• Proceedings of the Korean Institute of Intelligent Systems Conference
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• 2001.05a
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• pp.29-33
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• 2001

We propose fuzzy least-squares regression analysis by few error term data and test the slop by fuzzy hypotheses membership function for fuzzy number data with agreement index. Finding the agreement index by area for fuzzy hypotheses membership function and membership function of confidence interval, we obtain the results to acceptance or reject for the test of fuzzy hypotheses.

• Journal of Electrical Engineering and Technology
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• v.6 no.5
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• pp.713-722
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• 2011

In the present paper, the problem of stability analysis for linear systems with interval time-varying delays is considered. By introducing a new Lyapunov-Krasovskii functional, new stability criteria are derived in terms of linear matrix inequalities (LMIs). Two numerical examples are given to show the superiority of the proposed method.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.18 no.10
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• pp.2551-2561
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• 2014

Several algorithms have been developed to detect AFIB(Atrial Fibrillation) which either rely on the linear and frequency analysis. But they are more complex than time time domain algorithm and difficult to get the consistent rule of irregular RR interval rhythm. In this study, we propose algorithm for optimal value detection of irregular RR interval for AFIB classification based on linear analysis. For this purpose, we detected R wave, RR interval, from noise-free ECG signal through the preprocessing process and subtractive operation method. Also, we set scope for segment length and detected optimal value and then classified AFIB in realtime through liniar analysis such as absolute deviation and absolute difference. The performance of proposed algorithm for AFIB classification is evaluated by using MIT-BIH arrhythmia and AFIB database. The optimal value indicate ${\alpha}=0.75$, ${\beta}=1.4$, ${\gamma}=300ms$ in AFIB classification.

• Proceedings of the Optical Society of Korea Conference
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• 2009.10a
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• pp.331-332
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• 2009

We present an analysis on the quality factors of the Fourier hologram generated from multiple orthographic view images of three-dimensional object. In the analysis, we analyze both the maximum size of the reconstructed object and its spatial resolution. For the maximum size of the reconstruction, we found that the main factor is the orthographic projection angle interval. Too large projection angle interval causes overlapping in the reconstruction space domain. For the spatial resolution, there are three factors, i.e. the capturing lens array pitch which determines the spatial sampling rate of the original three-dimensional objects, the maximum orthographic projection angle, and the spatial frequency bandwidth of the object. The dominant factor is determined by the relationship between those three factors.

• Tribology and Lubricants
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• v.20 no.1
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• pp.33-40
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• 2004

This study represents the newly advanced formulation of hydraulic fluids for extended drain interval and introduces the performance results of used oil samples from various excavators. The used oil samples, in this paper, show that there is a sharp change in viscosity drop and moderate additive depletion when viscosity index of hydraulic oil is very high. For the extension of hydraulic fluid life, it is necessary to improve the stability of viscosity and oxidation. New target properties from the used oil analysis were proposed for extended life. Performance of newly developed hydraulic oil based on used oil analysis is compared with previously used one. The properties of new formulation are the viscosity index of 140 and improved thermal stability consists of VHVI base oil. Field test results showed the possibility of extension of fluid life. Additionally, for development of high performance product, new required propertied and performances were discussed.

• Tunnel and Underground Space
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• v.8 no.2
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• pp.79-86
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• 1998

This study was performed to suggest to suggest suitable design conditions of water curtain system through analysis on pressure down in boreholes by hydraulic tests carried out I construction fields for underground oil storages. The influence by hydraulic conductivities of rock mass around boreholes on pressure down in boreholes was analysed. The relationship between array of boreholes and their pressure down was also analysed. Groundwater flow analysis on crude oil and LPG storages was carried out to evaluate results of field tests and to investigate distribution of hydraulic gradient in rock mass around cavern using finite difference method. As the results, hydraulic tests showed that pressure down in boreholes was inverse proportional to the hydraulic conductivity of surrounding rock mass. The rate of pressure down of boreholes was not influenced by water curtain system more than 20m over cavern and was proportional to installation interval of boreholes. The hydraulic gradient in rock mass around cavern was proportional to distance and interval of boreholes and its value was not satisfactory to oil tightness condition in case of no water curtain system.

• Structural Engineering and Mechanics
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• v.27 no.3
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• pp.263-276
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• 2007

This paper presents a fuzzy finite element model for the analysis of structures in the presence of multiple uncertainties. A new methodology to evaluate the cumulative effect of multiple uncertainties on structural response is developed in the present work. This is done by modifying Muhanna's approach for handling single uncertainty. Uncertainty in load and material properties is defined by triangular membership functions with equal spread about the crisp value. Structural response is obtained in terms of fuzzy interval displacements and rotations. The results are further post-processed to obtain interval values of bending moment, shear force and axial forces. Membership functions are constructed to depict the uncertainty in structural response. Sensitivity analysis is performed to evaluate the relative sensitivity of displacements and forces to uncertainty in structural parameters. The present work demonstrates the effectiveness of fuzzy finite element model in establishing sharp bounds to the uncertain structural response in the presence of multiple uncertainties.

• Structural Engineering and Mechanics
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• v.38 no.6
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• pp.733-751
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• 2011

In the present study, a new kind of multivariable Reissner-Mindlin plate elements with two kinds of variables based on B-spline wavelet on the interval (BSWI) is constructed to solve the static and vibration problems of a square Reissner-Mindlin plate, a skew Reissner-Mindlin plate, and a Reissner-Mindlin plate on an elastic foundation. Based on generalized variational principle, finite element formulations are derived from generalized potential energy functional. The two-dimensional tensor product BSWI is employed to form the shape functions and construct multivariable BSWI elements. The multivariable wavelet finite element method proposed here can improve the solving accuracy apparently because generalized stress and strain are interpolated separately. In addition, compared with commonly used Daubechies wavelet finite element method, BSWI has explicit expression and a very good approximation property which guarantee the satisfying results. The efficiency of the proposed multivariable Reissner-Mindlin plate elements are verified through some numerical examples in the end.

• Journal of the Korean Society for Railway
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• v.11 no.3
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• pp.240-247
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• 2008

Recently, railway corporations have built maintenance information systems and collected failure and maintenance data. For example Seoul Metropolitan Rapid Transit Corporation (SMRT) built the Electric Motor Unit-Information System (EMU-IS) which is the first maintenance information system in Korea. It has been operated from August, 2000. This paper deals with a case study on determining maintenance interval through reliability analysis using EMU-IS fault data. Door system is considered for the case study in which reliability is evaluated for operating time and distance and the overhaul interval is determined.

• Plant Journal
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• v.9 no.4
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• pp.37-42
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• 2013

Power plants have many components and equipment. It is difficult for operators to know the each equipment fails or what equipment fails. It is important to prevent failure in advance. Recently, outlook of maintenance tasks is changing from time based maintenance to condition based maintenance. In this study, we selected RCM-based maintenance intervals for coal handling equipment at coal power plant. For RCM analysis, we have made great progress in a maintenance task and interval. If we apply RCM analysis to the whole plant system, we can expect qualitative improvement and efficient operation of power plant system.