Browsing by Issue Date, starting with "1996-08-25"

Now showing 1 - 20 of 85156

Effect of lateral substituent on the mesomorphic properties of ferroelectric side-chain liquid crystalline polysiloxanes.
(1996-08-25)
Hsu, CS
;
Tsai, CT
;
應用化學系
;
Department of Applied Chemistry
Effect of lateral substituent on the mesomorphic properties of ferroelectric side-chain liquid crystalline polysiloxanes.
(1996-08-25)
Hsu, CS
;
Tsai, CT
;
應用化學系
;
Department of Applied Chemistry
Thermally stimulated deporization current and DSC studies of the dual glass transitions in side-chain liquid crystalline copolysiloxanes
(1996-08-25)
Chang, HL
;
Hsu, CS
;
應用化學系
;
Department of Applied Chemistry
A new imidazoles as potent inhibitors of beta-glucosidase.
(1996-08-25)
Shu, HH
;
Li, YK
;
應用化學系
;
Department of Applied Chemistry
Thermally stimulated deporization current and DSC studies of the dual glass transitions in side-chain liquid crystalline copolysiloxanes
(1996-08-25)
Chang, HL
;
Hsu, CS
;
應用化學系
;
Department of Applied Chemistry
Influences of deposition temperature on thermal stability and moisture resistance of chemical vapor deposited fluorinated silicon oxide by using indirect fluorinating precursor
(1996-08-26)
Chang, KM
;
Wang, SW
;
Wu, CJ
;
Yeh, TH
;
Li, CH
In this letter, fluorinated silicon oxide (FxSiOy) films were deposited in the electron cyclotron resonance (ECR) chemical vapor deposition system with SiH4, O-2, and CF4 as the reaction gases. The CF4, in contrast to SiF4 or FSi(OC2H5)(3) used in other reports, is an indirect fluorinating source. The fluorinating mechanism is similar to that of the etching of oxide by fluorocarbon plasma, therefore, the thermal stability of the incorporated fluorine must strongly depend on the deposition temperature. It is found that the thermal stability and moisture resistance are greatly improved by increasing the deposition temperature. However, the higher deposition temperature also results in a higher compressed stress and dielectric constant. Besides, to get the moisture resistance, the deposition temperature must be above 300 degrees C. On the other hand, ECR-SiO2 (without fluorination), even deposited at room temperature, is shown to have a good water resistance. Therefore, by choosing deposition temperature for FxSiOy to have enough thermal tolerance and capping with ECR-SiO2, the moisture resistor is suggested for the inter metal dielectric applications.
Influences of deposition temperature on thermal stability and moisture resistance of chemical vapor deposited fluorinated silicon oxide by using indirect fluorinating precursor
(1996-08-26)
Chang, KM
;
Wang, SW
;
Wu, CJ
;
Yeh, TH
;
Li, CH
In this letter, fluorinated silicon oxide (FxSiOy) films were deposited in the electron cyclotron resonance (ECR) chemical vapor deposition system with SiH4, O-2, and CF4 as the reaction gases. The CF4, in contrast to SiF4 or FSi(OC2H5)(3) used in other reports, is an indirect fluorinating source. The fluorinating mechanism is similar to that of the etching of oxide by fluorocarbon plasma, therefore, the thermal stability of the incorporated fluorine must strongly depend on the deposition temperature. It is found that the thermal stability and moisture resistance are greatly improved by increasing the deposition temperature. However, the higher deposition temperature also results in a higher compressed stress and dielectric constant. Besides, to get the moisture resistance, the deposition temperature must be above 300 degrees C. On the other hand, ECR-SiO2 (without fluorination), even deposited at room temperature, is shown to have a good water resistance. Therefore, by choosing deposition temperature for FxSiOy to have enough thermal tolerance and capping with ECR-SiO2, the moisture resistor is suggested for the inter metal dielectric applications.
Quasi-threshold graphs
(1996-08-27)
Yan, JH
;
Chen, JJ
;
Chang, GJ
;
應用數學系
;
Department of Applied Mathematics
Quasi-threshold graphs are defined recursively by the following rules: (1) K-1 is a quasi-threshold graph, (2) adding a new vertex adjacent to all vertices of a quasi-threshold graph results in a quasi-threshold graph, (3) the disjoint union of two quasi-threshold graphs is a quasi-threshold graph. This paper gives some new equivalent definitions of a quasi-threshold graph. From them, linear time recognition algorithms follow. We also give linear time algorithms for the edge domination problem and the bandwidth problem in this class of graphs.
Blends of poly(ethylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)] .3. Crystallization behavior observed by polarized light microscopy
(1996-08-29)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) has been melt-mixed at 293 degrees C with two types of co[poly(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester, designated as P28 and P82, at the level of 10 wt %. The different p-acetoxybenzoic acid/PET mole ratios are 20/80 in P28 and 80/20 in P82. The blends were heated to 305 degrees C and then cooled to 25 degrees C at rate of 10 degrees C/min. The crystalline morphology of these blends in the range from 25 degrees C to 305 degrees C is monitored by polarized light microscopy. Morphologic observations revealed a quicker appearance of crystalline in the blends upon the addition of 10 wt % copolyester as a nucleating agent. It is found that P28, which contains fewer POB units, is much more advantageous to the nucleation process than P82, which contains more POB units. According to the optical photomicrographs, sufficient uniformity of distribution of copolyester domains in the PET matrix is reached after 8 min blending. (C) 1996 John Wiley & Sons, Inc.
Blends of poly(ethylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)] .3. Crystallization behavior observed by polarized light microscopy
(1996-08-29)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) has been melt-mixed at 293 degrees C with two types of co[poly(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester, designated as P28 and P82, at the level of 10 wt %. The different p-acetoxybenzoic acid/PET mole ratios are 20/80 in P28 and 80/20 in P82. The blends were heated to 305 degrees C and then cooled to 25 degrees C at rate of 10 degrees C/min. The crystalline morphology of these blends in the range from 25 degrees C to 305 degrees C is monitored by polarized light microscopy. Morphologic observations revealed a quicker appearance of crystalline in the blends upon the addition of 10 wt % copolyester as a nucleating agent. It is found that P28, which contains fewer POB units, is much more advantageous to the nucleation process than P82, which contains more POB units. According to the optical photomicrographs, sufficient uniformity of distribution of copolyester domains in the PET matrix is reached after 8 min blending. (C) 1996 John Wiley & Sons, Inc.
Blends of poly(ethylene terephthalate) with co[poly(ethylene terephthalate-p-oxybenzoate)] .4. Interchange reactions and their effects on the thermal and crystallization behaviors
(1996-08-29)
Ou, CF
;
Lin, CC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Poly(ethylene terephthalate) (PET) was blended with a co[poly(ethylene terephthalate-p-oxybenzoate)] (POB-PET) copolyester which is a liquid crystalline polymer consisting of p-oxybenzoate and ethylene terephthalate units in a 40/60 mol ratio (P46). The level of P46 liquid crystalline polymer varies from 10 to 50 wt %. All the blends were prepared by melt-mixing in a Brabender Plasticorder at 275 degrees C for different times. The thermal and crystallization behaviors of blends depend on the blending time and the composition of blends, viz., the content of the p-oxybenzoate (POB) moiety incorporated into the blends. The interchange reactions detected by proton NMR analysis occur during the processing at a greater level if the blending time increases. These interchange reactions hinder the crystallization processes of PET and result in a decrease of the melting point, the heat of fusion, crystallization temperature, and the heat of crystallization of the original PET. The effects of the interchange reaction on thermal and crystallization behaviors of the blends may be attributed to the insertion of the rigid POB units into the soft PET chain. (C) 1996 John Wiley & Sons, Inc.
Effect of magnesium on mechanical properties of Al2O3/Al-Zn-Mg-Cu metal matrix composites formed by squeeze casting
(1996-08-30)
Hsieh, JH
;
Chao, CG
;
交大名義發表
;
材料科學與工程學系
;
National Chiao Tung University
Al2O3/Al-Zn-Mg-Cu composites containing 2.0 similar to 3.0 wt.% 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 microstructure and the fracture surface. Tensile tests were utilized to evaluate the mechanical properties. The aging behavior of the composites was studied by using differential scanning calorimetry technique 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 at 120 degrees C aging for 24 h.
A Laplace transform solution for tracer tests in a radially convergent flow field with upstream dispersion
(1996-09-01)
Chen, JS
;
Liu, CW
;
Chen, CS
;
Yeh, HD
;
環境工程研究所
When tracers are introduced into an injection borehole, noticeable concentration gradients at the injection well may cause a backward spreading of the initial plume during radially convergent tracer tests. Based on this concept a non-rigorous mathematical model is developed to estimate the effect of backward spreading. The injection well with an instantaneous slug input is treated as a mathematical source and the initial plume at the injection well is allowed to move upstream. The model assumes that advection and longitudinal dispersion are the transport mechanisms in a radially converging how field. The Laplace transform solution for solute concentration in an infinite porous medium is obtained using the method of Green's function. Breakthrough curves are computed by numerically inverting the Laplace transform solution. As compared with the solution of Moench, it is concluded that the presence of backward movement of initial plume yields a decrease of peak concentration and spreading out of breakthrough curve tails. This effect is significant for small Peclet numbers and can be neglected for large Peclet numbers. A field tracer test is carried out to demonstrate the applicability of the model. The experimental data are fitted with the type curves of this study, and those of Moench's study, to determine dispersivity and aquifer porosity. The results show that dispersivity values estimated by matching the two type curves are different. Because it neglects backward dispersion, Moench's solution overestimates the dispersivity and effective aquifer porosity.
The electroluminescence and photoluminescence characteristics of films of poly(phenylene vinylene)/gel-glass interpenetrating networks
(1996-09-01)
Chang, WP
;
Whang, WT
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A series of poly(phenylene vinylene) (PPV)/gel-glass composites were prepared from mixtures of PPV precursor and silicon alkoxide methanol solution by employing a sol-gel process. The PPV/gel-glass composite, which is an interpenetrating network (IPN) structure, is used as the emissive layer in a polymeric light-emitting diode (LED). The addition of a small quantity of titanium ethoxide catalysed the reaction of gel-glass formation, making the PPV/gel-glass formation successful without phase separation and the luminescence of the composite film tunable. The luminescence characteristics of these PPV/gel-glass composites are dependent on the raw-material composition of silicon alkoxide and the molar ratio of PPV to gel-glass. From the ultra-violet/visible absorption spectrum, the conjugated length of these PPV/gel-glass composites can be seen to be shorter than that of pure PPV. The resultant PPV/gel-glasses emit light over a wide range from yellow-green (550 nm) to blue (484 nm) in the photoluminescence spectrum. Electroluminescent devices made from PPV/gel-glass 4 composites in the molar ratios of 1/1.17 and 1/2.33 shows a maximum emission peak at 515 and 510 nm, respectively. These PPV/gel-glass 4 LEDs showed a higher relative electroluminescence efficiency and a longer lifetime than pure PPV. The improvement in the device stability is related to the reduction of the thermal vibration of PPV chains during operation and the hindrance of carrier mobility in the IPN structure. Copyright (C) 1996 Elsevier Science Ltd.
Fabrication and analyses of negative-birefringent thin film compensator with characteristic matrix
(1996-09-01)
Yoo, JC
;
Shieh, HPD
;
光電工程研究所
;
Institute of EO Enginerring
We fabricated a multilayer negative-birefringent film as a phase compensator to minimize light leakage from twisted nematic liquid crystal displays in oblique incidence. The multilayer film stack is composed of alternating thin layers of silicon dioxide and titanium dioxide, which is magnetron sputtered on the glass substrates. The experiment agrees with the characteristic matrix calculation. Since each layer is not ''thin'' enough compared with visible spectra, the multilayer thin stack induces interference phenomena, and consequently reduces the transmittance. In order to eliminate the interference, we optimized the multilayer thin film to achieve high transmittance in the region of visible spectra.
Microstructure and crystal phases of praseodymium oxides in zinc oxide varistor ceramics
(1996-09-01)
Lee, YS
;
Liao, KS
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The effect of sintering temperature on the microstructure and crystal phases of the intergranular praseodymium oxides in ZnO varistor ceramics was investigated using transmission electron microscopy and high-resolution electron microscopy. The ZnO grains were three-dimensionally separated from the intergranular praseodymium oxides. On the basis of microdiffraction analyses of the intergranular layer, the phase transformation from fcc-Pr6O11 into hcp-Pr2O3 was found when the sintering temperature increased from 1300 degrees to 1350 degrees C. The defect reaction equation and the decrease of donor concentration with increasing sintering temperature can verify the certainty of phase transition during the liquid-phase sintering observed by transmission elecron microscopy. Additionally, on the basis of the small variations of the breakdown voltage per grain boundary, the number of active grain boundaries is not a dominant factor for the donor concentration dependence on the sintering temperature.
A novel cladding structure for semiconductor quantum-well lasers with small beam divergence and low threshold current
(1996-09-01)
Yen, ST
;
Lee, CP
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
A novel cladding structure is proposed and analyzed for semiconductor quantum-well lasers ttl achieve a small vertical-beam divergence and a low threshold current density simultaneously, This cladding structure is designed to guide a wide optical mode but with a high peak intensity in quantum wells. The wide expansion of the optical mode results in a small beam divergence. In addition, the high optical intensity in quantum wells causes a low threshold current density, This novel cladding structure is optimized. The result shows that this type of cladding structures can achieve a beam divergence as small as 14.6 degrees while the threshold current density remains small.
Delayed precise invalidation - A software cache coherence scheme
(1996-09-01)
Hwang, TS
;
Lu, NP
;
Chung, CP
;
交大名義發表
;
資訊工程學系
Software cache coherence schemes are very desirable in the design of scalable multiprocessors and massively parallel processors. The authors propose a software cache coherence scheme named 'delayed precise invalidation' (DPI). DPI is based on compiler-time markings of references and a hardware local invalidation of stale data in parallel and selectively. With a small amount of additional hardware and a small set of cache management instructions, this scheme provides more cacheability and allows invalidation of partial elements in an array, overcoming some inefficiencies and deficiencies of previous software cache coherence schemes.
AC permeability of the flux-line liquid in the anisotropic high-T-c superconducting crystals
(1996-09-01)
Wu, CJ
;
Tseng, TY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
AC properties of the flux-line liquid in the anisotropic high-temperature superconducting crystals in a parallel field are theoretically investigated. The ac responses in the simple flux-flow regime are analyzed from associated effective ac-magnetic permeability calculated on the hydrodynamic theory basis. The responses are studied as functions of anisotropic ratio and sample dimensions. The results illustrate the influence of the platelet crystal's size on permeability in the anisotropic superconductors while in the isotropic superconductors, the relationship of responses between a square rod and cylinder is found. It indicates that the permeability of a cylinder can be essentially replaced by that of a square rod and vice versa. The geometric effect on response is also elucidated in the isotropic superconductors.
A novel structure for three-dimensional silicon magnetic transducers to improve the sensitivity symmetry
(1996-09-01)
Lin, HY
;
Lei, TF
;
Jeng, JJ
;
Pan, CL
;
Chang, CY
A three-dimensional silicon magnetic transducer with symmetric sensitivities in the x-, y- and z-directions and small cross sensitivity has been demonstrated. Devices are based on a design of a vertical Hall structure using the surrounding trench and symmetric design to suppress the cross sensitivity. The fabrication process is simple and can be used as a part of a standard integrated circuit process. The results show that almost equal sensitivities in all three components of magnetic field can be obtained by coating Ni/Co thin films on the backside of the substrates. The cross sensitivity is only 1.3% of the sensitivity.