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收集所有交通大學研究人員與學生個人或團體所發表之各項學術著作，涵蓋期刊論文、教師專書、學位論文等項。;;Collections of Publications of NCTU Researchers and Students Like Journal Papers and Thesis.

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Author: search.filters.author.Chen, CHHas files: Yes

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Now showing 1 - 10 of 91
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    Defect Auger exciton dissociation and impact ionization in conjugated polymers
    (2001-09-15)
    Chen, CH
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    Meng, HF
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    物理研究所
    ;
    Institute of Physics
    We study theoretically the exciton dissociation and carrier generation in conjugated polymers via defect Auger process, in which the electron (hole) of the exciton drops into the deep defect level while the energy is released to the hole (electron) through Coulomb scattering. Contrary to the usual Auger process among free carriers at high densities, defect Auger process for excitons takes place independent of the exciton density, and is identified as the dominant mechanism of photocarrier generation for excitation below the band gap. The dissociation probability for each passage through the defect is found to be close to one for excitons with thermal velocity, consistent with the picture that exciton decay in oxidized polymers is controlled by diffusion on a chain with quenching centers. We also study the reverse process, i.e., defect impact ionization, in which excitons or free electron hole pairs are created via the impact of hot holes (electrons) on electrons (holes) in the defect level. Excitons are found to be produced predominantly for driving electric field in a window around 10(5) V/cm along the chain. Light emission under unipolar carrier injection is predicted.
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    Triplet-to-singlet exciton formation in poly(p-phenylene-vinylene) light-emitting diodes
    (2003-01-24)
    Lin, LC
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    Meng, HF
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    Shy, JT
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    Horng, SF
    ;
    Yu, LS
    The triplet to singlet exciton formation ratio in a MEH-PPV light-emitting diode is measured by comparing the triplet-induced absorptions with optical and electric excitations at the same singlet exciton density. The ratio is a strong universal decreasing function of the averaged electric field. Using 4 ns for singlet to triplet intersystem crossing time, the ratio is significantly larger than the spin-independent value 3 at intermediate field but is reduced to about 2 for higher field.
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    Induction of apoptosis in MCF-7 human breast cancer cells by phytochemicals from Anoectochilus formosanus
    (2004-01-01)
    Shyur, LF
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    Chen, CH
    ;
    Lo, CP
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    Wang, SY
    ;
    Kang, PL
    The antitumor activity of Anoectochilus formosanus Hayata (Orchidaceae), a popularly used folk medicine in the treatment of cancers in Asia, was investigated in MCF-7 human mammary carcinoma cells. Plant extracts of A. formosanus were observed to induce apoptosis of MCF-7 cells as evidenced by cell-morphological changes, an early redistribution of plasma membrane phosphatidylserine, and DNA content distribution studies. Bioactivity-guided fractionation of A. formosanus extracts produced a specific ethyl acetate (EA)-partitioned fraction in which apoptotic activity was enriched. The chemical profile and candidate index compounds of the active EA fraction were obtained using HPLC and various spectral analyses. Western blot analysis showed that upon treatment of MCF-7 cells with the EA fraction, cleavage of pro-caspases-8, -9, and -7, and poly(ADP-ribose) polymerase as well as significant release of mitochondrial cytochrome c into the cytosol were readily observed. Flow cytometry showed that the Fas ligand protein was overexpressed in EA-treated MCF-7 cells. Functional genomic studies indicated that specific genes related to cytoskeleton rearrangement, apoptotic signal transduction, and various transcription factors were differentially regulated in EA-treated MCF-7 cells. Putative apoptotic signaling pathways of MCF-7 cells in response to the EA extract of A. formosanus are proposed. Copyright (C) 2004 National Science Council, ROC and S. Karger AG, Basel.
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    Medicinal herb extract and a single-compound drug confer similar complex pharmacogenomic activities in MCF-7 cells
    (2004-01-01)
    Yang, NS
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    Shyur, LF
    ;
    Chen, CH
    ;
    Wang, SY
    ;
    Tzeng, CM
    Metabolite profiling and DNA microarray analysis of global gene expression profiles were employed to characterize the bioactivities of the herbal extract of Anoectochilus formosanus (AF), a popular folk medicine with anticancer activity, in MCF-7 cancer cells. The pharmacogenomic activities of this plant extract as a crude phytocompound mixture were compared to those conferred by the single-compound drug, plumbagin. A similar level of complexity in transcriptional regulation at the genomic level was observed for both AF extract- and plumbagin-treated MCF-7 cells, as revealed by the number of up- or downregulated genes as well as by the specific but distinct patterns found in the gene-clustering analysis. This finding offers evidence to support the search for fractionated medicinal herb extracts or phytocompound mixtures, in addition to single-compound drugs, as defined therapeutic agents. Copyright (C) 2004 National Science Council, ROC and S. Karger AG, Basel.
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    Numerical analysis of a burning droplet with internal circulation in a gravitational environment
    (1998-07-01)
    Huang, LW
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    Chen, CH
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    A theoretical analysis of steady burning droplets with internal circulation in the presence of normal atmosphere and gravity is presented. The normalized system governing the gas phase consists of the complete set of conservation equations in r-z coordinates and includes finite-rate global kinetics. For the liquid phase, it includes continuity and momentum conservation equations. Thermodynamic equilibrium is assumed along the gas-liquid interface, which is not stationary. A body-fitted grid generation technique is used to handle irregular boundaries. The parametric study is performed by changing droplet diameter. The induced convection flowfield is presented to demonstrate its interaction with the flame and the liquid flow motion. The predicted results show that there exists one, two, or three cells within the burning droplet, depending on its diameter. The occurrence of an extra cell is due to reverse flow in the gas phase generated by interaction of the induced flow and blowing velocity. Comparison with the case where internal flow is not considered, for a small droplet the effect of internal circulation on mass evaporation rate can be neglected. On the other hand the internal flow will increase the mass evaporation rate.
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    Method of solving triplets consisting of a singlet and air-spaced doublet with given primary aberrations
    (1998-10-01)
    Chen, CH
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    Shiue, SG
    ;
    Lu, MH
    ;
    光電工程學系
    ;
    Department of Photonics
    An effective algebraic algorithm is proposed as a computational tool for solving the thin-lens structure of a triplet which consists of a singlet and an air-spaced doublet. The triplet is required to yield specified amounts of lens power and four primary aberrations: spherical aberration, coma, longitudinal chromatic aberration and secondary spectrum. In addition, the air spacing is used to control the zonal spherical aberration and spherochromatism. The problem is solved in the following manner. First, the equations for power and chromatic aberration are combined into a quartic polynomial equation if the object is at a finite distance, or combined into a quadratic polynomial equation if the object is at infinity. The roots give the element powers. Second, the lens shapes are obtained by solving the quartic polynomial equation which is obtained by combining the equations of spherical aberration and coma. Since quartic and quadratic equations can be solved using simple algebraic methods, the algorithm is rapid and guarantees that all the lens forms can be found.
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    Influence of two-dimensional gas phase radiation on downward flame spread
    (1999)
    Lin, TH
    ;
    Chen, CH
    ;
    機械工程學系
    ;
    Department of Mechanical Engineering
    This work investigates how radiation heat transfer influences downward flame spread by presenting a gas phase radiation model, described by a two dimensional P-1 approximation method, to incorporate with the combustion model of Duh and Chen (1991). The parametric study is based on the variation of gravity, which changes the Damkohler number (Da) and radiation to conduction parameter (1/N-infinity) simultaneously. Comparing the results with the previous studies of Duh and Chen (1991) and Chen and Cheng (1994), which only considered the radiation effect in cross stream direction, the role of stream-wise radiation was identified. The stream-wise radiation contributes to reinforce the forward heat transfer rate subsequently increasing the flame spread rate. However, this model also provides more directional radiation loss than that of Chen and Cheng (1994) and, in doing so, draws more energy out from the flame to further reduce its strength. The results indicates that the effect of heat loss is greater than that of enhancing the upstream heat transfer since the flame spread rate in the present model is always lower than the one predicted by Duh and Chen (1991). Finally, a contour of the Planck mean absorption coefficient distribution is illustrated to demonstrate the effectiveness of gas radiation distribution. It reveals that the strongest radiation occurs near the pyrolyzing surface and the other significant one is in the plume region. A comparisons with available experimental data also given to evaluate the ability of predict in the present combustion model.
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    X-band balanced power amplifier using novel coupler with 50% power-added efficiency
    (1999-02-05)
    Tsao, KL
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    Chen, CH
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    Jou, CF
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    傳播研究所
    ;
    Institute of Communication Studies
    In this paper, we demonstrate an X-band balanced power amplifier using a novel microstrip line dc blocking impedance-transforming branch-line coupler (DCITBC). This novel coupler has the function of dc blocking, which can easily cascade two stages of an active circuit together. Therefore, we can reduce the cost and the circuit size. The measured power-added efficiency of this balanced power amplifier is 50% over the 9.8-10.2 GHz band, with an associated gain of 9 dB and 25 dBm output power. Additional important results are the superior performance of the harmonic suppression; the measured result shows a second harmonic below -40 dBc without an extra harmonic rejector. (C) 1999 John Wiley & Sons, Inc.