Browsing by Issue Date, starting with "1997-03-15"

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Very high hole mobility in p-type Si/SiGe modulation-doped heterostructures
(1997-03-15)
Tsai, WC
;
Chang, CY
;
Huang, GW
;
Fang, FF
;
Chang, YH
In this study, high-quality Si/Si1-xGex/Si p-type modulation-doped heterostructures were grown by ultrahigh-vacuum/chemical vapor deposition (UHV/CVD). High-field magnetotransport measurements revealed Shubnikov-de Hass oscillations in the longitudinal magneto resistance and the integer quantum Hall effect in transverse magnetoresistance illustrating the presence of a well-confined two-dimensional hole gas. The mobilities of the two-dimensional hole gas, as high as 12500 cm(2)/V . s at 0.65 K, were obtained for normal (doped layer at surface side) modulation-doped heterostructures with x = 0.12 at a sheet carrier concentration of 3.45 x 10(11) cm(-2). In addition, for this heterostructure, temperature-dependent measurements of Shubnikov-de Hass oscillations in the range 0.65 K-2.4 K were taken and the hole effective mass of 0.295m(0) + 0.01m(0) was obtained.
Magnetic exchange coupling in (Dy,Tb)FeCo magneto-optical recording films
(1997-03-15)
Hwang, WK
;
Shieh, HPD
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
The required bias field of a sperimagnetic film is governed by a finite exchange coupling coefficient (lambda) mainly determined by the subnetwork coupling. From the study of a series of (Dy,Tb)FeCo films at compensation composition it is found that lambda is mainly determined by the concentration of the rare earth components. Moreover, the exchange integral between rare earth and transition metal subnetworks can be derived from lambda so that the number of uncertain parameters for mean held modeling is reduced. Accordingly, the bias field required for magneto-optical recording is mainly proportional to lambda that can be obtained quantitatively from either measurement and/or mean field modeling. (C) 1997 American Institute of Physics.
Magnetic exchange coupling in (Dy,Tb)FeCo magneto-optical recording films
(1997-03-15)
Hwang, WK
;
Shieh, HPD
;
光電工程研究所
;
Institute of EO Enginerring
The required bias field of a sperimagnetic film is governed by a finite exchange coupling coefficient (lambda) mainly determined by the subnetwork coupling. From the study of a series of (Dy,Tb)FeCo films at compensation composition it is found that lambda is mainly determined by the concentration of the rare earth components. Moreover, the exchange integral between rare earth and transition metal subnetworks can be derived from lambda so that the number of uncertain parameters for mean held modeling is reduced. Accordingly, the bias field required for magneto-optical recording is mainly proportional to lambda that can be obtained quantitatively from either measurement and/or mean field modeling. (C) 1997 American Institute of Physics.
Resistive response to a microwave field in high temperature superconducting crystals
(1997-03-15)
Wu, CJ
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The microwave properties of high temperature superconducting crystals in the resistive states are theoretically investigated. The single crystals in the shapes of platelet and cylinder in parallel held configuration are considered. The microwave responses are analyzed from the associated effective r.f. magnetic permeabilities. The influence of the anisotropic resistivity on the microwave response is stressed in an anisotropic superconductor. The results indicate the importance of thin edges of the platelet crystal to the microwave properties. In the isotropic superconductor, a relationship between the responses of a square rod and a cylinder is found. The results show that the microwave properties of a cylinder can be essentially replaced by those of a square rod and vice versa. Also the geometric effect on the response is illustrated in the isotropic superconductor.
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.
A novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids
(1997-03-21)
Wu, HJ
;
Chern, JH
;
交大名義發表
;
應用化學系
;
National Chiao Tung University
Treatment of tetraoxa-cages 1a-f with Lewis acids such as TlC4, AlCl3, BF3 . OEt(2) and MeSO(3)H in dichloromethane at 25 degrees C gives the rearrangement products 2a-f in 90% yields regioselectively and stereoselectively; a novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids.
A novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids
(1997-03-21)
Wu, HJ
;
Chern, JH
;
應用化學系
;
Department of Applied Chemistry
Treatment of tetraoxa-cages 1a-f with Lewis acids such as TlC4, AlCl3, BF3 . OEt(2) and MeSO(3)H in dichloromethane at 25 degrees C gives the rearrangement products 2a-f in 90% yields regioselectively and stereoselectively; a novel hydride rearrangement of the acetal group of tetraacetal tetraoxa-cages mediated by Lewis acids.
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.
管管的法國梧桐不同
(1997-03-24)
管管
老秋
(1997-03-24)
管管
Physical characteristics of N-2 annealing on room-temperature-deposited ion plating oxide
(1997-03-24)
Yeh, CF
;
Chen, TJ
;
Kao, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of N-2 annealing on the physical properties of room-temperature-deposited ion plating (IF) oxide have been characterized. As-deposited IP oxide exhibits higher refractive index and dielectric constant values than high-temperature-annealed IP oxide. Strained bonds existing in as-deposited oxide can be relaxed by N-2 annealing depending on the annealing temperature. After annealing at 800 degrees C, the physical characteristics of IP oxide are comparable to those of thermal oxide. (C) 1997 American Institute of Physics.
管管的法國梧桐不同
(1997-03-24)
管管
Physical characteristics of N-2 annealing on room-temperature-deposited ion plating oxide
(1997-03-24)
Yeh, CF
;
Chen, TJ
;
Kao, JS
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effects of N-2 annealing on the physical properties of room-temperature-deposited ion plating (IF) oxide have been characterized. As-deposited IP oxide exhibits higher refractive index and dielectric constant values than high-temperature-annealed IP oxide. Strained bonds existing in as-deposited oxide can be relaxed by N-2 annealing depending on the annealing temperature. After annealing at 800 degrees C, the physical characteristics of IP oxide are comparable to those of thermal oxide. (C) 1997 American Institute of Physics.
管管的法國梧桐不同
(1997-03-24)
管管
管管的法國梧桐不同
(1997-03-24)
管管
管管的法國梧桐不同
(1997-03-24)
管管
Reflection-type normally-on two-wavelength modulator
(1997-03-27)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The authors demonstrate a novel reflection-type normally-on two-wavelength modulator by combining two quantum-well structures with different operating wavelengths in a coupled cavity structure. Reflection spectra show simultaneous modulations at wavelengths of 856 and 886 nm in the device consisting of GaAs/A1GaAs and InGaAs/A1GaAs quantum wells for each wavelength. Under separate applied voltages, maximum reflectivity changes of 70 and 54% were obtained for the two wavelengths. To the best of the authors' knowledge, this is the First two-wavelength reflection modulator ever reported.
Development of a feedforward active noise control system by using the H-2 and H infinity model matching principle
(1997-03-27)
Bai, MR
;
Chen, HP
;
交大名義發表
;
機械工程學系
;
National Chiao Tung University
Two novel active noise control techniques on the basis of feedforward H-2 and H-infinity optimal model matching principle are proposed. These methods effectively overcome the problem of unstable inverse plant resulting from the inherent non-minimum phase property of the cancellation path. The proposed algorithms are implemented by using a digital signal processor. The experimental results obtained by using H-2 and H-infinity feedforward techniques show attenuation for stationary noise in a duct as comparable to those of conventional methods. The proposed methods also have potential in suppressing transient noises that have been the major difficulty in adaptive methods. Comparisons of the methods are summarized. (C) 1997 Academic Press Limited.
Development of a feedforward active noise control system by using the H-2 and H infinity model matching principle
(1997-03-27)
Bai, MR
;
Chen, HP
;
機械工程學系
;
Department of Mechanical Engineering
Two novel active noise control techniques on the basis of feedforward H-2 and H-infinity optimal model matching principle are proposed. These methods effectively overcome the problem of unstable inverse plant resulting from the inherent non-minimum phase property of the cancellation path. The proposed algorithms are implemented by using a digital signal processor. The experimental results obtained by using H-2 and H-infinity feedforward techniques show attenuation for stationary noise in a duct as comparable to those of conventional methods. The proposed methods also have potential in suppressing transient noises that have been the major difficulty in adaptive methods. Comparisons of the methods are summarized. (C) 1997 Academic Press Limited.
MOS magnetic current sensor based on standard CMOS process
(1997-03-27)
Yang, HM
;
Lei, TF
;
Huang, YC
;
Lee, CL
;
電子工程學系及電子研究所
A novel current sensor is proposed. The current sensor consists of one MOS magnetic sensor and a flat coil in an industrial CMOS process, An experimental device demonstrated a sensitivity of 8.4mV/A.