• 한국보육학회지
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• 제18권2호
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• pp.203-215
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• 2018

본 연구의 목적은 구조방정식모델을 이용하여 유아 기질과 애착이 어떠한 경로로 유아 놀이성에 영향을 주는가를 살펴보고자 하는 것이었다. 이를 위해 U시에 소재한 유치원에 재원중인 만 5세 유아 275명을 연구대상으로 유아 놀이성(CPS), 기질(DOST-R) 및 애착(IPPA)을 측정하였다. 수집된 자료는 SPSS와 AMOS 프로그램을 통하여 기술통계, Pearson 상관계수 및 구조모형분석을 실시하였다. 모형의 적합도는 ${\chi}^2$, RMSEA, NNFI, CFI 및 SRMR로 평가되었다. 연구결과를 살펴보면 첫째, 유아 기질과 유아 놀이성 간에 정적상관관계가 나타났으며 유아 애착과 유아 놀이성간에도 정적상관관계가 나타났다. 둘째, 유아 애착은 유아 놀이성에 직접효과가 있는 것으로 나타났고 유아 기질은 유아 애착을 거쳐 유아 놀이성에 간접효과가 있는 것으로 나타났다.

• 한국전산구조공학회논문집
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• 제18권4호통권70호
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• pp.395-404
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• 2005

본 논문에서는 동적하중 재하 시 공간 강뼈대 구조물의 비선형 시간이력 해석에 대한 간편하고 효율적인 수치해석 기법을 제시하였다. 뼈대의 강성행렬에 안정함수를 적용함으로서 기하학적 비선형성 즉 P-$\delta$ 및 P-$\Delta$ 효과를 고려하였다. 접선계수 개념 및 New Orbison 완전 소성면에 기초한 연화소성힌지를 적용하여 축방항력에 의한 부재의 점진적 항복 및 휨에 의한 부재의 부분 소성화를 고려하였다. 증분형태로 정식화된 뼈대 구조의 동적평형방정식의 해를 수치적으로 구하기 위하여 적분형태의 평균가속도법을 사용하여 컴퓨터 프로그램을 개발하였다. 검증 예제에 대하여 보요소 모델을 사용한 ABAQUS 및 개발된 프로그램에 의한 해석결과를 비교함으로서 개발된 프로그램의 정밀도와 해석시간에 대한 효율성을 입증하였다.

• Tribology and Lubricants
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• 제34권3호
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• pp.107-114
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• 2018

This paper presents a computational model of a gas foil journal bearing with shim foils between the top foil and bumps, and predicts its static and dynamic performance. The analysis takes the previously developed simple elastic foundation model for the top foil-bump structure and advances it by adding foil models for the "shim foil" and "outer top foil." The outer top foil is installed between the (inner) top foil and bumps, and the shim foil is installed between the inner top foil and outer top foil. Both the inner and outer top foils have an arc length of $360^{\circ}$, but the arc length of the shim foil is shorter, which causes a ramp near its leading edge in the bearing clearance profile. The Reynolds equation for isothermal and isoviscous ideal gas solves the hydrodynamic pressure that develops within the bearing clearance with preloads due to the ramp. The centerline pressure and film thickness predictions show that the shim foil mitigates the peak pressure occurring at the loading direction, and broadens the positive pressure as well as minimum film thickness zones except for the shortest shim foil arc length of $180^{\circ}$. In general, the shim foil decreases the journal eccentricity, and increases the power loss, direct stiffness, and damping coefficients. As the shim foil arc length increases, the journal eccentricity decreases while the attitude angle, minimum film thickness, and direct stiffness/damping coefficients in the horizontal direction increase.

• 한국강구조학회 논문집
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• 제27권5호
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• pp.435-445
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• 2015

콘크리트 충전형 합성강관(Concrete Filled steel Tube, CFT)는 우수한 연성과 강도를 발휘하며 건축물의 기둥 및 해양구조물의 교각 등에 적용되고 있다. 현존하는 CFT 전단 설계식은 지나치게 보수적이며 이는 CFT의 경제성과 시공성에 영향을 미친다. 그러나 합리적인 전단 설계식 제안을 위한 실험 연구는 거의 존재하지 않는다. 이 연구는 원형 콘크리트 충전 강관의 개선된 전단 설계식을 제안하기 위한 해석적 연구이다. 선행 연구에서 제시한 원형 CFT 해석 모델을 참고하여 해석 연구를 수행하였으며 해석 모델은 기존 실험 연구 결과를 이용하여 검증하였다. 검증된 모델을 이용하여 변수 연구를 수행하였으며 전단성능에 끝단길이, 콘크리트의 압축강도, 직경두께비가 미치는 영향을 평가하였다.

• Journal of Information Technology Applications and Management
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• 제26권6호
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• pp.29-46
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• 2019

This study analyzed the factors influencing the technology acceptance of the general public in the drones and ARs, one of the key technologies of the industry 4.0. The theoretical basis was the extended unified theory of acceptance and use of technology model(UTAUT2), which uses performance expectancy, effort expectancy, social influence, facilitating conditions, and hedonic motivation as factors common to both services. The price value factor was excluded considering that most ARs were free, and the perceived risk factors, including privacy, which were not in UTAUT2, were included because they are important factors for ICT technology acceptance. The hypothesis was tested by structure equation model. Social influence and hedonic motivation had a positive(+) effect on intention to use technology. On the other hand, in the case of effort expectancy, neither the AR nor the drone had a significant influence on intention to use technology. Furthermore, performance expectancy had a positive(+) effect on intention to use in AR, but no significant influence was found out in drones. On the contrary, in the case of the facilitating conditions, the influence of the drones was positive (+), but the relation of AR was not investigated. The perceived risk was tested for the negative (-) influence of use intention of AR, but no significant relationship was found out for the drones. Among the significant influencing factors, hedonic motivation was the most powerful factor in AR and drones. Theoretical and practical implications are presented based on these results.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집A
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• pp.377-382
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• 2001

Mechanical behavior and electrical resistance change of CPDP (carbon particle dispersed plastic) composite consisting of epoxy resin and conductive carbon particle were investigated under monotonic loading and repeated loading-unloading. The electrical resistance almost linearly increased with increasing strain during loading and the residual electrical resistance was observed even after removing load. The value of the residual electrical resistance was dependent on the maximum strain under the applied stress. This result suggests that the estimation of maximum strain (i.e., damage) is possible by the measuring electrical resistance of composite. The behavior of electrical resistance change during and after loading was discussed on the basis of the results of microscopic deformation and fracture observation. Moreover, the relationship between the volume fraction of carbon particle and the electrical resistivity of CPDP was investigated in relation to the percolation theory. Simulation model of percolation structure was established by Monte Carlo method and the simulation result was compared to the experimental results. The electrical resistance change under applied loading was analyzed quantitatively using the percolation equation and a simple model for the critical volume fraction of carbon particle as a function of the mechanical stress. It was revealed that the prediction was in good agreement with the experimental result except in the region near the failure of material.

• 디지털융복합연구
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• 제11권3호
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• pp.263-272
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• 2013

본 연구는 복합기 제품에 있어서의 지각된 품질 요인, 브랜드이미지, 고객충성도 간의 관계를 규명함으로써 충성고객 확보에 효과적으로 접근할 수 있는 컨설팅 영역을 알아보고자 진행하였다. 연구목적의 달성을 위하여 관련 선행연구를 근거로 연구모형과 가설을 수립한 후 산업체의 구매의사 결정자를 대상으로 자료를 수집하여 타당성 분석 및 신뢰도 분석과 구조방정식모형 분석을 실시하였다. 본 연구의 결과를 요약하면 다음과 같다. 첫째, 복합기의 지각된 품질 구성요인이 브랜드이미지에 미치는 영향 정도는 제품품질, 판매원 서비스 속성, 서비스 품질의 순으로 확인되었다. 둘째, 복합기 제품의 브랜드이미지는 고객충성도에 긍정적인 영향을 미치는 것으로 나타났다. 본 연구는 복합기 제품과 관련한 연구범위를 경영분야까지 확장하였다는데 의의가 있으며 복합기 제품과 유사한 사업구조를 갖는 산업에 있어서의 경영전략 수립 실무 및 경영 컨설팅에 도움을 줄 것으로 기대된다.

• 한국정보시스템학회지:정보시스템연구
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• 제29권2호
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• pp.95-110
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• 2020

Purpose This paper attempts to explain the recent expanding trend in Mobile Grocery Shopping(MGS). More specifically, the authors have applied the Post Acceptance Model(PAM) in order to examine the conceptual structure among the four constructs of 'Expectation Confirmation', 'Perceived Usefulness', 'User Satisfaction', and 'Continuance Intention to Use' in Mobile Grocery Shopping. Design/methodology/approach Through a survey agency, data were collected from a sample of 312 consumers who had the previous experience in Mobile Grocery Shopping. The Structural Equation Modeling(SEM) analysis was conducted with the survey data using AMOS 22.0. Subsequently, 8,200 real customer data from an open market site were collected in order to find out their revisit and repurchase behavior. Findings This study supported the causal relationships of Expectation Confirmation → Perceived Usefulness, Expectation Confirmation → User Satisfaction, Perceived Usefulness → User Satisfaction, and User Satisfaction → Continuance Intention to Use, but did not support the direct effect of Perceived Usefulness on the Continuance Intention to Use Mobile Grocery Shopping. This implies that consumers with any experience in Mobile Grocery Shopping would not consider repurchase, unless they are satisfied with the experience even though they perceive its usefulness. Also, Expectation Confirmation has much larger effect on User Satisfaction than Perceived Usefulness. In addition, the real customer data showed that the revisit and the repurchase rate of mobile grocery shoppers were higher than those of online grocery shoppers, although the rates of adding to shopping carts, coupon downloads, and adding to favorites are similar.

• 한국전산구조공학회논문집
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• 제27권1호
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• pp.17-26
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• 2014

본 논문은 MLS(Moving Least Squares) 차분법을 바탕으로 동적균열전파 해석을 수행하기 위한 알고리즘을 제시한다. MLS 차분법은 절점만으로 이루어진 수치모델을 사용하며, 이동최소제곱법을 이용하여 전개한 Taylor 다항식을 기초로 미분근사식을 유도하기 때문에, 요소망의 제약에서 완벽하게 벗어난 절점해석이 가능하다. 시간항을 포함하는 동적 평형방정식은 Newmark 방법으로 시간적분 하였다. 동적하중을 받는 균열이 전파할 때, 매 시간단계마다 절점모델을 재구성하지 않고 균열선단 주변에서 국부적인 수정을 통해 해석이 가능하다. 동적균열을 묘사하기 위해 가시한계법(visibility criterion)을 적용하였고, 동적 에너지해방률을 산정하여 균열의 진전유무와 그에 상응하는 진전방향을 결정하였다. 모드 I 상태와 혼합모드 상태에서 균열이 진전하는 현상을 모사하였고, 이론해와 Element-Free Galerkin법으로 계산한 결과와의 비교를 통해 개발된 알고리즘의 정확성과 안정성을 검증하였다.

• Korean Chemical Engineering Research
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• 제56권2호
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• pp.275-280
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• 2018

Methyl ester derived from coconut oil is very interesting to study since it contains free-fatty acid with chemical structure of medium carbon chain ($C_{12}-C_{14}$), so the methyl ester obtained from its part can be a biodiesel and another partially into biokerosene. The use of heterogeneous catalysts in the production of methyl ester requires severe conditions (high pressure and high temperature), while at low temperature and atmospheric conditions, yield of methyl ester is relatively very low. By using microwave irradiation trans-esterification reaction with heterogeneous catalysts, it is expected to be much faster and can give higher yields. Therefore, we studied the production of methyl ester from coconut oil using CaO catalyst assisted by microwave. Our aim was to find a kinetic model of methyl ester production through a transesterification process from coconut oil assisted by microwave using heterogeneous CaO catalyst. The experimental apparatus consisted of a batch reactor placed in a microwave oven equipped with a condenser, stirrer and temperature controllers. Batch process was conducted at atmospheric pressure with a variation of CaO catalyst concentration (0.5; 1.0; 1.5; 2.0, 2.5%) and microwave power (100, 264 and 400 W). In general, the production process of methyl esters by heterogeneous catalyst will obtain three layers, wherein the first layer is the product of methyl ester, the second layer is glycerol and the third layer is the catalyst. The experimental results show that the yield of methyl ester increases along with the increase of microwave power, catalyst concentration and reaction time. Kinetic model of methyl ester production can be represented by the following equation: $-r_{TG}=1.7{\cdot}10^6{_e}{\frac{-43.86}{RT}}C_{TG}$.