Browsing by Issue Date, starting with "1996-07-04"

Now showing 1 - 20 of 85263

Bifurcations and chaos in a rate gyro with harmonic excitation
(1996-07-04)
Ge, ZM
;
Chen, HH
;
機械工程學系
;
Department of Mechanical Engineering
Bifurcations and chaos in a rate gyro with harmonic excitation
(1996-07-04)
Ge, ZM
;
Chen, HH
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
Short leaky-wave antennas of sum and difference patterns
(1996-07-04)
Lin, JM
;
Tzuang, CKC
;
Chou, GJ
;
Su, S
;
交大名義發表
A set of differential feed short (similar to 0.7 lambda(0)) leaky-wave antennas with sum (Sigma) and difference (Delta) patterns is presented. Rigorous field-theory analyses show that the radiation characteristics of these antennas agree well with the measurements. The performance of these antennas is well suited for direction finding applications.
Estimation of the Gilbert model parameters using the simulated annealing method
(1996-07-04)
Tan, TH
;
Chang, WW
;
交大名義發表
;
電信工程研究所
;
National Chiao Tung University
An estimation method based on the simulated annealing algorithm is proposed for computing the Gilbert model parameters from sample error sequences. Experimental results indicate that the simulated annealing method yields estimates which more closely match the experimental error statistics.
Short leaky-wave antennas of sum and difference patterns
(1996-07-04)
Lin, JM
;
Tzuang, CKC
;
Chou, GJ
;
Su, S
;
電信工程研究所
A set of differential feed short (similar to 0.7 lambda(0)) leaky-wave antennas with sum (Sigma) and difference (Delta) patterns is presented. Rigorous field-theory analyses show that the radiation characteristics of these antennas agree well with the measurements. The performance of these antennas is well suited for direction finding applications.
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.