Browsing by Author "Chen, Kuan-Yu"

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A conservative scheme for solving coupled surface-bulk convection-diffusion equations with an application to interfacial flows with soluble surfactant
(2014-01-15)
Chen, Kuan-Yu
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Lai, Ming-Chih
;
應用數學系
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數學建模與科學計算所(含中心)
;
Department of Applied Mathematics
Many physical problems arising in biological or material sciences involve solving partial differential equations in deformable interfaces or complex domains. For instance, the surfactant (an amphiphilic molecular) which usually favors the presence in the fluid interface may couple with the surfactant soluble in one of bulk domains through adsorption and desorption processes. Thus, it is important to accurately solve coupled surface-bulk convection-diffusion equations especially when the interface is moving. In this paper, we first rewrite the original bulk concentration equation in an irregular domain (soluble region) into a regular computational domain via the usage of the indicator function so that the concentration flux across the interface due to adsorption and desorption processes can be termed as a singular source in the modified equation. Based on the immersed boundary formulation, we then develop a new conservative scheme for solving this coupled surface-bulk concentration equations which the total surfactant mass is conserved in discrete sense. A series of numerical tests has been conducted to validate the present scheme. As an application, we extend our previous work [M.-C. Lai, Y.-H. Tseng, H. Huang, An immersed boundary method for interfacial flows with insoluble surfactant, J. Comput. Phys. 227 (2008) 7279-7293] to the soluble case. The effects of solubility of surfactant on drop deformations in a quiescent and shear flow are investigated in detail. (C) 2013 Elsevier Inc. All rights reserved.
A Digital Reverse Current Self-calibration Technique in 90% High Efficiency Rectified Power Supply for Near Field Communication through Magnetic Field Induction
(2017-01-01)
Lin, Li-Chi
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Chen, Kuan-Yu
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Yang, Wen-Hau
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Huang, Ru-Yu
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Chen, Ke-Horng
it is crucial in near field communication (NFC) controllers for power source transferred from mutual induction of coils when the devices are battery-off. NFC devices can be operated at the condition of low battery or even battery-off due to the requirement of payment any time. Thus, the proposed wireless power transfer (WPT) power supply can have high efficiency due to the remove of reverse leakage current by the digital reverse current self-calibration (DRCS). NFC standards including A, B, and F can be continuously supplied by the WPT supply system. The WPT power supply with the DRCS technique was fabricated in 0.25 mu m CMOS process can rectify AC source from induction of magnetic field to unregulated DC voltage source and to supply power the NFC controller through low dropout regulator (LDR). Moreover, test chip achieves as high as 92% voltage conversion ratio and 89.4 % power conversion efficiency (PCE) due to reduction of unnecessary current loss.
A note on pressure accuracy in immersed boundary method for Stokes flow
(2011-06-01)
Chen, Kuan-Yu
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Feng, Ko-An
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Kim, Yongsam
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Lai, Ming-Chih
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應用數學系
In this short note, we provide a simplified one-dimensional analysis and two-dimensional numerical experiments to predict that the overall accuracy for the pressure or indicator function in immersed boundary calculations is first-order accurate in L(1) norm, half-order accurate in L(2) norm, but has O(1) error in L(infinity) Despite the pressure has O(1) error near the interface, the velocity field still has the first-order convergence in immersed boundary calculations. (C) 2011 Elsevier Inc. All rights reserved.
"A novel ""partial bypass"" concept to augment the performance of air-cooled heat exchangers"
(2012-09-01)
Wang, Chi-Chuan
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Chen, Kuan-Yu
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Liaw, Jane-Sunn
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Tseng, Chih-Yung
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機械工程學系
"This study proposes a novel ""partial bypass"" concept which facilitates the heat transfer augmentation without the pumping power penalty. The basic idea is to introduce bypass cold stream which bypasses the front part of the heat exchanger and mixes with the hot stream across the front part of the heat exchanger, and the mixed stream flows through the rear part of the heat exchanger. Through this concept, heat transfer performance at the front part is slightly reduced but the rear part is substantially increased. The concept can be implemented with either maintaining the same total flowrate, heat transfer rate but accompanies with a much lower pressure drop or it can be applied with the same pumping power but accompanies with a much higher heat transfer rate. It is found that the ""partial bypass"" concept is especially fruitful for a heat exchanger with a comparatively large number of transfer unit (NTU). The concept is especially helpful in the design of a deep tube bank operated at lower frontal velocity. For validating the proposed concept, the calculation is also compared with the experimental measurements, and good agreement amid the calculations and measurements are reported. (C) 2012 Elsevier Ltd. All rights reserved."
A novel "partial bypass" concept to augment the performance of air-cooled heat exchangers
(2012-09-01)
Wang, Chi-Chuan
;
Chen, Kuan-Yu
;
Liaw, Jane-Sunn
;
Tseng, Chih-Yung
;
機械工程學系
This study proposes a novel "partial bypass" concept which facilitates the heat transfer augmentation without the pumping power penalty. The basic idea is to introduce bypass cold stream which bypasses the front part of the heat exchanger and mixes with the hot stream across the front part of the heat exchanger, and the mixed stream flows through the rear part of the heat exchanger. Through this concept, heat transfer performance at the front part is slightly reduced but the rear part is substantially increased. The concept can be implemented with either maintaining the same total flowrate, heat transfer rate but accompanies with a much lower pressure drop or it can be applied with the same pumping power but accompanies with a much higher heat transfer rate. It is found that the "partial bypass" concept is especially fruitful for a heat exchanger with a comparatively large number of transfer unit (NTU). The concept is especially helpful in the design of a deep tube bank operated at lower frontal velocity. For validating the proposed concept, the calculation is also compared with the experimental measurements, and good agreement amid the calculations and measurements are reported. (C) 2012 Elsevier Ltd. All rights reserved.
Advertisement recommendation based on personal interests and ad push fairness
(2019-01-01)
Liu, Duen-Ren
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Liao, Yu-Shan
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Chung, Ya-Han
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Chen, Kuan-Yu
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資訊管理與財務金融系註：原資管所+財金所
Purpose - Online advertisement brings huge revenue to many websites. There are many types of online advertisement; this paper aims to focus on the online banner ads which are usually placed in a particular news website. The investigated news website adopts a pay-per-ad payment model, where the advertisers are charged when they rent a banner from the website during a particular period. In this payment model, the website needs to ensure that the ad pushed frequency of each ad on the banner is similar. Under such advertisement push rules, an ad-recommendation mechanism considering ad push fairness is required. Design/methodology/approach - The authors proposed a novel ad recommendation method that considers both ad-push fairness and personal interests. The authors take every ad's exposure time into consideration and investigate users' three different usage experiences in the website to identify the main factors affecting the interests of users. Online ad recommendation is conducted on the investigated news website. Findings - The results of the experiments show that the proposed approach performs better than the traditional approach. This method can not only enhance the average click rate of all ads in the website but also ensure reasonable fairness of exposure frequency of each ad. The online experiment results demonstrate the effectiveness of this approach. Originality/value - Existing researches had not considered both the advertisement recommendation and ad-push fairness together. With the proposed novel ad recommendation model, the authors can improve the ad click-through rate of ads with reasonable push fairness. The website provider can thereby increase the commercial value of advertising and user satisfaction.
An experimental study of the air-side performance of fin-and-tube heat exchangers having plain, louver, and semi-dimple vortex generator configuration
(2015-01-01)
Wang, Chi-Chuan
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Chen, Kuan-Yu
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Liaw, Jane-Sunn
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Tseng, Chih-Yung
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機械工程學系
In this study, a comparative study of the airside performance of fin-and-tube heat exchangers having plain, louver, and semi-dimple vortex generator (VG) are made. A total of eighteen samples are made and tested with the corresponding fin pitch (F-p) being 1.6 mm and 2.0 mm and the number of tube row (N) are 1, 2 and 4, respectively. Test results indicate that the heat transfer coefficient for N = 1 for louver fin geometry with a smaller fin pitch of 1.6 mm is higher than that of semi-dimple VG and plain fin geometry. For N = 1 with a larger fin pitch of 2.0 mm, the semi-dimple VG is marginally higher than that of louver fin geometry when the frontal velocity is lower than 2 m s(-1). However, the trend is reversed where the heat transfer coefficient for louver fin outperforms that of semi-dimple VG when the velocity is increased further. For the airside performance for N = 2 or N = 4, the heat transfer coefficients for louver fin geometry is about 2-15% higher than those of semi-dimple geometry. The difference is increased with the rising velocity and the results prevail for both fin pitches. However, the difference is smaller at a larger fin pitch due to the comparatively effectively swirled motion of the semi-dimple VG. The effect of the number of tube row on the heat transfer coefficients is negligible for louver fin geometry and is also rather small for semi-dimple VG. For the plain fin geometry, the effect of tube row is also small when N > 1. The heat transfer performance for N = 1 is different from N = 2 or N = 4 due to its inline configuration. (C) 2014 Elsevier Ltd. All rights reserved.
An Inkjet-Printed Flexible Non-Enzymatic Lactate Sensor for Clinical Blood Plasma Test
(2020-04-01)
Huang, Yi-Syuan
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Chen, Kuan-Yu
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Cheng, Yu-Ting
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Lee, Chih-Kuo
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Tsai, Hsiao-En
In this letter, we demonstrate a fully inkjet-printed electrochemical lactate sensor. The sensor is inkjet-printed on a flexible substrate, Kapton film, where silver nanoparticles (Ag NPs) are printed as conductive electrodes. The working and reference electrodes of the sensor are Ag NPs/NiO NPs/Polyurethane (PU) and Ag/AgCl(s)/PU layers respectively. The inkjet-printed PU film can not only prevent the annihilation of the Ag NPs resulting from the dissolution of Ag and the formation of AgCl in the phosphate-buffered saline (PBS) but also stabilize the lactic acid measurements by maintaining a potential variant within 2% at different lactate concentrations. The as-printed sensor exhibits a linear sensitivity of 8.86nA/mM/mm(2) (R=99.6%) in the range from 0.6 to 2.2 mM. Clinical blood plasma testing results show that the trends of lactic acid change in patients measured by the sensor are the same as the ones measured using the existing detection method, colorimetric assays, in a tertiary university-affiliated hospital.
An Online Activity Recommendation Approach based on the Dynamic Adjustment of Recommendation Lists
(2017-01-01)
Liu, Duen-Ren
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Chen, Kuan-Yu
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Chou, Yun-Cheng
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Lee, Jia-Huei
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資訊管理與財務金融系註：原資管所+財金所
This research investigates an online recommendation method for new types of online news websites. Cross-domain analysis on user browsing news and the attending activities is conducted to predict user preferences on activities based on non-negative Matrix Factorization (NMF) and Latent Dirichlet Allocation (LDA) topic model. A novel approach is proposed for the dynamic adjustment of recommendation lists in order to tackle the issue of limited recommendation layouts. The existing studies have not addressed this issue. The proposed approach is implemented on an online news website and evaluated for online recommendations. The experiment results demonstrate that our method can predict user preferences on recommended activities and enhance the effectiveness of recommendations.
Churn prediction and social neighbour influences for different types of user groups in virtual worlds
(2019-06-01)
Liu, Duen-Ren
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Liao, Hsiu-Yu
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Chen, Kuan-Yu
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Chiu, Yi-Ling
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資訊管理與財務金融系註：原資管所+財金所
In virtual worlds (VWs), users have more VW games alternatives, whereas VW companies consequently suffer from high customer turnover rate and low customer loyalty. Therefore, building a churn prediction model to facilitate subsequent churn management and customer retention is important. The churn behaviours and the impact of social neighbour influences to customer churn may be different for different types of users. Accordingly, we segment users into stable, unstable, and solitary user groups according to their social contact behaviours in VWs. Novel segmentation-based churn prediction approaches are proposed for churn prediction in VWs by building prediction models for each type of user groups and considering the effect of social neighbour influences for different user groups. The proposed approaches are evaluated by conducting experiments with a dataset collected from a VW platform. The experimental results show different churn prediction performances under different user groups. The segmentation-based churn prediction approaches perform better than do general approaches without considering user groups. Moreover, the results also reveal that social neighbour influences have a positive impact on stable and unstable users. The proposed work contributes to investigating the social neighbour influences on churn prediction for different types of user groups in VWs.
Contact Characteristics of Circular-Arc Curvilinear Tooth Gear Drives
(2009-08-01)
Wu, Yi-Cheng
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Chen, Kuan-Yu
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Tsay, Chung-Biau
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Ariga, Yukinori
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機械工程學系
In this paper, the circular-arc curvilinear tooth gear drive is proposed. The gear and pinion tooth surfaces are generated by two complemented circular-arc rack cutters with curvilinear tooth-traces. According to the theory of gearing, the mathematical model of the proposed gear is developed. The tooth contact analysis technique is utilized to investigate the kinematical errors of circular-arc curvilinear tooth gear drives under different assembly errors. Contact patterns of the circular-arc curvilinear tooth gear drive are simulated by the developed computer-aided tooth contact analysis programs and surface topology method. Numerical examples are presented to show the kinematical errors of the circular-arc curvilinear tooth gear set under different assembly conditions. Relations among the circular-arc tooth profile, curvilinear tooth-trace, contact ratio, contact pattern, and kinematical error are also demonstrated by numerical examples.
Design of an LED Spot Light System with a Projection Distance of 10 km
(2019-10-01)
Wu, Chi-Shou
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Chen, Kuan-Yu
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Lee, Xuan-Hao
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Lin, Shih-Kang
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Sun, Ching-Cherng
We designed a spot light system with an illumination range of 10 km. In the designed system, an appropriate white light-emitting diode (LED) was selected according to the exitance and injection power required. Subsequently, through a first-order optical design, the geometry of the lens and reflector was determined using geometrical calculation. Because the central illuminance of the projection spot of the reflector was 2.5 times that of the cover lens, we first considered the fabrication error of the reflector. According to the adjustment of the optimized distance between the white LED and reflector, we modified the design of the cover lens to fit the new location of the white LED. An LED spot light module containing 16 spot light units was used. The module's power injection was only 68.2 W. Because of the excellent performance of the designed system in terms of the divergence angle of the projection beam and maximum luminous intensity, which were 1.6 degrees and 2,840,000 cd, respectively, the projection distance of the LED spot light module was 3.37 Km, according to the ANSI regulation. Finally, a spot light system with nine modules and capable of achieving a projection distance of 10 km was successfully fabricated.
Distributed Systems Management for Enterprise Web Services Environment
(2009)
Lin, Chia-Feng
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Wu, Ruey-Shyang
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Yuan, Shyan-Ming
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Chen, Kuan-Yu
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資訊工程學系
In this research, we simplify Web Services Distributed Management (WSDM) interfaces developing effort. The interfaces are generated by program code that must be created during development. Developers do not have to understand all Web services standards. On the other hand, the management system should provide message flow oriented management atomically without modifying service code. Enter prise can control all flows and review them at any time. Enterprise can build a quickly, efficient and extensible management system in the Web services environment
Impact of Oxygen Vacancy on the Photo-Electrical Properties of In2O3-Based Thin-Film Transistor by Doping Ga
(2019-03-01)
Chen, Kuan-Yu
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Yang, Chih-Chiang
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Su, Yan-Kuin
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Wang, Zi-Hao
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Yu, Hsin-Chieh
In this study, amorphous indium gallium oxide thin-film transistors (IGO TFTs) were fabricated by co-sputtering. Three samples with different deposition powers of the In2O3 target, namely, sample A with 50 W deposition power, sample B with 60 W deposition power, and sample C with 70 W deposition power, were investigated. The device performance revealed that oxygen vacancies are strongly dependent on indium content. However, when the deposition power of the In2O3 target increased, the number of oxygen vacancies, which act as charge carriers to improve the device performance, increased. The best performance was recorded at a threshold voltage of 1.1 V, on-off current ratio of 4.5 x 10(6), and subthreshold swing of 3.82 V/dec in sample B. Meanwhile, the optical properties of sample B included a responsivity of 0.16 A/W and excellent ultraviolet-to-visible rejection ratio of 8 x 10(4). IGO TFTs may act as photodetectors according to the results obtained for optical properties.
Investigation of the semi-dimple vortex generator applicable to fin-and-tube heat exchangers
(2015-09-05)
Wang, Chi-Chuan
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Chen, Kuan-Yu
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Lin, Yur-Tsai
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機械工程學系
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Department of Mechanical Engineering
The present study examines the air side performance of the fin-and-tube heat exchangers having semi-dimple vortex generator or plain fin geometry. A total of eight samples are made and tested with the corresponding fin pitch (F-P) being 1.6 mm and 2.0 mm and the number of tube row (N) are 1 and 2. The inlet air flow direction is also being tested upon the proposed semi-dimple VG. Test results indicate that the heat transfer performance of the proposed semi-dimple VG with N = 1 at a smaller fin pitch of 1.6 mm is slightly higher than that of plain fin geometry. For N = 1 with a larger fin pitch of 2.0 mm, the semi-dimple VG is about 10% higher than that of plain fin geometry. The difference in heat transfer performance amid VG and plain fin geometry becomes more pronounced with N = 2 and is especially evident when F-P = 2.0 mm due to mixing contribution. In general, the difference between plain and semi-dimple geometry becomes more conspicuous at a larger fin pitch because of the comparatively effectively swirled motion. Both geometries show a dependence on fin pitch at N = 1 but the effect is almost negligible when N is increased to 2. The inlet air flow direction casts negligible influence on the heat transfer performance of semi-dimple VG. However, the friction factors for the opposite air flow operation is lower than that of normal operation, especially in low Reynolds number region. (C) 2014 Elsevier Ltd. All rights reserved.
Magnetization Reversal Characteristics in NiFe Elliptical Ring Arrays
(2010-06-01)
Chang, Liang-Juan
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Chen, Kuan-Yu
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Lin, Lu-Kui
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Yao, Yeong Der
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Lin, Pang
The magnetization reversal processes of single-layer nanoscale elliptical ring arrays are examined. The magnetic field was applied parallel or perpendicular to the long axis. The magnetization hysteresis loops showed a simultaneous-reversal single-step transition or two-step transition involving flux closure vortex states. For various aspect ratios and thicknesses, the transition between single-step and double-step magnetization reversals was measured to form phase diagrams. Simulations of the magnetization reversal behavior agreed with our results.
Mathematical Model and Tooth Undercutting of Curvilinear Gears with Circular-Arc tooth Profiles
(2009-06-01)
Wu, Yi-Cheng
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Chen, Kuan-Yu
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Tsay, Chung-Biau
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Lo, Jie-Shing
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機械工程學系
In this paper, the curvilinear gear with circular-arc tooth profiles is proposed. A mathematical model of the gear is developed based on the theory of gearing. The developed mathematical model of the proposed circular-arc curvilinear gear is then adopted to show the computer graph of gear teeth. Besides, the tooth undercutting is also investigated. Some numerical examples for tooth undercutting analysis of this type of gears are studied and illustrated. The initial tooth undercutting points and tooth undercutting line of the proposed curvilinear gear are investigated. In addition, the minimum number of gear teeth for tooth non-undercutting is also calculated.
Mathematical model and worm wheel tooth working surfaces of the ZN-type hourglass worm gear set
(2009-09-01)
Chen, Kuan-Yu
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Tsay, Chung-Biau
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機械工程學系
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Department of Mechanical Engineering
In this study, the hourglass worm gear set is composed of a ZN-type hourglass worm generated by straight-edged blade cutters and a ZN-type hourglass worm wheel generated by worm-type hourglass hob cutters. Mathematical model of the ZN-type hourglass worm gear set is derived based on its generation mechanism and the theory of gearing. According to the developed mathematical model of the gear set, computer graphs of the ZN-type hourglass worm and worm wheel are presented. The tooth working surface, boundary lines and contact lines of the ZN-type hourglass worm gear set under different lead angles, pressure angles and modules are investigated and compared with those of the ZA-type hourglass worm gear set. (C) 2009 Elsevier Ltd. All rights reserved.
Mathematical Model of the ZN-Type Worm Gear set with a Non-ninety-degree Crossing Angle and Undercutting Analysis of Worm Wheel Tooth Surfaces
(2009-08-01)
Chen, Kuan-Yu
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Tsay, Chung-Biau
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機械工程學系
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Department of Mechanical Engineering
A mathematical model of the ZN-type worm gear set with a non-ninety-degree crossing angle is developed based on the theory of gearing. The worm wheel is generated by a worm-type hob cutter, which is identical to the ZN-type worm. Based on the developed mathematical model of the worm gear set, a three-dimensional computer-aided graph of the ZN-type worm gear set with a non-ninety-degree crossing angle is presented. Tooth undercutting of the worm wheel is also investigated. Besides, undercutting lines of the worm wheel tooth surfaces are calculated and plotted. It is found that tooth undercutting is easier to occur at the middle region of the worm wheel tooth surface. In addition, pressure angle and crossing angle of the worm gear set play very important roles on the tooth undercutting.
Online recommendations based on dynamic adjustment of recommendation lists
(2018-12-01)
Liu, Duen-Ren
;
Chen, Kuan-Yu
;
Chou, Yun-Cheng
;
Lee, Jia-Huei
;
資訊管理與財務金融系註：原資管所+財金所
The flourishing of the Internet has increasingly promoted the rise of new types of online news websites with e-commerce portals. Online news websites provide specific information on such topics as lifestyle, fashion news, and a variety of other activities. The provision of online recommendation of activities associated with online news websites has the potential to attract more users and create more benefits. Such online recommendations represent an important online trend. Furthermore, dynamically adjusting recommendation lists to increase users' click-through rates is important for limited online recommendation layouts; however, existing studies have not addressed this online recommendation issue. This research proposes a novel approach for the dynamic adjustment of recommendation lists to tackle the issue of limited recommendation layouts, and then develops novel online recommendation methods. This research designs novel methods based on non-negative matrix factorization (NMF) and latent Dirichlet allocation (LDA) to predict user preferences for activities, using analysis of browsing news and attending activities. We propose a novel online activity recommendation approach, taking into consideration the interest scores and push scores, for dynamically adjusting the recommendation list. The Most Frequently Pushed (MFP) strategy gives priority to replacing the most frequently pushed activity, while the Not Frequently Clicked (NFC) strategy gives priority to replacing the not frequently clicked activity. We implement our proposed approach on an online news website and evaluate its online recommendation performance. The results of our experiment demonstrate that our proposed approach can enhance the effectiveness of recommendations. (C) 2018 Elsevier B.V. All rights reserved.