• Journal of Navigation and Port Research
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• v.31 no.6
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• pp.471-478
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• 2007

This study is carried out the investigation of nonlinear characteristics of the field wave observation data acquired in the western sea area in Jeju island during one year. It is aimed to offer the fundamental data for Freak wave forecasting in real sea. For this, the nonlinear parameters of ocean waves, which are Skewness, Atiltness, Kurtosis and Spectrum band width parameter et al., are introduced, and the parameters are compared and discussed with some characteristics wave components, ie, significant wave height, maximum wave height, and so on. As a results, we know that the parameters describe nonlinear characteristics of observed wave spectrum broadly, are feebly related with occurrence of abnormal maximum wave height, namely freak event, however the Kurtosis, $K_t$ which is a degree of peakness of mode of surface elevation distribution, has better relationship than others.

• Journal of the Earthquake Engineering Society of Korea
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• v.15 no.4
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• pp.1-12
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• 2011

Seismic fragility analysis has been developed to evaluate the seismic performance of existing nuclear power plants, but now its applicability has been extended to buildings and bridges. In general, the seismic fragility curves are evaluated from the nonlinear time-history analysis (THA) using many earthquake ground motions. Seismic fragility analysis using the nonlinear THA requires a time consuming process of structural modeling and analysis. To overcome this shortcoming of the nonlinear THA, simplified methods such as the displacement coefficient method (DCM) and the capacity spectrum method (CSM) are used for the seismic fragility analysis. In order to evaluate the accuracy of the seismic fragility curve calculated by the DCM and the CSM, the seismic fragility curves of a reinforced concrete shear wall structure calculated by the DCM and CSM are compared with those calculated by the nonlinear THA. In order to construct a numerical fragility curve, 190 artificially generated ground motions corresponding to the design spectrum and the methodology proposed by Shinozuka et al. are used.

• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2008.04a
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• pp.313-316
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• 2008

에어컨 시스템은 압축기(Compressor), 응축기(Condenser), 증발기(Evaporator)와 확장밸브(Expansion Valve)로 구성되며, 에어컨 시스템에서 과열도와 저압(증발기의 압력)은 시스템의 효율 증대 및 성능 개선과 안정성에 대하여 결정적인 영향을 미친다. 따라서, 과열도와 저압을 조절하기 위해, 각각의 압축기내의 인버터 주파수와 확장밸브의 개도 제어가 중요하며 선형과 비선형 시스템 모두에 대하여 견실한 성능을 나타내고, 외란에 대하여 강인한 성능을 보이는 퍼지 제어기를 설계한다. 본 논문에서는 과열도와 저압을 제어하기 위하여, 3대의 확장밸브와 1대의 압축기를 가진 에어컨 시스템에 대하여 다중 퍼지 제어기를 설계한다. 또한, 각 제어 플랜트에 대하여 최적의 퍼지 제어기를 설계하기 위하여 3가지 최적화 알고리즘을 사용한다. 즉, 직렬 유전자 알고리즘(Serial Genetic Algorithm; SGA)과 병렬 유전자 알고리즘인 계층적 공정 경쟁 유전자 알고리즘(Hierarchical Fair Competition Genetic Algorithm; HFCGA), 그리고 Particle Swarm Optimization(PSO)을 사용하여 다중 퍼지 제어기를 최적화하고 시뮬레이션의 결과를 비교한다.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.23 no.9A
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• pp.2345-2354
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• 1998

There have been many researches to yield higher resolution image quality from the low resolution CCD device. The resolution of it is primary factor for the image quality of digital still camera and in manufacturing price. IN this paper, image enlargement algorithm, which reduces blocking effect of enlarged low resolution image and minimizes ringing and blur effect occurring around edge in linear interpolation, is proposed. This algorithm is composed of gaussian low pass filter which eliminates aliasing, least square spline interpolation and non-linear interpolation based on step edge model.

• 전자공학회논문지 IE
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• v.46 no.4
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• pp.49-56
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• 2009

In this paper, stabilization inverse optimal control for nonlinear systems with structural uncertainty is considered. Based on the control Lyapunov function, a theorem for the globally asymptotic stability is presented. From this a less conservative condition for the inverse optimal control is derived. The result is used to design an inverse optimal controller for a class of nonlinear systems, that improves and extends the existing results. The class of nonlinear system considered is also enlarger. The simulation results show the effectiveness of the method.

• The Journal of the Acoustical Society of Korea
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• v.19 no.4
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• pp.101-106
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• 2000

This study deals with the relationship between the magnitude of ultrasonic nonlinear parameter B/A, sound speed of amount of fat present in biological media for measuring B/A system using a wide band ultrasonic transducer. To represent this case, mixtures of egg white and egg yolk were studied. Even though the differences in density and sound speed of the two egg components were within 1% of each other, B/A were increases parabolically as a function of the fat density, which is not in agreement with the Yoshizumi et al's suggestion. In skim milk that does not contain fat, both the B/A and the sound speed increase with the solubility. It is proposed that protein could affect these values.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.8 no.1
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• pp.95-102
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• 1996

The skewness of near-bottom velocity distribution caused by the nonlinear interaction of the second order waves proposed by Wells (1967) has been re-evaluated. The direction of cross-shore sediment transport was related to the sign of the third moment (skewness) of velocity distribution, and a new concept of neutral depth which can explain the recovery of beach equilibrium after a disturbance is suggested. The seasonal change of beach profile due to the change of wave condition (storm-swell profile) is interpreted in terms of nonlinear interaction of the waves rather than the conventional wave steepness. The beach is eroded (storm profile) when the nonlinear interaction of the waves is strong (storm wave), whereas the beach is accreted (swell profile) when the nonlinear interaction is weak (swell wave).

• Journal of the Korean earth science society
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• v.26 no.5
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• pp.404-416
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• 2005

The seasonal and regional distribution of precipitation in Korea, terms of the amount of precipitation per day, number of days, and intensity was analyzed using precipitation data from 1971 to 2000. The significance level of the linear trend of these data was also investigated using the analysis of variance of each variable. The amount of precipitation per day less than 80 mm per day appeared in the Honam area which also shows a large number of precipitation day value during the fall and winter. However, the lowest amuont of precipitation per day was shown in the Youngnam area. The positive trend of the annual precipitation amount has also been detected in all stations except for a few station in Honam, and the positive trend of precipitation intensity is statistically significant in most of the stations at the Chungcheong and Gyeonggi area. The linear trend of precipitation intensity in these area is found to be significant at the $5\%$ level.

• Journal of Broadcast Engineering
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• v.25 no.2
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• pp.157-165
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• 2020

In this paper. we propose an effective compensation scheme to the quantization error arisen from quantized learning in a machine learning on an embedded system. In the machine learning based on a gradient descent or nonlinear signal processing, the quantization error generates early vanishing of a gradient and occurs the degradation of learning performance. To compensate such quantization error, we derive an orthogonal compensation vector with respect to a maximum component of the gradient vector. Moreover, instead of the conventional constant learning rate, we propose the adaptive learning rate algorithm without any inner loop to select the step size, based on a nonlinear optimization technique. The simulation results show that the optimization solver based on the proposed quantized method represents sufficient learning performance.

• Journal of the Korean Data and Information Science Society
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• v.27 no.3
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• pp.629-638
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• 2016

Among data mining techniques, the association rule is one of the most used in the real fields because it clearly displays the relationship between two or more items in large databases by quantifying the relationship between the items. There are three primary quality measures for association rule; support, confidence, and lift. We evaluate association rules using these measures. The approach taken in the previous literatures as to estimation of association rule number has been one of a determination function method or a regression modeling approach. In this paper, we proposed a few of non-linear regression equations useful in estimating the number of rules and also evaluated the estimated association rules using the quality measures. Furthermore we assessed their usefulness as compared to conventional regression models using the values of regression coefficients, F statistics, adjusted coefficients of determination and variation inflation factor.