• Proceedings of the KIEE Conference
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• 1991.11a
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• pp.357-360
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• 1991

In this paper, we have introduced a network and showed how this can be realised as an adaptive equalizer. The walsh equlizer is built from a set of Walsh-Block pulse functions and LMS algorithms with the optimal convergence factor(C.F.). The convergence and the adaptation speed of this algorithms depends on the proper choice of a design factor $\mu$ called the C.F.. Conventional adaptation techniques use the fixed time constant C.F. by the method of trial and error. In this paper, we propose to adaptive C.F. which are optimally tailored to adapt C.F. in real time so that their values are kept optimum for a new set of input variables.

• Proceedings of the KIEE Conference
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• 1999.07b
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• pp.924-926
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• 1999

To reduce chattering in sliding mode control, a boundary layer around the sliding surface is used, and a continuous control is applied within the boundary. In this paper, a method of determining the sliding mode controller switching gains and the width of boundary layer is presented. Contrary to the trial and error selection of the switching gains and the width of boundary layer, the selection in the presented work is done using genetic algorithms. Simulation results show that the system performance has been improved.

• Proceedings of the KIEE Conference
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• 1998.07b
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• pp.509-511
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• 1998

Design of fuzzy logic controllers encounters difficulties in the selection of optimized membership function and fuzzy rule base, which is traditionally achieved by tedious trial-and-error process. In this paper We proposed a new method to generate fuzzy logic controllers throught genetic algorithm(GA). The controller design space is coded in base-7 strings chromosomes, where each bit gene matches the 7 discrete fuzzy value. The developed approach is subsequently applied to the design of proportional plus integral type fuzzy controller for a do-servo motor control system. It was presented in discrete fuzzy linguistic value, and used a membership function with Gaussian curve. The performance of this control system is demonstrated higher than that of a conventional PID controller and fuzzy logic controller(FLC).

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2039-2042
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• 2008

Recently, Electronic & Electrical Products have problems how to reduce heat in trend reducing size and increasing speed. heat pipes worked by latent heats can solve problems for effective and quiet electronic applications. Heat Pipes have to be suitably designed for the external conditions due to showing optimum performance. it has influence on efficiency of heat pipes to the exterior structure changed by length, bending angle, diameter. Designing heat pipes has depended on experience from trial and error. this method wasted too many resources, but can't guarantee efficiency. to prevent those wastes, this study aims at making the thermal transfer coefficient predicting efficiency. In this study, the thermal transfer coefficient has been made from experimental results that used variables - lengths between heat source and radiation, bending angles, diameters of heat pipes. variables become non-dimensional in modeling process for making the coefficient.

• Journal of the Korean Society of Hazard Mitigation
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• v.1 no.1 s.1
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• pp.103-115
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• 2001

The current procedure to design hydraulic structures in a small basin area is to estimate the probable rainfall depth using rainfall intensity formula. The estimation of probable rainfall depth has many uncertainties inherent with it. However, it has been inevitable to simplify the nonlinearity if the rainfall in practice. This study attend to address a method which can model the nonlinearity in order to derive better rainfall intensity formula for the estimation of probable rainfall depth. The results show that genetic algorithm is more reliable and accurate than trial-and-error method or nonlinear programming technique(Powell's method) in the derivation of the rainfall intensity formula.

• Proceedings of the Korean Geotechical Society Conference
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• 1999.03a
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• pp.113-120
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• 1999

Deep excavation,1 in the urban areas may cause terrible damages to the adjacent structures. Most damages are due to the settlement of ground during excavation work. This article introduces two actual examples of structure damage in subway construction projects. A through of attempts to find out the factors that are affecting to the settlement of ground was made through site investigations and analyses of measurement data. Some suggestions are given to prevent the repeat of trial and error in deep excavation projects. This kind of attempts are eccentrical to the development and improvement of information-oriented construction method.

• Korean Journal of Adult Nursing
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• v.28 no.3
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• pp.323-333
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• 2016

Purpose: The purpose of this study was to explore the meaning of the experience of adapting to the dietary treatment for hemodialysis patients. Methods: The data were collected through in-depth interviews of ten hemodialysis patients who have been dialyzed for longer than five months. Giorgi's phenomenological method was used for data analysis. Results: The findings included five constituents and 16 sub-constituents. The five constituents concerning diet therapy were: 'suffering', 'undergoing trial and error', 'understanding the need', 'finding alternatives', and 'realizing the meaning of dietary therapy.' Conclusion: The findings contribute to understanding the process of adapting to diet therapy. The results of this study may be utilized in assisting patients to understand the diet therapy process.

• Proceedings of the KIEE Conference
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• 2004.11c
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• pp.614-616
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• 2004

It is waste of time in industrial plant that the PI controller gain tuning. The PI controller has many trial-and-error steps for gain design. This paper proposes the optimum gain design of PI controller using a speed estimation in sensorless vector-control. In this method, a degree of stability and Hurwitz theory are applied and the controller gain is expressed by system parameters.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.1361-1366
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• 2007

Forging for spring cup of engine valve was investigated in this study. New method is needed to reduce cost and development lead time required to fix forming process of new product, that eventually can provide die, metal flow and forming loads with high confidence level. FEM could provide required detail information that could reduce trial error in advance before the actual production. By using the rigid-plastic finite element simulation, possibilities of improving former research were explored. Results generated by FEM could foresee expected material deformation in advance and made possible new forming process successfully.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.3
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• pp.55-63
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• 1991

Transforming small ultrasonic energy into large mechanical energy is the essential feature of ultrasonic vibration in various application fields. This energy amplification can be obtained by achieving resonance condition between booster or tool horn and transducer. When it has uniform section with small sectional area, one dimensional analysis provides good estimation of the natural frequency of the horn. But, for arbitrary shape of horn, one dimensional analysis can no longer be applied. At present, designing tool horn whose natural frequency is identical to that of transducer requires serveral stages of trial and error in actual manufacturing process. In this paper, frequency analysis program is developed to easily predict the natural frequency of ultrasonic vibration cutting tool with axisymmetry and 3- dimensional shape using finite element method.