• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.5B
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• pp.463-472
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• 2009

The aim of this study is to examine the effect of beach curvature on wave fields in coastal area with Submerged Breakwaters using the 3D numerical model that is able to simulate directly interaction of WAve Structure Sandy beach (LES-WASS-3D). At first, the adopted model was validated through the comparison with an existing experimental data and showed fairly nice agreement. And then, the numerical simulations have been performed to investigate the effect of according to the variation of beach curvature. Based on the numerical results, the wave height, mean surface elevation, mean flow around submerged breakwaters and longshore distributions of run-up height have been discussed in relation to the variation of beach curvature.

• Proceedings of the Korea Information Processing Society Conference
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• 2015.10a
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• pp.1579-1580
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• 2015

본 논문에서는 3차원 메쉬 모델의 중요 영역을 표현하는 메쉬 돌출맵(mesh saliency map)을 생성하기 위하여 다중 스케일 평균 곡률 (multi-scale mean curvature)을 기반으로 정의된 전역 희소치(global rarity)를 이용하는 방법을 제안한다. 제안 방법에서는 우선, 메쉬 모델의 지역 영역 특성을 정의하기 위하여 기존 관련 연구들에서 많이 사용하고 있는 가우시안 가중치 평균곡률(Gaussian-weighted mean curvature)을 5단계 서로 다른 스케일에서 정의하고, 메쉬의 각 정점(vertex)에 대하여 중심주변 연산자(center-surround operator)를 적용하여 5단계 지역 돌출특성(local saliency)을 정의한다. 주어진 메쉬 모델의 전역 희소치를 구하기 위하여 메쉬의 모든 정점쌍 (vertex pair)에 대하여 5단계 지역 돌출 특성 공간에서의 거리를 계산하고, 각 정점별로 5단계 지역 돌출 특성 공간에서의 다른 정점과의 거리의 합으로 전역 희소치를 정의한다. 이러한 전역 희소치를 각 정점의 메쉬 돌출치로 정의한다. 서로 다른 형태의 3차원 모델에 대하여 제안방법에 의한 메쉬 돌출맵과 지역 특성만을 고려한 기존 메쉬 돌출맵을 생성하여 중요 영역 표현 결과를 비교 분석한다.

• The KIPS Transactions:PartB
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• v.11B no.3
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• pp.297-302
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• 2004

In this paper, the 3-D shape description for the objects with the cone ridge and valley surfaces, and the corresponding threshold value selection for surface classification are considered. The existing method based on the mean and Gaussian curvatures(H and K) of differential geometries cannot properly describe cone primitives, which are some of the most common objects in the real world. Also the existing method for surface classification based on the sign values of H and K has Problems in practical applications. For this, cone surface shapes are classified cone ridges and cone valleys are derived from surfaces using the fact that H values are constant case of cylinder surfaces and variable for cone surfaces, respectively. Also threshold value selection for surface classification from a statistical point of view is proposed. The effectiveness of the proposed methods are verified through experiments.

• Journal of Korea Multimedia Society
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• v.8 no.1
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• pp.34-45
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• 2005

In this paper, a novel implementation of a person verification system based on depth-weighted Hausdorff distance (DWHD) using the surface curvature of the face is proposed. The definition of Hausdorff distance is a measure of the correspondence of two point sets. The approach works by finding the nose tip that has a protrusion shape on the face. In feature recognition of 3D face image, one has to take into consideration the orientated frontal posture to normalize after extracting face area from original image. The binary images are extracted by using the threshold values for the curvature value of surface for the person which has differential depth and surface characteristic information. The proposed DWHD measure for comparing two pixel sets were used, because it is simple and robust. In the experimental results, the minimum curvature which has low pixel distribution achieves recognition rate of 98% among the proposed methods.

• Journal of KIISE:Software and Applications
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• v.31 no.5
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• pp.605-616
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• 2004

A new practical implementation of a facial verification system using cumulative histogram of surface curvatures for the local and contour line areas is proposed, in this paper. The approach works by finding the nose tip that has a protrusion shape on the face. In feature recognition of 3D face images, one has to take into consideration the orientated frontal posture to normalize after extracting face area from the original image. The feature vectors are extracted by using the cumulative histogram which is calculated from the curvature of surface for the contour line areas: 20, 30 and 40, and nose, mouth and eyes regions, which has depth and surface characteristic information. The L1 measure for comparing two feature vectors were used, because it was simple and robust. In the experimental results, the maximum curvature achieved recognition rate of 96% among the proposed methods.

• Journal of Digital Convergence
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• v.11 no.1
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• pp.315-320
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• 2013

We have investigated the variation of spherical aberration of the anterior and posterior surface in a Korean sample population with various age between 20 to 71 years old. We used Pentacam (Oculus Inc., Germany) to measure the corneal radius, asphericity, and spherical aberration of 290 patients with normal cornea. There were negative correlation between corneal anterior radius and spherical aberration(r = -0.22, p<0.0001), and, there were negative correlation between corneal posterior radius and spherical aberration(r=-0.27, p < 0.0001). There were positive correlation between anterior asphericity and spherical aberration(r = 0.24, p < 0.0001), however there were negative correlation between posterior asphericity and spherical aberration(r = -0.17, p=0.00288).The average of anterior spherical aberration and posterior spherical aberration was $0.482{\pm}0.099{\mu}m$ and $-0.098{\pm}0.029{\mu}m$. The average of spherical aberration was $0.385{\pm}0.097{\mu}m$. There were significant positive correlations between anterior spherical aberration and age(r = 0.227, p<0.0001), and there were positive correlations between posterior aberration and age(r = 0.349, p<0.0001). It is considered that this data can be used as basic information for furture studies for improving the quality of vision of modern human and, through the analysis of the spherical aberration of cornea was to provide a better understanding of the optical part of the Korean's eye.

• Journal of Korean Ophthalmic Optics Society
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• v.1 no.2
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• pp.71-76
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• 1996

As the results of measurement of the radius of corneal curvature with keratometer, for the right eye of 91 male adults, horizontal radius is 7.16 mm to 8.49 mm and vertical radius is 7.03 mm to 8.34 mm, and for the left eye of male adults, horizontal radius is 7.10 mm to 8.48 mm and vertical radius is 7.01 mm to 8.24 mm. In case of 61 female adults, horizontal radius is 7.16 mm to 8.45 mm, vertical radius 7.11 mm to 8.18 mm for the right eye, and horizontal radius 7.15 mm 108.43 mm and vertical radius 7.01 mm to 8.26 mm for the left eye. The mean value of radius of corneal curvature is 7.74 mm for male and 7.69 mm for female. Also the mean value of horizontal radius is 7.79 mm and vertical radius is 7.64 mm. Overall mean value of the radius of corneal curvature is 7.71 mm that is corresponded to Gullstrand's eye. The horizontal radius is 0.15 mm bigger than vertical radius.

• The KIPS Transactions:PartB
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• v.14B no.4
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• pp.241-248
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• 2007

An L-curve corner detection method is proposed for the determination of the regularization parameter in optical flow estimation. The method locates the positive peak whose curvature difference from the just right-hand negative valley is the maximum in the curvature plot of the L-curve. while the existing curvature-method simply finds the maximum in the plot. Experimental results show that RMSE of the estimated optical flow is greater only by 0.02 pixels-per-frame than the least in the average sense. The proposed method is also compared with an existing curvature-method and the adaptive pruning method, resulting in the optical flow estimation closest to the least RMSE.

• Journal of Korea Multimedia Society
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• v.11 no.4
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• pp.423-433
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• 2008

The surface curvatures extracted from the face contain the most important personal facial information. In particular, the face shape using the depth information represents personal features in detail. In this paper, we develop a method for recognizing the range face images by combining the multiple face regions using fuzzy integral. For the proposed approach, the first step tries to find the nose tip that has a protrusion shape on the face from the extracted face area and has to take into consideration of the orientated frontal posture to normalize. Multiple areas are extracted by the depth threshold values from reference point, nose tip. And then, we calculate the curvature features: principal curvature, gaussian curvature, and mean curvature for each region. The second step of approach concerns the application of eigenface and Linear Discriminant Analysis(LDA) method to reduce the dimension and classify. In the last step, the aggregation of the individual classifiers using the fuzzy integral is explained for each region. In the experimental results, using the depth threshold value 40 (DT40) show the highest recognition rate among the regions, and the maximum curvature achieves 98% recognition rate, incase of fuzzy integral.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.11 no.1
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• pp.117-124
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• 1991

Based on the momentum equation for the flow in a stream bend, the force per unit area which the flow exerts on the outer of a bend is directly proportional to a certain curvature coefficient, $C{\alpha}$. This coefficient is dependent on the ratio of bend radius(R) to flow width(W), as well as on the coefficient of dynamic bedload friction, $tan{\alpha}$. According to the results of the data analysis for the downstrream at the Han river, the range of R/w values is between 2.0 and 4.0. Exploring the variations of $C{\alpha}$ with R/w values a functional relationship which, for the known values of $tan{\alpha}$, shows maximum values of $C{\alpha}$ for R/w values between 2.21 and 4.42 in 1963, while in 1981 its values lied between 1.93 and 3.54.