• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.22 no.3
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• pp.312-319
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• 2011

In this paper, a new linearization algorithm for DPD(Digital PreDistorter) is suggested. This new algorithm uses DFP(Davidon-Fletcher-Powell) method. This algorithm is more accurate than that of the existing algorithms, and this method renew the best-fit value in every routine with out setting the initial value of step-size. In modeling power amplifier, the memory polynomial model which can model the memory effect of the power amplifier is used. And the overall structure of linearizer is based on an indirect learning architecture. In order to verify for performance of proposed algorithm, we compared with LMS(Least Mean-Squares), RLS(Recursive Least squares) algorithm.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.4
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• pp.528-538
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• 1985

A R-S-S-R three dimensional mechanism is designed for crank-rocker type through the optimization technique. The nonlinear kinematic equation of the mechanism is formulated by adopting the concept of structural error and precision points. Taking this equation as an objective function, the required mechanism is optimally synthesized by the Fletcher-Davidon-Powell's method of optimization techniques. The structural errors due to the various positions of precision points are compared, and the results from the use of two penalty functions suggested respectively by Fiacco-McCormick and by Powell are also compared on their effectiveness. The mobility of the optimally designed mechanism is checked for the possibility of its motion, and when a mechanism is optimally designed, it is strongly suggested that the mobility must be checked on the designed mechanism.

• Journal of the Korean Data and Information Science Society
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• v.28 no.6
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• pp.1447-1456
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• 2017

Accurate inference of parameters of a stochastic rainfall generation model is essential to improve the applicability of the rainfall generation model which modeled the rainfall process and the structure of rainfall events. In this study, the model parameters of a stochastic rainfall generation model, NSRPM (Neyman-Scott rectangular pulse model), were estimated using DFP (Davidon-Fletcher-Powell), GA (genetic algorithm), Nelder-Mead, and DE (differential evolution) methods. Summer season hourly rainfall data of 20 rainfall observation sites within the Nakdong river basin from 1973 to 2017 were used to estimate parameters and the regional applicability of inference methods were analyzed. Overall results demonstrated that DE and Nelder-Mead methods generate better results than that of DFP and GA methods.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.1
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• pp.67-72
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• 1987

InSb TFT is fabricated by the vacuum evaporation method and I-V characteristics are measured. Employing Davidon Fletcher-Powell algorithm, the device parameters are extracted. The current-voltage relations calculated by extracdted parameters are in good agreement with experimental results. It is found that optimization technique may be more simple and accurate than curve fitting method in device parameters extration.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.37 no.4A
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• pp.250-259
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• 2012

This paper compared and investigated the choice of optimal algorithm affects on the directivity synthesis of linear array in the satisfaction to the design specification of the desired directivity, convergence characteristic, and adaptability. Optimal algorithms use a quasi-Newton method(DFP and BFGS method) for realizing the desired directivity, used a quasi-ideal beam, steering beam, and a multi-beam, chosen as desired directivity. In the numerical result, this paper verified the effectiveness of the quasi-Newton method to the directivity synthesis, and offered a solving approach of occurred problems in the numerical simulation process.

• Proceedings of the KSME Conference
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• 2000.11a
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• pp.492-497
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• 2000

This paper focuses on the weight minimization of radial gate, as an extention of the previous work. Radial gates are commonly used to regulate the flow-rate of general purpose dams, due to its simplicity in manufacture and control. The present study identifies the optimum position of support point for 2 and 3 arm type radial gate, which guarantees the minimum weight satisfying strength constraint condition. These optimum designs are then compared with previously constructed radial gates. The results indicate that the weights of the optimized radial gates reduce by about 20%, compared to those of the conventionally designed radial gates.

• Proceedings of the KIEE Conference
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• 1997.07c
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• pp.911-913
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• 1997

This paper presents a method for optima] placement of series capacitors in order to improve the power system transient stability, using genetic algorithms. For the formulation, this paper considers the objective function which is the energy margin as the difference between transient energy and critical energy. The most important factor in determining an accurate critical energy is the controlling unstable equilibrium point (UEP). This paper proposes the controlling UEP methods, concurrently with the DFP(Davidon-Fletcher-Powell) method, which enables the enhancement of multi-machine analysis. The proposed method is applied to 6-bus, 7-line, 4-machine model system to show its effectiveness in determining the locations to install series capacitors and the it's size to be installed in system, simultaneously.

• Proceedings of the Korea Society for Simulation Conference
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• 2001.10a
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• pp.477-483
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• 2001

Optimum directivity synthesis of ultrasonic transducers in linear array is considered. To realize the desired directivity, a robust and efficient method is proposed which is the direct inversion combined with the iterative DFP (Davidon-Fletcher-Powell) method. A quasi-ideal beam with the beam width and the steering beam angle specified are chosen for the numerical demonstrations. The demonstration is then extended to the case of multi-beams. The proposed combination method shows quick convergence over the single LMS or DFP method at the expense of the system matrix inversion.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.1
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• pp.106-115
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• 1988

A numerical procedure for determining the airfoil shape that maximizes the lift is presented. The structure of the flow field is calculated by iteratively coupling potential flow and boundary analysis using the viscous-inviscid interaction method. The potential flow field is obtained by the vortex panel method and boundary layer flow is analyzed by means of integral approximation method which is capable of handling the laminar, transition and turbulent flow regimes. As the result of this study, it is found that the calculated flow regimes have good agreement with the existing experimented data. Davidon-Fletcher-Powell method and Augmented Lagrange Multiplier method are used for the optimal techniques. NACA 23012, NACA 65-3-21, NACA 64-2-415, NACA 64-2-A215 airfoils are used for determining the optimal airfoil shapes as a basic and compensate airfoils. Optimal design showed that the lift coefficients are increased by 17.4% at M$_{0}$=0.2 and 29% at M$_{0}$=0.3, compared with those of basic airfoil.oil.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.34 no.4
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• pp.1105-1116
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• 2014

A stochastic rainfall model, NSRPM (Neyman-Scott Rectangular Pulse Model), is able to reflect the cluster characteristics of rainfall events which is unable in the RPM (Rectangular Pulse Model). Therefore NSRPM has advantage in the hydrological applications. The NSRPM consists of five model parameters and the parameters are estimated using optimization techniques such as DFP (Davidon-Fletcher-Powell) method and genetic algorithm. However the DFP method is very sensitive in initial values and is easily converge to local minimum. Also genetic algorithm has disadvantage of long computation time. Nelder-Mead method has several advantages of short computation time and no need of a proper initial value. In this study, the applicability of parameter estimation methods was evaluated using rainfall data of 59 national rainfall networks from 1973-2011. Overall results demonstrated that accuracy in parameter estimation is in the order of Nelder-Mead method, genetic algorithm, and DFP method.