Korea Air Force Academy

Cheongju, South Korea

Korea Air Force Academy

Cheongju, South Korea
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Lee S.S.,Dong - A University | Kang S.,Korea Air Force Academy
Journal of Physical Therapy Science | Year: 2015

[Purpose] The aim of the study was to clarify the effects of regular exercise on lipid profiles and serum adipokines in Korean children. [Subjects and Methods] Subjects were divided into controls (n=10), children who were obese (n=10), and children with type 2 diabetes mellitus (n=10). Maximal oxygen uptake (VO2max), body composition, lipid profiles, glucagon, insulin and adipokines (leptin, resistin, visfatin and retinol binding protein 4) were measured before to and after a 12-week exercise program. [Results] Body weight, body mass index, and percentage body fat were significantly higher in the obese and diabetes groups compared with the control group. Total cholesterol, triglycerides, low-density lipoprotein cholesterol and glycemic control levels were significantly decreased after the exercise program in the obese and diabetes groups, while high-density lipoprotein cholesterol levels were significantly increased. Adipokines were higher in the obese and diabetes groups compared with the control group prior to the exercise program, and were significantly lower following completion. [Conclusion] These results suggest that regular exercise has positive effects on obesity and type 2 diabetes mellitus in Korean children by improving glycemic control and reducing body weight, thereby lowering cardiovascular risk factors and adipokine levels. ©2015 The Society of Physical Therapy Science.


Kim Y.-W.,Sogang University | Choi J.,Korea Air Force Academy | Park Y.-J.,Sogang University
Physical Review D - Particles, Fields, Gravitation and Cosmology | Year: 2014

We obtain a (5+1)-dimensional global flat embedding of the Gibbons-Maeda-Garfinkle-Horowitz-Strominger spacetime in the Einstein frame and a (5+2)-dimensional global flat embedding in the string frame. We show that the local free-fall temperatures for freely falling observers in each frame are finite at the event horizons, while the local temperatures for fiducial observers are divergent. We also observe that the local free-fall temperatures differ between the two frames. © 2014 American Physical Society.


Moon S.,Korea Air Force Academy | Oh E.,Korea Aerospace Research Institute | Shim D.H.,KAIST
Journal of Intelligent and Robotic Systems: Theory and Applications | Year: 2013

In this paper, a hierarchical framework for task assignment and path planning of multiple unmanned aerial vehicles (UAVs) in a dynamic environment is presented. For multi-agent scenarios in dynamic environments, a candidate algorithm should be able to replan for a new path to perform the updated tasks without any collision with obstacles or other agents during the mission. In this paper, we propose an intersection-based algorithm for path generation and a negotiation-based algorithm for task assignment since these algorithms are able to generate admissible paths at a smaller computing cost. The path planning algorithm is also augmented with a potential field-based trajectory replanner, which solves for a detouring trajectory around other agents or pop-up obstacles. For validation, test scenarios for multiple UAVs to perform cooperative missions in dynamic environments are considered. The proposed algorithms are implemented on a fixed-wing UAVs testbed in outdoor environment and showed satisfactory performance to accomplish the mission in the presence of static and pop-up obstacles and other agents. © 2012 Springer Science+Business Media B.V.


Lee C.,Seoul National University | Lee H.,Dong - A University | Seol H.,Korea Air Force Academy | Park Y.,Seoul National University
Expert Systems with Applications | Year: 2012

One of the most crucial stages in the new service development (NSD) process is concept selection, which is characterized by newly generated alternatives and vaguely defined concept evaluation criteria. Although a number of factors have been found to be influential, a lacuna remains as to how to make a strategic decision based on influential factors. This study proposes a systematic approach to evaluation of new service concepts (NSCs) by integrating the merit of group analytic hierarchy process (AHP) in modeling multi-criteria decision making (MCDM) problems and the strength of rough set theory (RST) in handling subjectivity in concept evaluation. The suggested approach is designed to be executed in four discrete stages. First of all, a hierarchical AHP model for the evaluation of NSCs is constructed in terms of strategy, finance, market, technology, and implementation. Second, pairwise comparisons are made among criteria and sub-criteria, and preferences to NSCs with respect to the sub-criteria are obtained by domain experts. Third, the individual judgments obtained at the preceding stage are aggregated into group judgments. Finally, the NSCs are prioritized based on risk propensity of decision makers. A case study of the video game service is presented to illustrate the suggested approach. We believe that our method can promote consensus building on the promising NSCs. © 2011 Elsevier Ltd. All rights reserved.


Seol H.,Korea Air Force Academy | Lee S.,Ajou University | Kim C.,Induk University
Expert Systems with Applications | Year: 2011

From a resource-based point of view, firm's technological capabilities can be used as underlying sources for identifying new businesses. However, current methods are insufficient to systematically and clearly support firms in finding new business areas based on their technological strength. This research proposes a systematic approach to identify new business areas grounded on the relative technological strength of firms. Patent information is useful as a measure of firms' technological resources and data envelopment analysis (DEA) is beneficial to obtain the weighted value of patents according to their quality. With this weighted quality of patents, a firm can evaluate their relative technological strength at the industry and product level according to potential business areas. To compute technological strength by products, this research applies text mining method to patent documents, a method which a researcher discovers knowledge with unstructured data with. This paper shows the usefulness of the newly proposed framework with a case study. © 2010 Published by Elsevier Ltd.


Choi J.,Korea Air Force Academy
Modern Physics Letters A | Year: 2014

In the framework of Lorentzian multiply warped products we study the magnetically charged Gibbons-Maeda-Garfinkle-Horowitz-Strominger (GMGHS) interior spacetime in the string frame. We also investigate geodesic motion in various hypersurfaces, and compare their solutions of geodesic equations with the ones obtained in the Einstein frame. © World Scientific Publishing Company.


Yang K.,Korea Air Force Academy
2013 International Conference on Unmanned Aircraft Systems, ICUAS 2013 - Conference Proceedings | Year: 2013

Planning in a cluttered environment under differential constraints is a difficult problem because the planner must satisfy the external constraints that arise from obstacles in the environment and the internal constraints due to the kinematic/dynamic limitations of the robot. This paper proposes a novel Spline-based Rapidly-exploring Random Tree (SRRT) algorithm which treats both the external and internal constraints simultaneously and efficiently. The proposed algorithm removes the need to discretize the action space as is common with conventional RRT, thus improving path quality. In addition, computationally expensive numerical integration of the system dynamics is replaced by an efficient spline curve parameterization. Finally, the SRRT guarantees continuity of curvature along the path satisfying any upper-bounded curvature constraints. This paper presents the underlying theory to the SRRT algorithm and presents simulation results of a mobile robot efficiently navigating through cluttered environments. © 2013 IEEE.


Yang K.,Korea Air Force Academy | Keat Gan S.,Korea Air Force Academy | Sukkarieh S.,Korea Air Force Academy
Advanced Robotics | Year: 2013

A new framework which adopts a rapidly-exploring random tree (RRT) path planner with a Gaussian process (GP) occupancy map is developed for the navigation and exploration of an unknown but cluttered environment. The GP map outputs the probability of occupancy given any selected query point in the continuous space and thus makes it possible to explore the full space when used in conjunction with a continuous path planner. Furthermore, the GP map-generated path is embedded with the probability of collision along the path which lends itself to obstacle avoidance. Finally, the GP map-building algorithm is extended to include an exploration mission considering the differential constraints of a rotary unmanned aerial vehicle and the limitation arising from the environment. Using mutual information as an information-theoretic measure, an informative path which reduces the uncertainty of the environment is generated. Simulation results show that GP map combined with RRT planner can achieve the 3D navigation and exploration task successfully in unknown and complex environments. © 2013 Copyright Taylor & Francis and The Robotics Society of Japan.


Yang K.,Korea Air Force Academy | Jung D.,Korea Air Force Academy | Sukkarieh S.,Korea Air Force Academy
Advanced Robotics | Year: 2013

This paper presents a path-smoothing algorithm over the piecewise linear path for non-holonomic robots. Based on the upper-bounded continuous curvature path-smoothing algorithm, three algorithms are proposed to enhance the path smoothing performance. First, an interactive algorithm, which fully utilizes extra distance margins of linear path, is suggested. Second, a bisection algorithm is proposed to relieve the violation of the maximum curvature constraints. Finally, an interpolating path-smoothing algorithm which passes intermediate points is suggested. Simulation results show the validity of the suggested algorithms. © 2013 Copyright Taylor & Francis and The Robotics Society of Japan.


Yang K.,Korea Air Force Academy
International Journal of Control, Automation and Systems | Year: 2011

A new synchronized biased-greedy RRT is proposed which leverages the strengths of the biased and greedy RRTs. It combines the advantage of the biased RRT that grows trees towards the goal location, with the ability of the greedy RRT that makes trees traverse the environment in a single iteration. The proposed method achieves performance improvements compared to other RRT variants, not only in computational time but also in the quality of the path. Two enhancements are made to the initial path to relax the sub-optimality of the RRT path; first a path pruning algorithm is executed to eliminate redundant nodes and an anytime strategy is adapted to continuously enhance the quality of the path within the deliberation time. © 2011 ICROS, KIEE and Springer.

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