• 한국멀티미디어학회논문지
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• 제18권11호
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• pp.1302-1312
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• 2015

Recent research has been devoted and focused on detecting pedestrian and vehicle in intelligent vehicles except for the vulnerable road user(VRUS). In this paper suggest a new projection method which has robustness for rotation invariant and reducing dimensionality for each cell from original image to detect two-wheeler. We applied new weighting values which are calculated by maximum curvature containing very important object shape features and uniform local binary pattern to remove the noise. This paper considered the Adaboost algorithm to make a strong classification from weak classification. Experiment results show that the new approach gives higher detection accuracy than of the conventional method.

• 대한수학회보
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• 제46권2호
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• pp.255-261
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• 2009

In this paper, we shall prove several results concerning Ricci curvature of a Riemannian manifold (M, g) := (SU(2), g) with an arbitrary given left invariant metric g. First of all, we obtain the maximum (resp. minimum) of {r(X) := Ric(X,X) | ${||X||}_g$ = 1,X ${\in}$ X(M)}, where Ric is the Ricci tensor field on (M, g), and then get a necessary and sufficient condition for the Levi-Civita connection ${\nabla}$ on the manifold (M, g) to be projectively flat. Furthermore, we obtain a necessary and sufficient condition for the Ricci curvature r(X) to be always positive (resp. negative), independently of the choice of unit vector field X.

• Steel and Composite Structures
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• 제4권3호
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• pp.227-246
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• 2004

This paper presents a moment-curvature method that accounts for the strength deterioration of steel at elevated temperature in estimating the response of steel beams exposed to fire. A modification to the EC4 method is proposed for a better estimation of the temperature distribution in the steel beam supporting a concrete slab. The accuracy of the proposed method is verified by comparing the results with established test results and the nonlinear finite element analysis results. The beam failure criterion based on a maximum strain of 0.02 is proposed to assess the limiting temperature as compared to the traditional criteria that rely on deflection limit or deflection rate. Extensive studies carried out on steel beams with various span lengths, load ratios, beam sizes and loading types show that the proposed failure criterion gives consistent results when compared to nonlinear finite element results.

• Steel and Composite Structures
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• 제20권5호
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• pp.983-997
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• 2016

The aim of this study is to investigate the impact behavior and impact-induced damage of sandwich composites made of E-glass/epoxy face sheets and PVC foam. The studies were carried out on square flat and curved sandwich panels with two different radius of curvatures. Impact tests were performed under impact energies of 10 J, 25 J and 80 J using an instrumented drop-weight machine. Contact force and displacement versus time and contact force- displacement graphs of sandwich panels were presented to determine the panel response. Through these graphs, the energy absorbing capacity of the sandwich panels was determined. The impact responses and failure modes of flat and curved sandwich panels were compared and the effect of curvature on sandwich composite panel was demonstrated. Testing has shown that the maximum contact force decrease while displacement increases with increasing of panel curvature and curved panels exhibits mixed failure mode, with cylindrical and cone cracking.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2006년도 춘계학술대회 논문집
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• pp.241-242
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• 2006

Spherical glass lenses are used in many optical industries. The curvature, eccentricity and height of a tool affect the surface roughness and curvature of lenses. The purpose of this study is the development and performance of a self-diagnostication ultra-precision lens polishing machine. In this paper, structure analysis is performed to reduce maximum displacement and to maintain outside the resonance region by CATIA V5. A spherical center setting gage is developed to increase accuracy of the manufactured lenses. The surface roughness, curvature and thickness of the manufactured lenses are measured and studied.

• 한국기계가공학회지
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• 제9권1호
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• pp.74-80
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• 2010

The purpose of reverse engineering design using 3D measurement data is an accurate reconstruction of real body. In oder to accomplish this object, it is important that creating exact extracting edges should be studying out first of all. This study used edge-based method to find out edge point from the measuring point data. The characteristics are analysed using the mean curvature block method on the fitting NURBS curve and defined edges through block removal condition. The results showed that only using the NURBS curve of maximum curvature analysis to define correct edge of real geometry is limited, but this segmentation approach provides simplified necessary condition for edge classification, and an effectiveness to classify a straight line, curves and fillets etc.

• 한국정보과학회논문지:소프트웨어및응용
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• 제33권1호
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• pp.130-137
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• 2006

얼굴의 깊이 정보는 개개인의 특성을 잘 나타내며, 특히 표면 곡률은 곡선으로 이루어진 사람들의 얼굴 표면을 특정 짓는 아주 중요한 정보이다. 3차원 물체 인식에서 표면 형태 특성을 잘 나타내는 곡률 정보와 계산량을 줄일 수 있는 차원 감소의 그룹 분할 투영 벡터 방법을 이용한 3차원 얼굴 인식 방법을 제안한다. 얼굴의 표면 곡률을 구하여, 이로부터 최대 곡률 및 최소 곡률에 대한 그룹 분할 투영 벡터를 적용하여 인식 하였다. 인식 결과 최소 곡률에 의한 투영 벡터 방법이 가장 높은 인식률을 나타내었다.

• Structural Engineering and Mechanics
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• 제55권3호
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• pp.461-472
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• 2015

The existence of initial imperfections in manufacturing or assembly of double-layer space structures having hundreds or thousands of members is inevitable. Many of the imperfections, such as the initial curvature of the members and residual stresses in members, are all random in nature. In this paper, the probabilistic effect of initial curvature imperfections in the load bearing capacity of double-layer grid space structures with different types of supports have been investigated. First, for the initial curvature imperfection of each member, a random number is generated from a gamma distribution. Then, by employing the same probabilistic model, the imperfections are randomly distributed amongst the members of the structure. Afterwards, the collapse behavior and the ultimate bearing capacity of the structure are determined by using nonlinear push down analysis and this procedure is frequently repeated. Ultimately, based on the maximum values of bearing capacity acquired from the analysis of different samples, structure's reliability is obtained by using Monte Carlo simulation method. The results show the sensitivity of the collapse behavior of double-layer grid space structures to the random distribution of initial imperfections and supports type.

• 대한기계학회논문집A
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• 제24권4호
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• pp.963-971
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• 2000

Gerotor is a planar mechanism consisting of a rotor and lobes which form a closed space, namely a chamber. As active contact points between a rotor and lobes are subjected to very high contact stresses, wear in one or both of the rotor and lobe cannot be avoided. Therefore, in the design of Gerotor used in hydraulic motors a compromise between high torque output and contact stress is of great importance and a thorough analysis of design parameters should be conducted to achieve this compromise. In this study, a contact point is modelled as a linear spring in consideration of equivalent curvature to analyze the contact stress. As the contact stress calculation in this problem is a statically indeterminate type, a numerical iterative scheme has been adopted to obtain the solution. To fully understand the influence of design parameters on the contact stress, the relationship between pressure force, equivalent curvature, contact force and contact stress are analyzed. It is shown that the equivalent curvature of the contact point is a dominant factor that affects the maximum contact stress.

• 소성∙가공
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• 제26권6호
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• pp.341-347
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• 2017

Flexibly-reconfigurable roll forming (FRRF) is a novel sheet metal forming technology conducive to produce multi-curvature surfaces by controlling strain distribution along longitudinal direction. Reconfigurable rollers could be arranged to implement a kind of punch die set. By utilizing these reconfigurable rollers, desired curved surface can be formed. In FRRF process, three-dimensional surface is formed from two-dimensional curve. Thus, it is difficult to predict the forming result. In this study, a regression analysis was suggested to construct a predictive model for a longitudinal curvature of FRRF process. To facilitate investigation, input parameters affecting the longitudinal curvature of FRRF were determined as maximum compression value, curvature radius in the transverse direction, and initial blank width. Three-factor three-level full factorial experimental design was utilized and 27 experiments using FRRF apparatus were performed to obtain sample data of the regression model. Regression analysis was carried out using experimental results as sample data. The model used for regression analysis was a quadratic nonlinear regression model. Determination factor and root mean square root error were calculated to confirm the conformity of this model. Through goodness of fit test, this regression predictive model was verified.