Browsing by Author "Chen, JT"

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A heuristic approach to determine bidirectional flow-path for AGV systems
(1999-06-01)
Liu, FHF
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Chen, JT
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工業工程與管理學系
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Department of Industrial Engineering and Management
The rapid development of intelligent vehicles and free-ranging guide systems has increased the feasibility of practical applications for bidirectional AGV systems. This paper presents a heuristic approach for designing the flow-path layout of bidirectional automated guided vehicles. Assume that the block layout for the departments is predetermined, and that the pick-up/deposit (P/D) stations are located on the boundaries of the departments. Thus, the boundaries of the block layout can be transformed into a planar network where the nodes represent the P/D stations and the intersections of boundaries. The objective is to have a flow-path layout at minimal cost. The fixed cost of aisles and the travel cost of vehicles are considered simultaneously. There are three stages in the proposed heuristic approach: constructing an initial solution, improving the solution, and adjusting the solution. Several sample problems could be solved in less than one second using a pentium-166 PC, with less than 1% difference from the optimal solution on average. By adding some equipment for changing direction, this approach could also be applied to the material handling systems, which traverse on fixed-paths unidirectionally, such as conveyors, power-and-free, unidirectional automated guided vehicles and monorails. Significance: An effective and efficient heuristic approach is proposed for determining a bidirectional flow-path layout. The approach can be used effectively in many different divided-based configurations of AGV systems, such as tandem, segmented bidirectional single-loop (SBSL), segmented flow topology (SFT) and divided configuration.
Analytical framework for designing the divided automated guided Vehicles system
(1997-06-01)
Liu, FHF
;
Chen, JT
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交大名義發表
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工業工程與管理學系
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National Chiao Tung University
The purpose of this paper is to present an analytical design framework for an AGV system configuration, called divided AGV system. In the divided AGV system, the pickup/deposit stations are divided into several transportation cells, and each cell has a simple guidepath traversed by a dedicated vehicle. Several transit stations may be set to construct a transit system for handling the intercell transport requirements. Moreover, the guidepaths for all cells are allowed to intersect at the crossroads. A systematic procedure is proposed to consider two important factors, distance and transport requirements (flow) between pickup/deposit stations simultaneously during the dividing procedure. In addition, a mathematical programming model for locating transit stations is integrated in the analytical framework. The divided configuration would not be seriously affected by plant layout, and the bi-directional vehicles would be implemented more effectively. In brief, the divided configuration could keep the simplicity of a control system and improve system feasibility and competition in a practical manufacturing environment.
Analytical framework for designing the divided automated guided Vehicles system
(1997-06-01)
Liu, FHF
;
Chen, JT
;
工業工程與管理學系
;
Department of Industrial Engineering and Management
The purpose of this paper is to present an analytical design framework for an AGV system configuration, called divided AGV system. In the divided AGV system, the pickup/deposit stations are divided into several transportation cells, and each cell has a simple guidepath traversed by a dedicated vehicle. Several transit stations may be set to construct a transit system for handling the intercell transport requirements. Moreover, the guidepaths for all cells are allowed to intersect at the crossroads. A systematic procedure is proposed to consider two important factors, distance and transport requirements (flow) between pickup/deposit stations simultaneously during the dividing procedure. In addition, a mathematical programming model for locating transit stations is integrated in the analytical framework. The divided configuration would not be seriously affected by plant layout, and the bi-directional vehicles would be implemented more effectively. In brief, the divided configuration could keep the simplicity of a control system and improve system feasibility and competition in a practical manufacturing environment.
Growth of MgWO4 phosphor by RF magnetron sputtering
(1998-05-01)
Chu, JP
;
Hsieh, IJ
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Chen, JT
;
Feng, MS
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材料科學與工程學系
Magnesium tungstate (MgWO4) thin film phosphors prepared by radio frequency (RF) magnetron sputter deposition were characterized. alpha- and beta-MgWO4 were determined as the major phases in the films studied. Since the deposition rates of film were influenced by RF power. working pressure as well as oxygen content, these processing parameters played an important role in affecting the phase present in the as-deposited films. It is found that the formation of alpha-MgWO4 phase was favorable for the films grown at low deposition rates (<40 Angstrom min(-1)) whereas beta-MgWO4 was a dominant phase at high deposition rates. Substrate temperatures showed no detectable effects on the deposition rates and thus the beta-MgWO4 was the only phase present for the substrate temperature range examined. A phase formation mechanism due to the deposition rate difference is described. Post-deposition annealing significantly improved the cathodoluminescence (CL) properties of films, with annealing temperatures at 750 degrees C or above being the most effective. CL property improvement appeared to he attributed to the enhancement of crystallinity and the transformation to the stable beta-MgWO4 phase during the annealing. Annealing-induced film delamination and blisters. however, resulted in deterioration of low voltage CL properties. (C) 1998 Elsevier Science S.A. All lights reserved.
New soluble poly(2,3-diphenylphenylene vinylene) derivatives for light-emitting diodes
(2005-04-22)
Yang, SH
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Chen, JT
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Li, AK
;
Huang, CH
;
Chen, KB
Soluble poly(2,3-diphenylphenylene vinylene) (DP-PPV) derivatives, poly(2,3-diphenyl-5-(4-heptyloxy-4'-oxytrimethylenediphenyl)phenylene vinylene) (P1), poly(2,3-diphenyl-5-[4-(4-pentylcyclohexyl)phenoxyl-propyl-p-phenylene vinylene) (P2) and poly(2,3-diphenyl-5-(2-(1, 4, 5-triphenyl-1H-2-imidazoloyl)-1-oxytrimethylene phenyl) phenylene vinylene) (P3), were synthesized. P1 and P2 contain liquid crystal side groups; while P3 contains a charge transport group. The polymers showed solid state UV-Visible absorption and photoluminescence in the range of 370-380 and 480-510 nm, corresponding to blue green emission. Similar to many other reported systems, the solution fluorescence spectra of P1 and P2 showed slight solvent dependency and blue-shifted with respect to those of the films. These were not the case for P3 which showed little solvent dependency and little blue shift in solution. Two-layer light-emitting devices with a simple ITO/PEDOT/polymer/Ca (Al) configuration were fabricated and characterized. (c) 2004 Elsevier B.V. All rights reserved.
Synthesis and thermal and photoluminescence properties of liquid crystalline polyacetylenes containing 4-alkanyloxyphenyl trans-4-alkylcyclohexanoate side groups
(2002-02-12)
Ting, CH
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Chen, JT
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Hsu, CS
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應用化學系
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Department of Applied Chemistry
Two series of polyacetylenes containing 4-alkanyloxyphenyl trans-4-n-alkylcyclohexanoate were synthesized using [Rh(nbd)Cl](2), MoCl5, and WCl6 as initiators. Polymers 1P-3P, which contain no flexible spacer, show no mesomorphic properties due to the rigid poly(phenylacetylene) backbone, Polymers 4P-9P, which contain three or four methylene units in their spacers, exhibit both SA and S, phases. X-ray diffraction diagrams reveal that the liquid crystalline polyacetylenes display an interdigitated bilayer structure for the smectic phases. Polymers 4P-9P are photoluminescent, and their emission wavelengths are about 500 rim. The photoluminescence intensity increased dramatically when a liquid crystalline polyacetylene was blended with poly(methyl methacrylate).
Synthesis of alkyl-branched main chain copolyimides and their effect on the pretilt angles of liquid crystal alignment
(2002-07-01)
Lee, WC
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Chen, JT
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Hsu, CS
;
Wu, ST
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應用化學系
Three series of copolyimides containing long alkyl branches were synthesized using the two-step method via poly(amic acid) precursors and chemical imidization. Most of the copolyimides prepared are soluble in polar organic solvents. Good liquid crystal alignment was achieved by buffing the copolyimide films spin-coated onto indium tin oxide glass substrates. The measured liquid crystal pretilt angles range from 0.16degrees to 15.54degrees. The Titan simulation program was used to calculate the dipole of each dianhydride structure and correlate with the observed pretilt angles. Main chain copolyimides with a long alkyl side chain, small dipole, and linear, symmetric and rigid core structures are favourable for generating large pretilt angles.