Browsing by Author "Chou, YH"

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A distributed-feedback antenna oscillator
(2000-05-01)
Wang, SL
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Chou, YH
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
In this paper, a new design of the active transmitting antenna array, called the distributed-feedback antenna oscillator, is proposed. The active array is formed by serially connecting several unit cells to a closed loop. Each unit cell contains an amplifier and a two-port antenna, with an overall insertion gain larger than 0 dB and a phase delay equal to a multiple of 360 degrees. The signal traveling on the loop is amplified and radiated in each unit cell. The radiation fields from all the antennas are then combined in free space. A four-element feedback antenna oscillator operating at 10 GHz is demonstrated by using two-port aperture-coupled microstrip antennas. Simulation results show that multiple oscillation modes with different frequencies and different radiation beams may be excited in the antenna oscillator. By experiment, it is found that each oscillation mode can be built by tuning the biases of the oscillator. The measured radiation pattern for each mode agrees very well with the predicted one. For a single-mode operation with a broadside pattern, bandstop filters of a simple geometry are designed and embedded in the oscillator to suppress the unwanted oscillation modes. Finally, the influence of the bias condition on the radiation power of the single-mode oscillator is investigated.
A new phase-shifterless scanning technique for a two-element active antenna array
(1999-02-01)
Chou, YH
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Chung, SJ
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電信工程研究所
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Institute of Communications Engineering
In this paper, a new phase-shifterless beam-scanning technique is proposed and demonstrated for a two-element active antenna array. An internal control line with an embedded amplifier is introduced in the array to provide another injection signal other than the mutual-coupling injection signal between antennas. By mixing the effects of the signals from the control Line and mutual coupling, the phase difference between antennas is adjusted by gradually changing the amplifier bias on the control line. A dynamic analysis is presented to explain the scanning mechanism. The measured results showed that, when the control-line amplifier was biased from the off state to fully on state, the radiation pattern of the array was varied smoothly from the out-of-phase mode (with 180 degrees radiation phase difference) to the in-phase mode (with 0 degrees phase difference). During the scanning process, the antenna oscillators were stably locked, with the deviation of the locked frequency lower than 0.35%.
A real-time local signal control methodology for alleviating incident-induced traffic congestion on arterials
(2002)
Sheu, IJB
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Chou, YH
;
Weng, MC
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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 real-time local signal control method which serves to alleviate incident-induced traffic congestion on the roadway between two adjacent intersections. The proposed approach includes two major parts: (1) a discrete-time non-linear stochastic model which denotes the time-varying relationships of lane traffic state variables and control variables under conditions of lane-blocking incidents, and (2) a realtime control algorithm for dynamically predicting control variables. To generate efficiently traffic data used in model tests, we employed the Paramics microscopic traffic simulator, which is developed to model and analyze ITS traffic flow conditions. The preliminary test results indicate the superiority of the proposed real-time signal control method in comparison with fixed-time signal control modes which are presently used at the study site. It Is expected that this study can stimulate research on Incident management, and extend to network-wide incident-responsive traffic control for the development of advanced traffic management systems (ATMS).(1).
A three-port 180-degree antenna hybrid: Design and applications
(2001-09-01)
Chou, YH
;
Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
In this paper, a novel three-port antenna structure, named 180 degrees antenna hybrid, is proposed and demonstrated. This structure is composed of a Wilkinson power divider with the isolation resistor replaced by an aperture-coupled patch antenna. The equivalent series impedance of the antenna can be adjusted to the required one by properly choosing the dimensions of the patch and the coupling aperture. When a signal is fed to the balanced port of this antenna hybrid, the power is equally split, with equal phases, to the two unbalanced ports. No power is radiated out from the antenna. In the other hand, a signal received from the antenna will be split with equal power but 180 phase difference to the two unbalanced ports. The balanced port is an isolation port. The measurement results showed good agreement with the characteristics to be designed. Three applications of this 180 degrees antenna hybrid are introduced, that is, a balanced mixer, an active transmitting antenna, and a dual-radiation-mode antenna array. The balanced mixer was constructed with diodes directly mounted on the two unbalanced ports of the antenna hybrid. The LO signal is fed from the balanced port and RF signal is received from the antenna. The active transmitting antenna was implemented with feedback configuration. The route from one of the unbalanced port to the balanced port of the antenna hybrid was used as the feedback path. A locking signal may be injected from the other unbalanced port. Finally, through a three-quarter-wavelength microstrip line, the balanced port of the antenna hybrid was connected to another aperture-coupled patch antenna to form a dual-radiation-mode antenna array. The in-phase and out-of-phase radiation patterns of this two-element array can be obtained from two unbalanced ports of the antenna hybrid, respectively.
An integrated logistics operational model for green-supply chain management
(2005-07-01)
Sheu, JB
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Chou, YH
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Hu, CC
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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 an optimization-based model to deal with integrated logistics operational problems of green-supply chain management (G-SCM). In the proposed methodology, a linear multi-objective programming model is formulated that systematically optimizes the operations of both integrated logistics and corresponding used-product reverse logistics in a given green-supply chain. Factors such as the used-product return ratio and corresponding subsidies from governmental organizations for reverse logistics are considered in the model formulation. Results of numerical studies indicate that using the proposed model, the chain-based aggregate net profits can be improved by 21.1%, compared to the existing operational performance in the particular case studied. © 2004 Elsevier Ltd. All rights reserved.
An integrated logistics operational model for green-supply chain management
(2005-07-01)
Sheu, JB
;
Chou, YH
;
Hu, CC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
This paper presents an optimization-based model to deal with integrated logistics operational problems of green-supply chain management (G-SCM). In the proposed methodology, a linear multi-objective programming model is formulated that systematically optimizes the operations of both integrated logistics and corresponding used-product reverse logistics in a given green-supply chain. Factors such as the used-product return ratio and corresponding subsidies from governmental organizations for reverse logistics are considered in the model formulation. Results of numerical studies indicate that using the proposed model, the chain-based aggregate net profits can be improved by 21.1%, compared to the existing operational performance in the particular case studied. © 2004 Elsevier Ltd. All rights reserved.
An optional operation organization of Chiang Kai-Shek International Airport rail link project in Taiwan
(2005)
Hsu, YC
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Chou, YH
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Chen, YN
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運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
With CKS International Airport remains one the important gateways to Taiwan, the CKS International Airport rail link system would serve as a most crucial mass transportation tool that would poise to excel the competitiveness of the international airport and its adjacent metropolises. In light of which, how best to locate an optimal operating organization that offers a sustainable management would emerge as a pressing concern. Taking into account urban transit and airport rail link service, the study, upon analyzing using the FAHP and TOPSIS methods, has chosen the Taipei Mass Rapid Transit Corporate alternative as the optimized alternative, together with the alternative of setting up a new private-run company as the second best alternative. As derived from analyses conducting on various decision-making groups, an operator with actual transportation operations would emerge as a crucial determining factor to become the future airport rail link operator. The study findings are not only intended as references to government departments but also to recommend the government to expeditiously finalize the operator as an urgent mission to facilitate subsequent implementation in light of the complexity in the rail system's interfacing logistical implementation.
Analysis of a grating metal structure with broad back-scattering field pattern for applications in vehicle collision avoidance system
(2002-01-01)
Chou, YH
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Lin, SJ
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
In this paper, grating metal structures with broad and flat back-scattering field patterns are studied for possible applications in a vehicle collision avoidance system. The two-dimensional TE scattering of a planar grating structure and a curved grating structure are analyzed at a frequency of 77 GHz. For the planar structure, the method of moment together with Floquet's theorem is used to solve the induced current and the resultant back-scattering field. Based on the results of the planar structure, the scattering field of the curved grating structure is obtained by using a perturbation method. The influence on the field pattern of the curvature as well as other structure parameters, such as the width and geometry of each period in the grating structure, is investigated.
Applications of semiconductor nanoparticles in electron transfer, energy transfer and metal ion recognition.
(2004-08-22)
Chou, YH
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Chiu, HT
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Chen, CY
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Cheng, CT
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Chou, PT
Chemical vapor deposition of the hafnium oxynitride for use as HIGH-K materials in microelectronic devices.
(2004-08-22)
Chuang, SH
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Chou, YH
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Chiu, HT
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應用化學系
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Department of Applied Chemistry
Design of a beam-switching active microstrip antenna array
(1998-05-01)
Chou, YH
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Chung, SJ
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電信工程研究所
;
Institute of Communications Engineering
An active microstrip antenna array with dual switching beams were developed and demonstrated. The array contained several active antennas and an extra amplifier-embedded coupling (microstrip) line. Two injection-locking signals were used in the design, that is, the free-space mutual coupling between antennas and the injection signal on the coupling line tapped from the first oscillator in the array. By turning on and off the amplifier on the line, these two signals dominated in turn, producing two radiation modes with different main beams. A three-element H-plane array and a two-element E-plane array were designed and measured. Both of the arrays had an out-of-phase radiation mode when the amplifier was turned off, and had an in-phase mode when the amplifier was on. Also, clean frequency spectra and good radiation patterns were measured, which demonstrated the validity of the present design.
Metalorganic chemical vapor deposition of tungsten carbonitride films by bis(tertbutylimido)bis(diethylamido)tungsten.
(2002-04-07)
Chuang, SH
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Chiu, HT
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Chou, YH
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Chang, YH
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Chen, SF
Potassium ion recognition by 15-crown-5 functionalized CdSe/ZnS quantum dots in H2O
(2006-01-21)
Chen, CY
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Cheng, CT
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Lai, CW
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Wu, PW
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Wu, KC
Based on 15-crown-5 functionalized CdSe/ZnS quantum dots (QDs), we report a novel fluorogenic sensor to probe K+ ions in H2O; recognition of K+ can be achieved via the Forster type of energy transfer between two different color QDs, so that [K+] of the order of 10(-6) M can be promptly detected.
Spectroscopy and femtosecond dynamics of type-II CdSe/ZnTe core-shell semiconductor synthesized via the CdO precursor
(2004-07-29)
Chen, CY
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Cheng, CT
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Yu, JK
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Pu, SC
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Cheng, YM
CdSe/ZnTe type-II quantum dots (QDs) synthesized via the CdO precursor are reported. Spectroscopic and femtosecond dynamic measurements reveal that the rate of photoinduced electron/hole spatial separation decreases with increases in the size of the core, and it is independent of the thickness of the shell in the CdSe/ZnTe QDs. The results are consistent with the binding strength of the electron and hole confined at the center of CdSe. The correlation between the core/shell size and the electron/hole spatial separation rate resolved in this study may provide valuable information for applications where rapid photoinduced carrier separation followed by charge transfer into a matrix or electrode is crucial, such as in photovoltaic devices.
Spectroscopy and femtosecond dynamics of type-II CdTe/CdSe core-shell quantum dots
(2006-01-16)
Chou, PT
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Chen, CY
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Cheng, CT
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Pu, SC
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Wu, KC
Syntheses of CdTe/CdSe type-II quantum dots (QDs) using CdO and CdCl2, as precursors for core and shell, respectively, are reported. Characterization was made via near-IR interbond emission, transmission electron microscopy (TEM), energy dispersive spectroscopy (EDX), and X-ray diffraction (XRD). Femtosecond fluorescence upconversion measurements on the relaxation dynamics of the CdTe core (in CdTe/CdSe) emission and CdTe/CdSe inter-band emission reveal that as the size of the core increases from 5.3, 6.1 to 6.9 nm, the rate of photoinduced electron separation decreases from 1.96, 1.44 to 1.07 X 10(12) s(-1). The finite rates of the initial charge separation ore tentatively rationalized by the small electron-phonon coupling, causing weak coupling between the initial and charge-separated states.
Stochastic modeling and real-time prediction of incident effects on surface street traffic congestion
(2004-05-01)
Sheu, JB
;
Chou, YH
;
Chen, A
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運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Modeling and real-time prediction of incident-induced time-varying lane traffic states, e.g., mandatory lane-changing fractions, queue lengths, and delays are vital to investigate the time-varying incident effects on traffic congestion in both the spatial and temporal domains. This paper presents a discrete-time nonlinear stochastic model to characterize the time-varying relationships of specified lane traffic states under the condition of lane-blocking incidents on surface streets. The proposed stochasti: model is composed of four types of equations: (1) recursive equations, (2) measurement equations, (3) delay-aggregation equations, and (4) boundary constraints. In addition, a recursive estimation algorithm is developed for real-time prediction of the specified time-varying lane traffic states. The proposed method Is tested with simulated data generated using the Paramics traffic simulator. The preliminary tests indicate the capability of the proposed method to estimate incident effects on surface street traffic congestion in real time. We also expect that this study can provide real-time incident-related traffic information with benefits both for understanding the impact of incidents on non-recurrent traffic congestion of surface streets, and for developing advanced incident-responsive traffic control and management technologies. (C) 2003 Elsevier Inc. All rights reserved.
Stochastic system modeling and optimal control of incident-induced traffic congestion
(2003-09-01)
Sheu, JB
;
Chou, YH
;
Weng, MC
;
運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
Incident-induced traffic congestion is a critical issue in formulating urban traffic congestion problems, and also a major cause that contributes to the invalidity of traffic signal control. This paper presents a prototype of real-time local signal control method, and explores its applicability in alleviating incident-induced traffic congestion on the roadway between two adjacent intersections for incident management. The architecture includes two major parts: (1) formulating time-varying lane traffic state variables and control variables under conditions of lane-blocking incidents with a discrete-time non-linear stochastic model, and (2) developing a real-time control algorithm for predicting dynamically control variables. To generate efficiently traffic data used in model tests, we employed the Paramics microscopic traffic simulator, which is developed to model and analyze ITS traffic flow conditions. According to the measures of two proposed space-based incident-impact indexes, the preliminary test results indicate the superiority of the proposed real-time signal control method in comparison with fixed-time signal control modes which are currently used at the study site. We do expect that this study can stimulate research on incident management, and extend to network-wide incident-responsive traffic control for the development of advanced traffic management systems (ATMS). (C) 2003 Elsevier Ltd. All rights reserved.
Syntheses and photophysical properties of type-II CdSe/ZnTe/ZnS (core/shell/shell) quantum dots
(2005)
Cheng, CT
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Chen, CY
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Lai, CW
;
Liu, WH
;
Pu, SC
Syntheses of CdSe/ ZnTe/ ZnS (core/shell/shell) type-II quantum dots (QDs) are reported. Structural characterization was made via TEM, EDX, XPS and XRD. Photophysical properties were investigated via the interband emission (CdSe -> ZnTe) and its associated quantum efficiency as well as relaxation dynamics. In comparison to the weak emission (Phi(f) similar to 4 x 10(-3) in toluene) of CdSe/ ZnTe (3.9/ 0.5 nm), capping ZnS (0.4 nm in thickness) enhances the CdSe -> ZnTe interband emission by similar to 30 fold (Phi(f) similar to 0.12), whereas the peak wavelength shifts only slightly to the red. By encapsulating dihydrolipoic acid ( DHLA), water-soluble CdSe/ ZnTe/ ZnS QDs were also prepared, and they exhibited an interband emission at y930 nm with an emission yield of similar to 0.1. Femtosecond pulse excitation (lambda(ex) similar to 1200 nm) measurement estimated a two- photon absorption cross section, sigma, of similar to 70 x 10(-50) cm(4) s photon(-1) for DHLA-capped CdSe/ ZnTe/ ZnS in water, supporting its suitability for the use as near-infrared (NIR) dyes in biomedical imaging.
Type-II CdSe/CdTe/ZnTe (core-shell-shell) quantum dots with cascade band edges: The separation of electron (at CdSe) and hole (at ZnTe) by the CdTe layer
(2005-12-01)
Chen, CY
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Cheng, CT
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Lai, CW
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Hu, YH
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Chou, PT
The rational design and synthesis of CdSe/CdTe/ZnTe (core-shell-shell) type-II quantum dots are reported. Their photophysical properties are investigated via the interband CdSe -> ZnTe emission and its associated relaxation dynamics. In comparison to the strong CdSe (core only) emission (lambda(max) approximate to 550 nm, Phi(f) approximate to 0.28), a moderate CdSe -> Cd Te emission (lambda(max) approximate to 1026 nm, Phi(f) approximate to 1.2 x 10(-3)) and rather weak CdSe -> Zn Te interband emission (lambda(max) approximate to 1415 nm, Phi(f) approximate to 1.1 x 10(-5)) are resolved for the CdSe/CdTe/ ZnTe structure (3.4/1.8/1.3 nm). Capping CdSe/CdTe with ZnTe results in a distant electron-hole separation between CdSe (electron) and ZnTe (hole) via an intermediate CdTe layer In the case of the CdSe/CdTe/ ZnTe structure, a lifetime as long as 150 ns is observed for the CdSe -> Zn Te (1415 nm) emission. This result further indicates an enormously long radiative lifetime of approximate to 10 ms. Upon excitation of the CdSe/CdTe/ Zn Te structure, the long-lived charge separation may further serve as an excellent hole carrier for catalyzing the redox oxidation reaction.