• 한국해양공학회지
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• 제30권1호
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• pp.18-24
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• 2016

Stabilizer fins are installed on each side of a ship to control its roll motion. The most common stabilizer fin is a rolling control system that uses the lift force on the fin surface. If the angle of attack of a stabilizer fin is zero or the speed is zero, it cannot control the roll motion. The Coanda effect is well known to generate lift force in marine field. The performance of stabilizer fin that applies the Coanda effect has been verified by model tests and numerical simulations. It was found that a stabilizer fin that applied the Coanda effect at Cj = 0.085 and a zero angle of attack exactly coincided with that of the original fin at α = 26°. In addition, the power needed to generate the Coanda effect was not high compared to the motor power of the original stabilizer fin.

• Journal of Advanced Marine Engineering and Technology
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• 제10권4호
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• pp.50-56
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• 1986

This report deals with a study on the boundary layer characteristics of TP620 hydrofoil in the steady state by using two dimensional boundary layer theory. On the basis of complex velocity and laminar and turbulent boundary layer theory, the author attempts to know some tendency by evaluating the performance characteristic values of TP620 hydrofoil working in a uniform flow. In deriving characteristic values, he calculates numerically velocity, momentum thickness, skin friction coefficient, shape factor, and displacement thickness on the TP620 hydrofoil working at each attack angle in a uniform flow. Applying this present numerical calculation using Thwaites' and Head's method, the results of boundary layer on the hydrofoil are shown to be influenced by surface velocity and attack angle.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.371-374
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• 2006

초음속 유동장 내에서 돌출된 sharp fin형상에 의해 발생하는 충격파로 인한 열전달 특성변화 연구를 수행하였다. IR camera를 이용하여 마하 3의 유동 내에 attack angle이 $10^{\circ}$ 부터 $20^{\circ}$ 의 fin을 돌출시켜 생기는 충격파에 의한 바닥면 열전달 계수 변화를 측정하였으며, 유동장의 변화를 알아보기 보기 위해 oil flow method를 사용하였다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2011년 춘계학술대회논문집
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• pp.494-499
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• 2011

One of the devices to prevent separated flow over a wing or a flap at high angle of attack is a vortex generator. In the present work, we numerically study the flow around a low-profile or micro vortex generator whose height is less than local boundary layer thickness which can delay separation with a minimum drag penalty owing to its very small wetted surface area. As a first step toward a parametric study to efficiently design this MVG flow control system, we simulate the flow around a single MVG on a flat plate. For the simulation, we employ OpenFOAM with Launder-Sharma ${\kappa}$-epsilon model. The analysis results are validated by comparing with experimental results of a rectangular MVG at an angle of attack of 10 degrees whose height is 20% of local boundary layer. Important results and aspects of this numerical study are discussed. We also simulate the flow around rectangular, triangular and trapezoidal MVGs and the results are compared

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
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• pp.233-236
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• 2005

Sewage facilities are positively necessary for environment improvement such as rainwater removal, sewage disposal, preservation of the quality of water and health of the citizens in present-day. Meanwhile, a deterioration of the concrete sewer facilities is increasing rapidly due to the chemical and physical attack and especially biochemical attack that is to say biodeterioration. In this study, to prevent biochemical corrosion of the sewer concrete, surface of the concrete was spread with liquefied organic and inorganic complex antibiotics and then its engineering properties were experimentally investigated

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2017년도 추계 학술논문 발표대회
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• pp.61-62
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• 2017

In this study, the initiation of steel corrosion was monitored due to chloride attack using embedded sensor. In general, Steel bars embedded in concrete are protected from corrosion by being forming a passive film on the surface. However, the passive film is destroyed by chemical erosion such as concrete carbonation and chloride penetration, and the rebar is exposed to the deteriorating factor and corrosion proceeds. In order to realize the initiation of steel corrosion, OCP and change of Impedance parameter were observed by using Half-cell and EIS method depending on cover depth. As result, 10mm cover showed the impedence increased in 6weeks.

• 전자통신동향분석
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• 제34권2호
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• pp.73-82
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• 2019

Airport is shifted airport 1.0 to airport 4.0 called smart airport and services paradigm is changed into direction to point the customer targeted benefits. Smart airports make use of integrated Internet of Things components to provide added-value services. By integrating smart components, airports are being exposed to a larger attack surface and new attack vectors. Self-services such as web or mobile check-in, self check-in/tagging/back drop/boarding, etc. should be strengthened to make airport processes smarter, and technologies such as automatic immigration, smart security search, and automatic AI-based baggage search should be applied. In this paper, we describe the necessity and importance of smart airports and next generation security screening technology. Further, we describe a walk through-type smart security screening system.

• 한국안전학회지
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• 제22권3호
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• pp.57-64
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• 2007

Recently, the corrosion of concrete structures has received great attention related with the deterioration of sea-side structures, such as new airport, bridges, and nuclear power plants. In this regards, many studies have been done on the chloride attack in concrete structures. However, those studies were confined mostly to the single deterioration due to chloride only, although actual environment is rather of combined type. The purpose of the present study is, therefore, to explore the influences of carbonation and freezing-thawing action to chloride attack in concrete structures. The test results indicate that the chloride penetration is more pronounced than the case of single chloride attack when the carbonation process is combined with the chloride attack. It is supposed that the chloride ion concentration of carbonation region is higher than the sound region because of the separation of fixed salts. Though the use of fly ash pronounces the chloride ion concentration in surface, amounts of chloride ion penetration into deep region decreases with the use of fly ash. The small reduction of relative dynamic elastic modulus induced from freezing-thawing increases the chloride ion penetration depths much. The present study allows more realistic assessment of durability for such concrete structures which are subjected to combined attacks of both chlorides and carbonation or freezing-thawing but the future studies for combined environment will assure the precise assessment.

• Journal of Information Processing Systems
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• 제15권4호
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• pp.865-889
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• 2019

The need for cyber resilience is increasingly important in our technology-dependent society where computing devices and data have been, and will continue to be, the target of cyber-attackers, particularly advanced persistent threat (APT) and nation-state/sponsored actors. APT and nation-state/sponsored actors tend to be more sophisticated, having access to significantly more resources and time to facilitate their attacks, which in most cases are not financially driven (unlike typical cyber-criminals). For example, such threat actors often utilize a broad range of attack vectors, cyber and/or physical, and constantly evolve their attack tactics. Thus, having up-to-date and detailed information of APT's tactics, techniques, and procedures (TTPs) facilitates the design of effective defense strategies as the focus of this paper. Specifically, we posit the importance of taxonomies in categorizing cyber-attacks. Note, however, that existing information about APT attack campaigns is fragmented across practitioner, government (including intelligence/classified), and academic publications, and existing taxonomies generally have a narrow scope (e.g., to a limited number of APT campaigns). Therefore, in this paper, we leverage the Cyber Kill Chain (CKC) model to "decompose" any complex attack and identify the relevant characteristics of such attacks. We then comprehensively analyze more than 40 APT campaigns disclosed before 2018 to build our taxonomy. Such taxonomy can facilitate incident response and cyber threat hunting by aiding in understanding of the potential attacks to organizations as well as which attacks may surface. In addition, the taxonomy can allow national security and intelligence agencies and businesses to share their analysis of ongoing, sensitive APT campaigns without the need to disclose detailed information about the campaigns. It can also notify future security policies and mitigation strategy formulation.

• 정보보호학회논문지
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• 제31권3호
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• pp.373-385
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• 2021

운전자의 안전성 및 편의성을 향상시키기 위하여, 최근 자동차에는 다수의 전자제어장치가 탑재되고 있다. 전자제어장치들은 차량의 상태를 서로 공유하기 위하여 일반적으로 CAN 통신 프로토콜을 이용하여 통신한다. 현대의 자동차는 안전성 및 편의성과 관련된 최첨단 서비스를 제공하고 있지만, 사이버보안 위협에 대한 Attack Surface가 증가하는 문제점이 있다. 자동차 해킹의 경우에는 운전자 생명과 직접적 영향이 있기 때문에, 이에 대응하기 위한 자동차 보안 기술 개발은 매우 중요하다. 차량용 침입탐지 기술은 자동차 해킹에 대응하기 위해 연구되고 있는 가장 대표적인 자동차 보안 기술 중 하나지만, 현재 제품화 가능한 수준의 차량용 침입 탐지 기술은 모두 주기 메시지에 대한 침입 탐지 여부만 분석이 가능하고 주기 메시지와 이벤트 메시지가 혼합된 형태인 PE (Periodic-and-on-Event) 메시지에 대해서는 분석이 어렵다. 본 논문에서는 PE 메시지를 이용하여 자동차 내부 네트워크에 침입하는 공격자 유형을 분류하고 이를 탐지할 수 있는 기법을 제안한다. 그리고 실제 차량에서 제안하는 기법을 우리의 공격자 모델에서 평가한 결과 0%의 FPR과 FNR을 보여준다.