Browsing by Author "Chen, Yen-Yu"

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A Macroscopic Signal Optimization Model for Arterials Under Heavy Mixed Traffic Flows
(2014-04-01)
Chen, Yen-Yu
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Chang, Gang-Len
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運輸與物流管理系註：原交通所+運管所
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Department of Transportation and Logistics Management
This paper presents a generalized signal optimization model for arterials experiencing multiclass traffic flows. Instead of using conversion factors for nonpassenger cars, the proposed model applies a macroscopic simulation concept to capture the complex interactions between different types of vehicles from link entry and propagation, to intersection queue formation and discharging. Since both vehicle size and link length are considered in modeling traffic evolution, the resulting signal timings can best prevent the queue spillback due to insufficient bay length and the presence of a high volume of transit or other types of large vehicles. The efficiency of the proposed model has been compared with the benchmark program TRANSYT-7F under both passenger flows only and multiclass traffic scenarios from modest to saturated traffic conditions. Using the measures of effectiveness of the average-delay-per-intersection approach and the total arterial throughput during the control period, our extensive numerical results have demonstrated the superior performance of the proposed model during congested and/or multiclass traffic conditions. The success of the proposed model offers a new signal design method for arterials in congested downtowns or megacities where transit vehicles constitute a major portion of traffic flows.
An Unsupervised Automated Essay-Scoring System
(2010-09-01)
Chen, Yen-Yu
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Liu, Chien-Liang
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Lee, Chia-Hoang
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Chang, Tao-Hsing
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資訊工程學系
BUFFER-OPTIMIZED IMPROVEMENT IN RF LOSS OF ALGAN/GAN HEMTS ON 4-INCH SILICON (111)
(2017-01-01)
Luong, Tien Tung
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Lumbantoruan, Franky
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Chen, Yen-Yu
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Ho, Yen-Teng
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Lin, Yueh-Chin
The effect of different buffer layers on the RF losses of GaN-based high-mobility-transistors (HEMTs) on Si substrate has been studied. It is found that the electron inversion layer induced by the residual tensile stress in AlN buffer is responsible for a dominant loss factor. It is first time such mechanisms of the RF loss of GaN/Si is discussed. It is proven that using a thin high-low-high temperature (HLH) AlN buffer reducing the tensile stress in AlN consequently reduces the RF loss.
Investigation of the low-temperature AlGaN interlayer in AlGaN/GaN/AlGaN double heterostructure on Si substrate
(2014-11-01)
Hsiao, Yu-Lin
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Wang, Yi-Jie
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Chang, Chia-Ao
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Weng, You-Chen
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Chen, Yen-Yu
A low-temperature (LT) AlGaN interlayer is inserted in the Al0.1Ga0.9N back barrier layer of an Al0.2Ga0.8N/GaN/Al0.1Ga0.9N double heterostructure grown on a 150mm Si substrate. It is found that the 21-nm-thick LT-AlGaN interlayer plays an important role in stress relaxation and dislocation reduction of the Al0.1Ga0.9N back barrier layer, especially for screw dislocation reduction. In addition, a buffer breakdown voltage higher than 600V is achieved, which is much higher than those of conventional heterostructures. These results demonstrate the effectiveness of combining the LT-AlGaN interlayer and the Al0.2Ga0.8N/GaN/Al0.1Ga0.9N double heterostructure on a Si substrate to increase the breakdown voltage for high-power applications. (C) 2014 The Japan Society of Applied Physics
Lateral Movement Decision Model for Powered Two-Wheelers in Taiwan
(2019-02-01)
Dong, Han
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Chen, Yen-Yu
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Cirillo, Cinzia
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Wong, K., I
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運輸與物流管理系註：原交通所+運管所
The maneuvering of powered two-wheelers (PTWs) is non-lane-based, and the interactions between PTWs and other vehicles in mixed traffic are complex. The behavior of PTWs, particularly in developing countries, is not the same as that of passenger cars, which has been studied for several decades. This study contributes to the existing literature on PTWs in several ways. A real-world microscopic vehicle trajectory database has been digitalized from a video clip for a four-lane urban arterial in Taipei (Taiwan). From a modeling perspective, a dynamic discrete choice model is proposed to capture the lateral-shifting behaviors of PTWs in mixed traffic conditions. The model considers not only the positions of all surrounding vehicles but also riders' perception of expected traffic conditions. The behavioral model is able to describe the sequential non-lane-based maneuvers of PTWs, including not following lane discipline, filtering, moving abreast of other vehicles in the same lane, oblique following, swerving, and overtaking from the same lane. The results indicate that a better model fit is obtained when taking into account the dynamic nature of the problem. The data and methods proposed have the potential to improve microscopic traffic simulation of mixed traffic with a large amount of PTWs. Practical applications are concerned with the improvement of road geometries and the definition of control strategies for mixed traffic flows.
RF loss mechanisms in GaN-based high-electron-mobility-transistor on silicon: Role of an inversion channel at the AlN/Si interface
(2017-07-01)
Luong, Tien Tung
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Lumbantoruan, Franky
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Chen, Yen-Yu
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Ho, Yen-Teng
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Weng, You-Chen
One of the epitaxial issues pertaining to the growth of AlGaN/GaN HEMTs on Si is the decrease of parasitic losses that can adversely impact the RF device performances. We characterized the microwave losses in coplanar waveguides (CPWs) on GaN-based high-electron-mobility-transistors (HEMTs) and their buffer layers on Silicon substrate, up to 40GHz. The RF losses depend not only on the crystalline quality but also on the residual tensile stress in AlN buffer, as well as its thickness. The mechanism of interfacial lossy channel induced by the piezoelectric field is discussed. Adopting a thin high-low-high temperature (HLH) AlN buffer can help to reduce the tensile stress leading to a reduction of RF losses. We suggest that a thinner p-type AlN and/or p-AlGaN-on-thin AlN near the interface can suppress the electron interfacial lossy channel, which helps the GaN-HEMT-on-HR Si to remain in a high frequency range and at high-temperature operation. (C) 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim