Browsing by Author "Lee, SH"

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A CPW-to-Slotline active gunn diode leaky wave antenna
(1998)
Lee, SH
;
Wu, JJ
;
Peng, ST
;
Hu, CC
;
Jou, CF
A X-band coplanar waveguide (CPW) to slotline couple feeding active microstrip leaky wave antenna using Gunn-diode oscillator as source is demonstrated. The method to excite the first higher order mode of the microstrip leaky wave antenna is to put the CPW-to-slotline transition underneath the middle of the microstrip line, and the oscillator circuit and radiating element are separated by a ground plane. The measured angle of the maximum beam direction of active antenna is at 72 degrees for the active Gunn oscillator frequency of 11.218 GHz; This prototype of active leaky wave antenna feeding by Gunn diode oscillator with CPW-to-slotline structure can be easily scaled up to millimeter wave frequency region.
A Gunn-diode active leaky-wave frequency scanning antenna
(1998-01-01)
Lee, SH
;
Jou, CK
;
Lee, CP
;
Hu, CC
;
Wu, JJ
A frequency tunable active leaky-wave scanning antenna using Gunn-diode voltage control oscillator (VCO) as source is developed. The frequency tuning controlled by changing either the varactor diode de bias or the Gunn diode de bias is demonstrated. The measured scanning angle of active antenna is close to 15 degree as the Gunn VCO frequency tuned from 12.58GHz to 12.98GHz. To excite the first higher order mode of the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the middle line of the microstrip leaky wave antenna. This is a prototype of frequency scanning antenna using two terminal device, which can be easily scaled up to millimeter wave frequency region.
A new method for generating fuzzy rules from numerical data for handling classification problems
(2001-08-01)
Chen, SM
;
Lee, SH
;
Lee, CH
;
資訊工程學系
;
Department of Computer Science
Fuzzy classification is one of the important applications of fuzzy logic. Fuzzy classification Systems are capable of handling perceptual uncertainties, such as the vagueness and ambiguity involved in classification problems. The most important task to accomplish a fuzzy classification system is to rnd a set of fuzzy rules suitable for a specific classification problem. In this article, we present a new method for generating fuzzy rules from numerical data for handling fuzzy classification problems based on the fuzzy subsethood values between decisions to be made and terms of attributes by using the level threshold value alpha and the applicability threshold value beta, where alpha is an element of [0, 1] and beta is an element of [0, 1]. We apply the proposed method to deal with the "Saturday Morning Problem,'' where the proposed method has a higher classification accuracy rate and generates fewer fuzzy rules than the existing methods.
Comparisons on properties and growth mechanisms of carbon nanotubes fabricated by high-pressure and low-pressure plasma-enhanced chemical vapor deposition
(2004-11-01)
Lin, CH
;
Lee, SH
;
Hsu, CM
;
Kuo, CT
;
材料科學與工程學系
Effects of plasma pressure and the presence of nitrogen on growth of carbon nanotubes (CNTs) and their properties were studied by using microwave plasma chemical vapor deposition (MPCVD) (pressure=600-3300 Pa) and electron cyclotron resonance chemical vapor deposition (ECR-CVD) (pressure=0.3-0.6 Pa) systems. CH4/H-2 and CH4/N-2 were used as source gases, and Co as the catalyst. The structures and properties of CNTs were characterized by using field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), Raman spectra, and field emission I-V measurements. The results show that. CNTs made by higher plasma pressure system have a higher growth rate (typically 1-3 mum/min), smaller tube diameter, better field emission properties, and better tube quality. The growth rate is related to the availability of carbon source. The morphology change from spaghetti-like to well-aligned CNTs is discussed in terms of directed ions. The change in field emission properties is reasoned in terms of geometric enhancement factor and screening effect for different tube morphologies. The presence of nitrogen plasma can have the following effects: increasing tube diameter, increasing straightness of CNTs, forming of bamboo-like CNTs, deterioration of field emission properties, and shifting of Raman peak toward lower-frequency side (or increasing residual tensile stress). (C) 2004 Elsevier B.V. All rigths reserved.
Compositional disordering of InGaAs/GaAs heterostructures by low-temperature-grown GaAs layers
(1996-01-15)
Tsang, JS
;
Lee, CP
;
Lee, SH
;
Tsai, KL
;
Tsai, CM
Compositional disordering of InGaAs/GaAs superlattices using a low-temperature-grown GaAs cap layer (LT-GaAs) by molecular beam epitaxy has been studied. The disordering of the superlattice was verified by photoluminescence and double-crystal x-ray rocking curve measurements. The Ga-vacancy-enhanced interdiffusion due to the presence of LT-GaAs was found to be the disordering mechanism. Diffusion equations and the Schrodinger's equation were solved numerically to obtain the composition profile and the transition energies in the disordered quantum well, respectively. The simulated energy shifts for samples under different annealing conditions agreed very well with the experimental results. The calculated effective diffusivity for the In-Ga interdiffusion has an activation energy of 1.63 eV, which is smaller than the activation energy 1.93 eV, for intrinsic interdiffusion. The diffusivity for the enhanced In-Ga interdiffusion due to the presence of LT-GaAs is about two orders of magnitude larger than the intrinsic In-Ga diffusivity. (C) 1996 American Institute of Physics.
Coplanar waveguide to coplanar strips fed active leaky-wave antenna
(1998-01-01)
Hu, CC
;
Jou, CF
;
Wang, CJ
;
Lee, SH
;
Wu, JJ
A new active coplanar waveguide (CPW) to coplanar strips (CPS) fed microstrip leaky-wave antenna is developed, which integrated with a Gunn diode as active source. The CPW-CPS balun is used to excite the first higher order mode of the microstrip leaky-wave antenna. The active leaky-wave antenna has maximum EIRP of 20.4 dBm at 9.759 GHz. The Gunn oscillator frequency is controlled by tuning the Gunn DC bias and the beam scanning is demonstrated. The measured scanning angle agrees with the prediction, it is close to 12 degrees as the oscillator frequency tuned from 9.84 GHz to 9.61 GHz. The coplanar structure allow easy integration of many solid-state devices. It is suitable for monolithic power combining and millimeter wave applications.
Coplanar waveguide to coplanar strips-fed active leaky-wave antenna
(1998-12-05)
Hu, CC
;
Jou, CF
;
Wang, CJ
;
Lee, SH
;
Wu, JJ
A new active coplanar waveguide (CPW) to coplanar ships (CPS)-fed microstrip leaky-wave antenna is developed, which is integrated with a Gunn diode as an active source. The CPW-CPS balun is used to excite the first higher order mode of the microstrip leaky-wave antenna. The active leaky-wave antenna has a maximum EIRP of 20.4 dBm at 9.759 GHz. The Gunn oscillator frequency is controlled by tuning the Gunn de bias, and the beam scanning is demonstrated. The measured scanning angle agrees with the prediction; it is close to 12 degrees as the oscillator frequency is tuned from 9.84 to 9.61 GHz. The coplanar structure allows easy integration of many solid-state devices. It is suitable for monolithic power combining ann millimeter-wave applications. (C) 1998 John Wiley & Sons, Inc.
Coplanar waveguide to coplanar strips-fed active leaky-wave antenna
(1998-12-05)
Hu, CC
;
Jou, CF
;
Wang, CJ
;
Lee, SH
;
Wu, JJ
A new active coplanar waveguide (CPW) to coplanar ships (CPS)-fed microstrip leaky-wave antenna is developed, which is integrated with a Gunn diode as an active source. The CPW-CPS balun is used to excite the first higher order mode of the microstrip leaky-wave antenna. The active leaky-wave antenna has a maximum EIRP of 20.4 dBm at 9.759 GHz. The Gunn oscillator frequency is controlled by tuning the Gunn de bias, and the beam scanning is demonstrated. The measured scanning angle agrees with the prediction; it is close to 12 degrees as the oscillator frequency is tuned from 9.84 to 9.61 GHz. The coplanar structure allows easy integration of many solid-state devices. It is suitable for monolithic power combining ann millimeter-wave applications. (C) 1998 John Wiley & Sons, Inc.
Electrochemical study on screen-printed carbon electrodes with modification by iron nanoparticles in Fe(CN)(6)(4-/3-) redox system
(2005-10-01)
Lee, SH
;
Fang, HY
;
Chen, WC
;
Lin, HM
;
Chang, CA
The remarkable enhancement of electron transfer on screen-printed carbon electrodes (SPCEs) with modification by iron nanoparticles (Fe-nano), coupled with Fe(CN)(6)(4-/3-) redox species, was characterized with an increase of electroactive area (A(ea)) at electrode surface together with a decrease of heterogeneous. electron transfer rate constant (k degrees) in the system. Hence, Fe-nano-Fe(CN)(6)(3-) SPCEs with deposition of glucose oxidase (GOD) demonstrated a higher sensitivity to various glucose concentrations than Fe(CN)(6)(3-)/GOD-deposited SPCEs. In addition, an inhibited diffusion current from cyclic voltammograms was also observed with an increase in redox concentration and complicated the estimation of A(ea). Further analysis by the electrochemical impedance method, it was shown that this effect might be resulted from the electrode surface blocking by the products of activated complex decomposition.
Fabrication and optical property of GaSe thin films grown by pulsed laser deposition
(2003-08-01)
Lee, SH
;
Hsu, YK
;
Hsu, HC
;
Chang, CS
;
Hsieh, WF
The highly oriented (001) GaSe film on c-cut sapphire (0001) was successfully fabricated by pulsed laser deposition. As growth temperature decreases from 550degreesC to 375degreesC, the structure of films changes from cubic zinc-blende Ga2Se3 phase to GaSe phase. The growth temperature of the critical transition from Ga2Se3 phase to GaSe phase is around 500degreesC . From atomic force microscope (AFM) results, it is observed that the growth process of GaSe film is in the manner of layer plus island growth. Besides, the optimal growth conditions of as-grown GaSe film were obtained at a substrate temperature of 400degreesC and laser energy density of 11.7J/cm(2). When the thickness of films goes beyond 800 Angstrom, the stress will be released and the thickness of 1200 Angstrom results in an optimal GaSe film. Furthermore, the indirect bound exciton emission and the recombination via impurity levels or structural defects were observed from low-temperature photoluminescence measurement.
Field study, design, and catalyst cost of selective catalytic reduction process
(2001-08-01)
Bai, HL
;
Lee, SH
;
Lin, CH
;
Hwang, JF
;
Hsieh, CL
A pilot TiO2/V2O5 based selective catalytic reduction (SCR) system was installed in a glass manufacturing factory. The effects of important operation parameters such as the reaction temperature, space velocity, and inlet NH3/NOx molar ratio on the NO removal were evaluated. It was observed that >1 mol of NO, is reacted for every 1 mol of NH3 injected. This observation is different from that reported in the literature for laboratory experiments. The key design parameter values of the reaction rate and the NH3 adsorption rate were determined based on results of the pilot tests using a theoretical SCR model developed by the same research group. The SCR model is a simple analytical solution that accounts for the simultaneous mass transfer and chemical reaction of an SCR reactor. The model results were compared to field data of NOx conversion efficiency and NH3 slip, and they were in reasonable agreement. The required catalyst volume and the cost of catalysts were then determined with the assistance of the design model.
Photodissociation dynamics of formyl fluoride (HFCO) at 193 nm: Branching ratios and distributions of kinetic energy
(2005-08-15)
Lee, SH
;
Wu, CY
;
Yang, SK
;
Lee, YP
;
應用化學系
Following photodissociation of formyl fluoride (HFCO) at 193 nm, we detected products with fragmentation translational spectroscopy utilizing a tunable vacuum ultraviolet beam from a synchrotron for ionization. Among three primary dissociation channels observed in this work, the F-elimination channel HFCO -> HCO+F dominates, with a branching ratio similar to 0.66 and an average release of kinetic energy similar to 55 kJ mol(-1); about 17% of HCO further decomposes to H+CO. The H-elimination channel HFCO -> FCO+H has a branching ratio similar to 0.28 and an average release of kinetic energy similar to 99 kJ mol(-1); about 21% of FCO further decomposes to F+CO. The F-elimination channel likely proceeds via the S-1 surface whereas the H-elimination channel proceeds via the T-1 surface; both channels exhibit moderate barriers for dissociation. The molecular HF-elimination channel HFCO -> HF+CO, correlating with the ground electronic surface, has a branching ratio of only similar to 0.06; the average translational release of 93 kJ mol(-1), similar to 15% of available energy, implies that the fragments are highly internally excited. Detailed mechanisms of photodissociation are discussed. (c) 2005 American Institute of Physics.
Regular and chaotic dynamic analysis and control of chaos for a vertically vibrating and rotating circular tube containing a particle
(2004)
Ge, ZM
;
Lee, SH
;
Lee, CI
;
機械工程學系
;
Department of Mechanical Engineering
The paper presents the detailed nonlinear dynamic analysis of a vertically vibrating and rotating circular tube containing a particle. By adding a harmonic periodic vibration and damping force on this nonlinear system, enriched dynamic behaviors of the nonlinear system are presented. By applying the Lyapunov direct method, the conditions of stability and instability of relative equilibrium position can be determined. A codimension one bifurcation analysis for the autonomous system is carried out near the degenerate point. It is found that Hopf bifurcation occurs in the system by center manifold theory. And by applying various numerical results, such as phase portrait, Poincare map, time history and power spectrum analysis, the behaviors of the periodic and chaotic motion can be presented. The effects of the change of parameters in the system can be found in the bifurcation diagrams and parameter diagram. Further, by using Lyapunov exponents and Lyapunov dimensions we can verify the chaotic behavior. Finally, seven methods, namely, the adding of constant torque, the adding of periodic torque, the adding of impulse, delayed feedback control, adaptive control, bang-bang control, optimal control, are use to control chaos effectively to periodic orbit.
Series quartz crystal sensor for remote bacteria population monitoring in raw milk via the Internet
(2006-02-15)
Chang, KS
;
Jang, HD
;
Lee, CF
;
Lee, YG
;
Yuan, CJ
A remote monitoring system based on a piezoelectric quartz crystal (SPQC) sensor was developed for the determination of the bacteria population in raw milk. The system employs the Windows XP server operating system, and its programs for data acquisition, display and transmission were developed using the LabVIEW 7.1 programming language. The circuit design consists of a circuit with a piezoelectric quartz crystal (SPQC) and a pair of electrodes. This system can provide dynamic data monitoring on a web-page via the Internet. Immersion of the electrodes in a cell culture with bacteria inoculums resulted in a change of frequency caused by the impedance change due to microbial metabolism and the adherence of bacteria on the surface of the electrodes. The calibration curve of detection times against density of bacteria showed a linear correlation coefficient (R-2 = 0.9165) over the range of 70-10(6) CFU ml(-1). The sensor could acquire sufficient data rapidly (within 4 h) and thus enabled real-time monitoring of bacteria growth via the Internet. This system has potential application in the detection of bacteria concentration of milk at dairy farms. (c) 2005 Elsevier B.V. All rights reserved.
Varactor-tuned Gunn diode voltage controlled oscillator antenna array
(1997-10-01)
Lee, SH
;
Jou, CF
;
Lee, CP
;
Hu, CC
;
傳播研究所
A simple varactor tuned X-band Gunn diode VCO antenna array which is strongly coupled has been demonstrated. These arrays have the advantages of simple biasing circuit, no resistors required to eliminate multimode problem and suitable for monolithic integration circuit. Preliminary results show a maximum tuning range of 47MHz for 1x1 array and 170MHz for 2x2 array. In order to solve power combining heating problem, we move the backside metal forward and it becomes a microstrip form. The measured frequency and radiation patterns of these grid arrays agree very well with theoretical calculations.
Varactor-tuned Gunn diode voltage controlled oscillator antenna array
(1997-10-01)
Lee, SH
;
Jou, CF
;
Lee, CP
;
Hu, CC
;
電子工程學系及電子研究所
A simple varactor tuned X-band Gunn diode VCO antenna array which is strongly coupled has been demonstrated. These arrays have the advantages of simple biasing circuit, no resistors required to eliminate multimode problem and suitable for monolithic integration circuit. Preliminary results show a maximum tuning range of 47MHz for 1x1 array and 170MHz for 2x2 array. In order to solve power combining heating problem, we move the backside metal forward and it becomes a microstrip form. The measured frequency and radiation patterns of these grid arrays agree very well with theoretical calculations.