• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2003년도 춘계학술발표대회 개요집
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• pp.29-31
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• 2003

Generally, the Quality of a weld joint is strongly influenced by process parameters during the welding process. In order to achieve high quality welds, mathematical models that can predict the bead geometry to accomplish the desired mechanical properties of the weldment should be developed. To achieve this objectives, a sensitivity analysis has been conducted and compared the relative impact of three process parameters on bead geometry in order to verify the measurement errors on the values of the uncertainty in estimated parameters. The results obtained show that developed mathematical models can be applied to estimate the effectiveness of process parameters for a given bead geometry, and a change of process parameters affects the bead width and bead height more strongly than penetration relatively.

• International Journal of Aeronautical and Space Sciences
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• 제15권2호
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• pp.173-182
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• 2014

The structured singular value (${\mu}$) analysis based method has many advantages for the robust stability analysis of missiles with uncertain parameters. Nevertheless, the present linear fractional transformation (LFT) modeling process, which is the basis of ${\mu}$ analysis, is complex, and not suitable for automatic implementation; on the other hand, ${\mu}$ analysis requires a large amount of computation, which is a burden for large-scale application. A constructive procedure, which is computationally more efficient, and which may lead to a lower order realization than existing algorithms, is proposed for LFT modeling. To reduce the calculation burden, an analysis method is developed, based on skew ${\mu}$. On this basis, calculation of the supremum of ${\mu}$ over a fixed frequency range converts into a single skew ${\mu}$ value calculation. Two algorithms are given, to calculate the upper and lower bounds of skew ${\mu}$, respectively. The validity of the proposed method is verified through robust stability analysis of a missile with real uncertain parameters.

• 한국해양공학회지
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• 제20권2호
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• pp.1-7
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• 2006

This paper, presents a comparison between numerical analysis and field test on a real offshore platform in Bohai Bay, China. This platform is a steel jacket offshore platform with vertical piles. The field testing under wave-induced force and wind force etc. was conducted, in order to obtain the dynamic parameters of the structure, including the frequencies of the jacket platform, as well as the corresponding damping ratios and mode shapes. The natural excitation technology (NexT) combined with eigensystem realization algorithm (ERA) and the peak picking (PP) method in frequency domain are carried out for modal parameter indentification under operational conditions. The three-dimeansional finite element model (FEM) is constructed by ANSYS and analytical modal analysis is performed to generate modal parameters. The analytical results were compared with experimental results. A good agreement was achieved between the finite element and analysis and field test results. It is further demonstrated that the numerical and experimental modal analysis provide a comprehensive study on the dynamic properties of the jacket platform. According to the analysis results, the modal parameters identification under ambient excitation can calibrate finite element model of the jacket platform structures, or can be used for the structural health monitoring system.

• 한국지진공학회논문집
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• 제22권6호
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• pp.333-343
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• 2018

In this paper, we study the existing results of the structure-soil-structure interaction (SSSI) effect on seismic responses of structures and summarize important parameters. The parameters considered in this study are a combination of buildings in the power block of a nuclear power plant, the characteristics of earthquake ground motions and its direction, and the characteristics embedded under the ground. Based on these parameters, the seismic analysis model of the structures in the power block of the nuclear power plant is developed and the structure-soil-structure interaction analyses are performed to analyze the influence of the parameters on the seismic response. For all analyses, the soil-structure interaction (SSI) analysis program CNU-KIESSI, which was developed to enable large-sized seismic analysis, is used. In addition, the SSI analyses is performed on individual structures and the results are compared with the SSSI analysis results. Finally, the influence of the parameters on the seismic response of the structure due to the SSSI effect is reviewed through comparison of the analysis results.

• International Journal of Concrete Structures and Materials
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• 제18권2E호
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• pp.89-95
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• 2006

This paper proposes a modified method of Latin Hypercube sampling to reduce the variance of statistical parameters in uncertainty analysis of concrete structures. The proposed method is a modification of Latin Hypercube sampling method. This analysis method uses specifically modified tables of random permutations of ranked numbers. In addition, the Spearman coefficient is used to make modified tables. Numerical analysis is carried out to predict the uncertainty of axial shortening in prestressed concrete bridge. Statistical parameters obtained from modified Latin Hypercube sampling method and conventional Latin Hypercube sampling method are compared and evaluated by a numeric analysis. The results show that the proposed method results in a decrease in the variance of statistical parameters. This indicates the method is efficient and effective in the uncertainty analysis of complex structural system such as prestressed concrete bridges.

• Journal of the Korean Statistical Society
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• 제23권2호
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• pp.463-482
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• 1994

In Bayesian analysis of randomized response models, the likelihood function does not combine tractably with typical priors for the parameters of interest, causing computational difficulties in posterior analysis of the parameters of interest. In this article, the difficulties are solved by introducing appropriate latent variables to the model and using the Gibbs sampling algorithm.

• 대한전기학회논문지:전기물성ㆍ응용부문C
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• 제49권5호
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• pp.310-314
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• 2000

To study the basic research of the lightning parameters for power system operation, LPATS(Lightning Positioning and Tracking System) has been introduced since 1995 in KEPCO(Korea Electric Power Corporation). We have developed the lightning parameters analysis program which can produce accumulative magnitude distribution of lightning current and IKL map by LPATS data. We obtained the various statistical distributions of lightning current parameters since 1996 by the lightning analysis program for the pertinent insulation design. In this paper, we describe the LPATS system in KEPCO, the statistical distribution of lightning current parameters and the IKL(Isokeraunic Level) map from 1996 to 1998. And the compared results between the calculated LFOR(lightning flashover rate) and the observed rate are also described.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.269-280
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• 2017

One major concern that has occupied the mind of the designers is a structural failure as result of stress concentration in the geometrical discontinuities. Understanding the effective parameters contribute to stress concentration and proper selection of these parameters enables the designer get to a reliable design. In the analysis of perforated isotropic and orthotropic plates, the effective parameters on stress distribution around holes include load angle, curvature radius of the corner of the hole, hole orientation and fiber angle for orthotropic materials. This present paper tries to examine the possible effects of these parameters on stress analysis of infinite perforated plates with central quasi-square hole applying grey wolf optimizer (GWO) inspired by the particular leadership hierarchy and hunting behavior of grey wolves in nature, and also the present study tries to introduce general optimum parameters in order to achieve the minimum amount of stress concentration around this type of hole on isotropic and orthotropic plates. The advantages of grey wolf optimizer are stout, flexible, simple, and easy to be enforced. The used analytical solution is the expansion of Lekhnitskii's solution method. Lekhnitskii applied this method for the stress analysis of anisotropic plates containing circular and elliptical holes. Finite element numerical solution is employed to examine the results of present analytical solution. Results represent that by selecting the aforementioned parameters properly, fewer amounts of stress could be achieved around the hole leading to an increase in load-bearing capacity of the structure.

• 대한의용생체공학회:의공학회지
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• 제27권2호
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• pp.47-52
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• 2006

The purpose of this study was to predict successful defibrillation in ventricular fibrillation using parameters extracted by wave analysis method and neuro-fuzzy. Total 15 dogs were tested for predicting successful defibrillation. Feature parameters were extracted for return of spontaneous circulation (ROSC) and non-ROSC by wave analysis method, and these parameters are an irregularity factor, spectral moments, mean power of level-crossing spectrum, and mean of alpha-significant value. Additionally, two parameters by analyzing method of frequency were extracted into a mean of power spectrum and a mean frequency. Then extracted parameters were analyzed in which parameters result to have high performance of discriminating ROSC and non-ROSC by a statistical method of t-test. The average of sensitivity and specificity were 62.5% and 75.0%, respectively. The average of positive predictive factor and negative predictive factor were 61.2% and 75.8%, respectively.

• 천문학회보
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• 제38권2호
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• pp.89.2-89.2
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• 2013

Solar energetic transients, e.g., flares, CMEs, etc., release large amount of energy which is expected to excite acoustic waves (p-modes) by exerting mechanical impulse of the thermal expansion of the flare on the photosphere. We study the p-mode properties of flaring and dormant active regions (ARs) to find association between flare and p-mode parameters. We compute the magnetic and flare activity indices of ARs using the line-of-sight magnetograms and GOES X-ray fluxes, respectively. The p-mode parameters are computed from the ring-diagram analysis. We correct p-mode parameters for magnetic field, filling factors and foreshortening by multiple linear-regression analysis. Our analysis of several flaring and dormant ARs observed during the Carrington rotations 1980-2109, showed strong association of mode parameters with magnetic and flare activities. We find that the mode parameters are contaminated by the geometrical effect. Mode amplitude decreases with angular distance from the solar disc centre. The mode width increases with magnetic activity while amplitude showed opposite relation due to mode absorption by the sunspot. After correcting modes due to all geometrical effects, magnetic activity and filling factor, we find that the modes amplitude, and mode energy increases with flare energy while width shows opposite relation.