Browsing by Author "Huang, HY"

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A novel algorithm for computing the 2D split-vector-radix FFT
(2004-03-01)
Huang, HY
;
Lee, YY
;
Lo, PC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper presents a novel two-dimensional split-vector-radix fast-Fourier-transform (2D svr-FFT) algorithm. The modularizing feature of the 2D svr-FFT structure enables us to explore its characteristics by identifying the local structural property. Each local module is designated as a DFT (non-DFT) block if its output corresponds to DFT (non-DFT) values. The block attribute (DFT or non-DFT) directs the algorithm to construct the local module. We will show that the distribution of DFT blocks can be illustrated by the Sierpinski triangle-a class of fractals generated by IFS (iterated function system). The finding of the Sierpinski-triangle structural property enables us to actually implement the 2D svr-FFT algorithm. To the best of our knowledge, the 2D svr-FFT has never been realized in software. The computational efficiency of the proposed algorithm is considerably improved in comparison with that provided by Matlab. (C) 2003 Elsevier B.V. All rights reserved.
Analysis of chlorophenoxy acid herbicides by cyclodextrin-modified capillary electrophoresis
(1996-09-20)
Hsieh, YZ
;
Huang, HY
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
In this study, we developed a capillary electrophoresis method involving cyclodextrins to separate seven chlorophenoxy acid herbicides and their enantiomers. The cavity size and the concentration of cyclodextrins heavily influenced the migration time of individual herbicides. The peak resolution also varied with different concentration ratios of cyclodextrins. Adding 4 mM alpha-cyclodextrin and 1 mM beta-cyclodextrin in the buffer was found to produce the optimum experimental condition. The herbicides examined in this study could be successfully separated within 7 min; meanwhile, the two pairs of enantiomers could also be completely resolved. The calibration lines' correlation coefficients for the separation conditions were all above 0.996. The dynamic range of the analysis of seven herbicides was at least two orders, from 1 ppm to 100 ppm. Analyzing the seven herbicides by capillary electrophoresis posed the advantages of a high resolution, high separation efficiency and good reproducibility. By combining with a C-18 disk preconcentration method, the herbicides' detection limits in the environmental water were below 1 ppb.
Analysis of Puerariae radix and its medicinal preparations by capillary electrophoresis
(1998-04-03)
Wang, CY
;
Huang, HY
;
Kuo, KL
;
Hsieh, YZ
;
應用化學系
This study presents a high-performance capillary electrophoresis (CE) method to analyze five constituents of Puerariae radix, an important crude herb used in Chinese medicine. Puerarin, daidzin, daidzein, genistein and biochanin A are the bioactive constituents of Puerariae radix. Herein, those analytes were successfully separated within 6 min using a pH 10.1 borax-NaOH buffer. The effects of pH value and concentration of the running buffer on the separation of the fie analytes were also examined. The relative standard deviations of the analytes' migration times were less than 0.38% under the optimized separation conditions. Notably, the correlation coefficients of the analytes' linear calibration graphs exceeded 0.998. Moreover, the amounts of the five constituents in three different Puerariae radix samples were determined by the CE method with a relatively simple extraction procedure. (C) 1998 Elsevier Science B.V.
Antioxidant role of human haptoglobin
(2004-08-01)
Tseng, CF
;
Lin, CC
;
Huang, HY
;
Liu, HC
;
Mao, SJT
Human plasma haptoglobin (Hp) is classified according to three phenotypes: Hp 1-1, 2-1, and 2-2 attributed by their two common alleles 1 and 2. Clinically, the 2-2 phenotype is associated with the risk of cardiovascular diseases and diabetes mellitus in patients. In this study, we demonstrate that Hp is an extremely potent antioxidant, which directly protects low density lipoprotein from Cu2+-induced oxidation. Its potency was markedly superior to probucol (one of the most potent antioxidants). Ranking of the IC50 of antioxidant activity was as follows: Hp 1-1 > Hp 2-1 > Hp 2-2 > probucol > vitamin E. Blockage of disulfide linkages between Hp subunits, not only abolished the alpha-helical content but also diminished the ability of Hp to form a complex with hemoglobin. The modified Hp subunits exerted almost 4 times greater antioxidant activity than that of native Hp. To investigate the antioxidant role of Hp on the cellular level, the cDNA of Hp 1-1 was cloned, introduced into the pcDNA3.0 vector which contains the cytomega lovirus promoter and transfected into chinese hamster ovary (CHO)-K1 cells. Following transfection, CHO cells were able to express Hp 1-1 protein and significantly (p < 0.001) elevated cell tolerance against oxidative stress. Transfected cells showed 2-fold higher resistance to hydrogen peroxide exposure for 24 h compared to control cells. Thus, Hp plays a provocative antioxidant role as demonstrated by our in vitro and ex vivo studies.
Determination of cinnamaldehyde, cinnamic acid, paeoniflorin, glycyrrhizin and [6]-gingerol in the traditional Chinese medicinal preparation Kuei-chih-tang by cyclodextrin-modified micellar electrokinetic chromatography
(1997-05-30)
Huang, HY
;
Kuo, KL
;
Hsieh, YZ
;
應用化學系
;
Department of Applied Chemistry
This study presents a cyclodextrin-modified micellar electrokinetic chromatography (CD-MEKC) technique with a multi-wavelength detection method to determine specific components in Kuei-chih-tang. Kuei-chih-tang, a Chinese medicinal preparation, is composed of five crude herbs, i.e., Cinnamomi ramulus, Paeoniae radix, Glycyrrhizae radix, Zingiberis rhizoma and Zizyphi fructus. The effects of SDS and gamma-cyclodextrin on the analytes' migration behavior were examined. The selected components were successfully separated within 10 min using a pH 10.0 borax-NaOH buffer containing 20 mM SDS and 2 mM gamma-cyclodextrin. The correlation coefficients of the linear calibration graphs for the analytes exceeded 0.993. Moreover, the optimized CD-MEKC method was employed to analyze four different Kuei-chih-tang samples. (C) 1997 Elsevier Science B.V.
Determination of puerarin, daidzein, paeoniflorin, cinnamic acid, glycyrrhizin, ephedrine, and [6]-gingerol in Ge-gen-tang by micellar electrokinetic chromatography
(1997-09-30)
Huang, HY
;
Hsieh, YZ
;
應用化學系
;
Department of Applied Chemistry
This paper presents a micellar electrokinetic chromatography (MEKC) method with diode-array detection to analyze for seven major components in the traditional Chinese medicinal preparation of Ge-gen-tang. Those analytes were successfully separated within 9 min using a pH 9.0 berate buffer containing 20 mM Sodium dodecyl sulfate at 30 degrees C. Experimental results indicated that the relative standard deviations of the analytes' migration times were <0.43% and the correlation coefficients of the analytes' linear calibration graphs exceeded 0.996. The quantities of the seven components in four different Ge-gen-tang samples were determined by the MEKC method coupled with a relatively simple extraction method. (C) 1997 Elsevier Science B.V.
Determination of saikosaponins by micellar electrokinetic capillary chromatography
(1997-01-24)
Hsieh, YZ
;
Huang, HY
;
應用化學系
;
Department of Applied Chemistry
In this study, we examine the feasibility of determining saikosaponins a, b1, b2, c and d, i.e., the bioactive components in Bupleuri Radix, using the micellar electrokinetic capillary chromatography technique. Results obtained from using different anion surfactants, bile salt or sodium dodecyl sulfate (SDS), are also compared. By using bile salt as a pseudostationary phase, the baseline separation of saikosaponins is observed; however, the detection limit is unfavorable. Whereas the baseline resolution of saikosaponins is achieved after adding gamma-cyclodextrin in the SDS running buffer. In addition, another separating method is developed with the mixed micellar system of SDS and Brij 35 containing gamma-cyclodextrin. The contents of saikosaponins in traditional Chinese medicinal prescriptions, such as Sheau Chair Hwu Tang, Bupleuri Radix plant and Chair Hwu San are analyzed by one of the above methods. The entire separation can be completed within 9 min by these methods. The R.S.D. values of the migration times are all below 1%. Moreover, the detection limits of saikosaponins vary from 7 to 33 mu g/ml.
Determination of saikosaponins by micellar electrokinetic capillary chromatography
(1997-01-24)
Hsieh, YZ
;
Huang, HY
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
In this study, we examine the feasibility of determining saikosaponins a, b1, b2, c and d, i.e., the bioactive components in Bupleuri Radix, using the micellar electrokinetic capillary chromatography technique. Results obtained from using different anion surfactants, bile salt or sodium dodecyl sulfate (SDS), are also compared. By using bile salt as a pseudostationary phase, the baseline separation of saikosaponins is observed; however, the detection limit is unfavorable. Whereas the baseline resolution of saikosaponins is achieved after adding gamma-cyclodextrin in the SDS running buffer. In addition, another separating method is developed with the mixed micellar system of SDS and Brij 35 containing gamma-cyclodextrin. The contents of saikosaponins in traditional Chinese medicinal prescriptions, such as Sheau Chair Hwu Tang, Bupleuri Radix plant and Chair Hwu San are analyzed by one of the above methods. The entire separation can be completed within 9 min by these methods. The R.S.D. values of the migration times are all below 1%. Moreover, the detection limits of saikosaponins vary from 7 to 33 mu g/ml.
Effects in carrier dynamics of Isolectronic In doped in GaN films grown by metalorganic vapor phase epitaxy
(2000)
Huang, HY
;
Shu, CK
;
Lin, WC
;
Liao, KC
;
Chuang, CH
Time-resolved photoluminescence spectra were used to characterize isoelectronically doped GaN:In films. Our results indicate that the recombination lifetime of donor-bound-exciton transition of pure GaN exhibits strong dependence on temperature. When In is doped into GaN, the recombination lifetime decreases sharply from 68 ps to 30 ps, irregardless of measured temperature and In doping concentration. The cause for this appearance is not clear at present. It might be related to the isoelectronic In impurity itself in GaN, which creates shallow energy levels that predominate the recombination process.
Effects of the process parameters on austenitic stainless steel by TIG-flux welding
(2006-05-01)
Huang, HY
;
Shyu, SW
;
Tseng, KH
;
Chou, CP
;
機械工程學系
The effects of the process parameters of TIG (tungsten inset gas)-flux welding on the welds morphology, angular distortion, ferrite content and hot cracking in austenitic stainless steel were investigated. Autogenous TIG welding process was applied to the type 304 stainless steel through a thin layer of activating flux to produce a bead on plate welded joint. TiO2, SiO2, Fe2O3, Cr2O3, ZnO and MnO2 were used as the activating fluxes. The experimental results indicated that the TIG-flux welding can increase the weld depth/width ratio and reduce the HAZ (heat affected zone) range, and therefore the angular distortion of the weldment can be reduced. It was also found that the retained ferrite content within the TIG-flux welds is increased, and has a beneficial effect in reducing hot cracking tendency for stainless steels of the austenitic type weld metals. A plasma column constriction increases the current density at the anode spot and then a substantial increase in penetration of the TIG-flux welds can be obtained.
Evaluation of TIG flux welding on the characteristics of stainless steel
(2005-09-01)
Huang, HY
;
Shyu, SW
;
Tseng, KH
;
Chou, CP
;
機械工程學系
The aim of the present study was to investigate the effect of specific oxide fluxes on the surface appearance, weld morphology, retained delta ferrite content, hot cracking susceptibility, angular distortion and mechanical properties obtained with the tungsten inert gas (TIG) process applied to the welding of 5 mm thick austenitic stainless steel plates. An autogenous gas tungsten arc welding process was applied to stainless steels through a thin layer of activating flux to produce a bead on plate welded joint. The MnO2 and ZnO fluxes used were packed in powdered form. The experimental results indicated that the 80% MnO2 - 20% ZnO mixture can give full penetration and also a satisfactory surface appearance for type 304 stainless steel TIG flux welds. TIG welding with MnO2 and/or ZnO can increase the measured ferrite number in welds, and tends to reduce hot cracking susceptibility in as welded structures. It was also found that TIG flux welding can significantly reduce the angular distortion of stainless steel weldments.
Formation of self-organized GaN dots on Al0.11Ga0.89N by alternating supply of source precursors
(2004-06-15)
Ke, WC
;
Huang, HY
;
Ku, CS
;
Yen, KH
;
Lee, L
The self-organized GaN dot structure is successfully grown on a slightly lattice-mismatched Al0.11Ga0.89N epilayer using flow-rate modulation epitaxy (FME) growth technique. From the variation of dot density with growth temperature, we can observe that the GaN dot growth is controlled predominately by the surface diffusion of Ga adatoms at substrate temperatures below 915degreesC and by re-evaporation at higher temperatures. Because of the special alternating gas supply feature in FME, during the Ga source step, it is the Ga metal that is deposited on the underlying Al0.11Ga0.89N layer. This is because of the large lattice mismatch of 41.8% between the Ga metal (4.51 Angstrom) and Al0.11Ga0.89N (3.18 Angstrom). We consider that the GaN dot growth in our study is mainly through the Volmer-Weber growth mode, not the commonly used Stranski-Krastanow growth mode.
Growth temperature reduction for isoelectronic As-doped GaN
(2003-03-01)
Lee, WH
;
Huang, HY
;
Chen, WC
;
Lee, CF
;
Chen, WK
As-doped GaN films were grown at different temperatures by atmospheric metalorganic chemical vapor deposition. A higher electron Hall mobility, narrower line width in photoluminescence, and longer spatial correlation length of the filmes were obtainable at low growth temperatures compared to undoped GaN grown at the same temperatures as a result of isoelectronic As-doping.
High-performance capillary electrophoretic analysis of synthetic food colorants
(1998-03-01)
Kuo, KL
;
Huang, HY
;
Hsieh, YZ
;
應用化學系
;
Department of Applied Chemistry
A high-performance capillary electrophoresis method with diode-array detection has been developed for analysis of synthetic food colorants. The influence of buffer composition on the separation of the food colorants was examined, as were the effects of alpha-, beta- and gamma-cyclodextrins on analyte migration behavior. Eight food colorants were completely separated within 10 min using pH 9.5 borax - NaOH buffer containing 5 mM beta-cyclodextrin. Experimental results indicate that the relative standard deviations of analyte migration times were < 0.88% under the optimized separation condition. Correlation coefficients of the linear calibration plots of the analytes exceeded 0.998. The method was suitable for determination of the quantities of synthetic food colorants in ice cream bars and fruit soda drinks.
Interconnect accelerating techniques for sub-100-nm gigascale systems
(2004-11-01)
Huang, HY
;
Chen, SL
;
電機學院
;
College of Electrical and Computer Engineering
This work describes new circuits called capacitor coupling trigger and capacitor coupling accelerator (CCA) circuits used to reduce the long interconnect RC delay in sub-100-nm processes. The proposed circuits use capacitors to split the output driving paths to eliminate the short-circuit current and thus improve the signal transition time. Besides, the capacitor coupling technique is applied to adjust the gate threshold voltage of the proposed circuits and isolate the input signal from the output driving transistors. The proposed circuits are faster than the prior circuits. Furthermore, the CCA can be applied to bi-directional interface, multiports bus, field-programmable gate array interconnections, and complex dynamic logic circuits.
Isoelectronic As doping effects on the optical characteristics of GaN films grown by metalorganic chemical-vapor deposition
(2000-10-30)
Huang, HY
;
Lin, WC
;
Lee, WH
;
Shu, CK
;
Liao, KC
We have studied the As doping effects on the optical characteristics of GaN films by time-integrated photoluminescence and time-resolved photoluminescence. When As is incorporated into the film, the localized defect levels and donor-acceptor pair transition become less resolved. The recombination lifetime of neutral-donor-bound exciton (I-2) transition in undoped GaN increases with temperature as T-1.5. However, the I-2 recombination lifetime in As-doped GaN first decreases exponentially from 98 to 41 ps between 12 and 75 K, then increases gradually to 72 ps at 250 K. Such a difference is related to the isoelectronic As impurities in GaN, which generate nearby shallow levels that dominate the recombination process. (C) 2000 American Institute of Physics. [S0003-6951(00)01941-0].
Luminescence intensity reduction in Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy
(2001-04-01)
Shu, CK
;
Chen, HH
;
Lee, WH
;
Pan, YC
;
Huang, HY
Photoluminescence dynamic responses of a heavily Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy have been investigated. As the probe power density increased from 2.5 to 925 W/cm(2), a Mg-related emission band shifted from 2.82 to 3.16 eV revealing characteristics of donor-acceptor pair recombination. The intensity evolution also showed slow decay that suggests the metastable emission behavior. A simple potential barrier model was proposed to occur between the Mg related deep levels and common Mg acceptor level, which impedes electron relaxation and thus slows down the luminescence decay. From the variation of decay time constant with temperature. a barrier energy was deduced to be about 69 meV which is very close to the electrical result of 68 meV.
Metastable photoluminescence in heavily Mg-doped GaN grown by metalorganic chemical vapor phase epitaxy
(2000)
Shu, CK
;
Lee, WH
;
Pan, YC
;
Huang, HY
;
Chen, HH
The long-term transient spectra of heavily Mg-doped GaN have been investigated. As the excitation power density increased, the broad Mg-induced emission band showed blue-shift revealing characteristic of donor-acceptor pair (DAP) recombination. We also observed an unusually slow intensity decay. The characteristic time constants range from several tenths to a few hundred seconds for emission between 360 and 460 nm. Our results are interpreted in terms of metastability due to compounded effects of differential DAP population and recombination rates and uneven acceptor distribution.
Microphotoluminescence spectra of hillocks in Al0.11Ga0.89N films
(2004-10-11)
Ke, WC
;
Ku, CS
;
Huang, HY
;
Chen, WC
;
Lee, L
The spatial variation of the optical properties of hillocks in Al0.11Ga0.89N films has been studied by using microphotoluminescence (mu-PL) microscopy. The mu-PL spectrum revealed a strong emission (I-H) at 351 nm from the hillock, besides the near-band-edge emission (I-nbe) at 341 nm. Moreover, the I-H intensity increases significantly and its full width at half maximum decreases from similar to76 to similar to53 meV by probing across the hillock center. These indicated that the hillock structure is a strong emission center. The temperature-dependent mu-PL, measurements showed that the I-H also has the S-shape behavior with a transition temperature of similar to120 K which is lower than that of I-nbe. The redshift of I-H is also smaller than I-nbe. Both indicated that the Al composition in hillocks is lower than the surrounding area. (C) 2004 American Institute of Physics.
Near-field optical microscopy and scanning Kelvin microscopy studies of V-defects on AlGaN/GaN films
(2004-10-04)
Ku, CS
;
Peng, JM
;
Ke, WC
;
Huang, HY
;
Tang, NE
AlxGa1-xN thin film was grown on undoped GaN/sapphire (0001) substrate by metalorganic chemical vapor deposition. V-defects were directly observed by atomic force microscopy (AFM) with various size of 0.5-2 mum in diameter. In a previous study, the microphotoluminescence spectra showed an extra peak (I-v=350 nm) inside the V-defect besides the near-band-edge emission (I-nbe=335 nm). To achieve better spatial resolution, we used near-field scanning optical microscopy (NSOM) and scanning Kelvin-force microscopy (SKM) to probe the V-defect in detail. The NSOM spectra showed that the intensity of the I-v band increased gradually from V-defect edges to its center, while I-nbe remained unchanged. Besides, the SKM measurements revealed that the Fermi level decreased from the flat region to V-defect center by about 0.2 eV. These results suggest that the I-v band could be related to shallow acceptor levels, likely resulting from V-Ga defects. (C) 2004 American Institute of Physics.