• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.40 no.6
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• pp.467-474
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• 2012

UAVs for reconnaissance and intelligence operations require long endurance capability, which demands high efficiency of the propulsion system. The distributed propulsion system(DPS) generates the thrust by replacing a large propulsion system with a number of small propulsion systems. A DPS distributed along the wing span can produce gains in propulsion efficiency by reducing ejection velocity. Also, the ingestion of boundary layers through the distributed DPS inlet and ejecting flow from the outlet can improve the lift to drag ratio of the vehicle. This study investigates the effects of locations and size of the inlet and outlet of the DPS on the blended-wing-body design based on Eppler 337 airfoil, with a CFD tool. The fans in the DPS are modeled as actuator disks for computational efficiency. The best location and aspect ratio of the inlet and outlet are found from lift-to-drag ratio and pitching moment considerations.

• The Journal of the Convergence on Culture Technology
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• v.8 no.2
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• pp.337-342
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• 2022

Although printing technology has recently been widely used in IT fields including displays and fuel cells, residual and thermal stress are generated by a manufacturing process of stacking the layers of the print head and result in the substrate deformation and nozzle plate crack, which may cause ink leaks or not be ejected onto a desired region. Therefore, in this paper, we propose a new design of thermal inkjet print head with a robust and reliable structure. Diverse types of inkjet print head such as a rib, pillar, support wall and individual feed hole are designed to reduce the deformation of the substrate and nozzle plate, and their feasibility is numerically investigated through FEA analysis. The numerical results show that the maximum stress and deformation of proposed print head dramatically drops to at least 40~50%, and it is confirmed that there is no nozzle plate cracks and ink leakage through the fabrication of pillar and support wall typed print head. Therefore, it is expected that the proposed head shape can be applied not only to ink ejection in the normal direction, but also to large-area printing technology.

• Applied Chemistry for Engineering
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• v.33 no.1
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• pp.96-102
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• 2022

Reactants of PEMFC are hydrogen and oxygen in gas phases and fuel cell overpotential could be reduced when reactants are smoothly transported. Numerous studies to modify cathode flow field design have been conducted because oxygen mass transfer in high current density region is dominant voltage loss factor. Among those cathode flow field designs, a block in flow field is used to forced supply reactant gas to porous gas diffusion layer. In this study, the block was installed on a simple fuel cell model. Using computational fluid dynamics (CFD), effects of forced convection due to blocks on a polarization curve and local current density contour were studied when different air flow rates were supplied. The high current density could be achieved even with low air supply rate due to forced convection to a gas diffusion layer and also with multiple blocks in series compared to a single block due to an increase of forced convection effect.

• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.30 no.2
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• pp.143-152
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• 2012

It is well-known that image matching is necessary for automatic generation of 3D data such as digital surface data from aerial images. Recently developed aerial digital cameras allow to capture multi-strip images with higher overlaps and less occluded areas than conventional analogue cameras and that much of researches on multi-image matching have been performed, particularly effective methods of measuring a similarity among multi-images using point features as well as linear features. This research aims to investigate similarity measuring methods such as SSD and SNCC incorporated into a area based multi-image matching method based on vertical line locus. In doing this, different similarity measuring entities such as grey value, grey value gradient, and average of grey value and its gradient are implemented and analyzed. Further, both dynamic and pre-fixed adaptive-window size are tested and analyzed in their behaviors in measuring similarity among multi-images. The aerial images used in the experiments were taken by a DMC aerial frame camera in three strips. The over-lap and side-lap are about 80% and 60%, respectively. In the experiment, it was found that the SNCC as similarity measuring method, the average of grey value and its gradient as similarity measuring entity, and dynamic adaptive-window size can be best fit to measuring area-based similarity in area based multi-image matching method based on vertical line locus.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.5
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• pp.619-628
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• 2010

Shape Memory Alloy (SMA) has recently received attention in developing implantable surgical equipments and it is expected to lead the future medical device market by adequately imitating surgeons' flexible and delicate hand movement. However, SMA actuators have not been used widely because of their nonlinear behavior called hysteresis, which makes their control difficult. Hence, we propose a parameter, $t_1$, which is necessary for temperature control, by analyzing the open-loop step response between current and temperature and by comparing it with the values of linear differential equations. $t_1$ is a pole of the transfer function in the invariant linear model in which the input and output are current and temperature, respectively; hence, $t_1$ is found to be related to the state variable used for temperature control. When considering the parameter under heat treatment conditions, $T_{max}$ was found to assume the lowest value, and $t_1$ was irrelevant to the heat treatment.

• Proceedings of the Korean Radioactive Waste Society Conference
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• 2004.06a
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• pp.353-354
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• 2004

사용후 핵연료의 조성을 분석하거나 또는 반사전자상과 2차 전자상 등으로 시료를 관찰하기 위해서는 핫셀(Hot cell)에 증착기(coater)를 설치하여 시료표면을 전도성 물질인 탄소 등으로 증착시켜야 한다. 그러나 원격조정기를(manipulator)를 이용하여 수행되는 핫셀에서의 증착작업은 사용후 핵연료 시험의 선진분석기술을 갖고 있는 원자력 선진국에서도 핫셀내에 설치되어 있는 증착기의 탄소봉을 교체하는 작업과 진공장치의 성능 유지가 까다로워 시료표면에 균질하게 전도성 물질을 증착시키는 작업에 많은 어려움을 겪고 있다. 본 연구는 통상적으로 이용되는 증착기를 사용하지 않고 Silver Paint를 사용하여 사용후 핵연료를 분석할 수 있는 새로운 방법에 대한 연구를 수행하였다. 산화물 핵연료는 전기전도도가 매우 낮아($3{\times}10^{-1}~4{\times}10^{-8}/ohm{\cdot}cm$)입사된 전자의 이동이 원활하지 못해 일어나는 들뜸(Charging)현상이 발생한다. 그러나 Silver Paint 에 사용후 핵연료를 접착하면 모세관(capillary)현상에 의해 시료 주위와 핵연료의 결정립계로 Silver가 스며들어 입사된 전자의 이동이 원활해져 전도성이 극히 낮은 시료의 분석이 가능하게 된다. 본 시험에 사용된 EPMA는 (Electron Probe Micro Analyzer, SX-50R, CAMECA, Paris, France) 고 방사능을 띤 조사 핵연료의 시험을 수행할 수 있도록 기기의 적절한 부위에 납과 텅스텐으로 차폐되어 시편의 방사능 세기가 $3{\times}10^{10}Bq$까지 시험 가능한 기기이다. 그림 1은 JAERI 에 설치 운영중인 증착기 설비 사진이다. 그림에서 핫셀에 설치된 증착기의 진공을 유지하기 위해 핫셀 벽을 관통하여 증착기 본체까지 연결된 배출관의 형상과 복잡한 주변장치들을 볼 수 있다. 그림 2는 비조사 핵연료 시편을 Silver Pain떼 접착한 사진이다. 그림은 시료주위와 시료 표면까지 Silver Paint가 도포된 모습을 보여주고 있다. 상용발전소에서 연소도가 50,000 Mwd/tU인 사용후 핵연료를 상기와 같은 방법으로 만든 시편의 표면을 관찰한 사진을 그림 3~8에 나타내었다. 그림 3은 핵연료 중앙부위의 결정립을 나타낸 그림이다. Silver Paint만으로 접착한 시료의 표면관찰 및 정량분석이 그림에서 보듯이 가능함을 확인하였다. 그림 4는 사용후 핵연료시료를 중앙부위에서 가장자리까지를 다섯 부위로 나누어 그 중 중앙부위(1/5) 지점의 입계 및 형상을 관찰한 사진이다. 결정립의 크기가 다른 부위보다 상대적으로 크고, 결정립에 생성된 기공이 발달되어 있음을 볼 수 있다. 그림 5와 6과 7은 중심부위와 rim부위 사이 지점을 관찰한 사진으로서 결정립과 기공의 분포가 비슷한 형상을 나타내고 있음을 관찰할 수 있었다. 그림 8은 rim 부위 사진으로 전형적인 rim 영역 현상을 관찰할 수 있었다. 표 1은 그림 2와 같이 비조사 산화물 핵연료를 Silver Paint로 접착한 시편을 정량 분석한 결과이다. 시편의 조성은 33.6 at% U, 66.4 at% O의 결과를 얻었다. 산화물 핵연료의 표면 관찰 및 정량 분석 시험시 시편 표면을 전도성 물질로 증착시키지 않고, Silver Paint 에 시편을 접착하는 방법으로도 만족한 시험 결과를 얻을 수 있었다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.31 no.4
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• pp.423-434
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• 1995

It was used boundary element method(BEM) and analysed axisymmetric problem to solve hydraulic cylinder for large vessel acting uniform internal pressure(25N/m super(2)) within elastic limit. This paper was utilized the carbon steel tubes for machine structural purposed model, inner radius was 150mm and outer radius was 250mm, axial length was semi-infinite and the isoparametric element was used. The important results obtained in this study were summarized as follows. Radial, tangential and shearing stress occured the maximum stresses(48, -20 and 34MPa) at the inner radius and the minimum stresses(32, -4 and 18MPa) at the outer radius of the hydraulic cylinder for large vessel. But negative signs have meaning compressive stress and stress diminution ratio was about 0.15MPa/mm. The use of isoparametric element raised accuracy and the increment of input data lessened the error in internal point but computer run-time was increased. The double node was improved the internal solutions to settle discontinuity at corner and the double exponential formula lessened error of stress value at boundary neighborhood. And then coincidence between the analytical and exact results is found to be fairly good, showing that the proposed analytical by BEM is reliable.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.520-525
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• 2019

Mines are an important infrastructure for securing resources, but safety problems can arise in the course of operation. Recently, the mining process is very complicated due to the large scale and mechanization. Therefore, it is necessary to construct accurate geospatial information on mine for systematic and safe mine operation. The geospatial information construction using the existing total station has a disadvantage that a lot of work time is required because the target must be collimated and measured. In this study, the data of the mines were acquired with the total station and the 3D laser scanner, and the mine spatial information was constructed by using the shape based registration method. By using the static scanner data of some area applying the reference point surveying result of the total station, it was possible to construct the accurate result on the wide area acquired by the mobile scanner effectively. Also, the accuracy of the constructed geospatial information was evaluated and the deviation of mean 0.083m was shown. Point cloud products constructed through the research can contribute to the efficiency improvement of mine management by enabling quantitative analysis such as visualization of mine shape, distance, area and slope, and automation of drawing creation for cross section shape.

• Cartoon and Animation Studies
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• s.51
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• pp.59-82
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• 2018

This study notes that the concept of painterliness, as defined by Heinrich $W{\ddot{o}}lfflin$, can apply to represent features in $Micha{\ddot{e}}l$, Dudok de Wit's animated short film Father and Daughter. It intends to examine the animated film's visual representation and narrative features in terms of painterliness. Comparing the Renaissance art style of the 16th century to the Baroque art style of the 17th century, $W{\ddot{o}}lfflin$ conceptualized the features of painterly style. In respect to this animated film, the images drawn by drawing tools are represented are represented by irregular and ambiguous shapes and meet $W{\ddot{o}}lfflin^{\prime}s$ conditions for painterly representation. Such a representation method in this animated film effectively functions as a double entendre or ambiguous narrative, while playing a key role in representing lyricism. In this animated film, painterliness contrasts with clarity, which commercial animated films provide, and plays a critical role in the representation methods utilized by auteurist animation directors. Painterliness in animated films is an element that should be highlighted, especially in the contemporary world where the forms of representation are becoming increasingly monolithic due to digital techniques. Continued research is greatly needed on this subject matter. Based on Father and Daughter, this study aims to examine the method of painterly representation that can be used in animation films, to explore its meaning and to underscore the importance of diversity in the forms of representation in animated films.

• Proceedings of the Korea Society of Mathematical Education Conference
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• 2006.04a
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• pp.25-37
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• 2006

영재를 위한 수학교육은 우리의 당면과제 중 하나이다. 능력 있는 학생들의 학습이 속진에 한정되는 것 보다는 심화자료 및 수학적 소프트웨어와 함께 하는 것이 더 의미 있을 것으로 기대된다. 본 연구는 스프레트쉬트를 사용한 수학적 아이디어의 탐구에 관한 것이다. 다음에 대해 논의하기로 하겠다. i) 스프레드쉬트는 비전통적이면서도 이용이 용이하며, 수학적 통찰을 위한 매개물이다. ii) 풍부하고, 흥미릅고, 가치있는 수학적 주제에 대해 스프레드쉬트를 이용할 수 있다. iii) 스프레드쉬트를 사용하여 학생들이 수학적 아이디어에 대한 흥미를 고취시킬 수 있다. iv) 스프레드쉬트는 학생들에게 그들의 창의적인 시각화 기술을 공개할 기회를 줌으로써 수학에 대한 폭넓은 도식적 이해를 제공한다. v) animation을 포함한 스프레드쉬트 도식들의 적절한 사용은 유익하면서도 흥미롭다. vi) 학생들은 일상생활에 나타나는 수학의 흥미로움을 발견할 것이다. vii) 교사는 지금의 지도방식에 스프레드쉬트를 통합할 수 있다. 특히 스프레드쉬트는 다음과 같은 면모도 가지고 있다. i) 창의적인 수학적 스프레드쉬트 모델들의 실제 과정들이 그 자체로써 수학적 개념발달에 이용될수 있다. ii) 스프레드쉬트 모델은 심화된 주제의 탐색을 위한 의미 있는 탐구과제를 제공한다. iii) 스프레드쉬트는 현장에서 사용되는 실제적 수학 도구이다. - 과학자나 공학도들의 사용도 증가되고 있다. 이것의 사용은 학생들이 현장에서 사용할 기술을 취득하게 할 수 있고, 같은 컴퓨터의 소프트웨어를 사용하는 가족의 대화 수단이 되기도 한다. 본 연구에서 우리는 스프레드쉬트의 4가지 실증적 예를 들어 보겠다. 또한 다른 영역에서 발전된 스프레드쉬트 모델의 몇 가지 도식적 산출물도 포함 할 것이다. 우리는 가장 대중적인 스프레드 쉬트인 Microsoft Excel 프로그램을 사용하였다. Excel의 수행과 Excel 연산의 설명을 담은 CD와 함께 다양한 사례들에 대한 논의는 (8)을 참고하기 바란다. 본고에서는 graphic animation 기술, 스크롤바의 사용을 간단하게 개괄하겠다. '동적형상들(movies)'를 만들 수 있는 간단한 매크로의 사용 등의 내용들은 각 자료를 사용할 수 있는 Excel 파일의 예와 함께 [1]과 [8]에 설명하였었다. 많은 인쇄물과 on-line 참고문헌, 매체자료들도 함께 제공하였다.