• Journal of Korean Association for Spatial Structures
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• v.11 no.3
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• pp.67-76
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• 2011

Column base is very important part of steel structure because it transmits load to foundation in structure. Column base which is used frame construction in the inside and outside of the country is distributed into exposed-type, concrete encased and imbeded-type. Exposed-type column base is most profitable, if consider reuse and recycle of elements first of all. In this study, we proposed a new style exposed-type column base improved in performance for construction work and mechanical performance.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.141.2-141.2
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• 2016

디스플레이, 센서 등 전자소자는 소형화 단계를 지나 인체 부착형 소자로의 발전을 요구하고 있다. 인체 부착을 위해서는 민감한 피부에 장시간 부착시 무해성과 탈부착의 자유로움이 요구되기에 기존의 화학물질을 활용한 접착 방식에서 개코도마뱀 또는 딱정벌레 발바닥에서 영감을 얻은 자연모사형 건식 접착 방식에 대한 연구가 활발하게 진행되고 있다. 폴리머를 이용하여 자연모사형 마이크로/나노구조 형성은 기계적으로 가공된 금형 몰딩과 후처리를 통한 매우 복잡한 공정이 요구된다. 본 연구에서는 이러한 복잡한 공정을 단순화하기 위해서 폴리머 소재에 플라즈마를 활용한 나노구조를 형성하는 방법을 소개하고자 하며, 건식 접착용 폴리머 소재(PMMA, PDMS)에 따른 표면구조 변화와 표면에너지 변화에 대한 연구를 수행하였다. 플라즈마 표면처리를 위해서 본 연구실에서 자체 개발한 선형이온소스를 활용하였으며 입사에너지, 노출시간, 사용가스에 따른 표면형상 변화를 주사전자현미경을 활용하여 관찰하였다. 또한 처리조건에 따른 표면에너지 변화를 확인하기 위해 물접촉각 변화를 측정하였다. PMMA는 입사에너지, 노출시간이 증가함에 따라 쉽게 나노기둥구조가 형성되었으나, 과도한 입사에너지 또는 노출시간에서는 표면구조가 에칭되면서 무너지는 것이 관찰되었다. 또한 PDMS는 동일한 조건에서 주름구조 형태를 보였으며 노출시간이 증가할수록 주름구조의 간격이 늘어남을 확인하였다. 본 연구 결과를 통해 나노 구조를 쉽게 제어할 수 있는 PMMA가 피부 부착형 접착 패치에 응용이 가능할 것으로 기대된다.

• Journal of Korean Ophthalmic Optics Society
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• v.20 no.1
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• pp.75-81
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• 2015

Purpose: The present study was conducted to investigate whether the changes in structure and activity of antioxidative enzymes, superoxide dismutase(SOD) and catalase(CAT) present in the eyes appeared when they were repeatedly exposed to UV-A, and reveal the correlation of these changes. Methods: Each enzyme solution was prepared from the standardized SOD and CAT, and repeatedly exposed to UV-A of 365 min under the condition of 30 minutes, 1 hour and 2 hours a day over 1, 2, 3, 4 and 5 days. Structural denaturation of SOD and CAT induced by repeat UV-A irradiation was confirmed by the electrophoretic analysis, and their enzyme activity was determined by the colorimetric assay using the proper assay kit. Results: SOD exposed repeatedly to UV-A showed the polymerization pattern through the electrophoretic analysis when it was repeatedly exposed under the condition of at least 1 hour a day however, the change of its activity was found to be less than 12%. On the other hand, CAT repeatedly exposed to UV-A showed reduced size of the electrophoretic band which indicated a structure denaturation and its activity was significantly decreased. In the case of that the repeat exposure time was longer, CAT activity was completely lost even though some enzyme band was shown in the electrphoretic analysis. Conclusions: From these results, it was revealed that the degree and pattern in structural denaturation of antioxidative enzymes differently appeared according to the type of enzyme, and the degree of structural denaturation was not always consistent with the reduction in enzyme activity.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.2
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• pp.85-92
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• 2007

In 1980s, a number of bridges with bare concrete deck were constructed on the Korea highway. After 20 years service, many bare concrete decks are still in good condition without special maintenance activity. Therefore, the application of the bare concrete deck is being reestimated from the view of construction and maintenance. As a part of the program, the characteristic of penetration(surface chloride and apparent diffusion coefficient) of de-icing salt into bare concrete bridge deck was analyzed in order to predict the service life of bridge on Korea highway.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.5
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• pp.81-88
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• 2007

Among deteriorations of concrete due to environmental exposure, carbonation problems of concrete structures have increased in urban and underground structures. But conventional carbonation-prediction equations that were proposed by foreign references, can not be applied directly to the prediction of carbonation for domestic concrete structures. The purpose of this study is to propose a prediction equation of carbonation depth by considering domestic exposure conditions of concrete structures. For the derivation of the equation, conventional carbonation-prediction equations are analyzed. Through considering the relationship between results of prediction equation and those of various domestic field survey data, the so-called correction factors for different domestic exposure condition of concrete structures are derived. Finally, a carbonation-prediction equation of concrete structures under domestic exposure conditions is proposed with consideration for concrete strength in core and correction factors.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.4C
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• pp.153-162
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• 2009

This paper investigates the effects of excavation-induced ground movements on nearby structures, considering soil-structure interactions of different soil and structural characteristics. The response of four and two-story block structures, which are subjected to excavation-induced advancing ground movements, are investigated in different soil conditions using numerical analysis. The structures for numerical analysis are modelled to have cracks when the shear and tensile stress exceed the maximum shear and tensile strength. The response of four and two-story block structures are investigated with advancing ground movement phases and compared with the response of structures which are subjected to excavation-induced total ground movement. The response of structures is compared among others in terms of the magnitude and shape of deformations and cracks in structures for different structure and ground conditions. The results of the comparison provide a background for better understandings for controlling and minimizing building damage on nearby structures due to excavation-induced ground movements.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.67-74
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• 2021

This paper evaluated the structural safety of an aging PSC I-girder bridge with rebar corrosion in the deck. The geometry and rebar of the bridge were designed based on an actual PSC I-girder bridge, and the numerical analysis was performed considering the crack of concrete and yielding of steel rebar. According to the evaluation criteria of Korea Infrastructure Safety and Technology Corporation, this study defined two criteria of rebar exposure and corrosion rates to construct a total of 32 corrosion scenarios. Rebar exposure was defined as the exposure of tensile rebars in the bridge deck due to the removal of cover concrete. The results of the analysis showed that the safety and rating factors of the bridge decreased with increasing rebar exposure and corrosion rates. For the rebar corrosion rate more than 50%, the safety grade of the bridge should be carefully evaluated for all the rebar exposure rate. When the rebar corrosion rate exceeds 57%, the bridge was evaluated as E grade regardless of rebar exposure rate. A correlation analysis for a 2% of rebar exposure rate found that the bridge was evaluated as A grade up to 55.8% corrosion rate, C grade up to 56.9%, D grade up to 58.5%, and E grade for corrosion rate greater than 58.5%. This study indicates the necessity of a quantitative evaluation of rebar corrosion for evaluating the structural safety of aging bridges.

• Composites Research
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• v.22 no.5
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• pp.37-42
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• 2009

Thermal analysis properties and chemical structure of carbon fiber/epoxy composites under environmental exposure were examined using an accelerated aging tester which can simulate real weather conditions such as temperature, moisture and ultraviolet. The composite specimens were exposed to combined environmental factors up to 3000 hours. Thermal analysis properties and chemical structure of the composites were evaluated with various exposure times through Modulated DSC and FTIR. According to the results of Modulated DSC, the glass transition temperature increased as exposure time increased due to the formation of network structures in the composites. Also endotherm peaks of enthalpy relaxation related to physical aging that can affect the properties of the composites were observed as exposure time increased. From the results of FTIR, it was found that the location of the peaks was little affected by exposure time, but the intensity of the peaks slightly decreased as exposure time increased due to the curing reaction in the epoxy group.

• Journal of the Korea institute for structural maintenance and inspection
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• v.21 no.2
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• pp.53-59
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• 2017

In this experimental study, the characteristic of damages on GFRP rebar exposed to high temperature only and immerged in alkaline solution after the exposure to high temperature was analyzed through microscopic image analysis. The found microcrack and pores in resin matrix were quantitatively compared if there was effect of pre-exposure to high temperature. The damages, such as microcrack and pores in resin matrix, by alkali exposure were mainly found in rebar surface. On the other hand, the pores caused by high temperatures were extensively found in a section and had greater width than those caused by the alkali exposure. In results of the quantitative comparison, the accumulated length and widths of microcrack and pores in resin matrix in pre-exposed GFRP rebar to high temperature were respectively 1.5 and 1.4 times of those in the GFRP rebar only immerged in alkali solution. Therefore, the deterioration of resin matrix by the alkali exposure could be accelerated due to the pre-exposure to high temperature.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.10 no.7
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• pp.1497-1502
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• 2009

AE(Auto exposure) is a function to maintain the exposure value of a captured image constant, and is one of the crucial functionalities of a CIS-based mobile camera. Generally AE is implemented in software, requiring a CPU and a ROM to store the corresponding software. This approach increases the hardware size at the cost of increased flexibility. In this paper, we propose an AE algorithm featuring variable frame-rate and adaptive analog gain control, as well as a FSM-based hardware architecture for a CIS-based mobile camera.