• 한국지형학회지
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• 제28권1호
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• pp.35-50
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• 2021

In this study, we analyzed the changes in the topographical landscape and the sedimentary environment to evaluate the ecological value of the Dongcheon Estuary and protect the wetland, and presented the conservation management method of the Dongcheon Estuary. Based on the result of topographical landscape analysis, agricultural land tended to decrease continuously, and artificial structures gradually increased. Moreover, in sediment analysis, the Dongcheon Estuary showed both the characteristics of river sediments and coastal sediments, and in some areas problems such as acidification and nutritional imbalance appeared. Therefore, in order to protect and manage the Dongcheon Estuary with high ecological value, it is necessary to limit the development around micro topography and minimize the artificial damage in the Dongcheon Estuary. In addition, efforts such as securing facilities for reducing pollutants and freshwater wetlands for pollutants, that flow in from nonpoint pollutants are required.

• The Journal of Advanced Prosthodontics
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• 제9권2호
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• pp.85-92
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• 2017

PURPOSE. The aim of this study was to evaluate the effect of tooth surface pre-treatment steps on shear bond strength, which is essential for understanding the adhesive cementation process. MATERIALS AND METHODS. Shear bond strengths of different cements with various tooth surface treatments (none, etching, priming, or etching and priming) on enamel and dentin of human teeth were measured using the Swiss shear test design. Three adhesives (Permaflo DC, Panavia F 2.0, and Panavia V5) and one self-adhesive cement (Panavia SA plus) were included in this study. The interface of the cement and the tooth surface with the different pre-treatments was analyzed using SEM. pH values of the cements and primers were measured. RESULTS. The highest bond strength values for all cements were achieved with etching and primer on enamel ($25.6{\pm}5.3-32.3{\pm}10.4MPa$). On dentin, etching and priming produced the highest bond strength values for all cements ($8.6{\pm}2.9-11.7{\pm}3.5MPa$) except for Panavia V5, which achieved significantly higher bond strengths when pre-treated with primer only ($15.3{\pm}4.1MPa$). Shear bond strength values were correlated with the micro-retentive surface topography of enamel and the tag length on dentin except for Panavia V5, which revealed the highest bond strength with primer application only without etching, resulting in short but sturdy tags. CONCLUSION. The highest bond strength can be achieved for Panavia F 2.0, Permaflo DC, and Panavia SA plus when the tooth substrate is previously etched and the respective primer is applied. The new cement Panavia V5 displayed low technique-sensitivity and attained significantly higher adhesion of all tested cements to dentin when only primer was applied.

• 한국재료학회지
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• 제20권6호
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• pp.312-318
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• 2010

Multilayer Poly methyl methacrylate (PMMA)/ Poly vinyl alcohol (PVA) bone plates were fabricated using electrospinning and in vitro investigations were carried out for pre-clinical biocompatibility studies. The initial cellular cytotoxicity of the methacrylate (PMMA)/ Poly vinyl alcohol (PVA) bone plates was measured by MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) assay using fibroblast-like L-929 cells. Cellular adhesion and differentiation studies were carried out using osteoblast-like MG-63 cells. As simulated body fluid (SBF) contains the same ionic concentration of body fluid and any bioactive material tends to deposit bone-like apatite on the samples surfaces into the SBF, in vitro bioactivity of the multilayer bone plates were investigated using SBF. We also studied the internal organization and tensile strength of the multilayer PMMA/PVA bone plates using micro-computed topography (${\mu}$-CT) and universal testing instrument (UTI, Korea) respectively. The cellular cytotoxicity study with MTT confirmed that the cellular viability was 78 to 90% which indicates good cyto-compatibility. Scanning electron microscopic findings revealed a good attachment and adhesion phenomenon of MG-63 cells onto the surfaces of the samples. Cellular differentiation studies also showed that osteogenic differentiation was switched on in a timely manner and affirmed along with that of the control group. Bone-like apatite formation on the surfaces was confirmed within 14 days of SBF incubation. Initial organizations of the multilayer PMMA/PVA bone plates were characterized as dense and uniform. The tensile strength of the post-pressing electronspun mat was higher than that of the pre-electronspun mat. These results suggest that a multilayer PMMA/PVA bone plate system is biocompatible, bioactive and a very good alternative bone plate system.

• 한국산학기술학회논문지
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• 제12권6호
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• pp.2457-2462
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• 2011

생산방식의 변화에 따라 3차원 형상을 신속하고 정확하게 측정하는 것이 중요해졌다. 가장 훌륭한 비접촉 3차원 측정방법인 모아레 방법 중 잡음신호를 효과적으로 제거할 수 있는 위상천이 방법을 구현함에 있어 DMD를 이용하여 격자를 생성하고 이송하는 효과를 발생하도록 하였다. 컴퓨터에서 격자를 이송하고 위상천이를 발생하므로 기계적 이송으로 인한 잡음신호의 발생 가능성을 배제할 수 있으며 광학렌즈와의 적절한 조합을 통해 쉽게 분해능을 변화하며 3차원 정보 획득이 가능하다. 근본적인 $2\pi$ 모호성문제를 극복하기 위하여 2차원 위상정력을 실시하였다. 이 방법을 적용하여 3차원 형상의 측정을 수행하였다.

• 한국지역지리학회지
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• 제15권2호
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• pp.204-214
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• 2009

본 연구의 목적은 2002년에 습지보호지역으로 지정된 천성산 화엄늪의 형성과정을 밝혀 지속가능한 습지관리를 위한 기초자료를 제공하는 것이다. 퇴적물 주상 시료와 부식의 탄소연대측정 결과로 볼 때, 화엄늪 습지보호지역의 초지는 지난 빙기의 기후변화와 관련없이 주민들의 화전농업에 의하여 만들어진 것으로 판단된다. 그리고 화엄늪은 천성산 정상부에 내린 강우가 지하로 침투하여 흐르다가 절리를 따라 능선 부분에서 용출하여 형성된 산지습지이다. 화엄늪 습지의 수량을 유지하기 위하여 습지보호지역 남서부의 주능선에 밀생하는 숲을 유지하여야 하며, 습지 하류 말단부를 지지하는 계단상의 거력제(block dam)가 붕락되지 않도록 유지하여야 한다. 그리고 습지의 주기적인 모니터링을 통하여 화엄늪 습지보호지역 내 지형과 수문변화를 측정하고 분석하여야 할 것이다.

• 한국조경학회지
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• 제34권3호
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• pp.1-11
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• 2006

This study analyzed characteristics of natural and human environments in Chuncheon's Gongji stream, and suggested nature-friendly planning strategies for self-purification of water quality, biodiversity improvement and conservative waterfront recreation. The environmental analysis included streambed structures, floodplain soils, water quality, vegetation, wildlife, and human facilities. Natural colonization of vegetation for the middle section of the study stream was obstructed by a straightened concrete revetment of baseflow channel, and vehicle movement and concrete parking lots across the floodplain. These human disturbances also deteriorated the naturalness of the stream landscape and limited habitation of bird species. However, natural sedimented wetlands in half of the channel width for the lower section of the stream contributed to a desirable vegetational landscape and greater bird occurrence. Based on BOD measurements, water quality of the stream fell under class $II{\sim}III$ of the stream water-quality standard, but it was worse around sewage outlets due to incomplete sewage collection especially during the dry season. Dominant fish species included typical inhabitants of good water-quality streams that are tolerant of adverse habitat changes. Nature-friendly planning strategies were established based on analysis of the environmental characteristics. They focused on not merely spatial zoning and layout divided into four zones - preservation, partial preservation, conservation and use -, but close-to-nature channel revetment techniques, natural water-purification facilities, biotope diversification, and water-friendly recreation and circulation. Strategies pursued both renewal of stream naturalness and hydraulic stability of streamflow by minimizing transformation of natural channel micro-topography and biotope, and by reflecting natural traces of streambed structures such as revetment scour and sedimentation.

• Water Engineering Research
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• 제6권3호
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• pp.131-147
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• 2005

Today, a trend that tries to return the artificial space of a river to a natural one is expanding. But in Korea, which lies in the monsoon climate zone, rivers endure flood damage every year. Moreover, climatic change from global warming causes severe variations in precipitation patterns. Until recently, river restoration practices in Korea have followed partial restoration. These restorative treatments transformed artificial structures of the stream to natural ones and introduced natural vegetation by imitating natural or semi-natural streams. Treatment transformed the riparian structure and increased the diversity of micro-topography and vegetation. Furthermore, restoration recovered species composition, increased species diversity, and inhibited the establishment of exotic species. In particular, the Suip stream, which was left to its natural process for approximately 50 years, recovered its natural features almost completely through passive restoration. An urban stream, the Yangjae, and a rural stream, the Dongmoon, were restored partially by applying ecological principles. On the contrary, technological treatment applied to recover flood damage induced species composition far from the natural vegetation and decreased species diversity. Additionally, this treatment increased exotic species. The same results were found also in benthic invertebrate and fish fauna. The above-mentioned results reflect the importance of ecological considerations in river management.

• 전자공학회논문지D
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• 제36D권10호
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• pp.37-44
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• 1999

건식 식각 공정을 시뮬레이션하기 위하여, 플라즈마 챔버 내의 식각 이온 거동 메카니즘을 몬테카를로 수치해석 방식으로 구현하였고, 식각 이온의 거동에 의한 기판의 식각 형상을 확인하기 위하여 셀 방식의 표면 전진기를 개발하였다. 몬테카를로 수치 계산의 단점인 과다한 계산 시간을 효과적으로 감소시키기 위하여, CRAY T3E 병렬 컴퓨터와 여러대의 워크스테이션을 연결한 MPI 환경에서 몬테카를로 병렬 계산 알고리즘을 개발하였다. 본 연구에서 개발한 몬테카를로 병렬 계산 알고리즘은 95% 이상의 효율성을 보이며, 16개의 프로세서를 사용하였을 때 16의 스피드업(Speedup) 값을 얻었다. 또한 셀 방식의 병렬 연산 표면 전진기를 이용하여 토포그래피 시뮬레이션을 수행한 결과에서, 셀의 개수가 2갭만 개 일 때, 약 600Mb 이상의 메모리가 소요되므로 단일 워크스테이션 환경에서는 불가능한 계산이 본 연구에서 개발한 병렬 계산 알고리즘을 이용하였을 때 32개의 프로세서에서 15분의 계산시간이 소요되었다.

• Journal of Ecology and Environment
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• 제29권2호
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• pp.113-124
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• 2006

Landscape structure, habitat types, vegetation structure and biodiversity in the Bokha stream chosen as a reference stream were investigated to get ecological information necessary for restoration of urban stream degraded by excessive artificial interference. Landscape structure showed a slight change between before and after flooding. Habitat types of nine sorts were identified based on ecological information obtained from field survey such as micro-topography, hydrological characteristics, disturbance regime, and so on. Each habitat holds specific organisms to each site. Consequently, the number of plant communities, and species of benthos and fish increased as the kinds of habitat type increase. Ordination of habitat types based on vegetation, benthos, and fish data reorganized them into three groups of pool types of two kinds depending on whether they are connected to the water course or not and riffle one. Vegetation showed different stratification and species composition depending on topographical position in relation to disturbance cycle. Based on the results from this study, relationship between environmental heterogeneity and biodiversity was discussed and a restoration plan was suggested in a viewpoint of vegetation.

• 한국진공학회:학술대회논문집
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• 한국진공학회 2010년도 제39회 하계학술대회 초록집
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• pp.276-276
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• 2010

Large-area micropatterned array of Co/Ni bilayer anti-dots was fabricated using photolithography and wet etching process. The surface morphology as well as the surface topography was checked by scanning electron microscopy and atomic force microscopy, whereas the magnetic properties were studied by magneto-optical Kerr effect (MOKE) and magnetic force microscopy (MFM). Systematic studies of the magnetic-reversal mechanism, the in-plane anisotropy and the switching field properties were carried out. To get a comprehensive knowledge about the domain configuration, we also employed OOMMF simulations. It was found from the MOKE measurements that a combined effect of configurational and the magneto-crystalline anisotropy simultaneously works in such micropatterned bilayer structures. In addition, the inclusion of holes in the uniform magnetic film drastically affected the switching field. The MFM images show well-defined domain structures which are periodic in nature. The micromagnetic simulations indicate that the magnetization reversal of such a structure proceeds by formation and annihilation of domain walls, which were equally manifested by the field-dependent MFM images. The observed changes in the magnetic properties are strongly related to both the patterning that hinders the domain-wall motion and to the magneto-anisotropic bilayered structure.