• 한국태양에너지학회 논문집
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• 제25권4호
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• pp.1-11
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• 2005

The stoichiometric mixture of evaporating materials for the $CuInSe_2$ single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CuInSe_2$, it was found tetragonal structure whose lattice constant $a_0$ and $c_0$ were $5.783\;{\AA}$ and $11.621\;{\AA}$, respectively. To obtain the $CuInSe_2$ single crystal thin film, $CuInSe_2$ mixed crystal was deposited on throughly etched GaAs(100) by the HWE(Hot Wall Epitaxy) system. The source and substrate temperature were $620^{\circ}C$ and $410^{\circ}C$ respectively. The crystalline structure of $CuInSe_2$ single crystal thin film was investigated by the double crystal X-ray diffraction(DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the $CuInSe_2$ obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=1.1851\;eV-(8.99{\times}10^{-4}\;eV/K)T^2/(T+153\;K)$. The open-circuit voltage, short current density, fill factor, and conversion efficiency of $n-CdS/p-CuGaSe_2$ heterojunction solar cells under $80\;mW/cm^2$ illumination were found to be 0.51V, $29.3\;mA/cm^2$, 0.76 and 14.3 %, respectively.

• 한국태양에너지학회 논문집
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• 제38권1호
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• pp.25-36
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• 2018

The stoichiometric mixture of evaporating materials for the $CaAl_2Se_4$: Co single crystal thin film was prepared from horizontal furnace. Using extrapolation method of X-ray diffraction patterns for the polycrystal $CaAl_2Se_4$, it was found orthorhomic structure whose lattice constant $a_0$, $b_0$ and $c_0$ were 6.4818, $11.1310{\AA}$ and $11.2443{\AA}$, respectively. To obtain the $CaAl_2Se_4$: Co single crystal thin film, $CaAl_2Se_4$: Co mixed crystal was deposited on throughly etched Si (100) by the HWE (Hot Wall Epitaxy) system. The source and substrate temperature were $600^{\circ}C$ and $440^{\circ}C$ respectively. The crystalline structure of $CaAl_2Se_4$: Co single crystal thin film was investigated by the double crystal X-ray diffraction (DCXD). Hall effect on this sample was measured by the method of Van der Pauw and studied on carrier density and mobility depending on temperature. From Hall data, the mobility was likely to be decreased by impurity scattering in the temperature range 30 K to 100 K and by lattice scattering in the temperature range 100 K to 293 K. The temperature dependence of the energy band gap of the $CaAl_2Se_4$: Co obtained from the absorption spectra was well described by the Varshni's relation, $E_g(T)=3.8239eV-(4.9823{\times}10^{-3}eV/K)T_2/(T+559K)$. The open-circuit voltage, short current density, fill factor, and conversion efficiency of $p-Si/p-CaAl_2Se_4$: Co heterojunction solar cells under $80mW/cm^2$ illumination were found to be 0.42 V, $25.3mA/cm^2$, 0.75 and 9.96%, respectively.

• Steel and Composite Structures
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• 제18권1호
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• pp.1-28
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• 2015

In this paper, the dynamic response of functionally gradient steel (FGS) composite cylindrical panels in steady-state thermal environments subjected to impulsive loads is investigated for the first time. FGSs composed of graded ferritic and austenitic regions together with bainite and martensite intermediate layers are analyzed. Thermo-mechanical material properties of FGS composites are predicted according to the microhardness profile of FGS composites and approximated with appropriate functions. Based on the three-dimensional theory of thermo-elasticity, the governing equations of motionare derived in spatial and time domains. These equations are solved using the hybrid Fourier series expansion-Galerkin finite element method-Newmark approach for simply supported boundary conditions. The present solution is then applied to the thermo-elastic dynamic analysis of cylindrical panels with three different arrangements of material compositions of FGSs including ${\alpha}{\beta}{\gamma}M{\gamma}$, ${\alpha}{\beta}{\gamma}{\beta}{\alpha}$ and ${\gamma}{\beta}{\alpha}{\beta}{\gamma}$ composites. Benchmark results on the displacement and stress time-histories of FGS cylindrical panels in thermal environments under various pulse loads are presented and discussed in detail. Due to the absence of similar results in the specialized literature, this paper is likely to fill a gap in the state of the art of this problem, and provide pertinent results that are instrumental in the design of FGS structures under time-dependent mechanical loadings.

• 아동학회지
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• 제38권1호
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• pp.185-203
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• 2017

Objective: The present study examined the perspectives of grandparents raising their grandchildren in an attempt to better understand grandparents' child-rearing experience while providing kinship foster care to their primary-grade grandchildren. Methods: Data were collected through individual in-depth interviews with eight grandparents who have raised one or two primary-grade (ages 8-10) grandchildren using a qualitative approach. Results: First, the participants viewed the reason for their kinship foster care as a failure for caring for their own children and accepted the present grandparent-care provision as their responsibility. Second, the participants communicated constant struggles with their own health and grandchild-care as well as positive/negative emotions associated with the care provision. Third, most of the participants did not fully understand the developmental needs of their primary-grade grandchildren. Fourth, the participants articulated concerns for their primary-grade grandchildren's learning, peer interactions, school adjustment, and extra-curricular activities. Lastly, the participants all agreed on hoping to raise grandchildren with good personality traits as members of a society and to have them fill the gap from the loss of their parents. Conclusion: Although most participants accepted the current circumstances as their obligation, they still noted difficulties in child-care provision. Given the developmental needs of grandchildren and the resource needs of grandparents, proper and continuous intervention approaches should be developed/provided.

• 한국산업정보학회논문지
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• 제20권2호
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• pp.85-96
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• 2015

외모와 신체에 대한 관심 증가로 인한 관련 산업들의 폭발적인 성장에도 불구하고 기존 연구들은 신체 존중감과 소비자의 구매의도 사이의 관계에 대한 일관적 결론에 도달하지 못하고 있다. 본 연구에서는 온라인 패션제품을 대상으로 신체 존중감과 소비자 구매의도 사이의 관계를 검토하고 이들 관계에서 존재하는 자기 감시성의 조절적 역할에 대해 살펴보았다. 172명의 소비자를 대상으로 위계적 조절 회귀분석을 실시한 결과, 신체 존중감은 온라인 패션상품에 대한 소비자의 구매의도 형성에 부정적 영향을 미치는 것으로 나타났으며, 자기 감시성은 신체 존중감과 온라인 패션제품에 대한 소비자의 구매의도와의 관계에서 긍정적인 조절 역할을 하는 것으로 나타났다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2009년 춘계학술대회논문집
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• pp.19-19
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• 2009

Dynamic Stall is a flow phenomenon which occurs on the retreating side of helicopter rotor blades during forward flight. It also occurs on blades of stall regulated wind turbines under yawing conditions as well as during gust loads. Time scales occurring during this process are comparable on both helicopter and wind turbine blades. Dynamic Stall limits the speed of the helicopter and its manoeuvrability and limits the amount of power production of wind turbines. Extensive numerical as well as experimental investigations have been carried out recently to get detailed insight into the very complex flow structures of the Dynamic Stall process. Numerical codes have to be based on the full equations, i.e. the Navier-Stokes equations to cover the scope of the problems involved: Time dependent flow, unsteady flow separation, vortex development and shedding, compressibility effects, turbulence, transition and 3D-effects, etc. have to be taken into account. In addition to the numerical treatment of the Dynamic Stall problem suitable wind tunnel experiments are inevitable. Comparisons of experimental data with calculated results show us the state of the art and validity of the CFD-codes and the necessity to further improve calculation procedures. In the present paper the phenomenon of Dynamic Stall will be discussed first. This discussion is followed by comparisons of some recently obtained experimental and numerical results for an oscillating helicopter airfoil under Dynamic Stall conditions. From the knowledge base of the Dynamic Stall Problems, the next step can be envisaged: to control Dynamic Stall. The present discussion will address two different Dynamic Stall control methodologies: the Nose-Droop concept and the application of Leading Edge Vortex Generators (LEVoG's) as examples of active and passive control devices. It will be shown that experimental results are available but CFD-data are only of limited comparison. A lot of future work has to be done in CFD-code development to fill this gap. Here mainly 3D-effects as well as improvements of both turbulence and transition modelling are of major concern.

• Journal of Welding and Joining
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• 제33권2호
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• pp.14-17
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• 2015

Cleaning effect is well known mechanism of oxide layer removal in DCEP polarity. It is also known that DCEN has higher heat input efficiency than DCEP in GTAW process. Based on these two renowned arc theories, conventional variable polarity arc for aluminum welding was set up to have minimum DCEP and maximum DCEN duty ratio to achieve the highest heat input efficiency and weldability increase. However, recent several variable polarity GTA research papers reported unexpected result of proportional relationship between DCEP duty ratio and heat input. The authors also observed the same result then suggested combination of tunneling effect and random walk of cathode spot to fill up the gap between experiment and conventional arc theory. In this research, suggested combinational work of tunneling effect and rapid cathode spot changing is applied to another unexpected phenomena of variable polarity aluminum arc welding. From previous research, it is reported that wider oxide removal range, narrower bead width and shallower penetration depth are observed in thin oxide layered aluminum compared to the case of thick oxide. This result was reported for the first time and it was hard to explain the reason at that time therefore the inference by the authors was hardly acceptable. However, the suggested combinational theory successfully explains the result of the previous report in logical way.

• 한국멀티미디어학회논문지
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• 제11권3호
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• pp.373-385
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• 2008

컴퓨터에서 포인팅 입력장치로써 마우스가 소개된 후로 그 발전 속도는 매우 느렸었다. 스타일러스나 터치스크린과 같은 몇 가지의 대안이 제시되긴 하였으나, 이러한 방법들은 모두 사용자가 컴퓨터와 가까운 영역에서 사용하도록 설계되었다. 특히 프레젠테이션과 같은 특별한 상황에서 사용자가 원거리로부터 인터랙션을 명령할 경우 다양한 인터랙션에 대한 부가적인 기능이 요구된다. 따라서 본 논문에서는, 영상처리를 기반으로, 경제적이면서도 어디서나 쉽게 구입이 가능한 레이저 포인터만을 이용하여 컴퓨터로부터 멀리 떨어진 위치에서도 사용자가 마우스와 같은 인터랙션이 가능한 장비를 제안한다. 또한, 평면 스크린에서 뿐만 아니라, 가상현실 및 3차원 입체영상 구성을 위하여 오늘날 많이 사용되어지고 있는 타원형이나 휨이 있는 스크린에서도 자동으로 보정이 가능한 좌표 매핑 방법을 제안하고자 한다.

• 정보처리학회논문지B
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• 제15B권2호
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• pp.147-158
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• 2008

본 논문에서는 인과관계 지식의 표현과 추론에 가장 대표적으로 사용되는 퍼지인식도(FCM, Fuzzy Cognitive Map)와 베이지안 신뢰 네트워크(BBN, Bayesian Belief Network)를 구조적으로 분석한다. 퍼지인식도와 베이지안 신뢰 네트워크는 의사 결정을 지원하는데 중요한 인과관계 지식을 표현하고 추론하는데 사용되는 가장 대표적인 프레임워크이지만 인과관계 지식응용 영역에서 두 프레임워크의 역할에 대한 구조적 비교 연구는 이루어지지 않고 있다. 본 논문에서는 두 프레임워크의 구조적 비교를 통해 퍼지인식도와 베이지안 신뢰 네트워크의 중요한 특징들을 추출하고, 이를 통해 인과 지식 공학에서 어떻게 퍼지 인식도와 베이지안 신뢰 네트워크가 이용되어야 하는지를 보인다. 인과관계 지식의 표현과 추론의 과정을 평가하는데 비교 평가를 위한 항목으로서 본 논문에서는 사용성, 표현력, 추론능력, 정형화와 완결성이 사용되었다.

• 벤처창업연구
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• 제9권6호
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• pp.101-108
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• 2014

창업은 일자리 창출과 신성장 동력 발굴의 적극적인 대안으로 인식되어 왔으며 창업투자회사는 이러한 활동에 주요한 역할을 담당할 것으로 기대된다. 그럼에도 불구하고 창업투자회사의 활동과 창업 활동 간의 상관관계에 대한 학계의 실증적 분석은 부족한 실태다. 1998년부터 2014년까지의 시계열 데이터를 분석한 결과 본 연구는 창업투자회사가 벤처 기업 창업을 양적으로 견인한 인과성이 있음을 밝혔다. 또한 벤처 기업의 창업이 청년 실업 문제를 단기간에 해소하기에는 부족하다는 것과 산업별 벤처 기업과 청년 실업 간의 관계가 다르다는 점도 발견했다. 본 연구는 창업투자활동과 벤처 창업 간의 상관성을 시계열적으로 고려하고 인과분석 시도함으로써 창업투자회사 육성에 관련된 연구와 전략 개발 그리고 정책 수립에 시사점을 준다.