Browsing by Issue Date, starting with "1997-03-21"

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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.
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.
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.
Elastic interaction between screw dislocations and a circular surface crack
(1997-03-31)
Lin, KM
;
Lin, HC
;
Chen, KC
;
Chang, HL
;
材料科學與工程學系
The behaviour of a screw dislocation around a circular surface crack was analyzed using the conformal mapping method. The effects of the crack length l and its radius of curvature R on the shielding effect and the strain energy were discussed in detail. It was found that for a dislocation being fixed at a constant distance from the crack tip and located on a plane tangent to crack surface at the tip, there exists a critical crack length l* corresponding to a maximum shielding effect induced by the dislocation on the circular surface crack. The l* increases with R and approaches infinity as the crack becomes planar (i.e. R --> infinity). The shielding effect vanishes as the crack disappears. It increases rapidly with l if 0 < l much less than l*, regardless of R. After reaching the maximum, it decreases slightly for larger R but significantly for smaller R as the crack becomes longer. The shielding is more pronounced for larger R than that for smaller R, with the difference increasing with crack length. As a result, a surface microcrack propagates initially in a rather brittle manner then becomes more ductile. When the crack gets longer, it still keeps ductile for a less curved or a planar crack but becomes relatively brittle for a severely curved crack. In addition, the strain energy is also significantly influenced by crack length and increases rapidly with l when l is rather small, regardless of R. With increasing l, it becomes less affected by l, and the variation with R is still not obvious, with larger R corresponding to a slightly higher strain energy. (C) 1997 Elsevier Science S.A.
Elastic interaction between screw dislocations and a circular surface crack
(1997-03-31)
Lin, KM
;
Lin, HC
;
Chen, KC
;
Chang, HL
;
材料科學與工程學系
The behaviour of a screw dislocation around a circular surface crack was analyzed using the conformal mapping method. The effects of the crack length l and its radius of curvature R on the shielding effect and the strain energy were discussed in detail. It was found that for a dislocation being fixed at a constant distance from the crack tip and located on a plane tangent to crack surface at the tip, there exists a critical crack length l* corresponding to a maximum shielding effect induced by the dislocation on the circular surface crack. The l* increases with R and approaches infinity as the crack becomes planar (i.e. R --> infinity). The shielding effect vanishes as the crack disappears. It increases rapidly with l if 0 < l much less than l*, regardless of R. After reaching the maximum, it decreases slightly for larger R but significantly for smaller R as the crack becomes longer. The shielding is more pronounced for larger R than that for smaller R, with the difference increasing with crack length. As a result, a surface microcrack propagates initially in a rather brittle manner then becomes more ductile. When the crack gets longer, it still keeps ductile for a less curved or a planar crack but becomes relatively brittle for a severely curved crack. In addition, the strain energy is also significantly influenced by crack length and increases rapidly with l when l is rather small, regardless of R. With increasing l, it becomes less affected by l, and the variation with R is still not obvious, with larger R corresponding to a slightly higher strain energy. (C) 1997 Elsevier Science S.A.