• Interaction and multiscale mechanics
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• 제2권1호
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• pp.45-68
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• 2009

An aim of the study is to develop an efficient numerical simulation technique that can handle the two-scale analysis of fluid permeation filters fabricated by the partial sintering technique of small spherical ceramics. A solid-fluid mixture homogenization method is introduced to predict the mechanical characters such as rigidity and permeability of the porous ceramic filters from the micro-scale geometry and configuration of partially-sintered particles. An extended finite element (X-FE) discretization technique based on the enriched interpolations of respective characteristic functions at fluid-solid interfaces is proposed for the non-interface-fitted mesh solution of the micro-scale analysis that needs non-slip condition at the interface between solid and fluid phases of the unit cell. The homogenization and localization performances of the proposed method are shown in a typical two-dimensional benchmark problem whose model has a hole in center. Three-dimensional applications to the body-centered cubic (BCC) and face-centered cubic (FCC) unit cell models are also shown in the paper. The 3D application is prepared toward the computer-aided optimal design of ceramic filters. The accuracy and stability of the X-FEM based method are comparable to those of the standard interface-fitted FEM, and are superior to those of the voxel type FEM that is often used in such complex micro geometry cases.

• 한국해양학회지:바다
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• 제1권2호
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• pp.73-79
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• 1996

본 연구는 북동 태평양의 심해저 퇴적물에 서식하는 대형저서동물의 군집 구조와 수평적 및 수직적 분포양상을 보기 위해 1996년 5월에 수행되었다. 생물 시료는 25개 정점에서 box corer를 사용하여 채취된 퇴적물을 0.3 mm 망목의 체 로 걸러 채집하였다. 총 9개 동물문의 17개 분류군에 속하는 363개체의 저서동물이 출현하였고, 이들은 선형동물(30.0%), 유공충류(25.1%), 저서성 요각류(10.2%), Xenophyophorea(5.2%), 다모류(4.7%)순으로 우점하였다. 전형적인 중형동물 분류군 들을 제외하면 다모류가 가장 우점한 동물군이었다. 출현종의 수는 0.01 m$^{2}$ 당 평균 6종류였고, 서식밀도는 1,288개체/m$^{2}$ 로서 심해역으로는 밀도가 높았다. 퇴적물 깊이별 수직분포를 보면 표층에서 최대출현량을 보이고 깊이에 따 라 감소한다. 퇴적물 깊이 10 cm 층 이내에 전체 저서생물의 98% 이상이 출현 하였다.

• 콘크리트학회지
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• 제6권3호
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• pp.201-214
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• 1994

본 연구는 콘크리트용 혼화재로서 우리나라에 풍부한 천연 실리카 질 광물을 이용하여 콘크리트의 강도증진 가능성 및 유용성과 경제적인 효율성에 대해 검토한 것이다. 제반 실험을 통해 얻어진 결론을 요약하면 다음과 같다. \circled1 최적의 제오라이트 치환율은 단위 시멘트당 5~10% 정도를 나타났으며, 그 때의 강도 증진율은 무첨가 콘크리트 값에 비해 대체적으로 40%정도의 강도증진 효과를 얻었다. \circled2 최적의 이암 치환율은 단위 시멘트량당 10~15% 정도로 나타났으며, 그때의 강도 증진율은 무첨가 콘크리트 값에 비해 대체적으로 10%정도의 강도증진 효과를 얻었다. 이러한 검토로부터 우리는 혼화재로서 콘크리트의 강도성능의 향상을 목적으로 기존의 실리카 흄, 플라이 애쉬 등의 대체품으로 천연 실리카 광물을 활용할 수 있다는 결론을 얻었다.

• 한국지반공학회논문집
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• 제34권9호
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• pp.19-32
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• 2018

본 연구에서는 무선센서네트워크기술(Wireless Sensor Network, WSN)의 산사태 모니터링 적용성을 연구하였다. WSN시스템은 IEEE 802.14e 표준규격을 사용하는 데이터의 수집과 전달을 위한 센서노드와 데이터를 수집 처리하고 최종 서버로 전송하는 게이트웨이로 구성하였다. 센서네트워크의 토폴로지는 유연성과 신뢰성이 높은 메쉬형을 채택하였으며, 서울시의 총 3개소에 테스트베드를 구축하였다. 산사태를 모니터링 하기 위하여 각 센서노드에는 함수비계, 모관흡수력계, 경사계, 강우량계를 설치하였다. 센서노드의 배치를 위해 산사태 위험도 해석, 임목밀도 및 지형분석을 통한 통신범위 분석을 수행하였다. 측정된 계측 데이터를 분석한 결과 네트워크의 연결은 양호하게 나타났으며, 강우에 의한 지반의 반응이 실내에서 측정한 함수비-모관흡수력과 유사한 결과를 나타났다. 따라서, 테스트베드 사례를 통해 산사태 모니터링에 적용이 가능함을 확인하였다.

• Wind and Structures
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• 제17권6호
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• pp.647-670
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• 2013

The paper presents a numerical approach to study of fluid flow characteristics and to predict performance of wind turbines. The numerical model is based on Finite-volume method (FVM) discretization of unsteady Reynolds-averaged Navier-Stokes (URANS) equations. The movement of turbine blades is modeled using moving mesh technique. The turbulence is modeled using commonly used turbulence models: Renormalization Group (RNG) k-${\varepsilon}$ turbulence model and the standard k-${\varepsilon}$ and k-${\omega}$ turbulence models. The model is validated with the experimental data over a large range of tip-speed to wind ratio (TSR) and blade pitch angles. In order to demonstrate the use of numerical method as a tool for designing wind turbines, two dimensional (2-D) and three-dimensional (3-D) simulations are carried out to study the flow through a small scale Darrieus type H-rotor Vertical Axis Wind Turbine (VAWT). The flows predictions are used to determine the performance of the turbine. The turbine consists of 3-symmetrical NACA0022 blades. A number of simulations are performed for a range of approaching angles and wind speeds. This numerical study highlights the concerns with the self-starting capabilities of the present VAWT turbine. However results also indicate that self-starting capabilities of the turbine can be increased when the mounted angle of attack of the blades is increased. The 2-D simulations using the presented model can successfully be used at preliminary stage of turbine design to compare performance of the turbine for different design and operating parameters, whereas 3-D studies are preferred for the final design.

• 한국의류산업학회지
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• 제15권2호
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• pp.231-239
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• 2013

This research developed a smart girdle for adult women in their 20's that has an inserted carbon weaving heater to help with relief from coldness and abdominal disease through the thermal insulation effect. A pocket of powernet fabric was attached to the inside of the girdle for the easy insertion and separation of the heating device, while the heating device was fixed to a mesh material by cotton yarn and was wrapped with elastic lining material to prevent the mechanical devices from being exposed. A set of 3 hooks was attached to the center of the back of the heating device in consideration of convenience and mobility. Whereas the switch was inserted into around the right waistband, and the battery into the inner pocket around the waist, to integrate the heating device with the girdle. The satisfaction and usability of the fabricated smart girdle was verified by having research participants wear it to evaluate the appearance change caused by the device, the inconvenience of wearing/unwearing, mobility, and the satisfactory functionality of the device. As a result, the grand mean was evaluated to be high, with appearance (4.19), mobility (4.17), and functionality (4.51) being higher than 4.00; which indicates that the heat generation function of the smart girdle is effective. It may be said that such collection and analysis of data that reflect users' opinions have value and significance in that they can be grafted onto future research on new technology as well as they contribute to taking a step forward in the rapidly increasing research of smart clothing, with the new-type clothing equipped with new function.

• Structural Engineering and Mechanics
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• 제65권3호
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• pp.291-302
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• 2018

Rigid body spring method (RBSM) is an effective tool to simulate the cracking process of structures, and has been successfully applied to investigate the behavior of reinforced concrete (RC) members. However, the theoretical researches and engineering applications of this method mainly focus on two-dimensional problems as yet, which greatly limits its applications in actual engineering projects. In this study, a three-dimensional (3-D) RBSM for RC structures is proposed. In the proposed model, concrete, reinforcing steels, and their interfaces are represented as discrete entities. Concrete is partitioned into a collection of rigid blocks and a uniform distribution of normal and tangential springs is defined along their boundaries to reflect its material properties. Reinforcement is modeled as a series of bar elements which can be freely positioned in the structural domain and irrespective of the mesh geometry of concrete. The bond-slip characteristics between reinforcing steel and concrete are also considered by introducing special linkage elements. The applicability and effectiveness of the proposed method is firstly confirmed by an elastic T-shape beam, and then it is applied to analyze the failure processes of a Z-type component under direct shear loading and a RC beam under two-point loading.

• 한국지리정보학회지
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• 제1권1호
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• pp.99-108
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• 1998

국지 기상 모형의 지표 특성을 표현하기 위해 토양 구분, 식생 구분, 지표 거칠기 길이, 지표 알베도와 엽면지수가 지면 과정 모수화 내에서 처방되어야 한다. 이 연구에서는 인공위성 관측값으로부터 계절함수로 얻어진 경,위도 1도 및 1도의 엽면지수, 지표거칠기 길이, 눈이 없을 때의 지표 알베도와 상세 격자 NDVI를 지면 과정 모형에 적용하였다. 생물권과 대기권 사이, 지면과 대기 사이의 상호작용에서 이러한 인공위성 자료를 사용한 것과 사용하지 않은 것을 비교함으로써, 열, 에너지 및 수증기 속들, 지면 기온, 바람, 식생 물함유량, 비습, 강수장의 민감도가 조사되었다.

• 한국지반신소재학회논문집
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• 제15권4호
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• pp.25-32
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• 2016

지반공학에서 평면변형율을 가정하는 2차원 사면안정해석은 일반적으로 널리 사용되고 있다. 이 가정은 사면활동이 넓은 영역에 걸쳐서 발생되는 가정이므로 3차원 효과가 무시된다. 대다수 연구에서 2차원해석의 최소안전율값은 3차원해석에 비하여 작게 평가되는 보수적인 결과를 나타낸다. 최근에는 컴퓨터의 소프트웨어와 하드웨어를 포함한 해석방법의 발달로 3차원해석에 대한 요구가 커지고 있다. 본 논문에서는 원호모드, 병진모드사면을 이용하여 유한요소에 의한 2, 3차원해석 및 2차원 한계평형해석을 통하여 수치해석을 실시하였다. 해석결과 매개변수(요소망크기, 체적팽창각(dilatency angle), 경계조건, 응력이력, 모델차원)에 따른 사면안정해석에 미치는 영향을 분석하였다. 해석결과 2차원 해석보다 3차원 해석에 의한 사면의 안전율 값은 항상 크게 평가되며, W 뱡향 경계조건이 롤러지지인 경우, 사면폭에 의한 결과 차이는 없는 것으로 조사되었다.

• 한국의류학회지
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• 제40권1호
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• pp.97-113
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• 2016

This study develops pant patterns using body shape, measurement and shell mesh data to decide optimal women's pants according to styles with excellent size, fit and shape for different individuals and silhouettes. Standard landmarks, lines, triangles and structures were set on a 3D scanned lower body shell to represent women in their twenties and flattened as a 2D pattern. Patterns were created and analyzed according to culotte, formal, slacks and tight type considering crotch shape, location of the crotch point, and adjusting waist darts. Flattened patterns were rotated to compare existing methods. The crease lines were then set through the hip protrusion point and compared. The main factor of the pant pattern were extracted, total rise, crotch depth, crotch width, angle of center line, shape of the center line curve, the thigh width, the amount of waist dart, and crease line position. With going tight style from the culotte, the fits are closer to the figure with minimized thigh circumference, the dart amount decreases, the crotch depth increases, the crotch extensions were shorter, and the angle of the center back increased. The total rise is U shape for culotte and is closer to V shape as the silhouette tightens. T-test of appearance evaluation of the developed pant pattern were conducted after analyzing measurements and shapes of each styles. The results of the developed patterns were superior to existing patterns in accordance to hip line between body and pants as well as appearance evaluation. We found systematic mechanisms among pattern factors that create various pant silhouettes. Evidence on classification of the silhouettes of traditional types of pants were explained objectively through the process of playing out 3D forms.