Browsing by Issue Date, starting with "1998-05-15"

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Design and analysis of delay control for CBR services in ATM networks
(1998-05-15)
Chen, YC
;
Chan, CT
;
Hu, SC
;
資訊工程學系
;
Department of Computer Science
Asynchronous transfer mode (ATM) networks are designed to provide end-to-end transport of user data via virtual connections with specified quality of services (QOS), which is expected to be satisfied through effective traffic control mechanisms. This paper presents an adaptive delay-jitter control (ADJC) method that guarantees the delay bounds of constant bit rate (CBR) services in ATM networks. Our proposed method is based on a node-by-node time-frame scheme. Through both mathematical derivation and simulation, we have demonstrated that ADJC features a significant improvement over existing approaches in jitter delay, which can be reduced to one time-frame from end-to-end for CBR traffic. Simulation results have shown that CBR services receive satisfactory delay performance using our approach. (C) 1998 Elsevier Science B.V.
Scanning tunneling microscopy observation of surface reconstruction of Si(100) during chemical vapor deposition from Si2H6
(1998-05-15)
Lin, DS
;
物理研究所
;
Institute of Physics
This study employs real-time high-temperature scanning tunneling microscopy to examine the evolution of the surface atomic structure of Si(100) during homoepitaxy by chemical vapor deposition at 625 degrees C. At the initial stage, a (2 x n) structure is gradually formed, and the growth mode is pure step flow, followed by double step flow after a single-domain surface is obtained due to faster step advance of S-B than S-A. As growth proceeds, areas with c(4 x 4) symmetry appear, grow, and eventually cover the entire surface. (C) 1998 Elsevier Science B.V. All rights reserved.
Correlation of supercritical fluid extraction with supercritical fluid chromatography in aqueous matrixes
(1998-05-15)
Yu, T
;
Luo, SK
;
Chen, SJ
;
應用化學系
;
Department of Applied Chemistry
A mathematical model is presented for correlating supercritical fluid chromatography (SFC) in aqueous stationary phases with supercritical fluid extraction (SFE) in aqueous matrixes. A solar coaxial countercurrent chromatography apparatus was used for the SFC and SFE experiments. The SFE extraction vessel, i.e., the column for SFC, was mathematically divided into limited layers. During extraction, each layer was considered to undergo a chromatographic process. The plate heights of all the layers were regarded equal throughout the column because pressure drops in the system were negligible. Each layer's chromatographic capacity factor and peak width were calculated using true SFC experimental data, and the sum of all these peak distributions as a function of time gave the extraction efficiency. Accordingly, the SFE analyte recovery curve could be simulated using SFC data and this model. Since SFC operations are more straightforward than SFE operations, SFE optimization may be more easily achieved using this mathematical correlation. The simulated analyte data of large capacity factors matched the experimental results very well. Deviations gradually became greater as analyte capacity factors were decreased. A rationale is proposed that satisfactorily interprets this deviation trend.
Growth mode in Si(100)-(2x1) epitaxy by low-temperature chemical-vapor deposition
(1998-05-15)
Wu, PH
;
Lin, DS
;
物理研究所
;
Institute of Physics
This study investigates the growth processes of Si on Si(100)-(2x1) during ultrahigh vacuum chemical vapor deposition using disilane as the source gas. The evolution of surface morphology and atomic ordering during growth at temperatures between 300 and 600 degrees C is examined in real time by high-temperature scanning tunneling microscopy. Directly imaging various growth kinetic processes, such as pure step-flow growth, double step-flow growth, two-dimensional nucleation growth, and surface passivation at different substrate temperature ranges clearly illustrates the growth mechanisms for the model chemical vapor deposition growth system and provides interesting comparison with results of Monte Carlo simulations and those of solid phase molecular-beam epitaxy. [S0163-1829(98)05619-7].
Resonant ultrafast nonlinear optics of bulk semiconductors under electric-field modulation
(1998-05-15)
Lai, CM
;
Meng, HF
;
電子物理學系
;
物理研究所
;
Department of Electrophysics
In bulk direct-band-gap semiconductors the ground state of a (photoexcited) electron-hole system is normally an exciton gas, instead of an electron-hole plasma, as long as the carrier density is not too large. We demonstrate theoretically that, in the presence of an electric-field modulation, the energy of the plasma is decreased due to the induced charge-density fluctuation. As a results, the plasma becomes the ground state at much lower carrier densities, implying that the critical carrier density for the transition between these two states can be reduced. This transition provides a mechanism of nonlinear optics for bulk direct-band-gap semiconductors with picosecond relaxation time, large nonlinearity, and low pump intensity.
Computer-generated holographic diffuser for color mixing
(1998-05-15)
Chao, W
;
Chi, S
;
Wu, CY
;
Kuo, CJ
;
光電工程學系
An iterative algorithm for multiple incoming wavelengths is proposed to design a computer-generated holographic diffuser with the features of high light utilization efficiency and uniform color mixing. The amplitude transmittance of this computer-generated holographic diffuser is constant, while the phase transmittance consists of multiple phase levels. This diffuser is designed according to the Fraunhofer diffraction theory and can uniformly spread the different input light at the same time. The simulation results show that over 88% average far field amplitude transmission efficiency is achieved for each input light and the output uniformity is within 12.4%. (C) 1998 Elsevier Science B.V. All rights reserved.
Specification, validation, and verification of time-critical systems
(1998-05-15)
Shieh, SP
;
Chen, JN
;
資訊工程學系
;
Department of Computer Science
In this paper, we propose a new formalism, named the Timed Communicating Finite State Machine (Timed CFSM), for specifying and verifying time-critical systems. Timed CFSM preserves the advantages of CFSM, such as the ability to express communication, synchronization and concurrency in computer systems. A given time-dependent specification can be formalized as a Timed CFSM, from which the reachability graph is constructed to verify the correctness of the specification. To cope with the space explosion problem from which all reachability analysis methods suffer, we propose a space reduction algorithm to meet the space constraint of the verification environment. (C) 1998 Elsevier Science B.V.
一種想得都得不到的病
(1998-05-17)
管管
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.