Browsing by Issue Date, starting with "1998-05-18"

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管管娶親人生七十又逢春忘年絕配普天同羨
(1998-05-18)
賴素鈴
管管娶嬌娘,喜宴忒詩意
(1998-05-18)
江中明
Signs of nonlinear refraction in chloroaluminum phthalocyanine solution
(1998-05-18)
Wei, TH
;
Huang, TH
;
Lin, MS
;
應用化學系
;
Department of Applied Chemistry
Opposite signs of nonlinear refraction in chloroaluminum (ClAl) phthalocyanine (Pc) dissolved in methanol are observed using the Z-scan technique with two output modes of a frequency-doubled, Q-switched, mode-locked Nd:YAG laser operating at 10 Hz. Using the single picosecond (ps) pulses switched out of the pulse trains, positive nonlinear refraction is observed and attributed to population transitions among ClAlPc's singlet states. Using the full nanosecond pulse trains, a sign change of nonlinear refraction relative to that of single ps-pulse excitation is observed, and is attributed to the heat-induced temperature rise and the population relaxing to CLAlPc's triplet states. (C) 1998 American Institute of Physics. [S0003-6951(98)01720-3].
A note on the gauge equivalence between the Manin-Radul and Laberge-Mathieu super KdV hierarchies
(1998-05-22)
Shaw, JC
;
Tu, MH
;
應用數學系
;
Department of Applied Mathematics
The gauge equivalence between the Manin-Kadul and Labarge-Mathieu super KdV hierarchies is revisited. Apart from the Inami-Kanno transformation, we show that there is another gauge transformation which also possesses the cancnical property. We explore the relationship of these two gauge transformations from the Kupershmidt-Wilson theorem viewpoint and, as a by-product, obtain the Darboux-Backlund transformation for the Manin-Radul super KdV hierarchy. The geometrical intepretation of these transformations is also briefly discussed.
詩壇訊息
(1998-05-23)
本報訊
詩畫聯展相互輝映
(1998-05-23)
蔡美娟
Chemical transformation of tetraacetal tetraoxa-cages to aza-cages and amido-cages mediated by iodotrimethylsilane and the combination of chlorotrimethylsilane and sodium iodide in nitriles
(1998-05-28)
Chern, JH
;
Wu, HJ
;
應用化學系
;
Department of Applied Chemistry
An one-pot conversion of tetraacetal tetraoxa-cages la-e to aza-cages 2a-e mediated by iodotrimethylsilane in alkyl nitriles at 25 degrees C via the ring expansion compound 9 as the reaction intermediate was discovered. A Ritter-type reaction was proposed for the mechanism of this conversion. On the other hand, reaction of tetraacetal tetraoxa-cages 1 with Me3SiCl and NaI in nitriles at 25 degrees C gave the amido-cages 12. Conjugated nitriles and Lewis acids, such as TiCl4 or BF3 . OEt2 were found to be ineffective for the conversion of era-cages to aza-cages. The structures of 2a and chemical transformation product 16 were proven by X-ray analysis. (C) 1998 Elsevier Science Ltd. All rights reserved.
Evaluation of spatial Green's functions for microstrips: fast Hankel transform algorithm and complex image method
(1998-05-28)
Hsieh, RC
;
Kuo, JT
;
電信工程研究所
;
Institute of Communications Engineering
The fast Hankel transform (FI-IT) algorithm and complex image method (CIM) are employed to evaluate the spatial-domain Green's function for a multilayered microstrip structure. The results are compared with those obtained by exact numerical integration. It is found that both techniques have high efficiency and the FHT has better accuracy than the CIM.
On the arrangement graph
(1998-05-29)
Chiang, WK
;
Chen, RJ
;
資訊工程學系
;
Department of Computer Science
The arrangement graph was proposed as a generalization of the star graph topology. In this paper we investigate the topological properties of the (n, k)-arrangement graph A(n.k). It has been shown that the (n, n - 2)-arrangement graph A(n,n-2) is isomorphic to the n-alternating group graph AG,. In addition, the exact value of average distance of A(n,k) has been derived. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
老頑童管管只許髮蒼不讓心老
(1998-05-31)
曹?怡
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.