Browsing by Issue Date, starting with "1998-06-01"

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Sequential distribution of copolyesters containing the phosphorus linking pendant groups characterized by H-1-NMR
(1998-06-01)
Chang, SJ
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A series of phosphorus-containing copolyesters were synthesized by polycondensation of terephthalic acid (TPA), ethylene glycol (EG) and 9,10-dihydro-10-[2, 3-di(hydroxycarbonyl)propyl]-9-oxa-10-phosphaphenanthrene-10 -oxide (DDP). Chemical structures of these phosphorus-containing copolyesters were characterized by H-1-n.m.r.. Experimental results show that these methylene protons of the ethylene glycol unit resonate at lower field than those of the DDP aliphatic protons. The resonance intensity of DDP aliphatic protons increases with the increase of the phosphorus content. The H-1-n.m.r. spectrum of the DDP aliphatic protons contain three peaks since the proton in H-C-P has greater coupling constant than that of H-C-C. The chemical shifts of these methylene protons in the ethylene glycol unit vary with different sequences. The methylene protons in the ethylene glycol of the T-E-T unit resonate at lower field than those of P-E-T(T-E-P) and P-E-P units. The monomer molar fraction, sequential distribution and degree of randomness of the phosphorus-containing copolyester were determined through analyses of the resonances of methylene protons in the ethylene glycol unit. The molar fractions of the DDP comonomer determined by n.m.r. analyses are close to the charged values in synthetic step and the values determined by an UV method. Moreover, the copolyesters were found to be as random copolymers with a degree of randomness equal to about 1. (C) 1998 Elsevier Science Ltd. All rights reserved.
Characterization and reduction of phase noise in passively mode-locked Ti : sapphire lasers with intracavity saturable absorbers
(1998-06-01)
Shieh, JM
;
Liu, SC
;
Pan, CL
;
光電工程學系
;
Department of Photonics
We characterize the phase noises (or timing jitter) of argon-ion-laser-pumped femtosecond Ti:sapphire lasers with intracavity dye saturable absorbers or saturable Bragg reflectors (SBR's). The significance of the finite lifetime of the absorbers is identified for what is the first time to our knowledge. We show that timing fluctuations of the mode-locked lasers can be suppressed significantly by optimization of intracavity gain bandwidth and group-velocity dispersion. A new active stabilization technique, based on the optoelectronic phase locked loop, is also demonstrated. The rms timing jitter (100-500 Hz) of the femtosecond passively mode-locked Ti:sapphire/dye and Ti:sapphire/SBR lasers operating at an average power of 200 mW is reduced to similar to 650 and 290 fs (500 Hz), respectively. (C) 1998 Optical Society of America.
Experimental study of a variable pressure damper on an automotive valve train
(1998-06-01)
Liou, JJ
;
Huang, G
;
Hsu, W
;
機械工程學系
;
Department of Mechanical Engineering
A variable pressure damper (VPD) is proposed here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve train. Valve bounce, component separation, spring vibration are observed in the testing. The VPD is shown to have significant improvement in reducing valve bouncing distance and surge vibration under 2985 rpm. Also, experimental results indicate that the component separation becomes more imminent at high speeds with larger damping forces. Here, in certain speed range, a proper frictional force provided by VPD is shown to be able to eliminate bouncing completely without causing component separation.
Experimental study of unsteady thermal characteristics and rotation induced stabilization of air convection in a bottom heated rotating vertical cylinder
(1998-06-01)
Ker, YT
;
Li, YH
;
Lin, TF
;
機械工程學系
;
Department of Mechanical Engineering
Flow stabilization by cavity rotation in convection of air (Pr = 0.7) in a vertical circular cylinder heated from below is studied experimentally. The cylinder is rotated at a constant speed about its own axis. In the experiment the time variations of the air temperature at selected locations in the cylinder are measured. Results are obtained for a cylinder with diameter D = 5 cm, height H = 10 cm, imposed temperature difference Delta T = 5 degrees C to 15 degrees C and rotation rate Omega from 0 to 346.1 rpm. The experimental data clearly show the stabilization of the thermal buoyancy driven irregular flow by the cavity rotation when the rotation rate is in certain ranges. For a given Delta T two different ranges of Omega exist for the flow to be stabilized. Outside these ranges the flow oscillates periodically or quasi-periodically in time. At given Delta T and Omega the temperature oscillation at various locations exhibits some change in amplitude but negligible change in frequency. However, change of the oscillation frequency with the rotation rate is nonmonotonic and is rather significant at high rotation rates. But this frequency change with the imposed temperature difference is small. (C) 1998 Elsevier Science Ltd. All rights reserved.
An experimental study of in-tube evaporation of R-22 inside a 6.5-mm smooth tube
(1998-06-01)
Wang, CC
;
Chiang, CS
;
Yu, JG
;
機械工程學系
;
Department of Mechanical Engineering
Two-phase flow pattern, friction, and heat transfer characteristics for R-22 inside a 6.5 mm smooth tube are reported in this study. The range of mass flux is between 50 and 700 kg/m(2) s. The flow pattern map proposed by Weisman et al. (Weisman, J., Duncan, D., Gibson, J., Crawford, T., 1979. Effect of fluid properties and pipe diameter on two-phase flow pattern in horizontal lines. Int. J. Multiphase Flow 5, 437-462) gave a satisfactory flow pattern prediction, and the Klimenko and Fyodorov (Klimenko, V.V., Fyodorov, M., 1990. Prediction of heat transfer for two-phase forced flow in channels of different orientation. In: Proceedings of the Ninth International Heat Transfer Conference, vol. 6, pp. 65-70) criterion shows an excellent classification of the stratified and unstratified flow pattern. The two-phase multipliers are strongly related to the flow pattern, and it is found that the two-phase multiplier is dependent upon mass velocities for stratified-wavy flow pattern. In addition, the two-phase heat transfer coefficient for stratified-wavy flow pattern is found to be insensitive to the change of vapor quality, and is approximately proportional to q(0.6-0 7). (C) 1998 Elsevier Science Inc. All rights reserved.
Sum-frequency generation from an isotropic chiral medium
(1998-06-01)
Yang, PK
;
Huang, JY
;
光電工程學系
;
Department of Photonics
We report a theoretical analysis of nonlinear optical sum-frequency generation from the bulk of a chiral liquid in the dipole approximation. In our theoretical formulation the circular birefringence effect of a chiral medium was properly taken into account. The angular dependence of the reflected and transmitted sum-frequency signals on the incident angles of two input beams was calculated to yield the optimal geometry for probing bulk chirality. We also derived a microscopic expression for the totally antisymmetric part of a second-order nonlinear optical susceptibility to elaborate unique features in the studies of chirality-related properties with sum-frequency generation. (C) 1998 Optical Society of America.
0.66 mu m InGaP/InGaAlP single quantum well microdisk lasers
(1998-06-01)
Pan, JS
;
Cheng, PH
;
Lee, TD
;
Lai, YC
;
Tai, KC
Visible emitting microdisk lasers with single InGaP/InGaAlP quantum well were demonstrated for the first time. Large spontaneous emission factors beta of 0.12 and 0.08 were observed for 5 and 10 mu m diameter disks, respectively.
Design of knockout concentrators
(1998-06-01)
Lin, YS
;
Shung, CB
;
Chen, JC
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The knockout switch architecture has been found attractive for large-scale switch implementations because of its satisfactory cell loss performance, with constant output buffer speed-up independent of switch dimension. The per port hardware complexity of a knockout concentrator, however, does grow linearly with the switch dimension. In the paper, several approaches are investigated to reduce the complexity of the knockout while retaining the cell loss performance. A bufferless hierarchical concentrator architecture with reduced hardware complexity is derived. The concentrator complexity can be further reduced by introducing buffers in the concentrator, and the trade-off is analysed. Furthermore, output grouping may be applied in the buffered hierarchical concentrator to reduce the per port complexity. Two large-scale switch design examples are derived using the proposed design approaches, producing a complexity reduction ranging from 1.2% to 89.7%.
Elastic solutions for a transversely isotropic half-space subjected to a point load
(1998-06-01)
Liao, JJ
;
Wang, CD
;
土木工程學系
;
Department of Civil Engineering
We rederive and present the complete closed-form solutions of the displacements and stresses subjected to a point load in a transversely isotropic elastic half-space. The half-space is bounded by a horizontal surface, and the plane of transverse isotropy of the medium is parallel to the horizontal surface. The solutions are obtained by superposing the solutions of two infinite spaces, one acting a point load in its interior and the other being free loading. The Fourier and Hankel transforms in a cylindrical co-ordinate system are employed for deriving the analytical solutions. These solutions are identical with the Mindlin and Boussinesq solutions if the half-space is homogeneous, linear elastic, and isotropic. Also, the Lekhnitskii solution for a transversely isotropic half-space subjected to a vertical point load on its horizontal surface is one of these solutions. Furthermore, an illustrative example is given to show the effect of degree of rock anisotropy on the vertical surface displacement and vertical stress that are induced by a single vertical concentrated force acting on the surface. The results indicate that the displacement and stress accounted for rock anisotropy are quite different for the displacement and stress calculated from isotropic solutions. (C) 1998 John Wiley & Sons, Ltd.
Multiple-cell square-type layout design for output transistors in submicron CMOS technology to save silicon area
(1998-06-01)
Ker, MD
;
Wu, CY
;
Huang, CC
;
Chen, TY
;
電子工程學系及電子研究所
A new multiple-cell square-type layout design is proposed to realize the large-dimension output transistors for submicron low-voltage CMOS ICs. By using this layout design, the layout area of CMOS output buffers can be effectively reduced 30-40% with respect to the traditional finger-type layout. The drain-to-bulk parasitic capacitance of the output transistors is also reduced 40% by this square-type layout. Experimental results in a 0.6 mu m CMOS process have shown that the maximum driving (sinking) capability per unit layout area of a CMOS output buffer realized by the proposed multiple-cell square-type layout is improved 54% (34%) more than that by the traditional finger-type layout. The human-body-model (machine-model) ESD robustness per unit layout area of the CMOS output buffer realized by the proposed multiple-cell square-type layout is increased 25.2% (17.3%) as comparing to that by the traditional finger-type layout. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.
Syntheses and characterization of organoimido complexes of niobium(V); Potential CVD precursors
(1998-06-01)
Chiu, HT
;
Lin, JC
;
Chuang, SH
;
Lee, GH
;
Peng, SM
New niobium imido complexes (RN)Nb(NEt2)(3) (R = Pr-n, Pr-i and Bu-t), potential precursors to grow niobium containing thin films by chemical vapor deposition (CVD), were prepared by reacting the corresponding (RN)NbCl(3)py(2) complexes (R = Pr-n, Pr-i and Bu-t; py = pyridine) with LiNEt2 in hydrocarbon solvents. The structures of (RN)NbCl(3)py(2) (R = Pr-i and Bu-t), determined by X-ray crystallography, are mononuclear with distorted octahedral geometries. For each complex, three chloride ligands are cia to the imido ligand and occupy meridional positions. One of two py ligands is cia to and the other is trans to the imido ligand. For ((PrN)-N-i)NbCl(3)py(2), the Nb = NPri bond distance (Angstrom) is 1.733(3) and the angle Nb=N-Pr-i angle (degrees) is 178.0(3). Crystal data: monoclinic, space group P2(1)/n, a = 8.805(2), b = 14.930(4), c = 13.407(3) Angstrom, beta = 93.37(2)degrees, V = 1759.5(7) Angstrom(3), Z = 4, D-c 1.565 g cm(-3). For ((BuN)-N-t)NbCl(3)py(2), the Nb=NBut bond distance (Angstrom) is 1.734(4) and the angle Nb=N-Bu-t angle (degrees) is 174.8(4). Crystal data: monoclinic, space group P2(1)/c, a = 9.609(1), b = 13.591(6), c = 14.615(2) Angstrom, beta = 90.05(1)degrees, V = 1908.5(9) Angstrom(3), Z = 4, D-c = 1.492 g cm(-3).
A novel two-step etching to suppress the charging damages during metal etching employing helicon wave plasma
(1998-06-01)
Cheng, HC
;
Lin, W
;
Kang, TK
;
Perng, YC
;
Dai, BT
A two-step etching has been performed to eliminate the plasma charging damages during helicon-wave plasma metal etching without selectivity loss, This technique utilized a normal etching recipe to remove the Al film and followed by an optimized etching recipe for the overetching step. By increasing the bias power and decreasing the source power, the optimum etching recipe can cause the plasma more directionally and reduce the Al charging damages. Eventually, the damage mechanism was also reported.
A two-machine flowshop scheduling heuristic with bicriteria objective
(1998-06-01)
Lee, CE
;
Chou, FD
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
This paper presents a O(N-2) heuristic algorithm to solve the two-machine flowshop scheduling with bicriteria objective to minimize the sum of makespan and total flow time. An integer programming model with N-2+2N variables and 3N constraints is also formulated to validate the performance of the heuristic scheduling algorithm proposed here. Experimental results demonstrate that the proposed algorithm can efficiently solve this problem with a high solution quality. Although the integer programming model provides the optimal solution, variables and constraints markedly increase when the number of jobs increases. Therefore, the optimal solution is not always attainable within the allowable time. The heuristic algorithm is much more practical in real world applications than the integer programming model.
A 1 logN parallel algorithm for detecting convex Hulls on image boards
(1998-06-01)
Lin, JC
;
Lin, JY
;
資訊工程學系
;
Department of Computer Science
By finding the maximum and minimum of {y(i) - mx(i) 1 less than or equal to i less than or equal to N} for certain slopes m, we propose here a simple and fast parallel algorithm to obtain the convex hull of N arbitrarily given points on an image hoard. The mathematical theory needed is included, and computation time is 1 log N.
Statistical distributions of Rician factor for radio LOS propagation in urban microcells
(1998-06-01)
Tarng, JW
;
Ju, KM
;
電信工程研究所
;
Institute of Communications Engineering
The Rician factor is an important parameter in evaluating the outage probability and reuse distance of cellular systems. From the measurement of 1.8 GHz radio propagation in outdoor urban microcells, it is found that the measured pdf of the Rician factor for low tier systems follows a lognormal distribution and the factor is independent on the propagation distance.
Direct determination of azimuth angles in photoelastic modulator system
(1998-06-01)
Chao, YF
;
Wang, CK
;
光電工程學系
;
Department of Photonics
Instead of the nulling method, a high-level intensity technique is proposed to determine the relative azimuth orientation of a photoelastic modulator and an analyzer. In a photoelastic modulating system, one can obtain a DC intensity distribution by varying the phase modulation amplitude at two azimuth angles of the analyzer, which are pi/4 apart from each other. The relative azimuth orientation can be determined by taking the ratio of the slopes of these two intensity distributions around the linear region of the zero point of the zero-order Bessel function. A similar technique is also applicable to wave plates for aligning their optical axes with the system.
An elucidation of solid incorporation of InGaN grown by metalorganic vapor phase epitaxy
(1998-06-01)
Ou, J
;
Chen, WK
;
Lin, HC
;
Pan, YC
;
Lee, MC
We carried out a systematic study on the solid incorporation of InGaN under various growth conditions using metalorganic vapor phase epitaxy (MOVPE). The solid distribution of InGaN was found to be very sensitive to the growth temperature, and the TMGa and TMIn flow rates. Experimental results indicated that at low Ga flow rates InGaN growth is essentially governed by thermodynamic factors, whereas at high growth rate the InGaN solid concentration is determined merely by the vapor composition in the gas phase. In regard to the effect of TMIn flow rates on InGaN growth, it was found that once In droplets form on the surface, the In growth efficiency correspondingly decreases significantly; accounting for the low In solid concentration in InGaN at high TMIn flow rates.
One and two-parameter blending for parametric surfaces
(1998-06-01)
Chuang, JH
;
Lien, FL
;
資訊工程學系
;
Department of Computer Science
Two formulations are proposed for computing the general blending of parametric surfaces. The first is an exact formulation that extends the concept of the affine potential method [11] and represents the blend exactly in a high dimensional space as the sweeping surface of the intersection between offsets of the base surfaces with radii satisfying a specific one-parameter curve. The second is a relatively complex formulation that defines the blend as the sweeping surface of the intersection between offsets of base surfaces with radii satisfying a specific two-parameter surface. To improve the interactive performance of these formulations, procedural approaches are proposed. Both formulations provide users with not only a simple and intuitive blending specification, but also a flexible shape control of the blending surface. Moreover, the formulations take the underlying geometry of the base surfaces into consideration.
Vague reasoning and knowledge representation using extended fuzzy Petri nets
(1998-06-01)
Chen, SM
;
Shiau, YS
;
資訊工程學系
;
Department of Computer Science
In this paper, we present an extended fuzzy Petri net model (EFPN) for modeling fuzzy IF-THEN rules and fuzzy IF-THEN-ELSE rules of a rule-based system, where the truth values of the propositions appearing in the rules are represented by vague values in [0, 1]. An efficient algorithm is also proposed to perform vague reasoning automatically. This vague reasoning capability allows computers to perform reasoning in a more flexible and more intelligent manner.
A novel hybrid coupler based on antiresonant reflecting optical waveguides
(1998-06-01)
Deng, JJ
;
Huang, YT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A novel hybrid coupler based on the antiresonant reflecting optical waveguides (ARROW's) is presented. This device consists of two parallel antiresonant reflecting optical waveguides with a tapered outermost cladding layer. Such a device can provide advantageous features of low radiation loss, low crosstalk at the output end, and compatible core dimensions and indexes with single-mode optical fibers. The staircase approximation and the eigenmode expansion analysis are used to analyze and optimize this device. In our design on a Si-substrate, radiation losses below 0.38 dB and extinction ratios below -20 dB for two waveguide channels are achieved. The beam propagation method (BPM) is also used to verify our design and analysis results.