• Journal of the Korea institute for structural maintenance and inspection
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• v.26 no.1
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• pp.1-9
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• 2022

De -icing salts have been used commonly in areas where snow or ice is a seasonal safety hazard for roadway, however, the salts is one of main causes on serious deterioration of road infrastructures in crowded urban city like Seoul. In order to establish maintenance strategy of road infrastructures under de-icing salts laden environment, it is necessary to examine environmental characteristics and its response to the existing facilities. The purpose of this study is to evaluate the deterioration environment of road infrastructures. Additional purpose is to develop a design model and details for durability design of infrastructures under de-icing salts laden environment, considering mainly a build-up rate of surface chlorides. Concentration of external chloride solution and surface chloride content were calculated at the level of average de-icing salts for 5 years, ratio of auxiliary road of 17.5 to 30%, and effective exposure area to snow 50 to 80%. The chloride build-up rate was 0.073 ~ 0.077% / year and the maximum surface chloride content was calculated to be 2.2 ~ 2.31% by concrete wt. This study is expected to be used for establishing integrated strategy of road infrastructures, such as predicting chloride profiles or degree of chemical corrosion to exposure concrete.

• Journal of Aerospace System Engineering
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• v.17 no.4
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• pp.18-27
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• 2023

In this paper, the structural-thermal-optical performance analysis of the mirror was performed by setting the laser heat source as the boundary condition of the thermal analysis. For the laser heat source model, the Beer-Lambert model considering semi-transparent optical material based on Gaussian beam was selected as the boundary condition, and the mechanical part was not considered, to analyze the performance of only the mirror. As a result of the thermal analysis, thermal stress and thermal deformation data due to temperature change on the surface of the mirror were obtained. The displacement data of the surface due to thermal deformation was fitted to a Zernike polynomial to calculate the optical performance, through which the performance of the mirror when a high-energy laser was incident on the mirror could be predicted.

• Journal of the Korean Society of Radiology
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• v.1 no.2
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• pp.23-30
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• 2007

This paper presents a method of generating 3-dimensional images by preprocessing 2-dimensional abdominal images obtained using CT (computed tomography) and MRI (magnetic resonance imaging) through segmentation, threshold technique, etc. and apply the method to virtual endoscopy. Three-dimensional images were visualized using indirect volume rendering, which can render at high speed using a general-purpose graphic accelerator used in personal computers. The algorithm used in the rendering is Marching Cubes, which has only a small volume of calculation. In addition, we suggested a method of producing 3-dimensional images in VRML (virtual reality modeling language) running on the Web browser without a workstation or an exclusive program. The number of nodes, the number of triangles and the size of a 3-dimensional image file from CT were 85,367, 174,150 and 10,124, respectively, and those from MRI were 34,029, 67,824 and 3,804, respectively.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.20 no.6
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• pp.101-107
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• 2020

Road surface measurement is an essential process for quantifying the degree and displacement of roughness in road surface management. For safer road surface management and quick maintenance, it is important to accurately measure the road surface while mounted on a vehicle. In this paper, we propose a sophisticated road surface measurement system that can be measured on a moving vehicle. The proposed road surface measurement system supports more accurate measurement of the road surface by using a high-performance line laser sensor. It is also possible to measure the transverse and longitudinal profile by matching the position information acquired from the RTK, and the velocity adaptive update algorithm allows a manager to monitor in a real-time manner. In order to evaluate the proposed system, the Gocator laser sensor, MRP module, and NVIDIA Xavier processor were mounted on a test mobile and tested on the road surface. Our evaluation results demonstrate that our system measures accurate profile base on the MSE. Our proposed system can be used not only for evaluating the condition of roads but also for evaluating the impact of adjacent excavation.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.133-142
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• 2006

Many methods have been tried to more correctly measure rock joint roughness. However, true roughness may be distorted and underestimated due to the sampling interval and measurement method. Thus, currently used measurement methods produce a dead zone and distort roughness profiles. The purpose of this study is to suggest new roughness measurement method by a camera-type 3D scanner as an alternative of currently used methods. First, the underestimation of artificial roughness is analyzed by using the current measurement method such as laser profilometry. Second, we replicate eight specimens from two rock joint surfaces, and digitize by a 3D scanner. Then, the roughness coefficient values obtained from eight numbers of 3D surface data and from three hundred twenty numbers of 2D profiles data are analyzed by using current and new measurement methods. The artificial simulation confirms that the sampling interval is one of main factors for the distortion of roughness and shows that inclination of waviness may not be considered any current methods. The experimental results show that the camera-type 3D scanner produces 10% larger roughness values than current methods. As the proposed new method is a fast, high precision and more accurate method for the roughness measurement, it should be a promising technique in this area.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.42 no.5
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• pp.423-429
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• 2014

Passive attitude stabilization methods using the permanent magnet combined with hysteresis damper and the gravity gradient boom have been widely used for the attitude determination and control of cube satellite, due to its advantage of system simplicity. In this paper, on-orbit thermal characteristics of the cube satellite considering the attitude profiles obtained from the above passive attitude stabilization methods have been investigated through on-orbit thermal analysis. In addition, the effectiveness of the various thermal coatings on the panel for the communication antenna installation has been verified.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.35 no.3
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• pp.325-331
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• 2011

A new method to predict the proper promotion time on the near-step-temperature test profile when heating or cooling the test-piece in a test chamber to the test temperature for environmental tests has been proposed by using the lumped analysis. For a given test condition the analysis shows the existence of a promotion time that reduces the testing time and saves energy. The theoretical results are in reasonably good agreements with experimental results for steel specimens. The suggested promotion time is approximately proportional to the mass/surface area of the test-piece for a given material.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.350.1-350.1
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• 2014

분포 브래그 반사기(distributed Bragg reflector; DBR)는 광센서, 도파로, 태양전지, 반도체 레이저 다이오드, 광검출기와 같은 고성능 광 및 광전소자 응용분야에 널리 사용되고 있다. 일반적으로, DBR은 박막의 두께를 4분의 1 파장(${\lambda}/4$)으로 가지는 서로 다른 저굴절율 물질과 고굴절율 물질을 교대로 적층 (pair)한 다중 pair로 제작되어지며, DBR의 반사 특성과 반사대역폭은 두 물질의 굴절율 차이와 pair의 수에 영향을 받는다. 그러나, 서로 다른 굴절율을 갖는 두 물질을 이용하는 DBR의 경우, 두 물질간 열팽창계수의 불일치, 접착력 문제, 높은 굴절율 차이를 갖는 물질 선택의 어려움 등 많은 문제점을 지니고 있다. 최근, 경사입사각증착법을 이용한 동일 재료(예, 인듐 주석 산화물, 게르마늄, 실리콘)기반의 DBR 제작 및 특성에 대한 연구가 보고되고 있다. 높은 입사각을 갖고 박막이 증착될 경우, 저율을 갖는 다공박막 제작이 가능하여 경사입사각증착법으로 homogeneous 물질 기반의 고반사 특성을 갖는 다중 pair의 DBR을 제작할 수 있다. 본 실험은, 갈륨비소 기판 위에 경사입사각증착법 및 전자빔증착법을 이용하여 중심파장 960 nm가 되는 이산화 티타늄 기반의 DBR을 제작하였고, 제작된 샘플의 증착된 박막의 표면 및 단면의 프로파일은 주사전자현미경을 사용하여 관찰하였으며, UV-Vis-NIR 스펙트로미터를 이용하여 반사율 특성을 조사하였다.

• Korean Journal of Optics and Photonics
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• v.27 no.2
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• pp.61-66
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• 2016

We used transmission deflectometry to measure the three-dimensional shapes of optical components, and we used the Hilbert transform to retrieve the phases from measured deformed fringe images. Deflectometry is useful for measuring large-scale samples, and specular samples. We have retrieved the phases from deformed fringe images and Hilbert-transformed images, and have used the least-squares method to find the height information. We have verified that phase retrieval using Hilbert transform is useful by computer simulation and experiment.

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.2
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• pp.138-144
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• 2023

In this study, the effect of electrochemical treatment in mitigating alkali leaching into an aquatic environment was investigated. To modify the surface of cement paste, 1000 mA/m² of the direct current was passed through anodic graphite to the external mesh for 4 weeks. Then, the cement paste specimen was exposed to still water in air-tight condition to prevent natural healing of alkali leaching in the water. For 100 days of monitoring in water, the pH value was marginally increased at the electrochemical treatment, while control specimen ranked to the even higher pH accounting for 13.2 in the pH. Moreover, after the pH monitoring, the pH profile for the paste specimen indicated that the electrochemical treatment was effective in securing the higher alkalinity of cement matrix. The water obtained from alkali leaching process, was used to ecological test for Daphnia magna. It was evident that the electrochemical treatment had minimal adverse effect on ecological impact, while control specimen mostly immobilized the standard Daphnia magna.