• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.54-66
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• 2001

The aim of this study was to investigate the fluoride release and some mechanical properties including 3-point bending strength, amount of abrasion, surface hardness, water sorption/solubility and cytotoxicity of the newly developed composite resins containing 8, 16, 24 wt% $SrF_2$ glass filler (VF8, VF16, VF24) and four commercially available composite resins, Heliomolar(HE), Verdonfil(VE), Z100(ZH) and Aelitefil(AE). To investigate cytotoxic effect, agar overlay assay was done. Amount of fluoride released into distilled water was measured over a 62-days period from VF8, VF16, VF24 and HE. Results were as follows: 1. Experimental composite resins showed similar mechanical properties to commercial composite resins, but 3-point bending strength and surface hardness of experimental composite resins were inferior to ZH. 2. Over a 62-day Period, the amount of fluoride released was ordered: VF24>VF16>VF8>HE. In experimental composite resins, the amount of fluoride released was 9-23 times greater than HE and seemed to be proportional to the content of $SrF_2$ glass filler. 3. Experimental composite resins and all control composite resins showed mild cytotoxicity. This study showed significantly greater fluoride release from newly developed composite resins than control(HE) and addition of $SrF_2$ glass filler did not decrease mechanical properties or increase cytotoxicity of composite resin. The results from this study imply that newly developed composite resin have adequate mechanical properites, mild cytotoxicity and some potential for secondary caries prevention.

• Journal of the Korean Solar Energy Society
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• v.26 no.3
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• pp.17-24
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• 2006

최근에 에너지절약 차원에서 종래의 공조방식을 대신할 새로운 냉난방시스템 개발이 요구되고 있는데, 본 논문에서는 태양열 집열기를 이용하는 데시컨트 시스템 중 제습역할을 실질적으로 담당하는 제습기의 충진층 부분에서의 열 및 물질전달에 관한 일련의 해석 결과를 발표하고 있다. 제습과정에서 액체흡수제는 충진층에서 열 뿐만 아니라 물질전달을 수반하게 되는데, 이 결과 건물에 냉방 및 난방효과를 가져다 준다. 따라서 이 충진층의 최적 설계가시스템의 효율을 극대화하기 위해서는 무엇보다도 중요한데, 이를 위해서는 충진층에서의 열 및 물질전달 양상을 규명하여야 한다. 따라서 금번 실험에서는 공기와 액체흡수제와의 접촉면적을 넓히기 위해서 충진재로써 3cm(직경) ${\times}$ 3cm(높이)인 시판중인 플라스틱 재질을 사용하고, 실질적으로 40cm(너비)${\sim}$40cm(깊이)${\times}$40cm(높이)의 충진층을 직접 제작하여 실험을 행하였다. 그 결과, 공기측 열 및 물질전달 계수는 공기 온도와 밀접한 관계를 갖고 있으며, 또한 물질전달계수는 열전달계수와 같은 경향을 보이고 있음을 알 수 있었다.

• Korean Journal of Food Science and Technology
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• v.41 no.3
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• pp.272-277
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• 2009

In this research, three dimensional mathematical models were developed to predict the shelf life of tofu packaged in a semi-rigid plastic container. A model combining oxygen transfer through the package and oxygen consumption within the package was considered. According to the results, the model simulations estimated that the number of microorganisms in the filled water was higher than that in the tofu, suggesting the shelf life of packaged tofu was not affected by the number of microorganisms in the tofu product, but rather by the number of organisms in the filled water. Additionally, the effects of the physical properties of the packaging material, such as oxygen permeability through the package, oxygen diffusion coefficient, the initial oxygen concentration in the filled water, and the depth of the filled water in the packaged tofu, were also observed.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.41 no.4
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• pp.347-355
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• 2021

During the earthquake, for multi-story structure, if the first floor is soft, the deformation will concentrate on that floor causing a serious damage to the column members which might leads to the collapse of the whole structure like Piloti structure during the Pohang earthquake in Korea. According to the 2016 National Disaster Management Research Institute's "Investigation of Seismic Reinforcement and Cost Analysis of Domestic Non-seismic Buildings", the rate of seismic resistance of private reinforced concrete buildings was 38.3 %. Among them, it was reported that the seismic-resistance ratio of the two to five-story structures was less than 50 %. Accordingly, the government is trying to improve the seismic rate through support projects, but the conventional seismic reinforcement methods are still expensive, and emergency construction is difficult. Therefore, in this study, the field applicability was evaluated by improving the reinforcement method using Velcro, which was developed through the research project of the Ministry of Land, Transport and Maritime Affairs in 2014. In order to improve the performance of the Velcro reinforcement method, introducing the initial tension of Velcro using high foaming rigid urethane filling between the Velcro and concrete of the columns was applied. Additionally, an experiment was conducted to evaluate the ductility of Velcro specimen from the concrete confinement effect. As a result, the ductility of the Velcro specimen was improved compare to Normal specimen. However, the energy dissipation capacity of VELCRO2 is better than VELCRO1, yet the maximum ductility of those two specimens did not show a significant difference. Therefore, the improvement of the internal filler material is still needed to have a better maximum ductility.

• Applied Chemistry for Engineering
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• v.16 no.4
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• pp.549-555
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• 2005

To evaluate the posterior and anterior restoration of polymeric dental restorative composite (PDRC), PDRC was prepared using a silica filler treated by heat at various temperatures. Compressive strength (CS) and diametral tensile strength (DTS) values were investigated to study the effect of a heat-treated silica on the mechanical properties of PDRC using the recommended dental specifications. Both the particle size and specific volume of silica were decreased upon increasing the heat treatment temperature. CS and DTS values of PDRC containing a heat-treated silica showed 1.2 and 1.3 times, respectively, higher than that of the PDRC containing a neat silica. Also, it was found that the lower heat treatment temperature, the better mechanical properties of PDRC were observed because there was less agglomeration between silica particles. Specially, PDRC using a silica treated at $600^{\circ}C$ showed superior mechanical strength.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2007.04a
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• pp.34-37
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• 2007

Propellant filling and holding test was carried out using liquid oxygen as a working fluid. The feeding line system has a filter at propellant tank outlet. Vaporization of liquid oxygen during holding after completion of filling and effect of vaporization to recirculation performance in this system was observed. Filling rate and pressure of tank ullage had the effect on state of liquid oxygen in feeding line. There was no geysering in feeding line during holding because of the position of filter.

• Journal of KSNVE
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• v.7 no.3
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• pp.411-418
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• 1997

A method to analyze the axisymmetric vibration and the internal pressure of the fluid filled, strength member embedded infinite cylindrical shell under the condition of axial static tension load applied is presented. As an example, the hose wall vibration and the internal pressure variation characteristics of a fluid filled infinite polyurethane hose are analyzed and dicussed, under the effects of the variation of the embedded strength members and the response positions.

• Proceedings of the Korean Institute of Industrial Safety Conference
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• 2003.05a
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• pp.418-421
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• 2003

경량ㆍ고강도 기능성 Composite는 경량구조재료로 차량, 항공기, 선박 및 각종 설비의 안전구조재로 그 용도가 다양하게 사용되고 있다. 특히 폐플라스틱을 이용한 경량구 조재는 가격 경쟁력이 높고 또한 환경 및 자원 재활용 측면에서 관심이 고조되고 있다. 고강도, 안전성 확보를 위해 사용가능한 폐플라스틱 소재로는 가공성이 용이한 폐Polyethylene(PE), 폐Polypropylene(PP), 폐Polyethyleneterephthalate(PET) 등을 주원료로 가공되나, 기계적 특성이 저하되어 이의 개선을 위해 여러 가지 형태의 충진재의 혼합을 통해 개선하고자 하는 연구가 진행되어 왔다.(중략)

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2007.06a
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• pp.561-562
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• 2007

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.17.2-17.2
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• 2009

Al Foam 소재는 다공질 금속으로써 저밀도 및 우수한 충격에너지 흡수능으로 최근 새로운 기능성 재료로 부상하여 세계 각국에서 연구개발이 활발하게 진행되고있다. 특히 이러한 Al Foam재를 자동차용 부품의 충격흡수재로사용할 경우 뛰어난 충격흡수능으로 인해 고안전 차량 부품 개발에 획기적인 기술 적용이 기대된다. 그러나, 종래 Al Foam재를 기계부품 등에 삽입할 경우 발포금속을 제조하여 부품 형상에 따라 가공하여 삽입하였으나 이는 공정 중 추가적인 기계 가공 및 비용이 들며 이에 따라생산성이 떨어지는 단점이 있었다. 따라서 본 연구논문에서는 차량용 충격흡수 부품 제작에있어 추가적인 가공 및 공정 수를 줄일 수 있는 Y-프로세스라는 주조공법을 적용하여 Net 형상 Al Foam재를 제작하였다. Y-프로세스는 Al Foam 금속 용탕이 주형에 투하되었을 때 Net 형상의 주형을 용탕 내 삽입하여 금속 용탕의 발포 및 응고시 Net 형상을따라 발포 및 응고가 되도록 하여 Net 형상의 Al Foam이삽입된 부품을 만드는 공법을 말한다. Y-프로세스로제조된 Al Foam재는 주형 내 완전히 충진되지는 못하였으나 주형내 충진된 Al Foam재의 상하부 셀크기가 비교적 균일한 모습을 나타내어 향후 공정제어를 통해 우수한 품질의 Net 형상 Al Foam 제조가 가능함을 알 수있었다.