• 한국농공학회지
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• 제43권4호
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• pp.89-96
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• 2001

In this study non-linear finite element analysis of dynamic response of steel arch under partially distributed dynamic load was discussed. Material and geometric non-linearities were included in finite element formulation and steel behavior was modeled with Von Mises yield criteria. Either radial or vertical dynamic load was dealt in numerical examples. Normal arch and arch with maximum shape imperfection of L/11,000 were studied. The analysis results showed that maximum displacement at the center of arch was occurred when 70% of arch span was loaded. The maximum displacement at a quarter of arch span was occurred when 50% of arch span was loaded and the displacement was larger than that of center of arch. Ratio of arch rise to arch span within 0.2∼-.3 seems to be appropriate for arch under radial or vertical load.

• Steel and Composite Structures
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• 제5권6호
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• pp.515-533
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• 2005

Buckling and post-buckling of cold-formed steel members are rather difficult to predict due to material and geometrical non-linearity. However, numerical techniques have reached a level of maturity such that many are now successfully undertaking ultimate strength analysis of cold-formed steel members. In numerical non-linear analysis, both geometrical and material imperfections, have to be estimated and properly used. They must be codified in terms of shape and magnitude. The presented paper represents a state-of-art report, including relevant results obtained by the authors and collected from literature, on that problem.

• 한국지반공학회논문집
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• 제20권8호
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• pp.193-203
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• 2004

표면이 거친 강성옹벽의 경우 뒷채움재에서 발생하는 아칭효과로 인해 옹벽에는 비선형의 토압분포가 작용하며, 아칭효과가 비선형의 토압분포에 미치는 영향은 옹벽의 변위 형태에 따라 달라진다. 따라서 강성옹벽에 작용하는 주동토압의 크기와 비선형의 토압분포를 정확하게 산정하기 위해서는 옹벽의 변위형태에 따라 달라지는 뒷채움재에 서 발생하는 실제적 인 파괴면 형상과 아칭효과를 고려해야만 한다. 따라서 본 연구에서는 강성옹벽이 저점을 중심으로 회전하는 경우에 뒷채움재에서의 아칭효과와 비선형의 파괴면 형상을 고려함으로써 비선형의 주동토압을 산정할 수 있는 토압산정식을 제안하였다. 이 과정에서 토압산정식이 수학적으로 복잡해지는 것을 피하기 위하여 뒷채움재에서 발생하는 비선형의 파괴면 형상은 4개의 직선으로 구성되는 가상의 파괴면으로 대체하였다. 그리고 제안식으로부터 구한 예측치를 기존의 모형시험 결과와 비교한 결과 제안식은 만족스런 토압 예측치를 제공하는 것으로 나타났다.

• 한국실내디자인학회논문집
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• 제20권1호
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• pp.14-23
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• 2011

The purpose of this study is to analyse the inclinations and expressions in contemporary architecture. Specially, we call this tendency and architectural movements as architectural metamorphosis. Metamorphosis in architecture present the core of the change of Forms and spirits in a change of outward shape and terrestrial identity. As in Ovid's extended dramatic poem of change and transformation, Metamorphoses, all Souls are deathless, and migrates from one form to another. Like these stories in Metamorphoses, Ovid tells the soul never dies, but leaps one form to anther, and can take any shape. So the architectural form, transformation and deformation in contemporary architecture means architectural sensations and cognitions can even approach the soul of form and shape under the transformation. The expressions and design strategies of metamorphosis in comtemporary architecture reveal continuous and sequential formations of space, linear structure with force and vector, rhythmical wavement and folding surface, lively wiggly flows of volumns and objects, and so on. Such qualities came from the periodical needs; separation of structure and surface, poly-surfacial movement, poly-sensual expression and experience, dematerialization and the dematerialized space, formless of non-formal architecture, digital architecture. Architecture of Metamorphosis is the ways and the needs of our period to overcome the static limits prohibits the liberal thoughts, to find the ways toward the opportunities and diversities and to unlock the imaginaire of the contemporary architecture.

• 한국정밀공학회지
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• 제27권11호
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• pp.17-23
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• 2010

Titanium alloy is one of the hard processing materials made by the traditional manufacturing method because of the excellent mechanical strength. Ablation of titanium alloy is investigated by using a femtosecond laser which is a regenerative amplified Ti:sapphire laser with 1kHz repetition rate, 184fs pulse duration time and 785nm wavelength. Experiments are carried out under various ablation conditions with different pulse overlap ratios for the rectangular shape and micro hole. Test results show that the ablation characteristic according to pulse overlap ratio of titanium alloy seems to be as non-linear type at the different zone of energy fluence. The optimal condition of rectangular shape processing is obtained at the laser peak power 1.3mW, pulse overlap ratio of 90%, beam gap of $1\;{\mu}m$. The micro hole has a good quality from the pulse overlap ratio of 99% at the same laser peak power. With the optimal processing condition, the fine rectangular shape and micro hole without burr and thermal damage are achieved.

• 제어로봇시스템학회논문지
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• 제18권6호
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• pp.562-570
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• 2012

This paper proposes a robust object tracking algorithm using object features and on-line learning based particle filter for mobile robots. Mobile robots with a side-view camera have problems as camera jitter, illumination change, object shape variation and occlusion in variety environments. In order to overcome these problems, color histogram and HOG descriptor are fused for efficient representation of an object. Particle filter is used for robust object tracking with on-line learning method IPCA in non-linear environment. The validity of the proposed algorithm is revealed via experiments with DBs acquired in variety environment. The experiments show that the accuracy performance of particle filter using combined color and shape information associated with online learning (92.4 %) is more robust than that of particle filter using only color information (71.1 %) or particle filter using shape and color information without on-line learning (90.3 %).

• 한국유체기계학회 논문집
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• 제13권6호
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• pp.42-50
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• 2010

The present analysis deals with a numerical procedure for optimizing the shape of elliptical dimples in a cooling channel. The three-dimensional Reynolds-averaged Navier-Stokes (RANS) analysis is employed in conjunction with the SST model for predictions of the turbulent flow and the heat transfer. Three non-dimensional geometric design variables, such as the ellipse dimple diameter ratio, ratio of the dimple depth to the average diameter, and ratio of the distance between dimples to the pitch are considered in the optimization. Twenty-one experimental points within design space are selected by Latin Hypercube Sampling. Each objective function values at these points are evaluated by RANS analysis and producing optimal point using surrogate model. The linear combination of heat transfer coefficient and friction loss related terms with a weighting factor is defined as the objective function. The results show that the optimized elliptical dimple shape improves considerably the heat transfer performance than the circular dimple shape.

• 한국방재학회 논문집
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• 제9권2호
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• pp.87-93
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• 2009

래버린스 위어는 마루부의 형상이 직선이 아닌 위어로 월류 폭을 증가시켜 월류량을 증대시키는 수공구조물이다. 최근 강우량 증가에 의한 댐 여수로의 개선 및 관개시설 및 운하관련 수공구조물 등 래버린스 위어의 활용범위는 다양하고 이에 관한 연구가 필요한 실정이다. 본 연구의 목적은 수리모형실험을 통해 삼각형 래버린스 위어 형상에 따른 수리특성 및 유량특성을 분석하여, 삼각형 래버린스 위어의 유량계수식을 제시하는데 있다. 본 연구에서 제시된 유량계수식은 상관계수, 잔차의 합, 평균절대오차율을 분석한 결과 적용성이 있는 것으로 나타나 댐의 여수로 및 관개시설 등 수공구조물 설계에 적용이 가능할 것이다.

• 대한기계학회논문집A
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• 제27권1호
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• pp.26-33
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• 2003

Based on detailed FE limit analyses, the present paper provides tractable approximations fer plastic limit pressure solutions fur axially through-wall-cracked pipe; axially (inner) surface-cracked pipe; circumferentially through-wall-cracked pipe; and circumferentially (inner) surface-cracked pipe. In particular, for surface crack problems, the effect of the crack shape, the semi-elliptical shape or the rectangular shape, on the limit pressure is quantified. Comparisons with existing analytical and empirical solutions show a large discrepancy in circumferential short through-wall cracks and in surface cracks (both axial and circumferential). Being based on detailed 3-D FE limit analysis, the present solutions are believed to be the most accurate, and thus to be valuable information not only for plastic collapse analysis of pressurised piping but also for estimating non-linear fracture mechanics parameters based on the reference stress approach.

• 한국전산구조공학회논문집
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• 제25권6호
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• pp.513-523
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• 2012

본 연구는 횡력저항시스템별로 프로토타입 모델을 선정하고 지진지역과 비정형성에 따른 내진성능 영향력을 검토하였다. 프로토타입 모델은 다이아그리드 시스템과 브레이스튜브 시스템 그리고 아웃리거 시스템을 선정하였다. 또한 각 횡력저항시스템별 평면 비틀림 각도를 $0^{\circ}$, $1^{\circ}$($1.5^{\circ}$), $2^{\circ}$($3^{\circ}$) 씩 변화하여 내진성능을 검토하였다. 지진지역은 강진지역(LA), 약진지역(Boston)을 선정하였다. 선형응답해석은 프로토타입 모델의 풍변위, 고유주기를 검토하였다. Non-Linear Response History(NLRH) 해석에서는 밑면전단력, 층간변위비를 검토하였다. 검토결과 다이아그리드 시스템과 브레이스튜브 시스템 그리고 아웃리거 시스템 모두 평면 비틀림 각도가 증가할수록 건물 전체의 강성이 줄어들었다. 또한 평면 비틀림 각도가 증가할수록 풍변위와 고유주기 결과가 증가하고 건물 전체의 강성이 줄어들어 밑면전단력이 감소하였다. 끝으로, NLRH 해석 결과 강진과 약진지역 모두 Tall Building Initiative(TBI)의 Maximum Considered Earthquake(MCE)수준의 층간변위비 제한값 0.045를 만족하여 허용범위내의 내진성능을 만족하고 있는 것으로 나타났다.