• 생태와환경
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• 제54권1호
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• pp.24-38
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• 2021

금강 상류지역에 조성된 26개의 샛강형 수로에서 서식처로서 효율성과 보전방안 마련을 위해 하상기질, 환경요인, 저서성 대형무척추동물을 조사하였다. 조사기간 동안, 총 85과 160종 9305개체 m^-2의 저서성 대형무척추동물이 출현하였으며, 하상기질이 주로 굵은자갈(Pebble)과 호박돌(Cobble)로 구성되거나 빠른 물 흐름(0.2m s^-1 이상)과 높은 용존산소(120% 이상)를 가진 샛강형 수로에서 높은 종다양성이 목격되었다. 유사도 분석(Hierarchical cluster analysis)과 비모수다차원척도법(NMDS)의 결과, 26개의 샛강형 수로는 총 3개의 클러스터로 구분되었다. 클러스터 1에서 아가미지렁이, 연못하루살이, 아시아실잠자리, 등검은실잠자리, 물달팽이 등의 저서성 대형무척추동물종은 수생식물과 관련되었으며, 깔따구류, 실지렁이, 늪깔따구류 등은 하상기질이 진흙(Silt and clay)이며, 탁도와 총인이 높은 샛강형 수로에서 주로 우점하였다. 클러스터 2에 포함된 저서성 대형무척추동물종(꼬마줄날도래, 알통하루살이, 동양하루살이, 털날도래 KUa, 큰줄날도래, 플라나리아, 작은강하루살이, 다슬기, 긴다리여울벌레, 등줄하루살이)들은 굵은자갈(Pebble) 및 가는자갈(Gravel)의 비율이 높고, 유속이 빠른 지역에서 주로 풍부하였다. 클러스터 3은 주로 호박돌(Cobble)로 주로 피복된 지점들이었으며, 먹파리류의 빈도가 높았다. 이와 같이 조사지역의 분명한 구분은 각 샛강형 수로가 명확한 서식환경에 의해 지배된다는 것을 의미한다. 일부 종다양성이 낮은 지점의 경우, 유입·유출부의 기능 개선, 사행조성, 호안부 식생 정착 유도 등의 자연성 회복을 위한 개선 방안이 요구된다.

• 동굴
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• 제64호
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• pp.49-59
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• 2004

본 연구지역은 북한강과 남한강, 경안천이 합수하는 지역이다. 1973년 팔당댐의 건설로 거대한 호수가 발달하였다. 이는 유속의 감소와 퇴적, 침수 등의 현상을 가져와 호소변에 습지가 발달하는 요인이 되었다. 습지 수원은 지하수면과 함께 지표수, 강수 모두 영향을 받지만, 무엇보다도 댐의 통제계획하에서 발생하는 호소형 습지임을 알 수 있다.

• 태양에너지
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• 제12권1호
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• pp.34-39
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• 1992

본 연구에서는 f-chart method를 이용하여 대전지방에서 공기식 시스템을 적용하였을 경우의 난방효과에 대한 성능 분석을 수행하였다. 공기의 유량, 집열판 덮개의 수, 페블 베드의 축열 용량 그리고 집열판의 코팅 등에 따른 공기식 시스템의 난방 효과를 분석하였으며 아울러 액체식 시스템을 이용한 난방 시스템과도 동일 조건하에서 그 성능을 비교 분석하였다.

• 대한안전경영과학회지
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• 제2권4호
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• pp.197-208
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• 2000

ABS sensor ring has been manufactured by powder metallurgy (P/M) method using 400 series ferrite stainless steel. The results are following. It is supposedly sufficient to use for control computer due to good experimental results of magnetic characteristics. Compared with sensor ring made by iron, 400 series ferrite stainless steel has shown a good corrosion resistance without an addition surface treatment. Thus the decreasing production process has been obtained. As a result mechanical characteristics of hardness and tensile test, 400 series ferrite stainless steel shown a good endurance when it is combined to constant velocity joint(C/V), and has a good hardness properties endurable to sand and pebble impact. The products before sintering are much more corrodible in the condition of spray test of salt water and ammonia than humidity and nitrogen condition.

• 한국산업안전학회:학술대회논문집
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• 한국안전학회 1998년도 추계 학술논문발표회 논문집
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• pp.59-69
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• 1998

ABS sensor ring has been manufactured by P/M method using 400 series ferrite stainless steel. the results are as following : It is supposedly sufficient to use for control computer due to good experimental results of magnetic characteristics. Compared with sensor ring made by iron, 400 series ferrite stainless steel has shown a good corrosion resistance without an addition surface treatment. Thus the decreasing production process has been obtained. As a result of hardness and tensile test, 400 series ferrite stainless steel shown a good endurance when it is combined to C/V joint, and has a good hardness properties endurable In sand and pebble impact.

• Earthquakes and Structures
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• 제19권2호
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• pp.103-117
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• 2020

The effect of the foundation size on the efficiency of seismic base isolation using a layer of stone pebbles is experimentally investigated. Four scaled models of buildings with different stiffnesses (from very stiff to soft) were tested, each with the so-called small and large foundation, and exposed to four different accelerograms (different predominant periods and durations). Tests were conducted so that the strains in the model remained elastic and afterwards the models were tested until collapse. Each model was tested for the case of the foundation being supported on a rigid base and on an aseismic layer. Compared to the smaller foundation, the larger foundation results in a reduced rocking effect, higher earthquake forces and lower bearing capacity of the tested models, with respectable efficiency (reduced strain/stress, displacement and increase of the ultimate bearing capacity of the model) for the considered seismic base isolation compared to the foundation on a rigid base.

• Nuclear Engineering and Technology
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• 제52권4호
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• pp.674-680
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• 2020

We used MCNP6 computer code to model HTR-10 core reactor. We used two types of fuel; UO₂ and (Th+Pu)O₂ mixture. We determined the critical height at which the reactor approached criticality in both two cases. The neutronic and burnup parameters were investigated. The results indicated that the core fueled with mixed (Th+Pu)O₂, achieved about 24% higher fuel cycle length than the UO₂ case. It also enhanced safeguard security by burning Pu isotopes. The results were compared with previously published papers and good agreements were found.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.752-759
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• 2006

Conglomerates and core-stones are the typical composite geomaterials that are composed of a weak matrix and a strong pebble part. In general, we couldn't analyze the composite geomaterials by using emperical rock classification methods. In the study, a series of analyses of elastic behavior of composite geomaterials are carried out by using homogenization theory. 45-case models are made with considering 3 kind of factors such as gravel content, size and strength of matrix. Those are applicable to various composite geomaterials of conglomerates and core-stones. The size of analysis model is large enough to exceed REV.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2010년 춘계학술대회논문집
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• pp.187-194
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• 2010

Shape optimization of an upper plenum of PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of eight of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.

• 한국전산유체공학회지
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• 제15권3호
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• pp.16-23
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• 2010

Shape optimization of an upper plenum of a PBMR type gas cooled nuclear reactor has been performed by using three-dimensional Reynolds-Averaged Navier-Stokes (RANS) analysis and surrogate modeling technique. The objective function is defined as a linear combination of uniformity of flow distribution in the core and pressure drop in the upper plenum and the core. The ratio of thickness of slot to diameter of rising channels, ratio of height of upper plenum to diameter of rising channels, and ratio of height of the slot at inlet to outlet, are used as design variables for optimization. Design points are selected through Latin-hypercube sampling. The optimal point is determined through surrogate-based optimization method which uses 3-D RANS analyses at design points. The results show that the optimum shape represent remarkably improved performance in flow uniformity and friction loss than the reference shape.