Entity

Time filter

Source Type

Yanggu, South Korea

Kim M.-H.,Republic of Korea Army Headquarters | Baik H.,GM Korea Company | Lee S.,Purdue University
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2014

This paper addresses a task allocation problem for a team of UAVs that cooperatively performs a search and attack mission in an unknown region. The UAVs are heterogeneous carrying different types and amounts of munition resources, and limited in communications and sensing capabilities. The environment is highly uncertain and dynamic where no prior information is available and dynamic events such as UAV failures unpredictably occur. The objective of the mission is to maximize total reward obtained by destroying targets within a given mission horizon. A group of UAVs may need to be formed to attack a target because individual UAVs may not have sufficient resources for the execution of attack tasks. Instantaneous task allocation approaches that seek for optimal solution for current tasks cannot effectively account for the unpredictability of future tasks in the uncertain dynamic environment. In this paper, we propose a distributed task allocation scheme based on resource welfare of which concept is adopted from economics. The approach we present enables the UAV team to effectively utilize resources by balancing resource depletions and consequently be capable of smoothly responding to dynamic events by retaining more UAVs available. Simulation experiments were conducted in various conditions to evaluate the performance of the proposed approach in comparison with the instantaneous task allocation method. The results show that our approach improves the performance by up to 29.3 % with respect to the instantaneous task allocation method. © 2014, Springer Science+Business Media Dordrecht. Source


Lee J.,GM Korea Company | Song S.,Yonsei University | Chun K.M.,Yonsei University
International Journal of Automotive Technology | Year: 2012

In lean-DeNOX catalysis reactions, hydrogen is a good reducing agent in PGM catalysts as well as an effective promoter in selective catalytic reduction reactions over base metal oxide catalysts. However, such a lean-DeNOX system, which uses hydrogen, requires an on-board fuel reforming system applicable to internal combustion engines. In this study, catalytic partial oxidation (CPOx) performance was tested in a laboratory for various reactants and hydrocarbon conditions. Volume concentrations of 5-10% oxygen and 0-5% water vapor were used to simulate diesel exhaust, and n-C12H26 was used as the feedstock for the reforming reaction. In the CPOx of n-C12H26, the highest hydrogen selectivity was 64% and was achieved at 100,000 h-1 GHSV. Additionally, the C/O ratio was less than unity in the absence of water vapor. However, as the water concentration was increased to 2. 5 and 5. 0 vol. % in the n-C12H26 CPOx reactions, the maximum hydrogen selectivity was increased from 64% in the absence of water to 70% and 75%, respectively. This effect is a consequence of the water-gas shift reaction over the catalyst bed. Regarding oxygen concentration effects, hydrogen selectivity slightly increased with increasing oxygen concentration from 10% to 15%. It was also found that the CPOx reaction of n-C12H26 can be ignited at temperatures below 300 C. Accordingly, it can be concluded that CPOx is a useful and feasible device for promoting diesel DeNOx catalysis in terms of hydrogen productivity and reaction initiation. © 2012 The Korean Society of Automotive Engineers and Springer-Verlag Berlin Heidelberg. Source


Jeon B.J.,Seoul National University of Science and Technology | Kim Y.S.,GM Korea Company | Choi H.G.,Seoul National University of Science and Technology
Journal of Mechanical Science and Technology | Year: 2012

Conjugate heat transfer around a circular cylinder with heat source was numerically investigated. Both the forced convection of water and conduction of carbon-steel were involved in the present simulation. A finite element formulation based on SIMPLE type algorithm was adopted for solving the incompressible Navier-Stokes equations coupled with energy equation. A conduction heat transfer problem inside the cylinder was trivially coupled with forced convection around the cylinder by using the Galerkin formulation of energy equation. The proposed algorithm was verified by solving the benchmark problem of conjugate heat transfer inside a cavity having a centered body. The effect of the Reynolds number on the temperature distribution on the cylinder surface and the maximum temperature inside the cyl-inder was examined. It was shown that the maximum temperature decreased as Reynolds number increased and that the position of the maximum temperature moved from the center to the rear part of the cylinder till Re = 20 and then moved back toward the center beyond Re = 20 since the reverse flow around the rear part of the cylinder became stronger as the Reynolds number further increased. Lastly, the maximum temperature of the cylinder with rotation was higher than that of the fixed one and the position of the maximum temperature inside the cylinder depended on the position and the strength of the dead zone. © KSME & Springer 2012. Source


Meinert F.,General Motors | Johannessen K.,GM Holden Ltd | Saito F.,GM do Brazil | Song B.,GM Korea Company | And 4 more authors.
SAE International Journal of Passenger Cars - Mechanical Systems | Year: 2016

Wind tunnel testing of reduced-scale models is a valuable tool for aerodynamic development during the early stages of a new vehicle program, when basic design themes are being evaluated. Both full-and reduced-scale testing have been conducted for many years at the General Motors Aerodynamics Laboratory (GMAL), but with increased emphasis on aerodynamic drag reduction, it was necessary to identify additional facilities to provide increased test capacity. With vehicle development distributed among engineering teams around the world, it was also necessary to identify facilities local to those teams, to support their work. This paper describes a cooperative effort to determine the correlation among five wind tunnels: GMAL, the Glenn L. Martin Wind Tunnel (GLMWT) at the University of Maryland, the Institute of Aeronautics and Space (IAE/ALA) TA-2 Wind Tunnel in Brazil, the Monash University Wind Tunnel in Australia, and the Korea Aerospace Research Institute Low Speed Wind Tunnel (KARI LSWT). Correlation tests were conducted using a vehicle model with interchangeable body modules and additional parts, to determine the relationships of measured aerodynamic force and moment coefficients among the tunnels. Despite the significant differences among facilities, the correlation results were satisfactory for reduced-scale wind tunnel development of future General Motors Co. (GM) vehicles. Correlation equations were defined, allowing conversion of data from one tunnel to equivalent values at another. This paper will present the physical descriptions and airflow characteristics of the wind tunnels, the test equipment and procedures, and the correlation results. Copyright © 2016 SAE International. Source


Ge J.C.,Chonbuk National University | Kim M.S.,Chonbuk National University | Yoon S.K.,GM Korea Company | Choi N.J.,Chonbuk National University
Energies | Year: 2015

Biodiesel as a clean energy source could reduce environmental pollution compared to fossil fuel, so it is becoming increasingly important. In this study, we investigated the effects of different pilot injection timings from before top dead center (BTDC) and exhaust gas recirculation (EGR) on combustion, engine performance, and exhaust emission characteristics in a common rail diesel engine fueled with canola oil biodiesel-diesel (BD) blend. The pilot injection timing and EGR rate were changed at an engine speed of 2000 rpm fueled with BD20 (20 vol % canola oil and 80 vol % diesel fuel blend). As the injection timing advanced, the combustion pressure, brake specific fuel consumption (BSFC), and peak combustion pressure (Pmax) changed slightly. Carbon monoxide (CO) and particulate matter (PM) emissions clearly decreased at BTDC 20° compared with BTDC 5°, but nitrogen oxide (NOx) emissions increased slightly. With an increasing EGR rate, the combustion pressure and indicated mean effective pressure (IMEP) decreased slightly at BTDC 20° compared to other injection timings. However, the Pmax showed a remarkable decrease. The BSFC and PM emissions increased slightly, but the NOx emission decreased considerably. Source

Discover hidden collaborations