Browsing by Author "Lin, Yu-Chung"

Now showing 1 - 8 of 8

A computer method based on simulated annealing to identify aquifer parameters using pumping-test data
(2008-02-25)
Huang, Yen-Chen
;
Yeh, Hund-Der
;
Lin, Yu-Chung
;
環境工程研究所
;
Institute of Environmental Engineering
Conventional graphical or computer methods for identifying aquifer parameters have their own inevitable limitations. This paper proposes a computer method based on a drawdown model and a heuristic approach of simulated annealing (SA) to determine the best-fit aquifer parameters of the confined and unconfined aquifer systems. The drawdown model for the confined aquifer is the Theis solution and the unconfined aquifer is the Neuman solution. The estimated results of proposed method have better accuracy than those of the graphical methods and agree well with those of the computer methods based on the extended Kalman filter and Newton's method. Finally, the sensitivity analyses for the control parameters of SA indicate that the proposed method is very robust and stable in parameter identification procedures. Copyright (c) 2007 John Wiley & Sons, Ltd.
Groundwater contaminant source identification by a hybrid heuristic approach
(2007-09-29)
Yeh, Hund-Der
;
Chang, Tung-Hua
;
Lin, Yu-Chung
;
環境工程研究所
;
Institute of Environmental Engineering
This study proposes an approach, SATS-GWT, that combines simulated annealing (SA), tabu search (TS), and the three-dimensional groundwater flow and solute transport model (MODFLOW-GWT). Our approach is used to estimate the source information: source location, release concentration, and release period. The sampling concentrations at monitoring points are simulated by the MODFLOW-GWT with an assumed release concentration and release period at a known source location. In the source estimation process, the source location is selected by TS within the suspected source area, and the trials for release concentrations and release periods are generated by SA. The MODFLOW-GWT is employed to compute the simulated concentrations at the monitoring points with the trial solution. The above mentioned procedures are repeated until the stopping criterion regarding the differences of objective function value (OFV) is met. The last trial source information which yields the best OFV is the final solution. Six studies on the homogeneous site, two studies on the heterogeneous site, and one study on the transient flow problem are conducted in this study. A suggestion regarding the optimal number of monitoring points and the condition for estimating the source information is given on the basis of the studies for homogeneous and heterogeneous aquifers. All results indicate that the proposed SATS-GWT can give good estimations, even when the sampling concentrations contain measurement errors.
Hybrid laser-beam-shaping system for rotatable dual beams with long depth of focus
(2016-10-01)
Chou, Fu-Lung
;
Chen, Cheng-Huan
;
Lin, Yu-Chung
;
Lin, Mao-Chi
;
光電工程學系
A laser processing system consisting of two diffractive elements and one refractive element is proposed enabling a Gaussian laser beam to be transformed into two beams with a depth of focus of up to 150 mu m and focal spot smaller than 5 mu m. For specific laser processing, the two beams are rotatable when the beam-splitting diffractive element is rotated. The overall system is versatile for laser cutting and drilling.
Hybrid laser-beam-shaping system for rotatable dual beams with long depth of focus
(2016-10)
Chou, Fu-Lung
;
Chen, Cheng-Huan
;
Lin, Yu-Chung
;
Lin, Mao-Chi
;
光電工程學系
A laser processing system consisting of two diffractive elements and one refractive element is proposed enabling a Gaussian laser beam to be transformed into two beams with a depth of focus of up to 150 mu m and focal spot smaller than 5 mu m. For specific laser processing, the two beams are rotatable when the beam-splitting diffractive element is rotated. The overall system is versatile for laser cutting and drilling.
Identifying groundwater pumping source information using simulated annealing
(2008-07-30)
Lin, Yu-Chung
;
Yeh, Hund-Der
;
環境工程研究所
;
Institute of Environmental Engineering
This study develops an approach referred to as SA-MF using simulated annealing (SA) and a three-dimensional groundwater flow model (MODFLOW-2000) to determine the pumping source information, namely the pumping source location, the pumping rate and the pumping period. Eight scenarios, each with various cases for aquifers with homogeneous or heterogeneous conductivities, are used to test the applicability and accuracy of SA-MF in determining the pumping source information. The results show that at least five measured heads should be used to analyse the pumping source identification problem and at least three observation wells are required to effectively determine the pumping source information. The SA-MF gives good estimated results in both synthetic and real problems even if the measured heads contain measurement errors. Copyright (C) 2008 John Wiley & Sons, Ltd.
One-Dimensional Reflective Diffuser for Line Beam Shaper with Microlens Array Homogenizer
(2014-09-01)
Hsiao, Yung-Neng
;
Wu, Hau-Ping
;
Chen, Cheng-Huan
;
Lin, Yu-Chung
;
Lee, Min-Kai
A laser beam shaping architecture based on a microlens array homogenizer has been exploited, in which the interference effect due to the coherency of the laser source deteriorates the uniformity. Moving diffusers have been considered as an effective way of averaging out the interference pattern. Because the uniformity is required in the line direction only, a one-dimensional reflective-type diffuser with a well-controlled diffusion angle has been proposed and prototyped. The diffuser is attached onto a rotating cylinder for movement in operation. The experiment demonstrates the effectiveness of the scheme, and a line beam with a uniformity of up to 92% has been achieved. (C) 2014 The Japan Society of Applied Physics
Parameter identification for leaky aquifers using global optimization methods
(2007-03-30)
Yeh, Hund-Der
;
Lin, Yu-Chung
;
Huang, Yen-Chen
;
環境工程研究所
;
Institute of Environmental Engineering
In the past, graphical or computer methods were usually employed to determine the aquifer parameters of the observed data obtained from field pumping tests. Since we employed the computer methods to determine the aquifer parameters, an analytical aquifer model was required to estimate the predicted drawdown. Following this, the gradient-type approach was used to solve the nonlinear least-squares equations to obtain the aquifer parameters. This paper proposes a novel approach based on a drawdown model and a global optimization method of simulated annealing (SA) or a genetic algorithm (GA) to determine the best-fit aquifer parameters for leaky aquifer systems. The aquifer parameters obtained from SA and the GA almost agree with those obtained from the extended Kalman filter and gradient-type method. Moreover, all results indicate that the SA and GA are robust and yield consistent results when dealing with the parameter identification problems. Copyright (c) 2006 John Wiley & Sons, Ltd.
Pipe network system analysis using simulated annealing
(2008-08-01)
Yeh, Hund-Der
;
Lin, Yu-Chung
;
環境工程研究所
;
Institute of Environmental Engineering
Water pipe network systems are designed and operated to supply fresh water from the source ( or treatment facility) to the customers. Based on the energy conservation or mass balance principle, a nonlinear equation set can be formulated to describe the relationship between the nodal head and pipe flow rate. In the past, Hardy-Cross method or Newton-type method was commonly used to solve the nonlinear equation set for obtaining the solutions, such as the nodal heads and flow rates. However, these two methods have the drawbacks that a non-convergent and/or a poor result may occur if improper initial guesses for the nodal heads or flow rates are made. In this article, a pipe network solver, PNSA, is developed to solve the nodal head and flow rate for a given network. The nonlinear equation set is first formulated as an unconstrained optimization problem, and then uses simulated annealing to solve the solutions of a pipe network system. The results obtained from PNSA with initial guesses generated by a random number generator show good match with those obtained from modified Powell's hybrid method and sparse matrix method.