• Journal of Ecology and Environment
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• 제38권3호
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• pp.343-352
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• 2015

The landscape setting of a habitat strongly influences the distribution, abundance, and species composition of waterfowl. Thus, habitat assessment is very important to understand the habitat characteristics that sustain waterfowl assemblages. In this study, we hypothesized that the excessive use of artificial materials when new wetlands are constructed negatively influences wintering waterfowl. To test this hypothesis, we measured environmental factors, assessed habitat, and investigated waterfowl at 13 artificial wetlands in the Nakdong River Basin. There were greater numbers of waterfowl species and individuals in artificial wetlands with high habitat assessment scores. In contrast, environmental factors did not affect waterfowl distribution. In particular, features of natural habitats, such as macrophytes and sandbars, and the surrounding land-use patterns were important factors for sustaining waterfowl assemblages in each created wetland. Our results show that promoting naturalness in wetlands and surrounding areas would increase the species diversity and abundance of waterfowl. Further, complex habitats, such as wetlands and some terrestrial habitats, support both aquatic and terrestrial species because mixed habitats feature a larger array of food sources than more limited habitats do.

• 한국초전도ㆍ저온공학회논문지
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• 제20권1호
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• pp.1-10
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• 2018

The improvement of critical current properties of $REBa_2Cu_3O_{7-x}$ (REBCO) coated conductors by introducing artificial pinning centers (APCs) is examined with respect to the field-angle anisotropy, high-field performance and relaxation property with time. Nano-rods along the c-axis introduced by PLD method and isotropic nano-particles introduced by TFA-MOD method are treated. The theoretical analysis is also shown to understand the effect of APCs quantitatively. The effects of superconducting layer thickness that influences the high-field performance and relaxation property are also discussed. It is shown that the upper critical field, which is another important factor to determine the high-field property, can be improved by introduction of APCs through electron scattering at interfaces with the superconducting matrix. The optimum critical current property can be obtained by properly designing the morphology and number density of APCs and the superconducting layer thickness.

• 한국정밀공학회지
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• 제20권7호
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• pp.36-43
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• 2003

In this paper, the warm forging process sequence has been determined to manufacture the warm forged product for the precision bevel gear used as the differential gear unit of a commercial automobile. The preform shape of bevel gear influences the dimensional accuracy and stiffness of final product. So, the design parameters related preform shape such as aspect ratio and chamfer length having an influence the formability of forged product are analyzed. Then the optimal conditions of design parameters have been selected by artificial neural network (ANN). Finally, to verify the optimal preform shape, the experiments of the warm forging of the bevel gear have been executed. The proposed method can give more systematic and economically feasible means for designing preform shape in metal forming process.

• Structural Engineering and Mechanics
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• 제51권2호
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• pp.299-313
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• 2014

In the first part of this paper, the influences of some of crack parameters on natural frequencies of a cracked cantilever Functionally Graded Beam (FGB) are studied. A cantilever beam is modeled using Finite Element Method (FEM) and its natural frequencies are obtained for different conditions of cracks. Then effect of variation of depth and location of cracks on natural frequencies of FGB with single and multiple cracks are investigated. In the second part, two Multi-Layer Feed Forward (MLFF) Artificial Neural Networks (ANNs) are designed for prediction of FGB's Cracks' location and depth. Particle Swarm Optimization (PSO) and Back-Error Propagation (BEP) algorithms are applied for training ANNs. The accuracy of two training methods' results are investigated.

• KSTLE International Journal
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• 제10권1_2호
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• pp.43-47
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• 2009

Influences of carbonaceous ingredient as a solid lubricant in automotive friction materials on friction properties were studied. Three types of carbonaceous ingredients such as natural graphite, artificial graphite, and cokes were mixed using a constrained mixture design. A 1/5 scale brake dynamometer was used to obtain tribological properties. Results showed that cokes substantially increased the friction coefficient, and natural graphite effectively reduced stick-slip phenomena. This significant difference was attributed to the formation of the friction film on the brake pad which was shown to be strongly dependent on the graphite types. The different crystal structures of the carbonaceous solid lubricants played a significant role in the formation of friction film at the interface.

• 화약ㆍ발파
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• 제36권3호
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• pp.1-9
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• 2018

본 연구는 인공절리의 경사, 인공절리와 발파공 간의 거리, 그리고 인공절리의 수가 압력파동의 전파, 균열의 전파, 그리고 발파파동의 속도에 미치는 영향을 평가할 목적으로 수행되었다. 이 평가작업은 동적 FEM 프로그램인 AUTODYN 상에서 지원되는 Euler-Lagrange solver를 사용하여 수행되었다. 주요 결과로서 발파파속은 인공절리와 발파공 간의 거리가 가깝거나 인공절리의 경사가 증가할수록 더 빠르게 감소하는 것으로 나타났다. 인공절리가 없는 경우에 비해 절리가 하나라도 존재하는 경우에는 발파파속의 감쇠가 상당히 크게 발생하였다. 하지만 인공절리의 수가 발파파속의 감쇠에 미치는 영향은 주어진 조건 하에서는 미미한 수준이었다.

• Journal of Advanced Marine Engineering and Technology
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• 제34권1호
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• pp.168-176
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• 2010

인공어초의 안정성과 내구성에 대한 관심은 최근 크게 주목을 받고 있다. 본 연구에서는 사이드 스켄소나와 멀티빔에코사운더, 잠수조사를 통하여 어초의 안정성, 시설년도, 종류를 조사하였다. 그 결과 4개의 조사해역(양양, 강릉, 동해 및 삼척)에서 총 8,438개(60개의 단위어초군)가 시설되어 있는 것을 확인하였다. 그리고 그 중 85.4%가 안정한 시설 상채를 나타냈으며 나머지 14.6%가 해양의 물리적인 변수에 의해서 영향을 받은 것으로 나타났다. 대표적으로는 파손(6.3%)과 전도(8.3%)현상이 있다. 단위 어초군별로는 61.7%가 안정한 상태를 나타냈으며, 38.3%가 해양의 물리적인 영향을 받은 것으로 나타났다. 대표적인 현상은 매몰이었다.

• 자원리싸이클링
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• 제16권1호
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• pp.68-72
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• 2007

전기적 환원을 이용한 인공 사진폐수에서의 은 회수를 연속순환식 공정을 적용하여 환원시간 및 두 전극간의 전합 차, 농도유량에 따른 영향을 검토하였다. 은 함유 인공폐수 처리에 있어 적용(인가) 전압과 초기 농도가 증가함에 따라 제거율이 증가함을 보였다. 은 함유 인공폐수의 전해 반응 시, 음극에 환원 석출된 물질의 정성적인 분석을 위해 EPMA 및 XRD 분석 결과, 석출된 물질이 은임을 확인하였다.

• 정보처리학회논문지:소프트웨어 및 데이터공학
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• 제6권12호
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• pp.565-572
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• 2017

본 연구는 기존의 수요 예측 등의 시계열 연구에서 주로 사용되는 ARIMA 모형의 어려움을 극복하고자 인공신경망(Artificial neural network) 모형을 이용하여 한국 프로 야구 관중 수를 예측하였다. 훈련 자료로는 2015년 3월부터 9월까지의 일별 KBO 관중 수 자료를 대상으로 하였다. 전방향 신경망(Feedforward neural network)의 모형 훈련 과정에서, 그리드 탐색(Grid search)을 적용하여 최적의 초모수(Hyperparameter)를 찾고자 하였다. 그 결과, 그리드 탐색법의 최적 모형을 이용한 평균 절대 백분율 오차(MAPE)는 평균 20.9% 였다. 앙상블 기법을 이용한 모형의 MAPE는 평균 20.0%였다. 이는 다중회귀와 비교해보았을 때, 평균적으로 각각 26.3%, 30.3% 높은 예측력을 보인다.

• 한국실내디자인학회논문집
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• 제19호
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• pp.45-52
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• 1999

This study is on Buckminster Fuller, who is generally known as a structure engineering architect, and his influences. Fuller's radical and utopian ideas and designs were regarded as 'paper architecture'. But considering today's high cost of energy and the limited natural resources, Fuller's Dymaxion theory must be re-evaluated. Fuller's influences on the contemporary architecture are summarized as follows. 1) His idea of controlling the environment through the use of technology influenced today's 'High-Tech' architects. Architecture is no-longer designed purely by its formal character, but becomes a tool of investigating environmental significance of modern technology. 2) Through systemizing mechanical equipment, Dymaxion House prototype, and aggregation of high-tech mechanical equipments, influenced Archigram & Metabolist's capsule idea. It is expressed as a plug-in module equipment of 'High-Tech' architecture which has flexible interior with mechanical exterior image. 3) Megastructure. The Manhattan dome project gave an influence to many engineer/architects who tried to achieve an ideal artificial environment. This is in connection to 1960's utopian projects. Today's megastructures show new possibilities in urbanism and architecture. Fuller's comprehensive idea of humans living in harmony in the universe shows possibilities not only in structural engineering, but in solving various problems that confront today's architecture.