• 한국추진공학회지
• /
• 제17권5호
• /
• pp.80-85
• /
• 2013

본 논문은 평균값과 Allowable 값 기준의 구조 안전율과 구조 신뢰도와 관계 비교를 통해 복합재 추진기관의 확률적 구조 설계 방법을 설명하였다. 일반적으로 복합재 압력용기의 평균 값 기준의 구조설계는 1.5 이상의 구조 안전율과 0.999 이상의 구조 신뢰도 값이 요구된다. 요구 압력 기준의 0.999의 구조 신뢰도를 만족하기 위해서 평균 값 기준의 구조설계는 섬유 강도의 변동률에 따라 다른 구조 안전율을 부여해야한다. 그러나 이미 섬유 강도 변동률이 고려된 Allowable 값을 이용할 때는 고정된 안전율이 부여된다. 이상의 해석 결과로 볼 때 섬유 강도는 복합재 압력용기 구조 설계에 가장 중요한 설계 변수이고, 우수한 성능의 복합재 추진기관을 개발하기 위해서는 섬유 강도의 변동률이 최소화되어야 함을 알 수 있었다.

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

• 실천공학교육논문지
• /
• 제14권1호
• /
• pp.49-59
• /
• 2022

본 연구는 A대학 교수학습센터(Center for Teaching & Learning)의 교수지원 프로그램 특성에 부합하는 교수역량 진단도구를 개발하고자 수행되었다. 이러한 연구목적을 달성하기 위해 선행연구 검토를 통해 3개 역량군(기본역량, 실천역량, 혁신역량)과 13개 교수역량, 26개 하위역량 요인으로 구성된 잠정적 교수역량 진단도구를 설정하였다. 잠정적 교수역량 진단도구의 신뢰도 및 타당도 검증을 위해 2020년 11월에 A대학교 교수자를 대상으로 온라인 설문조사를 실시하였으며, 설문 데이터를 정리하여 탐색적 요인분석과 확인적 요인분석을 수행하였다. 탐색적 요인분석 결과, 기본역량, 실천역량, 혁신역량 3개 역량군에 포함되는 26개 하위역량이 17개로 축소되었다. 확인적 요인분석을 실시한 결과, 모형의 적합도가 양호한 것으로 나타나 CTL 맞춤형 교수역량(하위역량) 17개 영역, 79개 문항을 최종 확정하였다. 또한 확정된 교수역량 요인의 개념신뢰도와 분산추출지수, 판별타당도를 분석한 결과 양호한 수준을 보였다. 본 연구를 통해 개발된 교수역량 진단도구는 CTL 교수지원 프로그램의 효과성 평가와 신규 프로그램 개발의 근거자료로 활용될 수 있다.

• 대한가정학회지
• /
• 제31권4호
• /
• pp.141-155
• /
• 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.

• 한국토양비료학회지
• /
• 제35권2호
• /
• pp.87-92
• /
• 2002

북한 지역은 산이 많고, 경사지 밭이 많아 토양 유실이 심하므로, 토지를 보호하는 것이 토양의 지력 유지에 중요하다. 토양 보전 대책 마련을 위해서는 각 지역의 토양 유실 가능량을 예측하는 것이 필요하다. 토양 유실 예측에 USLE가 광범위하게 적용된다. 북한 지역의 토양 유실 예측에 필요한 강수 인자8의 산출이 시도되었다. 북한 지역의 수집 가능한 75개소의 월 강수량 자료를 이용하였다. 월 강수량의 7, 8월 강수 집중도(X)로부터 지역 보정 인자를 산출하였다. 지역 보정 인자($U_{adj}$) 산출을 위한 기본식은 남한의 중북부 지역 20개소의 $EI_{30}$와 월강수량 자료로부터 얻어 낸 식 $$U_{adj}=4.095{\cdot}X-0.878(r=0.689^{**})$$ 을 적용하였다. 북한 지역의 강수량은 606-1,520mm이었으며, 7, 8월 집중도는 34.4%~53.8%이었다. 이에 따른 지역 보정 계수 $U_{adj}$는 0.53~1.33이었으며, 동해안과 산간 지방의 $U_{adj}$ 값이 서해안과 내륙 지방의 $U_{adj}$ 값보다 낮았다. 지역 보정 계수를 고려한 USLE의 강수 인자 $R_{adj}$는 107 ~ 493으로 평가되었으며, 이는 평균 259.6으로 남한의 평균 R 값 434.5보다 낮았다.

• International Journal of Automotive Technology
• /
• 제7권4호
• /
• pp.423-439
• /
• 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
• /
• 제39권4호
• /
• pp.25-50
• /
• 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
• /
• 제5권2호
• /
• pp.103-122
• /
• 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
• /
• 제36권1호
• /
• pp.49-59
• /
• 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
• /
• 제8권1호
• /
• pp.51-59
• /
• 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.