Browsing by Author "Chen, JJ"

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A theoretical model for the nongray radiation drying of polyvinylalcohol/water solutions
(2004)
Chen, JJ
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Lin, JD
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機械工程學系
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Department of Mechanical Engineering
A theoretical analysis of heat transfer and moisture variation was performed while a PVA solution was exposed to high-intensity nongray irradiation and/or air flow convection. Effective absorption coefficients were incorporated in the radiative transfer analysis. The influence of various radiation and convection parameters on the transfer of heat and moisture variation in the coated layers on an optically thick substrate was investigated. The effects of radiation and convection parameters on the transfer process were presented in terms of the rate of water content removal, heat transfer, and moisture distribution. Results were compared to those of drying when using convective heat. It is evident that the use of thermal radiation combined with convective heat will help in improving the drying rate. Numerical results show that both the radiative energy absorbed by the solution and the substrate and the distribution of water mass fraction in the solution are closely related to the rate of water removal from the solution during the process.
An automated robot calibration system based on a variable D-H parameter model
(1996)
Young, KY
;
Chen, JJ
;
Wang, CC
;
交大名義發表
;
電控工程研究所
Current robot calibration schemes usually employ calibration models with constant error parameters. Consequently, they are inevitably subject to a certain degree of locality, i.e., the calibrated error parameters (CEPs) will produce the desired accuracy only in certain regions of the robot workspace. This is mainly because of incomplete modeling of errors, resulting in imprecision, and because only a limited amount of measured data are available for identifying CEPs. To deal with the locality phenomenon, CEPs that vary in different regions of the robot workspace may be more appropriate Hence, we propose a variable D-H (Denavit and Hartenberg [2]) parameter model to formulate variations of CEPs. Simulations and experiments that verify the effectiveness of the proposed calibration system are described.
Analysis of drug dissolution data
(1999-04-15)
Lee, JC
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Chen, DT
;
Hung, HN
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Chen, JJ
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統計學研究所
Drug absorption in the human body depends on the dissolution rate of the drug. Suitable dissolution characteristics are important to ensure that the drug will achieve the desired therapeutic effects. To assess the similarity of dissolution rates of several drug lots, we apply a general growth curve model with different covariance structures. The Box-Cox power transformation and the naive log transformation are applied to a function of the dissolution rate. The predictive sample-reuse, or cross-validation, method is employed in selecting an appropriate model with best predictive accuracy. A testing procedure for examining the similarity among the drug lots is also conducted. A partially Bayesian approach is used for the assessment of dissolution equivalence. Copyright (C) 1999 John Wiley & Sons, Ltd.
Analysis of heat and mass transfer in drying processes of polymer solution using high-intensity infrared radiation
(1996)
Chen, JJ
;
Lin, JD
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Automatic flux-weakening control of permanent magnet synchronous motors using a reduced-order controller
(2000-09-01)
Chen, JJ
;
Chin, KP
;
機械工程學系
;
Department of Mechanical Engineering
This study presents a novel means of designing a simple and effective position and velocity controller for permanent magnet synchronous motors (PMSM). In contrast to the conventional two-loop control methods with full-state feedback, the proposed controller does not need current information of the motor for feedback purposes. However, under normal operation the steady-state d-axis current can still be controlled to zero to minimize power dissipation. In addition, implementing a simple overmodulation strategy allows the controller to automatically generate a flux-weakening control to expand the range of operating speed when voltage saturation occurs. In addition to not depending on system parameters used by the controller, the automatically generated demagnetizing current is also optimal in the sense of minimum power dissipation that differs from the maximum output torque design or the constant power design of the general flux-weakening control methods. Simulation and experimental results show that the controller can achieve an effective speed and position control with near-minimum power dissipation, even when voltage saturation occurs.
Developing a Taipei motorcycle driving cycle for emissions and fuel economy
(1998-01-01)
Tzeng, GH
;
Chen, JJ
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運輸與物流管理系註：原交通所+運管所
;
Department of Transportation and Logistics Management
The purposes of this study are to develop a representative driving cycle for motorcycles in metropolitan Taipei and to ascertain the emissions and fuel economy of the cycle. We collected extensive driving cycle data and proposed a methodology to develop a Taipei motorcycle driving cycle (TMDC). The characteristics of TMDC are high average acceleration and deceleration, high acceleration-deceleration changes and low average travel speed. Forty-five motorcycles were tested in a laboratory by using the ECE-40 and TMDC test procedure. The emissions of motorcycles tested by TMDC are higher than ECE, whether they are two-stroke or four-stroke engines. Furthermore, the CO and HC emissions of two-stroke engine motorcycles are higher than four-stroke engine motorcycles, and the NOx emission of two-stroke engine motorcycles are lower than four-stroke engine motorcycles, whether they are tested by TMDC or ECE. The fuel economy of two-stroke engine motorcycles tested by TMDC is lower than ECE, but the fuel economy of four-stroke engine motorcycles tested by TMDC is higher than ECE. A linear regression of TMDC in terms of ECE emissions shows them to be highly correlated, as is fuel economy. (C) 1998 Elsevier Science Ltd. All rights reserved.
Dispersion-compensating optical digital filters for 40-Gb/s metro add-drop applications
(2004-05-01)
Chen, JJ
;
光電工程學系
;
Department of Photonics
Optical digital filters that employ optical delay lines are proposed. Properly locating the zeros in the transfer function is shown to enable interleaver pairs to be designed with the same amplitude responses but opposite phase responses. In metro add-drop applications, the interleaver pair can provide up to 50% of the adding and dropping of the total traffic while simultaneously reducing the insertion loss of the express channel. Both experiments and Monte Carlo simulations demonstrated that the cascaded dispersion of seven pairs of interleavers within the + / - 30-GHz pass-band is less than 1 ps. A total dispersion near zero considerably increases the effective bandwidth and greatly increases the number of cascadable add-drop nodes.
Effects of cache mechanism on wireless data access
(2003-11-01)
Lin, YB
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Lai, WR
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Chen, JJ
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資訊工程學系
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Department of Computer Science
In wireless data transmission, the capacity of wireless links is typically limited. Since many applications exhibit temporal locality for data access, the cache mechanism can be built in a wireless terminal to effectively reduce the data access time. This paper studies the cache performance of the wireless terminal by considering a business-card application. We investigate the least-recently used replacement policy and two strongly consistent data access algorithms called poll-each-read and callback. An analytic model is proposed to derive the effective hit ratio of data access, which is used to validate against simulation experiments. Our study reports how the data access rate and the data update distribution affect the cache performance in a wireless terminal.
Efficient bit allocation under multiple constraints on cumulated rates for delayed video coding
(1997)
Lin, DW
;
Chen, JJ
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
We consider optimal encoding of a sequence of video units under a given set of rate constraints which may arise from finite codec delay, finite channel capacity, and finite codec buffer sizes. A Lagrange-multiplier approach is employed and some useful properties of the optimal Lagrange-multiplier solution are obtained under the assumption that the allowed video data rates are continuous. Based on these properties, we derive two solution algorithms for discrete rate allocation. The algorithms are more efficient than that have been presented to date. The solution is optimal when the distortion-rate relations of the video units are convex and the selectable rates of the video units are uniformly spaced with the same granularity. When these conditions do not hold, the Lagrange-multiplier solution may be suboptimal, but can be improved or optimized by a search about the solution.
Efficient optimal rate-distortion coding of video sequences under multiple rate constraints
(1997)
Lin, DW
;
Chen, JJ
;
交大名義發表
;
電子工程學系及電子研究所
;
National Chiao Tung University
We consider optimal coding of video sequences in the sense of employing an optimal selection of quantization scales under buffer and channel constraints. As a result of the delayed-coding framework, multiple rate constraints emerge, leading to the appearance of multiple Lagrange multipliers in a Lagrangian solution approach. We review the applicable Lagrangian optimization theory developed to-date, and present an efficient new solution algorithm.
Implementation of a variable D-H parameter model for robot calibration using an FCMAC learning algorithm
(1999-04-01)
Young, KY
;
Chen, JJ
;
電控工程研究所
;
Institute of Electrical and Control Engineering
Current robot calibration schemes usually employ calibration models with constant error parameters. Consequently, they are inevitably subject to a certain degree of locality, i.e., the calibrated error parameters (CEPs) will produce the desired accuracy only in certain regions of the robot workspace. To deal with the locality phenomenon, CEPs that vary in different regions of the robot workspace may be more appropriate. Hence, we propose a variable D-H (Denavit and Hartenberg) parameter model to formulate variations of CEPs. An FCMAC (Fuzzy Cerebellar Model Articulation Controller) learning algorithm is used to implement the proposed variable D-K parameter model. Simulations and experiments that verify the effectiveness of the proposed calibration scheme based on the variable D-H parameter model are described.
Integral distance graphs
(1997-08-01)
Chen, JJ
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Chang, GJ
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Huang, KC
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應用數學系
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Department of Applied Mathematics
Suppose D is a subset of all positive integers. The distance graph G(Z, D) with distance set D is the graph with vertex set Z, and two vertices x and y are adjacent if and only if \x - y\ is an element of D. This paper studies the chromatic number chi(Z, D) of G(Z, D). In particular, we prove that chi(Z,D) less than or equal to \D\ + 1 when \D\ is finite. Exact values of chi(G, D) are also determined for some D with \D\ = 3. (C) 1997 John Wiley & Sons, Inc.
Integral distance graphs
(1997-08-01)
Chen, JJ
;
Chang, GJ
;
Huang, KC
;
應用數學系
;
Department of Applied Mathematics
Suppose D is a subset of all positive integers. The distance graph G(Z, D) with distance set D is the graph with vertex set Z, and two vertices x and y are adjacent if and only if x - y is an element of D. This paper studies the chromatic number chi(Z, D) of G(Z, D). In particular, we prove that chi(Z,D) less than or equal to D + 1 when D is finite. Exact values of chi(G, D) are also determined for some D with D = 3. (C) 1997 John Wiley & Sons, Inc.
Minimum copper loss flux-weakening control of surface mounted permanent magnet synchronous motors
(2003-07-01)
Chen, JJ
;
Chin, KP
;
機械工程學系
;
Department of Mechanical Engineering
This study presents a novel current loop design method capable of automatic flux-weakening control with minimum copper loss for surface mounted permanent magnet synchronous motors (SPMSM). The proposed current controller can automatically re-compute the d-axis current command to defer output voltage saturation. Consequently, the motor operations in the flux-weakening region are also contained in the stable operating region. Analysis results indicate that since the output voltage vector in the flux-weakening region produced by this controller is consistently on the boundary of the maximum output voltage vector allowed by the inverter, the corresponding flux-weakening current is the optimal value in the sense of minimum copper loss. This minimum copper loss design differs from the maximum output torque design and the constant power design of the flux-weakening control methods found in the literature. Experimental results further demonstrate the feasibility of the proposed current controller and its ability to maximize the speed range of the motor drive for a given inverter capacity.
Multidirectional asymmetrical microlens array light control film for improved image in reflective color liquid crystal displays
(2002-02-01)
Huang, YP
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Chen, JJ
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Ko, FJ
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Shieh, HPD
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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.
Optimal bit allocation for coding of video signals over ATM networks
(1997-08-01)
Chen, JJ
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Lin, DW
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電子工程學系及電子研究所
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電信研究中心
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Department of Electronics Engineering and Institute of Electronics
We consider optimal encoding of video sequences for ATM networks. Two cases are investigated, In one, the video units are coded independently (e.g., motion JPEG), while in the other, the coding quality of a later picture may depend on that of an earlier picture (e.g., H.26x and MPEGx). The aggregate distortion-rate relationship for the latter case exhibits a tree structure, and its solution commands a higher degree of complexity than the former. For independent coding, we develop an algorithm which employs multiple Lagrange multipliers to find the constrained bit allocation, This algorithm is optimal up to a convex-hull approximation of the distortion-rate relations in the case of CBR (constant bit-rate) transmission, It is suboptimal in the case of VER (variable bit-rate) transmission by the use of a suboptimal transmission rate control mechanism for simplicity. For dependent coding, the Lagrange-multiplier approach becomes rather unwieldy, and a constrained tree search method is used. The solution is optimal for both CBR and VER transmission if the full constrained tree is searched, Simulation results are presented which confirm the superiority in coding quality of the encoding algorithms, We also compare the coded video quality and other characteristics of VER and CBR transmission.
Optimal bit allocation for video coding under multiple constraints
(1996)
Chen, JJ
;
Lin, DW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Optimal coding of video sequence over ATM networks
(1995)
Chen, JJ
;
Lin, DW
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Quasi-threshold graphs
(1996-08-27)
Yan, JH
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Chen, JJ
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Chang, GJ
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應用數學系
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Department of Applied Mathematics
Quasi-threshold graphs are defined recursively by the following rules: (1) K-1 is a quasi-threshold graph, (2) adding a new vertex adjacent to all vertices of a quasi-threshold graph results in a quasi-threshold graph, (3) the disjoint union of two quasi-threshold graphs is a quasi-threshold graph. This paper gives some new equivalent definitions of a quasi-threshold graph. From them, linear time recognition algorithms follow. We also give linear time algorithms for the edge domination problem and the bandwidth problem in this class of graphs.
Simultaneous heat and mass transfer in polymer solutions exposed to intermittent infrared radiation heating
(1998-06-01)
Chen, JJ
;
Lin, JD
;
機械工程學系
;
Department of Mechanical Engineering
A theoretical study is performed that describes heat transfer and moisture variation while a polymer solution is exposed to high-intensity infrared radiation flux and/or an airflow. While the intermittent heating is considered, we investigate the influences of various radiation and convection parameters on the transfer of heat and moisture variation of coated layers on an optically thick substrate. During the tempering stage in the intermittent heating process, the convective mass transfer is included to simulate the ambient air in reality. The effects of radiation and convection parameters on the transfer processes are presented in terms of the rate of water content removal, heat transfer, and moisture distributions. Numerical results show that the rate of water removal from the polymer solution is dominated by both the absorbed radiative heat energy and the distributions of water mass fraction in the polymer solution.