Browsing by Issue Date, starting with "1997-07-01"

Now showing 1 - 20 of 83665

Multiobjective zone TP reduction analyses for an off-stream reservoir
(1997-07-01)
Kao, JJ
;
Tsai, CH
;
環境工程研究所
;
Institute of Environmental Engineering
Multiobjective linear programming (MOLP) models are developed to evaluate total phosphorus (TP) load reduction strategies for an off-stream reservoir. Cost, water quality, and equity are the three major objectives considered. Watershed-based, subwatershed-based, and equal-transport-path-length-based strategies are the three zone control strategies analyzed and compared. The agricultural nonpoint-source pollution (AGNSP) model is used to simulate the non-point-source pollution loads on the reservoir, A twostep modeling procedure is applied to verify sediment mass balance and water quality of storm runoff. MOLP models are established based on the simulation results for the three control strategies and are solved using the ADBASE package to generate the noninferior solution sets of the models. The subwatershed-based control strategy is observed to be the most cost-effective one based on results obtained for TP concentration between 13 and 20 ppb, With respect to equity, however, the watershed-based control strategy is superior to the others. The proposed multiobjective analyses are intended to improve the comparison and evaluation of nonpoint source pollution control strategies.
Investigations of pool boiling heat transfer of binary refrigerant mixtures
(1997-07-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Pool boiling data for binary mixtures of R-22/R-124 on plain tubes are reported at reduced pressures of 0.1, 0.15, and 0.2. Significant reductions of heat transfer coefficients for mixtures are found as compared to pure refrigerant, and the reduction of heat transfer coefficient is especially pronounced in the vicinity of the pore component. This phenomenon is strongly related to the nonlinear variation of physical properties of liquid viscosity and latent heat of the mixtures. The available empirical and semiempirical correlations developed for mixtures are compared with the present data. In addition, a correlation based on the present R-22/R-124 experimental data is proposed. This correlation not only predicts the deterioration of heat transfer coefficients for the present data with success but also predicts the experimental data from other investigators with reasonably good accuracy.
Optical bypassing using a WDM-Gridconnect patchwork
(1997-07-01)
Jager, HA
;
Kao, MS
;
電信工程研究所
;
Institute of Communications Engineering
In this letter, the properties of transparent wavelength routed transport networks are analyzed which are based on a wavelength-divsion multiplexing (WDM)-Gridconnect patchwork and compared to networks built on a conventional fiber infrastructure. The patchwork represents an example of a partitioned wavelength routed fiber-optic transport network using optical bypassing. The cumulative transit traffic and path length statistics are calculated. Based on these results, recommendations for the transparent network partition size and the number of wavelengths are given.
On a pattern-oriented model for intrusion detection
(1997-07-01)
Shieh, SP
;
Gligor, VD
;
資訊工程學系
;
Department of Computer Science
Operational security problems, which are often the result of access authorization misuse, can lead to intrusion in secure computer systems. We motivate the need for pattern-oriented intrusion detection, and present a model that tracks both data and privilege flows within secure systems to detect context-dependent intrusions caused by operational security problems. The model allows the uniform representation of various types of intrusion patterns, such as those caused by unintended use of foreign programs and input data, imprudent choice of default privileges, and use of weak protection mechanisms. As with all pattern-oriented models, this model cannot be used to detect new, unanticipated intrusion patterns that could be detected by statistical models. For this reason, we expect that this model will complement, not replace, statistical models for intrusion detection.
Quasi-two-dimensional simulation of scour and deposition in alluvial channels
(1997-07-01)
Lee, HY
;
Hsieh, HM
;
Yang, JC
;
Yang, CT
;
土木工程學系
Most existing sediment routing models are one-dimensional models and hence they cannot be used Co simulate lateral channel bed deformations. Conversely, a two-dimensional model is computationally time consuming, and is not suitable for long-term simulation. Using the stream tube concept, a one-dimensional model is extended to a quasi-two-dimensional model in this study. It is capable of simulating lateral variations of channel cross section through the adjustments of stream tube boundaries. The model has an option to treat the suspended load and bed load separately and hence is able to simulate the deposition behavior of the suspended sediment under a nonequilibrium process. The model also provides options to solve either de Saint Venant equation or energy equation and hence can be applied in both steady and unsteady flow conditions. An assessment of this model's performance has been conducted through a comparison to an analytical solution and a set of experimental data, The application of this model to the Keelung River and the Shiemen Reservoir in Taiwan also gave convincing results.
On computing stable Lagrangian subspaces of Hamiltonian matrices and symplectic pencils
(1997-07-01)
Lin, WW
;
Wang, CS
;
應用數學系
;
Department of Applied Mathematics
This paper presents algorithms far computing stable Lagrangian invariant subspaces of a Hamiltonian matrix and a symplectic pencil, respectively, having purely imaginary and unimodular eigenvalues. The problems often arise in solving continuous- or discrete-time H-infinity-optimal control, linear-quadratic control and filtering theory, etc. The main approach of our algorithms is to determine an isotropic Jordan subbasis corresponding to purely imaginary (unimodular) eigenvalues by using the associated Jordan basis of the square of the Hamiltonian matrix (the S + S-1-transformation of. the symplectic pencil). The algorithms preserve structures and are numerically efficient and reliable in that they employ only orthogonal transformations in the continuous case.
Improved flash cell performance by N2O annealing of interpoly oxide
(1997-07-01)
Jong, FC
;
Huang, TY
;
Chao, TS
;
Lin, HC
;
Leu, LY
In this letter, we report the effects of N2O annealing of interpoly oxide on flash cell performance. It is demonstrated that by adding an N2O anneal after interpoly oxide formation, improved cycling endurance is achieved, The program and erase efficiencies are also improved significantly, compared to the control cell without N2O anneal. The cells with N2O anneal show higher cell current (i.e., drain current), which can be ascribed to a lower threshold voltage and higher transconductance, compared to the control cell.
Investigations of pool boiling heat transfer of binary refrigerant mixtures
(1997-07-01)
Chiou, CB
;
Lu, DC
;
Wang, CC
;
機械工程學系
;
Department of Mechanical Engineering
Pool boiling data for binary mixtures of R-22/R-124 on plain tubes are reported at reduced pressures of 0.1, 0.15, and 0.2. Significant reductions of heat transfer coefficients for mixtures are found as compared to pure refrigerant, and the reduction of heat transfer coefficient is especially pronounced in the vicinity of the pore component. This phenomenon is strongly related to the nonlinear variation of physical properties of liquid viscosity and latent heat of the mixtures. The available empirical and semiempirical correlations developed for mixtures are compared with the present data. In addition, a correlation based on the present R-22/R-124 experimental data is proposed. This correlation not only predicts the deterioration of heat transfer coefficients for the present data with success but also predicts the experimental data from other investigators with reasonably good accuracy.
A novel 3.5-GHz microwave counter using an opto-electronic harmonic heterodyne technique
(1997-07-01)
Chang, CS
;
Chiu, HF
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A novel 3.5-GHz microwave counter using an opto-electronic harmonic heterodyne technique has been demonstrated, The system's performance has been discussed and evaluated, and is viewed as good, in comparison with today's microwave-counting systems, It is believed that this novel device has potential for measuring signals above 100 GHz.
An efficient class of weighted trimmed means for linear regression models
(1997-07-01)
Chen, LA
;
統計學研究所
;
Institute of Statistics
We propose and study a class of weighted trimmed means based on the symmetric quantile functions for the location and linear regression models. A robustness comparison with the underlying distribution of a symmetric-type heavy tail is given. The weighted trimmed mean in optimal trimming under symmetric distributions is shown to have an asymptotic variance very close to the Cramer-Rao lower bound. For fixed weight setting, the weighted trimmed mean is still relatively more efficient in terms of asymptotic variance than the trimmed mean based on regression quantiles. From the parametric point of view, the computationally easy weighted trimmed mean is shown to be an efficient alternative to maximum likelihood estimation which is usually computationally difficult for most underlying distributions except the ideal case of normal ones. From the nonparametric point of view, this weighted trimmed mean is shown to be an efficient alternative robust estimator. A methodology for confidence ellipsoids and hypothesis testing based on the weighted trimmed mean is also introduced.
Method of solving a triplet comprising a singlet and a cemented doublet with given primary aberrations
(1997-07-01)
Chen, CH
;
Shiue, SG
;
Lu, MH
;
交大名義發表
;
光電工程學系
A simple algebraic algorithm is proposed as a computational tool for the thin-lens design of a triplet which consists of a singlet and a cemented doublet. The triplet is required to yield specified amounts of lens power, primary spherical aberration, central coma, longitudinal chromatic aberration and secondary spectrum. The three element powers of the triplet are first obtained by solving the simultaneous linear equations of the total lens power, longitudinal chromatic aberration and secondary spectrum. A quadratic equation is obtained by combining the equations of spherical aberration and central coma, and the lens shapes are then obtained by solving this quadratic equation. The solving process is purely algebraic and is therefore easy to calculate and guarantees that all the solutions can be found.
High-performance programmable AC power source with low harmonic distortion using DSP-based repetitive control technique
(1997-07-01)
Tzou, YY
;
Ou, RS
;
Jung, SL
;
Chang, MY
;
交大名義發表
This paper proposes a new control scheme based on a two-layer control structure to improve both the transient and steady-state responses of a closed-loop regulated pulse-width-modulated (PWM) inverter for high-quality sinusoidal ac voltage regulation. The proposed two-layer controller consists of a tracking controller and a repetitive controller. Pole assignment with state feedback has been employed in designing the tracking controller for transient response improvement, and a repetitive control scheme was developed in synthesizing the repetitive controller for steady-state response improvement. Design procedure is given for synthesizing the repetitive controller for PWM inverters to minimize periodic errors induced by rectifier-type nonlinear loads. The proposed control scheme has been realized using a single-chip digital signal processor (DSP) TMS320C14 from Texas Instruments. A 2-kVA PWM inverter has been constructed to verify the proposed control scheme. Total harmonic distortion (THD) below 1.4% for a 60-Hz output voltage under a bridge-rectifier RC load with a current crest factor of 3 has been obtained. Simulation and experimental results show that the DSP-based fully digital-controlled PWM inverter can achieve both good dynamic response and low harmonics distortion.
Normally on reflection-type two-wavelength quantum-well modulator with balanced cavity design
(1997-07-01)
Tsai, CM
;
Lee, CP
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
We have demonstrated a reflection-type two-wavelength modulator with a novel balanced cavity design, Simultaneous operations at wavelengths of around 860 and 896 nm have been achieved. By using such a new cavity design similar operating voltages have been obtained for both wavelengths. Under separate biasing voltages of 14.5 and 11 V on each quantum-well absorbing region, the maximum reflectivity changes were around 50%.
Superfield form of discrete gauge states in (c)over-cap=1 2d supergravity
(1997-07-01)
Chung, TD
;
Lee, JC
;
交大名義發表
;
電子物理學系
;
National Chiao Tung University
A general formula for the discrete states (Neveu-Schwarz sector) in N = 1 2D super-liouville theory is written down in the world-sheet supersymmetric form. We then derive a set of gauge states at the discrete momenta. These discrete gauge states are shown to carry the omega(infinity) charges and serve as the symmetry parameters in the old covariant quantization of the theory.
Comparative role of metal-organic decomposition-derived [100] and [111] in electrical properties of Pb(Zr,Ti)O-3 thin films
(1997-07-01)
Chen, SY
;
Chen, IW
;
材料科學與工程學系
;
Department of Materials Science and Engineering
The effect of composition (phase), texture, microstructure and thickness on electrical properties of Pb(Zr1-zTiz)O-3 (PZT) films have been evaluated. Zr-rich PZT films with [111] texture have a higher remanent polarization and dielectric constant, but a lower coercive field as compared with PZT[100] films. Ti-rich PZT films with [100] texture have a higher dielectric constant, but a lower remanent polarization and coercive field as compared with PZT[111] films. Near the morphotropic phase boundary (MPB) composition, films with a mixed texture of [111] and [100] have a higher dielectric constant than PZT[100] and PZT[111] films even though the values of remanent polarization and coercive field of the mixed textured films are in between those of the other two films. Both remanent and saturation polarization are independent of film thickness, whereas dielectric constant decreases but coercive field increases at very small thickness.
Assembly-part automatic positioning using high-level entities of mating features
(1997-07-01)
Chang, CF
;
Perng, DB
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
We present a new and convenient method for automatically positioning parts in an assembly. High-level entities of mating features and mating relations are used to describe the composed state of parts in an assembly. The characteristics of volume, reference origin, and boundary face of mating features and parts are used to determine automatic part-positioning operations. Using the proposed approach, a hierarchical model of the assembly can be constructed more easily with fewer input data. This approach thus makes computer-aided assembly design systems more user-friendly and greatly reduces the amount of input data required, An example is presented to demonstrate the simplicity and effectiveness of the proposed approach. (C) 1998 Elsevier Science Ltd. All rights reserved.
Optical phase conjugation in a nematic liquid-crystal film modulated by a quasi-static electric field
(1997-07-01)
Chen, SH
;
Shen, YR
;
交大名義發表
;
光電工程學系
;
National Chiao Tung University
A quasi-static field can play an important role in molecular reorientation of the optical nonlinearity in liquid crystals because of the combination of the critical behavior of the sample at the Freedericksz transition and of nonlinear coupling of the optical and quasi-static fields. The nonlinear-optical phenomenon, optical phase conjugation, was observed in an electric-field-biased nematic liquid-crystal film and can be predicted by molecular reorientation calculated with continuum theory. The external field-modulated intensities of the phase-conjugation beams were obtained by both numerical calculation and experimental measurement. At the same time, the rise times of the intensities of phase-conjugation beams were measured for various external fields. (C) 1997 Optical Society of America.
Automatic cel painting in computer-assisted cartoon production using similarity recognition
(1997-07-01)
Chang, CW
;
Lee, SY
;
資訊科學與工程研究所
;
Institute of Computer Science and Engineering
The task of painting each eel of an animated sequence has always been a tedious work using traditional methods. In order to simplify and speed up the process, the development of an automatic eel painting system is desired. This paper presents a method for assisting the production of cartoon animation using computers in order to reduce the production expense and to improve the overall quality. It signals a great improvement in the working environment where 2-D animation Is produced. The basic idea of our automatic eel painting mechanism is to extract both statistical and topological features of regions from input animation drawings, and to search for similar corresponding regions in the previous drawing, If the similarity measures are within the accepted thresholds, the corresponding colour will be inherited. A new integrated labelling algorithm constructing statistical region and topological graph features is proposed. Furthermore, a similarity measure of regions is defined and an algorithm of partial matching of attribute graphs is presented. The experimental result shows the feasibility and practicability of the proposed approach. (C) 1997 by John Wiley & Sons, Ltd.
Method of solving a triplet comprising a singlet and a cemented doublet with given primary aberrations
(1997-07-01)
Chen, CH
;
Shiue, SG
;
Lu, MH
;
光電工程研究所
;
Institute of EO Enginerring
A simple algebraic algorithm is proposed as a computational tool for the thin-lens design of a triplet which consists of a singlet and a cemented doublet. The triplet is required to yield specified amounts of lens power, primary spherical aberration, central coma, longitudinal chromatic aberration and secondary spectrum. The three element powers of the triplet are first obtained by solving the simultaneous linear equations of the total lens power, longitudinal chromatic aberration and secondary spectrum. A quadratic equation is obtained by combining the equations of spherical aberration and central coma, and the lens shapes are then obtained by solving this quadratic equation. The solving process is purely algebraic and is therefore easy to calculate and guarantees that all the solutions can be found.
Reliability analysis of replicated and-or graphs
(1997-07-01)
Liang, DR
;
Jan, RH
;
Tripathi, SK
;
資訊工程學系
;
Department of Computer Science
A computation task running in distributed systems can be represented as a directed graph H(V, E) whose vertices and edges may fail with known probabilities. In this paper, we introduce a reliability measure, called the distributed task reliability, to model the reliability of such computation tasks. The distributed task reliability is defined as the probability that the task can be successfully executed. Due to the and-fork/and-join constraint, the traditional network reliability problem is a special case of the distributed task reliability problem, where the former is known to be NP-hard in general graphs. For two-terminal and-or series-parallel (AOSP) graphs, the distributed task reliability can be computed in polynomial time. We consider a graph H-k((V) over cap, (E) over cap, named a k-replicated and-or series-parallel (RAOSP) graph, which is obtained from an AOSP graph H(V, E) by adding (k - 1) replications to each vertex and adding proper edges between two vertices. It can be shown that the RAOSP graphs are not AOSP graphs; thus, the existing polynomial algorithm does not apply. Previously, only exponential time algorithms as used in general graphs are known for computing the reliability of H-k((V) over cap, (E) over cap. In this paper, we present a linear time algorithm with O(K(V + E)) complexity to evaluate the reliability of the graph H-k((V) over cap, (E) over cap), where K = max{k(2)2(2k), 2(3k)}. (C) 1997 John Wiley & Sons, Inc.