• Particle and aerosol research
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• v.8 no.1
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• pp.1-8
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• 2012

In this study, the collection efficiency of inertial impactors was numerically simulated by employing the statistical Lagrangian particle tracking(SLPT) model. The SLPT model was proven to be correct in predicting the impactor collection efficiency, when the numerically obtained collection efficiencies were compared with the experimental data of Marple et al.(1987) at normal pressure level and the experimental data of $Marjam{\ddot{a}}ki$ et al.(2000) at low pressure level. Based on the validation results, balloon-borne impactors with the cut-off sizes of $1{\mu}m$, $2.5{\mu}m$, and $10{\mu}m$ were designed. Then, the sampling flowrates of the inertial impactors, required to keep the cut-off sizes constant at different pressures and temperatures, were estimated according to the altitude.

• International Journal of Aeronautical and Space Sciences
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• v.3 no.1
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• pp.30-38
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• 2002

In multi-dimensional systems, various solution schemes for radiative transfer are suggested but the applicabilities and accuracies of these schemes have not yet fully tested due to the lack of reference solutions especially for nongray gases. In this paper we present some precise radiative transfer solutions for a black walled 3-dimensional cylindrical system filled with nongray gases having uniform temperature and concentration. The ray-tracing method with the $T_N$ quadrature set and the SNB model are used to obtain the radiative transfer solutions by the nongray gases. The solutions presented in this paper are proved to be quite accurate and can be regarded as the reference solutions for the radiative transfer by nongray gases.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.20 no.4
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• pp.1356-1362
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• 1996

Fracture toughness of heterogeneous brittle materials such as poly crystalline ceramics used to present the size (thickness) effect as well as statistically distributed results. There is belief that both(size effect and scatter) must be associated with each other. However, no generally accepted theory has been established so far. Using statistical approach, a probabilistic modeling for the fracture toughness which describes the thickness effect was attempted in this paper, Weibull distribution of specific fracture energy(SFE)at local areas and Griffith criterion are applied to the model. In addition, the newly developed model was verified with experimental results of alumina.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.12 s.177
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• pp.170-174
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• 2005

A numerical system to extract effective elastic properties of polycrystalline thin-films for MEMS devices is developed. In this system, the statistical model based on lattice system is used for modeling the microstructure evolution simulation and the key kinetics parameters of given micrograph, grain distributions and deposition process can be extracted by inverse method proposed in the system. In this work, effects of kinetics parameters on the extraction of effective elastic properties of polycrystalline thin-films are studied by using statistical method. Effects of the fraction of the potential site($f_p$) among the parameters for deposition process of microstructure on the extraction of effective elastic properties of polycrystalline thin-films are investigated. For this research, polysilicon is applied to this system as the polycrystalline thin-films.

• Proceedings of the KSME Conference
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• 2003.04a
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• pp.1923-1929
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• 2003

The present study investigated the microcirculation of blood in the left common artery (LCCA). In order to develop a mathematical model for microcirculation in LCCA, the present study adopted preexisted set of measured morphological data on anatomy, mechanical properties of the coronary vessels, viscosity of blood, the basic laws of physics, and the appropriate boundary conditions. In this study, the statistical distribution of blood pressure, blood flow, and blood volume in the LCCA were determined based on the anatomical branching pattern of the coronary arterial tree and the statistical data of blood vessel dimensions. Our calculations were in good agreement with the previous studies. The present results showed that the mean longitudinal pressure drop profile was function of the vessel order numbers. It was found that the normalized pressure drop was a logarithmic function of the compliance.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.35 no.2
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• pp.64-70
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• 2012

This paper presents a statistical analysis method for the selection of electroencephalogram (EEG) electrode positions and spectral features to recognize emotion, where emotional valence and arousal are classified into three and two levels, respectively. Ten experiments for a subject were performed under three categorized IAPS (International Affective Picture System) pictures, i.e., high valence and high arousal, medium valence and low arousal, and low valence and high arousal. The electroencephalogram was recorded from 12 sites according to the international 10~20 system referenced to Cz. The statistical analysis approach using ANOVA with Tukey's HSD is employed to identify statistically significant EEG electrode positions and spectral features in the emotion recognition.

• Journal of Welding and Joining
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• v.34 no.2
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• pp.67-72
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• 2016

Aluminum alloy is one of light weight material and it is used to make LNG tank and ship. However, in order to weld aluminum alloy high density heat source is needed. In this paper, I-butt welding of Al 5083 with 6mm thickness using Plasma-MIG welding was carried out. The experiment was performed to investigate the influence of plasma-MIG welding parameters such as plasma current, wire feeding rate, MIG-welding voltage and welding speed on the tensile strength of weld. In addition we suggested 3 strength estimation models which are second order polynomial regression model, multiple nonlinear regression model and neural network model. The estimation performance of 3 models was evaluated in terms of average error rate (AER) and their values were 0.125, 0.238, and 0.021 respectively. Neural network model which has training concept and reflects non -linearity was best estimation performance.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.39 no.8
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• pp.751-758
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• 2015

Mathematical models are actively used to reduce the experimental expenses required to understand physical phenomena. However, they are different from real phenomena because of assumptions or uncertain parameters. In this study, we present a calibration and validation method using a paper helicopter and statistical methods to quantify the uncertainty. The data from the experiment using three nominally identical paper helicopters consist of different groups, and are used to calibrate the drag coefficient, which is an unknown input parameter in both analytical models. We predict the predicted fall time data using probability distributions. We validate the analysis models by comparing the predicted distribution and the experimental data distribution. Moreover, we quantify the uncertainty using the Markov Chain Monte Carlo method. In addition, we compare the manufacturing error and experimental error obtained from the fall-time data using Analysis of Variance. As a result, all of the paper helicopters are treated as one identical model.

• Transactions of Materials Processing
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• v.13 no.3
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• pp.248-252
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• 2004

The mechanical properties of polycrystalline thin-films, critical for Micro-Electro-Mechanical Systems (MEMS) components, are known to have the size effect and the scatter in the length scale of microns by the numbers of intensive investigation by experiments and simulations. So, the consideration of the microstructure is essential to cover these length scale effects. The lattice based stochastic model for the microstructure evolution is used to simulate the actual microstructure, and the fast and reliable algorithm is described in this paper. The kinetics parameters, which are the key parameters for the microstructure evolution based on the nucleation and growth mechanism, are extracted from the given micrograph of a polycrystalline material by an inverse method. And the method is verified by the comparison of the quantitative measures, the number of grains and the grain size distribution, for the actual and simulated microstructures. Finite element mesh is then generated on this lattice based microstructure by the developed code. And the statistical finite element analysis is accomplished for selected microstructure.

• International Journal of Reliability and Applications
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• v.5 no.1
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• pp.25-36
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• 2004

Ultrasonic inspection system consist of the examination procedures, equipment, and operators. The reliability of nondestructive testing is influenced by the inspection environment, materials and types of defect. It is very difficult to estimate the reliability of NDT due to the various factors. Piping inspection round robin was conducted to quantify the capability of ultrasonic inspection during in-service. In this study, the models for predicting the ultrasonic NDE reliability by logistic model and linear regression model are discussed. The utility of the NDT reliability assessment is verified by the analysis of the data from round robin test with these models.