Browsing by Author "Wu, C. L."

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Carrier Distributed PON Using SSB-CS Signal for Rayleigh Backscattering Suppression
(2010)
Chow, C. W.
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Yeh, C. H.
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Liu, Y. F.
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Wang, C. H.
;
Wu, C. L.
We demonstrate using single-sideband-carrier-suppressed (SSB-CS) signal to suppress the Rayleigh-Backscattering (RB) in a carrier-distributed PON. The SSB signal is generated by a dual-parallel Mach-Zehnder modulator (DP-MZM). The split-ratio and reach are also investigated and analyzed.
CRITICAL CURRENT ANISOTROPY AND FLUX PINNING IN YBCO(001) AND YBCO(110) SUPERCONDUCTING THIN FILMS PREPARED BY KrF PULSED LASER ABLATION
(1993-03-01)
Juang, J. Y.
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Wu, K. H.
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Wang, S. J.
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Lai, T. C.
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Kao, R. T.
Direct transport critical current density (J(C)) measurements were performed on laser ablated high quality Y1Ba2Cu3O7 superconducting thin films with T-CO >= 90 K, J(C) approximate to 5x10(6) A/cm(2) at 77 K, and intentionally controlled film orientations to investigate the J(C) anisotropy and predominant pinning mechanisms in these films. It was found that, for films with (001) oriented normal to the substrate the field dependencies of the critical current densities J(C)(H) showed very different behaviors for different field orientations, indicating that the active pinning mechanisms may be different in two field directions. For the (110) oriented films with field applied normal to film surface, the pinning mechanism, as depicted from the scaling behavior of the global pinning force density, was found to follow the manifestation of surface core pinning. At zero field, however, the temperature dependence of J(C) revealed that, in all cases, the critical current was limited by flux creep with essentially the same creep kinetic factor expected for high-T-C cuprates. Detailed studies of the scaling behaviors of the pinning force density as functions of both field and temperatures for fields up to 7 Tesla will be presented and compared for different films and field orientations.
Identification of Time-Variant Modal Parameters Using Time-Varying Autoregressive with Exogenous Input and Low-Order Polynomial Function
(2009)
Huang, C. S.
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Hung, S. L.
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Su, W. C.
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Wu, C. L.
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土木工程學系
This work presents an approach that accurately identifies instantaneous modal parameters of a structure using time-varying autoregressive with exogenous input (TVARX) model. By developing the equivalent relations between the equation of motion of a time-varying structural system and the TVARX model, this work proves that instantaneous modal parameters of a time-varying system can be directly estimated from the TVARX model coefficients established from displacement responses. A moving least-squares technique incorporating polynomial basis functions is adopted to approximate the coefficient functions of the TVARX model. The coefficient functions of the TVARX model are represented by polynomials having time-dependent coefficients, instead of constant coefficients as in traditional basis function expansion approaches, so that only low orders of polynomial basis functions are needed. Numerical studies are carried out to investigate the effects of parameters in the proposed approach on accurately determining instantaneous modal parameters. Numerical analyses also demonstrate that the proposed approach is superior to some published techniques (i.e., recursive technique with a forgetting factor, traditional basis function expansion approach, and weighted basis function expansion approach) in accurately estimating instantaneous modal parameters of a structure. Finally, the proposed approach is applied to process measured data for a frame specimen subjected to a series of base excitations in shaking table tests. The specimen was damaged during testing. The identified instantaneous modal parameters are consistent with observed physical phenomena.
Rayleigh Noise Mitigation Using Single-Sideband Modulation Generated by a Dual-Parallel MZM for Carrier Distributed PON
(2010-06-01)
Wang, C. H.
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Chow, C. W.
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Yeh, C. H.
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Wu, C. L.
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Chi, S.
Hybrid passive optical networks (PONs) with a centralized light source (CLS) could be a promising solution for the next-generation PON. However, the network with a loop-back architecture will give rise to interferometric noise caused by Rayleigh backscattering (RB). Here, we propose and demonstrate a colorless optical networking unit (ONU) using a dual-parallel Mach-Zehnder modulator (DP-MZM) to mitigate RB noise in a hybrid wavelength-division-multiplexing-time-division-multiplexing PON with CLS. Both dominant contributions of RB, carrier RB and signal RB, are experimentally characterized, for the first time, when using a DP-MZM as a reflective ONU. In addition, the split-ratio of a long-reach PON using the DP-MZM-based ONU is also investigated and analyzed, showing RB noise can be efficiently reduced.
Recycling of spent filter backwash water using coagulation-assisted membrane filtration: effects of submicrometre particles on membrane flux
(2010)
Huang, Chihpin
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Lin, Jr-Lin
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Wu, C. L.
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Chu, C. P.
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環境工程研究所
Membrane separation technology has been widely used for recycling of spent filter backwash water (SFBW) in water treatment plant. Membrane filtration performance is subject to characteristics of the particles in the SFBW. A bench-scale microfiltration (MF) coupled with pre-coagulation was set up to evaluate the recovery efficiency of SFBW. Effect of particle size distribution and zeta potential of the coagulated SFBW on the membrane filtration as well as the coagulation strategies were investigated. Pore clogging was more severe on the membrane with 1.0 mu m pore size than on the membrane with 0.5 mu m pore size due to the fact that submicrometre particles are dominant and their diameters are exactly closed to the pore size of the MF membrane. Pre-settling induced more severe irreversible fouling because only the submicrometre particles in the water become predominant after settling, resulting in the occurrence of more acute pore blocking of membrane. By contrast, pre-coagulation mitigates membrane fouling and improves membrane flux via enlarging particle size on membrane surface. The variations of zeta potential in response to coagulant dosing as well as fractal dimension were also compared with the performance of the subsequent filtration. The result showed that pre-coagulation induced by charge neutralization at the optimum dosage where the zeta potential is around zero leads to the optimal performance of the subsequent membrane filtration for SFBW recycling. At such condition, the fractal dimension of coagulated flocs reached minimum.
Studies of OFDM Signal for Broadband Optical Access Networks
(2010-08-01)
Chow, C. W.
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Yeh, C. H.
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Wang, C. H.
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Wu, C. L.
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Chi, S.
Using orthogonal-frequency-division-multiplexing (OFDM) format for passive optical network (PON) is a subject of great interest for recent research works. OFDM signal has high spectral efficiency, high tolerance to the fiber chromatic dispersion and the high flexibility on both multiple services provisioning and dynamic bandwidth allocation. In this paper we study the use of OFDM signals for optical access networks, including carrier distributed PON, heterogeneous optical wired/wireless network and a 100 Gb/s OFDM-PON. We first quantify the performance of the OFDM signal when subjected to the noise produced by two different Rayleigh backscattering (RB) components that are present in the carrier-distributed PON. Then, based on these results, we also study the possibility of using OFDM for signal remodulation in a long-reach (LR)-PON. We propose carrier-distributed OFDM PONs using a dual-feeder fiber architecture and wavelength-shifting to mitigate the RB noise. Afterwards, we propose heterogeneous optical wired/wireless access networks, combining 10 Gb/s PON and 10 Gb/s OFDM radio-over-fiber (ROF) network. Finally, we propose a 100 Gb/s OFDM-PON using subcarrier multiplexing (SCM).