• Title/Summary/Keyword: Attack Model

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An Integrated System to Predict Early-Age Properties and Durability Performance of Concrete Structures

  • Wang, Xiao-Yong;Lee, Han-Seung
    • Proceedings of the Korea Concrete Institute Conference
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    • 2010.05a
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    • pp.465-466
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    • 2010
  • In this paper, an integrated system is proposed which can evaluate both the early-age properties and durability performance of concrete structures. This integrated system starts with a hydration model which considers both Portland cement hydration and chemical reactions of supplementary cementing materials (SCM). Based on the degree of hydration of cement and mineral admixtures, the amount of reaction products, the early age heat evolution, chemically bound water, porosity, the early age short-term mechanical behaviors, shrinkage and early-age creep are evaluated as a function of curing age and curing conditions. Furthermore, the durability aspect, such as carbonation of blended concrete and chloride attack, are evaluated considering both the material properties and surrounding environments. The prediction results are verified through experimental results.

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Detection of Abnormal Signals in Gas Pipes Using Neural Networks

  • Min, Hwang-Ki;Park, Cheol-Hoon
    • Proceedings of the IEEK Conference
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    • 2008.06a
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    • pp.669-670
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    • 2008
  • In this paper, we present a real-time system to detect abnormal events on gas pipes, based on the signals which are observed through the audio sensors attached on them. First, features are extracted from these signals so that they are robust to noise and invariant to the distance between a sensor and a spot at which an abnormal event like an attack on the gas pipes occurs. Then, a classifier is constructed to detect abnormal events using neural networks. It is a combination of two neural network models, a Gaussian mixture model and a multi-layer perceptron, for the reduction of miss and false alarms. The former works for miss alarm prevention and the latter for false alarm prevention. The experimental result with real data from the actual gas system shows that the proposed system is effective in detecting the dangerous events in real-time with an accuracy of 92.9%.

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Studies on Flowfields Around Axisymmetric Bodies in the Rarefied Gas Regime Using the Direct Simulation Monte Carlo Method (희박기체영역에서의 직접모사법에 의한 축대칭 형상 주위의 유동장 해석에 관한 연구)

  • Lee Dong-Dae;Park Hyeong-Gu
    • 한국전산유체공학회:학술대회논문집
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    • 1998.11a
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    • pp.71-77
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    • 1998
  • In this study we calculated the flowfields around the axisymmetric bodies in the rarefied gas regime by using the DSMC. A flat-ended cylinder was selected as a representative axisymmetric body and the gas used for all calculations was nitrogen. With zero angle of attack, an increasingly rapid rise in density and the effect of shock waves near the flat-ended face were examined. And on the cylinder surface velocity slips and boundary layers could be observed in the results. Larsen-Borgnakke model was used for the energy redistribution in inelastic collisions. And by considering all internal energy modes, the distributions of translational, rotational and vibrational temperatures were plotted. The calculations were peformed for various Knudsen numbers, Especially the rotational temperatures calculated for a case were compared with the experimental results. And the simulation results show good agreements with the experimental ones.

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FLOW SIMULATION AROUND DUCTED-PROP (덕티드-프롭 유동해석)

  • Choi, S.W.
    • 한국전산유체공학회:학술대회논문집
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    • 2007.10a
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    • pp.264-271
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    • 2007
  • The flow simulations around ducted-prop of tilt-duct aircraft were conducted in this study. For the investigation of aerodynamic characteristics of various configurations of duct, the axisymmetric flow calculation method combined with actuator disk model for prop were used. The rapid two-dimensional calculation and fast grid generation enable aerodynamic analysis for various duct configurations in a very short time and anticipated to active role in optimal configuration design of duct exposed to various flight modes. For the case of angle of attack or tilt angle, the three dimensional flow calculation is conducted using the three dimensional grid simply generated by just revolving the axisymmetric grid around center axis. Through the three dimensional calculation around duct, the aerodynamic effectiveness of duct as a lifting surface in airplane mode was investigated. The flow calculations around the control vane (wing) installed in the rear section of duct were conducted The aerodynamic data of wing were compared with the data of the ducts to evaluate the aerodynamic effectiveness of ducts.

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LOW-SPEED AERODYNAMIC CHARACTERISTIC OF TRANSITION FLOW OVER THE NACA0012 (NACA0012 천이 유동의 저속 공력 특성 해석)

  • Jeon, Sang-Eon;Park, Soo-Hyung;Kim, Sang-Ho;Byun, Yung-Hwan;Jung, Kyung-Jin;Kang, In-Mo
    • Journal of computational fluids engineering
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    • v.15 no.3
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    • pp.1-8
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    • 2010
  • Laminar separation bubble and transitional flow over the NACA0012 are investigated at a moderate range of Reynolds numbers. A Reynolds-Averaged Navier-Stokes code is coupled with an empirical transition model that can predict transition onset points and the length of transition region. Without solving the boundary layer equations, approximated e-N method is directly applied to the RANS code and iteratively solved together. The computational results are compared with the experimental data for the NACA0012 airfoil. Results of transition onset point and the length are compared well with experimental data and Xfoil prediction. The present RANS results show at high angles of attack better agreement with experimental data than Xfoil results using the boundary layer equations.

AERODYNAMIC ANALYSIS ON LEADING-EDGE SWEEPBACK ANGLES OF FLYING-WING CONFIGURATIONS (전익기 형상의 앞전후퇴각 변화에 따른 공력해석)

  • Lee, J.M.;Chang, J.W.
    • Journal of computational fluids engineering
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    • v.11 no.4 s.35
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    • pp.48-55
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    • 2006
  • A computational study was carried out in order to investigate aerodynamic characteristics on leading edge sweepback angles of Flying-Wing configurations. The viscous-compressible Navire-Stokes equation and Spalart-Allmaras turbulence model of the commercial CFD code were adopted for this computation analysis. This investigation examined aerodynamic characteristics of three different types of leading edge sweepback angles: $30^{\circ}C,\;35^{\circ}C\;and\;40^{\circ}C$. The freestream Mach number was M=0.80 and the angle of attack ranged from ${\alpha}=0^{\circ}C\;to\;{\alpha}=20^{\circ}C$. The results show that the increases in sweepback angle of the Flying-Wing configuration creates more efficient aerodynamic performance.

An Experimental Evaluation of the Coanda Jet Applied High Efficient Rudder System for VLCC

  • Park, Bong-Joon;Kim, Hyo-Chul
    • Journal of Ship and Ocean Technology
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    • v.8 no.2
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    • pp.1-12
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    • 2004
  • To keep the ocean environment from pollutions, strict international requirements on the controllability are arisen to the VLCC. Especially in low speed operations near the harbor, the VLCC is often supported by tug to replenish the insufficient rudder force. When water jet is blown to the flapped rudder, the Coanda effect induces a high-lift force by delaying stall and re-enforcing circulation in a large angle of attack (Lachmann 1961, Ahn 2003). Based on numerous research efforts, the rudder system supported by the Coanda effect was devised and its performances were evaluated in the towing tank for a large VLCC model. Hydrodynamic forces acting on the rudder system were measured with a water jet blowing on the rudder surface and compared with those acting on a conventional rudder. The effectiveness of the new rudder system was proven through an experimental evaluation.

Review on the Shock Characteristics of the MIL-S-901 Medium Weight Shock Machine (MIL-S-901 중간중량 충격시험기의 하중특성에 관한 고찰)

  • Chung, J.H.;Kim, B.H.;Huh, Y.C.
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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    • 2000.06a
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    • pp.1149-1153
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    • 2000
  • All critical equipment installed aboard naval ships and submarines is required to be shock-qualified by tests on the MIL-S-901 shock test machines where testing is practical. The intent of the shock requirements is to produce combat vessels which are resistant to the underwater explosion weapon attack. To efficiently design equipment for passing a series of shock tests, the shock environment of the shock test machine should be clearly identified. In this paper, the shock characteristics of the MIL-S-901 Medium Weight Shock Machine(MWSM) are reviewed, based on the existing test data. An analytical model for the MWSM is also discussed.

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Network System Survivability: A Framework of Transmission Control Protocol with Software Rejuvenation Methodology (네트워크 시스템 생존성 : 소프트웨어 재활기법을 이용한 TCP의 프레임워크)

  • Khin Mi Mi Aung;Park, Jong-Sou
    • Proceedings of the Korea Institutes of Information Security and Cryptology Conference
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    • 2003.07a
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    • pp.121-125
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    • 2003
  • In this paper, we propose a framework of Transmission Control Protocol with Software Rejuvenation methodology, which is applicable for network system survivability. This method is utilized to improve the survivability because it can limit the damage caused by successful attacks. The main objectives are to detect intrusions in real time, to characterize attacks, and to survive in face of attacks. To counter act the attacks' attempts or intrusions, we perform the Software Rejuvenation methods such as killing the intruders' processes in their tracks, halting abuse before it happens, shutting down unauthorized connection, and responding and restarting in real time. These slogans will really frustrate and deter the attacks, as the attacker can't make their progress. This is the way of survivability to maximize the deterrence against an attack in the target environment. We address a framework to model and analyze the critical intrusion tolerance problems ahead of intrusion detection on Transmission Control Protocol (TCP).

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Wind tunnel studies of cantilever traffic signal structures

  • Cruzado, Hector J.;Letchford, Chris;Kopp, Gregory A.
    • Wind and Structures
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    • v.16 no.3
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    • pp.225-240
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    • 2013
  • The wind-induced vibrations of the mast arm of cantilever traffic signal structures can lead to the fatigue failure of these structures. Wind tunnel tests were conducted on an aeroelastic model of this type of structure. Results of these experiments indicated that when the signals have backplates, vortex shedding causes large-amplitude vibrations that could lead to fatigue failure. Vibrations caused by galloping were only observed for one particular angle of attack with the signals having backplates. No evidence for galloping, previously thought to be the dominant cause of fatigue failures in these structures, was observed.