Browsing by Issue Date, starting with "2006-05-08"

Now showing 1 - 20 of 63286

All-optical pulse data generation in a semiconductor optical amplifier gain controlled by a reshaped optical clock injection
(2006-05-08)
Lin, GR
;
Chang, YC
;
Yu, KC
;
光電工程學系
;
Department of Photonics
Wavelength-maintained all-optical pulse data pattern transformation based on a modified cross-gain-modulation architecture in a strongly gain-depleted semiconductor optical amplifier (SOA) is investigated. Under a backward dark-optical-comb injection with 70% duty-cycle reshaping from the received data clock at 10 GHz, the incoming optical data stream is transformed into a pulse data stream with duty cycle, rms timing jitter, and conversion gain of 15%, 4 ps, and 3 dB, respectively. The high-pass filtering effect of the gain-saturated SOA greatly improves the extinction ratio of data stream by 8 dB and reduces its bit error rate to 10(-12) at -18 dBm. (c) 2006 American Institute of Physics.
Stateful session handoff for mobile WWW
(2006-05-08)
Hsieh, MD
;
Wang, TP
;
Tsai, CS
;
Tseng, CC
;
資訊工程學系
This paper proposes a web session handoff system that can hand over not only stateless but also stateful sessions between homogenous and heterogeneous user devices to enable uninterrupted and seamless web access. The proposed system adopts a proxy-based approach and an optional client-assisted scheme in order to track and hand over session information. In the proposed system, a session is registered at a User Agent Proxy (UAP) and then tracked by the UAP so that the session can be handed over from one device via the UAP to another device. In addition to session information tracked by a UAP, the UAP can hand over more comprehensive session information by using the client-assisted scheme. Compared with client-based approaches, our design has several advantages, such as less modification to user devices, practicability, and fault tolerance. We have implemented a UAP on a PC and client programs for both PC and PDA. The implementation can successfully hand over between PC and PDA a stateful session for online shopping applications. (C) 2005 Elsevier Inc. All rights reserved.
Self-healing fiber Bragg grating sensor system
(2006-05-09)
Chi
;
Sien
;
Peng
;
Peng-Chun
;
Lin
The present invention is a self-healing fiber Bragg grating sensor system which comprises a central office, at least one network node, at least one 2×2 optical switch and at least one fiber Bragg grating. The network node can be made of optical switch. When the fiber for the sensor system is broken, sensing signals are discriminated in different paths provided by the network nodes to avoid stop working once the fiber is broken, by which the self-healing ability of the system is greatly improved. Besides, by using the structure of fiber laser in the present invention, the power output and the signal-to-noise ratio can be greatly increased. Accordingly, the present invention is to design a fiber sensor system with low cost and high capacity and with capability of self-healing.
Discovery of different types of inhibition between the human and Thermotoga maritima alpha-fucosidases by fuconojirimycin-based derivatives
(2006-05-09)
Ho, CW
;
Lin, YN
;
Chang, CF
;
Li, ST
;
Wu, YT
An efficient method for examining the selectivity of inhibitors on two alpha-fucosidases, one from Thermotoga maritima and the other from human, was established. The X-ray crystal structure of the former enzyme makes possible the homology modeling of the human alpha-fucosidase, indicating the major difference between both enzymes in the periphery of the catalytic site. To investigate the difference at the molecular level, a variety of fuconojirimycin (FNJ) derivatives with substitution at Cl, C2, C6, or N were rapidly prepared in microplates and screened without purification for the inhibition activities of the two alpha-fucosidases. Among the molecules that were tested, only the substitution at Cl can significantly enhance the inhibitory potency, in contrast to the control (no substitution) and compounds with substitution at other positions. The majority of Cl-substituted FNJs were found to be slow tight-binding inhibitors of the Thermotoga enzyme, while acting as the reversible inhibitors of the human fucosidase. The best inhibitor exhibited 13700-fold difference in affinity between the two enzymes, which was attributed to the dissimilar aglycon binding site. Further investigations were carried out, including site-directed mutagenesis, the comparison of K-i values among the wild type and mutants, and the intrinsic fluorescence change upon inhibitor titration, all supporting the idea that Tyr64 and Tyr267 of the Thermotoga alpha-fucosidase are critically involved in closely interacting with the aglycon of inhibitors. The increased level of contact thus induced conformational change, leading to the observed slow tight-binding inhibition.
The role of charge-transfer integral in determining and engineering the carrier mobilities of 9,10-di(2-naphthyl)anthracene compounds
(2006-05-10)
Tse, SC
;
So, SK
;
Yeung, MY
;
Lo, CF
;
Wen, SW
The charge transporting properties of t-butylated 9,10-di(2-naphthyl)anthracene (ADN) compounds have been investigated experimentally and computationally in relation to their molecular structures. The ADN compounds are found to be ambipolar with both electron and hole mobilities in the range of 1-4 x 10(-7) cm(2) V-1 s(-1) (electric field 0.5-0.8 MV/cm). As the degree of t-butylation increases, the carrier mobility decreases progressively. The mobility reduction was examined by Marcus theory of reorganization energies. All ADN compounds possess similar reorganization energies of similar to 0.3 eV. The reduction of carrier mobilities with increasing t-butylation can be attributed to a decrease in the charge-transfer integral or the wavefunction overlap. (c) 2006 Elsevier B.V. All rights reserved.
Trench gap-tilling copper by ion beam sputter deposition
(2006-05-10)
Han, S
;
Lee, TL
;
Yang, CJ
;
Shih, HC
;
材料科學與工程學系
The ion beam sputter deposition (IBSD) and electroless plating techniques have been combined to achieve the precipitation of Cu onto an amorphous (a)-TaN diffusion barrier layer in order to accomplish the ultralarge-scale-integrated interconnect metallization. The copper-filled specimens were annealed at various temperatures in a reduced atmosphere. The preferred orientation was analyzed by X-ray diffraction, and field emission scanning electron microscopy was used to elucidate the growth mechanism of the trench-filled electroless deposited Cu film on the Cu seeded layer by IBSD. The Cu(1 1 1) texture was strengthened by annealing at 300 degrees C for 1 h. The surface roughness increased notably with increasing annealing temperature. The electrical resistivity of the as-deposited copper film (3.05 mu Omega cm) decreased with increasing annealing temperature. The major contribution of this study is to successfully combine the techniques of IBSD and electroless plating for the Cu gap-filling of submicron trenches with an excellent step coverage. (c) 2006 Published by Elsevier B.V.
Dissociation of energy-selected c-C3H6S+ studied with threshold photoelectron-photolon coincidence experiments and calculations
(2006-05-10)
Chiang, SY
;
Fang, YS
;
Lin, CN
;
應用化學系
;
Department of Applied Chemistry
The dissociation of energy-selected c-C3H6S+ was investigated in a region 10.2-10.9 eV with a threshold photoelectron-photoion coincidence technique. Branching ratios and average releases of kinetic energy for channel c-C3H6S+ -> H2CS+ + C2H4 were derived from coincidence mass spectra. The measured small releases of kinetic energy near the appearance onset agree with statistical calculations; a linearly extrapolated threshold at 10.39 +/- 0.01 eV agrees with a predicted energy 10.35 eV with the GAUSSIAN-3 method. We discuss plausible mechanisms for c-C3H6S+ dissociating to CH3CS+ + CH3 based on G3B3 calculations to rationalize the absence of CH3CS+ signal in these experiments. (c) 2006 Elsevier B.V. All rights reserved.
Mechanistic study on the continuous flow electrocoagulation of silica nanoparticles from polishing wastewater
(2006-05-10)
Den, W
;
Huang, CP
;
Ke, HC
;
環境工程研究所
;
Institute of Environmental Engineering
This study investigates the removal mechanisms involved in the monopolar, continuous-flow electrocoagulation of a polishing wastewater containing negatively charged silica particles. Using iron as the anodes, the mechanisms were inferred from the experimental observations of the changes in pH, zeta-potential, and turbidity as a function of reaction time, as well as from the sludge characterization. Two types of distinct mechanisms were observed, one involving particle destabilization by oppositely charged ferrous ions and the other involving coprecipitation or enmeshment of silica particles with the iron hydroxides. The former mechanism was apparently responsible for the formation of "surface flocs", whereas the latter one was responsible for the "sediment sludge". The sludge collected separately from the two "sinks" was distinctly different in both physical appearance and settling velocity. Furthermore, based on the sheer quantity of the surface flocs and the sediment sludge, the two mechanisms involved in the electrocoagulation process were equally important to the silica removal.
A novel method to improve VCSELs oxide-confined aperture uniformity using selective As+-implanted underlying layer
(2006-05-10)
Huang, HW
;
Kao, CC
;
Chang, YA
;
Kuo, HC
;
Laih, LH
We report the utilization of an selective As+-implanted underlying layer and regrowth method to enhance and control the wet thermal oxidation rate for 850 nm oxide-confined VCSEL. The oxidation rate of the As'-implanted device showed a four-fold increase over the non-implanted one at the As' dosage of 1 x 10(16) cm(-1) and the oxidation temperature of 400 degrees C. The 50 side-by-side As'-implanted oxide-confined VCSELs fabricated using the method achieved very uniform performance with a deviation in threshold current Of Delta I-th similar to 0.2 mA and slope-efficiency of Delta S.E. similar to 3%. Finally, we accumulated life test data for oxide-confined VCSELs with As'-implanted underlying layer up to 1000 h at 80 degrees C/15 mA. (c) 2005 Elsevier B.V. All rights reserved.
支援模式轉換之無線區域網路的介質存取控制器及其轉換方法
(2006-05-11)
林衍良
;
張軒彬
;
張瑞川
本發明提出一種支援模式轉換之無線區域網路的介質存取控制器及其轉換方法，利用一實體層偵測所處環境中之訊號強弱，並將偵測到較強訊號之模式標誌值寫入一暫存器，當與通訊系統中之模式標誌值不符時，便通知一介質存取控制器進行模式轉換，實體層接著發出一中斷訊號給一中央處理器，並透過一DMA模組及一記憶體將該模式標誌值送至中央處理器以比較，並可利用一溝通模組以存取記憶體內之模式標誌值，以提供介質存取控制層之對外介面，當模式標誌值不符合所處環境中之訊號時，便利用一位介質存取控制器內之軟體層進行模式轉換。本發明可進行模式轉換，且提供更穩定的連線服務、較低之電力消耗與較低的製作成本與難度，並加速模式轉換的時間。
A gain-clamped S-band erbium-doped fiber amplifier using fiber Bragg grating
(2006-05-15)
Yeh, CH
;
Lin, MC
;
Chi, S
;
光電工程學系
;
Department of Photonics
We propose and investigate experimentally a gain-clamped S-band erbium-doped fiber amplifier module, employing a fiber Bragg grating to serve as a reflected element to lase a saturated tone injected into the module, by forward optical feedback method. In addition, different injected powers of the saturated tone are used to realize the performances of gain and noise figure for the proposed amplifier over the effectively wavelength range of 1478-1520 nm. (C) 2005 Elsevier B.V. All rights reserved.
Vortex dynamics in spacing-graded array of defects on a niobium film
(2006-05-15)
Wu, TC
;
Horng, L
;
Wu, JC
;
Hsiao, CW
;
Kolacek, J
We have investigated the vortex dynamics in the niobium films having a spacing-graded array of pinning sites. The samples were fabricated by using electron beam lithography through a lift-off technique. The pinning sites of 200 nm in diameter were arranged with a constant hole-defect separation in x-axis direction and graded separation in y-axis direction from 392 nm to 408 nm. The magneto-resistance measurements and current-voltage characteristics were explored with the external magnetic field applied perpendicular to the film plane. Dc current-voltage measured at matching field revealed two distinct curves resulted from the positive and negative applied current directions, respectively. This is believed to be due to an asymmetry pinning potential formed in the spacing-graded array of holes, giving rise to asymmetry Lorentz forces. De voltage drop measured with respect to the ac current applied along the x-axis of the sample showed two separated maxima, which can be explained using the dynamics of pinned vortex lattice and interstitial vortices in the asymmetry pinning landscape. (c) 2006 Elsevier B.V. All rights reserved.
The fragment transformation method to detect the protein structural motifs
(2006-05-15)
Lu, CH
;
Lin, YS
;
Chen, YC
;
Yu, CS
;
Chang, SY
To identify functional structural motifs from protein structures of unknown function becomes increasingly important in recent years due to the progress of the structural genomics initiatives. Although certain structural patterns such as the Asp-His-Ser catalytic triad are easy to detect because of their conserved residues and stringently constrained geometry, it is usually more challenging to detect a general structural motifs like, for example, the beta beta alpha-metal binding motif, which has a much more variable conformation and sequence. At present, the identification of these motifs usually relies on manual procedures based on different structure and sequence analysis tools. In this study, we develop a structural alignment algorithm combining both structural and sequence information to identify the local structure motifs. We applied our method to the following examples: the beta beta alpha-metal binding motif and the treble clef motif. The beta beta alpha-metal binding motif plays an important role in nonspecific DNA interactions and cleavage in host defense and apoptosis. The treble clef motif is a zinc-binding motif adaptable to diverse functions such as the binding of nucleic acid and hydrolysis of phosphodiester bonds. Our results are encouraging, indicating that we can effectively identify these structural motifs in an automatic fashion. Our method may provide a useful means for automatic functional annotation through detecting structural motifs associated with particular functions.
Aluminum incorporation into AlGaN grown by low-pressure metal organic vapor phase epitaxy
(2006-05-15)
Huang, GS
;
Yao, HH
;
Lu, TC
;
Kuo, HC
;
Wang, SC
Aluminum (Al) incorporation in AlxGa1-xN films grown by low-pressure metal organic vapor phase epitaxy using trimethylaluminum (TMAl) and trimethylgallium as group III precursors has been systematically studied. The solid phase Al composition of the AlxGa1-xN films varied nonlinearly with the Al gas phase composition. The incorporation kinetics of AlxGa1-xN alloy has been analyzed by using an adsorption-trapping model. Two parameters were used to characterize the properties of Al incorporation, i.e., the capture radius and the adsorption time of Al atoms. An exponential function of the Al composition of the AlxGa1-xN films versus the TMAl gas flow rate was obtained. It was demonstrated that the adsorption time of the Al atom was larger than the growth time of one atomic layer. The effects of ammonia flow rate, crystal growth rate, and growth temperature on the adsorption parameters were also discussed. (c) 2006 American Institute of Physics.
Whispering gallery mode of modified octagonal quasiperiodic photonic crystal single-defect microcavity and its side-mode reduction
(2006-05-15)
Lee, PT
;
Lu, TW
;
Tsai, FM
;
Lu, TC
;
Kuo, HC
Single-mode lasing action is obtained from a modified octagonal quasiperiodic photonic crystal single-defect microcavity which supports a well-confined whispering gallery mode with ultralow threshold and high-quality factor. Side-mode reduction is achieved by inserting a central air-hole in the cavity region. (c) 2006 American Institute of Physics.
Smooth solutions to a class of quasilinear wave equations
(2006-05-15)
Hsu, CH
;
Lin, SS
;
Makino, T
;
應用數學系
;
Department of Applied Mathematics
This article investigates the existence/nonexistence of smooth solutions of nonlinear vibration equations which arise from the one-dimensional motion of polytropic gas without external forces contained in a finite interval. For any fixed arbitrarily long time, we show that there are smooth small amplitude solutions of the nonlinear equations for which the periodic solutions of the linearized equation are the first-order approximations. On the other hand, when the nonlinearity is strictly convex or concave, there exists no time-periodic solutions which are twice continuously differentiable. An example of possible singularities which occur at the second derivatives is illustrated. We also give another kind of exact solutions with singularity such that shocks occur after a finite time. Furthermore, we get an estimate of the life span of smooth solutions to the initial-boundary value problem. (c) 2005 Elsevier Inc. All rights reserved.
Dual-stage soliton compression of a self-started additive pulse mode-locked erbium-doped fiber laser for 48 fs pulse generation
(2006-05-15)
Lin, YT
;
Lin, GR
;
光電工程學系
;
Department of Photonics
A dual-stage single-mode fiber (SMF) and large-effective-area fiber (LEAF) link for generating 48 fs pedestal-free pulses from a 40 MHz self-started additive pulse mode-locked erbium-doped fiber laser (APM-EDFL) with output peak power and pulse energy of 16 kW and 500 pJ, respectively, is demonstrated. With the SMF+LEAF link, a maximum pulse-width compression ratio of 7 and an optimized pulse-energy confining ratio of up to 85% can be achieved, and the soliton self-frequency shift effect of the APM-EDFL pulse can be greatly suppressed. (c) 2006 Optical Society of America
Temperature-dependent optical properties of In0.34Ga0.66As1-xNx/GaAs single quantum well with high nitrogen content for 1.55 mu m application grown by molecular beam epitaxy
(2006-05-15)
Lai, FI
;
Kuo, SY
;
Wang, JS
;
Hsiao, RS
;
Kuo, HC
The temperature dependence of optical properties of InGaAsN/GaAs single-quantum wells grown by solid source molecular beam epitaxy (MBE) with N contents varied from 0% to 5.3% was investigated by photoluminescence (PL). The evolution of the peak positions of InGaAs/GaAs sample are in agreement with the empirical Varshni model. However, pronounced temperature-dependent S-shaped peak positions and N-shaped linewidth were observed in PL spectra while increasing nitrogen concentration. The activation energy of InGaAsN/GaAs single quantum well (SQWs) is observed to decrease with nitrogen incorporation, which is contrary to the expectation of the bandgap reduction. This phenomenon suggests that the existence of defect-related nonradiative processes is due to nitrogen incorporation. The results of measurement demonstrate that the nitrogen incorporation into the InGaAsN has strong influence not only on carrier localization but also on the optical quality. In addition, the growth of high nitrogen content (5.3%) shows that the InGaAsN might be the potential candidate for long-wavelength optoelectronic devices. (c) 2006 Elsevier B.V. All rights reserved.
10 Gbit/s all-optical non-return to zero-return-to-zero data format conversion based on a backward dark-optical-comb injected semiconductor optical amplifier
(2006-05-15)
Lin, GR
;
Yu, KC
;
Chang, YC
;
光電工程學系
;
Department of Photonics
By using a semiconductor optical amplifier backward injected by a dark-optical-comb pulse train at 10 GHz, we demonstrate a 10 Gbit/s all-optical nonreturn-to-zero (NRZ) to return-to-zero (RZ) format conversion of an incoming optical pseudorandom binary sequence (PRBS) data strieam. Both the polarity and the wavelength of data are conserved during format conversion. Without any preamplification, the extinction ratio of degraded optical NRZ PRBS data is greatly improved from 7.13 to 13.6 dB after NRZ-to-RZ conversion. An ultralow bit-error rate of 10(-12) at a data rate as high as 10 Gbits/s is obtained with a received optical power of-18.3 dBm. The converted RZ PRBS data exhibit a negative power penalty of > 3.7 dB compared with the NRZ PRBS data at a bit-error rate of 10(-12). (c) 2006 Optical Society of America
An optimization model for Web content adaptation
(2006-05-15)
Jan, RH
;
Lin, CP
;
Chern, MS
;
資訊工程學系
;
Department of Computer Science
This paper considers Web content adaptation with a bandwidth constraint for server-based adaptive Web systems. The problem can be stated as follows: Given a Web page P consisting of n component items d(1), d(2),...,d(n) and each of the component items d(i) having J(i) versions d(i1), d(i2),... d(ut), for each component item d(i) select one of its versions to compose the Web page such that the fidelity function is maximized subject to the bandwidth constraint. We formulate this problem as a linear multi-choice knapsack problem (LMCKP). This paper transforms the LMCKP into a knapsack problem (KP) and then presents a dynamic programming method to solve the KP. A numerical example illustrates this method and shows its effectiveness. (c) 2005 Elsevier B.V. All rights reserved.