Browsing by Issue Date, starting with "2000-03-16"

Now showing 1 - 20 of 78474

Heuristic fuzzy-neuro network and its application to reactive navigation of a mobile robot
(2000-03-16)
Song, KT
;
Sheen, LH
;
電控工程研究所
;
Institute of Electrical and Control Engineering
A novel pattern recognition approach to reactive navigation of a mobile robot is presented in this paper. A heuristic fuzzy-neuro network is developed for pattern-mapping between quantized ultrasonic sensory data and velocity commands to the robot. The design goal was to enable an autonomous mobile robot to navigate safely and efficiently to a target position in a previously unknown environment. Useful heuristic rules were combined with the fuzzy Kohonen clustering network (FKCN) to build the desired mapping between perception and motion. This method provides much faster response to unexpected events and is less sensitive to sensor misreading than conventional approaches. It allows continuous, fast motion of the mobile robot without any need to stop for obstacles. The effectiveness of the proposed method is demonstrated in a series of practical tests on our experimental mobile robot. (C) 2000 Elsevier Science B.V. All rights reserved.
Tracking a near-field moving target using fuzzy neural networks
(2000-03-16)
Ma, CW
;
Teng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
In this paper we explore the problem of tracking a near-field moving target using fuzzy neural networks (FNNs). The moving target radiates narrow band waves that impinge on an array of passive sensors. At a particular time instance, the location of the target is estimated by several judiciously constructed FNN-based angle and distance estimators. When the target is moving, its trajectory can be on-line estimated due to the parallel and real-time computational capability of the FNNs. Computer simulation results illustrate the performance of the FNN-based angle estimator, distance estimator, and the near-field moving target tracker. (C) 2000 Elsevier Science B.V. All rights reserved.
Reduction of epitaxial alignment in n(+)-p poly-Si emitter diode due to gettering of P and As by Ar implantation
(2000-03-16)
Lee, LS
;
Lee, CL
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
It is demonstrated that Ar implantation can retard the epitaxial realignment of poly-Si/Si in an As- or P-doped n(+)-p poly-emitter diode during BF2 implantation. This is believed to be due to the gettering of As, P, and F by bubble-like defects created by the Ar implantation used to reduce the pile-up of these dopants at the poly-Si/Si interface. Consequently, there is less break-up of the interface oxide, resulting in a reduction in epitaxial realignment.
Robot learning schemes that trade motion accuracy for command simplification
(2000-03-16)
Young, KY
;
Lee, JF
;
Jou, HJ
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This study was inspired by the human motor control system in its ability to accommodate a wide variety of motions. By contrast, the biologically inspired robot learning controller usually encounters huge learning space problems in many practical applications. A hypothesis for the superiority of the human motor control system is that it may have simplified the motion command at the expense of motion accuracy. This tradeoff provides an insight into how fast and simple control can be achieved when a robot task does not demand high accuracy. Two motion command simplification schemes are proposed in this paper based on the equilibrium-point hypothesis for human motion control. Investigation into the tradeoff between motion accuracy and command simplification reported in this paper was conducted using robot manipulators to generate signatures. Signature generation involves fast handwriting, and handwriting is a human skill acquired via practice. Because humans learn how to sign their names after they learn how to write, in the second learning process, they somehow learn to trade motion accuracy for motion speed and command simplicity, since signatures are simplified forms of original handwriting. Experiments are reported that demonstrate the effectiveness of the proposed schemes. (C) 2000 Elsevier Science B.V. All rights reserved.
Power PHEMT with compact device layout for low voltage CDMA application
(2000-03-16)
Chang, EY
;
Lee, DH
;
Chen, SH
;
Chang, HC
;
材料科學與工程學系
A high efficiency low voltage operation dual delta-doped AlGaAs/ InGaAs/GaAs pseudomorphic high electron mobility transistor (PHEMT) for low voltage code division multiple access (CDMA) application has been developed. When tested at 2.4V and 1.9GHz under IS-95 CDMA modulation, the 20.16mm PHEMT device was found to have a linear output power of 28dBm with a power added efficiency of 30.2%. The device also has a saturation power of 30.0dBm with a power added efficiency of 61.5%. The high efficiency and linearity of the PHEMT at low bias voltage is attributed to the use of the dual delta-doped PHEMT structure and to the reduction of the size of the device layout. The device is suitable for low voltage CDMA applications.
Temperature dependence of RHEED oscillation in homoepitaxial growth of SrTiO3(100) films on stepped substrates
(2000-03-20)
Lee, JY
;
Juang, JY
;
Wu, KH
;
Uen, TM
;
Gou, YS
Homoepitaxial growth of SrTiO3 (STO) films on STO(100) substrates with unit-cell-high steps manifests itself by a marked change in the intensity oscillations of the specular reflectivity of reflection high-energy electron diffraction (RHEED) oscillations with increasing temperature. Atomic force microscopy (AFM) revealed a high density of growing islands distributed all over the edges and terraces of the pre-existing steps at lower deposition temperatures. In response, the RHEED intensity exhibits an 'overdamped' profile with no oscillation. At higher deposition temperatures (T-s approximate to 500 degrees C), larger (approximate to 40 nn) but fewer islands were observed to form preferentially on the step edges with a gradually recovered RHEED intensity, followed by RHEED oscillations after a few monolayers of coverage. At even higher growth temperatures, immediate periodic oscillations in RHEED intensity were observed. However, the temperature dependence of the oscillation period indicates that it may not be directly related to a layer-by-layer growth mode, as is generally believed. (C) 2000 Elsevier Science B.V. All rights reserved.
On the alpha-labeling number of bipartite graphs
(2000-03-21)
El-Zanati, S
;
Fu, HL
;
Shiue, CL
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應用數學系
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Department of Applied Mathematics
In this note we show that the alpha-labeling number of a bipartite graph G is bounded, which proves a conjecture of Snevily. (C) 2000 Elsevier Science B.V. All rights reserved.
On the alpha-labeling number of bipartite graphs
(2000-03-21)
El-Zanati, S
;
Fu, HL
;
Shiue, CL
;
應用數學系
;
Department of Applied Mathematics
In this note we show that the alpha-labeling number of a bipartite graph G is bounded, which proves a conjecture of Snevily. (C) 2000 Elsevier Science B.V. All rights reserved.
Cellular neural networks: Mosaic pattern and spatial chaos
(2000-03-21)
Juang, J
;
Lin, SS
;
應用數學系
;
Department of Applied Mathematics
We consider a cellular neural network (CNN) with a bias term z in the integer lattice Z(2) on the plane R-2. We impose a symmetric coupling between nearest neighbors, and also between next-nearest neighbors. Two parameters, a and epsilon, are used to describe the weights between such interacting cells. We study patterns that can exist as stable equilibria. In particular, the relationship between mosaic patterns and the parameter space (z, a; epsilon) can be completely characterized. This, in turn, addresses the so-called learning problem in CNNs. The complexities of mosaic patterns are also addressed.
Mutation at noncysteine positions eliminates the oxidation/reduction effect on the activity of phenol sulfotransferase.
(2000-03-26)
Yang, YS
;
生物科技學系
;
Department of Biological Science and Technology
Apodised fibre Bragg gratings fabricated with uniform phase mask using low cost apparatus
(2000-03-30)
Yang, CC
;
Lai, YC
;
光電工程學系
;
Department of Photonics
New exposure schemes for fabricating apodised fibre Bragg gratings using a uniform phase mask are described. A sidelobe suppression level as high as 20dB in the lower wavelength region has been successfully achieved. The schemes allow the writing of truly apodised fibre Bragg gratings using low cost and simple apparatus.
Pseudo-Hamiltonian-connected graphs
(2000-03-30)
Chang, GJ
;
Zhu, XD
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應用數學系
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Department of Applied Mathematics
Given a graph G and a positive integer k, denote by G[k] the graph obtained from G by replacing each vertex of G with an independent set of size k. A graph G is called pseudo-k Hamiltonian-connected if G[k] is Hamiltonian-connected, i.e., every two distinct vertices of G[k] are connected by a Hamiltonian path. A graph G is called pseudo Hamiltonian-connected if it is pseudo-k Hamiltonian-connected for some positive integer k. This paper proves that a graph G is pseudo-Hamiltonian-connected if and only if for every non-empty proper subset X of V(G), N(X) > X. The proof of the characterization also provides a polynomial-time algorithm that decides whether or not a given graph is pseudo-Hamiltonian-connected. The characterization of pseudo-Hamiltonian-connected graphs also answers a question of Richard Nowakowski, which motivated this paper. (C) 2000 Elsevier Science B.V. All rights reserved.
Beam-switchable scanning leaky-wave antenna
(2000-03-30)
Wang, CJ
;
Shih, YC
;
Jou, CF
;
傳播研究所
;
Institute of Communication Studies
A beam-switchable scanning leaky-wave antenna (LWA) has been developed. This LWA with a two-terminal feeding microstrip, line structure is integrated with a single port double throw (SPDT) snitch as a control circuit. In dual-beam mode, the scanning angle is steered over a range of 36-64 degrees for the right-hand beam and 144 -116 degrees for the left-hand beam. In one-beam made, the scanning angle is measured over 20 degrees for the right-hand beam. The measured result shows that we can change from the, one-beam mode to the dual-beam mode electronically by controlling the on/off status of an SPDT switch, in contrast to the case For traditional leaky wave antennas.
iGSM: VolP service for mobile networks
(2000-04-01)
Rao, HCH
;
Lin, YB
;
Cho, SL
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資訊工程學系
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Department of Computer Science
This article proposes iGSM: a voice-over-IF value-added service for mobile network. The iGSM service provides user mobility to subscribers, which allows them to use either GSM handsets or H.323 terminals (IP phones or PCs) to access telecommunications services. We describe how the iGSM registration, deregistration, and call delivery procedures can be implemented without modifying the GSM network. We study how the tromboning effect in the standard GSM system can be avoided when accessing the IP network. Then we investigate the misrouting problem caused by user mobility.
Crystallization kinetics of poly(trimethylene terephthalate)
(2000-04-01)
Huang, JM
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
The isothermal crystallization kinetics of poly(trimethylene terephthalate) (PTT) have been investigated using differential scanning calorimetry (DSC) and polarized light microscopy (PLM). Enthalpy data of exotherm from isothermal crystallization were analyzed using the Avrami theory. The average value of the Avrami exponent, n, is about 2.8. From the melt, PTT crystallizes according to a spherulite morphology. The spherulite growth rate and the overall crystallization rate depend on crystallization temperature. The increase in the spherulitic radius was examined by polarized light microscopy. Using values of transport parameters common to many polymers (U* = 1500 cal/mol, T-infinity = T-g - 30 degrees C) together with experimentally determined values of T-m(0) (248 degrees C) and T-g (44 degrees C), the nucleation parameter, k(g), for PTT was determined. On the basis of secondary nucleation analyses, a transition between regimes III and II was found in the vicinity of 194 degrees C (Delta T congruent to 54 K). The ratio of k(g) of these two regimes is 2.1, which is very close to 2.0 as predicted by the Lauritzen-Hoffman theory. The lateral surface-free energy, sigma = 10.89 erg/cm(2) and the fold surface-free energy, sigma(e) = 56.64 erg/cm(2) were determined. The latter leads to a work of chain-folding, q = 4.80 kcal/mol folds, which is comparable to PET and PET previously reported. (C) 2000 John Wiley & Sons, Inc.
Electrostatic dissipation and flexibility of poly(oxyalkylene)amine segmented epoxy derivatives
(2000-04-01)
Lin, JJ
;
Tseng, FP
;
Chang, FC
;
應用化學系
;
Department of Applied Chemistry
A family of hydrophilic and flexible epoxy polymers was prepared from the reaction of poly(oxyalkylene)amines and diglycidyl ether of bisphenol-A (DGEBA) at 1:1 molar ratio of N-H to epoxide. The use of a high molecular weight (M-W = 1000-6000) poly(oxyethylene-oxypropylene)amine and a low M-W amine as curing agents provided epoxy materials with good properties in toughness and hydrophilicity. The hydrophilicity, probed by surface resistivity of these cured materials, was found to be affected by the nature and weight content of poly(oxyethylene) segment in the polymer backbone, and also by the degree of crystallinity. Specifically, in the presence of a water-soluble poly(oxyethylene-oxypropylene)diamine of M-W 2000 the cured epoxies can reach surface resistivity as low as 10(8.6-9.6) Omega/square. In comparison, the water-insoluble poly(oxypropylene) diamine of M-W 2000 afforded a higher surface resistivity of 10(10.5) Omega/square because of the difference in hydrophilicity between oxyethylene and oxypropylene functionalities. Poly(oxypropylene)diamine of M-W 230 as the sole curing agent generated an epoxy with even higher surface resistivity of 10(13) Omega/square due to a highly crosslinking structure. With proper selection of mixed poly(oxyethylene-oxypropylene)diamine (25 wt%) and 2-aminoethanol (9 wt%), the DGEBA cured polymer had an appropriate surface resistivity of 10(9.8) Omega/square for antistatics. Moreover, this material was extremely ductile in appearance and showed over 500% elongation at break during mechanical tests. The high flexibility is rationalized by the balanced chemical structure of poly(oxyalkylene) segments and bisphenol-A distributed in a slightly crosslinked system. (C) 2000 Society of Chemical Industry.
Design on the low-leakage diode string for using in the power-rail ESD clamp circuits in a 0.35-mu m silicide CMOS process
(2000-04-01)
Ker, MD
;
Lo, WY
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
A new design on the diode string with very tow leakage current is proposed for using in the ESD clamp circuits across the power rails. By adding an NMOS-controlled lateral SCR (NCLSCR) device into the stacked diode string, the Leakage current of this new diode string with six stacked diodes at 5-V (3.3-V) forward bias can be reduced to only 2.1 (1.07) nA at a temperature of 125 degrees C in a 0.35-mu m silicide CMOS process, whereas the previous designs have a leakage current in the order of mA, The total blocking voltage of this new design with NCLSCR can be linearly adjusted by changing the number of the stacked diodes in the diode string without causing latch-up danger across the power rails. From the experimental results, the human-body-model ESD level of the ESD clamp circuit with the proposed low-leakage diode string is greater than 8 kV in a 0.35-mu m silicide CMOS process by using neither the ESD-implantation nor the silicide-blocking process modifications.
Resin transfer molding (RTM) process of a high performance epoxy resin. I: Kinetic studies of cure reaction
(2000-04-01)
Lee, CL
;
Ho, JC
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The cure kinetics of a high performance PR500 epoxy resin in the temperature range of 160-197 degrees C for the resin transfer molding (RTM) process have been investigated. The thermal analysis of the curing kinetics of PR500 resin was carried out by differential scanning calorimetry (DSC), with the ultimate heat of reaction measured in the dynamic mode and the rate of cure reaction and the degree of cure being determined under isothermal conditions. A modified Kamal's kinetic model was adapted to describe the autocatalytic and diffusion-controlled curing behavior of the resin. A reasonable agreement between the experimental data and the kinetic model has been obtained over the whole processing temperature range, including the mold filling and the final curing stages of the RTM process.
W ohmic contact for highly doped n-type GaN films
(2000-04-01)
Lin, CF
;
Cheng, HC
;
Chi, GC
;
電子工程學系及電子研究所
;
奈米中心
Ohmic contacts with low resistance and low barrier height were fabricated on n-type GaN films using W metallization. The n-type GaN films were grown by low pressure metalorganic chemical vapor deposition (LPMOCVD) with Si as the dopant. Ohmic characteristics were studied for GaN films with Si carrier concentration varying from 1.4 x 10(17) to 1.8 x 10(19) cm(-3). The specific contact resistivity were reduced with increasing Si-doping concentration on as-deposited W/GaN films, and the lowest value was 3.6 x 10(-4) Ohm cm(2) on n-type GaN with a concentration of 1.8 x 10(19) cm(-3). After rapid thermal annealing (RTA) treatment on W/GaN films at 1000 degrees C for 30 s, the specific contact resistivity were reduced to 1 x 10(-4) Ohm cm(2). The W metal on n-type GaN films, show that good thermal stability varied the annealing temperatures. The barrier height of as-deposited W metal on GaN is calculated to be 0.058 eV. (C) 2000 Elsevier Science Ltd. All rights reserved.
Emission current influence of gated structure and diamond emitter morphologies in triode-type field emission arrays
(2000-04-01)
Chen, CF
;
Hsieh, HC
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Field emission display is evolving as a promising technique for the future generation of flat panel displays. Characteristics affecting the power of field emitter arrays include the shape and work function of emission materials, distance between tip and gate, and the environmental vacuum condition. In this work, we present a novel scheme that involves a new fabrication process of gate structure metal-insulator-semiconductor (MIS) diode using IC technology. Deposition of the diamond film in this MIS diode forms a column-like diamond with gated field emission arrays (FEAs). This process is completed using a bias-assisted microwave plasma chemical vapor deposition system. Our results indicate that the threshold voltage of column-like diamond FEAs is about 10 V, and the field emission current density is about 139 mA cm(-2) (at V-gc = 20 V). The diamond field emitter array devices with the new gate structure and tip morphology significantly influence the electron field emission characteristics. (C) 2000 Elsevier Science S.A. All rights reserved.