Browsing by Author "Chen, Guan-Jie"

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Automated Segmentation of Dental Calculus in Optical Coherence Tomography Images
(2018-01-01)
Lee, Chia-Yen
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Chuang, Ching-Cheng
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Chen, Guan-Jie
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Huang, Chih-Chia
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Lee, Shyh-Yuan
The presence of dental calculus is highly correlated with the formation and advancement of periodontal disease. The occurrence and relapse of periodontal disease can be prevented only if dental calculus is completely removed. In this study, optical coherence tomography (OCT) is used to obtain two-dimensional cross-sectional images of tooth samples, in conjunction with a segmentation technique that enables automatic identification of dental calculus. We propose the vertical intensity transform function to correct the nonuniform instrument signal intensity caused by OCT. Afterwards, the detection ranges are defined by K-means or the Markov random field (MRF), and the candidate range is selected on the basis of mathematical morphology (MM). Finally, the features (thickness gradient, texture, and tooth surface slope) are quantified, and dental calculus is recognized and segmented. In the preliminary result, the sensitivity is 87.5%. The mean distance between the boundaries generated by the proposed algorithm and the corresponding manually delineated boundaries is 2.52 +/- 3.54 pixels. Our proposed algorithm assists physicians to determine dental calculus more easily. Doctors no longer need to rely solely on their experiences to recognize dental calculus, but can refer to specific data to assist in diagnosis.
Performance of piezoelectric fins for heat dissipation
(2015-07-01)
Sheu, Wen-Jenn
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Chen, Guan-Jie
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Wang, Chi-Chuan
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機械工程學系
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Department of Mechanical Engineering
In this study, a conceptual design employs the piezoelectric patch to a copper plate to form a so-called piezoelectric fin applicable for heat dissipation. A total of nine piezoelectric fins subject to various bonding and piezoelectric patch are made and tested. A piezoelectric fin array is also fabricated as a substitute of heat sink under natural convection. It is found that the tip displacement and the decay of performance of piezoelectric fin are intimately related to the bonding glues. The bonding glues with a higher Young\'s modulus lead to a larger fin tip displacement. The tip displacement increases with applied voltage and the length of piezoelectric patch and a maximum tip displacement of 10.9 mm is observed for TCE bonding under a 100 V power source. A maximum 64% heat transfer augmentation at a supplied power of 5 W is encountered for the piezoelectric fin array. The corresponding fin displacement in the fin array is suppressed owing to the resistant interactions amid adjacent piezoelectric fins. The heat transfer augmentation is moderately reduced to about 40% when the supplied power is raised to 15 W. (C) 2015 Elsevier Ltd. All rights reserved.