• Advances in materials Research
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• v.11 no.4
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• pp.279-298
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• 2022

In this paper, the important novelty and the defining a physical phenomenon of the resent research is the development of nonlocal stress and strain parameters on the porous sandwich beam with functionally graded materials in the top and bottom face sheets.Also, various beam models including Euler-Bernoulli, Reddy and the generalized formulation of two-variable beam theories are obtained in this research. According to a nonlocal strain elasticity theory, the strain at a reference point in the body is dependent not only on the stress state at that point, but also on the stress state at all of the points throughout the body. Thus, the nonlocal stress-strain elasticity theory is defined that can be actual at micro/nano scales. It can be seen that the critical buckling load and transverse deflection of sandwich beam by considering both nonlocal stress-strain parameters is higher than the nonlocal stress parameter. On the other hands, it is noted that by considering the nonlocal stress-strain parameters simultaneously becomes the actual case.

• Advances in Energy Research
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• v.8 no.4
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• pp.253-264
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• 2022

This paper deals with the effects of design (active area, current density, membrane conductivity) and operating parameters (temperature, relative humidity) on the performance of hydrogen-fuelled proton exchange membrane (PEM) fuel cell. The design parameter of a PEM fuel cell with the active area of the single cell considered in this study is 25 cm² (5 × 5). The operating voltage and current density of the fuel cell were 0.7 V and 0.5 A/cm² respectively. The variations of activation voltage, ohmic voltage, and concentration voltage with respect to current density are analyzed in detail. The membrane conductivity with variable relative humidity is also analyzed. The results show that the maximum activation overpotential of the fuel cell was 0.4358 V at 0.21 A/cm² due to slow reaction kinetics. The calculated ohmic and concentrated overpotential in the fuel cell was 0.01395 V at 0.76 A/cm² and 0.027 V at 1.46 A/cm² respectively.

• International Journal of Korean Welding Society
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• v.1 no.1
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• pp.44-50
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• 2001

A genetic algorithm was applied to the arc welding process as to determine the near-optimal settings of welding process parameters that produce the good weld quality. This method searches for optimal settings of welding parameters through the systematic experiments without the need for a model between the input and output variables. It has an advantage of being capable to find the optimal conditions with a fewer number of experiments rather than conventional full factorial designs. A genetic algorithm was applied to the optimization of the weld bead geometry. In the optimization problem, the input variables were wire feed rate, welding voltage, and welding speed. The output variables were the bead height bead width, and penetration. The number of levels for each input variable is 16, 16, and 8, respectively. Therefore, according to the conventional full factorial design, in order to find the optimal welding conditions,2048 experiments must be performed. The genetic algorithm, however, found the near optimal welding conditions in less than 40 experiments.

• KDI Journal of Economic Policy
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• v.44 no.1
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• pp.77-98
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• 2022

This paper empirically verifies that the types of capital adjustment costs serve as an important mechanism in relation to investment decision-making after confirming that the investment dispersion of Korean firms is pro-cyclical and can affect business cycles. Specifically, it is found through empirical methods using corporate financial data that capital adjustment costs generally assumed to take a quadratic form in macroeconomics are asymmetric and irreversible in the Korean economy. In particular, capital adjustment costs are empirically proven to cause investment dispersion to expand given that the substitution effect of the marginal value to the marginal cost for one unit of investment in the inter-temporal investment decision is affected by that cost with regard to the resale of owned equipment assets, as opposed to new investments in equipment assets. We ultimately show, albeit indirectly, that investment dispersion can affect business cycles as capital adjustment costs influences investment decisions. What is implied is that the capital adjustment cost is not merely an exogenously deep parameter that fits the dynamics of business cycles in a macroeconomic model but could instead be a policy variable that can be endogenized through government policies.

• Annual Conference of KIPS
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• 2021.11a
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• pp.986-989
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• 2021

하나의 폰트를 제작하기 위해서, 로마자 폰트는 200여자만 디자인하면 되지만, 한글 폰트는 11,172자나 되는 많은 글자를 하나하나 디자인해야 하는 어려움이 있다. 하나의 한글 폰트 제작에 많은 시간과 노력이 드는 기존 문제점을 해결하기 위해, 메타폰트와 같은 프로그래머블 폰트를 이용하는 방법이 제안되었으나, 이를 실제 사용하는 것은 용이하지 않다. 따라서 이러한 문제를 해결하기 위해 한글 가변폰트 서비스를 위한 한글 매개변수 조절 서비스 "STEMFONT'를 개발하였다. 본 논문에서는 STEMFONT 서비스에 대한 소개와 더불어 서비스 기능에 맞는 인터페이스 구성에 대해 설명한다. 이러한 인터페이스를 통해 사용자들이 쉽게 폰트를 제작할 수 있다.

• Journal of Electrical Engineering and information Science
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• v.1 no.1
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• pp.39-44
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• 1996

In this paper, adaptive controller with switching action is designed for rigid body robot manipulators to ensure the uniform stability of the manipulator system without a priori knowledge of the unmodeled dynamics. It will be shown that the parameter estimates are bounded independent of the other closed-loop signals boundedness, and also shown that the tracking error belongs to the normalized error bound via mathematical analisys. The robustness and performance of the proposed adaptive controller is investigated for the two-link direct drive manipulator actuated by VRM(Variable Reluctance Motor).

• Journal of Advanced Navigation Technology
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• v.27 no.6
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• pp.884-887
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• 2023

Recently, research has been actively conducted to overcome the limitations of high-priced single sensors and reduce costs through the convergence of low-cost multi-variable sensors. This paper estimates state variables through asynchronous Kalman filters constructed using CVXPY and uses Cvxpylayers to compare and learn state variables estimated from CVXPY with true value data to estimate filter parameters of low-cost sensors fusion.

• Journal of applied mathematics & informatics
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• v.42 no.1
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• pp.139-148
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• 2024

The purpose of this research is to investigate sufficient conditions for the existence of limit cycles of the fifth-order differential equation x⁽⁵⁾ + (p² + q²)$_{x}^{...}$ + p²q²$_{x}^{.}$ = εF(t, x, $_{x}^{.}$, $_{x}^{..}$, $_{x}^{...}$, $_{x}^{....}$), where p, q are rational numbers different from 0, p ≠ ±q, ε is a small real parameter, and F is a 2kπ-periodic function in the variable t. Also, we provide some applications.

• Journal of Distribution Science
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• v.14 no.8
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• pp.123-128
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• 2016

Purpose - Korean Wave that overspreads around Asia and America, especially the Korean beauty wave, has reached Mongolia and Mongolian consumers. Mongolia consumers usually prefer foreign cosmetic brands to local brands, because the local brands cannot satisfy fast changing needs and wants of local consumers. Research design, data, and methodology - Based on previous studies about life style of Mongolian consumers, advertisement properties and consumer behaviors, we propose a research model and related hypothesis. In order to test hypotheses, we analyzed 366 survey data out of 376 by eliminating improper 10 responses. Factor analysis and reliability analysis was conducted by SPSS 22.0. We used multiple regression analysis and parameter analysis to test the relation between variables. Results - As exploring the Mongolian consumers' current usage of cosmetic products, we found that the customers' focus is how the products fit with their skin. Mongolian consumers often get the information about cosmetic products through TV and internet. Mongolian consumers show positive attitudes on the appearance of Korean celebrities in responsibility, while there is no significant effect on attractiveness. Mongolian consumer's behaviors toward brand have positive effect on both responsibility and attractiveness of Korean commercial celebrities. Responsibility and attractiveness of Korean commercial celebrities have positive effect on the behaviors toward advertisements of cosmetic products. Conclusions - Behaviors toward advertisements of cosmetic products have positive effect on both purchase intention and loyalty of customer. Responsibility and attractiveness of Korean commercial celebrities have positive effect on mediating variable of behavior toward advertisement and independent variable of purchase intention. Responsibility and attractiveness of Korean commercial celebrities have positive effect on mediating variable of behavior toward advertisement and independent variable of loyalty of customer. In order to improve the effect of advertisements, firms need to consider not only the technique of the model but also the image of model in regard to trust and professionalism appealing to consumers. In addition, firms need to choose the model who fits in with the image of the firms and the products and service of the firms. Finally, Mongolian consumers tend to acquire the shopping information through TV advertisements, especially featuring Korean popular stars, thus, TV advertisements can be a wise option in Mongolian cosmetic market.

• Journal of Korea Water Resources Association
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• v.39 no.10 s.171
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• pp.867-880
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• 2006

Hydrological models with many parameters and complex model structures require a powerful and detailed model calibration/validation scheme. In this study, we proposed a multi-variable and multi-site calibration and validation framework for the Soil Water Assessment Tool (SWAT) model applied in the Gap-cheon catchment located downstream of the Geum river basin. The sensitivity analysis conducted before main calibration helped understand various hydrological processes and the characteristics of subcatchments by identifying sensitive parameters in the model. In addition, the model's parameters were estimated based on existing data prior to calibration in order to increase the validity of model. The Nash-Sutcliffe coefficients and correlation coefficient were used to estimate compare model output with the observed streamflow data: $R_{eff}\;and\;R^2$ ranged 0.41-0.84 and 0.5-0.86, respectively, at the Heuduck station. Model reproduced baseflow estimated using recursive digital filter except for 2-5% overestimation at the Sindae and Boksu stations. Model also reproduced the temporal variability and fluctuation magnitude of observed groundwater levels with $R^2$ of 0.71 except for certain periods. Therefore, it was concluded that the use of multi-variable and multi-site method provided high confidence for the structure and estimated parameter values of the model.