• EDISON SW 활용 경진대회 논문집
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• 제6회(2016년)
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• pp.19-22
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• 2016

Leading edge thrust is generally caused by passing air flow from lower to upper surface and it is required to have sufficient angle of attack for notable leading edge thrust. To produce leading edge thrust at low angle of attack, utilizing expansion wave accompanying low pressure is able to be a solution. Fore structure changes the direction of flow, and this flow passes the projected edge. As a result, from a perspective of the edge, it is able to have high angle of attack, and artificial expansion wave is generated. This concept shows 9.48% increase of L/D in inviscid flow, at Mach number 1.3 and angle of attack $1^{\circ}$ in maximum, and this model shows the 3.98% of increasement at angle of attack $2^{\circ}$. Although advantage of the artificial expansion wave decreased as angle of attack increase, it shows the possibility of aerodynamical improvement with artificial expansion wave.

• 한국정보통신학회논문지
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• 제26권9호
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• pp.1374-1381
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• 2022

네트워크 공격 대응에 관한 보안기술의 기존 연구들은 하드웨어적 네트워크 보안 기술을 이용하여 네트워크의 보안성을 높이는 방법이나 바이러스 방역 백신과 바이러스 방역 시스템이 주로 제안 설계되어왔다. 많은 사용자는 라우터의 보안 기능을 충분히 활용하지 못하고 있어 이러한 문제점을 극복하기 위해 네트워크 보안 수준에 따라 분리함으로써 계층화된 보안 관리를 통하여 외부에서의 공격을 차단할 수 있음을 계층별 실험을 통해 분류하였다. 연구의 범위는 Edge 라우터의 보안기술 동향을 살펴봄으로 Edge 라우터 기반의 네트워크 공격에 관한 위협으로부터 보호하는 방법과 구현 사례를 제시한다.

• Journal of Mechanical Science and Technology
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• 제18권12호
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• pp.2273-2283
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• 2004

The vortical flows over sharp-edged delta wings with and without a leading edge extension have been investigated using a computational method. Three-dimensional compressible Reynolds-averaged Navier-Stokes equations are solved to provide an understanding of the effects of the angle of attack and the angle of yaw on the development and interaction of vortices and the aerodynamic characteristics of the delta wing at a freestream velocity of 20 m/s. The present computations provide qualitatively reasonable predictions of vortical flow characteristics, compared with past wind tunnel measurements. In the presence of a leading edge extension, a significant change in the suction pressure peak in the chordwise direction is much reduced at a given angle of attack. The leading edge extension can also stabilize the wing vortex on the windward side at angles of yaw, which dominates the vortical flows over yawed delta wings.

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.914-924
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• 2003

The interaction and breakdown of vortices over the Leading Edge Extension (LEX) - Delta wing configuration has been investigated through wing-surface pressure measurements, the off-surface flow visualization, and 5-hole probe measurements of the wing wake section. The description focused on analyzing the interaction and the breakdown of vortices depending on the angle of attack and the sideslip angle. The Effect of angle of attack and sideslip angle on the aerodynamic load characteristics of the model is also presented. The sideslip angle was found to be a very influential parameter of the vortex flow over the LEX-delta wing configuration. The introduction of LEX vortex stabilized the vortex flow, and delayed the vortex breakdown up to a higher angle of attack. The vortex interaction and breakdown was promoted on the windward side, whereas it was suppressed on the leeward side.

• Journal of Mechanical Science and Technology
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• 제18권6호
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• pp.1042-1051
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• 2004

The vortex flow characteristics of a sharp-edged delta wing at high angles of attack were studied using a computational technique. Three dimensional, compressible Reynolds-averaged Navier-Stokes equations were solved to understand the effects of the angle of yaw, angle of attack, and free stream velocity on the development and interaction of vortices and the relationship between suction pressure distributions and vortex flow characteristics. The present computations gave qualitatively reasonable predictions of vortical flows over a delta wing, compared with past wind tunnel measurements. With an increase in the angle of yaw, the symmetry of the pair of leading edge vortices was broken and the vortex strength was decreased on both windward and leeward sides. An increase in the free stream velocity resulted in stronger leading edge vortices with an outboard movement.

• 한국정보처리학회:학술대회논문집
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• 한국정보처리학회 2013년도 춘계학술발표대회
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• pp.534-537
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• 2013

인터넷상에서 다양한 사용자 및 구성요소로 이루어진 분산시스템은 Sybil Attack 에 취약하다. 최근 온라인 소셜 네트워크(Online Social Network)의 그래프 정보를 사용해, Sybil Attack 에 대응하기 위한 Sybil-resistant value 추출 기법들이 제안되었다. 이 논문에서는 이러한 OSN 기반의 Sybil-resistant value 추출 기법들에 대한 성능을 평가한다. 특히 OSN 그래프의 각 노드들의 이웃 노드 개수 정보에 따른 성능과 Sybil 노드들의 Attack Edge 에 따른 성능을 평가한다. Facebook 에서 추출한 샘플 OSN 그래프를 사용한 성능 평가 분석을 통해, 실제 사용자를 위한 Sybil-resistant value 를 정상적으로 추출하기 위해서는 OSN 그래프 상에서 이웃 노드의 개수가 10 개 이상이어야 한다는 점과, Random Route Tail Intersection 기법이 Sybil 사용자 그룹의 Attack Edge 의 영향을 가장 적게 받는 다는점을 확인 하였다.

• 대한조선학회논문집
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• 제48권3호
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• pp.233-237
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• 2011

In the present experiments, vortical structures behind the hydrofoil trailing edge are visualized and analyzed as an elementary study for propeller singing phenomena. Two sorts of hydrofoil are selected for the measurement of shedding vortices. One was KH45 hydrofoil section and the other is KH45 with the truncated trailing edge that is positioned at X/C = 0.9523(C=chord length). Assuming the Strouhal number of 0.23, the shedding frequencies of vortices are extracted by analyzing the boundary layer thickness and the flow speed. The frequency distribution of shedding vortices is obtained with the variation of angle-of-attack while the flow speed is fixed to 8m/s. The truncation of the trailing edge makes the frequency of shedding vortices about 120Hz lower than that of original trailing edge and makes the vorticity value higher than the original trailing edge.

• 대한조선학회논문집
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• 제48권2호
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• pp.128-133
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• 2011

In the present study, the flow fields in between the propeller and the semi-spade rudder are investigated by using PIV technique to find out the influences of both simulated hull wake and propeller wake on the incident flow to the rudder. The velocity fields are measured at the propeller rotation angle of $180^{\circ}$ and the rudder deflection angles of $0^{\circ}$. Flow fields measured at each rudder deflection angle are analyzed in terms of angle-of-attack against the rudder leading edge. The hull wake increases the angle-of-attack more than that in the uniform inflow condition, forming the angle-of-attack of about $20^{\circ}$ at 0.7R(R=propeller radius) position. The distribution of the angle-of-attack is strongly affected by the stagnation point around the leading edge and camber effect of the rudder. These effects provide asymmetric distribution of angle-of-attack with respect to the leading edge of the rudder.

• 정보보호학회논문지
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• 제33권3호
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• pp.549-559
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• 2023

5G 네트워크의 핵심 기술로 모바일 에지 컴퓨팅(Mobile Edge Computing, MEC)이 주목받음에 따라, 모바일 사용자의 데이터를 기반으로 한 5G 네트워크 기반 에지 AI 기술이 최근 다양한 분야에서 이용되고 있다. 하지만, 전통적인 인공지능 보안에서와 마찬가지로, 에지 AI 핵심 기능을 담당하는 코어망 내 표준 5G 네트워크 기능들에 대한 적대적 교란이 발생할 가능성이 존재한다. 더불어, 3GPP에서 정의한 5G 표준 내 Standalone 모드의MEC 환경에서 발생할 수 있는 데이터 오염 공격은 기존 LTE망 대비 현재 연구가 미비한 실정이다. 본연구에서는 5G에서 에지 AI의 핵심 기능을 담당하는 네트워크 기능인 NWDAF를 활용하는 MEC 환경에 대한 위협 모델을 탐구하고, 일부 개념 증명으로써 Leaf NWDAF에 대한 데이터 오염 공격 탐지 성능을 향상시키기 위한 특징 선택 방법을 제안한다. 제안한 방법론을 통해, NWDAF에서의 Slowloris 공격 기반 데이터 오염 공격에 대해 최대 94.9%의 탐지율을 달성하였다.

• 한국가시화정보학회지
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• 제19권3호
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• pp.106-114
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• 2021

In the present study, we investigate the flow characteristics of a paraglider canopy with leading-edge tubercles by performing force measurement and surface flow visualizations. The experiment is conducted at Re = 3.3×10⁵ in a wind tunnel, where Re is the Reynolds number based on the mean chord length and the free-stream velocity. The canopy model with leading-edge tubercles has flow characteristics of a two-step stall, showing an earlier onset of the first stall than the canopy model without leading-edge tubercles. However, the main stall angle of the tubercled model is much larger than that of the canopy model without tubercles, resulting in a higher aerodynamic performance at high angles of attack. The delay in the main stall is ascribed to the suppression of separation bubble collapse around the wingtip at high angles of attack.