• 한국정보시스템학회지:정보시스템연구
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• 제13권1호
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• pp.121-134
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• 2004

As Internet usage widely grows, online content services such as newspaper, magazine, music, game and movie are provided with a fee-based subscription. Many content services providers consider charging a usage fee into its service provisions as one of the Internet business models for increasing revenue. There are customer resistances to adopting the fee-based service provision on the Web. Previous research in information systems (IS)has focused on the analysis of adoption of information technology or systems in the individual ororganization level. No principle research has been carried out on the user adoption behavior of online content services provisions. As users actively access content services on the Web, it needs to explore user adoption behavior in different settings. Many IS researcher have employedquantitative approaches, even though they deal with the process of user behavior regarding the information technology or system. In this study, we attempt to discover how customers adopt the fee-based provision of online content services by employing grounded theory, one of the principal qualitative research methods.

• 한국전기전자재료학회논문지
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• 제24권10호
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• pp.803-806
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• 2011

1 mol% $Li_2O$ excess $0.9(Na_{0.52}K_{0.48})NbO_3-0.1LiTaO_3$ lead-free piezoelectric multilayer ceramic actuators were investigated to determine their aging properties. To reduce the thermal aging behavior, we applied a rectified unipolar electric field of 5 kV/mm to the specimen to accelerate the electric aging behavior. By employing a rectified unipolar electric field for the piezoelectric actuators, we could remove undesirable heating from the relaxation current in the motion of the ferroelectric domain. To accelerate the aging test, the applied electric fields had a frequency of 900 Hz. To have enough time for charging and discharging, we employed an accurate time constant to design the equivalent circuit model for the aging tester. To extract exact aging behavior, we measured the pseudo-piezoelectric coefficient before and after the aging process. We also measured the electro-mechanical coupling coefficient, the frequency-dependent dielectric permittivity, and the impedance to compare with fresh and aged specimen.

• 한국수소및신에너지학회논문집
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• 제33권2호
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• pp.158-163
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• 2022

The test method on the Type II high-pressure hydrogen storage tanks made of the metal wire hoop winding is a complex and high risk. Also closeup on the tank being test is difficult. In this study, we studied a mechanical test method for a high-pressure hydrogen tanks. This method must be simple, risk-free and possible to observe the change in microscopic behavior of a metal wire on a liner. As the results, it was possible to observe the microscopic behavior on the metal wire by the mechanical test method. Also, a simple and risk-free test was possible compared to the conventional test method for high pressure hydrogen tanks.

• 무역학회지
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• 제47권5호
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• pp.1-20
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• 2022

As a part of environmental pollution mitigation in China, the number of environmentally friendly vehicles in China is proliferating, attention to vehicles that use environmentally friendly energy continues to increase, and China's new energy vehicle market is also growing rapidly. Similar to existing research, the focus of the subsidy is to provide financial support for electric vehicle buyers and the expansion of new energy vehicle charging infrastructure. Under these circumstances, this study attempts to understand the influence of Chinese consumers' green responsibility and other psychological factors on electronic vehicle purchase intention based on norm activation theory and theory of planned behavior. PLS-SEM examined the proposed hypotheses with 369 valid Chinese consumers, and all were supported. Our findings contribute to the extension of the research scope of Chinese consumers' intention to purchase electric vehicles and provide practical information for domestic and foreign firms entering China, the world's largest electric vehicle market.

• 대한기계학회논문집B
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• 제30권10호
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• pp.950-956
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• 2006

A mathematical heat transfer model for the prediction of heat flux on the slab surface and temperature distribution in the slab has been developed by considering the thermal radiation in the furnace and transient conduction governing equations in the slab, respectively. The furnace is modeled as radiating medium with spatially varying temperature and constant absorption coefficient. The slab is moved with constant speed through non-firing, charging, preheating, heating, and soaking zones in the furnace. Radiative heat flux which is calculated from the radiative heat exchange within the furnace modeled using the FVM by considering the effect of furnace wall, slab, and combustion gases is applied as the boundary condition of the transient conduction equation of the slab. Heat transfer characteristics and temperature behavior of the slab is investigated by changing such parameters as absorption coefficient and emissivity of the slab. Comparison with the experimental work shows that the present heat transfer model works well for the prediction of thermal behavior of the slab in the reheating furnace.

• 한국재료학회지
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• 제28권7호
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• pp.428-434
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• 2018

Hydrogen evolution on a steel surface and subsequent hydrogen diffusion into the steel matrix are evaluated using an electrochemical permeation test with no applied cathodic current on the hydrogen charging side. In particular, cyclic operation in the permeation test is also conducted to clarify the corrosion-induced hydrogen evolution behavior. In contrast to the conventional perception that the cathodic reduction reaction on the steel in neutral aqueous environments is an oxygen reduction reaction, this study demonstrates that atomic hydrogen may be generated on the steel surface by the corrosion reaction, even in a neutral environment. Although a much lower permeation current density and significant slower diffusion kinetics of hydrogen are observed compared to the results measured in acidic environments, they contribute to the increase in the embrittlement index. This study suggests that the research on hydrogen embrittlement in ultra-strong steels should be approached from the viewpoint of corrosion reactions on the steel surface and subsequent hydrogen evolution/diffusion behavior.

• 한국수소및신에너지학회논문집
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• 제34권6호
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• pp.689-697
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• 2023

The high-pressure hydrogen valve is intended to supply hydrogen charged at high pressure in the hydrogen tank to the fuel cell stack, which decompresses high-pressure hydrogen gas to low pressure and primarily limits the excessive flow. It consists of a pilot valve, a main valve, and a excessive flow valve to operate in a wide pressure range from 2 to 70 MPa of charging pressure. The opening characteristics of the valve were confirmed by computation fluid dynamics applying the moving grid technique. The behavior of the valve was predicted by predicting the force acting on the valve over time. In addition, the difference in behavior according to supply pressure was compared.

• 디지털융복합연구
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• 제18권2호
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• pp.151-162
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• 2020

본 연구의 목적은 중국 사용자들을 대상으로 온라인 지식 콘텐츠의 구매의도에 영향을 미치는 요인을 살펴보기 위함이다. 연구모형은 선행연구를 통해서 온라인 지식 콘텐츠 특성, 저작권 및 유료화 인식, 계획된 행동이론 변인, 구매의도 변수를 제시하였다. 설문조사를 통해서 최종 457부를 수집하였으며 SPSS 25.0과 AMOS 23.0을 이용하여 제시한 연구가설을 검증하였다. 연구결과에 의하면 온라인 지식 콘텐츠 특성은 태도에 부분적으로 영향을 미치는 것으로 나타났다. 또한, 유료화 인식과 계획된 행동이론 변인들은 구매의도에 긍정적인 영향을 있는 것으로 나타났다. 그리고, 이러한 연구결과를 활용한 온라인 지식 콘텐츠의 구매의도를 제고하는데 도움이 되는 방안을 제시하였으며, 실무적인 측면에서 유료 지식 콘텐츠의 운영 기업에 대한 시사점을 제시하였다. 또한, 향후 각종 콘텐츠 유료화 관련 후속 연구를 위한 토대를 제공할 것으로 사료된다.

• 한국가스학회지
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• 제24권6호
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• pp.61-69
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• 2020

본 논문은 압력과 온도조건에 따라 수소저장용기 TYPE 1에서 발생하는 거동특성을 FEM(Finite Element Method)으로 연구한 것이다. 용기의 구조안전성 평가를 위해 최고압력에서 발생한 VMS(Von Mises stress)을 소재의 YS(Yield Strength)를 비교하였고, 수명예측을 위한 기초데이터로써 PSED(Plastic Strain Energy Density) 결과를 분석하였다. 해석결과에 의하면 최고압력 40 Mpa 이상의 가스압에서 저장용기의 바닥면에 항복강도보다 높은 VMS가 발생하여 수소가스 저장용기의 안전성은 확보되지 않았다고 판단된다. 또한, 온도조건에 의해 발생한 VMS의 결과는 대단히 낮아서 온도에 의한 거동은 영향을 무시할 수 있다. VMS/YS이 1이하가 되는 최고압력은 약 30Mpa으로 계산되어 본 논문의 대상이 되는 수소저장용기는 30 Mpa이하의 가스충전압력으로 관리되어야 함을 알 수 있다.

• 에너지공학
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• 제22권4호
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• pp.338-346
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• 2013

일반 납축전지는 차량의 시동 성능 위주로 최적 설계되어 있다. 최근 차량 전장 시스템과 납축전지를 활용한 연비기술 적용의 증가로 납축전지의 사용 빈도가 늘어나고 있다. 연비기술 적용은 납축전지의 잦은 충방전 반응을 일으켜 납축전지 내구 수명을 단축시키고 있다. 본 연구에서는 납축전지의 노화 수명 모델 구현을 통해 배터리 내구 수명을 예측하는 방법을 제시하고자 한다. 납축전지의 노화에 영향을 미치는 요인은 방전율, 충전 시간, 완충 시간, 온도 조건 등이 있다. 본 논문에서는 납축전지의 동적 거동을 예측하기 위하여 전기화학반응 속도론, 이온의 전달현상, 전극 공극률의 시간에 따른 변화를 고려하였다. 수명 예측을 위해서 노화 메커니즘 중 노화에 가장 큰 영향을 주는 극판 부식 현상과 활물질 탈락을 노화 모델링에 반영하였다. 개발된 납축전지의 노화 모델을 검증하기 위하여 납축전지의 가속 충방전 시험을 수행하였다.