• Journal of the Korea Institute of Military Science and Technology
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• v.12 no.1
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• pp.1-7
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• 2009

Tracking and detecting targets by the M/W seeker is affected by the clutter reflecting from the earth's surface. In order to detect the look-down retreating targets, which appear in the sidelobe clutter region, in the M/W seeker of High PRF mode, it is necessary to understand statistical characteristics of the surface sidelobe clutter. Statistical analysis of sidelobe clutter is conducted for several configurations of the surface using data obtained by the CFT (Captive Flight Test) of the M/W seeker in High PRF mode. The probability density function(PDF) fitting is conducted for several configuration and conditions of the surface. PDFs and PDF parameters, which best describe statistical distribution of sidelobe clutter, are estimated.

• Water Engineering Research
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• v.2 no.1
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• pp.1-10
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• 2001

The frequency analyses for the precipitation data in Korea were performed. We used daily maximum series, monthly maximum series, and annual series. For nonparametric frequency analyses, variable kernel estimators were used. Nonparametric methods do not require assumptions about the underlying populations from which the data are obtained. Therefore, they are better suited for multimodal distributions with the advantage of not requiring a distributional assumption. In order to compare their performance with parametric distributions, we considered several probability density functions. They are Gamma, Gumbel, Log-normal, Log-Pearson type III, Exponential, Generalized logistic, Generalized Pareto, and Wakeby distributions. The variable kernel estimates are comparable and are in the middle of the range of the parametric estimates. The variable kernel estimates show a very small probability in extrapolation beyond the largest observed data in the sample. However, the log-variable kernel estimates remedied these defects with the log-transformed data.

• Structural Engineering and Mechanics
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• v.76 no.5
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• pp.631-641
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• 2020

In the present work, an approach for the multiple time probabilistic characterization of the response of linear structural systems subjected to random non-Gaussian processes is presented. Its fundamental property is working directly on the multiple time probability density functions of the actions and of the response. This avoids of passing through the evaluation of the response statistical moments at multiple time or correlations, reducing the computational effort in a consistent measure. This approach is the extension to the multiple time case of a previously published dynamic Probability Transformation Method (PTM) working on a single evolution of the response statistics. The application to some simple examples has revealed the efficiency of the method, both in terms of computational effort and in terms of accuracy.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.1
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• pp.192-200
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• 1994

The methodology of a simple probabilistic fatigue crack under random loading is proposed. Using the crack closure concept, the crack opening stress is assumed to be constant during random loading. The loading history was analyzed to determine the probability density functions, probability distribution functions and other related parameters for the probabilistic fatigue crack growth analysis. Fatigue crack growth using the exisiting available data was predicted by the proposed probabilistic analysis and compared with experimental data.

• Journal of the Korean Society of Marine Environment & Safety
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• v.21 no.3
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• pp.253-258
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• 2015

The purpose of this study is to find suitable probability distribution function of complex distribution data like multimodal. Normal distribution is broadly used to assume probability distribution function. However, complex distribution data like multimodal are very hard to be estimated by using normal distribution function only, and there might be errors when other distribution functions including normal distribution function are used. In this study, we experimented to find fit probability distribution function in multimodal area, by using AIS(Automatic Identification System) observation data gathered in Mokpo port for a year of 2013. By using chi-squared statistic, gaussian mixture model(GMM) is the fittest model rather than other distribution functions, such as extreme value, generalized extreme value, logistic, and normal distribution. GMM was found to the fit model regard to multimodal data of maritime traffic flow distribution. Probability density function for collision probability and traffic flow distribution will be calculated much precisely in the future.

• Journal of Advanced Marine Engineering and Technology
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• v.28 no.6
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• pp.993-999
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• 2004

The estimation of fatigue life at the design stage of membrane type LNG tank is very important in order to arrive at feasible and cost effective solutions considering the total lifetime of the tank. In this study, the practical procedure of fatigue life prediction by use of cumulative damage factors based on Miner-Palmgren hypothesis and probability density function has been shown with the corner region of Gaz Transport Membrane type LNG tank being used as an example. In particular the parameters of Weibull distribution that determine the stress spectrum are discussed. The main results obtained from this study are as follows: 1. The recommended value for the shape parameter of Weibull distribution for the LNG tank is 1.1 in case of using the direct calculation method proposed in this study. 2. The calculated fatigue life is influenced by the shape parameter of Weibull distribution and stress block. The safe fatigue design can be achieved by using higher value of shape parameter and the stress blocks divided into more stress blocks.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.3
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• pp.301-309
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• 2003

The non linear control algorithm with actuator saturation for a randomly excited oscillator has been widely explored and has shown promising results, but the probabilistic analysis of the algorithm has been rarely made due to its non-linear nature and the fact that the analytical solution of probability density function (PDF) for controlled responses does not exist. In this paper, a method for the probabilistic analysis on the non linear control algorithm with actuator saturation is proposed based on the equivalent non linear system method. Numerical examples are given to verify the approximation solution of PDF comparing to a statistically obtained PDF using a Gaussian white noise and a Kanai - Tagimi filtered Gaussian white noise.

• Journal of ILASS-Korea
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• v.22 no.3
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• pp.137-145
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• 2017

This paper describes numerical modeling of transcritical and supercritical fluid flows within a liquid propellant rocket engine. In the present paper, turbulence is modeled by standard $k-{\varepsilon}$ model. A conserved scalar approach in conjunction with multi-environment probability density function model is used to account for the turbulent mixing of real-fluids in the transcritical and supercritical region. The two real-fluid equations of state and dense-fluid correction schemes for mixtures are used to construct thermodynamic data library based on the conserved scalar. In this study, calculations are made on two cryogenic nitrogen jets under different chamber pressures. Sensitivity analysis for two different real-fluid equations of sate is particularly emphasized. Based on numerical results, precise structures of cryogenic nitrogen jets are discussed in detail. Numerical results show that the current real-fluid model can predict the essential features of the cryogenic liquid nitrogen jets.

• Journal of the Korean Society of Combustion
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• v.7 no.2
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• pp.7-14
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• 2002

The probability density functions (PDF) of temperature were measured by coherent anti-Stokes Raman Spectroscopy (CARS) in flames of gas turbine combustor sector rig of an aero-engine. The combustor was operated at simulated ground idle conditions with standard kerosene fuel. Temperature PDFs had been measured near fuel nozzle with change of rotation of a swirler and existence of a prefilmer. The characteristic features of temperature PDFs showed the variation of combustion configurations at four experimental conditions. Without a prefilmer, large recirculation of high temperature gas was expected in the co-flow condition and un vaporized fuel fragments were detected in the counter-flow condition. With a prefilmer, the enhanced mixing increased combustion intensity near fuel nozzle in the counter-flow condition and the flame was attached far from the fuel nozzle in the co-flow condition.

• Communications for Statistical Applications and Methods
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• v.18 no.2
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• pp.245-255
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• 2011

There are two nonparametric methods that use empirical distribution functions and probability density estimators for the test of the distribution change of data. In this paper we investigate the two methods precisely and summarize the results of previous research. We assume several probability models to make a simulation study of the change point analysis and to examine the finite sample behavior of the two methods. Empirical powers are compared to verify which is better for each model.