion system from an aerospace company is presented to further illustrate the proposed approach. After comparing results from the proposed method and two other approaches, this research found that the proposed approach provides a more accurate and reasonable reliability assessment.
Scale dependency of fractional flow dimension in a fractured formation
(2011)
Chang, Y. -C.
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Yeh, H. -D.
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Liang, K. -F.
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Kuo, M. -C. T.
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環境工程研究所
The flow dimensions of fractured media were usually predefined before the determination of the hydraulic parameters from the analysis of field data in the past. However, it would be improper to make assumption about the flow geometry of fractured media before site characterization because the hydraulic structures and flow paths are complex in the fractured media. An appropriate way to investigate the hydrodynamic behavior of a fracture system is to determine the flow dimension and aquifer parameters simultaneously. The objective of this study is to analyze a set of field data obtained from four observation wells during an 11-day hydraulic test at Chingshui geothermal field (CGF) in Taiwan in determining the hydrogeologic properties of the fractured formation. Based on the generalized radial flow (GRF) model and the optimization scheme, simulated annealing, an approach is therefore developed for the data analyses. The GRF model allows the flow dimension to be integer or fractional. We found that the fractional flow dimension of CGF increases near linearly with the distance between the pumping well and observation well, i.e. the flow dimension of CGF exhibits scale-dependent phenomenon. This study provides insights into interpretation of fracture flow at CGF and gives a reference for characterizing the hydrogeologic properties of fractured media.
The Epidemiology and Characteristics of Q fever and Co-infections with Scrub Typhus, Murine Typhus or Leptospirosis in Taiwan: A Nationwide Database Study
(2017-11-01)
Lai, C. -H.
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Sun, W.
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Lee, C. -H.
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Lin, J. -N.
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Liao, M. -H.
Q fever (QF) is a worldwide zoonosis associated with outbreaks. Only a few nationwide studies regarding the surveillance and epidemiology of human QF have been reported. Although QF is endemic in Taiwan, a nationwide database investigation of the epidemiology and characteristics of QF and its associations with scrub typhus (ST), murine typhus (MT) and leptospirosis (LS) has never been reported. We analysed nationwide databases of suspected QF, ST, MT and LS cases from October 2007 to December 2014 obtained from the Centers for Disease Control, Taiwan. A total of 468 (4.2%) QF cases were identified among 11109 suspected QF cases. QF cases were mainly distributed in the southern and Kaohsiung-Pingtung regions but rarely in the eastern region. Compared to non-QF cases, QF cases had significantly higher percentages of males (88.7 versus 66.2%) and high-risk occupations (farming, animal husbandry or veterinary medicine) (16.2 versus 10.5%). But the percentages of specific animal contact, including cattle (0.6 versus 0.8%) and goats (0.9 versus 1.0%), were low in both. The majority of suspected QF cases (89.4%) were simultaneously suspected with ST, MT or LS, and the combinations of suspected diseases differed between regions. The number of suspected QF cases from the eastern region decreased since 2009, which was not observed in other regions. A total of 1420 (12.8%) cases had confirmed diseases, including QF (453, 4.1%), QF+ST (7, 0.06%), QF+MT (4, 0.04%), QF+LS (4, 0.04%), MT (186, 1.7%), ST (545, 4.9%), ST+LS (11, 0.1%) and LS (210, 1.9%). Compared to cases of unknown disease, QF cases had larger percentages of high-risk occupations (16.2 versus 9.6%) but similar histories of animal contact (29.8 versus 25.1%). QF is an endemic disease in southern Taiwan. It is difficult to differentiate QF from ST, MT or LS only by high-risk occupations and history of animal contact, and co-infection of QF with these diseases should be considered.
Tidal propagation in an oceanic island with sloping beaches
(2010)
Chang, Y. -C.
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Jeng, D-S
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Yeh, H. -D.
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環境工程研究所
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Institute of Environmental Engineering
In this study, a new analytical solution for describing the tide-induced groundwater fluctuations in oceanic islands with finite length and different slopes of the beaches is developed. Unlike previous solutions, the present solution is not only applicable for a semi-infinite coastal aquifer, but also for an oceanic island with finite length and different sloping beaches. The solution can be used to investigate the effect of higher-order components and beach slopes on the water table fluctuations. The results demonstrate the effect of higher-order components increases with the shallow water parameter or amplitude parameter and the water table level increases as beach slopes decrease.
Wavelength-selection erbium fiber laser with single-mode operation using simple ring design
(2010-04-01)
Yeh, C. -H.
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Chow, C. -W.
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Chang, Y. -C.
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光電工程學系
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光電工程研究所
In this demonstration, we propose and experimentally investigate a wavelength-selection erbium-doped fiber (EDF) laser in single-longitudinal-mode (SLM) by using simple fiber ring scheme design. We use a tunable bandpass filter (TBF) inside the gain cavity to restrict the lasing frequency. The proposed ring cavities can also serve as the mode filters for side mode suppression. Based on the simple ring cavity design, the mode hopping can be avoided to achieve SLM output. The TBF inside the laser scheme also obtains the wavelength tuning in the range of 1520.02 to 1562.02 nm. In addition, the output performance of the proposed fiber laser has also been discussed.
Wavelength-selection erbium fiber laser with single-mode operation using simple ring design
(2010-04-01)
Yeh, C. -H.
;
Chow, C. -W.
;
Chang, Y. -C.
;
光電工程學系
;
Department of Photonics
In this demonstration, we propose and experimentally investigate a wavelength-selection erbium-doped fiber (EDF) laser in single-longitudinal-mode (SLM) by using simple fiber ring scheme design. We use a tunable bandpass filter (TBF) inside the gain cavity to restrict the lasing frequency. The proposed ring cavities can also serve as the mode filters for side mode suppression. Based on the simple ring cavity design, the mode hopping can be avoided to achieve SLM output. The TBF inside the laser scheme also obtains the wavelength tuning in the range of 1520.02 to 1562.02 nm. In addition, the output performance of the proposed fiber laser has also been discussed.