• Journal of the Korean Society of Propulsion Engineers
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• 제17권5호
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• pp.80-85
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• 2013

This paper describes a probabilistic structural design method of composite propulsion system by comparing safety factor based on average value and allowable value with structural reliability. Generally, the required structural safety factor and reliability of composite pressure vessel are 1.5 and 0.999, respectively. In the case of structural design using average strength, the safety factor which satisfies the required structural reliability depends on the variation of fiber strength. However, the structural design using allowable value shows constant safety factor for the variation of fiber strength, because the allowable value of fiber strength is calculated by considering the variation of fiber strength. Through the analysis results, it was known that the fiber strength is the most important design random variable for the structural design of composite pressure vessel and the variation of fiber strength must be minimized to develop the high performance composite propulsion system.

• Journal of Radiation Protection and Research
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• 제47권2호
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• pp.77-85
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• 2022

Background: After the Fukushima Daiichi Nuclear Power Station (FDNPS) accident, a model was developed to estimate the external exposure doses for residents who were expected to return to their homes after evacuation orders were lifted. However, the model's accuracy and uncertainties in parameters used to estimate external doses have not been evaluated. Materials and Methods: The model estimates effective doses based on the integrated ambient dose equivalent (H^*(10)) and life patterns, considering a dose reduction factor to estimate the indoor H^*(10) and a conversion factor from H^*(10) to the effective dose. Because personal dose equivalent (H_p(10)) has been reported to agree well with the effective dose after the FDNPS accident, this study validates the model's accuracy by comparing the estimated effective doses with H_p(10). The H_p(10) and life pattern data were collected for 36 adult participants who lived or worked near the FDNPS in 2019. Results and Discussion: The estimated effective doses correlated significantly with H_p(10); however, the estimated effective doses were lower than H_p(10) for indoor sites. A comparison with the measured indoor H^*(10) showed that the estimated indoor H^*(10) was not underestimated. However, the H_p(10) to H^*(10) ratio indoors, which corresponds to the practical conversion factor from H^*(10) to the effective dose, was significantly larger than the same ratio outdoors, meaning that the conversion factor of 0.6 is not appropriate for indoors due to the changes in irradiation geometry and gamma spectra. This could have led to a lower effective dose than H_p(10). Conclusion: The estimated effective doses correlated significantly with H_p(10), demonstrating the model's applicability for effective dose estimation. However, the lower value of the effective dose indoors could be because the conversion factor did not reflect the actual environment.

• Journal of Practical Engineering Education
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• 제14권1호
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• pp.49-59
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• 2022

This study was conducted to develop a teaching competency scales customized for teaching programs conducted by Center for Teaching & Learning at A University. To achieve this purpose, a preliminary study was set up, which consists of three competency groups (basic competency, practice competency, innovation competency) and 26 learning competency factors through a review of previous studies. In order to verify the reliability and validity of the provisional teaching competency scales, an online survey was conducted on A university teachers in September 2020, The collected questionnaire data were organized and exploratory factor analysis and confirmatory factor analysis were conducted. As a result of exploratory factor analysis, 26 teaching competency was reduced to 17. As a result of the confirmatory factor analysis, the model was found to be good, Also, as a result of analyzing the construct reliability and AVE of the confirmed teaching competency factors, all 17 factors showed a good level of .7 or more. The teaching competency scales developed through this study can be used as basic data for performance evaluation and development of new programs of CTL teaching program.

• Journal of the Korean Home Economics Association
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• 제31권4호
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• pp.141-155
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• 1993

The purpose of this study is to investigate Korean youth's motivations for parenthood and concepts of parental role and to examine closely the relationship with the sociodemographic variables(age, sex, religious orientation, growth region, father's occupational level, parental education degree). the subjects are 465 students of the three universities in National Capital region. The data are collected by questionnair methods and analyzed by t-test, F-test, factor analysis. The major findings are as follows: 1) The motivations for parenthood are classified into five factors. These are acquisition of social status factor, continuation of self factor, achevement and creativity factor, tradition factor, primary group ties factor. The korean youth think the most of achievement and creativity factor among five motivation factors. 2) The korean students have somewhat stereo-typed concepts of parental role and place the stress on training the behaviors of the child and encouraging the development of the child. 3) The sociodemographic variables to have relationship with the motivations for parenthood are age, sex, growth region and father and mother's educational degrees. And the variables related with the concepts of parental role are sex, father's occupational level. 4) There are relationships between traditional role concepts of a father and motivation of acquisition of social status factor and tradition factor. And traditional role concepts of a mother are related with motivations of acquisition of social status factor and primary group ties factor among the motivations for parenthood.

• Korean Journal of Soil Science and Fertilizer
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• 제35권2호
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• pp.87-92
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• 2002

Soil erosion is detrimental to sustain soil productivity in north Korea, since agriculture of this country depends largely upon the slope land in mountainous area. Taking any measure for protection from erosion should be based on prediction of soil loss. Estimation of rainfall factor, R, in north Korea for the Universal Soil Loss Equation was attempted. The monthly precipitation data of the twenty six locations provided by the Korean Meteorological Adminstration were used. From the relationship between II_30 and the July-August precipitation concentration percents, the regional adjustment factor was obtained. The rainfall factor was calculated with the monthly precipitation data and the regional adjustment factor. The annual precipitation in north Korea ranged from 606 to 1,520mm, and the July-August precipitation concentration percents were 34.4 to 53.8. The regional adjustment factor ranged from 0.53 to 1.33 showing lower value in the highland and east coastal region than in the mid mountainous inland and west region. The R-factor value estimated from the monthly precipitation and the regional adjustment factor ranged from 107 to 483, which was lower than average value in south Korea.

• International Journal of Automotive Technology
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• 제7권4호
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• pp.423-439
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• 2006

This paper proposes a hybrid analytic method for the prediction of vibrational and acoustic responses of reverberant system in the medium-to-high frequency ranges by using the PFA(Power Flow Analysis) algorithm and SEA(Statistical Energy Analysis) coupling concepts. The main part of this method is the application of the coupling loss factor(CLF) of SEA to the boundary condition of PFA in reverberant system. The hybrid method developed shows much more promising results than the conventional SEA and equivalent results to the classical PFA for various damping loss factors in a wide range of frequencies. Additionally, this paper presents applied results of hybrid power flow finite element method(hybrid PFFEM) by formulating the new joint element matrix with CLF to analyze the vibrational responses of built-up structures. Finally, the analytic results of coupled plate structures and an automobile-shaped structure using hybrid PFFEM were predicted successively.

• KDI Journal of Economic Policy
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• 제39권4호
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• pp.25-50
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• 2017

Whereas a large variety of previous studies show mixed results regarding the relationship between public investment and economic outcome, several studies have been conducted on related issues in Korea. The present study deals with the effect of public investment in Korea on economic growth and productivity. Using administrative data, it exploits three different methodologies: the total factor productivity approach, production function approach, and stochastic frontier production function approach. The results of this study show that public investment has a statistically significant effect on economic growth. However, it contributes little to enhance productivity. It is explained that there exists inefficiency of production in the Korean economy. These findings indicate that public investment has played a central role in the direct input factor and not in indirect role in Korea. Thus, it is necessary for public investment policies to concentrate on enhancing the efficiency of the Korean economy.

• International Journal of Knowledge Content Development & Technology
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• 제5권2호
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• pp.103-122
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• 2015

This study examined student satisfaction with e-learning experiences in order to determine which factors had the greatest impact on reports of satisfaction among students at Konkuk University. We surveyed 4,889 students enrolled in e-learning courses and analyzed 830 completed questionnaires to identify factors that influence student satisfaction with e-learning. Results showed significant correlations between system factors and satisfaction ($R^2=0.577$; p = 0.000). The system factor with the greatest impact on satisfaction was course attendance rate (0.224; p = 0.000).

• BMB Reports
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• 제36권1호
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• pp.49-59
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• 2003

Platelet-derived growth factor (PDGF) is a critical regulator of mesenchymal cell migration and proliferation. The vital functions of PDGFs for angiogenesis, as well as development of kidney, brain, cardiovascular system and pulmonary alveoli during embryogenesis, have been well demonstrated by gene knock-out approaches. Clinical studies reveal that aberrant expression of PDGF and its receptor is often associated with a variety of disorders including atherosclerosis, fibroproliferative diseases of lungs, kidneys and joints, and neoplasia. PDGF contributes to cancer development and progression by both autocrine and paracrine signaling mechanisms. In this review article, important features of the PDGF isoforms and their cell surface receptor subunits are discussed, with regards to signal transduction, PDGF-isoform specific cellular response, and involvement in angiogenesis, and tumorstromal interactions.

• Journal of Power Electronics
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• 제8권1호
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• pp.51-59
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• 2008

This paper addresses several issues concerning the analysis, design, modeling, simulation and development of single-phase, single-switch, power factor corrected AC-DC high frequency switching converter topologies with transformer isolation. A detailed analysis and design is presented for single-switch topologies, namely forward buck, flyback, Cuk, Sepic and Zeta buck-boost converters, with high frequency isolation for discontinuous conduction modes (DCM) of operation. With an awareness of modem design trends towards improved performance, these switching converters are designed for low power rating and low output voltage, typically 20.25W with 13.5V in DCM operation. Laboratory prototypes of the proposed single-switch converters in DCM operation are developed and test results are presented to validate the proposed design and developed model of the system.