Browsing by Issue Date, starting with "1996-07-11"

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Polymer blends of PBT and PP compatibilized by ethylene-co-glycidyl methacrylate copolymers
(1996-07-11)
Tsai, CH
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The ethylene-co-glycidyl methacrylate (EC) copolymer is an efficient reactive compatibilizer for polymer blends of poly(butylene terephthalate) (PET) and polypropylene (PP). During melt processing, the epoxy functional group of the EG copolymer can react with the PET carboxylic acid and/or hydroxyl terminal groups at the interface to form various EG-g-PBT copolymers. These in situ formed grafted copolymers tend to concentrate along the interface to reduce the interfacial tension at the melt and result in finer phase domains. Higher glycidyl methacrylate (GMA) content in the EG copolymer or a higher quantity of the EG compatibilizer in the blend results in a better compatibilized blend in terms of finer phase domains, higher viscosity, and better mechanical properties. The presence of only 50 ppm catalyst (ethyltriphenyl phosphonium bromide)in the EG compatibilized blend further improves the blend compatibility substantially. (C) 1996 John Wiley & Sons, Inc.
Polymer blends of PBT and PP compatibilized by ethylene-co-glycidyl methacrylate copolymers
(1996-07-11)
Tsai, CH
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The ethylene-co-glycidyl methacrylate (EC) copolymer is an efficient reactive compatibilizer for polymer blends of poly(butylene terephthalate) (PET) and polypropylene (PP). During melt processing, the epoxy functional group of the EG copolymer can react with the PET carboxylic acid and/or hydroxyl terminal groups at the interface to form various EG-g-PBT copolymers. These in situ formed grafted copolymers tend to concentrate along the interface to reduce the interfacial tension at the melt and result in finer phase domains. Higher glycidyl methacrylate (GMA) content in the EG copolymer or a higher quantity of the EG compatibilizer in the blend results in a better compatibilized blend in terms of finer phase domains, higher viscosity, and better mechanical properties. The presence of only 50 ppm catalyst (ethyltriphenyl phosphonium bromide)in the EG compatibilized blend further improves the blend compatibility substantially. (C) 1996 John Wiley & Sons, Inc.
Effects of intracavity dispersion on the starting dynamics of continuous-wave passively mode-locked Ti:sapphire/DDI lasers
(1996-07-15)
Shieh, JM
;
Twu, HM
;
Pan, CL
;
交大名義發表
;
光電工程學系
Through analysis of transient autocorrelation traces, we show that intracavity dispersion significantly affects the number of initially oscillating modes as well as the buildup of passive mode locking in picosecond and femtosecond lasers. (C) 1996 Optical Society of America
Central fringe identification using a heterodyne interferometric technique and a tunable laser-diode
(1996-07-15)
Lee, JY
;
Chiu, MH
;
Su, DC
;
光電工程研究所
;
Institute of EO Enginerring
A novel method combining a heterodyne technique and a tunable laser diode for identifying the central fringe of an interferogram is presented. It has some merits, such as simple optical structure, easier operation, etc. Its feasibility is demonstrated.
Effect of magnesium on mechanical properties of Al2O3/Al-Zn-Mg-Cu metal matrix composites formed by squeeze casting
(1996-07-15)
Hsieh, JH
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Al2O3Al-Zn-Mg-Cu composites containing 2.0-3.0wt% Mg in the matrix alloy have been fabricated by squeeze casting. Light microscopy, scanning electron microscopy and image analysis were used to examine and analyze the details of the microstructure and the fracture surface. Tensile tests were used to evaluate the mechanical properties. The aging behavior of the composites was studied using differential scanning calorimetry (DSC) techniques and microhardness tests. The microhardness and ultimate tensile strength (UTS) of the composites increase with increasing Mg content, The maximum microhardness and UTS of the composites occur after aging for 24 h at 120 degrees C.
Effect of magnesium on mechanical properties of Al2O3/Al-Zn-Mg-Cu metal matrix composites formed by squeeze casting
(1996-07-15)
Hsieh, JH
;
Chao, CG
;
交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
Al2O3Al-Zn-Mg-Cu composites containing 2.0-3.0wt% Mg in the matrix alloy have been fabricated by squeeze casting. Light microscopy, scanning electron microscopy and image analysis were used to examine and analyze the details of the microstructure and the fracture surface. Tensile tests were used to evaluate the mechanical properties. The aging behavior of the composites was studied using differential scanning calorimetry (DSC) techniques and microhardness tests. The microhardness and ultimate tensile strength (UTS) of the composites increase with increasing Mg content, The maximum microhardness and UTS of the composites occur after aging for 24 h at 120 degrees C.
Dynamics of a ''Rouse'' segment as probed by depolarized photon-correlation and viscoelasticity measurements
(1996-07-15)
Lin, YH
;
Lai, CS
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
A polystyrene melt, whose molecular weight (weight-average molecular weight = 1050) is about that estimated for a Rouse segment;, has been studied with depolarized photon-correlation and viscosity measurements. Theoretically the dynamic depolarized light scattering is shown to be affected by the reorientational motion of the whole polymer molecule in the long-time region and the local segmental motions in the short-time region. The elastic dumbbell model is used to describe the viscoelasticity and reorientational motion of the polymer molecule. Relaxation times [tau] and tau(v) are extracted from the depolarized light scattering and viscosity measurement results, respectively. The ratio tau(v)/[tau], being independent of temperature as expected, is of the order of magnitude predicted from the theoretical analysis. We come to a similar conclusion supporting the above results by analyzing the depolarized photon-correlation results and the viscoelastic relaxation data in the glass-rubber transition zone of entangled polystyrene melts, which are available in literature.
Parameter extraction of resistive thermal sensors
(1996-07-15)
Chen, YM
;
Shie, JS
;
Hwang, T
;
交大名義發表
;
光電工程學系
Obtaining thermal parameters is important in evaluating the performance of thermal microsensors. Two experimental methods are described here for the study of the pressure-dependent thermal behavior of the sensors: a bolometric method that utilizes a chopped light input to obtain a sensor frequency response, and deriving its thermal data therefrom; a d.c, electrical method that measures the heat required for balance under d.c. bias, and obtaining sensor information. The thermal conductance and capacitance, absorptance, as well as emissivity of a sensor can be extracted from the experimental measurements. These parameters provide the essential data for the electrothermal SPICE program in the related design simulations.
Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures
(1996-07-15)
Chin, A
;
Chen, WJ
;
Ganikhanov, F
;
Lin, GR
;
Shieh, JM
Cross-sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70 degrees C, A columnar polycrystalline GaAs is observed for samples grown at 160 degrees C while it appears amorphous for samples grown at temperatures below 120 degrees C, The successful growth of amorphous (Ga,As) at 70 degrees C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As-4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as-grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (similar to 500 Angstrom in size) whose grain boundaries provide effective carrier traps and recombination centers. (C) 1996 American Institute of Physics.
Preparation of large area and investigation of initial film growth of YBa2Cu3O7 by scanning pulsed laser deposition
(1996-07-15)
Wu, KH
;
Wang, RC
;
Chen, SP
;
Lin, HC
;
Juang, JY
A pulsed laser deposition system with a rotating reflector, which can generate an extended plume with a diameter of about 40 mm, has been proven to be viable in producing large area YBa2Cu3O7 (YBCO) thin films. Films with uniformity of thickness and electrical properties to within a few percents were obtained. By making a further modification on this laser scanning system, YBCO films with various thicknesses can be deposited in situ on several pieces of substrates under essentially identical deposition conditions, and particularly, in a continuous fashion. The atomic force microscopy (AFM) images reveal that films grown on NdGaO3 follow the Stranski-Krastanov (layer then island growth) mode, while films grown on as-polished MgO and on annealed MgO follow the Volmer-Weber (islands without layer growth) mode and step-flow mode, respectively. (C) 1996 American Institute of Physics.
Central fringe identification using a heterodyne interferometric technique and a tunable laser-diode
(1996-07-15)
Lee, JY
;
Chiu, MH
;
Su, DC
;
交大名義發表
;
光電工程學系
A novel method combining a heterodyne technique and a tunable laser diode for identifying the central fringe of an interferogram is presented. It has some merits, such as simple optical structure, easier operation, etc. Its feasibility is demonstrated.
Preparation of large area and investigation of initial film growth of YBa2Cu3O7 by scanning pulsed laser deposition
(1996-07-15)
Wu, KH
;
Wang, RC
;
Chen, SP
;
Lin, HC
;
Juang, JY
A pulsed laser deposition system with a rotating reflector, which can generate an extended plume with a diameter of about 40 mm, has been proven to be viable in producing large area YBa2Cu3O7 (YBCO) thin films. Films with uniformity of thickness and electrical properties to within a few percents were obtained. By making a further modification on this laser scanning system, YBCO films with various thicknesses can be deposited in situ on several pieces of substrates under essentially identical deposition conditions, and particularly, in a continuous fashion. The atomic force microscopy (AFM) images reveal that films grown on NdGaO3 follow the Stranski-Krastanov (layer then island growth) mode, while films grown on as-polished MgO and on annealed MgO follow the Volmer-Weber (islands without layer growth) mode and step-flow mode, respectively. (C) 1996 American Institute of Physics.
Microstructure and subpicosecond photoresponse in GaAs grown by molecular beam epitaxy at very low temperatures
(1996-07-15)
Chin, A
;
Chen, WJ
;
Ganikhanov, F
;
Lin, GR
;
Shieh, JM
Cross-sectional transmission electron microscopy (TEM) and femtosecond (fs) reflectivity are used to study (Ga,As) compound grown at low temperatures from 160 to 70 degrees C, A columnar polycrystalline GaAs is observed for samples grown at 160 degrees C while it appears amorphous for samples grown at temperatures below 120 degrees C, The successful growth of amorphous (Ga,As) at 70 degrees C, instead of a mixture of metallic Ga droplets and As solids, suggests that the decomposition of As-4 molecules may be catalyzed by the surface Ga. Upon annealing, all samples become polycrystalline before epitaxial solid state regrowth eventually dominates and the whole sample becomes single crystal for long enough annealing. Carrier lifetime of 230 fs is measured for the as-grown amorphous sample. For the annealed sample, the photoresponse exhibits a fast initial decay of 120 fs and a much slower secondary decay of 33 ps. The initial decay is attributed to the formation of fine polycrystalline grains (similar to 500 Angstrom in size) whose grain boundaries provide effective carrier traps and recombination centers. (C) 1996 American Institute of Physics.
Heavy quark effective theory on the light front
(1996-07-20)
Zhang, WM
;
Cheung, CY
;
Lin, GL
;
物理研究所
;
Institute of Physics
The light front heavy quark effective theory is derived to all orders in 1/m(Q). In the limit m(Q)-->infinity, the theory exhibits the familiar heavy quark spin-flavor symmetry. This new formalism permits a straightforward canonical quantization to all orders in 1/m(Q); moreover, higher order terms have rather simple operator structures. The light front heavy quark effective theory can serve as a useful framework for the study of nonperturbative QCD dynamics of heavy hadron bound states.
Heavy quark effective theory on the light front
(1996-07-20)
Zhang, WM
;
Cheung, CY
;
Lin, GL
;
物理研究所
;
Institute of Physics
The light front heavy quark effective theory is derived to all orders in 1/m(Q). In the limit m(Q)-->infinity, the theory exhibits the familiar heavy quark spin-flavor symmetry. This new formalism permits a straightforward canonical quantization to all orders in 1/m(Q); moreover, higher order terms have rather simple operator structures. The light front heavy quark effective theory can serve as a useful framework for the study of nonperturbative QCD dynamics of heavy hadron bound states.
Defects and degradation in ZnO varistor
(1996-07-22)
Lee, WI
;
Young, RL
;
交大名義發表
;
友訊交大聯合研發中心
;
National Chiao Tung University
A systematic study of the defects in ZnO has been performed. The two commonly observed levels (L1, L2), located at around 0.15 and 0.24 eV under the conduction band, have been identified as native defects. The deep level transient spectroscopy depth profiling technique is applied on multilayer-chip-type ZnO varistors to determine the distribution profiles of these two levels. With higher densities near the grain boundary, L2 is unlikely to be zinc interstitials as some previous studies have assigned, Both L1 and L2 show no apparent correlation with the device degradation process. Instead, a complex defect or interface trap, related to impurities in the starting material, exhibits a much stronger correlation with the ZnO varistor's stability. (C) 1996 American Institute of Physics.
Observation of compositional modulation in (111)A InGaAs quantum wells and the effect on optical properties
(1996-07-22)
Chin, A
;
Chen, WJ
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have studied the growth of InGaAs/GaAs multiple quantum wells (MQWs) on (111)A GaAs. Uniform thickness of (111)A quantum wells is observed by the cross-sectional transmission electron microscopy (TEM). Growth induced long-range In- and Ga-rich InxGa1-xAs/InyGa1-yAs superlattice in (111)A is also observed by cross-sectional TEM in the ternary InGaAs wells. In contrast, none of the above superstructure was observed by TEM on a side-by-side grown (100) oriented substrate. However, the photoluminescence (PL) linewidth is broadened by such compositional modulation. Low-temperature (15 K) photoluminescence showed a broad PL linewidth of 27.5 meV for In0.16Ga0.84As/GaAs MQWs grown on (111)A substrates at 520 degrees C. A decreased PL linewidth of 15.7 meV and a reduced compositional modulation in InGaAs wells can be achieved at a higher growth temperature of 560 degrees C. (C) 1996 American Institute of Physics.
Analysis of random dynamical systems by interpolated cell mapping
(1996-07-25)
Ge, ZM
;
Lee, SC
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
A method of interpolated cell mapping (ICM) is developed for global analysis of random dynamical systems. In this method, one first analyzes a random system by constructing a uniform number of sample interpolated trajectories for each cell. More sample interpolated trajectories are then constructed for critical cells sensitive to random effects to characterize the global behaviour of the system. When applied to the global analysis of non-linear systems with uncertain external loadings or system parameters, the proposed method yields more precise results than the generalized cell mapping (GCM) method. These results agree well with those obtained by Monte Carlo simulation. Additionally, the proposed method allows global analyses of random systems to be improved easily when the original regions of study are too large to give precise analyses. (C) 1996 Academic Press Limited
Analysis of random dynamical systems by interpolated cell mapping
(1996-07-25)
Ge, ZM
;
Lee, SC
;
機械工程學系
;
Department of Mechanical Engineering
A method of interpolated cell mapping (ICM) is developed for global analysis of random dynamical systems. In this method, one first analyzes a random system by constructing a uniform number of sample interpolated trajectories for each cell. More sample interpolated trajectories are then constructed for critical cells sensitive to random effects to characterize the global behaviour of the system. When applied to the global analysis of non-linear systems with uncertain external loadings or system parameters, the proposed method yields more precise results than the generalized cell mapping (GCM) method. These results agree well with those obtained by Monte Carlo simulation. Additionally, the proposed method allows global analyses of random systems to be improved easily when the original regions of study are too large to give precise analyses. (C) 1996 Academic Press Limited
Picosecond photoresponse of carriers in Si ion-implanted Si
(1996-07-29)
Chin, A
;
Lee, KY
;
Lin, BC
;
Horng, S
;
電子工程學系及電子研究所
Picosecond photoresponse of carriers in Si ion-implanted Si samples has been measured using femtosecond transient reflectivity measurement. A threshold peak implant dose of 10(16) cm(-2) is required to achieve picosecond carrier lifetime. At this dosage, carrier lifetimes of 0.9 and 1.4 ps are measured for the as-implanted and 400 degrees C annealed Si substrates, respectively. The increase in carrier lifetime upon annealing is attributed to the reduction in the concentration of trap and recombination centers. Sheet resistance also shows a strong dependence on the annealing temperature. An eightfold increase in sheet resistance is obtained for annealed samples, and a reduction in hopping conduction, manifested by the e(-1/T) temperature dependence, may be responsible for the increase in resistance. Further evidence of decreasing hopping conduction can be also observed from the more than two orders of magnitude in reduction of sheet resistance as the peak dosage decreases from 10(16) to 10(14) cm(-2). (C) 1996 American Institute of Physics.