• 정보보호학회논문지
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• 제32권4호
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• pp.617-628
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• 2022

Ascon은 2015년부터 진행되고 있는 NIST 경량암호 공모사업의 최종 라운드 후보 중 하나이며, 해시 모드 Ascon-Hash와 Ascon-Xof를 지원한다. 본 논문에서는 Ascon-Hash의 충돌 공격을 위한 MILP 모델을 개발하고, 해당 모델을 통해 양자 컴퓨팅 환경에서 활용 가능한 차분 경로를 탐색한다. 또한, 탐색한 차분 경로를 이용하여 양자 컴퓨터를 사용할 수 있는 공격자가 3-라운드 Ascon-Hash의 양자 free-start 충돌쌍을 찾을 수 있는 알고리즘을 제시한다. 본 공격은 Ascon-Hash에 대한 충돌 공격을 양자 컴퓨팅 환경에서 최초로 분석했다는 점에서 유의미하다.

• International Journal of Control, Automation, and Systems
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• 제2권1호
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• pp.107-117
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• 2004

A new algorithm for planning a collision-free path based on an algebraic curve as well as the concept of path space is developed. Robot path planning has so far been concerned with generating a single collision-free path connecting two specified points in a given robot workspace with appropriate constraints. In this paper, a novel concept of path space (PS) is introduced. A PS is a set of points that represent a connection between two points in Euclidean metric space. A geometry mapping (GM) for the systematic construction of path space is also developed. A GM based on the 2$^{nd}$ order base curve, specifically Bezier curve of order two is investigated for the construction of PS and for collision-free path planning. The Bezier curve of order two consists of three vertices that are the start, S, the goal, G, and the middle vertex. The middle vertex is used to control the shape of the curve, and the origin of the local coordinate (p, $\theta$) is set at the centre of S and G. The extreme locus of the base curve should cover the entire area of actual workspace (AWS). The area defined by the extreme locus of the path is defined as quadratic workspace (QWS). The interference of the path with obstacles creates images in the PS. The clear areas of the PS that are not mapped by obstacle images identify collision-free paths. Hence, the PS approach converts path planning in Euclidean space into a point selection problem in path space. This also makes it possible to impose additional constraints such as determining the shortest path or the safest path in the search of the collision-free path. The QWS GM algorithm is implemented on various computer systems. Simulations are carried out to measure performance of the algorithm and show the execution time in the range of 0.0008 ~ 0.0014 sec.

• 천문학논총
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• 제11권1호
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• pp.125-137
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• 1996

The collision of two particles in the accretion disk may lead to be a mechanism of heat generation. By using hydrodynamic equations, the mean free path, the collision frequency and the deflection angle due to the collision of the particles are derived as a function of the mass accretion rate. The mean free path seems to be a smaller fraction compared to the dimension parameter of the system. The radiative flux in the disk is obtained under the influence of the collision of the particles.

• 대한산업공학회지
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• 제22권4호
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• pp.579-588
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• 1996

The purpose of this paper is to develop a method of Collision-Free Path Planning (CFPP) for an articulated robot. First, the configuration of the robot is built by a set of robot joint angles derived from robot inverse kinematics. The joint space, that is made of the joint angle set, forms a Configuration space (Cspcce). Obstacles in the robot workcell are also transformed into the Cobstacles using slice projection method. Actually the Cobstacles means the configurations of the robot causing collision with obstacles. Secondly, a connected graph, a kind of roadmap, is constructed by the free configurations in the Cspace, where the free configurations are randomly sampled from a free Cspace immune from the collision. Thirdly, robot paths are optimally determinant in the connected graph. A path searching algorithm based on $A^*$ is employed in determining the paths. Finally, the whole procedures for the CFPP method are shown for a proper articulated robot as an illustrative example.

• 대한전자공학회논문지
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• 제26권10호
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• pp.1480-1487
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• 1989

An approach for collision-free coordination plan along designated paths of two robots in a common workspace is presented. Specifically, a notion of coordination space is introduced to visualize all the collision-free coordinations for the two robots. Then a problem is formulated and resolved in order to find the optimal coordination curve which trade off between safety of two robots and difference of degree of accomplishment.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1987년도 한국자동제어학술회의논문집(한일합동학술편); 한국과학기술대학, 충남; 16-17 Oct. 1987
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• pp.915-920
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• 1987

When a task requires two robot arms to move in a cooperative manner sharing a common workspace, potential collision exists between the two robot arm . In this paper, a novel approach for collision-free trajectory planning along paths of two SCARA-type robot arms is presented. Specifically, in order to describe potential collision between the links of two moving robot arms along the designated paths, an explicit form of "Virtual Obstacle" is adopted, according to which links of one robot arm are made to grow while the other robot arm is forced to shrink as a point on the path. Then, a notion of "Coordination Chart" is introduced to visualize the collision-free relationship of two trajectories.of two trajectories.

• 제어로봇시스템학회논문지
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• 제3권5호
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• pp.461-468
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• 1997

A real-time collision-free trajectory control method for dual arm robot system is proposed. The proposed method is composed of two stages; one is to calculate the minimum distance between two robot arms and the other is to control the trajectories of the robots to ensure collision-free motions. The calculation of minimum distance between two robots is, also, composed of two steps. To reduce the calculation time, we, first, apply a simple modeling technique to the robots arms and determine the interested part of the robot arms. Next, we apply more precise modeling techniques for the part to calculate the minimum distance. Simulation results show that the whole algorithm runs within 0.05 second using Pentium 100MHz PC.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.979-983
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• 2001

We develop a new method of simultaneous optimization of trajectory and shape of redundant flexible manipulators for collision-free utilizing the B-spline function and a mathematical programming method We adopt an approximate flexible manipulator model which consists of rigid bar elements and spring elements. We use B-spline function for determining the approximate trajectory and the expressions of the outline of obstacles. The used total performance index consists of 2 performance indices. The first is the driving energy, and the second is the trajectory deviation which is caused by the approximate modeling for the flexible manipulator. We design optimal collision-free trajectory of flexible manipulators by searching optimum positions of the control points for B-spline approximation which minimize the performance index subject to constraint condition for collision-free. Some examinations through numerical examples show the effectiveness of the method

• ETRI Journal
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• 제43권4호
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• pp.580-593
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• 2021

When operating in confined spaces or near obstacles, collision-free path planning is an essential requirement for autonomous exploration in unknown environments. This study presents an autonomous exploration technique using a carefully designed collision-free local planner. Using LiDAR range measurements, a local end-point selection method is designed, and the path is generated from the current position to the selected end-point. The generated path showed the consistent collision-free path in real-time by adopting the Euclidean signed distance field-based grid-search method. The results consistently demonstrated the safety and reliability of the proposed path-planning method. Real-world experiments are conducted in three different mines, demonstrating successful autonomous exploration flights in environment with various structural conditions. The results showed the high capability of the proposed flight autonomy framework for lightweight aerial robot systems. In addition, our drone performed an autonomous mission in the tunnel circuit competition (Phase 1) of the DARPA Subterranean Challenge.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 1989년도 한국자동제어학술회의논문집; Seoul, Korea; 27-28 Oct. 1989
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• pp.627-634
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• 1989

A collision-free trajectory planning algorithm using the iterative learning concept is proposed for dual robot arms in a 3-D workspace to accurately follow their specified paths with constant velocities. Specifically, a collision-free trajectory minimizing the trajectory error is obtained first by employing the linear programming technique. Then the total operating time is iteratively adjusted based on the maximum trajectory error of the previous iteration so that the collision-free trajectory has no deviation from the specified path and also the operating time is near-minimal.