Browsing by Issue Date, starting with "2001-03-01"

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Special issues on multimedia communication services
(2001-03-01)
Hang, HM
;
Rao, KR
;
電信研究中心
;
Center for Telecommunications Research
Characterization of p-type InxGa1-xN grown by metalorganic chemical vapor deposition
(2001-03-01)
Wen, TC
;
Lee, WI
;
Sheu, JK
;
Chi, GC
;
友訊交大聯合研發中心
This study investigates the electrical and optical characteristics of Mg-doped InxGa1-xN grown by metalorganic chemical vapor deposition. All the Mg-doped InxGa1-xN layers show p-type conduction after thermal annealing. Room temperature (RT) carrier concentration increases exponentially with an In mole fraction increase. The highest hole concentration of bull; Mg-doped InxGa1-xN is 1.65 x 10(19) cm(-3). Also, the RT photoluminescence (PL) spectra of Mg related emissions in InxGa1-xN are displayed. However, the PL peak intensity becomes weak after the post-annealing process on Mg-doped InxGa1-xN. This degradation might be created by the surface dissociation during the post-annealing process. (C) 2001 Elsevier Science Ltd. All rights reserved.
Hydrogen bonding and mechanical properties in segmented montmorillonite/polyurethane nanocomposites of different hard segment ratios
(2001-03-01)
Tien, YI
;
Wei, KH
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Hydrogen bonding in the hard segments of the synthesized montmorillonite/polyurethane nanocomposites of various hard segment ratios was found to decrease with the increasing amount of montmorillonite regardless of the hard segment ratios, but reached plateau values at 5 wt% montmorillonite concentration. The maximal reductions of the hydrogen bonding in the polyurethane nanocomposites ranged from 20 to 37%, depending on the hard segment ratios as compared to that in the pure polyurethane. The maximal strength and the elongation at break of the polyurethane nanocomposites increased dramatically as compared to that of pristine polyurethane, and the maximal values occurred at 1 wt% montmorillonite concentration. (C) 2001 Elsevier Science Ltd. All rights reserved.
Phase transformations in an Fe-8Al-30Mn-1.5Si-1.5C alloy
(2001-03-01)
Lee, JW
;
Liu, TF
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The phase transformations in an Fe-8Al-30Mn-1.5Si-1.5C alloy has been investigated by means of transmission electron microscopy. In the as-quenched condition, the microstructure of the alloy was austenite phase containing fine (Fe,Mn)(3)AlC carbides. The fine (Fe,Mn)(3) AlC carbides were formed during quenching by a spinodal decomposition. When the as-quenched alloy was aged at temperatures ranging from 550 to 1000 degreesC, the phase transformation sequence as the aging temperature increased was found to be (Fe,Mn)(3)AlC carbide + D0(3) --> (Fe, Mn)(3)AlC carbide + B2 --> (Fe, Mn)(3)AlC carbide + alpha --> gamma. This transformation has never before been observed in the Fe-Al-Mn-C and Fe-Al-Mn-Si-C alloys. (C) 2001 Elsevier Science B.V. All rights reserved.
請問東阿王曹子建先生-曹家豆子店外史
(2001-03-01)
管管
Variable structure control scheme for landing on a celestial object
(2001-03-01)
Liaw, DC
;
Cheng, CC
;
電控工程研究所
;
Institute of Electrical and Control Engineering
This paper considers the landing of a space vehicle on a celestial object. By assuming the air drag in two specific forms and th uncertainty in matching type, their effects are studied. Through the construction of a time-varying boundary layer, a new guidance control law for landing on a celestial object is proposed via the variable structure control (VSC) technique to guarantee that tracking performance is achieved at an exponential convergence rate. The proposed guidance law is continuous and alleviates chattering drawback by classic VSC design. Finally, simulation results are presented to illustrate the use of the main design.
Fabrication and characterization of phosphorus-doped diamond field emitters in triode-type field emission arrays
(2001-03-01)
Chen, CF
;
Tsai, CL
;
Lin, CL
;
材料科學與工程學系
;
Department of Materials Science and Engineering
In this work, we present a novel scheme that involves a new fabrication process for gate-structured metal-insulator-semiconductor (MIS) diodes using IC technology. Using a bias-assisted microwave-plasma chemical vapor deposition (BAMPCVD) system to synthesize P-doped emitters completes this process. A comparison of the held emission characteristics of two types of non-doped dendrite-like and P-doped nanotube-like diamond emitters with a 4-mum gate aperture is made. Phosphorus doping can enhance the electrical characteristics by reducing the turn-on voltage and enhancing the emission current density. The turn-on voltage of non-doped and P-doped emitters is 15 and 5 V, respectively. Phosphorus doping can enhance the electrical properties by increasing the emission current, since the field emission current (I-a) of non-doped and P-doped emitters is 4 muA (at V-gc = 45 V) and 322 muA (at V-gc = 120 V), respectively. The emission current of P-doped emitters is approximately 80-fold larger than that of non-doped diamond emitters. (C) 2001 Elsevier Science B.V. All rights reserved.
Effect of gravity on particle collection efficiency of inertial impactors
(2001-03-01)
Huang, CH
;
Tsai, CJ
;
環境工程研究所
;
Institute of Environmental Engineering
This study has investigated the effect of gravitational force on particle collection efficiency in inertial impactors numerically and experimentally. In the numerical study, two-dimensional flow field in the inertial impactor was simulated by solving the Navier-Stokes equations with the control volume method. Particle trajectories were then calculated to obtain the collection efficiency at different Reynolds numbers, which are based on nozzle diameter. This study shows that gravitational force increases the particle collection efficiency when the Reynolds number is below about 1500. The numerical results were found to be in good agreement with the experimental data of Marple et al. (JAPCA, 37, 1303) (1987), Rubow et al. (American Industrial Hygiene Association Journal, 48, 532) (1987) and those obtained in the present study. (C) 2001 Elsevier Science Ltd. All rights reserved.
Tracking control of unicycle-modeled mobile robots using a saturation feedback controller
(2001-03-01)
Lee, TC
;
Song, KT
;
Lee, CH
;
Teng, CC
;
電機資訊學士班
The tracking control problem with saturation constraint for a class of unicycle-modeled mobile robots is formulated and solved using the backstepping technique and the idea from the LaSalle's invariance principle. A global result is presented in which several constraints on the linear and the angular velocities of the mobile robot from recent literature are dropped. The proposed controller can simultaneously solve both the tracking and regulation problems of a unicycle-modeled mobile robot. With the proposed control laws, the robot can globally follow any path specified by a straight line, a circle or a path approaching the origin using a single controller. As demonstrated, the circular and parallel parking control problem are solved using the proposed controller. Computer simulations are presented which confirm the effectiveness of the proposed tracking control law Practical experimental results validate the simulations.
Sol-gel synthesis and the effect of boron addition on the phosphorescent properties of SrAl2O4 : Eu2+,Dy3+ phosphors
(2001-03-01)
Chen, IC
;
Chen, TM
;
應用化學系
;
Department of Applied Chemistry
The effects of boron addition on the microstructure and afterglow properties of the long-phosphorescent SrAl2O4:Eu2+,Dy3+ (SAED), synthesized via a novel sol-gel route, were systematically investigated. Significant improvement on luminescence intensity and the lengthening of afterglow persistent time in boron-added SAED (BSAED) phases were observed, as compared to those without boron addition and commercial phosphors. Typical bluish-green emissions attributed to the doublet phosphorescence with wavelengths peaking at 412 and 501 nm for BSAED phase and 398 and 486 nm for the pristine SAED phase were observed. Afterglow with wavelengths peaking at 403 and 485 nm was observed for BSAED phase, whereas that with wavelengths peaking at 486.5 nm was found for the pristine SAED phase, as indicated by time-dependent afterglow decay profiles. Results from scanning electron microscopic morphological studies were used to investigate the modification of microstructure of the BSAED phases.
Detecting line segments in an image - a new implementation for Hough Transform
(2001-03-01)
Ching, YT
;
資訊工程學系
;
Department of Computer Science
The conventional Hough Transform is a technique for detecting line segments in an image. The conventional Hough Transform transforms image points into lines in the parameter space. If there are collinear image points, the lines transformed from the points intersect at a point in the parameter space. Determining the intersection is generally carried out through the "voting method", which partitions the parameter space into squared meshes. A problem with the voting method involves determining the resolution required for partitioning the parameter space. Tn this payer. we present a solution to this problem. We propose to transform an image point into a belt, whose width is a function of the width of a line in the image. We then determine the intersection of numerous belts to detect a line segment. An iterated algorithm based the transformation for detecting line segments is presented in this paper. (C) 2001 Elsevier Science B.V. All rights reserved.
Multilevel recording in erasable phase-change media by light intensity modulation
(2001-03-01)
Shieh, HPD
;
Chen, YL
;
Wu, CH
;
光電工程學系
;
Department of Photonics
Multilevel recording has an advantage of increasing the recording density without extensively altering the current optical configuration. Four-level recording schemes in phase-change disks using either two or three recording layers were demonstrated. By modulating the intensity of the laser pulse, marks were recorded in any of the recording layers, forming four recording regions. Utilizing the large difference in refractive indices between the amorphous and crystalline states, each recording region corresponds to a different reflectance. For the four-level recording disk, if each recording region represents two-bit data, then the recording density of the four-level disk can be higher by a factor of two than that of a conventional disk recorded by pulse position modulation (PPM).
請問東阿王曹子建先生-曹家豆子店外史
(2001-03-01)
管管
New media and market competition: A niche analysis of television news, electronic news, and newspaper news in Taiwan
(2001-03-01)
Li, SCS
;
傳播研究所
;
Institute of Communication Studies
With the rapid development of communication technologies, Taiwan's news market has undergone a great transformation. Adopting niche theory from organizational ecology, this study analyzed competition among three news media in Taiwan. A telephone survey was conducted to examine the level of perceived gratification provided by television news, electronic news, and newspaper news. The findings showed that strong competition exists between newspapers and television news, and that television news has gained superiority over newspapers.
A new index of component importance
(2001-03-01)
Hwang, FK
;
應用數學系
;
Department of Applied Mathematics
Several indices of component importance have been proposed in the literature. The index most relevant to system reliability is the Birnbaum importance, but a comparison between two components is hard to prove and even hard to verify by computation. In this paper we propose a new index which is stronger than the Birnbaum comparison, but always verifiable by computing. In many cases, it could even be easier to prove. We also show the relation of this index with other indices. (C) 2001 Published by Elsevier Science B.V.
Fluctuating characteristics and rotation induced stabilization of thermal buoyancy driven water flow in a vertical rotating cylinder
(2001-03-01)
Yin, CP
;
Ker, YT
;
Huang, TH
;
Lin, TF
;
機械工程學系
An experimental study was carried out here to investigate the fluctuating characteristics and stabilization of the thermal buoyancy driven unstable water flow in vertical closed circular cylinders heated from below by rotating the cylinder about its vertical axis. Results for the time variations of the water temperature at selected locations were obtained for the imposed temperature difference DeltaT ranging from 5 degreesC to 15 degreesC and the cavity rotation rate Ohm from 0 to 300 rpm for a cylinder with diameter D = 5 cm, height H = 10 cm and Ohm varying from 0 to 210 rpm for another cylinder with D = 2.5 cm and H = 5 cm. Based on the data for the time records of the water temperature, the flow suppression by the cylinder rotation causes the time-average temperature distributions along the cylinder axis for high rotation rates to become linear. Besides, the flow can be stabilized by the cylinder rotation when the rotation rate is in certain ranges. Significant dependence of the oscillation amplitude with the space is revealed. But the entire how oscillates at nearly the same frequency when the flow is time periodic. Moreover, non-monotonic variations of the oscillation frequency with the rotation rate are clearly shown. Based on the present data, a flow regime map and correlations delineating the stable and unstable states in the vertical rotating cylinders containing water are also provided. (C) 2001 Elsevier Science Ltd. All rights reserved.
Design of sampled-data systems with large plant uncertainty using quantitative feedback theory
(2001-03-01)
Lin, TC
;
Wang, CH
;
Teng, CC
;
Lee, TT
;
電控工程研究所
This paper proposes a new quantitative feedback theory (QFT) design framework for dealing,with sampled-data systems with large plant uncertainty. After the QFT-based design in the continuous-time domain is completed, the analogue controller can he transformed directly into a rational discrete-time transfer function via approximate Z transform with the sampling time as a free parameter. The sampling time can therefore be adjusted to make the uncertain sampled-data system robustly stable. In comparison with other approaches, our approach is much more systematic without the solvability problem and yet significant enough to guide the designer to realize the physical controller in which the plant transfer function has prescribed bounds on its parameters. Several examples are used to illustrate the proposed approach and excellent results are obtained.
請問東阿王曹子建先生-曹家豆子店外史
(2001-03-01)
管管
Using knowledge-based systems for research on parallelizing compilers
(2001-03-01)
Yang, CT
;
Tseng, SS
;
Fann, YW
;
Tsai, TK
;
Hsieh, MH
The main function of parallelizing compilers is to analyze sequential programs, in particular the loop structure, to detect hidden parallelism and automatically restructure sequential programs into parallel subtasks that are executed on a multiprocessor. This article describes the design and implementation of an efficient parallelizing compiler to parallelize loops and achieve high speedup rates on multiprocessor systems. It is well known that the execution efficiency of a loop can be enhanced if the loop is executed in parallel or partially parallel, such as in a DOALL or DOACROSS loop. This article also reviews a practical parallel loop detector (PPD) that is implemented in our PFPC on finding the parallelism in loops. The PPD can extract the potential DOALL and DOACROSS loops in a program by verifying array subscripts. In addition, a new model by using knowledge-based approach is proposed to exploit more loop parallelisms in this paper. The knowledge-based approach integrates existing loop transformations and loop scheduling algorithms to make good use of their ability to extract loop parallelisms. Two rule-based systems, called the KPLT and IPLS, are then developed using repertory grid analysis and attribute-ordering tables respectively, to construct the knowledge bases. These systems can choose an appropriate transform and loop schedule, and then apply the resulting methods to perform loop parallelization and obtain a high speedup rate. For example, the IPLS system can choose an appropriate loop schedule for running on multiprocessor systems. Finally, a runtime technique based on the inspector/executor scheme is proposed in this article for finding available parallelism on loops. Our inspector can determine the wavefronts of a loop with any complex indirected array-indexing pattern by building a DEF-USE table. The inspector is fully parallel without any synchronization. Experimental results show that the new method can resolve any complex data dependence patterns where no previous research can. One of the ultimate goals is to construct a high-performance and portable FORTRAN parallelizing compiler on shared-memory multiprocessors. We believe that our research may provide more insight into the development of a highperformance parallelizing compiler Copyright (C) 2001 John Wiley & Sons, Ltd.
Statistical process monitoring using an empirical Bayes multivariate process control chart
(2001-03-01)
Feltz, CJ
;
Shiau, JJH
;
統計學研究所
;
Institute of Statistics
In this paper, we describe the theory underlying an empirical Bayesian approach to monitoring two or more process characteristics simultaneously. If the, data is continuous and multivariate in nature, often the multivariate normal distribution can be used to model the process. Then, using Bayesian theory: we develop techniques to implement empirical Bayes process monitoring of the multivariable process. Lastly, an example is given to illustrate the use of our techniques. Copyright (C) 2001 John Wiley & Sons, Ltd.