• Journal of KIISE:Computer Systems and Theory
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• v.35 no.3
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• pp.133-140
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• 2008

This paper proposes an effective k-D tree traversal algorithm for ray tracing on a GPU. The previous k-D tree traverse algorithm based on GPU uses bottom-up searching from a leaf to the root after failing to find the ray intersected primitive in the leaf node. During the bottom-up search the algorithm decides the current node is visited or not from the parent node. In such a way, we need to visit the parent node which was already visited and the duplicated bounding box intersection tests. The new k-D tree traverse algorithm reduces the brother and parent duplicated visit by using an efficient method which decides whether the brother node is already visited or not during the bottom-up search. Also the algorithm take place bounding box intersection tests only for the nodes which is not yet done. As a result our experiment shows the new algorithm is about 30% faster than the previous.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.39 no.4
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• pp.403-413
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• 1990

A collision free trajectory control for multiple mobile robots in obstacle-resident workspace is proposed. The proposed method is based on the concept of neural optimization network which has been applied to such problems which are too complex to be handled by traditional analytical methods, and gives good adaptibility for unpredictable environment. In this paper, the positions of the mobile robot are taken as the variables of the neural circuit and the differential equations are derived based on the performance index which is the weighted summation of the functions of the distances between the goal and current position of each robot, between each pair of robots and between the goal and current position of each robot, between each pair of robots and between obstacles and robots. Also is studied the problem of local minimum and of detour in large radius around obstacles, which is caused by inertia of mobile robots. To show the validity of the proposed method an example is illustrated by computer simulation, in which 6 mobile robots with mass and friction traverse in a workspace with 6 obstacles.

• Journal of the Korea Institute of Military Science and Technology
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• v.15 no.1
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• pp.1-8
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• 2012

Obstacle detection is much studied by using sensors such as laser, vision, radar and ultrasonic in path planning for UGV(Unmanned Ground Vehicle), but not much reported about its characterization. In this paper not only an obstacle classification method using 2-dimensional LMS(Laser Measurement System) but also a decision making method whether to avoid or traverse the obstacle is proposed. The basic idea of decision making is to classify the characteristics by 2D laser scanned data and intensity data. Roughness features are obtained by range data using a simple linear regression model. The standard deviations of roughness and intensity data are used as measures for decision making by comparing with those of reference data. The obstacle classification and decision making for the UGV can facilitate a short path to the target position and the survivability of the robot.

• 한국지구물리탐사학회:학술대회논문집
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• 2006.06a
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• pp.79-82
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• 2006

This paper presents to examine the ability of an electrical resistivity method to monitor the grouting effect at subsidence area. To monitor the changes in ground resistivity before and during the grout, series of electrical resistivity monitoring surveys have been conducted. Data has acquired in the form of grid making nine lines parallel to road and four lines traverse the road. Two kinds of electrode arrays modify pole-pole and dipole-dipole arrays were used during resistivity data acquisition. In this paper, the results show that electrical prospecting is an effective method to detect low resistivity imaging zone by grout during the ground reinforcement.

• Journal of the Korean Operations Research and Management Science Society
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• v.14 no.2
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• pp.53-66
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• 1989

The Public Vehicle Routing Problem (PVRP) is to find the minimum total cost routes of M or less Public-Vehicles to traverse the required arcs(streets) at least once, and return to their starting depot on a directed network. In this paper, first, a mathematical model is formulated as minimal cost flow model with illegal subtour elimination constraints, and with the fixed cost and routing cost as an objective function. Second, an efficient branch and bound algorithm is developed to obtain an exact solution. A subproblem in this method is a minimal cost flow problem relaxing illegal subtour elimination constraints. The branching strategy is a variable dichotomy method according to the entering nonrequired arcs which are candidates to eneter into an illegal subtour. To accelerate the fathoming process, a tighter lower bound of a candidate subproblem is calculated by using a minimum reduced coast of the entering nonrequired arcs. Computational results based on randomly generated networks report that the developed algorithm is efficient.

• Proceedings of the KSME Conference
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• 2008.11b
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• pp.2621-2624
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• 2008

The study on the measurement method of the aerodynamic performance of a turbo compressor was conducted. It is well known that the performance and the efficiency of the compressor can be calculated from the temperature and pressure distribution in each stage of the compressor. In the past Pitot tubes and thermocouples were used to measure pressure and temperature respectively, and recently pressure and temperature rake is used in order to decrease the measuring time and the number of measurement. The miniature total pressure rake which is available in the compressor with a small axial gap is designed and is under development.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.679-682
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• 2004

Air void systems in hardened concrete has an important influence on concrete durability such as freeze-thaw resistance, water permeability, surface scaling resistance. Linear traverse method and point count method described at ASTM is the routine analysis of the air void system that have been widely used to estimate the spacing factor in hardened concrete. Recently, many concretes often have a spacing factor higher than the generally accepted $200-250{\mu}m$ limit for the usual range of air contents. This study is proposed to estimate the matrix spacing factor by calculation of simplicity. The matrix spacing factor needs two parameters that are air content and numbers of air voids in the hardened concrete. Those are obtained from the standard air-void system analysis of the ASTM C 457. The equation is valid for all values of paste-to-air ratio because the estimation of paste content is unnecessary at the using ASTM C 457. The matrix spacing factor yields a similar estimate of the standard spacing factor.

• The Transactions of the Korea Information Processing Society
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• v.2 no.1
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• pp.119-129
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• 1995

In this paper, we propose a schedulatility analysis method for real-time programs. Several approaches to anlayzing schedulability have been developed, but since these approaches use a fixed priority scheduling method and/or traverse all possible state spaces, there take place exponential time and space complexity of these methods, Therefore it is necessary to reduce the state space and detect schedulability at earlier time. Our schedulability analysis method uses a minimum unit time taken to terminate synchronization action, a minimum unit time taken to terminate actions after synchronization, and a deadline of processes to detect unschedulability at earlier time and dynamic scheduling scheme to reduce state space. We conclude that our method can detected unschedulability earlier 50 percent unit time than Fredette's method.

• Journal of Institute of Control, Robotics and Systems
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• v.14 no.9
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• pp.909-915
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• 2008

Recently, the interests in the development and application of unmaned robots are increasing in various fields including surveillance and reconnaissance, planet exploration, and disaster relief. Unmaned robots are usually controlled from distance using radio communications but they should be equipped with an autonomous travelling function to cope with unexpected terrains and obstacles. This means that they should be able to evaluate terrain's characteristics quantitatively using mounted sensors so as to traverse harsh natural terrains autonomously. For this purpose, this paper presents a method for extracting terrain information, that is, slope and roughness from elevation maps as a prior step of traversability analysis. Slope is extracted using the curve fitting based on the least squares method and roughness using three metrics and their weighted average. The effectiveness of the proposed method is verified on both a fractal map and the world model map of a real terrain.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.32 no.10
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• pp.784-790
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• 2008

The feasibility and the accuracy of the correlation coefficient(CC) method for the determination of particle positions along the optical axis in digital particle holography were verified by alidation experiments. A traverse system with capable of high precision was used to move the particle objects by exact known distances between several different positions. The particle positions along the optical axis were calculated by the CC method and compared with their exact values to obtain the errors of the focal plane determination. The tested particles were 2D dots in a calibration target along with different sized glass beads and droplets that reflected and caused a three-dimensional effect. The results show that the CC method can work well for both the 2D dots and the 3D particles. The effect of other particles on the focal plane determination was also investigated. The CC method can locate the focal plane of particles with a high precision, regardless of the existence of other particles.