• 대한수학회논문집
• /
• 제37권4호
• /
• pp.1259-1267
• /
• 2022

In this paper we present a full circle approximation method using parametric polynomial curves with algebraic coefficients which are curvature continuous at both endpoints. Our method yields the n-th degree parametric polynomial curves which have a total number of 2n contacts with the full circle at both endpoints and the midpoint. The parametric polynomial approximants have algebraic coefficients involving rational numbers and radicals for degree higher than four. We obtain the exact Hausdorff distances between the circle and the approximation curves.

• 한국컴퓨터산업학회논문지
• /
• 제5권3호
• /
• pp.405-414
• /
• 2004

본 논문에서는 18-라운드 변형된 Feistel 구조를 갖는 128-bit 블록 암호알고리즘 Circle-g를 설계하고, 차분공격(differential cryptanalysis)과 선형공격(linear cryptanalysis)을 통해 안정성을 분석하였다. Circle-g의 f-함수는 2-라운드만에 완전 확산(diffusion)이 일어나도록 설계되었다. 이러한 우수한 확산효과로 인해 9-라운드 차분특성이 구성될 확률은 2^{-144}로, 12-라운드 선형특성이 구성될 확률은 2^{-144}로 분석되었다. 결과적으로 Circle-g는 128-bit 비밀키를 적용하였을 경우 12-라운드 이상이면 차분공격이나 선형공격은 전수(exhaustive)조사 방법보다 효율성이 떨어지는 것으로 분석되었다.

• Journal of Information Processing Systems
• /
• 제15권6호
• /
• pp.1422-1437
• /
• 2019

With the rapid development of the Internet and the Mobile Internet, social communication based on the network has become a life style for many people. WeChat is an online social platform, for about one billion users, therefore, it is meaningful to study the spreading and evolution mechanism of the rumor on the WeChat social circle. The Rumor was injected into the WeChat social circle by certain individuals, and the communication and the evolution occur among the nodes within the circle; after the refuting-rumor-information injected into the circle, subsequently,the density of four types of nodes, including the Susceptible, the Latent, the Infective, and the Recovery changes, which results in evolving the WeChat social circle system. In the study, the evolution characteristics of the four node types are analyzed, through construction of the evolution equation. The evolution process of the rumor injection and the refuting-rumor-information injection is simulated through the structure of the virtual social network, and the evolution laws of the four states are depicted by figures. The significant results from this study suggest that the spreading and evolving of the rumors are closely related to the nodes degree on the WeChat social circle.

• International Journal of Naval Architecture and Ocean Engineering
• /
• 제7권4호
• /
• pp.691-698
• /
• 2015

The hydrodynamic interaction forces and moments induced by the vicinity of bank on a passing vessel are known as wall effects. In this paper, the characteristics of interaction acting on a passing vessel in the proximity of a semi-circle bank wall are described and illustrated, and the effects of ship velocity, water depth and the lateral distance between vessel and semi-circle bank wall are discussed. For spacing between ship and semi-circle bank wall (SP) less than about 0.2 L and depth to ship's draft ratio (h/d) less than around 2.0, the ship-bank interaction effects increase steeply as h/d decreases. However, for spacing between ship and semi-circle bank wall (SP) more than about 0.3 L, the ship-bank interaction effects increase slowly as h/d decreases, regardless of the water depth. Also, for spacing between ship and semi-circle bank wall (SP) less than about 0.2 L, the hydrodynamic interaction effects acting on large vessel increase largely as ship velocity increases. In the meantime, for spacing between ship and semi-circle bank wall ($S_P$) more than 0.3 L, the interaction effects increase slowly as ship velocity increases.

• 한국컴퓨터정보학회논문지
• /
• 제21권6호
• /
• pp.21-28
• /
• 2016

Circle detection has long been studied as one of fundamental image processing applications. It is used in divers areas including industrial inspection, medial image analysis, radio astronomy data analysis, and other object recognition applications. The most widely used class of circle detection techniques is the circle Hough transform and its variants. Management of 3 dimensional parameter histogram used in these methods brings about spatial and temporal overheads, and a lot of studies have dealt the problem. This paper proposes a robust circle detection method using maximal symmetry property of circle. The basic idea is that if perpendicular bisectors of pairs of edges are accumulated in image space, center of circle is determined to be the location of highest accumulation. However, directly implementing the idea in image space requires a lot of calculations. The method of this paper reduces the number of calculations by mapping the perpendicular bisectors into parameter space, selecting small number of parameters, and mapping them inversely into image space. Test on 22 images shows the calculations of the proposed method is 0.056% calculations of the basic idea. The test images include simple circles, multiple circles with various sizes, concentric circles, and partially occluded circles. The proposed method detected circles in various situations successfully.

• 산업경영시스템학회지
• /
• 제42권3호
• /
• pp.52-60
• /
• 2019

This paper presents a numerically robust algorithm to construct a Voronoi diagram of circles in the plane. The circles are allowed to have intersections among them, but one circle cannot fully contain another circle. The Voronoi diagram is a tessellation of the plane into Voronoi regions of given circles. Each circle has its Voronoi region which is defined by a set of points in the plane closer to the circle than any other circles. The distance from a point p to a circle $c_i$ of center $p_i$ and radius $r_i$ is ${\parallel}p-p_i{\parallel}-r_i$, which is the closest Euclidean distance from p to the circle boundary. The proposed algorithm first constructs the point Voronoi diagram of centers of given circles, then it enlarges each point to the circle and expands its Voronoi region accordingly. This region-expansion process is done by local modifications and after completing this process for the whole circles the desired circle Voronoi diagram can be obtained. The proposed algorithm is numerically robust and we provide with a few examples to show its robustness. The algorithm runs in $O(n^2)$ time in the worst case and O(n) time on average where n is the number of the circles. The experiment shows that the region-expansion algorithm is robust and runs fast with strong linear time behavior.

• 대한수학회보
• /
• 제52권5호
• /
• pp.1433-1443
• /
• 2015

Catenoid and Riemann's minimal surface are foliated by circles, that is, they are union of circles. In $\mathbb{R}^3$, there is no other nonplanar example of circle-foliated minimal surfaces. In $\mathbb{R}^4$, the graph $G_c$ of w = c/z for real constant c and ${\zeta}{\in}\mathbb{C}{\backslash}\{0}$ is also foliated by circles. In this paper, we show that every circle-foliated minimal surface in $\mathbb{R}$ is either a catenoid or Riemann's minimal surface in some 3-dimensional Affine subspace or a graph surface $G_c$ in some 4-dimensional Affine subspace. We use the property that $G_c$ is circle-foliated to construct circle-foliated minimal surfaces in $S^4$ and $H^4$.

• 품질경영학회지
• /
• 제44권4호
• /
• pp.845-853
• /
• 2016

Purpose: This research is to find the general and somewhat prevailing problems in quality circle papers. Many quality circles try to benchmark awarded papers even though they may have common problems. By pointing out popular problems in papers, many quality circles hopefully could be guided to the right direction in working out improvement actions. Methods: Many papers awarded in national quality circle conferences are deeply analyzed to figure out common problems. 69 recent papers are analyzed step by step and the most important and frequently occurring problems in each step are indicated. Results: Many prevailing problems are found in each step of QC stories. Especially finding themes, Grasping status quo, Cause analysis, Setting targets, Development of and Implementing counter attacks are the most common areas that have problems. Conclusion: Some problems are already too popular to be recognized as problems. In this paper those problems are logically criticized and thereby right directions for future quality circle activities are proposed.

• 품질경영학회지
• /
• 제39권2호
• /
• pp.188-198
• /
• 2011

The purpose of this research is to identify the effect of quality circles activities upon quality circles performance and business performance. Empirical results indicate that quality circle activities influence on quality circles performance in both individual and enterprise level, Quality circles performance influences on not employment satisfaction but customer satisfaction, business performance (profitability and market values) of companies with quality circles is higher than that of companies without quality circles. In conclusion, quality circle activities influence on quality circles performance that effect on business performance.

• 한국안광학회지
• /
• 제16권2호
• /
• pp.147-157
• /
• 2011

목적: 본 연구에서는 써클 콘택트렌즈의 착용 실태를 조사하고, 임상 적용 시 동일재질의 일반 소프트 콘택트렌즈 착용 시의 순목횟수, 비침입성 눈물막 파괴시간 및 렌즈 표면의 차이를 비교하여 착색 여부에 따른 차이를 알아보고자 하였다. 방법: 80명을 대상으로 써클 콘택트렌즈의 착용 실태를 알아보았으며, 20대 20안을 대상으로 하여 동일한 재질 및 파라미터의 일반 소프트 콘택트렌즈와 써클 콘택트렌즈를 각각 5일 동안 착용시킨 후 순목 횟수, 비 침입성 눈물막 파괴시간을 측정하였다. 또한, 주사전자현미경을 이용하여 렌즈의 표면을 관찰하였다. 결과: 써클 콘택트렌즈 교체의 주요 원인이 불편감이라고 답한 응답자가 50%에 달하였으며, 67%가 하루에 6시간 이상을 착용하는 것으로 나타났다. 콘택트렌즈 착용 1일, 3일, 5일째에 눈물막이 안정화된 시점인 착용 30분 후와 3시간 후의 순목 횟수는 두 종류의 렌즈 모두 착용 기간이 증가할수록 증가하는 경향을 보였다. 3일째, 5일째 착용 3시간 후에는 써클 콘택트렌즈 착용 시와 소프트 콘택트렌즈 착용 시의 순목 횟수가 통계적으로 유의한 차이가 나타났다. 콘택트렌즈를 착용한 상태에서의 비침입성 눈물막 파괴시간은 착용 1일째 30분 후 소프트 콘택트렌즈 착용 시는 6.0 초, 써클 콘택트렌즈는 3.7 초로 통계적으로 유의한 차이가 있었다. 착용 3시간 후에도 두 렌즈 사이의 비침입성 눈물막 파괴시간에는 통계적으로 유의한 차이가 있었으며, 착용 3일째와 5일째도 마찬가지였다. 써클 콘택트렌즈와 일반 소프트 콘택트렌즈의 전후면과 써클 콘택트렌즈 후면의 표면조도(surface roughness)는 동일했으나 써클 콘택트렌즈는 착색된 부분인 렌즈 전면부는 균일하지 않고 요철이 많았다. 결론: 써클 콘택트렌즈의 표면 차이가 렌즈 착용 시 습윤성의 차이를 야기하였을 것으로 보이며 그로 인하여 불편감을 느끼게 되었을 것으로 생각되어졌다. 본 연구 결과로 착색으로 인한 써클 콘택트렌즈와 일반 소프트 콘택트렌즈의 차이를 밝혔으므로 건강한 써클 콘택트렌즈의 착용에 도움이 될 수 있으리라 여겨진다.