• 대한기계학회논문집B
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• 제30권4호
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• pp.364-372
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• 2006

The objective of this study is to evaluate the efficiency and the prediction accuracy of developed large eddy simulation (LES) program for complex turbulent flows, such as recirculating and swirling flows. To save the computational cost, a Beowulf cluster system consisting 16 processors was constructed. The flows in backward-facing step and dump combustor were examined as representative recirculating and swirling flows. Firstly, a direct numerical simulation (DNS) for laminar backward-facing step flows was previously conducted to validate the overall performance of program. Then LES was carried out for turbulent backward-facing step flows. The results of laminar flow showed a qualitative and quantitative agreement between simulations and experiments. The simulations of the turbulent flow also showed reasonable results. Secondly, LES results for non-swirling and swirling flows in a dump combustor were compared with the results of Reynolds-averaged Navier-Stokes (RANS) using standard $k-{\varepsilon}$ model. The results show that LES has a better performance in predicting the mean axial and azimuthal velocities, comer recirculation zone (CRZ) and center toroidal recirculation zone (CTRZ) than those of RANS. Finally, it was examined the capability of LES for the description of unsteady phenomena.

• Ocean and Polar Research
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• 제37권4호
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• pp.295-315
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• 2015

In order to determine the spatio-temporal distribution of macrobenthic faunal communities in Jinhae Bay, quantitative faunal samples were collected seasonally at 23 sites in Jinhae Bay from February, 2011 to November, 2012. Sediment facies were found to be mud except for those at Chilcheon-do near Geoje Island. Mean values of TOC (%) ranged between 1.3 and 3.6%, and these are the highest values recorded excluding special management areas in Korea. Hypoxia occurred every summer in the whole areas of Jinhae Bay except around Geoje Island in the bay mouth. Due to the summer hypoxia, species richness, density and biomass also declined during the summer in Jinhae Bay. Opportunistic species such as Paraprionospio patiens, Sigambra bassi, Nectoneanthes oxypoda and Theora fragilis occurred as the dominant species before and after the hypoxia. However, Capitella capitata appeared as a dominant species only during the winter-spring season every year. From cluster analysis, Jinhae Bay could be divided into two sites groups: one group occupied the normoxic zone and the other one located in the hypoxic zone.

• 한국환경과학회지
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• 제12권10호
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• pp.1025-1032
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• 2003

The purpose of this study is to analyze the characteristics of the urban landscape by CG(Computer Graphic) pictures and visibility analysis. In this study, the CG picture was created by using zoning data and DEM(Digital Elevation Model) on Chunchon city. The landscape type was classified into three by cluster analysis using the area rate of the element which constitutes CG picture. Visible analysis used DEM as fundamental data, and was performed by using GIS(Geographic Information System). And the frequency seen on viewshed was classified into five grades. The result of this study are as follows: 1. The area rate of the element which constitutes CG picture was high development restriction zone(43%) in type 1, green land area(39%) in type 2, and city area(24%) in type 3. 2. In the analysis results of GIS visibility analysis, it turns out that Euiam lake is important area on the landscape in all types. 3. The land use of high frequency seen on viewshed was water area, residential area in type 1, development restriction area, park area in type 2, and development restriction zone, water area in type 3.

• Journal of Forest and Environmental Science
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• 제37권4호
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• pp.269-279
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• 2021

This study was carried out to introduce the forest cover types of the Baekdudaegan inhabiting the number of native tree species. In order to understand the vegetation distribution characteristics of the Baekdudaegan, a vegetation survey was conducted on the major 20 mountains of the Baekdudaegan. The vegetation data were collected from 3,959 sample points by the point-centered quarter method. Each mountain was classified into 4-7 forests by using various multivariate statistical methods such as cluster analysis, indicator species analysis, multiple discriminant analysis, and species composition analysis. The forests were classified mainly according to the relative abundance of Quercus mongolica. There was a total of 111 classified forests and these forests were integrated into the following nine forest cover types using the percentage similarity index and by clustering according to vegetation type: 1) Mongolian oak, 2) Mongolian oak and other deciduous, 3) Oaks (Mixed Quercus spp.), 4) Korean red pine, 5) Korean red pine and oaks, 6) ash, 7) mixed mesophytic, 8) subalpine zone coniferous, and 9) miscellaneous forest. Forests grouped within the subalpine zone coniferous and miscellaneous classifications were characterized by similar environmental conditions and those forests that did not fit in any other category, respectively.

• 한국환경농학회지
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• 제28권4호
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• pp.365-370
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• 2009

The aim of this study was to investigate the vegetation types of Minarimot, in Jeju Islands. The vegetation types were classified by the Z-M school method and cluster analysis. The vegetation in Minarimot was classified into 6 communities and 2 subcommunities: Persicaria thunbergii-Isachne globosa community (vegetation type: A), Scirpus tribangulatus-Eleocharis manillata var. cyclocarpa community (B) (Aneilema keisak subcommunity (B-1) and Caldesia parnassifolia-Potamogeton distinctus subcommunity (B-2)), Eleocharis kuroguwai community (C), Phragmites communis community (D), Scirpus tabernaemontani community(E) and Typha orientalis community (F). These communities were grouped into three main categories according to cluster analysis. The community (A) established at the edge of the wetland which has the driest condition was distinguished as Group I, while the community (B) emerged in the submerged zone was distinguished as Group III. The Group II was designated as the communities (C, D, E, F) between Group I and III, whose communities were occasionally submerged. The result of principal coordinate analysis (PCoA) appeared that the different vegetation established along the wetland were depending on water environment such as water depth and the period submerged.

• 한국농공학회지
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• 제34권4호
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• pp.69-79
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• 1992

To estimate soil behavior and structural characteristics under the conditions of cyclic loading, freezing & thawing and initial state, several testing was performed and obtained following results. 1.After repeated freezing and thawing processes, original soil structure was destroyed and changed to globular structure from honeycomb or tube in its structure types. Also above processes resulted increasing the soil compression strain while decreasing the failure stress in stress-strain relationship and reached the soil structure into the mode of brittle fracture. Under cyclic loading conditions, soil cluster which was originally dispersed structure colloided with each other, seperated, and finally the soil failed due to the effect of overcompaction. 2.Through the stabilization processes seperated by four steps, the structure of soil skeleton was changed to quite different globular type. The degree of compressibility of soil was decreased in the normally consolidated zone, while the strength against external load increased due to soil particle stabilization. 3.Soil stress-strain chracteristics were largely influenced by repeated up and down processes of temperature. The maximum deformation was obtained in the case of temperature between 0 10˚C by the reseon of particle cluster reformation. 4.Soil compressibility was largely influenced by the optimum moisture content. Under freezing process, swelling could be found and its magnitude was proportional to the density of soil. 5.Density of soil was decreased as increasing the number or repeated freezing and thawing processes and the largest decreasing rate was found at the first turning point from freezing to thawing cycle.

• 한국지리정보학회지
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• 제10권4호
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• pp.22-34
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• 2007

우리나라는 그 동안 국토를 이용하고 관리함에 있어 생태적 계획에 입각한 지속가능한 보전 및 관리보다는 효율성과 경제성을 중심으로 한 개발지향적 논리에 초점을 맞춤으로써 국토 환경보전에 커다란 기여를 하고 있는 농경지 및 산지면적이 지속적으로 감소하고 있는 추세이다. 지역생태계의 가치에 대한 생태학적 인식이 부족한 가운데 이루어진 일련의 지속적인 개발압력은 자연환경의 자정능력을 초과하는 환경압력으로 작용함에 따라 지역생태계의 건전한 물질순환과 에너지 흐름에 부정적인 결과를 초래하고 있다. 이에 본 연구에서는 기존의 물환경 문제해결을 위한 공간단위로서의 유역개념이 아닌 생태계를 평가하고 관리할 수 있는 공간 단위개념으로서 유역을 분석하기 위하여 다양한 경관요소가 혼재하고 있는 낙동강 유역권을 대상으로 경관구성 요소 중 토지이용을 중심으로 공간분석기법을 활용하여 서로 유사한 패턴을 보이는 유형으로 분류하고, 각 유형별 지역에 대한 특징을 분석하였다.

• 한국지능시스템학회논문지
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• 제16권6호
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• pp.777-784
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• 2006

본 논문에서는 부분최소법 (PLS: Partial least square)과 c-퍼지 모델트리를 적용하여 클로로필-a 농도의 예측 모델을 제안한다. 제안된 방법은 모든 입력속성을 고려하여 퍼지 클러스터에 의해 계산된 중심벡터를 설정한 후, 각각의 중심벡터들과 입력속성간의 소속도를 이용하여 내부 노드를 형성하고, 형성된 내부노드에서 PLS를 적용하여 지역모델(Local model)을 구축한다. 노드의 분리기준으로서 부모노드(patent node)에서 구축된 모델에서 계산된 에러값이 자식노드(child node)에서 계산된 에러값보다 클 경우에 분기가 이루어진다. 최종 단계에서는 임의의 입력데이터와 잎노드에서 계산된 클러스터 중심값과 비교하여 소속도가 높은 클러스터에 속한 지역모델을 선택하여 출력값을 예측한다. 제안된 방법의 우수성을 보이기 위해 수질 데이터를 대상으로 실험한 결과 기존의 모델트리 방식에 비하여 향상된 성능을 보임을 알 수 있었다.

• Nuclear Engineering and Technology
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• 제54권11호
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• pp.4236-4243
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• 2022

An industrial nuclear technique based on the use of an X-ray profiler was implemented to estimate the densities or concentrations of sediments present in an Atlantic maritime zone in the areas subjected to dredging under the governance of the Panama Canal Authority (ACP). The sediment profiles show in most areas there is a concentration of between 1.00-1.15 g/cm³ except for one area in particular, the density starts at 1.20 g/cm³ and even reaches values greater than 1.50 g/cm³; therefore, an already consolidated sediment is present, which, depending on the depth found. Values of 1.265 g/cm³, 1.297 g/cm³, 1.185 g/cm³ obtained by ACP previous studies are within the range of 1.20-1.30 g/cm³ measured with the nucleonic gauge. However, it should be noted that during the tests with the X ray profiler, sediment densities values greater than the aforementioned limit were also obtained that varying according at depths close to 12 m and 18 m with values reached up to 1.513 g/cm³ and 1.60 g/cm³, respectively. This demonstrates that sediment accumulation depends on depth. This nucleonic gauge is feasible technique for the study of the sedimentation phenomenon in channel basins and even in other projects nationwide.

• 해양환경안전학회지
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• 제23권4호
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• pp.331-337
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• 2017

본 연구에서는 울진군 죽변의 암반조간대에서 2년(2015-2016)간 계절별 저서동물의 군집구조와 분포양상을 분석하였다. 죽변암반조간대의 종조성은 5문 41종으로 자포동물 4종, 연체동물 19종, 환형동물 3종, 절지동물 13종, 극피동물 2종이 출현하였으며, 총개체수 $1,642inds./m^2$, 총생체량 $1,959.42gWWt/m^2$ 조사되었다. 조간대 상부는 조무래기따개비(Chthamalus challengeri), 좁쌀무늬총알고둥(Nodilittorina radiata)이 우점하였다. 하부는 지중해담치(Mytilus galloprovincialis), 배무래기(Nipponacmaea schrenckii), 구멍밤고둥(Chlorostoma turbinata)이 우점하였다. 계절별 우점종의 경우, 조간대 상부에는 겨울과 봄에 조무래기따개비, 여름과 가을에 좁쌀무늬총알고둥이 우점하였다. 조간대 하부는 전 계절에 걸쳐서 지중해담치가 우점하였다. 군집분석을 통해 생물군집의 분기별 유사성을 분석한 결과, 이들 지역은 세 개의 그룹으로 구분되었다. 조간대 하부의 2015년 11월, 2015년 8월, 2016년 2-8월의 Group A와 조간대 하부의 2016년 11월, 2015년 5월의 Group B, 2015년-2016년 조간대 상부의 Group C로 구분되었다.