• Journal of Korean Society of Steel Construction
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• v.25 no.5
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• pp.579-585
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• 2013

Shear buckling stresses of steel pipes due to the lateral forces have been analyzed via parametric analysis. Detailed FEM models are prepared, and steel types, thickness, radii and length of steel pipes are selected as parameters. STK400, STK490 and SM570 are used and the thickness of pipe is 2mm and 40mm. The radii(R) and lengths(L) are determined based on the values satisfying the following relationship as R/t=20~400 and L/R=1~3. The shear buckling stresses decrease for all types of considered steels as R/t increase from 20 to 200. High strength steels are more sensitive to R/t, and also have an bigger effect on shear buckling stresses than low strength steels. It is found that shear buckling stresses decrease as L/R increases, showing that the steel pipes become weak as the length of the steel pipe increases.

• Journal of the Korean Society of Hazard Mitigation
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• v.10 no.6
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• pp.81-87
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• 2010

In order to calculate the accurate runoff from a basin, nonlinearity in the relationship between rainfall and runoff has to be considered. Many runoff calculation models assume the linearity in the relationship or are too complicated to be analyzed. Therefore, the storage function method has been used in the prediction of flood because of the simplicity of the model. The storage function method has five parameters with related to the basin and rainfall characteristics which can be estimated by the empirical trial and error method. To optimize these parameters, regression method or optimization techniques such as genetic algorithm have been used, however, it is not easy to optimize them because of the complexity of the method. In this study, the metamodel is proposed to estimate those model parameters. The metamodel is the combination of artificial neural network and genetic algorithm. The model is consisted of two stages. In the first stage, an artificial neural network is constructed using the given rainfall-runoff relationship. In the second stage, the parameters of the storage function method are estimated using genetic algorithm and the trained artificial neural network. The proposed metamodel is applied in the Peong Chang River basin and the results are presented.

• The Journal of the Korea Contents Association
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• v.14 no.2
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• pp.343-354
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• 2014

The purpose of this study was to investigate the effects of marital conflicts on dyadic adjustment and the mediating effects of positive emotion and sex-role attitude. The participants were total 270 middle-aged married people and data was collected from April 12 to June 24 in 2014. The data was collected with structured questionnaire and analyzed with the SPSS 17.0 and AMOS 18.0 programs. Results were as follows. First, marital conflicts had a significant direct effect and indirect effect through the mediation of positive emotion on dyadic adjustment. Second, positive emotion had a significant mediating effect but sex-role attitude did not. Third, The modified model showed a good fitness indices( ${\chi}^2$=38.90 standardized ${\chi}^2$=1.77(CMIN/df), GFI=.97, AGFI=.94, NFI=.98, SRMR=.02, CFI=.99, RMSEA=.05) and explanation power was 88.9%. These results suggest that middle-aged dyadic adjustment can be improved by increasing positive emotion. This study results will be contribute to develop intervention program for enhancement of marital relationship and education program for middle-aged.

• Journal of Industrial Convergence
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• v.18 no.1
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• pp.1-15
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• 2020

This study aims at examining the effect of strategic orientation on IT startup performance and analyzing the mediating effect of network in the relationship. The study was conducted on the three dimensions that make up strategic orientation: technological orientation, customer orientation, competitive orientation on firm performance, and the understanding of the role of the network. Empirical research on 94 IT startups as residents of startup support institutions was conducted. The suitability of the research model was evaluated with PLS-SEM. As a result of the empirical analysis, customer orientation and competitive orientation was verified to have a positive effect on network, while Technological orientation was confirmed to have no positive effect. and network mediated the relationship between customer orientation and competitive orientation, while Technological orientation was confirmed to have no positive effect. The results of this study provide startup practitioners with strategic direction and the importance of network establishment and utilization.

• The Journal of the Korea Contents Association
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• v.18 no.6
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• pp.131-143
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• 2018

The purpose of this study is to investigate whether ego-resilience has mediating effects on the relationships between elementary school student's smartphone dependence and attention. This study was conducted on 326 5th grade elementary school students in Gimhae city, and SPSS 24.0 program was used for data analysis. The result of this study was as follows. First, elementary school students' smartphone dependence showed a significant negative correlation with ego-resilience. Second, the elementary school students' smartphone dependence showed a significant negative correlation with attention. Third, as a result of analyzing the mediating effect of ego-resilience on the elementary school students' relationship with their smartphone dependence and attention, the ego-resilience has a partial mediating effect. Based on these results, suggestions were as follows: education for good use of smartphone, establishment and dissemination of family model related to smartphone use, and practical efforts and training to improve ego-resilience.

• Culinary science and hospitality research
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• v.16 no.1
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• pp.61-77
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• 2010

Hotel practitioners are searching for leadership typology to maximize employees' capabilities and consistency in their attitude. Also, they are increasingly interested in their employees' traits which constitute and influence their job attitude. This study sought to investigate the impact of servant leadership mediated through self-leadership on employees' job attitude. Focused on hotel restaurant employees, representing 15 hotels in Seoul Metropolitan Area, a survey was conducted and 272 respondents out of 297 were empirically analyzed. The collected data was analyzed with the SPSS 12.0 for Windows and AMOS software program. Structural equation modeling was conducted to test the hypotheses. The results suggested that servant leadership has a significant impact on self-leadership. Furthermore, self-leadership was found to have a significant impact on job satisfaction. However, direct influence of self-leadership on organizational commitment was not found. Finally, servant leadership was found to have a direct impact on job satisfaction. On the other hand, servant leadership positively influences on organizational commitment when mediated through self-leadership. In addition, this study provides practical implications for hotel restaurant professionals in linking servant leadership mediated through self-leadership to job attitude.

• Journal of the Earthquake Engineering Society of Korea
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• v.2 no.1
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• pp.1-10
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• 1998

In the dynamic soil-structure interaction(SSI) analysis, numerous uncertain parameters are involved. They include the uncertainties in the definition of input motions, modeling of soil-structure interaction systems. analysis techniques, etc. This paper presents the results of parametric studies of the seismic responses of a reactor containment structure built on the viscoelastic layered soil. Among the numerous parameter, this study concentrates on the effects of definition point of the input motion, embedment of structure to the base soil, thickness of the top soil layer, and rigidity of the base soil. The substructure method using frequency independent impedances is adopted. The method is based on the mode superposition method in time domain using the composite modal damping values of th SSI system computed from the ratio of dissipated energy to the strain energy for each model. From the study results, the sensitivity of each parameter on the earthquake responses has been suggested for the practical application of the substructure method of SSI analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.386-386
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• 2017

지하수 해석을 위해 3차원 수치해석 모형이 적용되고 있으나, 다양한 매개변수를 명확히 적용하기에는 한계가 있다. 특히, 수리전도도는 지층의 투수성정도를 나타내는 계수로 지하수 분석에 매우 중요한 매개변수이다. 신뢰성의 확보를 위해 양수시험을 통해 산출된 결과를 이용하고 있으나 소수관정의 시험결과를 유역의 대푯값으로 적용하기에 불확실도가 매우 높고, 수위변화가 독특한 지역의 정확한 수리특성을 적용하기에 한계가 있다. 이 연구에서는 수리전도도 특성을 해석하기 위하여 3차원 수치해석모형을 적용하였으며, 모델보정 방법 중 Regularization(정규화)라고 불리는 Pilot point 기법을 사용하였다. 제주도와 같이 수리전도도 값이 지역별로 차이가 크고 동일 유역 내에도 다른 지질구조를 보이는 등 동일 매질에서 동일 투수성을 보이지 않는 다양함으로 실측값들을 적용하기에 어려운 곳에서 정규화라는 보정방법은 최적화된 방법이다. 지하수위는 중제주유역 내 위치한 12개소 수위관측정의 2016년 연평균수위를 적용하였다. 미계측지역은 제주도 등수위선자료를 이용하여 DEM을 구축하였으며, 임의지점 17개소를 선정하여 대표수위로 적용하였다. 중제주유역의 평균 수리전도도는 82.90 m/day로 분석되었으며, 유역의 동측 하류부는 최대 1,745 m/day로 비교적 큰 결과가 산출되었다. 유역의 중앙에 위치하는 OR관측정을 기준으로 동 서지역의 지하수위를 검토한 결과 서측은 지형구배에 따라 지하수위가 형성하고 있으나, 동측의 경우 상 하류의 표고차가 30m이상 발생되지만 지하수위는 유사한 형태를 보이고 있다. 지하수 흐름에 해석되는 Darcy의 방정식은 수리전도도와 동수경사는 반비례관계를 나타내며, 이 이론에 의해 상 하류 지하수위가 유사하게 형성되는 동측지역은 국부적으로 수리전도도가 높게 형성되는 것으로 확인되었다. 실무에서는 유역경계에 따라 평균화된 매개변수가 적용되므로 명확한 지하수 해석이 어렵고, 수리전도도와 같이 지역적 편차가 심한 매개변수는 다양한 연구를 통해 적용성검토가 수행되어야 한다.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.366-366
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• 2017

하천의 유량관측 자료는 지표수자원의 확보와 수공구조물의 설계를 위해 가장 기초적인 수문자료로써 정밀하고 지속적인 관측을 요구한다. 최근 유량 관측법은 접촉식 유속측정 방법의 단점을 보완한 전자파 표면유속계나 영상분석기법을 적용한 표면영상유속계(SIV)가 활용되고 있다. 이들 관측장비는 표면유속 관측법에 의해 유량을 측정하므로 보다 정밀한 유량자료를 확보하기 위해서는 측정 영역의 표면유속과 단면의 평균유속에 대한 해석이 필요하다. 이 연구에서는 제주도 남부지역에 위치한 강정천을 대상으로 2011년 7월부터 2015년 6월 까지 월 1~2회 현장관측한 ADCP 자료를 활용하여 Chiu(1987)가 제안한 2차원 유속분포식의 매개변수를 추정하여 정밀한 유량을 산정하였다. 또한 표면영상유속계(SIV)로 산정된 표면유속을 Chiu-2 차원 유속분포식에서 평균유속으로 환산하여 기존의 표면유속을 일률적으로 적용한 수심평균유속 환산계수인 0.85의 적용 값과 비교 분석하였다. 대상하천의 현장에서 72회 관측된 ADCP 자료를 활용하여 각각의 최대유속과 평균유속을 분석하고 엔트로피 계수(M)를 산정한 결과와 유속의 공간적 분포를 모델링하기 위해 제시되는 $_{urf}$를 산정하였으며, 산정된 계수 값을 이용하여 표면유속을 계산한 결과와 ADCP의 관측된 표면유속의 $^2$는 0.874로 나타났다. 이러한 결과는 Chiu-2차원 유속분포식을 연구대상하천에 적용하는 과정에서 추정되는 매개변수의 평균값 사용에 대한 타당성을 보여준다. 이 후 추정된 하천매개변수를 하천현장에 적용성 확인을 위해 강정천의 동일 관측지점에서 표면영상유속계(SIV)를 사용한 표면유속과 유량을 산정함과 동시에 ADCP에 의한 유속 및 유량과 비교 분석하였다. 표면영상유속계(SIV)로 분석된 유속 벡터를 Chiu-2차원 유속분포식에 적용하여 산정된 유량과 기존의 수심평균유속환산계수 0.85를 적용한 유량은 각각 $0.7171m^3/s$과 0$0.5758m^3/s$였다. ADCP 평균유량 $0.6664m^3/s$과의 오차율은 각각 7.63%, 13.64%로 나타나 Chiu-2차원 유속분포식을 적용한 유량이 수심평균유속환산계수 0.85를 적용한 유량에 비해 작은 오차율을 보였다.

• The Journal of the Korea Contents Association
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• v.21 no.7
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• pp.619-628
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• 2021

This study identified the relationship between adolescents' alienation and stress responses, and examined the mediating model of smart media addiction moderated by behavioral activation system (BAS) on alienation and stress responses. Participants were 361 male and female students in middle and high schools located at Seoul metropolitan area. PROCESS Macro 3.5 Model 7 was used for analysis of the moderating mediating effect. Results revealed that adolescents' alienation and BAS were positively correlated with smart media addiction and stress responses, while smart media addiction was positively correlated with stress responses. In a moderated mediating model for stress responses, there was significant interaction effect of alienation and BAS; conditionally indirect effect of alienation was not significant in groups with very low BAS. These findings suggest that adolescents who feel alienation are more likely to experience stress responses by overindulging themselves in using smart media. The moderating effect suggests that this effect is stronger with higher levels of BAS.