Browsing by Issue Date, starting with "2002-01-15"

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Addenda to photoluminescence and electron paramagnetic resonance studies of defect centers in porous silicon
(2002-01-15)
Lue, HT
;
Tseng, CY
;
Lue, JT
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This work includes addenda to the paper entitled photoluminescence and electron paramagnetic resonance studies of defect centers in porous silicon (PS) which was published in this journal. The readers can readily obtain the principal values of g(parallel to) and g(perpendicular to) from the de-convolution of the effective principal g-values of the spin resonance data measured at various rotating angles of the magnetic field and the crystal axes. (C) 2002 Elsevier Science B.V. All rights reserved.
Low-voltage-operation high-power-density AlGaAs/InGaAs enhancement-mode pseudomorphic high-electron-mobility transistor for personal handy-phone handset application
(2002-01-15)
Chen, SH
;
Chang, L
;
Chang, EY
;
Chang, CY
;
材料科學與工程學系
A high-power-density enhancement-mode AlGaAs/InGaAs pseudomorphic high-electron-mobility transistor (E-PHEMT) is developed for the Japanese personal handy-phone system (PHS). The E-PHEMT has a total gate width of 3.36 mm with a gate length of 0.5 mum. The E-PHEMT shows a high power density of 247 mW/mm at 3.6 V, 196 mW/mm at 3 V, 152 mW/mm at 2.4 V and 63 mW/mm at 1.2 V, this is the highest power density reported so far for E-PHEMT with similar device size and bias conditions. When the E-PHEMT was qualified by 1.9 GHz pi/4-shifted quadrature phase shift keying (QPSK) modulated signal for PHS at 2,4 V with idle current of 30 mA. the device shows a linear PAE of 35.1% with associated power gain of 15.5 dB at output power of 22.4 dBm. The adjacent channel leakage power (P(adj)) of the de ice is -56.6 dBc at 600 kHz apart from the center frequency. The E-PHEMT meets PHS specifications and demonstrates high power density, excellent power efficiency and linearity at low bias voltage.
Domination in distance-hereditary graphs
(2002-01-15)
Chang, MS
;
Wu, SC
;
Chang, GJ
;
Yeh, HG
;
應用數學系
The domination problem and its variants have been extensively studied in the literature. In this paper we investigate the domination problem in distance-hereditary graphs, In particular, we give a linear-time algorithm for the domination problem in distance-hereditary graphs by a labeling approach. We actually solve a more general problem, called the L-domination problem, which also includes the total domination problem as a special case. (C) 2002 Elsevier Science B.V. All rights reserved.
Hot filament for in situ catalyst supply in the chemical vapor deposition growth of carbon nanotubes
(2002-01-15)
Chen, CF
;
Lin, CL
;
Wang, CM
;
材料科學與工程學系
;
Department of Materials Science and Engineering
A simplified chemical vapor deposition (CVD) method is described for in situ synthesis of multiwalled carbon nanotubes. The synthesis apparatus is similar to, that used to deposit CVD diamond. However, an Fe-Cr wire is selected and coiled as the filament to grow nanotubes. The tubes crow because the filament acts as both a heat source for pyrolysis, and a source of metal for the catalyst. The evaporated metal atoms can be considered to catalyze the growth of carbon nanotubes. The system has the potential to inexpensively synthesize large amounts of nanotubes continuously by combining physical and chemical vapor deposition.
Synthesis and characterization of soluble polyimides derived from 2,2 '-bis(3,4-dicarboxyphenoxy)-9,9 '-spirobifluorene dianhydride
(2002-01-15)
Reddy, DS
;
Shu, CF
;
Wu, FI
;
應用化學系
;
Department of Applied Chemistry
The synthesis of aromatic poly(ether imide)s containing spirobifluorene units in the polymer backbone is described. 2,2'-Bis(3,4-dicarboxyphenoxy)-9,9'-spirobifluorene dianhydride, which was used as a new monomer, was synthesized with 2,2'-dihydroxy-9,9'-spirobifluorene as the starting material. In the spiro-segment, the rings of the connected bifluorene were orthogonally arranged. This bis(ether anhydride) monomer was employed in reactions with a variety of aromatic diamines to furnish poly(ether imide)s, involving an initial ring-opening polycondensation and subsequent chemically induced cyclodehydration. Excellent solubility in common organic solvents at room temperature, good optical transparency, and high thermal stability are the prominent characteristic features of these new polymers, which can be attributed to the presence of spiro-fused orthogonal bifluorene segments along the polymer chain. The glass-transition temperatures of the polyimides were 240-293 degreesC, and the 5% weight-loss temperatures were greater than 500 degreesC. (C) 2001 John Wiley & Sons, Inc.
Thermal stability study of Ni/Ta n-GaN Schottky contacts
(2002-01-28)
Chen, GL
;
Chang, FC
;
Shen, KC
;
Ou, J
;
Chen, WH
The Schottky behavior of Ni/Ta and Ni contacts on n-GaN was investigated under various annealing conditions by current-voltage measurements. It is found that with the addition of Ta between the Ni layer and the GaN substrate the thermal stability properties of devices can be significantly improved. Experimental results indicate that a high quality Ni/Ta n-GaN Schottky diode with an ideality factor and barrier height of 1.16 and 1.24 eV, respectively, can be obtained under 1 h annealing, at 700 degreesC. (C) 2002 American Institute of Physics.
A model of non-homogeneous damped electromagnetic wave and heat equation in ferrite materials
(2002-02-01)
Tung, MJ
;
Chen, R
;
Hsu, CH
;
Tseng, TY
;
電子工程學系及電子研究所
This study uses a closely coupled model to treat the core loss of ferrite by the combination of non-homogeneous damped electromagnetic wave and heat equation. The heat dissipation of ferrites is caused by the core loss, which is a summation of magnetic, dielectric and eddy current losses. Explicit finite difference method solves the coupled equations to calculate core loss and compares it with the measured results. Those results show that this method can be used to analyze electromagnetic and thermal field with temperature dependence of ferrites. (C) 2002 Elsevier Science B.V. All rights reserved.
Multidirectional asymmetrical microlens array light control film for improved image in reflective color liquid crystal displays
(2002-02-01)
Huang, YP
;
Chen, JJ
;
Ko, FJ
;
Shieh, HPD
;
光電工程學系
A multidirectional asymmetrical microlens array light control film (MAMA-LCF) which can direct light incident from multiple directions collectively for viewing is demonstrated in achieving much enhanced brightness in reflective color super twisted-nematic liquid crystal displays (STN-LCDs). The MAMA-LCF, constructed with an asymmetrical microlens array and laminated onto the front surface of reflective color STN-LCDs, can yield a maximum gain of about 5 x the MgO standard white in a typical viewing region without visible dispersion, moire or parallax effects.
A new method for extracting primitives of regular textures based on wavelet transform
(2002-02-01)
Lee, KL
;
Chen, LH
;
資訊工程學系
;
Department of Computer Science
In this paper, a new method for extracting primitives of a regular texture via wavelet transform is provided. Each primitive is restricted to be a parallelogram. The main work of the proposed method is to extract the two displacement vectors that form the primitive of a regular texture. A contrast-based criterion is used to select appropriate subimages obtained from wavelet transform for detecting displacement vectors. An edge thresholding method is then performed on the subimages selected to locate edges. Based on these edges, Hough transform is applied to extract the displacement vectors. The proposed method is quite efficient and can get more accurate results for displacement vectors when comparing to traditional co-occurrence matrix based methods. Synthesized textures are provided to show the effectiveness of the proposed method.
Hybrid 10-Gb/s, 2.5-Gb/s, 64-QAM, and AM-VSB high-capacity wavelength-division-multiplexing transport systems using SMF and LEAF fibers
(2002-02-01)
Lee, CC
;
Chen, YK
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Chang, CH
;
Feng, KM
;
Tzeng, SL
A four-wavelength high-capacity hybrid wavelength-division-multiplexing (WDM) system separately over 100-km standard single-mode fiber and nonzero dispersion-shifted fiber of large effective area fiber is demonstrated. The WDM wavelengths contain one 10-Gb/s signal, one 2.5-Gb/s signal, one 64-quadrature amplitude modulator signal of 110 channels, and one amplitude module with vestigial sideband signal of 80 channels. Satisfaction of a huge variety of receiving requirements and reduction of fiber nonlinearities-induced degradations by controlling channel powers are also considered. Such a hybrid WDM system would be attractive for multiservice trunk applications in advanced transport systems for providing both CATV and telecommunication services.
The synthesis of naphthosultine and benzodisultines and their pyrolysis with dienophiles: Studies on o-naphthoquinodimethane and bis-o-quinodimethane
(2002-02-01)
Wu, AT
;
Liu, WD
;
Chung, WS
;
應用化學系
;
Department of Applied Chemistry
Sealed tube reactions of the naphthosultine 8 with a series of electron-deficient dienophiles (fumaronitrile, N-phenylmaleimide, dimethyl fumarate, and dimethyl acetylenedicarboxylate) in toluene at 180 degreesC gave corresponding 1:1 cycloadducts 11-14 in various amounts along with rearranged naphthosulfolene 7 in 67-95% yields. The reaction of 1,2,4,5-tetra(bromomethyl)benzene with Rongalite (sodium formaldehyde sulfoxylate) and tetrabutylammonium bromide in DMF gave benzodisultines 17 and 18 in a combined yield of 56%. Sealed tube reactions of benzodisultines 17 and 18 with a series of dienophiles in xylene at 200 degreesC gave corresponding 1:1 and 1:2 cycloadducts 20-27. The results suggested that thermal extrusion of sulfur dioxide from these sultines led to either o-naphthoquinodimethane 6 (from 8) or bis-o-quinodimethane 19 (from 17 and 18); subsequent trapping of these reactive intermediates by dienophiles and SO2 gave various 1:1 and 1:2 Diels-Alder adducts in modest to excellent yields.
Spatial disorder of Cellular Neural Networks
(2002-02-01)
Hsu, CH
;
Lin, SS
;
應用數學系
;
Department of Applied Mathematics
This paper shows the spatial disorder of one-dimensional Cellular Neural Networks (CNN) using the iteration map method. Under certain parameters, the map is one-dimensional and the spatial entropy of stable stationary solutions can be obtained explicitly as a devil-staircase like function.
Effect of hydrating liquid on the hydraulic properties of geosynthetic clay liners
(2002-02-01)
Shan, HY
;
Lai, YJ
;
土木工程學系
;
Department of Civil Engineering
The engineering properties of geosynthetic clay liners (GCLs) are closely related to the chemistry of pore liquid. For applications in lining systems or cover systems of landfills, covers for remediation sites, and secondary containment systems, GCLs are likely to be permeated by more than one type of liquid. In this study, GCL specimens were hydrated and permeated with different liquids. The hydraulic conductivity of these GCL specimens was determined. The results showed that the hydraulic conductivity of GCLs was controlled by both hydrating and permeating liquid. In addition, even if GCLs were hydrated with aqueous phase liquids other than fresh water, they still have the ability to retard infiltration effectively. (C) 2002 Elsevier Science Ltd. All rights reserved.
Analytical prediction of the cogging torque and torque constant of a hybrid stepping motor
(2002-02-01)
Wang, SJ
;
Lin, SK
;
電控工程研究所
;
Institute of Electrical and Control Engineering
We present an analytic method to efficiently calculate the torque constant and cogging torque of a hybrid stepping motor. The feature of the proposed method is its computational efficiency in that it is a useful tool for the motor design which is aimed at reducing the level of cogging torque or increasing the torque constant. This method is verified by comparing with the 3D finite element method and some experiments. (C) 2002 Elsevier Science B.V. All rights reserved.
Synthesis and characterization of new polyquinolines containing 9,9 '-spirobifluorene units
(2002-02-01)
Chiang, CL
;
Shu, CF
;
應用化學系
;
Department of Applied Chemistry
Polyquinolines, which contain 9,9'-spirobifluorene units in the main chain, were synthesized via the acid-catalyzed Friedlander condensation reactions of bis(o-aminoketone) with bisacetyl monomers. In the spiro-fused bifluorene moiety, the two mutually perpendicular fluorene rings were connected via a common tetracoordinated carbon atom. This structural feature leads to polymers that possess high thermal stability and good solubility in common organic solvents. The polyquinolines have similar lowest energy transitions that can be attributed to a pi-pi* transition with lambda(max) values in the 363-385 nm range and exhibit blue emission. A model compound was synthesized to demonstrate that the tetrahedral bonding carbon at the center of the spiro moiety could serve as a conjugation interrupt to effectively control the conjugation length of the polymers. The electrochemical behaviors of these polymers were investigated by cyclic voltammetry. The reversible reduction and low-lying LUMO energy level suggest that some of the polyquinolines might have potential for use as materials for electron injection and transport in polymer LEDs.
Effect of nitrogen addition to shielding gas on residual stress of stainless steel weldments
(2002-02-01)
Tseng, KH
;
Chou, CP
;
機械工程學系
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Department of Mechanical Engineering
The objective of the present study, was to investigate the effect of nitrogen additions to the shielding gels Oil the ferrite content and residual stress in austenitic stainless steels. Autogenous gas tungsten arc (GTA) welding was applied on austenitic stain less steels 304 and 310 to produce a bead on plate weld, The delta ferrite content of the weld metals was measured using a Ferritscope. The residual stress in the weldments was determined using the hole drilling strain gauge method. The present results indicated that the retained delta ferrite content in type 304 stainless steel weld metals decreased rapid v as nitrogen addition to the argon shielding gas was increased. The welding residual stress increased with increasing quantity, of added nitrogen in the shielding gas. It was also found that the tensile residual stress zone in austenitic stainless steel weldments was exteneded as the quantity of added nitrogen gas in the argon shielding gas was increased. (C) 2002 IoM Commuications Ltd.
Heuristic and simulated annealing algorithms for solving extended cell assignment problem in wireless ATM networks
(2002-02-01)
Din, DR
;
Tseng, SS
;
資訊工程學系
;
Department of Computer Science
In this paper, we investigate the extended cell assignment problem which optimally assigns new adding and splitting cells in Personal Communication Service (PCS) to switches in a wireless Asynchronous Transfer Mode (ATM) network. Given cells in a PCS network and switches on an ATM network (whose locations are fixed and known), we would like to do the assignment in an attempt to minimize a cost criterion. The cost has two components: one is the cost of handoffs that involve two switches, and the other is the cost of cabling. This problem is modeled as a complex integer programming problem, and finding an optimal solution to this problem is NP-hard. A heuristic algorithm and a simulated annealing algorithm are proposed to solve this problem. The heuristic algorithm, Extended Assignment Algorithm (EEA), consists of two phases, initial assigning phase and cell exchanging phase. First, in the initial assigning phase, the initial assignments of cells to switches are found. Then, these assignments are improved by performing cell exchanging phase in which two cells are repeatedly exchanged in different switches with great reduction of the total cost. The simulated annealing algorithm, ESA (enhanced simulated annealing), generates constraint-satisfied configurations, and uses three configuration perturbation schemes to change current configuration to a new one. Experimental results indicate that EAA and ESA algorithms have good performances. Copyright (C) 2002 John Wiley Sons, Ltd.
Characterization and Modeling of on-chip spiral inductors for Si RFICs
(2002-02-01)
Chao, CJ
;
Wong, SC
;
Kao, CH
;
Chen, MJ
;
Leu, LY
The paper presents a complete characterization of on-chip inductors fabricated in BiCMOS technology. First, a study of the scaling effect of inductance on geometry and structure parameters is presented to provide a clear guideline on inductor scaling with suitable quality factors. The substrate noise analysis and noise reduction techniques are then investigated. It is shown that floating well can improve both quality factor and noise elimination by itself under 3 GHz and together with a guard ring above 3 GHz. Finally, for accurate circuit simulations, a new inductor model is developed for predicting the skin effect and eddy effect and associated quality factor and inductance.
Determination of head pose and facial expression from a single perspective view by successive scaled orthographic approximations
(2002-02-01)
Chang, CC
;
Tsai, WH
;
資訊工程學系
;
Department of Computer Science
Human faces are the main organs for expressing human emotion. In this study, anew iterative approach to analyzing the head pose and the facial expression of a human face from a single image is proposed. The proposed approach extends the concept of successive scaled orthographic approximations. which was used to estimate the pose of a rigid object, to develop a method to estimate the parameters for a non-rigid object, namely, a human face. The implementation of the proposed method is simple; furthermore, no initial guess is required. The convergency property of the proposed method is also analyzed theoretically and experimentally. Experimental results show that the proposed method is robust and has a high percentage of convergency, and thus prove the feasibility of the proposed approach.
Effect of heat treatments on in-situ Al2O3/TiAl3 composites produced from squeeze casting of TiO2/A356 composites
(2002-02-01)
Hsu, CW
;
Chao, CG
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In-situ Al2O3/TiAl3 intermetallic matrix composites were fabricated via squeeze casting of TiO2/A356 composites heated in the temperature range from 700 degreesC to 780 degreesC for 2 hours. The phase transformation in TiO2/A356 composites employing various heat-treatment temperatures (700 degreesC to 780 degreesC) was studied by means of differential thermal analysis (DTA), microhardness, scanning electron microscopy (SEM), electron probe microanalysis (EPMA), and X-ray diffraction (XRD). From DTA, two exothermic peaks from 600 degreesC to 750 degreesC were found in the TiO2/A356 composites. The XRD showed that Al2O3 and TiAl3 were the primary products after heat treatment of the TiO2/A356 composite. The fabrication of in-situ Al2O3/TiAl3 Composites required 33 vol pet TiO2 in Al and heat treatment in the range from 750 degreesC to 780 degreesC. The hardness (HV) of the in-situ Al2O3/TiAl3 composites (1000 HV) was superior to that of nonreacted TiO2/A356 composites (200 HV). However, the bending strength decreased from 685 MPa for TiO2/A356 composites to 250 MPa for Al2O3/TiAl3 composites. It decreased rapidly because pores occurred during the formation of Al2O3 and TiAl3. The activation energy of the formation of Al2O3 and TiAl3 frorn TiO2 and A356 was determined to be about 286 kJ/mole.