• 대한치과보철학회지
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• 제45권3호
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• pp.362-374
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• 2007

Statement of problem. The intial stability for osseointegration of implant has been an interesting factor. Especially, in the case of poor bone quality or immediately loaded implant, various strategies have been developed focusing on the surface of materials to improve implant fixation to bone. The microscopic properties of implant surfaces play a major role in the osseous healing of dental implants. Purpose. The aims of this study are to perform a histologic and histomorphometric comparison of the healing characteristics of three different surfaces and the comparison of resonance frequency analysis (RFA) values measured by $Osstell^{TM}$ and perio-test values (PTV) measured by Periotest. Material and methods. A total of 24 screw titanium implants (Dentium Co., Seoul, Korea) with 6mm in length and 3.4mm in diameter, were placed in the mandible of 4 beagle dogs. Implants were divided into three groups following the surface treatment methods: Group I is machined(control group). Group II is anodically oxidized. Group III is coated 500nm in thickness with hydroxyapatite(HA) by ion beam assisted deposition(IBAD) on the anodized oxidization. Bone blocks from 2 dogs were caught after 3 weeks of covered healing and another blocks from 2 dogs after 6 weeks. RFA values and PTV were measured right after insertion and at 3 and 6weeks. Histomorphometric analysis was made with Kappa Image Base System to calculate bone-to-implant contact (BIC) and bone area inside the threads. Pearson's correlation analyses were performed to evaluate the correlation between RFA and PTV, BIC and bone area ratio of three different surfaces at 3 and 6 weeks. Results. 1) In all surface treatment methods, the RFA values decreased and the PTV values increased until 6 weeks in comparison to initial values. 2) At 3 weeks, no significant difference was found from bone-to-implant contact ratio and bone area ratio of three different surface treatment methods(P>0.05). However, at 6 weeks, different surface treatment methods showed significantly different bone-toimplant contact ratio and bone area ratio(P<0.05). 3) In the implants with the IBAD on the anodic oxidization, significant difference was found between the 3 weeks and the 6 weeks bone area ratio(P<0.05). 4) Correlation was found between the RFA values and the bone area ratio at 3 and 6 weeks with significant difference(P<0.05). Conclusions. These results indicate that the implants with the IBAD on the anodic oxidization may have a high influence on the initial stability of implant.

• 한국물환경학회지
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• 제37권3호
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• pp.157-167
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• 2021

Korea needs to develop a rational system to separate stormwater utility fee from current sewerage fee. In this study, the scenario for calculating stormwater utility fee of Bupyeong-gu was suggested and the results were considered. For this purpose, the application of stormwater utility fee overseas and current domestic system were analyzed. A three step calculating scenario considering suitable domestic situation and impervious surface area was suggested. Water, sewerage usage, and hydrant data were collected. The total amount of water and sewerage fees for land use were calculated. The sewerage fee of Bupyeong-gu for the year 2014 was 21,685,446,578 won. Assuming that 40% of this amount was the cost associated to stormwater, the result showed that the fees for residential area in third step decreased by 0.77% compared to that of the first step. For commercial area, the stormwater utility fee decreased by 36.87%. For industrial area, although the consumption of water was similar to that of commercial area, the stormwater utility fee increased by 8.35%. For green area, the fee increased by 37.46%. This study demonstrated that the calculation of actual stormwater utility fee using impervious surface map and impervious Surface Ratio Estimation Methodology developed in previous studies is feasible.

• Carbon letters
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• 제28권
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• pp.47-54
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• 2018

High surface carbon aerogels with hierarchical and tunable pore structure were prepared using ionic liquid as carbon precursor via a simple salt templating method. The as-prepared carbon aerogels were characterized by nitrogen sorption measurement and scanning electron microscopy. Through instant visual observation experiments, it was found that salt eutectics not only serve as solvents, porogens, and templates, but also play an important role of foaming agents in the preparation of carbon aerogels. When the pyrolyzing temperature rises from 800 to $1000^{\circ}C$, the higher temperature deepens the carbonization reaction further to form a nanoporous interconnected fractal structure and increase the contribution of super-micropores and small mesopores and improve the specific surface area and pore volume, while having few effects on the macropores. As the mass ratio of ionic liquid to salt eutectics drops from 55% to 15%, that is, the content of salt eutectics increases, the salt eutectics gradually aggregate from ion pairs, to clusters with minimal free energy, and finally to a continuous salt phase, leading to the formation of micropores, uniform mesopores, and macropores, respectively; these processes cause BET specific surface area initially to increase but subsequently to decrease. With the mass ratio of ionic liquids to salts at 35% and carbonization temperature at $900^{\circ}C$, the specific surface area of the resultant carbon aerogels reached $2309m^2g^{-1}$. By controlling the carbonization temperature and mass ratio of the raw materials, the hierarchically porous architecture of carbon aerogels can be tuned; this advantage will promote their use in the fields of electrodes and adsorption.

• 한국지리정보학회지
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• 제26권2호
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• pp.42-54
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• 2023

우리나라 대도시 지역에 인구가 집중되고 이에 따른 수요를 충족시키기 위하여 저밀도 주거지가 재개발·재건축을 통하여 고밀도 주거지화 되고 있다. 그러나 단시간에 이루어진 대규모의 재건축은 도시녹지 면적 감소에 의한 열섬현상을 발생시키는 등 도시 기후에 부정적인 영향을 끼치게 된다. 본 연구에서는 Landsat 8 위성영상을 활용하여 서울특별시 강동구 고덕동, 둔촌동 재건축 지역의 2013년에서 2022년까지의 지표 온도의 변화를 분석하였다. 고덕동 지역에서는 재건축이 진행되는 대상지와 산림지역, 산림과 시가지가 혼재된 지역, 저층주거지역에 대한 지표 온도의 차이를 분석하였으며, 둔촌동 지역에서는 대상지와 산림지역, 저층주거지역에 대한 지표 온도의 차이를 분석하였다. 분석은 지표 온도 차이에 대한 다중회귀분석을 통하여 진행되었다. 고덕동 지역과 둔촌동 지역에서 공통적으로 재건축 전단계까지 전반적으로 지표 온도가 산림보다 높고 저층주거지역보다 낮게 나타났다. 이러한 특징들은 고덕동, 둔촌동의 저층주거지역이 대상지보다 녹지율이 낮고 건폐율이 높기 때문에 발생하였음을 알 수 있다. 본 연구를 통해 저밀도 지역이 고밀도화가 되더라도 녹지와 건폐율을 적절하게 관리한다면 도시열섬현상을 완화시킬 수 있음을 알 수 있다.

• Advances in concrete construction
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• 제16권3호
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• pp.155-167
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• 2023

The penetrated chloride in concrete has different behavior with mix proportions and local exposure conditions, even in the same environments, so that it is very important to quantify surface chloride contents for durability design. As well known, the surface chloride content which is a key parameter like external loading in structural safety design increases with exposure period. In this study, concrete samples containing OPC (Ordinary Portland Cement), GGBFS (Ground Granulated Blast Furnace Slag), and FA (Fly Ash) had been exposed to submerged, tidal, and splash area for 5 years, then the surface chloride contents changing with exposure period were evaluated. The surface chloride contents were obtained from the chloride profile based on the Fick's 2nd Law, and the regression analysis for them was performed with exponential and square root function. After exposure period of 5 years in submerged and tidal area conditions, the surface chloride content of OPC concrete increased to 6.4 kg/m³ - 7.3 kg/m³, and the surface chloride content of GGBFS concrete was evaluated as 7.3 kg/m³ - 11.5 kg/m³. In the higher replacement ratio of GGBFS, the higher surface chloride contents were evaluated. The surface chloride content in FA concrete showed a range of 6.7 kg/m³ to 9.9 kg/m³, which was the intermediate level of OPC and GGBFS concrete. In the case of splash area, the surface chloride contents in all specimens were from 0.59 kg/m³ to 0.75 kg/m³, which was the lowest of all exposure conditions. Experimental constants available for durability design of chloride ingress were derived through regression analysis over exposure period. In the concrete with GGBFS replacement ratio of 50%, the increase rate of surface chloride contents decreased rapidly as the water to binder ratio increased.

• 대한화장품학회지
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• 제13권1호
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• pp.15-28
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• 1987

Silica spheres were prepared by interfacial reaction method. Factors in-fluencing to the mean particle size and specific surface area of silica spheres were investigated. The experiment about the surface modification of silica spheres was carried out. It was observed that silica spheres have characteristics of the spherical shape with the vacancy in the inner side, high surface area, and reaction tendency by many silanol group. The mean particle size of silica spheres is dependent on the surfactant concentration and W/O ratio. The specific surface area is influenced by SiO2/Na2O mole ratio in sodium silicate. Silica spheres coated with titanium dioxide or zirconium dioxide improve the UV protection effect. Titanate and silane coupling agent make chemical bond with silica surface and improve the organophile and the dispersibility of silica spheres.

• Journal of Plant Biology
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• 제16권1_2호
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• pp.1-5
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• 1973

Six young trees of Alnus tinctoria grown in isolation, each having different growing stage, were selected and the surface area of their roots, stems and leaves was determined. Each of the roots of more than 0.2mm in diameter and stems was cut at intervals of 10cm and their surface area was calculated with 2$\pi$rl from the average diameter (2r) of both sections (upper and lower) by making cylindrical estimation of the cut pieces. The leaf area measured was only one side area, and the volume of cut piece and amount of dry matter of each organ were also measured. The percentage to the surface area of the whole plant body by each organ was 4-12% in root, 7-9% in stem and 69-89% in leaf, respectively. There was relatively a little individual difference. However, the surface area ratios of root and stem showed a slightly increasing tendency while that of leaf decreasing according to the growing stage. The ratio of sum leaf area index (LAIi) was 2.3-4.0$m^2$/$m^2$-and that of the surface area index(SaIi) was 0.16-0.33$m^2$/$m^2$, respectively. It has been known that the stem surface area(SAI) to the leaf area index(LAI) is within the range of 31-53%, but the SAIi is within the range of 8-11% of the LAIi.

• Corrosion Science and Technology
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• 제9권1호
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• pp.39-47
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• 2010

Galvanic coupling between GECM(graphite epoxy composite material) and metallic materials can facilitate corrosion of metals and alloys because GECM is noble and electrically conductive. Galvanic corrosion is affected by many factors including metallic materials, area ratio, surface condition, and corrosivity. This work aims to evaluate the effect of area ratio on galvanic corrosion between GECM and several metals. In the case of glavanic coupling of carbon steel and Al to GECM, corrosion rate increased with increasing area ratio. Corrosion rate of sensitized STS 316S stainless steel decreased a little at an area ratio 1:1 but increased at an area ratio 30:1. It is considered to be due to that area ratio affects galvanic corrosion more in less corrosion resistant alloys. However, in case of STS 316 and Ti, galvanic coupling reduces corrosion rate by the formation of passive film.

• KIEAE Journal
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• 제10권6호
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• pp.91-96
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• 2010

The problem of urban climate change and destruction of wildlife habitats space which is becoming more serious day by day, has to do with the impervious area(surface area) in urban space. The destruction of natural ground and indiscreet soil covering due to compact development is causing urban desertification in urban residential areas. With biotops area ratio being variously used and extended as a pre planning index, this study aims to analyze the elements of biotop area ratio that need to be supplemented in order to emerge as a realistic planning index for post evaluation measure and not act only as a examining tool in the planning stage. In particular, this study aims to examine the possibility of biotops area ratio to be used as a system to evaluate the outer space of apartment housings, in which biotops area ratio is most actively used, as a tool to secure ecological soundness of the development area after construction is finished.

• 대한원격탐사학회지
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• 제28권2호
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• pp.203-214
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• 2012

콘크리트와 아스팔트가 상당 부분을 차지하는 도시의 물리적인 환경은 도시열섬효과를 일으키는 주요 원인이며, 일차적으로 토지이용 또는 토양피복에 따른 지표면온도의 상승으로 나타난다. 본 연구에서는 도시의 토지피복유형이 지표면온도에 미치는 영향을 공간해상도가 다른 MODIS, Landsat ETM+과 RapidEye 위성영상을 사용하여 비교 분석해 보았다. 연구대상지인 일산 신도시지역의 지표면온도는 토지 이용에 따라 뚜렷이 구분되는 패턴을 보여주었는데 건폐율이 높은 저층단독주택지구보다 건폐율이 낮고 녹지율이 높은 고층 아파트단지의 지표면온도가 현저히 낮게 나타났다. 토지피복유형과의 관계는 건물이나 도로 등 도시화지역의 면적이 증가할수록 기후존의 지표면온도가 증가하고, 식생과 수면, 그림자 지역의 면적이 늘어날수록 지표면온도는 떨어진다. NDVI와 지표면온도 사이에도 음의 선형상관관계가 나타나지만, 계절적 영향을 배제하기 어렵다는 단점이 있다.