Browsing by Author "Wang, C. C."

Now showing 1 - 11 of 11

A Co-axial multi-tube heat exchanger applicable for a Geothermal ORC power plant
(2014-01-01)
Hsieh, J. C.
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Lee, Y. R.
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Guo, T. R.
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Liu, L. W.
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Cheng, P. Y.
The study proposes a Co-axial multi-tube heat exchanger (CMTHE) applicable to geothermal heat extraction. The heat exchanger is integrated with a 50 kW geothermal ORC power plant having a working fluid of R-245fa. Two field tests were performed to examine the system response of the ORC system subject to change of CMTHE. In case 1 where the flow rate in the shell-side of CMTHE is maintained, the pressure variation in the shell-side of CMTHE casts minor variations on heat extraction, ORC power generation, and ORC efficiency during the transient. Moreover, the effect of pressure has barely any influence of the final states of heat extraction, ORC power generation, and ORC efficiency. In case 2 where the pressure is preserved in the CMTHE, it is found that a decrease of flow rate in the CMTHE results in degradation of heat extraction, ORC power generation and ORC system efficiency. On the contrary, increasing the flow rate in the CMTHE leads to a rise of heat extraction, ORC power generation and ORC system efficiency. Unlike that in case 1, the effect of flow rate has a detectable effect on the final states of heat extraction, ORC power generation, and ORC efficiency. (C) 2014 Published by Elsevier Ltd.
Co-delivery of paclitaxel and cetuximab by nanodiamond enhances mitotic catastrophe and tumor inhibition.
(2015)
Chao, J. I.
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Liao, W. S.
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Lin, Y. W.
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Lin, J.
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Cheng, H. C.
Co-delivery of paclitaxel and cetuximab by nanodiamond enhances mitotic catastrophe and tumor inhibition.
(2015)
Chao, J. I.
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Liao, W. S.
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Lin, Y. W.
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Lin, J.
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Cheng, H. C.
Dynamic Analysis of a Motion Transformer Mimicking a Hula Hoop
(2011-02-01)
Lu, C. X.
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Wang, C. C.
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Sung, C. K.
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Chao, Paul C. P.
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電機工程學系
Hula-hoop motion refers to the spinning of a ring around a human body; it is made possible by the interactive force between the moving ring and the body. Inspired by the generic concept of hula-hoop motion, this study proposes a novel motion transformer design that consists of a main mass sprung in one translational direction and a free-moving mass attached at one end of a rod, the other end of which is hinged onto the center of the main mass. It is expected that the transformer is capable of transforming linear reciprocating motion into rotational motion. In addition, the transformer could be integrated with coils, magnets, and electric circuits to form a portable energy scavenging device. A thorough dynamic analysis of the proposed transformer system is conducted in this study in order to characterize the relationships between the varied system parameters and the chance of hula-hoop motion occurrence. The governing equations are first derived with Lagrange's method, which is followed by the search for steady-state solutions and the corresponding stability analysis via the homotopy perturbation method and the Floquet theory. Direct numerical simulation is simultaneously performed to verify the correctness of the approximate analysis. In this manner, the feasibility of the proposed design and the occurrence criteria of hula-hoop motion are assessed. [DOI: 10.1115/1.4001839]
Enhanced optical properties of InAs/GaAs quantum dots grown by radio-frequency hydrogen plasma-assisted molecular beam epitaxy
(2011-02-01)
Katkov, A. V.
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Chi, Jim
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Wang, C. C.
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Cheng, C.
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電子工程學系及電子研究所
Strong enhancement of photoluminescence (PL) efficiency has been observed in a GaAs/InAs quantum dots-in-a-well structure, grown with in situ irradiation of atomic hydrogen supplied by a radio-frequency hydrogen plasma source. The PL enhancement and wavelength position at room temperature have been found to be stable under extensive thermal annealing up to 630 degrees C in vacuum. As shown by the corresponding improvement of the barrier material, the possible mechanism for PL enhancement is the reduced nonradiative recombination in the barrier region by in situ passivation of defects while they are generated.
Excited Energy Attenuation Study Through Vibration Measurement and Spectrum Analysis
(2010)
Lin, S. Y.
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Chang, C. K.
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Chung, C. T.
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Hsu, F. C.
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Wang, C. C.
This paper presents the use of vibration measurement in conjunction with spectrum signal analysis to investigate the vibration phenomena and the dynamic response of the absorber system frame and rigid axle of a vehicle body under real road-driving conditions. Ford 1.6L sedan was selected as the vehicle body to carry out the experiments with different driving speeds. B&K PULSE dynamic signal analyzer was used to detect the vibration signal induced from the absorber system frame and rigid axle of the vehicle body in motion. The acquired on-line signals are then processed through the Fast Fourier Transform using the power spectrum density, the cepstrum method, and the overall analysis. The vibration energy attenuated from the absorber system is analyzed by comparing with that on the rigid axle excited from the road conditions corresponding to different driving speeds. Furthermore, the effects of various road conditions and driving speeds on oscillation of the vehicle body are studied. The corresponding results may be extensively treated as a guiding reference of the absorber system design and manufacturing for those vehicle manufacturing companies.
Geometry-dependent phase, stress state and electrical properties in nickel-silicide nanowires
(2016-05-25)
Wang, C. C.
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Lai, W. T.
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Hsiao, Y. Y.
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Chen, I. H.
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George, T.
We report that the geometry of single-crystalline Si nanowires (NWs) prior to salicidation at 500 degrees C is the key factor controlling the phase, stress state, and electrical resistivity of the resulting NixSiy NWs of width less than 100 nm. This is a radical departure from previous observations of a single phase formation for nickel silicides generated from the silicidation of bulk Si substrates. The phase transition from NiSi for large NWs (W-Si NW = 250-450 nm) to Ni2Si for small NWs (W-Si NW = 70-100 nm) is well correlated with the observed volumetric expansion and electrical resistivity variation with the NW width. For the extremely small dimensions of NixSiy NWs, we propose that the preeminent, kinetics-based Zhang and d\'Heurle model for salicidation be modified to a more thermodynamically-governed, volume-expansion dependent NixSiy phase formation. A novel, plastic deformation mechanism is proposed to explain the observed, geometry-dependent NixSiy NW phase formation that also strongly influences the electrical performance of the NWs.
Geotechnical site characterization for reservoir sediment
(2013)
Wang, C. C.
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Huang, A. B.
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Ho, Y. T.
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Lee, J. T.
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土木工程學系
The unusually strong typhoons and heavy rainfalls occurred recently in Taiwan have caused major landslides in many reservoir catch basins. The debris from these landslides eventually settled in the reservoir and turned into mud. From soil mechanics point of view, the mud in front of the dam is a very young, normally consolidated or under-consolidated soil. The engineering properties of the reservoir mud are important design parameters in the planning and design of schemes to remove the mud. Yet, our knowledge in this regard is very limited. For the major reservoirs in Taiwan, the mud is often under more than 40 m of water. How to conduct effective geotechnical site characterization under these circumstances is a challenge. The authors developed a differential pressure flat dilatometer (Delta DMT) and a piezo-penetrometer (Delta Pu) to facilitate in situ tests under water in a reservoir. A series of field Delta DMT and Delta Pu tests along with representative soil sampling were conducted at Tsengwen Reservoir in Southern Taiwan. The paper describes the techniques of differential pressure DMT and piezo-penetrometer tests, interpretation of available test data to obtain the engineering properties of the reservoir mud, and discusses implications in future site characterization of reservoir mud.
Optical property improvement of InAs/GaAs quantum dots grown by hydrogen-plasma-assisted molecular beam epitaxy
(2011-05-01)
Katkov, A. V.
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Wang, C. C.
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Chi, J. Y.
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Cheng, C.
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Gutakovskii, A. K.
An order-of-magnitude increase of photoluminescence (PL) efficiency at room temperature has been observed in the GaAs/InAs quantum dots (QDs)-in-a-well structure grown with in situ irradiation of atomic hydrogen supplied by a radio-frequency hydrogen-plasma source. The enhancement in PL intensity rapidly increases with the hydrogen flow rate and is stable with a variation of excitation power in the radio-frequency plasma source. Extensive thermal annealing of grown samples up to 634 degrees C did not show any significant degradation of photoluminescence intensity compared with the reference sample. The reduction of nonradiative recombination centers in the as-grown sample causes the greatly enhanced luminescence property. In addition to PL enhancement the authors observed that the H-assisted growth of InAs QDs has suppressed bimodal distribution of QD shape. In contrast to the hydrogen-plasma-assisted growth, irradiation by hydrogen in molecular form has a detrimental effect on the optical properties of similar structures. The high thermal stability of improved optical properties suggests that the formation of the defects which are responsible for nonradiative recombination channels is suppressed during H-assisted epitaxy although in situ defect passivation by atomic hydrogen cannot be completely ruled out. (C) 2011 American Vacuum Society. [DOI: 10.1116/1.3570870]
Simulation of Velocity Distribution and Pressure Drop in Every Channel in the Printed Circuit Heat Exchanger
(2013)
Lo, H. P.
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Hung, C. H.
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Wang, C. C.
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機械工程學系
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Department of Mechanical Engineering
This study examines the performance of printed circuit heat exchangers (PCHE) operated at high temperature subject to the influence of inlet conditions. Simulations are made with three cold plates and three hot plates with mass flow ranging from 0.469kg/h to 4.697kg/h. The inlet temperatures of the cold side and hot side are 200 degrees C and 700 degrees C, respectively. The size of the plate is 272x55x1.65mm with straight channel in the cold side and Z-Shape channel in the hot plate. The simulation is carried out for three cases (Case1: V-c = 5 m/s, T-c = 200 degrees C, V-h = 5 m/s, T-h = 700 degrees C; Case2: V-c = 5 m/s, T-c = 200 degrees C, V-h = 10 m/s, T-h = 700 degrees C; Case3: V-c = 1 m/s, T-c = 200 degrees C, V-h = 5 m/s, T-h = 700 degrees C). It is found that the effect of inlet velocity on the temperature performance is quite significant, and the heat transfer coefficient is related to the mass flow rate. The distribution of mass flow rate within the channel casts significant effect on the outlet temperature. The calculated results indicated the effectiveness epsilon (Case1) is 0.72 which is much higher than those of Case2 (0.704) and Case3 (0.574). Yet the second cold plate shows the maximum temperature difference and the pressure drop in all three cases of simulation.
The pivotal role of oxygen interstitials in the dynamics of growth and movement of germanium nanocrystallites
(2015-01-01)
Chen, K. H.
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Wang, C. C.
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Lai, W. T.
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George, T.
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Li, P. W.
We report an unusual "symbiotic" behavior of oxygen interstitials acting in concert with Ge and Si interstitials at high temperature inducing morphology changes and autonomous migration of Ge nanocrystallites within SiO2/Si3N4 layers. The Ge nanocrystallites were originally generated by the selective oxidation of SiGe nano-pillars grown and lithographically patterned over buffer Si3N4 layers on Si substrates. The coalescence and movement of these Ge nanocrystallites appear to be very sensitive to the presence and flux of oxygen interstitials especially at the Ge nanocrystallite/buffer Si3N4 interface. A range of different morphologies are observed for Ge nanocrystallites that are directly attributable to the influence of oxygen interstitial concentration and consequently the interstitial Si and Ge concentrations. In combination with Si and Ge interstitials, oxygen interstitials activate the coalescence of sparsely-distributed Ge nanocrystallites and concurrently their migration towards the source of Si interstitials, i.e. the buffer Si3N4 layers, through catalytically-enhanced local decomposition and subsequent oxidation of both the SiO2 and Si3N4 buffer layers. We also show that these symbiotic effects are "tunable" by increasing the Ge content of the SiGe nano-pillars. Dense distributions of Ge nanocrystallites generated from high Ge content SiGe nano-pillars remain static and they show no changes in their morphology possibly because oxygen interstitials are simply unable to penetrate these clusters and consequently incapable of inducing symbiotic Si and Ge interstitial generation.