• 한국전산유체공학회:학술대회논문집
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• 2011.05a
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• pp.414-419
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• 2011

Missile am fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 60 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure distribution, etc. are analyzed according to the angle of attack. The results at a low angle of attack are compared with other results before a stall condition. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. Unsteady velocity field, periodic vortex shedding, the unsteady pressure distribution on the airfoil surface, and the acoustic fields are analyzed. The effects of these unsteady characteristics in the aerodynamic coefficients are analyzed.

• Journal of computational fluids engineering
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• v.18 no.1
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• pp.1-6
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• 2013

Missile and fighter aircraft have been challenged by low restoring nose-down pitching moment at high angle of attach. The consequence of weak nose-down pitching moment can be resulting in a deep stall condition. Especially, the pressure oscillation has a huge effect on noise generation, structure damage, aerodynamic performance and safety, because the flow has strong unsteadiness at high angle of attack. In this paper, the unsteady aerodynamics coefficients were analyzed at high angle of attack up to 50 degrees around two dimensional NACA0012 airfoil. The two dimensional unsteady compressible Navier-Stokes equation with a LES turbulent model was calculated by OHOC (Optimized High-Order Compact) scheme. The flow conditions are Mach number of 0.3 and Reynolds number of $10^5$. The lift, drag, pressure, entropy distribution, etc. are analyzed according to the angle of attack. The results of average lift coefficients are compared with other results according to the angle of attack. From a certain high angle of attack, the strong vortex formed by the leading edge are flowing downstream as like Karman vortex around a circular cylinder. The primary and secondary oscillating frequencies are analyzed by the effects of these unsteady aerodynamic characteristics.

• Journal of The Korean Astronomical Society
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• v.38 no.2
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• pp.169-172
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• 2005

We present CO(3-2), CO(2-1), and 230 GHz (1.3 mm) continuum images of nearby galaxies taken with the Submillimeter Array (SMA). Our main topic is to study the relation between higher-J molecular gas (e.g., CO J=3-2, 2-1) and nuclear activities (e.g., active galactic nuclei [AGNs] and starbursts). The nearby Seyfert 2 galaxy M51 shows strong CO(3-2) emission from the circumnuclear molecular gas, with an intensity twice as strong as that of the CO(1-0) emission. Strong CO(3-2) emission enhancement suggests that the circum nuclear molecular gas in M51 is warm and dense, which may be related to the AGN activities. Molecular gas in the nearby moderate starburst galaxy NGC 6946 is distributed along the large-scale bar or spiral arms and along the minibar, and the multi-J CO line images show very similar distribution to each other. For this galaxy, there is no clear enhancement in higher-J lines as seen in M51, which may be because NGC 6946 does not have clear AGN activities. Based on the results of these two galaxies, the physical conditions of the circum nuclear molecular gas may be related to the AGN activities. We also observed the nearby edge-on starburst galaxy NGC 3628 and the starburst/Seyfert composite galaxy NGC 4945 with the CO(2-1) line and 230 GHz (1.3 mm) continuum emission. These information will give us some hints for understanding the relation between nuclear activities and circum nuclear molecular gas and dust.

• Journal of Environmental Science International
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• v.26 no.3
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• pp.289-302
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• 2017

During the research period, error analysis of the amount of daily precipitation was performed with data obtained from 2DVD, Parsivel, and AWS, and from the results, 79 days were selected as research days. According to the results of a synoptic meteorological analysis, these days were classified into 'LP type, CF type, HE type, and TY type'. The dates showing the maximum daily precipitation amount and precipitation intensity were 'HE type and CF type', which were found to be attributed to atmospheric instability causing strong ascending flow, and leading to strong precipitation events. Of the 79 days, most days were found to be of the LP type. On July 27, 2011 the daily precipitation amount in the Korean Peninsula reached over 80 mm (HE type). The leading edge of the Northern Pacific high pressure was located over the Korean Peninsula with unstable atmospheric conditions and inflow of air with high temperature and high humidity caused ascending flow, 120 mm/h with an average precipitation intensity of over 9.57 mm/h. Considering these characteristics, precipitation in these sample dates could be classified into the convective rain type. The results of a precipitation scale distribution analysis showed that most precipitation were between 0.4-5.0 mm, and 'Rain' size precipitation was observed in most areas. On July 9, 2011, the daily precipitation amount was recorded to be over 80 mm (CF type) at the rainy season front (Jangma front) spreading across the middle Korean Peninsular. Inflow of air with high temperature and high humidity created unstable atmospheric conditions under which strong ascending air currents formed and led to convective rain type precipitation.

• Convergence Security Journal
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• v.22 no.1
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• pp.149-158
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• 2022

R.o.K Marine Corps was established on April 15, 1949 at Deoksan Air Base in Jinhae. When they fought in the Korean War and the Vietnam War, they were sure to win, so they were loved and trusted by the people. Strong combat power is only possible when an advanced barracks culture is established. Today's new generation of soldiers have strong characteristics ; self-centered and individualistic. R.o.K Marine Corps officers must understand the characteristics of the new generation of soldiers and strive to develop creative leadership in order to make them utilize their characteristics. In addition, as cutting-edge science and technology develops along with the 4th industrial revolution, R.o.K Marine Corps officers should work hard to acquire professional tactical knowledge and self-development. Therefore, Marine Corps officers should do their best to understand the characteristics of the new generation of soldiers and demonstrate leadership to become a strong force trusted by the people.

• Journal of Broadcast Engineering
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• v.14 no.3
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• pp.322-331
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• 2009

This paper proposes an efficient data representation of stereo images using edge-based mesh optimization. Mash-based two dimensional warping for stereo images mainly depends on the performance of a node selection and a disparity estimation of selected nodes. Therefore, the proposed method first of all constructs the feature map which consists of both strong edges and boundary lines of objects for node selection and then generates a grid-based mesh structure using initial nodes. The displacement of each nodal position is iteratively estimated by minimizing the predicted errors between target image and predicted image after two dimensional warping for local area. Generally, iterative two dimensional warping for optimized nodal position required a high time complexity. To overcome this problem, we assume that input stereo images are only horizontal disparity and that optimal nodal position is located on the edge include object boundary lines. Therefore, proposed iterative warping method performs searching process to find optimal nodal position only on edge lines along the horizontal lines. In the experiments, we compare our proposed method with the other mesh-based methods with respect to the quality by using Peak Signal to Noise Ratio (PSNR) according to the number of nodes. Furthermore, computational complexity for an optimal mesh generation is also estimated. Therefore, we have the results that our proposed method provides an efficient stereo image representation not only fast optimal mesh generation but also decreasing of quality deterioration in spite of a small number of nodes through our experiments.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.29 no.4C
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• pp.461-471
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• 2004

Recently, subscribers have strong desire to get QoS based personalized services in high-speed Internet access. Service providers have been rapidly replacing ADSL, cable broadband access networks with Metro-Ethernet based VDSL. But, it is difficult for Motto-Ethernet based broadband access networks to provide QoS based personalized services, because already deployed network elements cannot distinguish subscribers by specific traffic characteristics. In this paper, when the access network has tree topology, we show that it is possible to provide QoS for each downstream flow with only per flow traffic shaping at the edge node without QoS functions in access networks. In order to show that our suggested scheduling algorithm at the edge node can support the assured service in tree topology access networks, we evaluated its performance by simulation. The suggested scheduling algorithm can shape per-flow traffic based on the maximum bandwidth, and guarantees minimum bandwidth per flow by modifying the DRR scheduler. Simulation results show that congestion and loss in the access network elements are greatly reduced, TCP performance is highly enhanced and loss for assured CBR service flows is reduced by only shaping per-flow traffic at the edge node using our proposed scheduling algorithm.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.238-238
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• 2009

In this work, we investigated the effect of the Zn complex concentration and growth temperature on the growth of ZnO nanorod by hydrothermal method. The ZnO nanorods were performed at condition of the various Zn complex concentration and growth temperature, 0.02 ~ 0.08 M and 60 ~ 80 $^{\circ}C$, respectably. We found from the SEM results that the diameter and length of ZnO nanorods were with increasing the growth temperature and Zn complex concentration. However, the growth condition in the two parameters wasmore than sensitive compared to Zn complex concentration on increasing the growth rate. From photoluminescence(PL) analysis, the strong band-edge emission for ZnO nanorod grown at 80 $^{\circ}C$ with 0.08 M indicated the fine crystallinity. Therefore, the diameter and length of ZnO nanorods have been able to control through the control of front growth parameters. Also, these ZnO nanorods grown low temperature will be available as building block for transparence flexible device applications.

• Proceedings of the Materials Research Society of Korea Conference
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• 2009.11a
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• pp.25.2-25.2
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• 2009

Vertically aligned zinc oxide(ZnO) nanorods (NRs) with different surface morphology were grown by metal organic chemical vapor deposition (MOCVD) on sapphire substrate with different deposition condition. Based on the surface morphology, ZnO nanostructures are divided into three types: nanoneedles, nanonails and nanorods with rounded tip. Variable temperature photoluminescence (PL) have employed to probe the exciton recombination in high density and vertically aligned ZnO Nanorod arrays. Low temperature photoluminescence measurements do not show any significant yellow emission, but the near band edge excitonic emission shows very strong dependence with the surface morphology. The recombination properties are expected to be different due to different surface-to-volume ratio and distribution of potential fluctuations of intrinsic defects.

• Proceedings of the IEEK Conference
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• 2001.09a
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• pp.385-388
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• 2001

본 논문에서는 비디오 영상에서 장면 전환을 검출하는 알고리듬을 제안한다. 장면 전환 검출은 비디오 프레임 사이의 유사도를 측정하여 이루어 진다. 유사도는 비디오 영상의 특성을 나타내는 지표를 추출하고 이를 비교함으로써 얻어진다. 비디오 영상의 특성 지표는 비디오 영상 전체에서 추출하는 것이 일반적이나 제안하는 알고리듬에서는 비디오 영상에서 강한 에지 부분을 포함하는 여러개의 블록에서만 추출된다. 이렇게 함으로써 배경보다 더 중요한 정보를 가진 에지 주변의 칼라 변화에 집중하는 효과를 얻게된다. 실험 결과는 강한 에지 블록에서 얻은 지표가 점진적 장면 전환(dissolve, wipe) 검출에 효과적임을 보여준다. 제안하는 알고리듬은 또한 Cut탐지에도 비교적 좋은 성능을 보인다. 그리고 Fade-in/out을 간단하면서 효과적으로 탐지할 수 있는 방법을 제시한다.