Browsing by Author "Chen, Yi-Chi"

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A Joint Codebook Design for Beamforming Systems with Transmit Antenna Selection
(2011)
Chen, Yi-Chi
;
Tsai, Shang-Ho
;
Chuang, Gene C. H.
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電機工程學系
;
Department of Electrical and Computer Engineering
This paper proposes a codebook design that considers transmit antenna selection and beamforming simultaneously. Under the same amount of feedback bits, the proposed codebook can reduce the number of RF units more than half while its performance is still maintained closely (within 0.1 dB loss) to the codebook designs that use all transmit antennas. Since RF units are expensive, the proposed codebook can greatly reduce the hardware implementational cost with slight performance degradation. Moreover, we analyze the proposed codebook and derive a lower bound of symbol error rate (SER). The derived SER lower bound generally matches the simulation results. Simulation results show the proposed codebook with around half active transmit antennas performs comparable to the Lloyd codebook design with full active antennas.
A run-time reconfigurable fabric for 3D texture filtering
(2007)
Wang, Wei-Ting
;
Chen, Yi-Chi
;
Chung, Chung-Ping
;
資訊工程學系
;
Department of Computer Science
To reduce area of texture filter for real-time rendering is challenging as user demand for 3-D scene realism increases. This work presents a low-area run-time reconfigurable texture filter design given certain performance requirement A texture filter is a part of a texture unit. The reconfiguration is on a number of bilinear filters as basic function blocks, can be implemented within individual texture unit or across multiple texture units, and is based on hierarchical decomposition of all lands of filtering algorithms. Two reconfiguration designs are proposed and examined The self-content design, in which a texture unit must be equipped with all necessary hardware to deal with all different filtering algorithms; and the sharable design, in which texture units can share their texture filters (and the total amount of useable texture units may thus change). Experimental results show that the sharable design achieves a 12% area reduction, as compared with the self-content design
Cholesteryl alpha-D-glucoside 6-acyltransferase enhances the adhesion of Helicobacter pylori to gastric epithelium
(2020-03-13)
Jan, Hau-Ming
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Chen, Yi-Chi
;
Yang, Tsai-Chen
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Ong, Lih-Lih
;
Chang, Chia-Chen
Helicobacter pylori, the most common etiologic agent of gastric diseases including gastric cancer, is auxotrophic for cholesterol and has to hijack it from gastric epithelia. Upon uptake, the bacteria convert cholesterol to cholesteryl 6 '-O-acyl-alpha-D-glucopyranoside (CAG) to promote lipid raft clustering in the host cell membranes. However, how CAG appears in the host to exert the pathogenesis still remains ambiguous. Herein we identified hp0499 to be the gene of cholesteryl alpha-D-glucopyranoside acyltransferase (CGAT). Together with cholesteryl glucosyltransferase (catalyzing the prior step), CGAT is secreted via outer membrane vesicles to the host cells for direct synthesis of CAG. This significantly enhances lipid rafts clustering, gathers adhesion molecules (including Lewis antigens and integrins alpha 5, beta 1), and promotes more bacterial adhesion. Furthermore, the clinically used drug amiodarone was shown as a potent inhibitor of CGAT to effectively reduce the bacterial adhesion, indicating that CGAT is a potential target of therapeutic intervention. Jan et al. identify cholesteryl alpha-D- glucopyranoside acyltransferase as a key enzyme in Helicobacter pylori's synthesis of cholesteryl 6'-O-acyl-alpha-D-glucopyranoside, which promotes bacterial adhesion. This study provides insights into the H. pylori-induced pathogenesis and therapeutic strategies against it.
Handwritten Signature Verification by Using a Six-Axis Motion Sensor and SVM
(2019-01-01)
Cheng, Chang-Chieh
;
Chen, Yi-Chi
;
Ching, Yu-Tai
;
資訊工程學系
;
資訊技術服務中心
Signature verification, if we consider the muscle memory, is a biometric for identification technology. To access muscle memory, we use a motion sensor that consists of accelerometer and gyroscope to implement a signature verification system. The motion sensor records six motion values including three-axis accelerations and angular velocities while name signing. 14 features of signature are extracted from the sequence of accelerations and angular velocities. A support vector machine (SVM) is then applied to verify the signatures. The proposed method was applied to verify the Chinese signatures. The SVM is trained by the training data from each person. The true positive rate of the proposed method can reach to 95.66%. Fake signatures generated by tracing from true signatures can also be recognized by the proposed method.
Metabolic labelling of cholesteryl glucosides in Helicobacter pylori reveals how the uptake of human lipids enhances bacterial virulence
(2016-01-01)
Jan, Hau-Ming
;
Chen, Yi-Chi
;
Shih, Yu-Yin
;
Huang, Yu-Chen
;
Tu, Zhijay
Helicobacter pylori infects approximately half of the human population and is the main cause of various gastric diseases. This pathogen is auxotrophic for cholesterol, which it converts upon uptake to various cholesteryl alpha-glucoside derivatives, including cholesteryl 6'-acyl and 6'-phosphatidyl alpha-glucosides (CAGs and CPGs). Owing to a lack of sensitive analytical methods, it is not known if CAGs and CPGs play distinct physiological roles or how the acyl chain component affects function. Herein we established a metabolite-labelling method for characterising these derivatives qualitatively and quantitatively with a femtomolar detection limit. The development generated an MS/MS database of CGds, allowing for profiling of all the cholesterol-derived metabolites. The subsequent analysis led to the unprecedented information that these bacteria acquire phospholipids from the membrane of epithelial cells for CAG biosynthesis. The resulting increase in longer or/and unsaturated CAG acyl chains helps to promote lipid raft formation and thus delivery of the virulence factor CagA into the host cell, supporting the idea that the host/pathogen interplay enhances bacterial virulence. These findings demonstrate an important connection between the chain length of CAGs and the bacterial pathogenicity.
Poster: Handwritten Signature Verification by Using a Six-Axis Motion Sensor and SVM
(2019-01-01)
Cheng, Chang-Chieh
;
Chen, Yi-Chi
;
Ching, Yu-Tai
;
資訊工程學系
;
資訊技術服務中心
Signature verification, if we consider the muscle memory, is a biometric for identification technology. To access muscle memory, we use a motion sensor that consists of accelerometer and gyroscope to implement a signature verification system. The motion sensor records six motion values including three-axis accelerations and angular velocities while name signing. 14 features of signature are extracted from the sequence of accelerations and angular velocities. A support vector machine (SVM) is then applied to verify the signatures. The proposed method was applied to verify the Chinese signatures. The SVM is trained by the training data from each person. The true positive rate of the proposed method can reach to 95.66%. Fake signatures generated by tracing from true signatures can also be recognized by the proposed method.
The cysteine 703 to isoleucine or histidine mutation of the oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae generates an iridal-type triterpenoid
(2012-11-01)
Chang, Cheng-Hsiang
;
Chen, Yi-Chi
;
Tseng, Sheng-Wei
;
Liu, Yuan-Ting
;
Wen, Hao-Yu
The Cys703 to Ile or His mutation within Saccharomyces cerevisiae oxidosqualene-lanosterol cyclase ERG7 (ERG7(C7031/H)) generates an unusual truncated bicyclic rearranged intermediate, (8R,9R,10R)-polypoda-5,13E,17E,21-tetraen-3 beta-ol, related to iridal-skeleton triterpenoid. Numerous oxidosqualene-cyclized truncated intermediates, including tricyclic, unrearranged tetracyclic with 17 alpha/beta exocyclic hydrocarbon side chain, rearranged tetracyclic, and chair chair chair tricyclic intermediates (compounds 3-9), were also isolated from the ERG7(C703X) site-saturated mutations or the ERG7(F699T/C7031) double mutation, indicating the functional role of the Cys703 residue in stabilizing the bicyclic C-8 cation and the rearranged intermediate or interacting with Phe699, and opened a new avenue of engineering ERG7 for producing biological active agents. (C) 2012 Elsevier Masson SAS. All rights reserved.