• Journal of Aerospace System Engineering
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• v.18 no.3
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• pp.1-7
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• 2024

The utilization of Unmanned Aerial Vehicles (UAVs) is expanding in various industries such as logistics, manufacturing, and transportation. However, to operate a large number of UAVs, it is imperative to first plan a secure and efficient self-configuring communication network for UAVs. In this study, we proposed a method for planning a secure and efficient UAV self-configuring communication network using Voronoi diagrams in the following three steps: 1) generating Voronoi diagrams using obstacles, 2) selecting obstacles to consider for path generation, and 3) planning the optimal path and outputting the path. The real-time feasibility of using the proposed method for planning optimal communication paths for a realistic number of UAVs was experimentally validated.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2005.05a
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• pp.179-187
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• 2005

In this paper, we consider the problem of regrouping a number of service sites into a smaller number of service sites called centers. Each service site is represented as a point in the plane and has an associated value of service demand. We aim to group the sites so that each group has the balanced service demand and the sum of distances from the sites in the group to their corresponding center is minimized. To solve this problem, we propose a hybrid genetic algorithm that is combined with Voronoi diagrams. We provide a variety of experimental results by changing the weights of the two factors: service demands and distances. Our hybrid algorithm finds better solutions in a shorter computation time in comparison with a pure genetic algorithm.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.24 no.1
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• pp.98-102
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• 2015

This paper proposes an autonomous navigation method for a nonholonomic mobile robot, based on the generalized Voronoi diagram (GVD). We define the look-ahead point for a given motion constraint to determine the direction of motion, which solves the problem of a minimum turning radius for the real nonholonomic mobile robot. This method can be used to direct the robot to explore an unknown environment and construct smooth feedback curves for the nonholonomic robot. As the trajectories can be smoothed, the position of the robot can be stabilized in the plane. The simulation results are presented to verify the performance of the proposed methods for the nonholonomic mobile robot. Furthermore, this approach is worth drawing on the experience of any other mobile robots.

• Korean Journal of Computational Design and Engineering
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• v.15 no.1
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• pp.33-42
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• 2010

In this study, new medial surface calculation methods using Voronoi diagrams are investigated for the point samples extracted on closed surface models. The medial surface is defined by the closure of all points having more than one closest point on the shape boundary. It is a one of essential geometric information in 3D and can be used in many areas such as 3D shape analysis, dimension reduction, freeform shape deformation, image processing, computer vision, FEM analysis, etc. In industrial parts, the idealized solid parts and shell shapes including sharp edges and vertices are frequently used. Other medial surface extraction methods using Voronoi diagram have inherent separation and branch problems, so that they are not appropriate to the sharp edged objects and have difficulties to be applied to industrial parts. In addition, the branched surfaces on sharp edges in shell shapes should be eliminated to obtain representative medial shapes. In order to avoid separation and branch problems, the new approach by analyzing the shapes and specially sampling on surfaces has been developed.

• Journal of Korea Multimedia Society
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• v.3 no.3
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• pp.298-308
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• 2000

We present an efficient algorithm for finding the sequence of extreme vortices of a moving regular convex polyhedron of with respect to a fixed plane H.. The algorithm utilizes the spherical Voronoi diagram that results from the outward unit normal vectors nF$_{i}$ 's of faces of P. It is well-known that the Voronoi diagram of n sites in the plane can be computed in 0(nlogn) time, and this bound is optimal. However. exploiting the convexity of P, we are able to construct the spherical Voronoi diagram of nF$_{i}$ ,'s in O(n) time. Using the spherical Voronoi diagram, we show that an extreme vertex problem can be transformed to a spherical point location problem. The extreme vertex problem can be solved in O(logn) time after O(n) time and space preprocessing. Moreover, the sequence of extreme vertices of a moving regular convex polyhedron with respect to H can be found in (equation omitted) time, where m$^{j}$ $_{k}$ (1$\leq$j$\leq$s) is the number of edges of a spherical Voronoi region sreg(equation omitted) such that (equation omitted) gives one or more extreme vertices.

• Spatial Information Research
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• v.15 no.3
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• pp.203-218
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• 2007

The purpose of this article is to set up the scientific and reasonable norm of location and service area determination instead of the pro-administrative lacking availability, so as to propose more practical and reasonable standard of space unit for the location of facilities. This article has accepted the method of Voronoi Diagram as a new scientific and reasonable criteria. The article chooses and realizes a model that can propose a new service area, transform and apply to improve its reality, and assesses which has more reality and compatibility by comparing the models. The result from this procedure can be adapted in objectification of the service area determination and formation of the standard space unit.

• Proceedings of the Korean Information Science Society Conference
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• 2006.10a
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• pp.505-510
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• 2006

This paper presents an improved algorithm for constructing the city Voronoi diagram under the Euclidean metric given a transportation network consisting of roads having a constant number of speeds and orientations. The algorithm applies the continuous Dijkstra paradigm and its efficiency follows from new geometric insights that are first observed in this paper.

• 제어로봇시스템학회:학술대회논문집
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• 2003.10a
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• pp.174-179
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• 2003

Through the simultaneous localization and map building (SLAM) technique, a robot can create maps about its unknown environment while it continuously localizes its position. Grid maps and feature maps have been widely used for SLAM together with application of probability methods and POMDP (partially observed Markov decision process). But this approach based on grid maps suffers from enormous computational burden. Topological maps, however, have drawn more attention these days because they are compact, provide natural interfaces, and are easily applicable to path planning in comparison with grid maps. Some topological SLAM techniques like GVG (generalized Voronoi diagram) were introduced, but it enables the robot to decide only whether the current position is part of GVG branch or not in the GVG algorithm. In this paper, therefore, to overcome these problems, we present a method for updating a global topological map from the local topological maps. These local topological maps are created through a labeled Voronoi diagram algorithm from the local grid map built based on the sensor information at the current robot position. And the nodes of a local topological map can be utilized as the features of the environment because it is robust in light of visibility problem. The geometric information of the feature is applied to the extended Kalman filter and the SLAM in the indoor environment is accomplished. A series of simulations have been conducted using a two-wheeled mobile robot equipped with a laser scanner. It is shown that the proposed scheme can be applied relatively well.

• Proceedings of the Korean Information Science Society Conference
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• 2004.04a
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• pp.949-951
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• 2004

본 논문에서는 유클리드 평면상에 도로망이 주어져 있어서 여행자들이 그 도로들을 이용하여 더욱 빠르게 이동할 수 있을 경우를 가정한다. 이 때, 두 점 사이의 거리는 기하학적 직선거리가 아닌 주어진 도로들을 이용하여 두 점 사이를 이동할 때 필요한 최소시간으로 측정한다. 본 논문에서는 이러한 새로운 거리 척도를 고려할 때에 보로노이 다이어그램이 어떤 특성을 갖는 가를 연구하며 그것을 이용하여 보로노이 다이어그램을 효율적으로 계산하는 알고리즘을 제시한다. 이알고리즘은 O(nm$^2$logn＋m$^3$logm)의 시간과 O(m(n + m))의 공간을 필요로 한다. 이 때, n은 주어진 싸이트의 개수이고 m은 주어 진 도로의 개수이다.

• Korean Journal of Materials Research
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• v.15 no.2
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• pp.85-88
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• 2005

[ $W-15wt.\%$ ] Cu nanocomposite powders are fabricated by ball-milling and subsequent hydrogen-reduction. The compacted parts of $W-15wt.\%Cu$ nanocomposite powders were sintered at $1200^{\circ}C$ for 1 h with various heating rates of 5 and $20^{\circ}C/min$. The homogeneity of the sintered microstructures was evaluated through homogeneity index by the standard deviation of Victor's hardness test. The W-W contiguities were calculated by using Voronoi diagrams. The sintered microstructure with the heating rate of $20^{\circ}C/min$ was more homogeneous and had lower W-W contiguity than that of $5^{\circ}C/min$. The microstructural homogeneity was directly related to the W-W contiguity. Thermal conductivity of the sintered parts with the heating rate of $20^{\circ}C/min$ was higher than that with heating rate of $5^{\circ}C/min$. This phenomenon indicates that the thermal conductivity is affected by the W-W contiguity resulting from the homogeneity of the sintered microstructure.