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Jung S.K.,Korea Aerospace Industries LTD. | Myong R.S.,Gyeongsang National University
Computers and Fluids | Year: 2013

A second-order positivity-preserving finite volume upwind scheme based on the approximate Riemann solver is developed for computing the Eulerian two-phase flow composed of air and small water droplets in atmospheric icing. In order to circumvent a numerical problem due to the non-strictly hyperbolic nature of the original Eulerian droplet equations, a simple technique based on splitting of the original system into the well-posed hyperbolic part and the source term is proposed. The positivity-preserving Harten-Lax-van Leer-Contact approximate Riemann solver is then applied to the well-posed hyperbolic part of the Eulerian droplet equations. It is demonstrated that the new scheme satisfies the positivity condition for the liquid water contents. The numerical results of one and two-dimensional test problems are also presented as the verification and validation of the new scheme. Lastly, the exact analytical Riemann solutions of the well-posed hyperbolic part of the droplet equations in wet and dry regions are given for the verification study. © 2013 Elsevier Ltd.

Lee E.,Korea Aerospace Industries LTD. | Jeong Y.,Korea Aerospace Industries LTD. | Kim S.,Gyeongsang National University
Korean Journal of Materials Research | Year: 2015

Aging aircraft structures are inevitably exposed to environment for a long time facing many potential problems, including corrosion and wide spread fatigue damage, which in turn cause the degradation of flight safety. In this study, the environmental surface damages on aging aircraft structures induced during service were quantitatively analyzed. Additionally, S-N fatigue tests were performed with center hole specimens extracted from aging aircraft structures. From the results of quantitative analyses of the surface damages and fatigue tests, it is concluded that corrosion pits initiated during service reduce the fatigue life significantly. Finally, using the fracture mechanics and the EIFS (equivalent initial flaw size) concepts, the remaining fatigue life was predicted based on actual fatigue test results. © Materials Research Society of Korea, All rights reserved.

Moon Y.H.,Gyeongsang National University | Yoon K.S.,Korea Aerospace Industries LTD. | Park S.-T.,Electronics and Telecommunications Research Institute | Shin I.H.,Electronics and Telecommunications Research Institute
IEEE Transactions on Multimedia | Year: 2013

In this paper, a new fast encoding algorithm based on an efficient motion estimation (ME) process is proposed to accelerate the encoding speed of the scalable video coding standard. Through analysis of the ME process performed in the enhancement layer, we discovered that there are redundant MEs and some MEs can simply be unified at the fully overlapped search range (FOSR). In order to make the unified ME more efficient, we theoretically derive a skip criterion to determine whether the computation of rate-distortion cost can be omitted. In the proposed algorithm, the unnecessary MEs are removed and a unified ME with the skip criterion is applied in the FOSR. Simulation results show that the proposed algorithm achieves computational savings of approximately 46% without coding performance degradation when compared with the original SVC encoder. © 2012 IEEE.

Hyun J.,Korea Aerospace Industries LTD. | Kim K.H.,Gyeongsang National University
Proceedings - 18th IEEE International Conference on Embedded and Real-Time Computing Systems and Applications, RTCSA 2012 - 2nd Workshop on Cyber-Physical Systems, Networks, and Applications, CPSNA | Year: 2012

As real-time systems become complex and require high-performance, Hierarchical Real-Time Scheduling Framework (HRTSF) has been investigated to schedule real-time tasks to meet their deadlines by sharing resources hierarchically under various scheduling algorithms. In this paper, we focus on fault-tolerant scheduling in the hierarchical real-time scheduling framework. Thus, we introduce a new component interface model which provides abstract information about a component's fault-tolerant real-time requirement. The upper-layer component can use the interface model to share its resource with consideration of both real-time and fault-tolerance. We also provide the schedulability analysis of Rate Monotonic (RM) algorithm under the proposed framework and apply it to a case study of designing avionics software as an example of Cyber Physical Systems (CPS). © 2012 IEEE.

Kim Y.,Korea Institute of Geoscience and Mineral Resources | Kwon J.,Korea Institute of Geoscience and Mineral Resources | Jeong Y.,Korea Aerospace Industries LTD. | Woo N.,Korea Institute of Geoscience and Mineral Resources | Kim S.,Gyeongsang National University
Metals and Materials International | Year: 2013

The through-thickness stress corrosion cracking (SCC) behaviors of thick 2024-T351 and 7050-T7451 extrudates in 3.5% NaCl solution were studied at both anodic and cathodic applied potentials using a slow strain rate test method. The SCC susceptibilities of 2024-T351 extrudate tended to change in the throughthickness direction, with the lowest susceptibility for the surface specimen. 7050-T7451 specimens, on the other hand, did not show a notable change in the through-thickness SCC susceptibility. The fractographic analysis suggested that the grain boundary played an important role in determining the SCC susceptibility. The SCC process of each alloy was discussed based on the microscopic and fractographic examinations. © 2013 The Korean Institute of Metals and Materials and Springer Science+Business Media Dordrecht.

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