• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2009년도 춘계학술대회 논문집
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• pp.138-138
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• 2009

Recently, thin-film solar cells of Cu(In,Ga)$Se_2$(CIGS) have reached a high level of performance, which has resulted in a 19.9%-efficient device. These conventional devices were typically fabricated using chemical bath deposited CdS buffer layer between the CIGS absorber layer and ZnO window layer. However, the short wavelength response of CIGS solar cell is limited by narrow CdS band gap of about 2.42 eV. Taking into consideration the environmental aspect, the toxic Cd element should be replaced by a different material. It is why during last decades many efforts have been provided to achieve high efficiency Cd-free CIGS solar cells. In order to alternate CdS buffer layer, ZnS buffer layer is grown by using chemical bath deposition(CBD) technique. The thickness and chemical composition of ZnS buffer layer can be conveniently by varying the CBD processing parameters. The processing parameters were optimized to match band gap of ZnS films to the solar spectrum and exclude the creation of morphology defects. Optimized ZnS buffer layer showed higher optical transmittance than conventional thick-CdS buffer layer at the short wavelength below ~520 nm. Then, chemically deposited ZnS buffer layer was applied to CIGS solar cell as a alternative for the standard CdS/CIGS device configuration. This CIGS solar cells were characterized by current-voltage and quantum efficiency measurement.

• 한국신재생에너지학회:학술대회논문집
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• 한국신재생에너지학회 2011년도 춘계학술대회 초록집
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• pp.106.1-106.1
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• 2011

The Cu(In,Ga)Se2 (CIGS) thin film solar cells have been achieved until almost 20% efficiency by NREL. These solar cells include chemically deposited CdS as buffer layer between CIGS absorber layer and ZnO window layer. Although CIGS solar cells with CdS buffer layer show excellent performance, the short wavelength response of CIGS solar cell is limited by narrow CdS band gap of about 2.42 eV. Taking into consideration the environmental aspect, the toxic Cd element should be replaced by a different material. Among Cd-free candidate materials, the CIGS thin film solar cells with ZnS buffer layer seem to be promising with 17.2%(module by showa shell K.K.), 18.6%(small area by NREL). However, ZnS/CIGS solar cells still show lower performance than CdS/CIGS solar cells. There are several reported reasons to reduce the efficiency of ZnS/CIGS solar cells. Nakada reported ZnS thin film had many defects such as stacking faults, pin-holes, so that crytallinity of ZnS thin film is poor, compared to CdS thin film. Additionally, it was known that the hetero-interface between ZnS and CIGS layer made unfavorable band alignment. The unfavorable band alignment hinders electron transport at the heteo-interface. In this study, we focused on growing defect-free ZnS thin film and for favorable band alignment of ZnS/CIGS, bandgap of ZnS and CIGS, valece band structure of ZnS/CIGS were modified. Finally, we verified the photovoltaic properties of ZnS/CIGS solar cells.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 춘계학술대회 논문집
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• pp.466-471
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• 2014

The interior vehicle noise due to the exterior aerodynamic field is an important topic in the acoustic design of a car. The air flow detached from the A-pillar and impacting the side windows are of particular interest as they are located close to the driver / passenger and provides a lower insulation index than the trimmed car body parts. This paper presents a numerical analysis method for a simplified vehicle model. The internal air cavity including trim component are included in the simulation. The car body includes the windshield and two side windows. The body is made of aluminum and trimmed with porous layers. The methodology proposed in this paper relies on two steps: the first step involves the computation of the exterior flow and turbulence induced non-linear acoustic field using PowerFlow. The second step consists in the computation of the vibro-acoustic transmission through the window using the finite element vibro-acoustic solver Actran. Additionally in order to validate the numerical process, an experimental set-up has been created based on the simplified vehicle. The vibration of the windshield and windows, the total wind noise level results and the relative contributions of the different windows are then presented and compared to measurements. The influence of the flow yaw angle (different wind orientation) is also assessed.

• 한국압력기기공학회 논문집
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• 제10권1호
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• pp.90-95
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• 2014

Local wall thinning is a point of concern in almost all steel structures such as pipe lines covered with a thermal insulator made up of materials with low thermal conductivity(fiberglass or mineral wool); hence, Non Destructive Technique(NDT) methods that are capable of detecting the wall thinning and defects without removing the insulation are necessary. In this study we developed a Pulsed Eddy Current(PEC) system to detect the wall thinning of Ferro magnetic steel pipes covered with fiber glass thermal insulator and shielded with Aluminum plate. The developed system is capable of detecting the wall thickness change through an insulation of thickness 10cm and 0.4mm aluminum shielding. In order to confirm the thickness change due to wall thinning, two different sensors, a hall sensor and coil sensor were used as a detecting element. In both cases, the results show a very good change corresponding to the thickness change of the test specimen. During these experiments a carbon steel tube of diameter 210mm and a length of 620mm, which is covered with insulator of 95mm thickness was used. To simulate the wall thinning, the thickness of the tube is changed for a specified length such as 2.5mm, 5mm and 8 mm from the inner surface of the tube. A 0.4mm thick Aluminum plate was covered on the Test specimen to simulate the shielding of the insulated pipelines. For both hall sensor and coil detection methods Fast Fourier transform(FFT) was calculated using window approach and the results for the test specimen without Aluminum shielding were summarized which shows a clear identification of thickness change in the test specimen by comparing the magnitude spectra. The PEC system can detect the wall thinning under the 95 mm thickness insulation and 0.4 mm Al shielding, and the output signal showed linear relation with tube wall thickness.

• 한국실내디자인학회논문집
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• 제17권1호
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• pp.30-38
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• 2008

Borrowed landscape is an Oriental gardening method to draw inside external natural landscape, and borrowed landscape of Japan has a different characteristic from that of Korea or China nature is manipulated and re-interpreted by human will in the course of applying it to architectural space. In other words, not the original scenery, but manipulated one appears which is cut, reduced, or deleted by architectural elements such as wall, window, or fence. Therefore, this study examined how architectural structure of Ando Tadao symbolizing modernist architecture understood and adopted Japanese traditional views on nature, that is, borrowed landscape. To this end, on the basis of the understanding on 'polymerization of abstraction and form' he mentioned, his geometric architectural principles are discussed, since this serves to be an important beginning of architectural concretization by the concept of 'form' experienced and perceived by human being through geometric means called architecture 'abstraction.' The findings of this study are as follows: first, it was found that Ando Tadao generates borrowed landscape effects by polymerizing and manipulating his simple and geometric structures with each other and thereby editing natural scenery, while Japanese traditional borrowed landscape introduces source scenery inside, through condensation and symbolization. Second, the results of this study revealed that his architecture functions to transcend external and internal realm of a space, which is also observed in Japanese traditional architectural borrowed landscape. Therefore, this study is considered significant in the sense that it proved that Ando Tadao's architectural language is based on borrowed landscape as a specific Japanese traditional element, going beyond the scope of previous studies focusing simply on the introduction of natural elements.

• Structural Engineering and Mechanics
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• 제75권4호
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• pp.435-444
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• 2020

Ultrasonic guided wave testing is a very promising non-destructive testing method for rails, which is of great significance for ensuring the safe operation of railways. On the basis of the semi-analytical finite element (SAFE) method, a analytical model of 59R2 grooved rail was proposed, which is commonly used in the ballastless track of modern tram. The dispersion curves of ultrasonic guided waves in free rail and supported rail were obtained. Sensitivity analysis was then undertaken to evaluate the effect of rail elastic modulus on the phase velocity and group velocity dispersion curves of ultrasonic guided waves. The optimal guided wave mode, optimal excitation point and excitation direction suitable for detecting rail integrity were identified by analyzing the frequency, number of modes, and mode shapes. A sinusoidal signal modulated by a Hanning window with a center frequency of 25 kHz was used as the excitation source, and the propagation characteristics of high-frequency ultrasonic guided waves in the rail were obtained. The results show that the rail pad has a relatively little influence on the dispersion curves of ultrasonic guided waves in the high frequency band, and has a relatively large influence on the dispersion curves of ultrasonic guided waves in the low frequency band below 4 kHz. The rail elastic modulus has significant influence on the phase velocity in the high frequency band, while the group velocity is greatly affected by the rail elastic modulus in the low frequency band.

• 만화애니메이션 연구
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• 통권34호
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• pp.367-386
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• 2014

과학기술의 눈부신 발전은 디지털 기기의 콘텐츠 및 디자인의 다양성과 변화로 이어졌으며 여기에서 파생되는 UI, UX, GUI 디자인은 세분화된 디지털 디자인의 창조 및 발전으로 거듭났다. 이런 다양한 디지털 매체의 디자인은 도스 이후의 윈도우의 시작과 함께 생겨났으며 이는 마우스라는 혁신적인 도구의 개발로 인해 가능했다. 이러한 환경 안의 디지털 매체 디자인의 중심에는 모든 콘텐츠 및 버튼, 입구를 상징하는 아이콘이 있으며 모바일, 앱, 윈도우환경에서 필수요소로 자리 잡고 있다, 이러한 아이콘은 윈도우 초기 시절부터 다양한 발전을 거듭하였으며 이는 디지털 과학기술의 발전과 함께 하였다. 디자인 트렌드분석은 스큐어모피즘에서 부터 플랫된 형태 그리고 미니멀리즘으로 되돌아오기까지의 아이콘의 디자인의 변천을 분석한다. 분석 범위는 트렌드와 기기의 성능에 민감한 모바일을 대상으로 분석하며 Kress's grammar of visual design의 분석틀을 기본으로 한다. 특히 iPhone의 IOS7디자인이 애플의 대표 디자인 트렌드인 스큐어모피즘을 접고 미니멀리즘, 플렛 디자인을 채택해 큰 변화를 겪는 현 시점에서 모바일 앱시장의 GUI 디자인 기초 동향 파악 자료로 활용되는데 도움이 되고자 한다.

• 한국정보처리학회논문지
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• 제4권12호
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• pp.2985-2995
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• 1997

본 논문에서 제안하는 원격교육 시스템은 정보 통신 기술과 멀티미디어 기술을 이용해서 사이버 스페이스상에서 열린 교육을 위한 교육자와 피교육자간의 상호 참여를 통한 동기 및 비동기의 학습이 모두 가능하도록 개발된 원격 교육 시스템이다. 특히 기존의 원격 교육 시스템이 갖는 생소함과 불편함을 가능한 느끼지 않도록 개발하였고, 면대면 효과를 최대로 지원하는 멀티미디어 기술상의 상호작용이 가능한 실시간 동기모드의 학습모드와 사용자 위주의 비동기 모드의 자율학습을 진행하다가 필요한 자료의 지원을 받아 원하는 선생님의 학습자료를 다운로딩 할 수 있고, 선생님과의 동기 학습 모드 변환이 가능한 시스템이다. 본 시스템은 응용 공유기술, 화이트보드, 다양한 비디오 윈도우 표시, 비디오, 사용자 인터페이스를 지원하고 있으며, 또한 세션관리, 통신제어, 각 미디어 제어의 제어 기술이 지원되고 있다．

• 한국재료학회:학술대회논문집
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• 한국재료학회 2010년도 춘계학술발표대회
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• pp.35.1-35.1
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• 2010

The Cu(In,Ga)Se2(CIGS) thin film solar cells have been achieved until almost 20% efficiency by NREL. These solar cells include chemically deposited CdS as buffer layer between CIGS absorber layer and ZnO window layer. Although CIGS solar cells with CdS buffer layer show excellent performance, many groups made hard efforts to overcome its disadvantages in terms of high absorption of short wavelength, Cd hazardous element. Among Cd-free candidate materials, the CIGS thin film solar cells with Zn compound buffer layer seem to be promising with 15.2%(module by showa shell K.K.), 18.6%(small area by NREL). However, few groups were successful to report high-efficiency CIGS solar cells with Zn compound buffer layer, compared to be known how to fabricate these solar cells. Each group's chemical bah deposition (CBD) condition is seriously different. It may mean that it is not fully understood to grow high quality Zn compound thin film on the CIGS using CBD. In this study, we focused to clarify growth mechanism of chemically deposited Zn compound thin film on the CIGS, especially. Additionally, we tried to characterize junction properties with unfavorable issues, that is, slow growth rate, imperfect film coverage and minimize these issues. Early works reported that film deposition rate increased with reagent concentration and film covered whole rough CIGS surface. But they did not mention well how film growth of zinc compound evolves homogeneously or heterogeneously and what kinds of defects exist within film that can cause low solar performance. We observed sufficient correlation between growth quality and concentration of NH3 as complex agent. When NH3 concentration increased, thickness of zinc compound increased with dominant heterogeneous growth for high quality film. But the large amounts of NH3 in the solution made many particles of zinc hydroxide due to hydroxide ions. The zinc hydroxides bonded weakly to the CIGS surface have been removed at rinsing after CBD.

• 정보처리학회논문지A
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• 제8A권3호
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• pp.269-278
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• 2001

자동배선 시스템의 배선영역 모델링 방법은 그리드와 논 그리드 방식을 사용하고 있다. 그리드 방식은 PCB상에 전기적, 물리적 요소들이 적다 할지라도 보드와 그리드의 크기에 제약을 받기 때문에 자동배선 속도를 감소시키는 단점을 가지고 있다. 따라서 메모리 용량을 증가 시키게 된다. 논 그리드 방식(Shape based type)은 영역처리 방식을 사용하며, 배선영역에서 그리드 방식보다 44.2% 메모리 감소효과가 있다. 따라서 Via 수는 55.5%의 감소 효곽가 있으며, 총 배선 시간도 기존 PCB시스템보다 83.3% 향상되었다. 본 논문에서는 단일 원점에서 여러 목적지에 가장 빠르게 도달 할 수 있고 최단 경로 문제를 해결하는 auction 알고리즘을 적용한 Shape based 방식에 의하여 메모리 낭비 없이 빠른 속도로 자동 배선할 수 있는 PCB 자동 배선 시스템을 개발하였다. 또한 본 시스템은 IBM Pentium 컴퓨터 Windows 환경에서 Visual C++언어로 개발하였으며 다른 PC 와도 호환성을 가질수 있도록 개발 하였다.