Browsing by Author "Ho, JC"

Now showing 1 - 18 of 18

beta-Lactoglobulin is a thermal marker in processed milk as studied by electrophoresis and circular dichroic spectra
(2005-05-01)
Chen, WL
;
Hwang, MT
;
Liau, CY
;
Ho, JC
;
Hong, KC
As much of the sterilization process involves heat treatment during the preparation of milk on an industrial scale, the unpredictable measures of the process are an essential issue in determining the quality of the milk. The purpose of the present study was to investigate the major protein change(s) of whey proteins in processed milk and extend the knowledge for future reference in the dairy industry. Using a native polyacrylamide gel electrophoresis, we showed almost a 90% loss and denaturation of beta-lactoglobulin (LG), but not alpha-lactalbumin ( LA), in some brands of the processed and dry milks. Immunochemical analysis using Western blotting revealed that part of the loss was attributed to the formation of large multiple forms of LG in the processed product. Such denaturation was presumably associated with the heating procedure used in the process. Essentially, LG was the only major fraction converted to aggregates in milk heated at 95 degrees C for 30 min on 2-dimensional PAGE. The detailed thermal denaturation of purified LG and LA at various temperatures ( 50 to 95 degrees C) and time ( 5 to 960 s) were investigated using a circular dichroic analysis. The maximal changes of ellipticity at 205 nm ( converting beta-structure to disordered structure) were correlated to heating temperature and time. There were no significant conformational changes of LG at temperatures below 70 degrees C for as long as 480 s. Pronounced and rapid changes occurred between 80 to 95 degrees C in a time-dependent manner. Fifty percent of the maximal changes could be reached within 15 s. In conclusion, the unique chemical and immunochemical loss and conformational changes made LG a superior marker for evaluating the thermal processing of milk. The detailed thermal denaturation curves of LG constructed with its time and temperature in this study provide a valuable reference for the dairy industry. We postulate that heat treatment over 80 degrees C in 15 s may induce a significant denaturation of milk LG.
Characterization and conductive coating of phosphors for improved brightness
(2005-04-30)
Chang, CH
;
Chiou, BS
;
Chen, KS
;
Ho, JC
;
電子工程學系及電子研究所
In this study, the phosphors used in CRTs are coated with In2O3 conductive layer derived from the hydrolysis of indium chloride. The conductive coating retards/eliminates charging-up on the phosphor surface during the bombardment of the electrons and improves the cathodoluminescent brightness of the phosphor. However, the non-emissive conductive coating also degrades the cathodoluminescent brightness when it is too thick. The cathodoluminescent brightness increases initially with the amount of coating, reaches a maximum at 10 wt.% InCl3, and decreases with further increase of coating. It is found that with a 10 wt.% InCl3 coating, the brightness of phosphor increases by 20% at 500 V and 1 mu A. (c) 2004 Published by Elsevier B.V.
Chemical solution deposition of Zn1-xZrxO thin films as active channel layers of thin-film transistors
(2006)
Lee, JH
;
Lin, P
;
Ho, JC
;
Lee, CC
;
材料科學與工程學系
Sol-gel derived Zn1- xZrxO films and thin-film transistors (TFTs) were investigated in this study, where x ranges from 0.00 to 0.10. The effects of the Zr additive on the crystallinity, grain size, and surface morphology of Zn1- xZrxO films are discussed. Zn1- xZrxO-TFTs exhibited much lower off-state current (I-OFF) and higher on/off ratio than pure ZnO-TFT. The behavior of I-OFF related to the carrier concentration (n) of Zn1-xZrxO films and the correlation between n and the grain size are interpreted. The optimized I-OFF and on/off ratio of Zn1- xZrxO-TFT were 3.24 x 10(-13) A/mu m and 8.89 x 10(6) where x = 0.03, respectively. (c) 2006 The Electrochemical Society.
Ester-amide exchange in blends of liquid-crystalline copolyester and polyamide 6
(2000-08-15)
Ho, JC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The kinetics of the ester-amide exchange in solution blends of the random liquid-crystalline polyester copoly(oxybenzoate-terephthalate) (P64) and polyamide 6 (PA6) were studied with carbon nuclear magnetic resonance. With second-order reversible reactions assumed, the activation energy of the ester-amide interchange in 30/70, 50/50, and 70/30 P64/PA6 blends were all about 24.0 kcal/mol. The pre-exponential factors for the ester-amide exchange in 30/70, 50/50, and 70/30 P64/PA6 blends were 2.01 x 10(11), 2.59 x 10(10), and 2.74 x 10(12) min(-1), respectively. (C) 2000 John Wiley & Sons, Inc.
Induced gamma -> alpha crystal transformation in blends of polyamide 6 and liquid crystalline copolyester
(2000-07-11)
Ho, JC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The equilibrium melting temperatures and the induced gamma --> ct crystal transformation in blends of random liquid crystalline copoly(oxybenzoate-ethylene terephthalate) at molar ratio 60/40 (P64) and polyamide 6 (PA6) under different thermal treatments were investigated with differential scanning calorimetry and wide-angle X-ray diffraction, respectively. It was found that the equilibrium melting temperatures of P64/PA6 blends depended strongly on the amount of P64, and the presence of a small amount of P64 in PA6, around 5%, induced additional crystallization of the or-form crystal in the quenched PA6. Moreover, the onset temperature for the gamma --> alpha crystal transformation in the 5/95 P64/PA6 blend was reduced by 30 degrees C as compared to that in the pure PA6 case (160 degrees C vs 130 degrees C).
Influence of measuring environment on the electrical characteristics of pentacene-based thin film transistors
(2004-11-22)
Wang, YW
;
Cheng, HL
;
Wang, YK
;
Hu, TH
;
Ho, JC
This work concerns the electrical properties and carrier transport behavior of polycrystalline pentacene-based thin film transistors (TFTs) in air and high-vacuum environments. The transistor in a high vacuum outperforms that in air. The dependence of the field-effect mobility on the gate voltage and the drain voltage is considered. A potential barrier model is applied to estimate the trap density of the pentacene transistor. The determined trap density at the grain boundaries of the pentacene film in air exceeds that in a high vacuum. These results show that the increased trap concentration at the grain boundaries in ambient air limits carrier transport. (C) 2004 Elsevier B.V. All rights reserved.
Miscibility in blends of liquid crystalline copolyester and semicrystalline poly(ethylene-2,6-naphthalene dicarboxylate)
(2000-12-01)
Ho, JC
;
Lin, TC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The miscibility in blends of random liquid crystalline copoly(oxybenzoate-ethylene terephthalate) at a molar ratio of 60:40 (P64) and semicrystalline poly(ethylene-2,6-naphthalene dicarboxylate) (PEN) were investigated with differential scanning calorimetry, wide angle X-ray diffraction and polarized optical micrography. It was found that P64 and PEN were partially miscible as evidenced from the appearance of a single glass transition temperature for each blend at different compositions. Furthermore, the Flory-Huggins interaction parameter, chi(12), for P64 and PEN was determined to be -1.13 through the melting point depression analysis, indicating miscibility in blends of P64; and PEN at the melt state. The coherence lengths of PEN in the presence of a small amount of P64, around 3%, were larger than that in pure PEN, implying the regularity of PEN crystals in the blends with low P64 content being more perfect than that of the pure PEN. (C) 2000 Elsevier Science Ltd. All rights reserved.
Miscibility in blends of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) and polycarbonate
(1997-07-01)
Wei, KH
;
Jang, HC
;
Ho, JC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The miscibility of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) (HIQ) and polycarbonate (PC) was investigated with differential scanning calorimetry (d.s.c.). It was found that blends of liquid crystalline HIQ and PC showed a single glass transition temperature across the whole composition range. Annealing these blends at temperatures slightly above the melting point of HIQ, ester exchange occurred as confirmed both by i.r. and n.m.r. spectroscopy. The apparent miscibility of HIQ and PC was caused by this reaction. The blends retained liquid crystalline characteristics in the first few reaction minutes. As the transesterification continued, the bisphenol-A segment in PC reacted with both isophthalate and oxybenzoate segments in HIQ. This resulted in amorphous polymers. These amorphous polymers exhibited a single glass transition temperature higher than that for both pure polymers. (C) 1997 Elsevier Science Ltd.
Miscibility in blends of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) and polycarbonate
(1997-07-01)
Wei, KH
;
Jang, HC
;
Ho, JC
;
交大名義發表
;
材料科學與工程學系
The miscibility of liquid crystalline poly(p-oxybenzoate-co-p-phenyleneisophthalate) (HIQ) and polycarbonate (PC) was investigated with differential scanning calorimetry (d.s.c.). It was found that blends of liquid crystalline HIQ and PC showed a single glass transition temperature across the whole composition range. Annealing these blends at temperatures slightly above the melting point of HIQ, ester exchange occurred as confirmed both by i.r. and n.m.r. spectroscopy. The apparent miscibility of HIQ and PC was caused by this reaction. The blends retained liquid crystalline characteristics in the first few reaction minutes. As the transesterification continued, the bisphenol-A segment in PC reacted with both isophthalate and oxybenzoate segments in HIQ. This resulted in amorphous polymers. These amorphous polymers exhibited a single glass transition temperature higher than that for both pure polymers. (C) 1997 Elsevier Science Ltd.
Pentacene-based thin film transistors used to drive a twist-nematic liquid crystal display
(2005-11-22)
Wang, YW
;
Cheng, HL
;
Wang, YK
;
Hu, TH
;
Ho, JC
The study addresses the factors of influence on the active matrix display that is driven by pentacene-based organic thin-film transistors (TFTs). The atmosphere and humidity conditions were found to seriously affect the performance of organic TFTs. An appropriate encapsulation layer was added to protect the organic TFTs from external damage. Organic TFTs reliability, the illumination effect and device uniformity, were also considered in the context of display application. Finally, a monochrome 3 inch 64 x 128 active-matrix twist-nematic liquid crystal display (LCD) was fabricated. The display is capable of showing video images with a refresh rate of 20 Hz. Obtained results reveal the potential of organic TFTs for active-matrix LCD technology. (c) 2005 Elsevier B.V All rights reserved.
Resin transfer molding (RTM) process of a high performance epoxy resin. I: Kinetic studies of cure reaction
(2000-04-01)
Lee, CL
;
Ho, JC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The cure kinetics of a high performance PR500 epoxy resin in the temperature range of 160-197 degrees C for the resin transfer molding (RTM) process have been investigated. The thermal analysis of the curing kinetics of PR500 resin was carried out by differential scanning calorimetry (DSC), with the ultimate heat of reaction measured in the dynamic mode and the rate of cure reaction and the degree of cure being determined under isothermal conditions. A modified Kamal's kinetic model was adapted to describe the autocatalytic and diffusion-controlled curing behavior of the resin. A reasonable agreement between the experimental data and the kinetic model has been obtained over the whole processing temperature range, including the mold filling and the final curing stages of the RTM process.
Sol-gel-derived Zn((1-x))Mg(x)O thin films used as active channel layer of thin-film transistors
(2005-07-01)
Lee, JH
;
Lin, P
;
Lee, CC
;
Ho, JC
;
Wang, YW
Sol-gel derived n-type Zn((1-x))Mg(x)O (x = 0-0.45) thin films and thin-film transistors (TFTs) with active channel layers made of the films were investigated. The films were prepared at 500 degrees C. The effects of Mg doping on the crystallinity, optical transparency, grain size, and charge-carrier concentration (n) of the films were examined. The Fermi level of the films, as derived from the temperature dependence of n, was similar to 0.12eV below the conduction band. The donor concentration and donor level (E(d)) were derived by a curve fitting method based on the electrical neutrality condition. Ed was found to be similar to 0.3 eV below the conduction band. The composition dependence of the TFT output characteristics was interpreted and correlated to the width of the depletion region adjacent to the grain boundaries. When the grains were almost depleted at x = 0.2, the TFT showed an enhancement mode and an on/off ratio of 10(6).
Sol-gel-derived Zn(1-x)MgxO thin films used as active channel layer of thin-film transistors
(2005-07-01)
Lee, JH
;
Lin, P
;
Lee, CC
;
Ho, JC
;
Wang, YW
Sol-gel derived n-type Zn(1-x)MgxO (x = 0-0.45) thin films and thin-film transistors (TFTs) with active channel layers made of the films were investigated. The films were prepared at 500 degrees C. The effects of Mg doping on the crystallinity, optical transparency, grain size, and charge-carrier concentration (n) of the films were examined. The Fermi level of the films, as derived from the temperature dependence of n, was similar to 0.12eV below the conduction band. The donor concentration and donor level (E-d) were derived by a curve fitting method based on the electrical neutrality condition. Ed was found to be similar to 0.3 eV below the conduction band. The composition dependence of the TFT output characteristics was interpreted and correlated to the width of the depletion region adjacent to the grain boundaries. When the grains were almost depleted at x = 0.2, the TFT showed an enhancement mode and an on/off ratio of 10(6).
Study on blends of liquid crystalline copolyesters with polycarbonate .3. Mechanical properties of compatibilized blends
(1997-03-21)
Wei, KH
;
Ho, JC
;
交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
Blends of liquid crystalline poly(oxybenzoate-co-oxynaphthalate) (Vectra A950) and polycarbonate (PC) were prepared by adding a compatibilizer to the two polymers in a melt-blending process. The compatibilizer was based on controlled transesterification between synthesized poly(oxybenzoate-co-terephthalate) (40/60) and PC. The compatibilizer exhibited birefringence, and its thermal property was analyzed by differential scanning calorimetry. The maximum increase in tensile modulus and tensile strength of these compatibilized Vectra blends were 24% and 54%, respectively, as compared with those of binary Vectra blend without compatibilizer resulting from an injection-molding process. The tensile properties of the compatibilized Vectra blends decreased once the concentration of the compatibilizer exceeded 2 phr. (C) 1997 John Wiley & Sons, Inc.
Synthesis and characterization of liquid crystalline multiblock copolyesters of oxybenzoate and ethylene terephthalate
(1999-06-01)
Ho, JC
;
Lin, YS
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Multiblock copoly(oxybenzoate-p-ethylene terephthalate) (POB-PET) was synthesized by a direct reaction of poly(hydroxybenzoic acid) (PHBA), acetoxybenzoic acid and poly(ethylene terephthalate). The synthesized multiblock POB-PET becomes more blocky and less soluble in the mixed solvent of trifluoroacetic acid and chloroform when the degree of polymerization of PHBA used in the synthesis is higher as evidenced in the solid-state and liquid-state nuclear magnetic resonance study. The thermal curves displayed by the synthesized multiblock 20/80 and 40/60 POB-PET contained distinctive contributions from both PET blocks and POB blocks in the copolymers when the degree of polymerization of PHBA used in the synthesis is seven. Only 20 mol% of POB is needed to form liquid crystalline phase in these multiblock POB-PET as opposed to a minimum of 40 mol% of POB is required to form liquid crystalline phases for random POB-PET. (C) 1999 Elsevier Science Ltd. All rights reserved.
The effect of In2O3 conductive coating on the luminescence and zeta potential of ZnS : Cu, Al phosphors
(2005)
Chang, CH
;
Chiou, BS
;
Chen, KS
;
Ho, CC
;
Ho, JC
Phosphors used in CRTs have been coated with In2O3 conductive layer derived from the hydrolysis of indium chloride. It was found that brightness of the phosphors rises initially with the amount of InCl3, reaches a maximum at 10 Wt-% InCl3 and then decreases when more InCl3 was added. With 10 wt.% InCl3 coating, the brightness of ZnS:Cu, Al phosphor increases by 24% at 800 V and I RA while very little changes were observed in the luminescent emission peak and CIE color loci. The luminescence decay times increase with the increase of the conductive coating. However, they are shorter than 0.7 mu s for samples with the amount of coating ranging from 0 to 20 wt.% InCl3 and are Suitable for display applications. Conductive coating affects the surface chemistry of the phosphor particles, enhances the zeta potential of ZnS:Cu, Al in IPA solution. and, consequently, increases the electrophoretic deposition rate of the phosphors onto substrate. The zeta potential of 10 wt.% InCl3 coated ZnS:Cu, Al in isopropyl alcohol solution is 32 mV as compared to 1.2 mV of that of the uncoated ZnS:Cu, Al. Besides, the electrophoretic deposition rate of the 10 wt.% InCl3 coated ZnS:Cu, Al (0.23 mg/s) is larger than that of the uncoated phosphor (0.17 mg/s). (c) 2005 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
The kinetics of transesterification in blends of liquid crystalline copolyester and polycarbonate
(1999-02-01)
Ho, JC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The kinetics of transesterification in blends of thermotropic copoly(oxybenzoate-ethylene terephthalate) and polycarbonate at melt state were analysed quantitatively with C-13 nuclear magnetic resonance, and were then modelled by a phenomenological equation. It was found that the activation energy for the transesterification reaction between the poly(oxybenzoate) segment in copoly(oxybenzoate-ethylene terephthalate) and polycarbonate was more than twice that for the transesterification reaction between the poly(ethylene terephthalate) segment and polycarbonate (i.e. 94.6 versus 41.8 kcal/mol). This is probably due to the stronger chemical bond in oxybenzoate-oxybenzoate that in ethylene-terephthalate. Additionally, owing to the rigid-rod nature of the poly(oxybenzoate) segment, the frequency factor in the transesterification reaction in poly(oxybenzoate) segment and polycarbonate is much higher than that in poly(ethylene terephthalate) segment and polycarbonate (i.e. 10(36) versus 10(14) min(-1)). (C) 1998 Elsevier Science Ltd. All rights reserved.
The role of transesterification on the miscibility in blends of polycarbonate and liquid crystalline copolyester
(1997-03-24)
Wei, KH
;
Ho, JC
;
交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
Transesterification mechanisms and rate in blends of polycarbonate (PC) and random liquid crystalline polyester copoly(oxybenzoate-p-terephthalate) at molar ratio 40/60 (P46) were studied through a five-component diad analysis and with C-13 and H-1-C-13 nuclear magnetic resonance spectroscopy. It was found that the ester-ester interchange in the two polymers took place within 15 min when the blend was annealed at 260 degrees C in vacuum. In the annealed blend, the Bisphenol A unit in polycarbonate reacted first with the terephthalate unit and then with the oxybenzoate unit in copoly(oxybenzoate-p-terephthalate). As the transesterification in the blend continued for about 1 h, the forming of dad Bisphenol A-oxybenzoate exceeded that of diad Bisphenol A-terephthalate. This large loss (57%) of the diad oxybenzoate-oxybenzoate caused the disappearance of the liquid crystalline phase in the blend. In sharp contrast to the originally immiscible blend of PC and P46 (two distinctive glass transition temperatures), the large loss of the liquid crystalline diad resulted in complete miscibility in the annealed blend, as evidenced by the appearance of a single glass transition temperature in the differential scanning calorimetry measurement.