WorldWideScience

Sample records for angle of attack

  1. Non-linear Flight Dynamics at High Angles of Attack

    DEFF Research Database (Denmark)

    Granasy, P.; Sørensen, C.B.; Mosekilde, Erik;

    1998-01-01

    The methods of nonlinear dynamics are applied to the longitudinal motion of a vectored thrust aircraft, in particular the behavior at high angles of attack. Our model contains analytic nonlinear aerodynamical coefficients based on NASA windtunnel experiments on the F-18 high-alpha research vehicle...

  2. High angle of attack aerodynamics subsonic, transonic, and supersonic flows

    CERN Document Server

    Rom, Josef

    1992-01-01

    The aerodynamics of aircraft at high angles of attack is a subject which is being pursued diligently, because the modern agile fighter aircraft and many of the current generation of missiles must perform well at very high incidence, near and beyond stall. However, a comprehensive presentation of the methods and results applicable to the studies of the complex aerodynamics at high angle of attack has not been covered in monographs or textbooks. This book is not the usual textbook in that it goes beyond just presenting the basic theoretical and experimental know-how, since it contains reference material to practical calculation methods and technical and experimental results which can be useful to the practicing aerospace engineers and scientists. It can certainly be used as a text and reference book for graduate courses on subjects related to high angles of attack aerodynamics and for topics related to three-dimensional separation in viscous flow courses. In addition, the book is addressed to the aerodynamicist...

  3. Effect of Mean Angle of Attack Modulation on Dynamic Stall

    Science.gov (United States)

    Heintz, Kyle; Corke, Thomas

    2016-11-01

    Wind tunnel experiments at M = 0 . 2 were conducted on a cambered airfoil instrumented with surface pressure transducers that was oscillated with two independent frequencies. The primary input, f1, corresponds to a range of reduced frequencies, while the slower, secondary input, f2, drives the modulation of the mean angle of attack, thus varying the stall-penetration angle, αpen. Various combinations transitioned different regimes of dynamic stall from "light" to "deep". Results suggest that when αpen is falling between consecutive cycles, the aerodynamic loads do not fully recover to the values seen when αpen is rising, even though the airfoil recedes to αpen load coefficients, aerodynamic damping, and their phase relationships to pitch angle. APS Fellow.

  4. Review of Research On Angle-of-Attack Indicator Effectiveness

    Science.gov (United States)

    Le Vie, Lisa R.

    2014-01-01

    The National Aeronautics and Space Administration (NASA) conducted a literature review to determine the potential benefits of a display of angle-of-attack (AoA) on the flight deck of commercial transport that may aid a pilot in energy state awareness, upset recovery, and/or diagnosis of air data system failure. This literature review encompassed an exhaustive list of references available and includes studies on the benefits of displaying AoA information during all phases of flight. It also contains information and descriptions about various AoA indicators such as dial, vertical and horizontal types as well as AoA displays on the primary flight display and the head up display. Any training given on the use of an AoA indicator during the research studies or experiments is also included for review

  5. Determination of the angle of attack on rotor blades

    DEFF Research Database (Denmark)

    Shen, Wen Zhong; Hansen, Martin Otto Laver; Sørensen, Jens Nørkær

    2009-01-01

    Two simple methods for determining the angle of attack (AOA) on a section of a rotor blade are proposed. Both techniques consist of employing the Biot-Savart integral to determine the influence of the bound vorticity on the velocity field. In the first technique, the force distribution along...... the blade and the velocity at a monitor point in the vicinity of the blade are assumed to be known from experiments or CFD computations. The AOA is determined by subtracting the velocity induced by the bound circulation, determined from the loading, from the velocity at the monitor point. In the second...... to be located closer to the blade, and thus to determine the AOA with higher accuracy. Data from CFD computations for flows past the Tellus 95 kW wind turbine at different wind speeds are used to test both techniques. Comparisons show that the proposed methods are in good agreement with existing techniques...

  6. Numerical study of attack angle characteristics for integrated hypersonic vehicle

    Institute of Scientific and Technical Information of China (English)

    Wei HUANG; Zhen-guo WANG

    2009-01-01

    The two-dimensional coupled implicit Navier-Stokes equations and standard k-ε viscous models are used to simulate the angle of Stack characteristics of an integrated hypersonic vehicle with a hark head configuration under three kinds of working conditions:inlet cut-off,engine through-flow,and engine ignition.Influence of each component on aero-propulsive performance of the vehicle is discussed.It is concluded that the longitudinal static stability of the vehicle is good,and there is enough lift-to-drag ratio to satisfy the flying requirement of the vehicle.At the same time,it is important to change configurations of engine and upper surface of airframe to improve aero-propulsive performance of the vehicle.

  7. EFFECT OF SWEEP ANGLE ON THE VORTICAL FLOW OVER DELTA WINGS AT AN ANGLE OF ATTACK OF 10°

    Directory of Open Access Journals (Sweden)

    JAMES BRETT

    2014-12-01

    Full Text Available CFD simulations have been used to analyse the vortical flows over sharp edged delta wings with differing sweep angles under subsonic conditions at an angle of attack of 10°. RANS simulations were validated against experimental data for a 65° sweep wing, with a flat cross-section, and the steadiness of the flow field was assessed by comparing the results against unsteady URANS and DES simulations. To assess the effect of sweep angle on the flow field, a range of sweep angles from 65° to 43° were simulated. For moderate sweep wings the primary vortex was observed to detach from the leading edge, undergoing vortex breakdown, and a weaker, replacement, "shadow" vortex was formed. The shadow vortex was observed for sweep angles of 50° and less, and resulted in reduced lift production near the wing tips loss of the stronger primary vortex.

  8. In-blade angle of attack measurement and comparison with models

    Science.gov (United States)

    Gallant, T. E.; Johnson, D. A.

    2016-09-01

    The torque generated by a wind turbine blade is dependent on several parameters, one of which is the angle of attack. Several models for predicting the angle of attack in yawed conditions have been proposed in the literature, but there is a lack of experimental data to use for direct validation. To address this problem, experiments were conducted at the University of Waterloo Wind Generation Research Facility using a 3.4 m diameter test turbine. A five-hole pressure probe was installed in a modular 3D printed blade and was used to measure the angle of attack, a, as a function of several parameters. Measurements were conducted at radial positions of r/R = 0.55 and 0.72 at tip speed ratios of λ = 5.0, 3.6, and 3.1. The yaw offset of the turbine was varied from -15° to +15°. Experimental results were compared directly to angle of attack values calculated using a model proposed by Morote in 2015. Modeled values were found to be in close agreement with the experimental results. The angle of attack was shown to vary cyclically in the yawed case while remaining mostly constant when aligned with the flow, as expected. The quality of results indicates the potential of the developed instrument for wind turbine measurements.

  9. Effects of Angle of Attack and Velocity on Trailing Edge Noise

    Science.gov (United States)

    Hutcheson, Florence V.; Brooks, Thomas F.

    2006-01-01

    Trailing edge (TE) noise measurements for a NACA 63-215 airfoil model are presented, providing benchmark experimental data for a cambered airfoil. The effects of flow Mach number and angle of attack of the airfoil model with different TE bluntnesses are shown. Far-field noise spectra and directivity are obtained using a directional microphone array. Standard and diagonal removal beamforming techniques are evaluated employing tailored weighting functions for quantitatively accounting for the distributed line character of TE noise. Diagonal removal processing is used for the primary database as it successfully removes noise contaminates. Some TE noise predictions are reported to help interpret the data, with respect to flow speed, angle of attack, and TE bluntness on spectral shape and peak levels. Important findings include the validation of a TE noise directivity function for different airfoil angles of attack and the demonstration of the importance of the directivity function s convective amplification terms.

  10. Delayed detached eddy simulations of fighter aircraft at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Guoliang Xu; Xiong Jiang; Gang Liu

    2016-01-01

    The massively separated flows over a realistic air-craft configuration at 40◦, 50◦, and 60◦angles of attack are studied using the delayed detached eddy simulation (DDES). The calculations are carried out at experimental conditions corresponding to a mean aerodynamic chord-based Reynolds number of 8.93 × 105 and Mach number of 0.088. The influ-ence of the grid size is investigated using two grids, 20.0×106 cells and 31.0 × 106 cells. At the selected conditions, the lift, drag, and pitching moment from DDES predictions agree with the experimental data better than that from the Reynolds-averaged Navier–Stokes. The effect of angle of attack on the flow structure over the general aircraft is also studied, and it is found that the dominated frequency associated with the vortex shedding process decreases with increasing angle of attack.

  11. COMPUTATION OF FIELD STRUCTURE AND AERODYNAMIC CHARACTERISTICS OF DELTA WINGS AT HIGH ANGLES OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    YANG Li-zhi; GAO Zheng-hong

    2005-01-01

    A numerical investigation of the structure of the vortical flowfield over delta wings at high angles of attack in longitudinal and with small sideslip angle is presented.Three-dimensional Navier-Stokes numerical simulations were carried out to predict the complex leeward-side flowfield characteristics that are dominated by the effect of the breakdown of the leading-edge vortices. The methods that analyze the flowfield structure quantitatively were given by using flowfield data from the computational results. In the region before the vortex breakdown, the vortex axes are approximated as being straight line. As the angle of attack increases, the vortex axes are closer to the root chord, and farther away from the wing surface. Along the vortex axes, as the adverse pressure gradients occur, the axial velocity decreases, that is, λ is negative, so the vortex is unstable, and it is possible to breakdown. The occurrence of the breakdown results in the instability of lateral motion for a delta wing, and the lateral moment diverges after a small perturbation occurs at high angles of attack. However,after a critical angle of attack is reached, the vortices breakdown completely at the wing apex, and the instability resulting from the vortex breakdown disappears.

  12. NUMERICAL STUDY OF FLOW PAST AN AXISYMMETRIC BODY WITH A RING WING AT VARIOUS ATTACK ANGLES

    Institute of Scientific and Technical Information of China (English)

    Ren An-lu; Zou Jian-feng; Dai Zhi-qian

    2003-01-01

    The laminar and turbulent flows past an axisymmetric body with a ring wing were investigated numerically at various attack angles (0°-20°) for the Reynolds numbers ranging from 103 to 107. The DDM (Domain Decomposition Method) with the Schwarz iterative method based on finite difference approximation was applied to simulate this problem. The primitive variable formulation was used for the solution of the incompressible Navier-Stoke equations. The velocity field was calculated from the unsteady momentum equation by marching in time. The continuity equation was replaced by a Poisson-type equation for the pressure with the Neumann boundary conditions. The Baldwin-Lomax model was adopted to simulate turbulence effect. The leap frog implicit iterative method was used for the time difference approximations. The computed pressure at the front stagnation point is found to have a small deviation, less than 10%, from the theoretical value. The outlet flux has a loss about 5%. The lift coefficients increase linearly with the attack angle, but for attack angles greater than 15° the lift coefficients show mild decrease. The friction drag coefficients are insensitive to the attack angles, but the pressure drag coefficients increase markedly with the attack angles. In addition, complex flow patterns are revealed within the vicinity of the ring wing.

  13. Doppler radiation sensing of Shuttle angle of attack and TAS during entry

    Science.gov (United States)

    Foale, C. M.

    Space Shuttle true airspeed, angle of attack, and sideslip angle are currently derived from inertial guidance information. A new method is proposed which offers a potential improvement in Shuttle safety during entry. Angle of attack, sideslip angle and true airspeed could be measured directly at heights from 120 km down to 20 km by Doppler sensing three independent true airspeeds along the Shuttle body axes. Two types of Doppler measurement sensors, employing either passive detection of atmospheric radiation or coherent detection of scattered laser light are discussed. The proposed technique is essentially solid-state and robust, and is well suited for use in future small hypersonic vehicles that require flight control in the Upper Atmosphere of the earth or in probes destined for the other planets.

  14. Magnus effects at high angles of attack and critical Reynolds numbers

    Science.gov (United States)

    Seginer, A.; Ringel, M.

    1983-01-01

    The Magnus force and moment experienced by a yawed, spinning cylinder were studied experimentally in low speed and subsonic flows at high angles of attack and critical Reynolds numbers. Flow-field visualization aided in describing a flow model that divides the Magnus phenomenon into a subcritical region, where reverse Magnus loads are experienced, and a supercritical region where these loads are not encountered. The roles of the spin rate, angle of attack, and crossflow Reynolds number in determining the boundaries of the subcritical region and the variations of the Magnus loads were studied.

  15. Surface pressure model for simple delta wings at high angles of attack

    Indian Academy of Sciences (India)

    A A Pashilkar

    2001-12-01

    A new aerodynamic modelling approach is proposed for the longitudinal static characteristics of a simple delta wing. It captures the static variation of normal force and pitching moment characteristics throughout the angle of attack range. The pressure model is based on parametrizing the surface pressure distribution on a simple delta wing. The model is then extended to a wing/body combination where body-alone data are also available. The model is shown to be simple and consistent with experimental data. The pressure model can be used as a first approximation for the load estimation on the delta wing at high angles of attack.

  16. Lattice Boltzmann Method used for the aircraft characteristics computation at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    Traditional Finite Volume Method(FVM)and Lattice Boltzmann Method(LBM)are both used to compute the high angle attack aerodynamic characteristics of the benchmark aircraft model named CT-1.Even though the software requires flow on the order of Ma<0.4,simulation at Ma=0.5 is run in PowerFLOW after theoretical analysis.The consistency with the wind tunnel testing is satisfied,especially for the LBM which can produce perfect results at high angle attack.PowerFLOW can accurately capture the detail of flows because it is inherently time-dependent and parallel and suits large-scale computation very well.

  17. Bifurcation analysis of polynomial models for longitudinal motion at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Shi Zhongke; Fan Li

    2013-01-01

    To investigate the longitudinal motion stability of aircraft maneuvers conveniently,a new stability analysis approach is presented in this paper.Based on describing longitudinal aerodynamics at high angle-of-attack (α < 50°) motion by polynomials,a union structure of two-order differential equation is suggested.By means of nonlinear theory and method,analytical and global bifurcation analyses of the polynomial differential systems are provided for the study of the nonlinear phenomena of high angle-of-attack flight.Applying the theories of bifurcations,many kinds of bifurcations,such as equilibrium,Hopf,homoclinic (heteroclinic) orbit and double limit cycle bifurcations are discussed and the existence conditions for these bifurcations as well as formulas for calculating bifurcation curves are derived.The bifurcation curves divide the parameter plane into several regions; moreover,the complete bifurcation diagrams and phase portraits in different regions are obtained.Finally,our conclusions are applied to analyzing the stability and bifurcations of a practical example of a high angle-of-attack flight as well as the effects of elevator deflection on the asymptotic stability regions of equilibrium.The model and analytical methods presented in this paper can be used to study the nonlinear flight dynamic of longitudinal stall at high angle of attack.

  18. Investigation on high angle of attack characteristics of hypersonic space vehicle

    Institute of Scientific and Technical Information of China (English)

    HUANG Wei; LI ShiBin; LIU Jun; WANG ZhenGuo

    2012-01-01

    The high angle of attack characteristics play an important role in the aerodynamic performances of the hypersonic space vehicle.The three-dimensional Reynolds Averaged Navier-Stokes (RANS) equations and the two-equation RNG k-ε turbulence model have been employed to investigate the influence of the high angle of attack on the lift-to-drag ratio and the flow field characteristics of the hypersonic space vehicle,and the contributions of each component to the aerodynamic forces of the vehicle have been discussed as well.At the same time,in order to validate the numerical method,the predicted results have been compared with the available experimental data of a hypersonic slender vehicle,and the grid independency has been analyzed.The obtained results show that the predicted lift-to-drag ratio and pitching moment coefficient show very good agreement with the experimental data in the open literature,and the grid system makes only a slight difference to the numerical results.There exists an optimal angle of attack for the aerodynamic performance of the hypersonic space vehicle,and its value is 20°.When the angle of attack is 20°,the high pressure does not leak from around the leading edge to the upper surface.With the further increasing of the angle of attack,the high pressure spreads from the wing tips to the central area of the vehicle,and overflows from the leading edge again.Further,the head plays an important role in the drag performance of the vehicle,and the lift percentage of the flaperon is larger than that of the rudderevator.This illustrates that the optimization of the flaperon configuration is a great work for the improvement of the aerodynamic performance of the hypersonic space vehicle,especially for a high lift-to-drag ratio.

  19. Wing-Alone Aerodynamic Characteristics to High Angles of Attack at Subsonic and Transonic Speeds.

    Science.gov (United States)

    1982-11-01

    indicators of symmetry since the wings were unbanked within the limits of tolerances and flow angularity. Longitudinal, spanwise, and vertical... unbanked wings at subsonic and transonic speeds from low to high angles of attack. The wing planforms varied in aspect ratio and taper ratio with

  20. Stability Analysis of Hypersonic Boundary Layer over a Cone at Small Angle of Attack

    Directory of Open Access Journals (Sweden)

    Feng Ji

    2014-04-01

    Full Text Available An investigation on the stability of hypersonic boundary layer over a cone at small angle of attack has been performed. After obtaining the steady base flow, linear stability theory (LST analysis has been made with local parallel assumption. The growth rates of the first mode and second mode waves at different streamwise locations and different azimuthal angles are obtained. The results show that the boundary layer stability was greatly influenced by small angles of attack. The maximum growth rate of the most unstable wave on the leeward is larger than that on the windward. Moreover, dominating second mode wave starts earlier on the leeward than that on the windward. The LST result also shows that there is a “valley” region around 120°~150° meridian in the maximum growth rates curve.

  1. Prediction of forces and moments on finned bodies at high angle of attack in transonic flow

    Energy Technology Data Exchange (ETDEWEB)

    Oberkampf, W. L.

    1981-04-01

    This report describes a theoretical method for the prediction of fin forces and moments on bodies at high angle of attack in subsonic and transonic flow. The body is assumed to be a circular cylinder with cruciform fins (or wings) of arbitrary planform. The body can have an arbitrary roll (or bank) angle, and each fin can have individual control deflection. The method combines a body vortex flow model and lifting surface theory to predict the normal force distribution over each fin surface. Extensive comparisons are made between theory and experiment for various planform fins. A description of the use of the computer program that implements the method is given.

  2. Qualitative evaluation of a flush air data system at transonic speeds and high angles of attack

    Science.gov (United States)

    Larson, Terry J.; Whitmore, Stephen A.; Ehernberger, L. J.; Johnson, J. Blair; Siemers, Paul M., III

    1987-01-01

    Flight tests were performed on an F-14 aircraft to evaluate the use of flush pressure orifices on the nose section for obtaining air data at transonic speeds over a large range of flow angles. This program was part of a flight test and wind tunnel program to assess the accuracies of such systems for general use on aircraft. It also provided data to validate algorithms developed for the shuttle entry air data system designed at NASA Langley. Data were obtained for Mach numbers between 0.60 and 1.60, for angles of attack up to 26.0 deg, and for sideslip angles up to 11.0 deg. With careful calibration, a flush air data system with all flush orifices can provide accurate air data information over a large range of flow angles. Several orificies on the nose cap were found to be suitable for determination of stagnation pressure. Other orifices on the nose section aft of the nose cap were shown to be suitable for determination of static pressure. Pairs of orifices on the nose cap provided the most sensitive measurements for determining angles of attack and sideslip, although orifices located farther aft on the nose section could also be used.

  3. Evaluation of electrolytic tilt sensors for measuring model angle of attack in wind tunnel tests

    Science.gov (United States)

    Wong, Douglas T.

    1992-01-01

    The results of a laboratory evaluation of electrolytic tilt sensors as potential candidates for measuring model attitude or angle of attack in wind tunnel tests are presented. The performance of eight electrolytic tilt sensors was compared with that of typical servo accelerometers used for angle-of-attack measurements. The areas evaluated included linearity, hysteresis, repeatability, temperature characteristics, roll-on-pitch interaction, sensitivity to lead-wire resistance, step response time, and rectification. Among the sensors being evaluated, the Spectron model RG-37 electrolytic tilt sensors have the highest overall accuracy in terms of linearity, hysteresis, repeatability, temperature sensitivity, and roll sensitivity. A comparison of the sensors with the servo accelerometers revealed that the accuracy of the RG-37 sensors was on the average about one order of magnitude worse. Even though a comparison indicates that the cost of each tilt sensor is about one-third the cost of each servo accelerometer, the sensors are considered unsuitable for angle-of-attack measurements. However, the potential exists for other applications such as wind tunnel wall-attitude measurements where the errors resulting from roll interaction, vibration, and response time are less and sensor temperature can be controlled.

  4. DSMC simulation for effects of angles of attack on rarefied hypersonic cavity flows

    Science.gov (United States)

    Jin, Xuhon; Huang, Fei; Shi, Jiatong; Cheng, Xiaoli

    2016-11-01

    The present work investigates rarefied hypersonic flows over a flat plate with two-dimensional and three-dimensional cavities by employing the direct simulation Monte Carlo (DSMC) method, focusing on the effect of angles of attack (AOAs) on flow structure inside the cavity and aerodynamic surface quantities. It was found that only one primary recirculation structure was formed inside the cavity at the angle of attack (AOA) of 0°, while a second vortex system was produced just beneath the primary one with the angle of attack increased to 30°. As AOAs grow, the freestream flow is able to penetrate deeper into the cavity and attach itself to the cavity base, making the "dead-water" region shrink. Meantime, with the increment in the AOA, both heat transfer and pressure coefficients show a similar and gradual quantitative behavior, and along centerlines of the two side surfaces of the cavity, both pressure and heat transfer coefficients become growing, indicating that the increase in the AOA does enhance momentum and energy transfer to both the two aforementioned surfaces. However, the heat flux over the cavity floor does not keep increasing with the growth of the AOA, while the pressure does, indicating that augmenting AOAs does not enhance momentum to the cavity floor, but does make compressibility stronger and stronger near the cavity base.

  5. Study on flow behavior and structure over chined fuselage at high angle of attack

    Institute of Scientific and Technical Information of China (English)

    2010-01-01

    A study of leeward vortex structure over chined fuselage and the effects of micro tip perturbation on its vortex flow have been carried out in wind tunnel experiments at Reynolds numbers from 1.26×105 to 5.04×105 with PIV and pressure measurement techniques.Firstly,the experiment results have proved that micro tip perturbation has no effects on the vortex flow and its aerodynamic characteristics over chined fuselage at high angle of attack,in which there are not any non-deterministic flow behaviors.Secondly,the evolution of leeward vortex structure over chined fuselage along the axis of model can be divided into four flow regimes:linear conical developed regime,decay regime of leeward vortex intensity,asymmetric leeward vortex break down regime and completely break down regime.And a correlation between leeward vortex structure and sectional aerodynamic force was also revealed in the present paper.Thirdly,the experiment results show the behavior of leeward vortex core trajectories and zonal characteristics of leeward vortex structure with angles of attack.Finally,the experiment results of Reynolds number effect on the leeward vortex flow have further confirmed research conclusions from previous studies:the flows over chined fuselage at high angles of attack are insensitive to variation of Reynolds number,and there is a little effect on the secondary boundary layer separation and the suction peak induced by leeward vortex.

  6. Hydrodynamic performance of a vertical-axis tidal-current turbine with different preset angles of attack

    Institute of Scientific and Technical Information of China (English)

    ZHAO Guang; YANG Ran-sheng; LIU Yan; ZHAO Peng-fei

    2013-01-01

    The instantaneous angle of attack on the blade has a significant effect on the hydrodynamic performance of a vertical-axis tidal-current turbine with straight blades.This paper investigates the influence of different preset angles of attack on the hydrodynamic performance of a three-bladed,vertical-axis,tidal-current turbine both experimentally and numerically.Experiments are carried out in a towing tank.This tested turbine's solidity is 0.1146.The preset angles of attack on the blade are-3°,0°,3°,and 5°,in the experiments.Experimental results show that with the increase of the preset angle of attack from-3°,to 5°,the hydrodynamic performance of the turbine is improved significantly with the power coefficients being increased from 15.3% to 34.8%,respectively.Compared to the result of a 0° preset angle of attack,the performance of the turbine with positive preset angles of attack is experimentally demonstrated to be beneficial.This performance improvement is also shown by numerical simulations based on the Unsteady Reynolds Averaged Navier-Stokes (URANS) equations.In addition,the numerical results show that the optimal positive preset angle of attack is 7° for the turbine studied.The corresponding power coefficient is 38%.Beyond this optimal preset angle of attack,the hydrodynamic performance of the turbine decreases.Therefore,due to the dynamic stall phenomenon,an optimal preset angle of attack exists for any vertical-axis turbine.This value should be considered in the design of a vertical-axis tidal-current turbine.

  7. Penetration and impact resistance of PDC cutters inclined at different attack angles

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    In order to develop a rotary-percussive bit with diamond-enhanced cutters assisted by high pressure water jets,it is necessary to study the damage mechanism and the penetration properties of PDC cutters subject to different impactload level and rock types. Therefore the impact experiments of the single PDC cutters with different attack angles in fourrocks: black basalt, Missouri red granite, Halston limestone, and a very soft (Roubidoux) sandstone were carried out,and the effects of rake angles of PDC cutters on both the penetration and impact resistance of PDC cutters have been discussed in detail. Test results show that a PDC insert can withstand a very strong impact in compression but is easily damaged by impact shearing, the PDC cutters are more easily damaged by shearing if the attack angles are relatively small, the45 PDC cutters have the least penetration resistance among the cutters tested. Thus it is suggested that the attack anglesof PDC cutters should be larger than 30 for bits which must withstand impact from a hammer

  8. Investigation of normal force and moment coefficients for an AUV at nonlinear angle of attack and sideslip range

    Digital Repository Service at National Institute of Oceanography (India)

    Barros, E.A. de; Dantas, J.L.D.; Pascoal, A.M.; Desa, E.S.

    of angles of attack considered. In contrast with the traditional ASE formulations used in naval and aircraft fields, an improved methodology is introduced that takes advantage of the qualitative information obtained from CFD flow visualizations...

  9. Computer programs for calculation of sting pitch and roll angles required to obtain angles of attack and sideslip on wind tunnel models

    Science.gov (United States)

    Peterson, John B., Jr.

    1988-01-01

    Two programs have been developed to calculate the pitch and roll angles of a wind-tunnel sting drive system that will position a model at the desired angle of attack and and angle of sideslip in the wind tunnel. These programs account for the effects of sting offset angles, sting bending angles and wind-tunnel stream flow angles. In addition, the second program incorporates inputs from on-board accelerometers that measure model pitch and roll with respect to gravity. The programs are presented in the report and a description of the numerical operation of the programs with a definition of the variables used in the programs is given.

  10. Quasi-periodic dynamics of a high angle of attack aircraft

    Science.gov (United States)

    Rohith, G.; Sinha, Nandan K.

    2017-01-01

    High angle of attack maneuvers closer to stall is a commonly accessed flight regime especially in case of fighter aircrafts. Stall and post-stall dynamics are dominated by nonlinearities which make the analysis difficult. Presence of external factors such as wind makes the system even more complex. Rich nonlinearities point to the possibility of existence of chaotic solutions. Past studies in this area confirm the development of such solutions. These studies are mainly concentrated on very high angle of attack regimes, which may not be practically easily accessible. This paper examines the possibility of existence of chaotic solutions in the lower, more accessible areas in the post stall domain. The analysis is composed of the study of effect of external wind as an agent to drive the system towards the possibility of a chaotic solution. Investigations reveal presence of quasi-periodic solutions, which are characterized by two incommensurate frequencies. This solution appears in the time simulation by varying the control parameter viz., wind. The solutions correspond to the values in the lower region of the angle of attack versus elevator bifurcation curve in the post-stall region. A steady wind is considered for the analysis and explores the possibility of chaotic motion by increasing the wind in a step wise manner. It is found that wind adds extra energy to the system which in turn drives the system in to chaos. The analysis is done with the help of phase portrait, Poincare map and amplitude spectrum and a quasi-periodic route to chaos via torus doubling is also presented.

  11. Mechanism of transition in a hypersonic sharp cone boundary layer with zero angle of attack

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Firstly, the steady laminar flow field of a hypersonic sharp cone boundary layer with zero angle of attack was computed. Then, two groups of finite amplitude T-S wave disturbances were introduced at the entrance of the computational field, and the spatial mode transition process was studied by direct numerical simulation (DNS) method.The mechanism of the transition process was analyzed. It was found that the change of the stability characteristics of the mean flow profile was the key issue. Furthermore, the characteristics of evolution for the disturbances of different modes in the hypersonic sharp cone boundary layer were discussed.

  12. Effects of Sudden Changes in Inflow Conditions on the Angle of Attack on HAWT Blades

    CERN Document Server

    Stoevesandt, Bernhard

    2010-01-01

    In this paper changes in wind speed and wind direction from a measured wind field are being analyzed at high frequencies. This is used to estimate changes in the angle of attack (AOA) on a blade segment over short time periods for different estimated turbine concepts. Here a statistical approach is chosen to grasp the characteristics of the probability distributions to give an over all view of the magnitude and rate of the changes. The main interest is the generation of basic distributions for the calculation of dynamic stall effects and stall flutter due to wind fluctuations.

  13. Parametric approximation of airfoil aerodynamic coefficients at high angles of attack

    DEFF Research Database (Denmark)

    Skrzypinski, Witold Robert; Zahle, Frederik; Bak, Christian

    2014-01-01

    , and the third method, also utilizing trigonometric functions, was developed with the scope on stall-regulated turbines. The method of the even sine and cosine functions was further developed in the present work by using two independent harmonic approximations in the positive and negative α regions......Three methods for estimating the lift and drag curves in the 360° angle of attack (α) range with harmonic approximation functions were analyzed in the present work. The first method assumes aerodynamic response of a flat plate, the second utilizes even sine and even cosine approximation functions...

  14. Study of optical techniques for the Ames unitary wind tunnels. Part 3: Angle of attack

    Science.gov (United States)

    Lee, George

    1992-01-01

    A review of optical sensors that are capable of accurate angle of attack measurements in wind tunnels was conducted. These include sensors being used or being developed at NASA Ames and Langley Research Centers, Boeing Airplane Company, McDonald Aircraft Company, Arnold Engineering Development Center, National Aerospace Laboratory of the Netherlands, National Research Council of Canada, and the Royal Aircraft Establishment of England. Some commercial sensors that may be applicable to accurate angle measurements were also reviewed. It was found that the optical sensor systems were based on interferometers, polarized light detector, linear or area photodiode cameras, position sensing photodetectors, and laser scanners. Several of the optical sensors can meet the requirements of the Ames Unitary Plan Wind Tunnel. Two of these, the Boeing interferometer and the Complere lateral effect photodiode sensors are being developed for the Ames Unitary Plan Wind Tunnel.

  15. Flight Test Techniques for Quantifying Pitch Rate and Angle of Attack Rate Dependencies

    Science.gov (United States)

    Grauer, Jared A.; Morelli, Eugene A.; Murri, Daniel G.

    2017-01-01

    Three different types of maneuvers were designed to separately quantify pitch rate and angle of attack rate contributions to the nondimensional aerodynamic pitching moment coefficient. These maneuvers combined pilot inputs and automatic multisine excitations, and were own with the subscale T-2 and Bat-4 airplanes using the NASA AirSTAR flight test facility. Stability and control derivatives, in particular C(sub mq) and C(sub m alpha(.)) were accurately estimated from the flight test data. These maneuvers can be performed with many types of aircraft, and the results can be used to increase simulation prediction fidelity and facilitate more accurate comparisons with wind tunnel experiments or numerical investigations.

  16. Transition prediction for supersonic and hypersonic boundary layers on a cone with angle of attack

    Institute of Scientific and Technical Information of China (English)

    SU CaiHong; ZHOU Heng

    2009-01-01

    Transition prediction for boundary layers has always been one of the urgent problems waiting for a solution for the development of aero-space technology, yet there is no reliable and effective method due to the complexity of the problem. The eN method has been regarded as an effective method for the transition prediction of boundary layers. However, it heavily relies on experiment or experience. And in cases with three-dimensional base flow, for instance, the boundary layer on a cone with angle of attack, the result of its application is not satisfactory. The authors have found its cause and proposed the method for its improvement, which did yield the fairly satisfactory result for a given test case, and also did not rely so much on experiment or experience. However, before people can really apply this method to practical problems, more test cases have to be studied. In this paper, more test cases for the appli- cation of the improved eN method to problems of transition prediction of supersonic and hypersonic boundary layers on cones with angle of attack will be studied. The results are compared with those obtained by experiments and/or direct numerical simulations, confirming that the improved eN method is effective and reliable. We also find that there may be more than one ZARF for each meridian plane, and which one should be chosen for the eN method has been clarified.

  17. Design of Optimal Attack-Angle for RLV Reentry Based on Quantum Particle Swarm Optimization

    Directory of Open Access Journals (Sweden)

    Qingzhen Zhang

    2014-04-01

    Full Text Available The attack-angle optimization is a key problem for reentry trajectory design of a gliding type reusable launch vehicle (RLV. In order to solve such a problem, the equations of motion are derived first. A physical programming (PP method is briefly presented and the preference function is reflected in mathematical representation. The attack-angle optimization problem with four criteria (i.e., downrange, total heat, heat rate, and trajectory oscillation is converted into a single-objective optimization problem based on the PP method. A winged gliding reentry RLV is chosen as a simulation example and the transformed single-objective problem is solved by the quantum-behaved particle swarm optimization (QPSO algorithm based on two types of preference structures, longer range preference and smaller total heat preference. The constraints of maximizing heating rate, normal load factor, and dynamic pressure and minimizing terminal velocity are handled by a penalty function method. The simulation results demonstrate the efficiency of these methods. The physical causation of the optimal solution and the typical profiles are presented, which reflect the designer's preference. At last, the feasibility and advantages of QPSO are revealed by comparison with the results of genetic algorithm (GA and standard particle swarm optimization (PSO algorithm on this optimization problem.

  18. Low-frequency unsteadiness of vortex wakes over slender bodies at high angle of attack

    Directory of Open Access Journals (Sweden)

    Ma Baofeng

    2014-08-01

    Full Text Available A type of flow unsteadiness with low frequencies and large amplitude was investigated experimentally for vortex wakes around an ogive-tangent cylinder. The experiments were carried out at angles of attack of 60–80° and subcritical Reynolds numbers of 0.6–1.8 × 105. The reduced frequencies of the unsteadiness are between 0.038 and 0.072, much less than the frequency of Karman vortex shedding. The unsteady flow induces large fluctuations of sectional side forces. The results of pressure measurements and particle image velocimetry indicate that the flow unsteadiness comes from periodic oscillation of the vortex wakes over the slender body. The time-averaged vortex patterns over the slender body are asymmetric, whose orientation is dependent on azimuthal locations of tip perturbations. Therefore, the vortex oscillation is a type of unsteady oscillation around a time-averaged asymmetric vortex structure.

  19. Evaluation of electrolytic tilt sensors for wind tunnel model angle-of-attack (AOA) measurements

    Science.gov (United States)

    Wong, Douglas T.

    1991-01-01

    The results of a laboratory evaluation of three types of electrolytic tilt sensors as potential candidates for model attitude or angle of attack (AOA) measurements in wind tunnel tests are presented. Their performance was also compared with that from typical servo accelerometers used for AOA measurements. Model RG-37 electrolytic tilt sensors were found to have the highest overall accuracy among the three types. Compared with the servo accelerometer, their accuracies are about one order of magnitude worse and each of them cost about two-thirds less. Therefore, the sensors are unsuitable for AOA measurements although they are less expensive. However, the potential for other applications exists where the errors resulting from roll interaction, vibration, and response time are less, and sensor temperature can be controlled.

  20. Flight validation of ground-based assessment for control power requirements at high angles of attack

    Science.gov (United States)

    Ogburn, Marilyn E.; Ross, Holly M.; Foster, John V.; Pahle, Joseph W.; Sternberg, Charles A.; Traven, Ricardo; Lackey, James B.; Abbott, Troy D.

    1994-01-01

    A review is presented in viewgraph format of an ongoing NASA/U.S. Navy study to determine control power requirements at high angles of attack for the next generation high-performance aircraft. This paper focuses on recent flight test activities using the NASA High Alpha Research Vehicle (HARV), which are intended to validate results of previous ground-based simulation studies. The purpose of this study is discussed, and the overall program structure, approach, and objectives are described. Results from two areas of investigation are presented: (1) nose-down control power requirements and (2) lateral-directional control power requirements. Selected results which illustrate issues and challenges that are being addressed in the study are discussed including test methodology, comparisons between simulation and flight, and general lessons learned.

  1. Identification of variations of angle of attack and lift coefficient for a large horizontal-axis wind turbine

    DEFF Research Database (Denmark)

    Rezaeiha, Abdolrahim; Arjomandi, Maziar; Kotsonis, Marios;

    2015-01-01

    The current paper investigates the effects of various elements including turbulence, wind shear, yawed inflow, tower shadow, gravity, mass and aerodynamic imbalances on variations of angle of attack and lift coefficient for a large horizontal-axis wind turbine. It will identify the individual...... and the aggregate effect of elements on variations of mean value and standard deviation of the angle of attack and lift coefficient in order to distinguish the major contributing factors. The results of the current study is of paramount importance in the design of active load control systems for wind turbine....

  2. A computational/experimental study of the flow around a body of revolution at angle of attack

    Science.gov (United States)

    Zilliac, Gregory G.

    1986-01-01

    The incompressible Navier-Stokes equations are numerically solved for steady flow around an ogive-cylinder (fineness ration 4.5) at angle of attack. The three-dimensional vortical flow is investigated with emphasis on the tip and the near wake region. The implicit, finite-difference computation is performed on the CRAY X-MP computer using the method of pseudo-compressibility. Comparisons of computational results with results of a companion towing tank experiment are presented for two symmetric leeside flow cases of moderate angles of attack. The topology of the flow is discussed and conclusions are drawn concerning the growth and stability of the primary vortices.

  3. ASYMMETRIC VORTICES FLOW OVER SLENDER BODY AND ITS ACTIVE CONTROL AT HIGH ANGLE OF ATTACK

    Institute of Scientific and Technical Information of China (English)

    DENG Xueying; WANG Yankui

    2004-01-01

    The studies of asymmetric vortices flow over slender body and its active control at high angles of attack have significant importance for both academic field and engineering area. This paper attempts to provide an update state of art to the investigations on the fields of forebody asymmetric vortices. This review emphasizes the correlation between micro-perturbation on the model nose and its response and evolution behaviors of the asymmetric vortices. The critical issues are discussed,which include the formation and evolution mechanism of asymmetric multi-vortices; main behaviors of asymmetric vortices flow including its deterministic feature and vortices flow structure; the evolution and development of asymmetric vortices under the perturbation on the model nose; forebody vortex active control especially discussed micro-perturbation active control concept and technique in more detail. However present understanding in this area is still very limited and this paper tries to identify the key unknown problems in the concluding remarks.

  4. Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

    Directory of Open Access Journals (Sweden)

    Xin Qi

    2015-02-01

    Full Text Available Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To predict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynamics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurcation and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders series of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

  5. Effect of angle of attack on the flow past a harbor seal vibrissa shaped cylinder

    Science.gov (United States)

    Kim, Hyo Ju; Yoon, Hyun Sik

    2016-11-01

    The present study considered the geometric disturbance inspired by a harbor seal vibrissa of which undulated surface structures are known as a detecting device to capture the water movement induced by prey fish. In addition, this vibrissa plays an important role to suppress vortex-induced vibration, which has been reported by the previous researches. The present study aims at finding the effect of the angle of attack (AOA) on flow characteristics around the harbor seal vibrissa shaped cylinder, since the flow direction facing the harbor seal vibrissa with the elliptic shape can be changed during the harbor seal's movements and surrounding conditions. Therefore, we considered a wide range of AOA varying from 0 to 90 degree. We carried out large eddy simulation (LES) to investigate the flow around inclined vibrissa shaped cylinder for the Reynolds number (Re) of 500 based hydraulic diameter of a harbor seal vibrissa shape. For comparison, the flow over the elliptic cylinder was also simulated according to AOA at the same Re. The vortical structures of both vibrissa shaped and elliptic cylinders have been compared to identify the fundamental mechanism making the difference flow quantities. This subject is supported by Korea Ministry of Environment (MOE) as "the Chemical Accident Prevention Technology Development Project.", National Research Foundation of Korea (NRF) Grant through GCRCSOP (No.20110030013) and (NRF-2015R1D1A3A01020867).

  6. Flow Control of the Stingray UAV at Low Angles of Attack

    Science.gov (United States)

    Farnsworth, John; Vaccaro, John; Amitay, Michael

    2007-11-01

    The effectiveness of active flow control, via synthetic jets and steady blowing jets, on the aerodynamic performance of the Stingray UAV was investigated experimentally in a wind tunnel. Global flow measurements were conducted using a six component sting balance, static pressure, and Particle Image Velocimetry (PIV) measurements. Using active control for trimming the Stingray UAV in pitch and roll at low angles of attack has similar effects to those with conventional control effectors. The synthetic jets were able to alter the local streamlines through the formation of a quasi-steady interaction region on the suction surface of the vehicle's wing. Phase locked data were acquired to provide insight into the growth, propagation, and decay of the synthetic jet impulse and its interaction with the cross-flow. The changes induced on the moments and forces can be proportionally controlled by either changing the momentum coefficient or by driving the synthetic jets with a pulse modulation waveform. This can lead the way for future development of closed-loop control models.

  7. A hybrid system approach to airspeed, angle of attack and sideslip estimation in Unmanned Aerial Vehicles

    KAUST Repository

    Shaqura, Mohammad

    2015-06-01

    Fixed wing Unmanned Aerial Vehicles (UAVs) are an increasingly common sensing platform, owing to their key advantages: speed, endurance and ability to explore remote areas. While these platforms are highly efficient, they cannot easily be equipped with air data sensors commonly found on their larger scale manned counterparts. Indeed, such sensors are bulky, expensive and severely reduce the payload capability of the UAVs. In consequence, UAV controllers (humans or autopilots) have little information on the actual mode of operation of the wing (normal, stalled, spin) which can cause catastrophic losses of control when flying in turbulent weather conditions. In this article, we propose a real-time air parameter estimation scheme that can run on commercial, low power autopilots in real-time. The computational method is based on a hybrid decomposition of the modes of operation of the UAV. A Bayesian approach is considered for estimation, in which the estimated airspeed, angle of attack and sideslip are described statistically. An implementation on a UAV is presented, and the performance and computational efficiency of this method are validated using hardware in the loop (HIL) simulation and experimental flight data and compared with classical Extended Kalman Filter estimation. Our benchmark tests shows that this method is faster than EKF by up to two orders of magnitude. © 2015 IEEE.

  8. High angle of attack: Forebody flow physics and design emphasizing directional stability

    Science.gov (United States)

    Ravi, R.

    A framework for understanding the fundamental physics of flowfields over forebody type shapes at low speed, high angle of attack conditions with special emphasis on sideslip has been established. Computational Fluid Dynamics (CFD) has been used to study flowfieids over experimentally investigated forebodies: the Lamont tangent-ogive forebody, the F-5A forebody and the Erickson chine forebody. A modified version of a current advanced code, CFL3D, was used to solve the Euler and thin-layer Navier-Stokes equations. The Navier-Stokes equations used a form of the Baldwin-Lomax turbulence model modified to account for massive crossflow separation. Using the insight provided by the solutions obtained using CFD, together with comparison with limited available data, the aerodynamics of forebodies with positive directional stability has been revealed. An unconventional way of presenting the results is used to illustrate how a positive contribution to directional stability arises. Based on this new understanding, a parametric study was then conducted to determine which shapes promote a positive contribution to directional stability. The effect of cross-sectional shape on directional stability was found to be very significant. Broad chine-shaped cross-sections were found to promote directional stability. Also, directional stability is improved if the chine is placed closer to the top of the cross-section. Planform shapes also played an important role in determining the forebody directional stability characteristics. This initial parametric study has been used to propose some guidelines for aerodynamic design to promote positive directional stability.

  9. Dynamic surface measurements on a model helicopter rotor during blade slap at high angles of attack

    Science.gov (United States)

    Hubbard, J. E., Jr.; Harris, W. L.

    1982-01-01

    The modern helicopter offers a unique operational capability to both the public and private sectors. However, the use of the helicopter may become severely limited due to the radiated noise generated by the rotor system. A description is presented of some of the experimental results obtained with a model helicopter rotor in an anechoic wind tunnel with regard to blade stall as a source mechanism of blade slap. Attention is given to dynamic rotor blade surface phenomena and the resulting far field impulsive noise from the model helicopter rotor at high angles of attack and low tip speed. The results of the investigation strongly implicates the boundary layer as playing an important role in blade slap due to blade/vortex interaction (BVI) in a highly loaded rotor. Intermittent stall cannot be ruled out as a possible source mechanism for blade slap. This implies that blade surface characteristics, airfoil shape and local Reynolds number may now be used as tools to reduce the resultant far-field sound pressure levels in helicopters.

  10. Bifurcation analysis and stability design for aircraft longitudinal motion with high angle of attack

    Institute of Scientific and Technical Information of China (English)

    Xin Qi; Shi Zhongke

    2015-01-01

    Bifurcation analysis and stability design for aircraft longitudinal motion are investigated when the nonlinearity in flight dynamics takes place severely at high angle of attack regime. To pre-dict the special nonlinear flight phenomena, bifurcation theory and continuation method are employed to systematically analyze the nonlinear motions. With the refinement of the flight dynam-ics for F-8 Crusader longitudinal motion, a framework is derived to identify the stationary bifurca-tion and dynamic bifurcation for high-dimensional system. Case study shows that the F-8 longitudinal motion undergoes saddle node bifurcation, Hopf bifurcation, Zero-Hopf bifurcation and branch point bifurcation under certain conditions. Moreover, the Hopf bifurcation renders ser-ies of multiple frequency pitch oscillation phenomena, which deteriorate the flight control stability severely. To relieve the adverse effects of these phenomena, a stabilization control based on gain scheduling and polynomial fitting for F-8 longitudinal motion is presented to enlarge the flight envelope. Simulation results validate the effectiveness of the proposed scheme.

  11. Experimental investigation of separated shear layer from a leading edge subjected to various angles of attack with tail flap deflections

    Indian Academy of Sciences (India)

    K Anand; S Sarkar

    2015-05-01

    Shear layer development over a thick flat plate with a semi-circular leading edge is investigated for a range of angles of attack under different pressure gradients for a Reynolds number of 2.44×105 (based on chord and free-stream velocity). The characteristics of the separated shear layer are very well documented through a combination of surface pressure measurement and smoke flow visualization. The instability of the separated layer occurs because of enhanced receptivity of perturbations leading to the development of significant unsteadiness and three-dimensional motions in the second-half of the bubble. The onset of separation, transition and the point of reattachment are identified for varying angles of attack and pressure gradients imposed by tail flap deflections. The data concerning bubble length, laminar portion and reattachment points agree well with the literature.

  12. Simulator study of the effectiveness of an automatic control system designed to improve the high-angle-of-attack characteristics of a fighter airplane

    Science.gov (United States)

    Gilbert, W. P.; Nguyen, L. T.; Vangunst, R. W.

    1976-01-01

    A piloted, fixed-base simulation was conducted to study the effectiveness of some automatic control system features designed to improve the stability and control characteristics of fighter airplanes at high angles of attack. These features include an angle-of-attack limiter, a normal-acceleration limiter, an aileron-rudder interconnect, and a stability-axis yaw damper. The study was based on a current lightweight fighter prototype. The aerodynamic data used in the simulation were measured on a 0.15-scale model at low Reynolds number and low subsonic Mach number. The simulation was conducted on the Langley differential maneuvering simulator, and the evaluation involved representative combat maneuvering. Results of the investigation show the fully augmented airplane to be quite stable and maneuverable throughout the operational angle-of-attack range. The angle-of-attack/normal-acceleration limiting feature of the pitch control system is found to be a necessity to avoid angle-of-attack excursions at high angles of attack. The aileron-rudder interconnect system is shown to be very effective in making the airplane departure resistant while the stability-axis yaw damper provided improved high-angle-of-attack roll performance with a minimum of sideslip excursions.

  13. Development of microprocessor-based laser velocimeter and its application to measurement of jet exhausts and flows over missiles at high angles of attack

    Science.gov (United States)

    Harwell, K. E.; Farmer, W. M.; Hornkohl, J. O.; Stallings, E.

    1981-03-01

    During the past three years, personnel have developed a unique three-component laser velocimeter for the in situ measurement of particle and/or gas velocities in flow fields produced behind bodies at high angles of attack and in jet exhaust plumes. This report describes the development of the laser velocimeter and its subsequent application of the measurement of the velocity distribution and vortex structure in free jets and in flows over missiles at high angles of attack.

  14. The Effect of Trailing Vortices on the Production of Lift on an Airfoil Undergoing a Constant Rate of Change of Angle of Attack.

    Science.gov (United States)

    1983-12-01

    The purpose of this study was to investigate the effect a trailing vortex wake has on an airfoil undergoing a constant rate of change of angle of...When applied to the constant rate - of - change of angle-of-attack problem, the results showed that a trailing vortex wake has a measurable and

  15. Convective heat transfer over a wall mounted cube at different angle of attack using large eddy simulation

    Directory of Open Access Journals (Sweden)

    Heidarzadeh Habibollah

    2014-01-01

    Full Text Available Turbulent fluid flow and convective heat transfer over the wall mounted cube in different flow angle of attack have been studied numerically using Large Eddy Simulation. Cube faces and plate have a constant heat flux. Dynamic Smagorinsky (DS subgrid scale model were used in this study. Angles were in the range 0≤θ≤45 and Reynolds number based on the cube height and free stream velocity was 4200. The numerical simulation results were compared with the experimental data of Nakamura et al [6, 7]. Characteristics of fluid flow field and heat transfer compared for four angles of attack. Flow around the cube was classified to four regimes. Results was represented in the form of time averaged normalized streamwise velocity and Reynolds stress in different positions, temperature contours, local and average Nusselt number over the faces of cube. Local convective heat transfer on cube faces was affected by flow pattern around the cube. The local convective heat transfer from the faces of the cube and plate are directly related to the complex phenomena such as horse shoe vortex, arch vortexes in behind the cube, separation and reattachment. Results show that overall convective heat transfer of cube and mean drag coefficient have maximum and minimum value at θ=0 deg and θ=25 deg respectively.

  16. Proportional navigation law design of plane-symmetrical vehicle with terminal attack angle constraint for over target flight

    Science.gov (United States)

    Wu, Bin; Ji, Denggao; Guo, Zhenxi; Shen, Haibin; Zhang, Jianfei

    2016-11-01

    This article proposes a type of proportional navigation law design of plane-symmetrical vehicle with terminal attack angle constraint for over target flight. Firstly, the line of sight rotating rate and the velocity rotating rate model of the vehicle are expressed. Then, the attitude of the vehicle is constructed by the acceleration vector requirement of proportional navigation law. Accordingly, the guidance command uncertain issue can be avoided for plane-symmetrical vehicle over target flight. It guarantees high precision to hit the target. The effect and efficiency of the guidance law are shown by simulations of characteristic trajectories.

  17. Vortex-induced vibrations of a DU96-W-180 airfoil at 90° angle of attack

    DEFF Research Database (Denmark)

    Skrzypinski, Witold Robert; Gaunaa, Mac; Sørensen, Niels N.;

    2014-01-01

    This work presents an analysis of vortex-induced vibrations of a DU96-W-180 airfoil in deep stall at a 90 degrees angle of attack, based on 2D and 3D Reynolds Averaged Navier Stokes and 3D Detached Eddy Simulation unsteady Computational Fluid Dynamics computations with non-moving, prescribed motion...... and elastically mounted airfoil suspensions. Stationary vortex-shedding frequencies computed in 2D and 3D Computational Fluid Dynamics differed. In the prescribed motion computations, the airfoil oscillated in the direction of the chord line. Negative aerodynamic damping, found in both 2D and 3D Computational...... Fluid Dynamics computations with moving airfoil, showed in the vicinity of the stationary vortex-shedding frequency computed by 2D Computational Fluid Dynamics. A shorter time series was sufficient to verify the sign of the aerodynamic damping in the case of the elastic computations than the prescribed...

  18. Development of a method of analysis and computer program for calculating the inviscid flow about the windward surfaces of space shuttle configurations at large angles of attack

    Science.gov (United States)

    Maslen, S. H.

    1974-01-01

    A general method developed for the analysis of inviscid hypersonic shock layers is discussed for application to the case of the shuttle vehicle at high (65 deg) angle of attack. The associated extensive subsonic flow region caused convergence difficulties whose resolution is discussed. It is required that the solution be smoother than anticipated.

  19. Experimental study of heat transfer enhancement in solar air heater with different angle of attack of V-down continuous ribs

    Science.gov (United States)

    Istanto, Tri; Danardono, Dominicus; Yaningsih, Indri; Wijayanta, Agung Tri

    2016-06-01

    In this paper, an experimental study on the effect of angle attack in V-down continuous ribs on heat transfer and friction factor in an artificially roughened air heater duct is presented. The electric heater with a constant heat flux as a simulation of the indoor testing solar air heater is used to heat the roughened part of rectangular duct while other parts were insulated. The system and operating conditions were used to decide the range of parameters for the study. The ratio of the width to height of the duct (W/H) was 12, the relative roughness pitch (p/e) was 10, the relative roughness height (e/Dh) was 0.033 and the angle of attack of flow (α) was 30-80°. The air flow rate corresponded to Reynolds number between 3500 -10,000. The result of heat transfer and friction factor had been compared to those for smooth duct under similar flow and thermal boundary condition. The thermo-hydraulic performance also had been considered. As a result, the maximum enhancement of Nusselt number (Nu) and friction factor(f) were 2.34 and 2.45 times, respectively. For each variation of angle attack of flow, the thermo-hydraulic performance has been compared and the result shows that a V-down continuous rib with the angle of attack of flow as 60° gave the best thermo-hydraulic performance.

  20. An evaluation of several methods of determining the local angle of attack on wind turbine blades

    DEFF Research Database (Denmark)

    Guntur, Srinivas; Sørensen, Niels N.

    2014-01-01

    existing as well as new full rotor CFD computations of the MEXICO rotor are used in this analysis. A more accurate estimation of the AOA is possible from 3D full rotor CFD computations, but when working with experimental data, pressure measurements and sectional forces are often the only data available....... The aim of this work is to analyse the reliability of some of the simpler methods of estimating the 3D effective AOA compared some of the more rigorous CFD based methods....

  1. Numerical Simulation of Turbulent Flow Over of Semi-Cylindrical Profile at Zero Angle of Attack

    Directory of Open Access Journals (Sweden)

    Shebelev Alexander

    2016-01-01

    Full Text Available Results of unsteady two-dimensional numerical simulations for the turbulent flow over the semi-cylindrical profile at Reynolds number 45000 are presented. Three different turbulence RANS eddy viscosity models are used for the simulation. The calculations show the formation of alternating large-scale vortices shed in the wake of the body. The calculated averaged pressure distribution on the contour demonstrate a good agreement with the experimental data. A series of calculations have been performed for the estimation of influence of mesh resolution in the wake of streamlined body on the unsteady solution accuracy. It was found that a mesh size ~0.04 of chord length is sufficient to resolve the vortex street.

  2. Investigation of the High Angle of Attack Dynamics of the F-15B Using Bifurcation Analysis

    Science.gov (United States)

    1990-12-01

    region via limit points should not be expected due to asymmetric thrust alone. A large I perturbation may push the F-15 away from the stable branch and...engine thrust setting of 25,000 lbf was then tried in the simu- 3 lation. Fig. 5-16 shows that using the higher thrust asym- metry, the F-15 pushes ...ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION Air Force Institute of Tecnology REPORT NUMBER I WPAFB, OH 45433-6583 AFIT/GAE/ENY/90D-16 9

  3. Effects of wall cooling and angle of attack on boundary layer transition on sharp cones at free stream Mach 7.4

    Science.gov (United States)

    Mateer, G. G.

    1972-01-01

    Tests were conducted on 5 deg and 15 deg half-angle sharp cones at wall-to-total-temperature ratios of 0.08 to 0.4, and angles of attack from 0 deg to 20 deg. The results indicate that (1) transition Reynolds numbers decrease with decreasing temperature ratio, (2) local transition Reynolds numbers decrease from the windward to the leeward side of the model, and (3) transition data on the windward ray of cones can be correlated in terms of the crossflow velocity gradient, momentum thickness Reynolds number, local Mach number, and cone half-angle.

  4. Aerodynamic coefficients of plain and helically filleted twin circular cylinders for varying wind angles of attack

    DEFF Research Database (Denmark)

    Acampora, Antonio; Georgakis, Christos T.

    2013-01-01

    Moderate vibrations continue to be recorded on the Øresund Bridge twin-stay cables. System identification techniques have been applied to investigate the aerodynamic characteristics of the cables based on ambient vibration measurements. As might be expected, the measured aerodynamic damping ratios...... vary from those estimated through use of aerodynamic coefficients of single circular cylinders, as reported in literature. To address this issue, wind tunnel tests were performed on a 1:2.3 scale section model of the Øresund Bridge cables, with and without the presence of helical fillets. In this paper...

  5. Aerodynamic Numerical Testing of Megawatt Wind Turbine Blade to Find Optimum Angle of Attack

    OpenAIRE

    Sogukpinar, H.; Bozkurt, I.; Pala, M; Turkmenler, H.

    2016-01-01

    Wind energy is one of the oldest kinds of energy source used by mankind and it is dating back to thousand years. At the beginning of twentieth century, multi blades wind turbines were improved and used for charging in USA. After oil crisis in in the seventies, there was a surge of alternative energy sources in USA, Denmark and Germany. In terms of installed capacity, Germany had the leadership until 2007, then it passed to USA and finally China becomes the leader. Today, 6 MW capacity wind tu...

  6. Fundamentals and Methods of High Angle-of-Attack Flying Qualities Research

    Science.gov (United States)

    1988-01-01

    Solving Equation (6) for the spin Radius, R, and substituting into equation (13), ay can be redefined in terms of fib 𔃼V as given by equation (17). (T...14) through (16) respectively) are functions of flb/2V, o, and a. Thus there are three equations to solve for three unknowns ( fib /2V, 1, a) in order...January 17,1983, pp. 57-62. 86. Markman, Steven R., "Capabilities of Airborne and Ground Based Flight Simulation," AIAA Paper 85-1944. 87. Knotts

  7. Aerodynamic Characteristics of a 10 deg Sharp Cone at Hypersonic Speeds and High Angles of Attack

    Science.gov (United States)

    1975-06-01

    pump arrived at by trial and error. After an ex- and hypodermic needle , served as a self-seal- tensive pretrial period during which several :., Ing...lift and drag coefficients showed good agree- ment with the modified Ncwtonian theory . The ceneli P istributonwsnal the~ ~ ’nelný~(ontiasnuedrl...acceleration, ft/sec Newtonian theory . The centerline K Model geometry and m~iss function distribution was nearly independent of the L Model length, in

  8. A Simulator Study of the Effectiveness of a Pilot's Indicator which Combined Angle of Attack and Rate of Change of Total Pressure as Applied to the Take-Off Rotation and Climbout of a Supersonic Transport

    Science.gov (United States)

    Hall, Albert W.; Harris, Jack E.

    1961-01-01

    A simulator study has been made to determine the effectiveness of a single instrument presentation as an aid to the pilot in controlling both rotation and climbout path in take-off. The instrument was basically an angle-of-attack indicator, biased with a total-pressure-rate input as a means of suppressing the phugoid oscillation. Linearized six-degree-of-freedom equations of motion were utilized in simulating a hypothetical supersonic transport as the test vehicle. Each of several experienced pilots performed a number of simulated take-offs, using conventional flight instruments and either an angle-of-attack instrument or the combined angle-of-attack and total-pressure-rate instrument. The pilots were able to rotate the airplane, with satisfactory precision, to the 15 deg. angle of attack required for lift-off when using either an angle-of-attack instrument or the instrument which combined total-pressure-rate with angle of attack. At least 4 to 6 second-S appeared to be required for rotation to prevent overshoot, particularly with the latter instrument. The flight paths resulting from take-offs with simulated engine failures were relatively smooth and repeatable within a reasonably narrow band when the combined angle-of-attack and total-pressure-rate instrument presentation was used. Some of the flight paths resulting from take-offs with the same engine-failure conditions were very oscillatory when conventional instruments and an angle-of-attack instrument were used. The pilots considered the combined angle-of-attack and total- pressure-rate instrument a very effective aid. Even though they could, with sufficient practice, perform satisfactory climbouts after simulated engine failure by monitoring the conventional instruments and making correction based on their readings, it was much easier to maintain a smooth flight path with the single combined angle-of-attack and total-pressure-rate instrument.

  9. Drag prediction for blades at high angle of attack using CFD

    DEFF Research Database (Denmark)

    Sørensen, Niels N.; Michelsen, J.A.

    2004-01-01

    In the present paper it is first demonstrated that state of the art 3D CFD codes are. capable of predicting the correct dependency of the integrated drag of a flat plate placed perpendicular to the flow. This is in strong contrast to previous 2D investigations of infinite plates, where computations...

  10. Navy and the HARV: High angle of attack tactical utility issues

    Science.gov (United States)

    Sternberg, Charles A.; Traven, Ricardo; Lackey, James B.

    1994-01-01

    This presentation will highlight results from the latest Navy evaluation of the HARV (March 1994) and focus primarily on the impressions from a piloting standpoint of the tactical utility of thrust vectoring. Issue to be addressed will be mission suitability of high AOA flight, visual and motion feedback cues associated with operating at high AOA, and the adaptability of a pilot to effectively use the increased control power provided by the thrust vectoring system.

  11. Surface Pressure Estimates for Pitching Aircraft Model at High Angles-of-attack (Short Communication)

    OpenAIRE

    A.A. Pashilkar

    2002-01-01

    The surface pressure on a pitching delta wing aircraft is estimated from the normal force and the pitching moment characteristics. The pressure model is based on parametrising the surface pressure distribution on a simple delta wing. This model is useful as a first approximation of the load distribution on the aircraft wing. Leeward surface pressure distributions computed by this method are presented.

  12. Surface Pressure Estimates for Pitching Aircraft Model at High Angles-of-attack (Short Communication

    Directory of Open Access Journals (Sweden)

    A. A. Pashilkar

    2002-10-01

    Full Text Available The surface pressure on a pitching delta wing aircraft is estimated from the normal force and the pitching moment characteristics. The pressure model is based on parametrising the surface pressure distribution on a simple delta wing. This model is useful as a first approximation of the load distribution on the aircraft wing. Leeward surface pressure distributions computed by this method are presented.

  13. Influences of attack angle and mach number on aerodynamic characters of typical sections of extra-long blade in a steam turbine

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    On super-sonic or trans-sonic planar cascade wind tunnel of free jet intermittent type, wind blowing experiments were performed on the typical sections of stator and rotor blades in the last stage of ultra-ultra-critical steam turbine with extra-long blade of 1200mm. The influences of attack angle and Mach number on the aerodynamic performances of these sections of the blade profiles were verified, and their operating ranges were also specified.

  14. Computer programs for the calculation of dual sting pitch and roll angles required for an articulated sting to obtain angles of attack and sideslip on wind-tunnel models

    Science.gov (United States)

    Peterson, John B., Jr.

    1991-01-01

    Two programs were developed to calculate the pitch and roll position of the conventional sting drive and the pitch of a high angle articulated sting to position a wind tunnel model at the desired angle of attack and sideslip and position the model as near as possible to the centerline of the tunnel. These programs account for the effects of sting offset angles, sting bending angles, and wind-tunnel stream flow angles. In addition, the second program incorporates inputs form on-board accelerometers that measure model pitch and roll with respect to gravity. The programs are presented and a description of the numerical operation of the programs with a definition of the variables used in the programs is given.

  15. BiGlobal linear stability analysis on low-Re flow past an airfoil at high angle of attack

    KAUST Repository

    Zhang, Wei

    2016-04-04

    We perform BiGlobal linear stability analysis on flow past a NACA0012 airfoil at 16° angle of attack and Reynolds number ranging from 400 to 1000. The steady-state two-dimensional base flows are computed using a well-tested finite difference code in combination with the selective frequency damping method. The base flow is characterized by two asymmetric recirculation bubbles downstream of the airfoil whose streamwise extent and the maximum reverse flow velocity increase with the Reynolds number. The stability analysis of the flow past the airfoil is carried out under very small spanwise wavenumber β = 10−4 to approximate the two-dimensional perturbation, and medium and large spanwise wavenumbers (β = 1–8) to account for the three-dimensional perturbation. Numerical results reveal that under small spanwise wavenumber, there are at most two oscillatory unstable modes corresponding to the near wake and far wake instabilities; the growth rate and frequency of the perturbation agree well with the two-dimensional direct numerical simulation results under all Reynolds numbers. For a larger spanwise wavenumber β = 1, there is only one oscillatory unstable mode associated with the wake instability at Re = 400 and 600, while at Re = 800 and 1000 there are two oscillatory unstable modes for the near wake and far wake instabilities, and one stationary unstable mode for the monotonically growing perturbation within the recirculation bubble via the centrifugal instability mechanism. All the unstable modes are weakened or even suppressed as the spanwise wavenumber further increases, among which the stationary mode persists until β = 4.

  16. Experimental investigation of effect of flow attack angle on thermohydraulic performance of air flow in a rectangular channel with discrete V-pattern baffle on the heated plate

    Directory of Open Access Journals (Sweden)

    Raj Kumar

    2016-05-01

    Full Text Available In this work, the effect of angle of attack ( α a of the discrete V-pattern baffle on thermohydraulic performance of rectangular channel has been studied experimentally. The baffle wall was constantly heated and the other three walls of the channel were kept insulated. The experimentations were conducted to collect the data on Nusselt number ( N u b and friction factor ( f b by varying the Reynolds number (Re = 3000–21,000 and angle of attack ( α a from 30° to 70°, for the kept values of relative baffle height ( H b / H = 0 . 50 , relative pitch ratio ( P b / H = 1 . 0 , relative discrete width ( g w / H b = 1 . 5 and relative discrete distance ( D d / L v = 0 . 67 . As compared to the smooth wall, the V-pattern baffle roughened channel enhances the Nusselt number ( N u b and friction factor ( f b by 4.2 and 5.9 times, respectively. The present discrete V-pattern baffle shapes with angle of attack ( α a of 60° equivalent to flow Reynolds number of 3000 yields the greatest thermohydraulic performance. Discrete V-pattern baffle has improved thermal performance as compared to other baffle shapes’ rectangular channel.

  17. Flight-Determined Subsonic Longitudinal Stability and Control Derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) with Thrust Vectoring

    Science.gov (United States)

    Iliff, Kenneth W.; Wang, Kon-Sheng Charles

    1997-01-01

    The subsonic longitudinal stability and control derivatives of the F-18 High Angle of Attack Research Vehicle (HARV) are extracted from dynamic flight data using a maximum likelihood parameter identification technique. The technique uses the linearized aircraft equations of motion in their continuous/discrete form and accounts for state and measurement noise as well as thrust-vectoring effects. State noise is used to model the uncommanded forcing function caused by unsteady aerodynamics over the aircraft, particularly at high angles of attack. Thrust vectoring was implemented using electrohydraulically-actuated nozzle postexit vanes and a specialized research flight control system. During maneuvers, a control system feature provided independent aerodynamic control surface inputs and independent thrust-vectoring vane inputs, thereby eliminating correlations between the aircraft states and controls. Substantial variations in control excitation and dynamic response were exhibited for maneuvers conducted at different angles of attack. Opposing vane interactions caused most thrust-vectoring inputs to experience some exhaust plume interference and thus reduced effectiveness. The estimated stability and control derivatives are plotted, and a discussion relates them to predicted values and maneuver quality.

  18. Transition prediction of a hypersonic boundary layer over a cone at small angle of attack--with the improvement of eN method

    Institute of Scientific and Technical Information of China (English)

    SU CaiHong; ZHOU Heng

    2009-01-01

    The problem of transition prediction for hypersonic boundary layers over a sharp cone has been stud-ied in this work. The Mach number of the oncoming flow is 6, the cone half-angle is 5Ω, and the angle of attack is 1Ω. The conventional eN method is used, but the transition location so obtained is obviously incorrect. The reason is that in the conventional method, only the amplifying waves are taken into ac-count, while in fact, for different meridians the decay processes of the disturbances before they begin to grow are different. Based on our own previous work, new interpretation and essential improvement for the eN method are proposed. Not only the amplification process but also the decay process is con-sidered. The location, where by linear stability theory, the amplitude of disturbance wave is amplified from its initial small value to 1%, is considered to be the transition location. The new result for transi-tion prediction thus obtained is found to be fairly satisfactory. It is also indicated that for the calculation of base flow, boundary layer equations can be used for a small angle of attack. Its computational cost is much smaller than those for DNS.

  19. Ionospheric plasma flow over large high-voltage space platforms. I - Ion-plasma-time scale interactions of a plate at zero angle of attack. II - The formation and structure of plasma wake

    Science.gov (United States)

    Wang, J.; Hastings, D. E.

    1992-01-01

    The paper presents the theory and particle simulation results for the ionospheric plasma flow over a large high-voltage space platform at a zero angle of attack and at a large angle of attack. Emphasis is placed on the structures in the large, high-voltage regime and the transient plasma response on the ion-plasma time scale. Special consideration is given to the transient formation of the space-charge wake and its steady-state structure.

  20. Measurement of Aerodynamic Forces for Various Mean Angles of Attack on an Airfoil Oscillating in Pitch and on Two Finite-span Wings Oscillating in Bending with Emphasis on Damping in the Stall

    Science.gov (United States)

    Rainey, A Gerald

    1957-01-01

    The oscillating air forces on a two-dimensional wing oscillating in pitch about the midchord have been measured at various mean angles of attack and at Mach numbers of 0.35 and 0.7. The magnitudes of normal-force and pitching-moment coefficients were much higher at high angles of attack than at low angles of attack for some conditions. Large regions of negative damping in pitch were found, and it was shown that the effect of increasing the Mach number 0.35 to 0.7 was to decrease the initial angle of attack at which negative damping occurred. Measurements of the aerodynamic damping of a 10-percent-thick and of a 3-percent-thick finite-span wing oscillating in the first bending mode indicate no regions of negative damping for this type of motion over the range of variables covered. The damping measured at high angles of attack was generally larger than that at low angles of attack. (author)

  1. Bracing System of Large Attack Angle in Low Speed Wind Tunnel%低速风洞大攻角张线式支撑系统

    Institute of Scientific and Technical Information of China (English)

    杨恩霞; 刁彦飞; 庞永刚

    2001-01-01

    Based on traditional bracing system of wind tunnel testing, a system of hanging brace of large angle of attack was designed, which can reduce frame interference. The contradiction between bracing rigidity and aerodynamic interference can be resolved by this system.%基于传统的风洞试验支撑系统,设计了能减小支架干扰的大攻角张线式支撑系统。该系统能解决支架的支撑刚度与气动干扰之间的矛盾。

  2. Effect of aerodynamic and angle-of-attack uncertainties on the blended entry flight control system of the Space Shuttle from Mach 10 to 2.5

    Science.gov (United States)

    Stone, H. W.; Powell, R. W.

    1984-01-01

    A six-degree-of-freedom simulation analysis has been performed for the Space Shuttle Orbiter during entry from Mach 10 to 2.5 with realistic off-nominal conditions using the entry flight control system specified in May 1978. The off-nominal conditions included the following: (1) aerodynamic uncertainties, (2) an error in deriving the angle of attack from onboard instrumentation, (3) the failure of two of the four reaction control-system thrusters on each side, and (4) a lateral center-of-gravity offset. With combinations of the above off-nominal conditions, the control system performed satisfactorily with a few exceptions. The cases that did not exhibit satisfactory performance displayed the following main weaknesses. Marginal performance was exhibited at hypersonic speeds with a sensed angle-of-attack error of 4 deg. At supersonic speeds the system tended to be oscillatory, and the system diverged for several cases because of the inability to hold lateral trim. Several system modifications were suggested to help solve these problems and to maximize safety on the first flight: alter the elevon-trim and speed-brake schedules, delay switching to rudder trim until the rudder effectiveness is adequate, and reduce the overall rudder loop gain. These and other modifications were incorporated in a flight-control-system redesign in May 1979.

  3. A computer program for the calculation of the flow field including boundary layer effects for mixed-compression inlets at angle of attack

    Science.gov (United States)

    Vadyak, J.; Hoffman, J. D.

    1982-01-01

    A computer program was developed which is capable of calculating the flow field in the supersonic portion of a mixed compression aircraft inlet operating at angle of attack. The supersonic core flow is computed using a second-order three dimensional method-of-characteristics algorithm. The bow shock and the internal shock train are treated discretely using a three dimensional shock fitting procedure. The boundary layer flows are computed using a second-order implicit finite difference method. The shock wave-boundary layer interaction is computed using an integral formulation. The general structure of the computer program is discussed, and a brief description of each subroutine is given. All program input parameters are defined, and a brief discussion on interpretation of the output is provided. A number of sample cases, complete with data listings, are provided.

  4. An experimental investigation of thrust vectoring two-dimensional convergent-divergent nozzles installed in a twin-engine fighter model at high angles of attack

    Science.gov (United States)

    Capone, Francis J.; Mason, Mary L.; Leavitt, Laurence D.

    1990-01-01

    An investigation was conducted in the Langley 16-Foot Transonic Tunnel to determine thrust vectoring capability of subscale 2-D convergent-divergent exhaust nozzles installed on a twin engine general research fighter model. Pitch thrust vectoring was accomplished by downward rotation of nozzle upper and lower flaps. The effects of nozzle sidewall cutback were studied for both unvectored and pitch vectored nozzles. A single cutback sidewall was employed for yaw thrust vectoring. This investigation was conducted at Mach numbers ranging from 0 to 1.20 and at angles of attack from -2 to 35 deg. High pressure air was used to simulate jet exhaust and provide values of nozzle pressure ratio up to 9.

  5. AEROX: Computer program for transonic aircraft aerodynamics to high angles of attack. Volume 1: Aerodynamic methods and program users' guide

    Science.gov (United States)

    Axelson, J. A.

    1977-01-01

    The AEROX program estimates lift, induced-drag and pitching moments to high angles (typ. 60 deg) for wings and for wingbody combinations with or without an aft horizontal tail. Minimum drag coefficients are not estimated, but may be input for inclusion in the total aerodynamic parameters which are output in listed and plotted formats. The theory, users' guide, test cases, and program listing are presented.

  6. Wind-tunnel force and flow visualization data at Mach numbers from 1.6 to 4.63 for a series of bodies of revolution at angles of attack from minus 4 deg to 60 deg

    Science.gov (United States)

    Landrum, E. J.; Babb, C. D.

    1979-01-01

    Flow visualization and force data for a series of six bodies of revolution are presented without analysis. The data were obtained in the Langley Unitary Plan wind tunnel for angles of attack from -4 deg to 60 deg. The Reynolds number used for these tests was 6,600,000 per meter.

  7. Experimental Evaluation of the Effect of Angle-of-attack on the External Aerodynamics and Mass Capture of a Symmetric Three-engine Air-breathing Launch Vehicle Configuration at Supersonic Speeds

    Science.gov (United States)

    Kim, Hyun D.; Frate, Franco C.

    2001-01-01

    A subscale aerodynamic model of the GTX air-breathing launch vehicle was tested at NASA Glenn Research Center's 10- by 10-Foot Supersonic Wind Tunnel from Mach 2.0 to 3.5 at various angles-of-attack. The objective of the test was to investigate the effect of angle-of-attack on inlet mass capture, inlet diverter effectiveness, and the flowfield at the cowl lip plane. The flow-through inlets were tested with and without boundary-layer diverters. Quantitative measurements such as inlet mass flow rates and pitot-pressure distributions in the cowl lip plane are presented. At a 3deg angle-of-attack, the flow rates for the top and side inlets were within 8 percent of the zero angle-of-attack value, and little distortion was evident at the cowl lip plane. Surface oil flow patterns showing the shock/boundary-layer interaction caused by the inlet spikes are shown. In addition to inlet data, vehicle forebody static pressure distributions, boundary-layer profiles, and temperature-sensitive paint images to evaluate the boundary-layer transition are presented. Three-dimensional parabolized Navier-Stokes computational fluid dynamics calculations of the forebody flowfield are presented and show good agreement with the experimental static pressure distributions and boundary-layer profiles. With the boundary-layer diverters installed, no adverse aerodynamic phenomena were found that would prevent the inlets from operating at the required angles-of-attack. We recommend that phase 2 of the test program be initiated, where inlet contraction ratio and diverter geometry variations will be tested.

  8. A computer program for calculating the perfect gas inviscid flow field about blunt axisymmetric bodies at an angle of attack of 0 deg

    Science.gov (United States)

    Zoby, E. V.; Graves, R. A., Jr.

    1973-01-01

    A method for the rapid calculation of the inviscid shock layer about blunt axisymmetric bodies at an angle of attack of 0 deg has been developed. The procedure is of an inverse nature, that is, a shock wave is assumed and calculations proceed along rays normal to the shock. The solution is iterated until the given body is computed. The flow field solution procedure is programed at the Langley Research Center for the Control Data 6600 computer. The geometries specified in the program are sphores, ellipsoids, paraboloids, and hyperboloids which may conical afterbodies. The normal momentum equation is replaced with an approximate algebraic expression. This simplification significantly reduces machine computation time. Comparisons of the present results with shock shapes and surface pressure distributions obtained by the more exact methods indicate that the program provides reasonably accurate results for smooth bodies in axisymmetric flow. However, further research is required to establish the proper approximate form of the normal momentum equation for the two-dimensional case.

  9. Effects of Low Incoming Turbulence on the Flow around a 5 : 1 Rectangular Cylinder at Non-Null-Attack Angle

    Directory of Open Access Journals (Sweden)

    M. Ricci

    2016-01-01

    Full Text Available The incompressible high Reynolds number flow around the rectangular cylinder with aspect ratio 5 : 1 has been extensively studied in the recent literature and became a standard benchmark in the field of bluff bodies aerodynamics. The majority of the proposed contributions focus on the simulation of the flow when a smooth inlet condition is adopted. Nevertheless, even when nominally smooth conditions are reproduced in wind tunnel tests, a low turbulence intensity is present together with environmental disturbances and model imperfections. Additionally, many turbulence models are known to be excessively dissipative in laminar-to-turbulent transition zones, generally leading to overestimation of the reattachment length. In this paper, Large Eddy Simulations are performed on a 5 : 1 rectangular cylinder at non-null-attack angle aiming at studying the sensitivity of such flow to a low level of incoming disturbances and compare the performance of standard Smagorinsky-Lilly and Kinetic Energy Transport turbulence models.

  10. Analysis of the longitudinal handling qualities and pilot-induced-oscillation tendencies of the High-Angle-of-Attack Research Vehicle (HARV)

    Science.gov (United States)

    Hess, Ronald A.

    1994-01-01

    The NASA High-Angle-of Attack Research Vehicle (HARV), a modified F-18 aircraft, experienced handling qualities problems in recent flight tests at NASA Dryden Research Center. Foremost in these problems was the tendency of the pilot-aircraft system to exhibit a potentially dangerous phenomenon known as a pilot-induced oscillation (PIO). When they occur, PIO's can severely restrict performance, sharply dimish mission capabilities, and can even result in aircraft loss. A pilot/vehicle analysis was undertaken with the goal of reducing these PIO tendencies and improving the overall vehicle handling qualities with as few changes as possible to the existing feedback/feedforward flight control laws. Utilizing a pair of analytical pilot models developed by the author, a pilot/vehicle analysis of the existing longitudinal flight control system was undertaken. The analysis included prediction of overall handling qualities levels and PIO susceptability. The analysis indicated that improvement in the flight control system was warranted and led to the formulation of a simple control stick command shaping filter. Analysis of the pilot/vehicle system with the shaping filter indicated significant improvements in handling qualities and PIO tendencies could be achieved. A non-real time simulation of the modified control system was undertaken with a realistic, nonlinear model of the current HARV. Special emphasis was placed upon those details of the command filter implementation which could effect safety of flight. The modified system is currently awaiting evaluation in the real-time, pilot-in-the-loop, Dual-Maneuvering-Simulator (DMS) facility at Langley.

  11. High Angle of Attack Aerodynamics

    Science.gov (United States)

    1979-01-01

    pas pressuris~o ,le domains du nombn3 do Reynolds couvert par variation do la viteese (40 m/s 4 V 4 oVs) oat relative- mont modesto 0,8 x 106 pc,4e...equationa which apply are: - on the wing : equ. (2a) - on the vortex sheet and sear wake equ Is (2b), (3), (A-4) - on the vortex : equ. (6) The

  12. Three-Dimensional Inviscid Flow About Supersonic Blunt Cones at Angle of Attack - III: Coupled Subsonic and Supersonic Programs for Inviscid Three-Dimensional Flow

    Energy Technology Data Exchange (ETDEWEB)

    Abbett, M. J.; Fort, R.

    1968-09-01

    The three-dimensional ideal gas flow in the shock layer of a blunted supersonic cone at an angle of attack is calculated using two asymptotic solutions. The first solution calculates the steady state flow in the subsonic nose region by obtaining a time-dependent solution of the hyperbolic equations using numerical techniques. Internal, nonboundary points are calculated using a Lax-Wendroff numerical type technique. Boundary points, shock and body surface, are computed using a time-dependent method of characteristics. When a steady state solution is reached the flow properties on a surface of constant {theta}, (where the Mach number is everywhere > 1) are used for initial data for the afterbody solution. The afterbody solution, using polar coordinates (r, {theta}, {phi}) assumes at r{sub 0} an arbitrary set of initial conditions provided by the nose region solution and computes the downstream flow as a function of {theta}, {phi}, and r until an asymptotic state independent of r develops. The interior mesh points are again calculated using a Lax- Wendroff type technique and the boundary points by a method of characteristics. This report covers the coupling of the time-dependent and radius (r) dependent solutions. Instructions are given for the operation of the resulting Fortran code. The type of input data required is detailed and sample output is provided. Output data is given in two sets of coordinates. One is wind orientated; the other set is given in body orientated coordinates; The analytical transformation from one coordinate system to the other is given.

  13. 不同攻角下压气机叶栅涡流噪声辐射特性的研究%Research on Vortex Noise Radiation of Compressor Cascade Under Different Attack Angle

    Institute of Scientific and Technical Information of China (English)

    柳晓丹; 杨爱玲; 戴韧; 陈康民

    2011-01-01

    采用大涡模拟模型和边界元方法对压气机叶栅的非定常流场与声场进行了分析,研究了来流攻角对叶栅尾缘非定常涡脱落及其噪声辐射特性的影响.结果表明:压气机叶栅流场中存在着尾缘涡脱落现象,尾缘涡脱落的强度随着攻角的变化而变化.在较大的正攻角下,吸力面存在的分离涡与下游的尾涡相互影响,引起较大的升力脉动,使得噪声辐射增强;而在较大负攻角下,压力面的分离涡同样影响尾缘涡的脱落,噪声辐射水平也有增强趋势.来流攻角对噪声辐射的指向性影响不大.声压级的最小值出现在阻力系数最小的攻角下.%In order to investigate the influence of attack angle of compressor cascades on unsteady vortex shedding at trailing edge and the noise radiation,large eddy simulation model and boundary element method were used to analyze the unsteady flow and acoustic field.Results show that unsteady vortex shedding exists at the trailing edge of compressor cascade,and the shedding strength varies with attack angles.The vortex separation on suction side with large positive attack angle affects the downstream trailing vortex,which causes large lift fluctuation and strengthens the noise radiation;whereas the separation on pressure side with large negative attack angle also influences the trailing-edge vortex shedding and strengthens the noise radiation.However,the attack angle of coming flow has little impact on directivity of noise radiation.The minimum value of sound level appears at an attack angle of least drag.

  14. Circumscribed Ciliochoroidal Effusion Presenting as an Acute Angle Closure Attack

    Science.gov (United States)

    Lipa, Roslyn Kathryn Manrique; Sánchez, María Eugenia González; Ordovas, Carlos Antonio Hijar; Aragües, Abel Rojo; Borque, Carmen Garcia

    2017-01-01

    Purpose: To report a case of choroidal effusion probably caused by angiotensin receptor II blocker. Case Report: A 52-year-old man with aplastic anemia and high blood pressure who developed unilateral acute angle closure glaucoma after receiving oral cyclosporine and angiotensin II receptor blocker (losartan). Ophthalmic examination revealed visual acuity of 20/30 in the left eye, mild mydriasis, iris bombe, no anterior chamber reaction, mild conjunctival hyperemia, and the intraocular pressure of 30 mmHg. After laser YAG iridotomy, funduscopy was performed showing a choroidal circumscribed lesion at the inferotemporal quadrant. Diagnostic tests ruled out any inflammatory or malignancy process, and the choroidal lesion spontaneously disappeared. After 20 months of follow-up, patient's ocular remained stable. Conclusion: This is the third case of choroidal effusion associated with angiotensin II receptor blockers. Since idiosyncratic ciliochoroidal effusion is a diagnosis of exclusion, it is mandatory to rule out more frequent causes, such as inflammatory or malignant processes. PMID:28299016

  15. Numerical Calcultion on Hydrodynamic Characteristic of UUV with Cabin Door Opened at Small Angle of Attack%舱门开启状态下UUV小攻角水动力特性数值模拟

    Institute of Scientific and Technical Information of China (English)

    刘立栋; 张宇文

    2012-01-01

    In order to master hydrodynamic characteristic of UUV whose cabin door is opened at small angle of attack,based on wind tunnel model experiment firstly, it is proved that numerical computation method used is accurate and effective;then the drag,lift and moment characteristic of UUV whose cabin door is opened are calculated numerically by this method,and the influence of load cabin and cabin door on the surface pressure distribution of UUV is analysed after cabin door is opened. The computation result shows that the high pressure difference between the front end and the back end of the load cabin results in a significant increase of the pressare drag of load cabin dragin UUV's, and the drag about zero angle of attack are not symmetrical,the main reason of which is that the pressure drag of load cabin increases with the increase of absolute value of angle of attack on the condition of negative angle of attack. Because of fluid block function of the average pressure on the canbin door's down surface is higher that the up one when the angle of attack is zero degree,so zero lift of UUV is positive,and zero lift angle of attack is about -3 degrees,besides zero moment is positive. Zero moment angle of attack is about -1 degrees.%为了掌握舱门开启状态下UUV小攻角水动力特性,首先基于风洞模型实验验证了所用数值计算方法的准确性与有效性,进而采用该方法对舱门开启状态UUV阻力、升力及力矩特性进行了数值模拟研究,分析了舱门开启后载荷舱及舱门对UUV表面压力分布的影响.计算结果表明,载荷舱前后端面形成的较大压力差,导致舱门开启状态UUV阻力显著提升,且阻力关于零攻角表现为不对称性,主要原因在于负攻角条件下载荷舱粘压阻力随攻角绝对值的增大而增大;由于载荷舱的流体阻滞作用,零攻角工况下舱门下表面平均压力高于上表面,UUV零攻角升力为正,零升力攻角约为-3.,

  16. Virtual Test for the Effect of Rear Wing Attack Angle on the Performance of Formula SAE Car%尾翼攻角变化对方程式赛车性能影响的虚拟试验

    Institute of Scientific and Technical Information of China (English)

    倪俊; 吴志成; 陈思忠

    2012-01-01

    In order to compare the performance of Formula SAE car with different rear wing attack angles, the virtual prototype model of a certain Formula SAE car was built by ADAMS with considering the nonlinear factors and aerodynamics characteristics. By comparison with actual test data, the correctness of the virtual prototype model was verified. Based on these, a feasible method was proposed which can take the aerodynamics characteristics of the rear wing into simulation. The comparison among different rear wing attack angles was performed according to the lift and drag characteristics of the rear wing. The results show that the increase of the attack angle has a little effect on acceleration performance. Besides, the transient performance and the crosswind stability are improved with the increase of attack angle, but the tendency to understeer is aggravated.%为对比方程式赛车尾翼攻角不同时的性能.应用ADAMS建立了某方程式赛车的虚拟样机模型,并考虑了非线性因素及空气动力特性.通过与实车试验结果的对比,验证了虚拟样机模型的准确性.在此基础上,提出了一种切实可行的方法在仿真中计入了尾翼的空气动力特性.并根据不同攻角时的尾翼升阻特性,对尾翼攻角不同时的各项性能进行了对比.对比结果表明,攻角的增大对赛车的直线加速性能影响很小,提高了赛车的瞬态响应性能和侧风稳定性,但加重了赛车的不足转向特性.

  17. Structural Learning of Attack Vectors for Generating Mutated XSS Attacks

    Directory of Open Access Journals (Sweden)

    Yi-Hsun Wang

    2010-09-01

    Full Text Available Web applications suffer from cross-site scripting (XSS attacks that resulting from incomplete or incorrect input sanitization. Learning the structure of attack vectors could enrich the variety of manifestations in generated XSS attacks. In this study, we focus on generating more threatening XSS attacks for the state-of-the-art detection approaches that can find potential XSS vulnerabilities in Web applications, and propose a mechanism for structural learning of attack vectors with the aim of generating mutated XSS attacks in a fully automatic way. Mutated XSS attack generation depends on the analysis of attack vectors and the structural learning mechanism. For the kernel of the learning mechanism, we use a Hidden Markov model (HMM as the structure of the attack vector model to capture the implicit manner of the attack vector, and this manner is benefited from the syntax meanings that are labeled by the proposed tokenizing mechanism. Bayes theorem is used to determine the number of hidden states in the model for generalizing the structure model. The paper has the contributions as following: (1 automatically learn the structure of attack vectors from practical data analysis to modeling a structure model of attack vectors, (2 mimic the manners and the elements of attack vectors to extend the ability of testing tool for identifying XSS vulnerabilities, (3 be helpful to verify the flaws of blacklist sanitization procedures of Web applications. We evaluated the proposed mechanism by Burp Intruder with a dataset collected from public XSS archives. The results show that mutated XSS attack generation can identify potential vulnerabilities.

  18. Structural Learning of Attack Vectors for Generating Mutated XSS Attacks

    CERN Document Server

    Wang, Yi-Hsun; Lee, Hahn-Ming; 10.4204/EPTCS.35.2

    2010-01-01

    Web applications suffer from cross-site scripting (XSS) attacks that resulting from incomplete or incorrect input sanitization. Learning the structure of attack vectors could enrich the variety of manifestations in generated XSS attacks. In this study, we focus on generating more threatening XSS attacks for the state-of-the-art detection approaches that can find potential XSS vulnerabilities in Web applications, and propose a mechanism for structural learning of attack vectors with the aim of generating mutated XSS attacks in a fully automatic way. Mutated XSS attack generation depends on the analysis of attack vectors and the structural learning mechanism. For the kernel of the learning mechanism, we use a Hidden Markov model (HMM) as the structure of the attack vector model to capture the implicit manner of the attack vector, and this manner is benefited from the syntax meanings that are labeled by the proposed tokenizing mechanism. Bayes theorem is used to determine the number of hidden states in the model...

  19. The Timing of Terrorist Attacks

    DEFF Research Database (Denmark)

    Jensen, Thomas

    2016-01-01

    I use a simple optimal stopping model to derive policy relevant insights on the timing of one-shot attacks by small autonomous terrorist units or “lone wolf” individuals. A main insight is that an increase in proactive counterterrorism measures can lead to a short term increase in the number...... of attempted terrorist attacks because it makes it more risky for existing terrorist units to pursue further development of capabilities. This is consistent with the events in London in 2005 where a terrorist attack on 7 July was followed by a similar but unsuccessful attack two weeks later....

  20. 小迎角纵向不稳定飞机起飞安全性分析%Take-off safety analysis of aircraft with longitudinal static instability at low angles of attack

    Institute of Scientific and Technical Information of China (English)

    耿建中; 姚海林; 段卓毅

    2013-01-01

    由于螺旋桨滑流的影响,某运输机起飞构型在小迎角时纵向稳定性裕度不足,甚至不稳定,给飞机带来安全隐患.分析了某运输机起飞构型纵向力矩特性,讨论了螺旋桨滑流对纵向静稳定性的影响、影响飞机起飞时的安全因素和进入小迎角飞行的条件,建立了飞机起飞的数学仿真模型,通过大量的仿真计算,研究了突风和驾驶员误操纵对飞机起飞安全性的影响,给出了起飞时飞机所能抗御的最大突风速度.研究结果表明,某运输机小迎角稳定裕度不足,不稳定对飞机安全起飞的影响可以不予考虑.%The propeller slipstream result in longitudinal stability margin insufficient,even static instability at low angles of attack of an aircraft,which may cause potential problem. In order to study the effect of the static instability on take-off safety,the effect of propeller slipstream on longitudinal static stability was discussed. The pitching moment characteristic,the factor which has effect on safe take-off,and the con-ditons which may cause an aircraft flying at low angles attack were analyzed. Building dynamic model,the influence of gust and the pilot misoperation on the take-off safety were studied through computation and simulation. The maximum velocity of gust that an aircraft can resist was given. The result indicates the effect of the static instability on the take-off safety can be neglected.

  1. Local heat transfer around a wall-mounted cube. Case of the attack angle of 45 deg.; Rippotai tokki mawari no kyokusho netsu dentatsu. Katamukikaku 45 degrees no baai

    Energy Technology Data Exchange (ETDEWEB)

    Nakamura, H.; Igarashi, T.; Tsutsui, T. [National Defense Academy, Kanagawa (Japan)

    1999-11-25

    An experimental study was performed to investigate the local heat transfer around a cube mounted on the wall. The cube lied in the turbulent boundary layer. The flow angle of attack to the cube was 15 degree. The Reynolds number ranged from 4.2 x 10{sup 3} to 3.3 x 10{sup 4}. The surface temperature distributions around time cube were measured with thermocouples tinder the condition of a constant heat flux. The local h eat transfer is very high near the front corner on the top face of the cube. This high heat transfer region extends from the front corner to downstream along both edges. This is caused by the formation of lamb horn vortex. The local heat transfer is also high in time region of horseshoe vortex formed a round the cube. On the wall behind the cube, there is a pair of minimum heat transfer region. The average Nusselt number on each face of the cube is given as a function of Reynolds number. The overall Nusselt number of time cube is expressed by Nu{sub m}=0.43Re{sup 0.58}. (author)

  2. 不同攻角下AUV回收过程中的水动力规律%Research on the Law of the Hydrodynamic During AUV Recovery under Different Angle of Attack

    Institute of Scientific and Technical Information of China (English)

    潘光; 王培; 杜晓旭

    2012-01-01

    通过对AUV(Autonomous Underwater Vehicle)回收过程中运动规律的研究和对纳维—斯托克斯方程(Navier-Stokes equations)及其求解方法的分析,基于CFD(Computational Fluid Dynamics)理论建立了AUV回收运动的三维计算模型,并使用CFD软件完成其物理模型的建立、网格的划分及求解设置.在此基础上对AUV回收过程中的阻力、升力干扰进行分析计算,得到不同攻角下AUV所受到的水动力干扰与AUV和回收平台之间距离的相互联系.%By studying the law of motion of AUV recovery process and analyzing Navier-Stokes equations (Navier-Stokes equations) and its solution.the three-dimensional model of the AUV recovery movement is established based on CFD Theory,and then CFD software is used to finish the build of the physical model,the partition of the mesh and solution set. On this basis, drag and lift interference have been calculated in the process of the AUV recovery. The relationship between AUV hydrodynamic interference suffered by different angle of attack and the distance between recovery platform and AUV is obtained.

  3. Some Aspects of the Modified Newtonian and Prandtl-Meyer-Expansion Method for Axisymmetric Blunt Bodies at Zero Angle of Attack

    Science.gov (United States)

    Wagner, Richard D., Jr.

    1959-01-01

    In a recent article on hypersonic flow, Lees and Kubota suggested a modification of the local-expansion method to predict the surface pressures in the region of a nose-cylinder junction where Newtonian theory fails. The modification consists of matching the Newtonian pressure distribution and the Prandtl-Meyer relation at the point on the nose surface where both the pressure and the pressure gradient, predicted by these two solution, are equal. With this approximation, the pressure distribution can be predicted quite accurately up to the nose-cylinder junction for blunt-nosed bodies of continuous curvature, provided centrifugal-force effects are negligible. The purpose of this note is to facilitate the application of Lees' suggestion and to draw attention to some of its consequences.

  4. The PELskin project-part V: towards the control of the flow around aerofoils at high angle of attack using a self-activated deployable flap

    OpenAIRE

    2016-01-01

    During the flight of birds, it is often possible to notice that some of the primaries and covert feathers on the upper side of the wing pop-up under critical flight conditions, such as the landing approach or when stalking their prey (see Fig. 1) . It is often conjectured that the feathers pop up plays an aerodynamic role by limiting the spread of flow separation . A combined experimental and numerical study was conducted to shed some light on the physical mechanism determining the feathers s...

  5. Analytical Characterization of Internet Security Attacks

    Science.gov (United States)

    Sellke, Sarah H.

    2010-01-01

    Internet security attacks have drawn significant attention due to their enormously adverse impact. These attacks includes Malware (Viruses, Worms, Trojan Horse), Denial of Service, Packet Sniffer, and Password Attacks. There is an increasing need to provide adequate defense mechanisms against these attacks. My thesis proposal deals with analytical…

  6. Automated Generation of Attack Trees

    DEFF Research Database (Denmark)

    Vigo, Roberto; Nielson, Flemming; Nielson, Hanne Riis

    2014-01-01

    Attack trees are widely used to represent threat scenarios in a succinct and intuitive manner, suitable for conveying security information to non-experts. The manual construction of such objects relies on the creativity and experience of specialists, and therefore it is error-prone and impractica......Attack trees are widely used to represent threat scenarios in a succinct and intuitive manner, suitable for conveying security information to non-experts. The manual construction of such objects relies on the creativity and experience of specialists, and therefore it is error...

  7. Three-Dimensional Inviscid Flow About Supersonic Blunt Cones at Angle of Attack - I: Numerical Technique for the Three-Dimensional Blunt-Body Problem

    Energy Technology Data Exchange (ETDEWEB)

    Moretti, G.; Bleich, G.

    1968-09-01

    The three-dimensional flow field around blunted bodies traveling at supersonic speed is computed using a time-dependent technique. The problem is mathematically well posed, the technique is stable and its accuracy increases with the fineness of the mesh. Values at points within the shock layer are computed by a method closely related to the Lax-Wendroff technique. Values at shock points and body points are computed by a four-dimensional method of characteristics.

  8. High Angle-of-Attack Aerodynamics

    Science.gov (United States)

    1982-12-01

    in 50th dIetIl vetr . , i spetruml oif Icyjiolts tiumieors. I’liese dtata show that over the AO .\\ ritntig ftstl airotxirlitul\\ 40. t,, 711 (le grees...Atarltv niec f4 i ieohrhn .tiesi rcinln atr sseelttl righ. is sown n Fgur 16b), onsstet wih te eteral fow hotkrap shwn n Fqurv14(). .it that

  9. Attack Vulnerability of Network Controllability.

    Science.gov (United States)

    Lu, Zhe-Ming; Li, Xin-Feng

    2016-01-01

    Controllability of complex networks has attracted much attention, and understanding the robustness of network controllability against potential attacks and failures is of practical significance. In this paper, we systematically investigate the attack vulnerability of network controllability for the canonical model networks as well as the real-world networks subject to attacks on nodes and edges. The attack strategies are selected based on degree and betweenness centralities calculated for either the initial network or the current network during the removal, among which random failure is as a comparison. It is found that the node-based strategies are often more harmful to the network controllability than the edge-based ones, and so are the recalculated strategies than their counterparts. The Barabási-Albert scale-free model, which has a highly biased structure, proves to be the most vulnerable of the tested model networks. In contrast, the Erdős-Rényi random model, which lacks structural bias, exhibits much better robustness to both node-based and edge-based attacks. We also survey the control robustness of 25 real-world networks, and the numerical results show that most real networks are control robust to random node failures, which has not been observed in the model networks. And the recalculated betweenness-based strategy is the most efficient way to harm the controllability of real-world networks. Besides, we find that the edge degree is not a good quantity to measure the importance of an edge in terms of network controllability.

  10. Performance of attack strategies on modular networks

    CERN Document Server

    da Cunha, Bruno Requião

    2016-01-01

    Vulnerabilities of complex networks have became a trend topic in complex systems recently due to its real world applications. Most real networks tend to be very fragile to high betweenness adaptive attacks. However, recent contributions have shown the importance of interconnected nodes in the integrity of networks and module-based attacks have appeared promising when compared to traditional malicious non-adaptive attacks. In the present work we deeply explore the trade-off associated with attack procedures, introducing a generalized robustness measure and presenting an attack performance index that takes into account both robustness of the network against the attack and the run-time needed to obtained the list of targeted nodes for the attack. Besides, we introduce the concept of deactivation point aimed to mark the point at which the network stops to function properly. We then show empirically that non-adaptive module-based attacks perform better than high degree and betweenness adaptive attacks in networks ...

  11. Perfection of Recent Attacks using IP

    Directory of Open Access Journals (Sweden)

    A. RENGARAJAN

    2012-02-01

    Full Text Available The Internet threat monitoring (ITM systems have been deployed to detect widespread attacks on the Internet in recent years. However, the effectiveness of ITM systems critically depends on the confidentiality of the location of their monitors. If adversaries learn the monitor locations of an ITM system, they can bypass the monitors and focus on the uncovered IP address space without being detected. In this paper, we study a new class of attacks, the invisible LOCalization (iLOC attack. The iLOC attack can accurately and invisibly localize monitors of ITM systems. In the iLOC attack, the attacker launches low-rate port-scan traffic, encoded with a selected pseudo noise code (PN-code, to targeted networks. While the secret PN-code is invisible to others, the attacker can accurately determine the existence of monitors in the targeted networks based on whether the PN-code is embedded in the report data queried from the data center of the ITM system. We formally analyze the impact of various parameters on attack effectiveness. We implement the iLOC attack and conduct the performance evaluation on a real-world ITM system to demonstrate the possibility of such attacks. We also conduct extensive simulations on the iLOC attack using real-world traces. Our data show that the iLOC attack can accurately identify monitors while being invisible to ITM systems. Finally, we present a set of guidelines to counteract the iLOC attack.

  12. Biomechanics of knife stab attacks.

    Science.gov (United States)

    Chadwick, E K; Nicol, A C; Lane, J V; Gray, T G

    1999-10-25

    Equipment, materials and methods for the measurement of the biomechanical parameters governing knife stab attacks have been developed and data have been presented that are relevant to the improvement of standards for the testing of stab-resistant materials. A six-camera Vicon motion analysis system was used to measure velocity, and derive energy and momentum during the approach phase of the attack and a specially developed force-measuring knife was used to measure three-dimensional forces and torque during the impact phase. The body segments associated with the knife were modelled as a series of rigid segments: trunk, upper arm, forearm and hand. The velocities of these segments, together with knowledge of the mass distribution from biomechanical tables, allowed the calculation of the individual segment energy and momentum values. The instrumented knife measured four components of load: axial force (along the length of the blade), cutting force (parallel to the breadth of the blade), lateral force (across the blade) and torque (twisting action) using foil strain gauges. Twenty volunteers were asked to stab a target with near maximal effort. Three styles of stab were used: a short thrust forward, a horizontal style sweep around the body and an overhand stab. These styles were chosen based on reported incidents, providing more realistic data than had previously existed. The 95th percentile values for axial force and energy were 1885 N and 69 J, respectively. The ability of current test methods to reproduce the mechanical parameters measured in human stab attacks has been assessed. It was found that current test methods could reproduce the range of energy and force values measured in the human stab attacks, although the simulation was not accurate in some respects. Non-axial force and torque values were also found to be significant in the human tests, but these are not reproduced in the standard mechanical tests.

  13. Stochastic Model of TCP SYN Attacks

    Directory of Open Access Journals (Sweden)

    Simona Ramanauskaitė

    2011-08-01

    Full Text Available A great proportion of essential services are moving into internet space making the threat of DoS attacks even more actual. To estimate the real risk of some kind of denial of service (DoS attack in real world is difficult, but mathematical and software models make this task easier. In this paper we overview the ways of implementing DoS attack models and offer a stochastic model of SYN flooding attack. It allows evaluating the potential threat of SYN flooding attacks, taking into account both the legitimate system flow as well as the possible attack power. At the same time we can assess the effect of such parameters as buffer capacity, open connection storage in the buffer or filte­ring efficiency on the success of different SYN flooding attacks. This model can be used for other type of memory depletion denial of service attacks.Article in Lithuanian

  14. Patterns of Heart Attacks

    Science.gov (United States)

    2010-06-01

    Hypertension (high blood pressure), smoking, family history of heart disease, and diabetes mellitus (both types 1 and 2) are also factors that increase the risk...breath 16% 19% Hyperlipidemia 2% Asthma 23% Coronary Artery Disease 15% Chest Pain 4% Pneumonia 24% 38% Diabetes 7% Congestive Heart Failure 9% 6...Pain Diabetes Congestive Heart Failure Hypertension Asthma Table 5.7: Diagnoses that distinguish cluster 8 from the cost bucket 2 population average. The

  15. On Mitigating Distributed Denial of Service Attacks

    Science.gov (United States)

    Gao, Zhiqiang

    2006-01-01

    Denial of service (DoS) attacks and distributed denial of service (DDoS) attacks are probably the most ferocious threats in the Internet, resulting in tremendous economic and social implications/impacts on our daily lives that are increasingly depending on the well-being of the Internet. How to mitigate these attacks effectively and efficiently…

  16. Detection of Denial-of-service Attacks

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Denial-of-service (DOS) is a type of computer attack, which can essentially disable computers and networks.Resource consumption type of DOS attack could not be detected by the traditional misuse detection technique. This paper presents a new method of support vector mchine (SVM) to detect these attacks. We find that a DOS attack to a host is related to the activities within an impact data set of the host. The SVM method is used to classify the subsets of an impact data set to estimate its anomalism. The experiment result shows that this method can detect resource consumption type of DOS attacks, such as SYNflood, Smurf and UDP-storm. A receiver operating characteristic curve is plotted to determine performance for any possible operating point of the DOS attacks detection.

  17. ACTIVITY ATTACK ON REDUCED VARIANTS OF RIJNDAEL

    Institute of Scientific and Technical Information of China (English)

    Wei Baodian; Liu Dongsu; Wang Xinmei

    2004-01-01

    The famous Square attacks against the Rijndael algorithm have taken advantage of the change of the balance of some bytes. Further study shows that the change of activity always happens before the change of balance, which builds the foundation for a new activity attack presented in this paper. In the activity attack, the round in which the activity changes is executed in an equivalent form to avoid the obstructive restriction of the subkeys of that round.The existence of the birthday paradox guarantees much fewer plaintexts necessary for activity attacks comparing with that for corresponding Square attacks. But no benefit may result from the new attacks performed independently because the activity attacks guess four instead of one key byte once. Only when both the balance property and the activity property are exploited at the same time can much better performance be obtained. The better performance in the simulation shows that the consuming time and chosen plaintexts necessary are both reduced to one tenth of those of the corresponding Square attacks. So the activity attacks could be viewed as an efficient supplement to the Square attacks.

  18. Evaluation of Hypervisor Stability towards Insider Attacks

    Institute of Scientific and Technical Information of China (English)

    Roman Kulikov; Svetlana Kolesnikova

    2016-01-01

    Virtualization technology plays a key role in cloud computing. Thus, the security issues of virtualization tools (hypervisors, emulators, etc.) should be under precise consideration. However, threats of insider attacks are underestimated. The virtualization tools and hypervisors have been poorly protected from this type of attacks. Furthermore, hypervisor is one of the most critical elements in cloud computing infrastructure. Firstly, hypervisor vulnerabilities analysis is provided. Secondly, a formal model of insider attack on hypervisor is developed. Consequently, on the basis of the formal attack model, we propose a new methodology of hypervisor stability evaluation. In this paper, certain security countermeasures are considered that should be integrated in hypervisor software architecture.

  19. Cavitating flow control through continuous tangential mass injection on a 2D hydrofoil at a small attack angle

    Directory of Open Access Journals (Sweden)

    Timoshevskiy Mikhail V.

    2016-01-01

    Full Text Available We studied cavitating flow over the suction side of a symmetric 2D foil – a scaled-down model of high-pressure hydroturbine guide vanes (GV – in different cavitation regimes at the attack angle of 3°. High-speed imaging was used to analyze spatial patterns and time dynamics of the gas-vapour cavities. A hydroacoustic pressure transducer was employed to register time-spectra of pressure fluctuations nearby the hydrofoil. A PIV technique was applied to measure the velocity fields and its fluctuations. The active flow control was implemented by means of a continuous liquid supply with different flow rates through a slot channel located in the GV surface. It was found that the active mass injection does not influence the primary flow upstream of the slot channel position. For the cavitation-free and cavitation inception cases, the injection was shown to make the turbulent wake past the GV section more intense. However, at the developed cavitation regimes the active flow management made it possible to reduce substantially the amplitude or even totally suppress the periodic cavity length oscillations and pressure pulsations associated with them.

  20. Experimental wake survey behind Viking 1975 entry vehicle at angles of attack of 0 deg and 5 deg, Mach numbers from 1.60 to 3.95, and longitudinal stations from 1.0 to 8.39 body diameters

    Science.gov (United States)

    Brown, C. A., Jr.; Campbell, J. F.; Tudor, D. H.

    1971-01-01

    An investigation was conducted to obtain flow properties in the wake of the Viking '75 entry vehicle at Mach numbers from 1.60 to 3.95 and at angles of attack of 0 deg and 5 deg. The wake flow properties were calculated from total and static pressures measured with a pressure rake at longitudinal stations varying from 1.0 to 8.39 body diameters and lateral stations varying from -0.42 to 3.0 body diameters. These measurements showed a a consistent trend throughout the range of Mach numbers and longitudinal distances and an increase in dynamic pressure with increasing downstream position.

  1. Anatomy parameters in attack eye of primary acute angle-closure glaucoma patients compared to that of contralateral eye%急性闭角型青光眼发作眼与对侧眼解剖参数的比较

    Institute of Scientific and Technical Information of China (English)

    王华; 梁远波; 唐炘; 范肃洁; 孙霞; 王涛; 孙兰萍; 王宁利

    2011-01-01

    Objective To campare the central corneal thickness (CCT) between the attack eye and contralateral eye in primary acute angle-closure glaucoma(AACG) patients. Methods About 75 primary acute angle-closure glaucoma patients was observed. We measured the CCT of the both eyes in primary acute angle-closure glaucoma by A scan. Also the ACD, thickness of lens and axis were measured when the IOP was reduced. And paired t test was used to compare the difference. Results The mean CCT of the attacked eye of AACG is (576.97 ±50.93) μm while the mean CCT of the contralateral eye is (544.68 ±33.53)(μm. There is significance in CCT between the attacked eye and the contralateral eye(P 0.05). Conclusions CCT was increased in acute angle-closure glaucoma after the attack compared to the contralateral eye which should be considered during the treatment of the AACG patients.%目的 对照研究急性闭角型青光眼发作眼和对侧眼的角膜中央厚度和前房深度,晶状体厚度和眼轴长度.方法 共观察了急性闭角型青光眼75例.眼压控制后每个患者双眼接受A超检查,检查项目包括角膜中央厚度、前房深度、晶状体厚度和眼轴长度.统计分析采用配对t检验.结果 急性闭角型青光眼发作眼的平均角膜中央厚度是(576.97±50.93)μm,对侧眼的平均角膜中央厚度为(544.68±33.53)μm(P0.05).结论 与对侧眼相比,急性闭角型青光眼的角膜中央厚度较厚,可能是发作后遗留的损害.其它眼解剖参数无统计学差异,因此对侧眼也应进行预防治疗.

  2. Evaluation of Crosstalk Attacks in Access Networks

    DEFF Research Database (Denmark)

    Wagner, Christoph; Eiselt, Michael; Grobe, Klaus

    2016-01-01

    WDM-PON systems regained interest as low-cost solution for metro and access networks. We present a comparative analysis of resilience of wavelength-selective and wavelength-routed architectures against crosstalk attackers. We compare the vulnerability of these architectures against attacks...

  3. Use of Attack Graphs in Security Systems

    Directory of Open Access Journals (Sweden)

    Vivek Shandilya

    2014-01-01

    Full Text Available Attack graphs have been used to model the vulnerabilities of the systems and their potential exploits. The successful exploits leading to the partial/total failure of the systems are subject of keen security interest. Considerable effort has been expended in exhaustive modeling, analyses, detection, and mitigation of attacks. One prominent methodology involves constructing attack graphs of the pertinent system for analysis and response strategies. This not only gives the simplified representation of the system, but also allows prioritizing the security properties whose violations are of greater concern, for both detection and repair. We present a survey and critical study of state-of-the-art technologies in attack graph generation and use in security system. Based on our research, we identify the potential, challenges, and direction of the current research in using attack graphs.

  4. Evaluating Deterioration of Concrete by Sulfate Attack

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Effects of factors such as water to cement ratio, fly ash and silica fume on the resistance of concrete to sulfate attack were investigated by dry-wet cycles and immersion method. The index of the resistance to sulfate attack was used to evaluate the deterioration degree of concrete damaged by sulfate. The relationship between the resistance of concrete to sulfate attack and its permeability/porosity were analyzed as well as its responding mechanism. Results show that the depth of sulfate crystal attack from surface to inner of concrete can be reduced by decreasing w/c and addition of combining fly ash with silica fume. The variation of relative elastic modulus ratio and relative flexural strength ratio of various specimens before and after being subjected to sulfate attack was compared.

  5. Minimization and Reliability Analyses of Attack Graphs

    Science.gov (United States)

    2002-02-01

    they model only attacks. Since we have a generic state machine model , we can simultaneously model not just attacks, but also seemingly benign system...Finite State Machine Model The Network We model the network as a set of facts, each represented as a relational predicate. The state of the network

  6. Spatially localized attacks on interdependent networks: the existence of a finite critical attack size

    CERN Document Server

    Berezin, Yehiel; Danziger, Michael M; Li, Daqing; Havlin, Shlomo

    2013-01-01

    Many real world complex systems such as infrastructure, communication and transportation networks are embedded in space, where entities of one system may depend on entities of other systems. These systems are subject to geographically localized failures due to malicious attacks or natural disasters. Here we study the resilience of a system composed of two interdependent spatially embedded networks to localized geographical attacks. We find that if an attack is larger than a finite (zero fraction of the system) critical size, it will spread through the entire system and lead to its complete collapse. If the attack is below the critical size, it will remain localized. In contrast, under random attack a finite fraction of the system needs to be removed to initiate system collapse. We present both numerical simulations and a theoretical approach to analyze and predict the effect of local attacks and the critical attack size. Our results demonstrate the high risk of local attacks on interdependent spatially embedd...

  7. Automatic Classification of Attacks on IP Telephony

    Directory of Open Access Journals (Sweden)

    Jakub Safarik

    2013-01-01

    Full Text Available This article proposes an algorithm for automatic analysis of attack data in IP telephony network with a neural network. Data for the analysis is gathered from variable monitoring application running in the network. These monitoring systems are a typical part of nowadays network. Information from them is usually used after attack. It is possible to use an automatic classification of IP telephony attacks for nearly real-time classification and counter attack or mitigation of potential attacks. The classification use proposed neural network, and the article covers design of a neural network and its practical implementation. It contains also methods for neural network learning and data gathering functions from honeypot application.

  8. SURVEY OF PACKET DROPPING ATTACK IN MANET

    Directory of Open Access Journals (Sweden)

    A.Janani

    2014-03-01

    Full Text Available Mobile Ad-hoc NETwork (MANET is an application of wireless network with self-configuring mobile nodes. MANET does not require any fixed infrastructure. Its development never has any threshold range. Nodes in MANET can communicate with each other if and only if all the nodes are in the same range. This wide distribution of nodes makes MANET vulnerable to various attacks, packet dropping attack or black hole attack is one of the possible attack. It is very hard to detect and prevent. To prevent from packet dropping attack, detection of misbehavior links and selfish nodes plays a vital role in MANETs. In this paper, a omprehensive investigation on detection of misbehavior links and malicious nodes is carried out.

  9. Experimental wake survey behind Viking 75 entry vehicle at angles of attack of 0 deg, 5 deg, and 10 deg, Mach numbers from 0.20 to 1.20, and longitudinal stations from 1.50 to 11.00 body diameters

    Science.gov (United States)

    Brown, C. A., Jr.; Campbell, J. F.

    1973-01-01

    An investigation was conducted to obtain flow properties in the wake of a preliminary configuration of the Viking '75 Entry Vehicle at Mach numbers from 0.20 to 1.20 and at angles of attack of 0 deg, 5 deg, and 10 deg. The wake flow properties were calculated from total and static pressures measured with a pressure rake at longitudinal stations varying from 1.50 to 11.00 body diameters, and are presented in tabulated and plotted form. The wake properties were essentially symmetrical about the X-axis at alpha = 0 deg and the profiles were shifted away from the X-axis at angles of attack. An unexpected reduction in wake property ratios occurred as the Mach number increased from 0.60 to 1.00; these ratios then increased as the Mach number increased to 1.20. The reduction was present for all the longitudinal stations of the tests and decreased with increased longitudinal distance.

  10. Forensics Investigation of Web Application Security Attacks

    Directory of Open Access Journals (Sweden)

    Amor Lazzez

    2015-02-01

    Full Text Available Nowadays, web applications are popular targets for security attackers. Using specific security mechanisms, we can prevent or detect a security attack on a web application, but we cannot find out the criminal who has carried out the security attack. Being unable to trace back an attack, encourages hackers to launch new attacks on the same system. Web application forensics aims to trace back and attribute a web application security attack to its originator. This may significantly reduce the security attacks targeting a web application every day, and hence improve its security. The aim of this paper is to carry out a detailed overview about the web application forensics. First, we define the web applications forensics, and we present a taxonomic structure of the digital forensics. Then, we present the methodology of a web application forensics investigation. After that, we illustrate the forensics supportive tools for a web application forensics investigation. After that, we present a detailed presentation of a set of the main considered web application forensics tools. Finally, we provide a comparison of the main considered web application forensics tools.

  11. An Intrusion Detection System Against UDP Flood Attack and Ping of Death Attack (DDOS in MANET

    Directory of Open Access Journals (Sweden)

    Ankur Ashok Acharya

    2016-04-01

    Full Text Available DDoS is one of the serious attacks in the ad hoc network. Among lot many DDoS attacks, UDP flood attack and Ping of death attack are considered to be important as these two attacks may cause severe damage to the network. To provide better security to the network, efficient intrusion detection (IDS system is required to monitor the network continuously, keeping track of malicious activities and policy violations and produce report to the network administrator. UDP flood attack and ping of death attack are given importance in this paper as they are not well addressed in the existing research works. Packet capture and packet decoder is used to identify the packets and retrieve the packet details. A threshold is set for each node that is connected to the network. If the packet flow into the node exceeds the threshold that is set then the administrator is notified about the same.

  12. What Are the Symptoms of a Heart Attack?

    Science.gov (United States)

    ... from the NHLBI on Twitter. What Are the Symptoms of a Heart Attack? Not all heart attacks ... symptoms are called silent heart attacks. Most Common Symptoms The most common warning symptoms of a heart ...

  13. AN APPROACH OF DEFENDING AGAINST DDOS ATTACK

    Institute of Scientific and Technical Information of China (English)

    Wu Zhijun; Duan Haixin; Li Xing

    2006-01-01

    An approach of defending against Distributed Denial of Service (DDoS) attack based on flow model and flow detection is presented. The proposed approach can protect targets from DDoS attacking, and allow targets to provide good service to legitimate traffic under DDoS attacking, with fast reaction. This approach adopts the technique of dynamic comb filter, yields a low level of false positives of less than 1.5%,drops similar percentage of good traffic, about 1%, and passes neglectable percentage of attack bandwidth to the victim, less than 1.5%. The prototype of commercial product, D-fighter, is developed by implementing this proposed approach on Intel network processor platform IXP 1200.

  14. The role of sleep in migraine attacks

    Directory of Open Access Journals (Sweden)

    Elaine Inamorato

    1993-11-01

    Full Text Available Migraine attacks may be precipitated by sleep deprivation or excessive sleep and sleep is also associated with relief of migraine attacks. In view of this variable relationship we studied the records of 159 consecutive outpatients of our Headache Unit. In 121 records there was reference to sleep involvement, in 55% by a single form and in 45% by more than one form. When only one form was related, relief was most common (70%. 30% of that group of patients had the migraine attack precipitated by sleep, 24% by deprivation and 6% by sleep excess. When the effects of sleep were multiple, these effects were as expected logically in 65%: «in accordance» group (e.g attack precipitated by sleep deprivation and relieved by sleep onset. In a second group, («conflicting» where the involvement was not logical, there were three different combinations of sleep involvement, possibly due to more than one pathophysiological mechanism.

  15. Prevention of Routing Attacks In Manet

    Directory of Open Access Journals (Sweden)

    N.Rajesh

    2013-01-01

    Full Text Available Mobile Ad hoc Networks (MANET are easily prone to attacks due to its network infrastructure. In previous routing attacks the malicious node is isolated using naive fuzzy response decisions. In this paper a new technology of broadcasting the awareness information about attacker node to all the existing nodes in the network is discussed. The awareness approach is based on an extended Dempster-Shafer mathematical theory(D-S Theory. Dempster-Shafer mathematical theory is used to collect the evidence notion of importance factors. The adaptiveness of the mechanism allows to systematically cope with the identified MANET routing attacks. The intrusion response action in MANET was addressed by isolating uncooperative nodes based on the node reputation derived from their behaviors. Here the effectiveness of the approach with the consideration of the packet delivery ratio and routing cost were demonstrated using java swing concepts

  16. Taxonomy of SSL/TLS Attacks

    Directory of Open Access Journals (Sweden)

    Keerthi Vasan K.

    2016-02-01

    Full Text Available Secure Socket Layer (SSL and Transport Layer Security (TLS protocols use cryptographic algorithms to secure data and ensure security goals such as Data Confidentiality and Integrity in networking. They are used along with other protocols such as HTTP, SMTP, etc. in applications such as web browsing, electronic mail, and VoIP. The existing versions of the protocols as well as the cryptographic algorithms they use have vulnerabilities and is not resistant towards Man-In-The- Middle (MITM attacks. Exploiting these vulnerabilities, several attacks have been launched on SSL/TLS such as session hijacking, version degradation, heart bleed, Berserk etc. This paper is a comprehensive analysis of the vulnerabilities in the protocol, attacks launched by exploiting the vulnerabilities and techniques to mitigate the flaws in protocols. A novel taxonomy of the attacks against SSL/TLS has been proposed in this paper.

  17. Detecting Pulsing Denial-of-Service Attacks with Nondeterministic Attack Intervals

    Directory of Open Access Journals (Sweden)

    Xiapu Luo

    2009-01-01

    Full Text Available This paper addresses the important problem of detecting pulsing denial of service (PDoS attacks which send a sequence of attack pulses to reduce TCP throughput. Unlike previous works which focused on a restricted form of attacks, we consider a very broad class of attacks. In particular, our attack model admits any attack interval between two adjacent pulses, whether deterministic or not. It also includes the traditional flooding-based attacks as a limiting case (i.e., zero attack interval. Our main contribution is Vanguard, a new anomaly-based detection scheme for this class of PDoS attacks. The Vanguard detection is based on three traffic anomalies induced by the attacks, and it detects them using a CUSUM algorithm. We have prototyped Vanguard and evaluated it on a testbed. The experiment results show that Vanguard is more effective than the previous methods that are based on other traffic anomalies (after a transformation using wavelet transform, Fourier transform, and autocorrelation and detection algorithms (e.g., dynamic time warping.

  18. Randomized, controlled trial of telcagepant over four migraine attacks

    DEFF Research Database (Denmark)

    Ho, Andrew P; Dahlöf, Carl Gh; Silberstein, Stephen D

    2010-01-01

    This study evaluated the calcitonin gene-related peptide (CGRP) receptor antagonist telcagepant (tablet formulation) for treatment of a migraine attack and across four attacks. Adults with migraine were randomized, double-blind, to telcagepant 140 mg, telcagepant 280 mg, or control treatment...... sequences to treat four moderate-to-severe migraine attacks. Control patients received placebo for three attacks and telcagepant 140 mg for one attack. Efficacy for the first attack (Attack 1) and consistency of efficacy over multiple attacks were assessed. For an individual patient, consistent efficacy...

  19. Pathologic features of fatal shark attacks.

    Science.gov (United States)

    Byard, R W; Gilbert, J D; Brown, K

    2000-09-01

    To examine the pattern of injuries in cases of fatal shark attack in South Australian waters, the authors examined the files of their institution for all cases of shark attack in which full autopsies had been performed over the past 25 years, from 1974 to 1998. Of the seven deaths attributed to shark attack during this period, full autopsies were performed in only two cases. In the remaining five cases, bodies either had not been found or were incomplete. Case 1 was a 27-year-old male surfer who had been attacked by a shark. At autopsy, the main areas of injury involved the right thigh, which displayed characteristic teeth marks, extensive soft tissue damage, and incision of the femoral artery. There were also incised wounds of the right wrist. Bony injury was minimal, and no shark teeth were recovered. Case 2 was a 26-year-old male diver who had been attacked by a shark. At autopsy, the main areas of injury involved the left thigh and lower leg, which displayed characteristic teeth marks, extensive soft tissue damage, and incised wounds of the femoral artery and vein. There was also soft tissue trauma to the left wrist, with transection of the radial artery and vein. Bony injury was minimal, and no shark teeth were recovered. In both cases, death resulted from exsanguination following a similar pattern of soft tissue and vascular damage to a leg and arm. This type of injury is in keeping with predator attack from underneath or behind, with the most severe injuries involving one leg. Less severe injuries to the arms may have occurred during the ensuing struggle. Reconstruction of the damaged limb in case 2 by sewing together skin, soft tissue, and muscle bundles not only revealed that no soft tissue was missing but also gave a clearer picture of the pattern of teeth marks, direction of the attack, and species of predator.

  20. Performance Evaluation of AODV with Blackhole Attack

    Science.gov (United States)

    Dara, Karuna

    2010-11-01

    A Mobile Ad Hoc Network (MANET) is a temporary network set up by a wireless mobile computers moving arbitrary in the places that have no network infrastructure. These nodes maintain connectivity in a decentralized manner. Since the nodes communicate with each other, they cooperate by forwarding data packets to other nodes in the network. Thus the nodes find a path to the destination node using routing protocols. However, due to security vulnerabilities of the routing protocols, mobile ad-hoc networks are unprotected to attacks of the malicious nodes. One of these attacks is the Black Hole Attack against network integrity absorbing all data packets in the network. Since the data packets do not reach the destination node on account of this attack, data loss will occur. In this paper, we simulated the black hole attack in various mobile ad-hoc network scenarios using AODV routing protocol of MANET and have tried to find a effect if number of nodes are increased with increase in malicious nodes.

  1. Distributed Denial of Service Attacks: A Review

    Directory of Open Access Journals (Sweden)

    Sonali Swetapadma Sahu

    2014-01-01

    Full Text Available A wireless sensor network (WSN is a wireless network consisting of spatially distributed autonomous devices using sensors to monitor physical or environmental conditions.WSN is a fluorishing network that has numerous applications and could be used in diverse scenarios. DDoS (Distributed Denial of Service is an attack where a number of compromised systems attack a single target, thereby causing denial of service for users of the targeted system. The flood of incoming messages to the target system essentially forces it to shut down, thereby denying service to the system to legitimate users.Not much research work has been done in DDoS in WSN.We are conducting a review on DDoS attack to show its impact on networks and to present various defensive, detection and preventive measures adopted by researchers till now.

  2. Effect of attack and cone angels on air flow characteristics for staggered wing shaped tubes bundle

    Science.gov (United States)

    Sayed Ahmed, Sayed E.; Ibrahiem, Emad Z.; Mesalhy, Osama M.; Abdelatief, Mohamed A.

    2014-12-01

    An experimental and numerical study has been conducted to clarify fluid flow characteristics and pressure drop distributions of a cross-flow heat exchanger employing staggered wing-shaped tubes at different angels of attack. The water-side Rew and the air-side Rea were at 5 × 102 and at from 1.8 × 103 to 9.7 × 103, respectively. Three cases of the tubes arrangements with various angles of attack, row angles of attack and 90° cone angles were employed at the considered Rea range. Correlation of pressure drop coefficient Pdc in terms of Rea, design parameters for the studied cases were presented. The flow pattern around the staggered wing-shaped tubes bundle were predicted using the commercial CFD FLUENT 6.3.26 software package. Results indicated that the values of Pdc increased with the angle of attack from 0° to 45°, while the opposite was true for angles of attack from 135° to 180°. The values of Pdc for the arrangements of (θ1,2,3 = 45°), (θ1 = 45°, θ2 = 0°, θ3 = 45°), and (θ1,2,3 = 0°) were lower than those for the arrangement of (ϕ1 = ϕ2 = ϕ3 = 90°) by about 33, 53, and 91 %, respectively. Comparisons between the experimental and numerical results of the present study and those obtained by similar previous studies showed good agreements.

  3. The diagnosis of transient ischemic attacks

    NARCIS (Netherlands)

    P.J. Koudstaal (Peter Jan)

    1989-01-01

    textabstractThe diagnosis of transient ischemic attack (TIA) is fraught with difficulty, since the diagnosis rests entirely upon the history of the patient's symptoms and the neurologist's skill in questioning the patient. The aim of this thesis is to investigate various measures to improve the reli

  4. Chemical Attack of Malaysian Pozzolans Concrete

    Directory of Open Access Journals (Sweden)

    Mohd Hilton Ahmad

    2011-09-01

    Full Text Available Malaysia produces more than 10 million tonne of by-product from industrial sector per year. As the environmental impact concerns, more than half of the by-product can be recycled to be used as construction materials. One of them is pozzolan, a cement replacing material that can be used to enhance the properties of the concrete. This paper studies the chemical attack to local prozzolans concrete. The parameters studied include weight loss, length change, and residual strength of local pozzolans concrete after been exposed to severe environment. The specimen were tested under normal room temperature, exposed to magnesium sulfate, MgSO4. 2H2O where both sulfate attack and acid attack take place. Two series of pozzolans< which is Pulverized fly ash (PFA and Palm oil fuel ash (POFA were identified. Another series of admixture, Quarry Dust (QD from quarry waste that contain high amount of silica content also been carried out. Each series will study the effect of cement replacement percentage of 5%, 10% and 15%. The parameters were compared to conventional ordinary Portland cement (OPC concrete as control mix. Accelerated testing was conducted at 3, 7, 28, 56 and 90 days. The result shows that the local pozzolans concrete were found to be in good resistance against sulfate attack compared to conventional concrete. Compared to all series conducted, series of PFA replacement gave the best resistance followed by POFA and QD replacement series.

  5. Generalization of the Euler Angles

    Science.gov (United States)

    Bauer, Frank H. (Technical Monitor); Shuster, Malcolm D.; Markley, F. Landis

    2002-01-01

    It is shown that the Euler angles can be generalized to axes other than members of an orthonormal triad. As first shown by Davenport, the three generalized Euler axes, hereafter: Davenport axes, must still satisfy the constraint that the first two and the last two axes be mutually perpendicular if these axes are to define a universal set of attitude parameters. Expressions are given which relate the generalized Euler angles, hereafter: Davenport angles, to the 3-1-3 Euler angles of an associated direction-cosine matrix. The computation of the Davenport angles from the attitude matrix and their kinematic equation are presented. The present work offers a more direct development of the Davenport angles than Davenport's original publication and offers additional results.

  6. Recovery of human remains after shark attack.

    Science.gov (United States)

    Byard, Roger W; James, Ross A; Heath, Karen J

    2006-09-01

    Two cases of fatal shark attack are reported where the only tissues recovered were fragments of lung. Case 1: An 18-year-old male who was in the sea behind a boat was observed by friends to be taken by a great white shark (Carcharodon carcharias). The shark dragged him under the water and then, with a second shark, dismembered the body. Witnesses noted a large amount of blood and unrecognizable body parts coming to the surface. The only tissues recovered despite an intensive beach and sea search were 2 fragments of lung. Case 2: A 19-year-old male was attacked by a great white shark while diving. A witness saw the shark swim away with the victim's body in its mouth. Again, despite intensive beach and sea searches, the only tissue recovered was a single piece of lung, along with pieces of wetsuit and diving equipment. These cases indicate that the only tissue to escape being consumed or lost in fatal shark attacks, where there is a significant attack with dismemberment and disruption of the integrity of the body, may be lung. The buoyancy of aerated pulmonary tissue ensures that it rises quickly to the surface, where it may be recovered by searchers soon after the attack. Aeration of the lung would be in keeping with death from trauma rather than from drowning and may be a useful marker in unwitnessed deaths to separate ante- from postmortem injury, using only relatively small amounts of tissues. Early organ recovery enhances the identification of human tissues as the extent of morphologic alterations by putrefactive processes and sea scavengers will have been minimized. DNA testing is also possible on such recovered fragments, enabling confirmation of the identity of the victim.

  7. Quantitative Verification and Synthesis of Attack-Defence Scenarios

    DEFF Research Database (Denmark)

    Aslanyan, Zaruhi; Nielson, Flemming; Parker, David

    2016-01-01

    Attack-defence trees are a powerful technique for formally evaluating attack-defence scenarios. They represent in an intuitive, graphical way the interaction between an attacker and a defender who compete in order to achieve conflicting objectives. We propose a novel framework for the formal...... analysis of quantitative properties of complex attack-defence scenarios, using an extension of attack-defence trees which models temporal ordering of actions and allows explicit dependencies in the strategies adopted by attackers and defenders. We adopt a game-theoretic approach, translating attack......-defence trees to two-player stochastic games, and then employ probabilistic model checking techniques to formally analyse these models. This provides a means to both verify formally specified security properties of the attack-defence scenarios and, dually, to synthesise strategies for attackers or defenders...

  8. Analysis of the SYN Flood DoS Attack

    Directory of Open Access Journals (Sweden)

    Mitko Bogdanoski

    2013-06-01

    Full Text Available The paper analyzes systems vulnerability targeted by TCP (Transmission Control Protocol segments when SYN flag is ON, which gives space for a DoS (Denial of Service attack called SYN flooding attack or more often referred as a SYN flood attack. The effects of this type of attack are analyzed and presented in OPNET simulation environment. Furthermore, the paper presents two anomaly detection algorithms as an effective mechanism against this type of attack. Finally, practical approaches against SYN flood attack for Linux and Windows environment which are followed by are shown.

  9. A Survey of Mobile Ad Hoc Network Attacks

    Directory of Open Access Journals (Sweden)

    PRADIP M. JAWANDHIYA,

    2010-09-01

    Full Text Available Security is an essential requirement in mobile ad hoc network (MANETs. Compared to wired networks, MANETs are more vulnerable to security attacks due to the lack of a trusted centralized authority and limited resources. Attacks on ad hoc networks can be classified as passive and active attacks, depending on whether the normal operation of the network is disrupted or not. In this paper, we are describing the all prominent attacks described in literature in a consistent manner to provide a concise comparison on attack types. To the best of our knowledge, this is the first paper that studies all the existing attacks on MANETs.

  10. Research and Implementation of Three HTTPS Attacks

    Directory of Open Access Journals (Sweden)

    Kefei Cheng

    2011-05-01

    Full Text Available With the rapid development of network applications, the issues of Network transmission security become very important. Therefore, SSL protocol is more and more widely used in a variety of network services. But the SSL protocol itself is not perfect, in practice, there are also problems. For the deficiencies of endpoint authentication in the SSL handshake process, the paper analyzes two kinds of defects existing in the SSL hand-shake process. Firstly, handshake process, in the first stage of the SSL connection, using plaintexts, existing the possibility of  being monitored and tampered. Secondly, SSL deployment of the actual application. Because of considering the factors about the performance of the network connection, that usually uses the way of switch connection based on HTTP protocol. In response to these deficiencies, this thesis adopts the two ways of forged certificates and converting the data stream from HTTPS to HTTP to attack them. In addition, a new attack mode against the data stream of HTTPS is designed and implemented. Experiments show that the above three methods cause significant security risks to HTTPS communications. Therefore, taking a static ARP table, enhanced certificate mechanism and mutual authentication of three different measures are proposed to enhance network security in the paper. It is shown that three ways can relative effectively defense against attacks on HTTPS in the experiments.

  11. Denial of Service Attack Techniques: Analysis, Implementation and Comparison

    Directory of Open Access Journals (Sweden)

    Khaled Elleithy

    2005-02-01

    Full Text Available A denial of service attack (DOS is any type of attack on a networking structure to disable a server from servicing its clients. Attacks range from sending millions of requests to a server in an attempt to slow it down, flooding a server with large packets of invalid data, to sending requests with an invalid or spoofed IP address. In this paper we show the implementation and analysis of three main types of attack: Ping of Death, TCP SYN Flood, and Distributed DOS. The Ping of Death attack will be simulated against a Microsoft Windows 95 computer. The TCP SYN Flood attack will be simulated against a Microsoft Windows 2000 IIS FTP Server. Distributed DOS will be demonstrated by simulating a distribution zombie program that will carry the Ping of Death attack. This paper will demonstrate the potential damage from DOS attacks and analyze the ramifications of the damage.

  12. Robustness of Complex Networks against Attacks Guided by Damage

    CERN Document Server

    Wang, Hui; Xu, Xiaomin; Xiao, Yanghua; Wang, Wei

    2011-01-01

    Extensive researches have been dedicated to investigating the performance of real networks and synthetic networks against random failures or intentional attack guided by degree (degree attack). Degree is one of straightforward measures to characterize the vitality of a vertex in maintaining the integrity of the network but not the only one. Damage, the decrease of the largest component size that was caused by the removal of a vertex, intuitively is a more destructive guide for intentional attack on networks since the network functionality is usually measured by the largest component size. However, it is surprising to find that little is known about behaviors of real networks or synthetic networks against intentional attack guided by damage (damage attack), in which adversaries always choose the vertex with the largest damage to attack. In this article, we dedicate our efforts to understanding damage attack and behaviors of real networks as well as synthetic networks against this attack. To this end, existing ...

  13. Mitigation of Malicious Attacks on Networks

    CERN Document Server

    Schneider, Christian M; Andrade, Jose S; Havlin, Shlomo; Herrmann, Hans J; 10.1073/pnas.1009440108

    2011-01-01

    Terrorist attacks on transportation networks have traumatized modern societies. With a single blast, it has become possible to paralyze airline traffic, electric power supply, ground transportation or Internet communication. How and at which cost can one restructure the network such that it will become more robust against a malicious attack? We introduce a unique measure for robustness and use it to devise a method to mitigate economically and efficiently this risk. We demonstrate its efficiency on the European electricity system and on the Internet as well as on complex networks models. We show that with small changes in the network structure (low cost) the robustness of diverse networks can be improved dramatically while their functionality remains unchanged. Our results are useful not only for improving significantly with low cost the robustness of existing infrastructures but also for designing economically robust network systems.

  14. Comparative Analysis of Routing Attacks in Ad Hoc Network

    Directory of Open Access Journals (Sweden)

    Bipul Syam Purkayastha

    2012-03-01

    Full Text Available In the mobile ad hoc networks the major role is played by the routing protocols in order to route the data from one mobile node to another mobile node. But in such mobile networks, routing protocols are vulnerable to various kinds of security attacks such as blackhole node attacks. The routing protocols of MANET are unprotected and hence resulted into the network with the malicious mobile nodes in the network. These malicious nodes in the network are basically acts as attacks in the network. In this paper, we modify the existing DSR protocol with the functionality of attacks detection without affecting overall performance of the network. Also, we are considering the various attacks on mobile ad hoc network called blackhole attack, flooding attack and show the comparative analysis of these attacks using network simulator ns-2.

  15. A Formal Classification of Internet Banking Attacks and Vulnerabilities

    Directory of Open Access Journals (Sweden)

    Laerte Peotta

    2011-02-01

    Full Text Available A formal classification of attacks and vulnerabilities that affect current internet banking systems is presented along with two attacks which demonstrate the insecurity of such systems. Based ona thoroughanalysis of current security models, we propose a guidelines for designing secure internet banking systems which are not affected by the presented attacks and vulnerabilities.

  16. A computer program for the calculation of the flow field in supersonic mixed-compression inlets at angle of attack using the three-dimensional method of characteristics with discrete shock wave fitting

    Science.gov (United States)

    Vadyak, J.; Hoffman, J. D.; Bishop, A. R.

    1978-01-01

    The calculation procedure is based on the method of characteristics for steady three-dimensional flow. The bow shock wave and the internal shock wave system were computed using a discrete shock wave fitting procedure. The general structure of the computer program is discussed, and a brief description of each subroutine is given. All program input parameters are defined, and a brief discussion on interpretation of the output is provided. A number of sample cases, complete with data deck listings, are presented.

  17. Methods of Identifying and Preventing SQL Attacks

    Directory of Open Access Journals (Sweden)

    Bojken Shehu

    2012-11-01

    Full Text Available The paper begins by identifying the organizations which are vulnerable to the SQL attack referred to as an SQL injection attack. The term SQL injection attack is defined and a diagram is used to illustrate the way that attack occurs. In another section, the paper identifies the methods used to detect an attack to SQL, whereby the techniques are discussed extensively using relevant diagrams for illustration. The other sections cover the preventive methods, where the methods are also discussed with an illustration using diagrams.

  18. Unified communications forensics anatomy of common UC attacks

    CERN Document Server

    Grant, Nicholas Mr

    2013-01-01

    Unified Communications Forensics: Anatomy of Common UC Attacks is the first book to explain the issues and vulnerabilities and demonstrate the attacks, forensic artifacts, and countermeasures required to establish a secure (UC) environment. This book is written by leading UC experts Nicholas Grant and Joseph W. Shaw II and provides material never before found on the market, including: analysis of forensic artifacts in common UC attacks an in-depth look at established UC technologies and attack exploits hands-on understanding of UC attack vectors and associated countermeasures

  19. Activity Modelling and Comparative Evaluation of WSN MAC Security Attacks

    DEFF Research Database (Denmark)

    Pawar, Pranav M.; Nielsen, Rasmus Hjorth; Prasad, Neeli R.

    2012-01-01

    and initiate security attacks that disturb the normal functioning of the network in a severe manner. Such attacks affect the performance of the network by increasing the energy consumption, by reducing throughput and by inducing long delays. Of all existing WSN attacks, MAC layer attacks are considered....... The second aim of the paper is to simulate these attacks on hybrid MAC mechanisms, which shows the performance degradation of aWSN under the considered attacks. The modelling and implementation of the security attacks give an actual view of the network which can be useful in further investigating secure......Applications of wireless sensor networks (WSNs) are growing tremendously in the domains of habitat, tele-health, industry monitoring, vehicular networks, home automation and agriculture. This trend is a strong motivation for malicious users to increase their focus on WSNs and to develop...

  20. The Semiotic and Conceptual Genesis of Angle

    Science.gov (United States)

    Tanguay, Denis; Venant, Fabienne

    2016-01-01

    In the present study, we try to understand how students at the end of primary school conceive of angle: Is an angle a magnitude for them or a geometric figure, and how do they manage to coordinate the two aspects in their understanding of the concepts of angle and of angle measurement? With the aim of better grasping the way "angle" is…

  1. Quantitative Verification and Synthesis of Attack-Defence Scenarios

    DEFF Research Database (Denmark)

    Aslanyan, Zaruhi; Nielson, Flemming; Parker, David

    2016-01-01

    which guarantee or optimise some quantitative property, such as the probability of a successful attack, the expected cost incurred, or some multi-objective trade-off between the two. We implement our approach, building upon the PRISM-games model checker, and apply it to a case study of an RFID goods...... analysis of quantitative properties of complex attack-defence scenarios, using an extension of attack-defence trees which models temporal ordering of actions and allows explicit dependencies in the strategies adopted by attackers and defenders. We adopt a game-theoretic approach, translating attack......-defence trees to two-player stochastic games, and then employ probabilistic model checking techniques to formally analyse these models. This provides a means to both verify formally specified security properties of the attack-defence scenarios and, dually, to synthesise strategies for attackers or defenders...

  2. PERFORMANCE EVALUATION OF WIRELESS SENSOR NETWORK UNDER HELLO FLOOD ATTACK

    Directory of Open Access Journals (Sweden)

    Mohammad Abdus Salam

    2016-03-01

    Full Text Available Wireless sensor network (WSN is highly used in many fields. The network consists of tiny lightweight sensor nodes and is largely used to scan or detect or monitor environments. Since these sensor nodes are tiny and lightweight, they put some limitations on resources such as usage of power, processing given task, radio frequency range. These limitations allow network vulnerable to many different types of attacks such as hello flood attack, black hole, Sybil attack, sinkhole, and many more. Among these attacks, hello flood is one of the most important attacks. In this paper,we have analyzed the performance of hello flood attack and compared the network performance as number of attackers increases. Network performance is evaluated by modifying the ad-hoc on demand distance vector (AODV routing protocol by using NS2 simulator. It has been tested under different scenarios like no attacker, single attacker, and multiple attackers to know how the network performance changes. The simulation results show that as the number of attackers increases the performance in terms of throughput and delay changes.

  3. Impact of Alleged Russian Cyber Attacks

    Science.gov (United States)

    2009-05-01

    March 14, 2009). 96 Ivan Buranov, Vladimir Vodo, and Seda Yegikyan, Pro-Kremlin Activist Admits Attack on Estonian Websites, Denies Criminal...Vladimir Vodo, and Seda Yegikyan, Pro-Kremlin Activist Admits Attack on Estonian Websites, Denies Criminal Wrongdoing, Translated by Open Source...Buranov, Ivan; Vodo, Vladimir; and Yegikyan, Seda Pro-Kremlin Activist Admits Attack on Estonian Websites, Denies Criminal Wrongdoing, Translated

  4. 原发性闭角型青光眼单侧急性发作对侧眼激光虹膜周边切除术后随访研究%Follow-up of laser peripheral iridotomy in fellow eyes with unilateral acute attack of primary angle closure glaucoma

    Institute of Scientific and Technical Information of China (English)

    张海涛; 杨华; 徐英英

    2011-01-01

    Background Laser peripheral iridotomy(LPI) is used as the primary therapy for the eyes at risk of angle closure.But there are still 28% eyes with primary angle closure suspect occur angle closure within 2 years after LPI.It is necessary to explore the associated factors of the efficacy of LPI.Objective The aim of this study was to explore the changes of intraocular pressure(IOP) and anterior chamber angle in the fellow eyes of patients with unilateral acute attack of primary angle closure glaucoma (PACG) and analyze the relevant factors influencing the successful rate of LPI.Methods Eighty-seven fellow eyes received LPI from 87 patients with unilateral acute attack of PACG were included in this study and retrospectively analyzed.The IOP and gonioscopy were performed before and 1 week,3,6,9,12 months after LPI.Successful signs of LPI were defined as an IOP 6-21mmHg without any anti-glaucoma medication,none of glaucomatous neuropathy and the coincident visual field loss,and no need of additional glaucomatous medication or surgery.This study was approved by Ethic Committee of the First Hospital of Xinxiang Medical College,and written informed consent was obtained from each patient.Results Seventy-nine eyes of 79 cases finished the medical visit throughout the follow-up duration with the age 61.4±0.4 years and 33(41.8%) males and 46(58.2%) females.The mean IOP was lowed in various time points after LPI in comparison with before operation with the general difference among different time visiting groups(F=4.056,P<0.01).Shaffer grade was increased in superior,temporal and nasal quadrants and significant differences were found between 1 week group,3 months group or 6 months group and before operation group (P<0.05).LPI lessened the range of appositional angle closure (AAC) in postoperative 1 week group and 3 months group compared with pre-operative group (P<0.05),but no statistically significant reduce was seen in range of AAC from 6 months through 12 months after

  5. Variability of clinical features in attacks of migraine with aura

    DEFF Research Database (Denmark)

    Hansen, Jakob M; Goadsby, Peter J; Charles, Andrew C

    2016-01-01

    BACKGROUND: There is significant variability in the clinical presentation of migraine, both among patients, and between attacks in an individual patient. We examined clinical features of migraine with aura in a large group of patients enrolled in a clinical trial, and compared retrospective...... migraine attack characteristics reported upon enrollment in the trial with those recorded prospectively in the trial. METHODS: Patients with migraine (n = 267) with typical visual aura in more than 30% of their attacks were enrolled from 16 centers for a clinical trial. Upon enrollment, patients provided...... a detailed retrospective description of the clinical features of their attacks of migraine. During the trial, clinical symptoms in migraine attacks starting with aura were recorded prospectively in 861 attacks. RESULTS: Retrospectively reported visual aura symptoms were variable and often overlapping...

  6. REVIEW CLUSTERING MECHANISMS OF DISTRIBUTED DENIAL OF SERVICE ATTACKS

    Directory of Open Access Journals (Sweden)

    Wesam Bhaya

    2014-01-01

    Full Text Available Distributed Denial of Service attacks (DDoS overwhelm network resources with useless or harmful packets and prevent normal users from accessing these network resources. These attacks jeopardize the confidentiality, privacy and integrity of information on the internet. Since it is very difficult to set any predefined rules to correctly identify genuine network traffic, an anomaly-based Intrusion Detection System (IDS for network security is commonly used to detect and prevent new DDoS attacks. Data mining methods can be used in intrusion detection systems, such as clustering k-means, artificial neural network. Since the clustering methods can be used to aggregate similar objects, they can detect DDoS attacks to reduce false-positive rates. In this study, a review of DDoS attacks using clustering data mining techniques is presented. A review illustrates the most recent, state-of-the art science for clustering techniques to detect DDoS attacks.

  7. Public knowledge of heart attack symptoms in Beijing residents

    Institute of Scientific and Technical Information of China (English)

    ZHANG Qing-tan; HU Da-yi; YANG Jin-gang; ZHANG Shou-yan; ZHANG Xin-quan; LIU Shu-shan

    2007-01-01

    Background Definitive treatment for heart attack is early reperfusion with either angioplasty or thrombolytic therapy,and the benefit is strictly time-dependent. Patient outcomes are improved with either therapy when initiated as soon as possible. Recognition of heart attack symptoms is logically tied to taking action to receive prompt emergency care.Inadequate knowledge of heart attack symptoms may prolong delay. The purpose of this study was to document knowledge about heart attack symptoms in Beijing residents and to identify the characteristics associated with increased knowledge of heart attack.Methods A structured survey was conducted in 18 communities in Beijing from March 1 through June 10 in 2006.Addresses and participants were selected randomly following a stratification. The survey was designed to collect knowledge of heart attack symptoms from sampled adults in each community.Results A total of 4627 respondents completed the questionnaires correctly, and 50.29% of them were female. Totally 64.15% of the respondents reported chest pain or discomfort (common symptoms) as a symptom of heart attack; 75.38% reported at least one of the following eight symptoms as a symptom of heart attack: back pain, shortness of breath, arm pain or numbness, nausea or vomiting, neck, jaw or shoulder pain, epigastric pain, sweating, weakness (less common symptoms); 20.36% correctly reported four or more heart attack symptoms, only 7.4% knew all the correct heart attack symptoms, and 28.94% knew about reperfusion therapy for heart attack; 31.7% reported to call 120 or 999 while having a heart attack themselves; however 89.6% reported to call 120 or 999 when someone else is suffering from a heart attack. Very old persons and those with health insurance coverage, high education level, high household income, longer living in Beijing and previous experience with heart disease had greater knowledge of heart attack symptoms.Conclusions Public knowledge of common heart attack

  8. Scaling of misorientation angle distributions

    DEFF Research Database (Denmark)

    Hughes, D.A.; Chrzan, D.C.; Liu, Q.

    1998-01-01

    The measurement of misorientation angle distributions following different amounts of deformation in cold-rolled aluminum and nickel and compressed stainless steel is reported. The sealing of the dislocation cell boundary misorientation angle distributions is studied. Surprisingly, the distributions...... for the small to large strain regimes for aluminum, 304L stainless steel, nickel, and copper (taken from the literature )appear to be identical. Hence the distributions may be "universal." These results have significant implications for the development of dislocation based deformation models. [S0031...

  9. Wind Tunnel Corrections for High Angle of Attack Models,

    Science.gov (United States)

    1981-02-01

    2) . De telles confrontations sont bien entendu specifiquss des maquettes utilises et en particulier devraient Stre developp^es dans le domaine des...d’essais, il y a lieu de tenir compte des qualitds de l’ecoulement aussi bien stationnaire (ascendance, gradient longitudinal de pression) qu’in...luence des divers parametres ne peut etre etudiee isolement car il n’est pas encore possiblt re les faire varier. L’ONERA a dejä public des travaux

  10. X-29 High Angle-of-Attack Flying Qualities

    Science.gov (United States)

    1991-06-01

    40. - o - -- .. IMULP1ION WIIT. PI EDI TED RER MODEL SIMLI Z ON WI1T 4FLIGO 1 UPDR "E: REAO HDEL 20. 0 10 -0 ,. 140, ,. . 20 2... . . .. 3_ Z \\ / (Z II...53 (ConclITded) 312 X-29 USAF SIN 820049 40. FL- IT OR SIL LRTI WITH PRDZIT U RA! 0 O L -0 5 I LATI IO IITH FLIGH UPDR a RE NOD 30...X-29 USAF S/N 820049 20. -SIML LRTIOh WITH PREDI TED RAD MODEL SSIML LRTID1 WITH FLIGHT UPDR TE REPO M000 15. 10. 0 z 0 U 0 . 2. 3. 4-. 5. 6.. 7. 8. 9

  11. Simulation of Attacks for Security in Wireless Sensor Network

    Directory of Open Access Journals (Sweden)

    Alvaro Diaz

    2016-11-01

    Full Text Available The increasing complexity and low-power constraints of current Wireless Sensor Networks (WSN require efficient methodologies for network simulation and embedded software performance analysis of nodes. In addition, security is also a very important feature that has to be addressed in most WSNs, since they may work with sensitive data and operate in hostile unattended environments. In this paper, a methodology for security analysis of Wireless Sensor Networks is presented. The methodology allows designing attack-aware embedded software/firmware or attack countermeasures to provide security in WSNs. The proposed methodology includes attacker modeling and attack simulation with performance analysis (node’s software execution time and power consumption estimation. After an analysis of different WSN attack types, an attacker model is proposed. This model defines three different types of attackers that can emulate most WSN attacks. In addition, this paper presents a virtual platform that is able to model the node hardware, embedded software and basic wireless channel features. This virtual simulation analyzes the embedded software behavior and node power consumption while it takes into account the network deployment and topology. Additionally, this simulator integrates the previously mentioned attacker model. Thus, the impact of attacks on power consumption and software behavior/execution-time can be analyzed. This provides developers with essential information about the effects that one or multiple attacks could have on the network, helping them to develop more secure WSN systems. This WSN attack simulator is an essential element of the attack-aware embedded software development methodology that is also introduced in this work.

  12. Simulation of Attacks for Security in Wireless Sensor Network.

    Science.gov (United States)

    Diaz, Alvaro; Sanchez, Pablo

    2016-11-18

    The increasing complexity and low-power constraints of current Wireless Sensor Networks (WSN) require efficient methodologies for network simulation and embedded software performance analysis of nodes. In addition, security is also a very important feature that has to be addressed in most WSNs, since they may work with sensitive data and operate in hostile unattended environments. In this paper, a methodology for security analysis of Wireless Sensor Networks is presented. The methodology allows designing attack-aware embedded software/firmware or attack countermeasures to provide security in WSNs. The proposed methodology includes attacker modeling and attack simulation with performance analysis (node's software execution time and power consumption estimation). After an analysis of different WSN attack types, an attacker model is proposed. This model defines three different types of attackers that can emulate most WSN attacks. In addition, this paper presents a virtual platform that is able to model the node hardware, embedded software and basic wireless channel features. This virtual simulation analyzes the embedded software behavior and node power consumption while it takes into account the network deployment and topology. Additionally, this simulator integrates the previously mentioned attacker model. Thus, the impact of attacks on power consumption and software behavior/execution-time can be analyzed. This provides developers with essential information about the effects that one or multiple attacks could have on the network, helping them to develop more secure WSN systems. This WSN attack simulator is an essential element of the attack-aware embedded software development methodology that is also introduced in this work.

  13. An Attack Investigation, Characterization and Simulation of Various Attacks in MANET

    Directory of Open Access Journals (Sweden)

    Pratik Gite

    2015-01-01

    Full Text Available Mobile Ad-hoc Network is one of the most popular network technology in the field of research and development community. Due to their dynamic and ad-hoc nature, the network suffers from the various performance and security issues. The main objective of this paper is to evaluate the performance of Ad-hoc On Demand Distance Vector (AODV routing protocol under normal condition and attacks conditions on the basis of different performance metrics. This paper is also concerned about the different kinds of attacks formation viz. Black Hole, Worm Hole, Gray Hole and Denial of Service attacks on MANET environment. In addition of that different kinds of approaches available for detection and prevention of such attacks are also investigated. Finally using different experimentation and simulations through NS-2, the effort is made to identify the effective network characteristics. After concluding the effects and simulation the need of a new Intrusion Detection System (IDS model is presented for future implementation.

  14. The Impact of Black-Hole Attack on ZRP Protocol

    Directory of Open Access Journals (Sweden)

    CHAHIDI Badr

    2016-07-01

    Full Text Available lack of infrastructure in ad hoc networks makes their deployment easier. Each node in an ad hoc network can route data using a routing protocol, which decreases the level of security. Ad hoc networks are exposed to several attacks such as the blackhole attack. In this article, a study has been made on the impact of the attack on the hybrid routing protocol ZRP (Zone Routing Protocol. In this attack a malicious node is placed between two or more nodes in order to drop data. The trick of the attack is simple, the malicious node declares to have the most reliable way to the destination so that the wife destination chooses this path. In this study, NS2 is used to assess the impact of the attack on ZRP. Two metrics measure, namely the packet delivered ratio and end to end delay.

  15. Breakdown of an Inhomogeneous Scale- Free Network Under Intentional Attack

    Institute of Scientific and Technical Information of China (English)

    LIN Guo-Ji; CHENG Xiang; OU-YANG Qi

    2003-01-01

    Using a recently introduced network model with node and connection diversity, we study the breakdown of different scale-free networks under intentional attacks. Our simulation results show that inhomogeneous networks are more sensitive to intentional attack than the homogeneous ones and that the centralization of the networks is an important variable, reflecting the characteristics of the network under intentional attack. Using a recently introduced method we can theoretically develop the critical point of the inhomogeneous networks.

  16. Detection and Isolation of Packet Dropping Attacker in MANETs

    Directory of Open Access Journals (Sweden)

    Ahmed Mohamed Abdalla

    2013-05-01

    Full Text Available Several approaches have been proposed for Intrusion Detection Systems (IDS in Mobile Ad hoc Networks (MANETs. Due to lack of MANETs infrastructure and well defined perimeter MANETs are susceptible to a variety of attacker types. To develop a strong security mechanism it is necessary to understand how malicious nodes can attack the MANETs. A new IDS mechanism is presented based on End-to-End connection for securing Optimized Link State Routing (OLSR routing protocol. This new mechanism is named as Detection and Isolation Packet Dropped Attackers in MANETs (DIPDAM. DIPDAM mechanism based on three ID messages Path Validation Message (PVM , Attacker Finder Message (AFM and Attacker Isolation Message (AIM. DIPDAM mechanism based on End-to-End (E2E communication between the source and the destination is proposed. The simulation results showed that the proposed mechanism is able to detect any number of attackers while keeping a reasonably low overhead in terms of network traffic.

  17. Impact Analysis of Recent DDoS Attacks

    Directory of Open Access Journals (Sweden)

    Ketki Arora

    2011-02-01

    Full Text Available In the present era Internet has changed the way of traditional essential services such as banking, transportation, power, health, and defence being operated. These operations are being replacedby cheaper, more efficient Internet-based applications. It is all because of rapid growth and success of Internet in every sector. Unfortunately with the growth of Internet, count of attacks on Internet has also increased incredibly fast. Denial-of-service attack is one of them, which poses immense threat on the availability. Since, the World is highly dependent on the Internet, availability of the Internet is very critical for the socio-economic growth of the society. Denial-of-service attacks occur almost every day,and the frequency and the volume of these attacks are increasing day by day. One of the biggest challenges before researchers is to find the details of such attacks because due to damaging reputationissues, most of the commercial sites do not even disclose that they were blitzed by such attacks. Details of attacks can guide very well in the formulation of comprehensive defensive solution for such attacks. In this paper, an overview on DDoS problem, major factors causing DDoS attacks are demonstrated, brief detail of most recent DDoS incidents on online organizations is outlined and finally, the need for a comprehensive distributed solution is highlighted.

  18. Non-harmful insertion of data mimicking computer network attacks

    Energy Technology Data Exchange (ETDEWEB)

    Neil, Joshua Charles; Kent, Alexander; Hash, Jr, Curtis Lee

    2016-06-21

    Non-harmful data mimicking computer network attacks may be inserted in a computer network. Anomalous real network connections may be generated between a plurality of computing systems in the network. Data mimicking an attack may also be generated. The generated data may be transmitted between the plurality of computing systems using the real network connections and measured to determine whether an attack is detected.

  19. Flooding Distributed Denial of Service Attacks-A Review

    Directory of Open Access Journals (Sweden)

    Khadijah W.M. Ghazali

    2011-01-01

    Full Text Available Problem statement: Flaws either in users’ implementation of a network or in the standard specification of protocols has resulted in gaps that allow various kinds of network attack to be launched. Of the kinds of network attacks, denial-of-service flood attacks have caused the most severe impact. Approach: This study reviews recent researches on flood attacks and their mitigation, classifying such attacks as either high-rate flood or low-rate flood. Finally, the attacks are compared against criteria related to their characteristics, methods and impacts. Results: Denial-of-service flood attacks vary in their rates, traffic, targets, goals and impacts. However, they have general similarities that are the methods used are flooding and the main purpose is to achieve denial of service to the target. Conclusion/Recommendations: Mitigation of the denial-of-service flood attacks must correspond to the attack rates, traffic, targets, goals and impacts in order to achieve effective solution.

  20. Fake BTS Attacks of GSM System on Software Radio Platform

    Directory of Open Access Journals (Sweden)

    Yubo Song

    2012-02-01

    Full Text Available The 2G GSM communication system only provides one-way authentication mechanism which just authenticate the identities of mobile users. As we know, this is not resistant to fake BTS attack. But for the huge cost for building a fake BTS before, this kind of attack were not really implemented before. This paper presents an implement of fake BTS based on software radio technologies. Furthermore, this paper discusses two types of fake BTS attacks on our software radio platform. The first attack is IMSI/IMEI catch attack, which can get the mobile phone’s IMSI and IMEI. With this information, attacker can got the track of the man with this phone. The second attack is selective jamming attack. After get the IMSI and IMEI of the mobile phone, the attackers can decide whether the mobile phone is blocked or not. We will analyze the GSM protocol which is relevant to the interception system and later present the performance of such a system by real tests and demonstrate its feasibility.

  1. The timing of terrorist attacks: An optimal stopping approach

    Directory of Open Access Journals (Sweden)

    Thomas Jensen

    2016-02-01

    Full Text Available I use a simple optimal stopping model to derive policy relevant insights on the timing of one-shot attacks by small autonomous terrorist units or “lone wolf” individuals. A main insight is that an increase in proactive counterterrorism measures can lead to a short term increase in the number of attempted terrorist attacks because it makes it more risky for existing terrorist units to pursue further development of capabilities. This is consistent with the events in London in 2005 where a terrorist attack on 7 July was followed by a similar but unsuccessful attack two weeks later.

  2. Optimal counterterrorism and the recruitment effect of large terrorist attacks

    DEFF Research Database (Denmark)

    Jensen, Thomas

    2011-01-01

    We analyze a simple dynamic model of the interaction between terrorists and authorities. Our primary aim is to study optimal counterterrorism and its consequences when large terrorist attacks lead to a temporary increase in terrorist recruitment. First, we show that an increase in counterterrorism...... makes it more likely that terrorist cells plan small rather than large attacks and therefore may increase the probability of a successful attack. Analyzing optimal counterterrorism we see that the recruitment effect makes authorities increase the level of counterterrorism after large attacks. Therefore...

  3. An Improved Model of Attack Probability Prediction System

    Institute of Scientific and Technical Information of China (English)

    WANG Hui; LIU Shufen; ZHANG Xinjia

    2006-01-01

    This paper presents a novel probability generation algorithm to predict attacks from an insider who exploits known system vulnerabilities through executing authorized operations. It is different from most intrusion detection systems (IDSs) because these IDSs are inefficient to resolve threat from authorized insiders. To deter cracker activities, this paper introduces an improved structure of augmented attack tree and a notion of "minimal attack tree", and proposes a new generation algorithm of minimal attack tree. We can provide a quantitative approach to help system administrators make sound decision.

  4. Performance analysis of black hole attacks in geographical routing MANET

    Directory of Open Access Journals (Sweden)

    H.J Shanthi

    2014-10-01

    Full Text Available The MANET (Mobile Adhoc Network is vulnerable to several types of attacks. The most commonly classified attack is black hole attack, which is carried by single or multiple attackers, advertising itself of having a short fresh route to transmit data. The aim is to ensure security against the black hole attack and analyze the performance in geographical routing. The simple method is to send data as small blocks instead of entire data. The traffic is monitored independently in its neighborhood. The mechanism uses geographic information to detect variance in neighbor relations and node movements. We analyze the black hole attack in two popular location based protocol LAR and DREAM. It provides the stimulation study of black hole attack with the minimum attacker and also provides analysis on the parameters such as throughput, packet delivery and delay done with OMNET++ simulator. The simulation results show that packet loss increases and throughput decreases in the network with a black hole node in geographical routing. The proposed mechanism can be combined with existent routing protocols to defend against black hole attacks.

  5. Prevention Of WormholeAttacks In Geographic Routing Protocol

    Directory of Open Access Journals (Sweden)

    E.Poornima,

    2011-01-01

    Full Text Available As mobile ad hoc network applications are deployed, security emerges as a central requirement..Position aided routing protocols can offer a significant performance increase over traditional ad hoc routing protocols. Boundary State Routing (BSR is a geographic routing protocol which routes the data using the location of the nodes. Geographic routing protocols are known to be particularly susceptible to attacks.. In this paper we present the possible attacks on BSR protocol. One of the most popular and serious attacks in ad hoc networks is wormhole attack in which two or more colluding attackers record packets at one location, and tunnel them to another location for a replay at that remote location. A wormhole attack is very powerful, and preventing the attack has proven to be very difficult. In this paper, we devise efficient methods to detect and avoid wormhole attacks in the BSR protocol. The first method namely Reverse Routing Scheme (RRS attempts to detect the intrusion action .The second technique namely Authentication of Nodes Scheme (ANS uses cryptographic concepts to detect and prevent wormhole attacks. It not only detects the fake route but also adopts preventive measures against action wormhole nodes from reappearing during routing. The proposed system is designed in Boundary state routing (BSRprotocol and analysis and simulations are performed in network simulator (NS-2.

  6. Optimisation of Fan Blade Angle

    Directory of Open Access Journals (Sweden)

    Swaroop M P

    2017-01-01

    Full Text Available This report represents the optimization of fan blade angle in accordance with the various room temperatures that can be in the tropical area like India. We took this work mainly because cooling is an important factor now a days in every area where construction and rooms are there and ceiling fans are the most common device that is commonly used. So it is of utmost importance to tweak the performance of this ceiling fan so that it can function in its most optimal condition. We have modeled the fan in a modeling software (SOLIDWORKS and imported that into an analyzing software (ANSYS and a result is generated on the various blade angles (0, 4, 8 and 12.5 degrees in accordance to room conditions. A trend line curve with the obtained data is expected as the result which can be crucial for designing of future fans

  7. Pattern association--a key to recognition of shark attacks.

    Science.gov (United States)

    Cirillo, G; James, H

    2004-12-01

    Investigation of a number of shark attacks in South Australian waters has lead to recognition of pattern similarities on equipment recovered from the scene of such attacks. Six cases are presented in which a common pattern of striations has been noted.

  8. Understanding How Components of Organisations Contribute to Attacks

    DEFF Research Database (Denmark)

    Gu, Min; Aslanyan, Zaruhi; Probst, Christian W.

    2016-01-01

    components quickly results in a large quantity of interrelations, which are hard to grasp. In this work we present several approaches for visualising attributes of attacks such as likelihood of success, impact, and required time or skill level. The resulting visualisations provide a link between attacks...

  9. Temporal characterization of experimental recorder attack transients.

    Science.gov (United States)

    Ernoult, A; Fabre, B

    2017-01-01

    Through the comparison of notes produced on two recorders by one novice and two experienced players in musical contexts, this study identifies the temporal aspects of the attack transients which are controlled by the player and those which are imposed by the dynamic response of the instrument. The rise times of mouth pressure used by the novice player are longer than the ones produced by the experienced players, which are the shortest ones preserving the control of the jet velocity rise times. For shortest rise times, the jet development is limited by the inertia of the channel. The onset time of the acoustic oscillation is divided in two parts: the time needed to initiate the oscillation and the duration of the growth. The times of growth are similar for the novice and the experienced players, which is linked to the similarity of the gain characterizing the linear behavior of the instrument. The times needed to initiate the oscillation show the most pronounced difference between the two types of players; it is much longer for a novice player. This difference is interpreted in terms of the initial input of energy in the system which is larger for the experienced players.

  10. Performance evaluation of DSR Protocol under DoS attack

    Directory of Open Access Journals (Sweden)

    Ms. Trupti Patel

    2012-03-01

    Full Text Available A mobile ad-hoc network (MANET consists of mobile hosts equipped with wireless communication devices. A Mobile Ad hoc Network is a self-organizing, infrastructure less, multi-hop network. The transmission of a mobile host is received by all hosts within its transmission range due to the broadcast nature of wireless communication and unidirectional antenna. If two wireless hosts are out of their transmission ranges in the ad hoc networks, other mobile hosts located between them can forward their message, which effectively builds connected networks among the mobile hosts in the deployed area. One main challenge in design of these networks is their vulnerable nature to security attack. These attacks can be deployed by insider or outsider attacker. Sometime, the node from network can be attacker. This is happen because of mobility of nodes and changing network topology. There are different kind of attacks available in literature and can be implemented on MANET. One of these attacks is Grey Hole attack that has dangerous effect on Mobile Ad-Hoc Network. In this paper, we study the effect of Grey Hole attack on Dynamic Source Routing (DSR protocol in Mobile Ad-Hoc Network.

  11. Robustness of Complex Networks under Attack and Repair

    Institute of Scientific and Technical Information of China (English)

    HU Bin; LI Fang; ZHOU Hou-Shun

    2009-01-01

    To study the robustness of complex networks under attack and repair,we introduce a repair model of complex networks.Based on the model,we introduce two new quantities,i.e.attack fraction f_a and the maximum degree of the nodes that have never been attacked K_a,to study analytically the critical attack fraction and the relati ve size of the giant component of complex networks under attack and repair,using the method of generating function.We show analytically and numerically that the repair strategy significantly enhances the robustness of the scale-free network and the effect of robustness improvement is better for the scale-free networks with a smaller degree exponent.We discuss the application of our theory in relation to the understanding of robustness of complex networks with reparability.

  12. Effectiveness of the Call in Beach Volleyball Attacking Play

    Directory of Open Access Journals (Sweden)

    Künzell Stefan

    2014-12-01

    Full Text Available In beach volleyball the setter has the opportunity to give her or his hitter a “call”. The call intends that the setter suggests to her or his partner where to place the attack in the opponent’s court. The effectiveness of a call is still unknown. We investigated the women’s and men’s Swiss National Beach Volleyball Championships in 2011 and analyzed 2185 attacks. We found large differences between female and male players. While men called in only 38.4% of attacks, women used calls in 85.5% of attacks. If the male players followed a given call, 63% of the attacks were successful. The success rate of attacks without any call was 55.8% and 47.6% when the call was ignored. These differences were not significant (χ2(2 = 4.55, p = 0.103. In women’s beach volleyball, the rate of successful attacks was 61.5% when a call was followed, 35% for attacks without a call, and 42.6% when a call was ignored. The differences were highly significant (χ2(2 = 23.42, p < 0.0005. Taking into account the findings of the present study, we suggested that the call was effective in women’s beach volleyball, while its effect in men’s game was unclear. Considering the quality of calls we indicate that there is a significant potential to increase the effectiveness of a call.

  13. Robustness of controllability for networks based on edge-attack.

    Science.gov (United States)

    Nie, Sen; Wang, Xuwen; Zhang, Haifeng; Li, Qilang; Wang, Binghong

    2014-01-01

    We study the controllability of networks in the process of cascading failures under two different attacking strategies, random and intentional attack, respectively. For the highest-load edge attack, it is found that the controllability of Erdős-Rényi network, that with moderate average degree, is less robust, whereas the Scale-free network with moderate power-law exponent shows strong robustness of controllability under the same attack strategy. The vulnerability of controllability under random and intentional attacks behave differently with the increasing of removal fraction, especially, we find that the robustness of control has important role in cascades for large removal fraction. The simulation results show that for Scale-free networks with various power-law exponents, the network has larger scale of cascades do not mean that there will be more increments of driver nodes. Meanwhile, the number of driver nodes in cascading failures is also related to the edges amount in strongly connected components.

  14. Understanding bifurcation of slow versus fast cyber-attackers

    NARCIS (Netherlands)

    Wieren, van Maarten; Doerr, Christian; Jacobs, Vivian; Pieters, Wolter; Livraga, Giovanni; Torra, Vicenç; Aldini, Alessandro; Martinelli, Fabio; Suri, Neeraj

    2016-01-01

    Anecdotally, the distinction between fast “Smash-and-Grab” cyber-attacks on the one hand and slow attacks or “Advanced Persistent Threats” on the other hand is well known. In this article, we provide an explanation for this phenomenon as the outcome of an optimization from the perspective of the att

  15. Ethical Considerations of Computer Network Attack in Information Warfare

    Science.gov (United States)

    2001-01-16

    attack/destruction, and special information operations (SIO). CNA and the other methods of offensive IO represent the incorporation of information...psychological operations, electronic warfare, physical attack and/or destruction, and special information operations, and could include computer network...to computer networks to record information sent over them. 41 special information operations. Information operations that by their sensitive nature

  16. Treatment of HAE Attacks in the Icatibant Outcome Survey

    DEFF Research Database (Denmark)

    Hernández Fernandez de Rojas, Dolores; Ibañez, Ethel; Longhurst, Hilary;

    2015-01-01

    BACKGROUND: Icatibant, a selective bradykinin B2 receptor antagonist for the treatment of acute hereditary angio-oedema (HAE) attacks in adults, can be administered by health care professionals (HCPs) or self-administered. This analysis compared characteristics and outcomes of acute HAE attacks t...

  17. Attack Vulnerability of Network with Duplication-Divergence Mechanism

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    We study the attack vulnerability of network with duplication-divergence mechanism. Numerical results have shown that the duplication-divergence network with larger retention probability a is more robust against target attack relatively. Furthermore, duplication-divergence network is broken down more quickly than its counterpart BA network under target attack. Such result is consistent with the fact of WWW and Internet networks under target attack. So duplication-divergence model is a more realistic one for us to investigate the characteristics of the world wide web in future. We also observe that the exponent 7 of degree distribution and average degree are important parameters of networks, reflecting the performance of networks under target attack. Our results are helpful to the research on the security of network.

  18. Survey of Attacks on Mobile AdhocWireless Networks

    Directory of Open Access Journals (Sweden)

    Vikas Solomon Abel

    2011-02-01

    Full Text Available Security has always been a key issue with wireless networks since there are no physical boundaries. Experience has shown numerous vulnerabilities to a variety of attacks even when security measures are in place. In the combined Internet-MANET environment also security is an important issue keeping in view the Internet connectivity and attack on the MANET protocols.

  19. A Survey of Man in the Middle Attacks

    DEFF Research Database (Denmark)

    Conti, Mauro; Dragoni, Nicola; Lesyk, Viktor

    2016-01-01

    extensively review the literature on MITM to analyse and categorize the scope of MITM attacks, considering both a reference model, such as the open systems interconnection (OSI) model, as well as two specific widely used network technologies, i.e., GSM and UMTS. In particular, we classify MITM attacks based......The Man-In-The-Middle (MITM) attack is one of the most well known attacks in computer security, representing one of the biggest concerns for security professionals. MITM targets the actual data that flows between endpoints, and the confidentiality and integrity of the data itself. In this paper, we...... on several parameters, like location of an attacker in the network, nature of a communication channel, and impersonation techniques. Based on an impersonation techniques classification, we then provide execution steps for each MITM class. We survey existing countermeasures and discuss the comparison among...

  20. Comprehensive Study of Selective Forwarding Attack in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Wazir Zada Khan

    2011-02-01

    Full Text Available Sensor networks are becoming closer towards wide-spread deployment so security issues become a vital concern. Selective forwarding attack is one of the harmful attacks against sensor networks and can affect the whole sensor network communication. The variety of defense approaches against selective forwarding attack is overwhelming. In this paper we have described all the existing defensive schemes according to our best knowledge against this attack along with their drawbacks, thus providing researchers a better understanding of the attack and current solution space. This paper also classifies proposed schemes according to their nature and defense. Nature of scheme classifies into Distributed and Centralized. Defense of scheme classifies into detection and prevention.

  1. Impact of Multipath Routing on WSN Security Attacks

    Directory of Open Access Journals (Sweden)

    Koffka Khan

    2014-05-01

    Full Text Available Multipath routing does not minimize the consequences of security attacks. Due to this many WSNs are still in danger of most security attacks even when multipath routing is used. In critical situations, for example, in military and health applications this may lead to undesired, harmful and disastrous effects. These applications need to get their data communicated efficiently and in a secure manner. In this paper, we show the results of a series of security attacks on a multipath extension to the ad hoc on-demand distance vector AODV protocol, AOMDV. It is proved that many security parameters are negatively affected by security attacks on AOMDV, which is contradictory to research claims. This means that alternative refinements have to be made to present multipath routing protocols in order to make them more effective against network security attacks.

  2. The research of DPA attacks against AES implementations

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    This article examines vulnerabilities to power analysis attacks between software and hardware implementations of cryptographic algorithms. Representative platforms including an Atmel 89S8252 8-bit processor and a 0.25 μm 1.8 v standard cell circuit are proposed to implement the advance encryption standard (AES). A simulation-based experimental environment is built to acquire power data, and single-bit differential power analysis (DPA), and multi-bit DPA and correlation power analysis (CPA) attacks are conducted on two implementations respectively. The experimental results show that the hardware implementation has less data-dependent power leakages to resist power attacks. Furthermore, an improved DPA approach is proposed. It adopts hamming distance of intermediate results as power model and arranges plaintext inputs to differentiate power traces to the maximal probability. Compared with the original power attacks, our improved DPA performs a successful attack on AES hardware implementations with acceptable power measurements and fewer computations.

  3. Metrics for Assessment of Smart Grid Data Integrity Attacks

    Energy Technology Data Exchange (ETDEWEB)

    Annarita Giani; Miles McQueen; Russell Bent; Kameshwar Poolla; Mark Hinrichs

    2012-07-01

    There is an emerging consensus that the nation’s electricity grid is vulnerable to cyber attacks. This vulnerability arises from the increasing reliance on using remote measurements, transmitting them over legacy data networks to system operators who make critical decisions based on available data. Data integrity attacks are a class of cyber attacks that involve a compromise of information that is processed by the grid operator. This information can include meter readings of injected power at remote generators, power flows on transmission lines, and relay states. These data integrity attacks have consequences only when the system operator responds to compromised data by redispatching generation under normal or contingency protocols. These consequences include (a) financial losses from sub-optimal economic dispatch to service loads, (b) robustness/resiliency losses from placing the grid at operating points that are at greater risk from contingencies, and (c) systemic losses resulting from cascading failures induced by poor operational choices. This paper is focused on understanding the connections between grid operational procedures and cyber attacks. We first offer two examples to illustrate how data integrity attacks can cause economic and physical damage by misleading operators into taking inappropriate decisions. We then focus on unobservable data integrity attacks involving power meter data. These are coordinated attacks where the compromised data are consistent with the physics of power flow, and are therefore passed by any bad data detection algorithm. We develop metrics to assess the economic impact of these attacks under re-dispatch decisions using optimal power flow methods. These metrics can be use to prioritize the adoption of appropriate countermeasures including PMU placement, encryption, hardware upgrades, and advance attack detection algorithms.

  4. Serial analysis of gene expression predicts structural differences in hippocampus of long attack latency and short attack latency mice

    NARCIS (Netherlands)

    Feldker, DEM; Datson, NA; Veenema, AH; Meulmeester, E; de Kloet, ER; Vreugdenhil, E

    2003-01-01

    The genetically selected long attack latency (LAL) and short attack latency (SAL) mice differ in a wide variety of behavioural traits and display differences in the serotonergic system and the hypothalamus-pituitary-adrenocortical (HPA)-axis. Serial analysis of gene expression (SAGE) was used to gen

  5. Attack resilience of the evolving scientific collaboration network.

    Directory of Open Access Journals (Sweden)

    Xiao Fan Liu

    Full Text Available Stationary complex networks have been extensively studied in the last ten years. However, many natural systems are known to be continuously evolving at the local ("microscopic" level. Understanding the response to targeted attacks of an evolving network may shed light on both how to design robust systems and finding effective attack strategies. In this paper we study empirically the response to targeted attacks of the scientific collaboration networks. First we show that scientific collaboration network is a complex system which evolves intensively at the local level--fewer than 20% of scientific collaborations last more than one year. Then, we investigate the impact of the sudden death of eminent scientists on the evolution of the collaboration networks of their former collaborators. We observe in particular that the sudden death, which is equivalent to the removal of the center of the egocentric network of the eminent scientist, does not affect the topological evolution of the residual network. Nonetheless, removal of the eminent hub node is exactly the strategy one would adopt for an effective targeted attack on a stationary network. Hence, we use this evolving collaboration network as an experimental model for attack on an evolving complex network. We find that such attacks are ineffectual, and infer that the scientific collaboration network is the trace of knowledge propagation on a larger underlying social network. The redundancy of the underlying structure in fact acts as a protection mechanism against such network attacks.

  6. Personality characteristics of victims of illegal attacks on the Internet

    Directory of Open Access Journals (Sweden)

    Safuanov F.S.

    2016-01-01

    Full Text Available The article examines the personality characteristics of victims of illegal attacks on the Internet. We used methods as follow: 16 factors Cattell personality questionnaire, subjective control level, life-style index, Buss-Perry questionnaire, Spielberger State-Trait Anxiety Inventory, a COPE inventory. 78 internet users were divided into two groups of 38 persons: the main group included people falling victim to illegal attacks on the Internet, the control group participants were not attacked on the internet. We identified specific aggregated symptoms of individual psychological characteristics of internet attack victims and show that victims of "non-forced" and "forced" offenses have different levels of situational and personal anxiety, aggression and locus of control.

  7. A Survey of DDOS Attacks in TCP/IP Stack

    Directory of Open Access Journals (Sweden)

    P.C. Senthil Mahesh

    2014-08-01

    Full Text Available The aim of study is to discuss DDOS attack in TCP/IP layer. A Denial-of-Service (DoS or Distributed Denial-of-Service (DDoS attack is an attempt to make a device or network source not available to its designed customers. The purposes and objectives of a DoS attack may differ, it usually includes initiatives to momentarily or consistently disrupt or hold solutions of a variety linked with the Online. As explanation, DDoS (Distributed Denial of Service attack are sent by two or more individuals, or bots. DoS (Denial of Service attack are sent by one person or system. DoS attack typically focus on sites or solutions organized on high-profile web or web servers such as financial institutions, bank card payment gateways and even main name servers. This technique has now seen comprehensive use in certain activities, used by server owners, or dissatisfied opponents on activities. Progressively, DoS attack have also been used as a way of level of resistance.

  8. The LOCAL attack: Cryptanalysis of the authenticated encryption scheme ALE

    DEFF Research Database (Denmark)

    Khovratovich, Dmitry; Rechberger, Christian

    2014-01-01

    We show how to produce a forged (ciphertext, tag) pair for the scheme ALE with data and time complexity of 2102 ALE encryptions of short messages and the same number of authentication attempts. We use a differential attack based on a local collision, which exploits the availability of extracted...... state bytes to the adversary. Our approach allows for a time-data complexity tradeoff, with an extreme case of a forgery produced after 2119 attempts and based on a single authenticated message. Our attack is further turned into a state recovery and a universal forgery attack with a time complexity...

  9. Recurrence of Panic Attacks after Influenza Vaccination: Two Case Reports

    Science.gov (United States)

    Kim, Han-Joon; Jeon, Sang-Won; Yoon, Ho-Kyoung

    2016-01-01

    Human influenza is a contagious respiratory illness caused by the influenza virus. The influenza vaccination is recommended annually, but several adverse effects related to allergic reactions have been reported. Panic attacks are also known to occur, but no case of a panic attack adverse effect has been reported in South Korea. We present two cases of panic disorder patients whose symptoms were aggravated by the influenza vaccination. We assumed that dysregulation of T-lymphocytes in panic disorder patients could have a role in activating various kinds of cytokines and chemokines, which then can lead to panic attack aggravation. PMID:27776395

  10. Effect of Black Hole Attack on MANET Routing Protocols

    Directory of Open Access Journals (Sweden)

    Jaspal Kumar

    2013-04-01

    Full Text Available Due to the massive existing vulnerabilities in mobile ad-hoc networks, they may be insecure against attacks by the malicious nodes. In this paper we have analyzed the effects of Black hole attack on mobile ad hoc routing protocols. Mainly two protocols AODV and Improved AODV have been considered. Simulation has been performed on the basis of performance parameters and effect has been analyzed after adding Black-hole nodes in the network. Finally the results have been computed and compared to stumble on which protocol is least affected by these attacks.

  11. Compounding the Losses of Convoyed Ships Attacked by Tactical Submarines

    Directory of Open Access Journals (Sweden)

    Kåre M. Mjelde

    1982-10-01

    Full Text Available It is demonstrated that a time dependent stochastic model for the losses of convoyed ships attacked by submarines can be applied in the determination of the losses in terms of the results of two submodels:

  12. Enhancement of scale-free network attack tolerance

    Institute of Scientific and Technical Information of China (English)

    Qu Ze-Hui; Wang Pu; Song Chao-Ming; Qin Zhi-Guang

    2010-01-01

    Despite the large size of most communication and transportation systems, there are short paths between nodes in these networks which guarantee the efficient information, data and passenger delivery; furthermore these networks have a surprising tolerance under random errors thanks to their inherent scale-free topology. However, their scale-free topology also makes them fragile under intentional attacks, leaving us a challenge on how to improve the network robustness against intentional attacks without losing their strong tolerance under random errors and high message and passenger delivering capacity. Here we propose two methods (SL method and SH method) to enhance scale-free network's tolerance under attack in different conditions.

  13. For Heart Attack Survivors, a Risk of Suicide?

    Science.gov (United States)

    ... html For Heart Attack Survivors, a Risk of Suicide? Study findings underscore importance of depression screening, researcher ... may face a higher-than-normal risk of suicide, a new study suggests. Researchers in Taiwan found ...

  14. Performance Analysis of Black Hole Attack in Vanet

    Directory of Open Access Journals (Sweden)

    Vimal Bibhu

    2012-10-01

    Full Text Available Black hole attack in Vehicular Ad Hoc Network is major problem related with the field of computer networking. In this paper we present the performance analysis of the black hole attack in Vehicular Ad Hoc Network. We elaborate the different types of attacks and their depth in ad hoc network. The performance metric is taken for the evaluation of attack which depends on a packet end to end delay, network throughput and network load. The delay, throughput and load are simulated by the help of OPNET 14.5 modeler. The simulation setup comprises of 30 Vehicular nodes moving with constant speed of 10 meter per second. The data rate of Vehicular nodes is 11 Mbps with default transmitting power of 0.005 watts. With On Demand Distance Vector Routing and Optimized Link State Routing the malicious node buffer size is lowered to a level which increase packet drops.

  15. An Improvement of GNY Logic for the Reflection Attacks

    Institute of Scientific and Technical Information of China (English)

    DING Yiqiang

    1999-01-01

    In this paper, the limitation of the GNY logic about its inability to detect the reflection attacks againstsome authentication protocols is given. An improvement is proposed whichtakes into account the possible multiple instances (principals) of thesame identity in the model.

  16. Attack surfaces

    DEFF Research Database (Denmark)

    Gruschka, Nils; Jensen, Meiko

    2010-01-01

    The new paradigm of cloud computing poses severe security risks to its adopters. In order to cope with these risks, appropriate taxonomies and classification criteria for attacks on cloud computing are required. In this work-in-progress paper we present one such taxonomy based on the notion...... of attack surfaces of the cloud computing scenario participants. © 2010 IEEE....

  17. Fusion of Heterogeneous Intrusion Detection Systems for Network Attack Detection

    Directory of Open Access Journals (Sweden)

    Jayakumar Kaliappan

    2015-01-01

    Full Text Available An intrusion detection system (IDS helps to identify different types of attacks in general, and the detection rate will be higher for some specific category of attacks. This paper is designed on the idea that each IDS is efficient in detecting a specific type of attack. In proposed Multiple IDS Unit (MIU, there are five IDS units, and each IDS follows a unique algorithm to detect attacks. The feature selection is done with the help of genetic algorithm. The selected features of the input traffic are passed on to the MIU for processing. The decision from each IDS is termed as local decision. The fusion unit inside the MIU processes all the local decisions with the help of majority voting rule and makes the final decision. The proposed system shows a very good improvement in detection rate and reduces the false alarm rate.

  18. Heart Attack

    Science.gov (United States)

    ... a million people in the U.S. have a heart attack. About half of them die. Many people have permanent heart damage or die because they don't get ... It's important to know the symptoms of a heart attack and call 9-1-1 if someone ...

  19. Transcription and the Pitch Angle of DNA

    CERN Document Server

    Olsen, Kasper W

    2013-01-01

    The question of the value of the pitch angle of DNA is visited from the perspective of a geometrical analysis of transcription. It is suggested that for transcription to be possible, the pitch angle of B-DNA must be smaller than the angle of zero-twist. At the zero-twist angle the double helix is maximally rotated and its strain-twist coupling vanishes. A numerical estimate of the pitch angle for B-DNA based on differential geometry is compared with numbers obtained from existing empirical data. The crystallographic studies shows that the pitch angle is approximately 38 deg., less than the corresponding zero-twist angle of 41.8 deg., which is consistent with the suggested principle for transcription.

  20. Detecting Distributed Denial of Service Attacks Using Data Mining Techniques

    Directory of Open Access Journals (Sweden)

    Mouhammd Alkasassbeh

    2016-01-01

    Full Text Available Users and organizations find it continuously challenging to deal with distributed denial of service (DDoS attacks. . The security engineer works to keep a service available at all times by dealing with intruder attacks. The intrusion-detection system (IDS is one of the solutions to detecting and classifying any anomalous behavior. The IDS system should always be updated with the latest intruder attack deterrents to preserve the confidentiality, integrity and availability of the service. In this paper, a new dataset is collected because there were no common data sets that contain modern DDoS attacks in different network layers, such as (SIDDoS, HTTP Flood. This work incorporates three well-known classification techniques: Multilayer Perceptron (MLP, Naïve Bayes and Random Forest. The experimental results show that MLP achieved the highest accuracy rate (98.63%.

  1. Meningiomas of the cerebellopontine angle.

    Science.gov (United States)

    Matthies, C; Carvalho, G; Tatagiba, M; Lima, M; Samii, M

    1996-01-01

    Meningiomas of the cerebellopontine angle (CPA) represent a clinically and surgically interesting entity. The opportunity of complete surgical excision and the incidence of impairment of nerval structures largely depend on the tumour biology that either leads to displacement of surrounding structures by an expansive type of growth or to an enveloping of nerval and vascular structures by an en plaque type of growth. As the origin and the direction of growth are very variable, the exact tumour extension in relation to the nerval structures and the tumour origin can be identified sometimes only at the time of surgery. Out of a series of 230 meningiomas of the posterior skull base operated between 1978 and 1993, data of 134 meningiomas involving the cerebellopontine angle are presented. There were 20% male and 80% female patients, age at the time of surgery ranging from 18 to 76 years, on the average 51 years. The clinical presentation was characterized by a predominant disturbance of the cranial nerves V (19%), VII (11%), VIII (67%) and the caudal cranial nerves (6%) and signs of ataxia (28%). 80% of the meningiomas were larger than 30 mm in diameter, 53% led to evident brainstem compression or dislocation and 85% extended anteriorly to the internal auditory canal. Using the lateral suboccipital approach in the majority of cases and a combined presigmoidal or combined suboccipital and subtemporal approaches in either sequence in 5%, complete tumour removal (Simpson I and II) was accomplished in 95% and subtotal tumour removal in 5%. Histologically the meningiotheliomatous type was most common (49%) followed by the mixed type (19%), fibroblastic (16%), psammomatous (7%), hemangioblastic (7%) and anaplastic (2%) types. Major post-operative complications were CSF leakage (8%) requiring surgical revision in 2% and hemorrhage (3%) requiring revision in 2%. While the majority of neurological disturbances showed signs of recovery, facial nerve paresis or paralysis was

  2. Vulnerability of water supply systems to cyber-physical attacks

    Science.gov (United States)

    Galelli, Stefano; Taormina, Riccardo; Tippenhauer, Nils; Salomons, Elad; Ostfeld, Avi

    2016-04-01

    The adoption of smart meters, distributed sensor networks and industrial control systems has largely improved the level of service provided by modern water supply systems. Yet, the progressive computerization exposes these critical infrastructures to cyber-physical attacks, which are generally aimed at stealing critical information (cyber-espionage) or causing service disruption (denial-of-service). Recent statistics show that water and power utilities are undergoing frequent attacks - such as the December power outage in Ukraine - , attracting the interest of operators and security agencies. Taking the security of Water Distribution Networks (WDNs) as domain of study, our work seeks to characterize the vulnerability of WDNs to cyber-physical attacks, so as to conceive adequate defense mechanisms. We extend the functionality of EPANET, which models hydraulic and water quality processes in pressurized pipe networks, to include a cyber layer vulnerable to repeated attacks. Simulation results on a medium-scale network show that several hydraulic actuators (valves and pumps, for example) can be easily attacked, causing both service disruption - i.e., water spillage and loss of pressure - and structural damages - e.g., pipes burst. Our work highlights the need for adequate countermeasures, such as attacks detection and reactive control systems.

  3. Impact modeling and prediction of attacks on cyber targets

    Science.gov (United States)

    Khalili, Aram; Michalk, Brian; Alford, Lee; Henney, Chris; Gilbert, Logan

    2010-04-01

    In most organizations, IT (information technology) infrastructure exists to support the organization's mission. The threat of cyber attacks poses risks to this mission. Current network security research focuses on the threat of cyber attacks to the organization's IT infrastructure; however, the risks to the overall mission are rarely analyzed or formalized. This connection of IT infrastructure to the organization's mission is often neglected or carried out ad-hoc. Our work bridges this gap and introduces analyses and formalisms to help organizations understand the mission risks they face from cyber attacks. Modeling an organization's mission vulnerability to cyber attacks requires a description of the IT infrastructure (network model), the organization mission (business model), and how the mission relies on IT resources (correlation model). With this information, proper analysis can show which cyber resources are of tactical importance in a cyber attack, i.e., controlling them enables a large range of cyber attacks. Such analysis also reveals which IT resources contribute most to the organization's mission, i.e., lack of control over them gravely affects the mission. These results can then be used to formulate IT security strategies and explore their trade-offs, which leads to better incident response. This paper presents our methodology for encoding IT infrastructure, organization mission and correlations, our analysis framework, as well as initial experimental results and conclusions.

  4. Modeling Partial Attacks with Alloy (Transcript of Discussion)

    Science.gov (United States)

    Lin, Amerson

    The reason we went into this research, was that we found that partial attacks were extremely hard to model in terms of a language that could be used by an automated tool. Now there are three reasons why this is so. The first is that it is hard to identify these attacks even by hand, because you have to be really creative in thinking, what constitutes a reduction in entropy of the secret, that is significant, because a partial attack is really anything that reduces entropy, it's just that it does not reduce the entropy to zero, which would be a case of a complete attack. Next, it's hard to describe that in a formal language, part of that problem comes from the definition, you have to define what you want to be the goal, if the secret is the entire password, then getting one letter is pretty much a partial attack, but if the secret is that one letter, then getting that one letter is a complete attack. And lastly, applying that logic, how do you measure entropy, how do you measure information leakage, that's also very difficult.

  5. Impact of Degree Heterogeneity on Attack Vulnerability of Interdependent Networks

    Science.gov (United States)

    Sun, Shiwen; Wu, Yafang; Ma, Yilin; Wang, Li; Gao, Zhongke; Xia, Chengyi

    2016-09-01

    The study of interdependent networks has become a new research focus in recent years. We focus on one fundamental property of interdependent networks: vulnerability. Previous studies mainly focused on the impact of topological properties upon interdependent networks under random attacks, the effect of degree heterogeneity on structural vulnerability of interdependent networks under intentional attacks, however, is still unexplored. In order to deeply understand the role of degree distribution and in particular degree heterogeneity, we construct an interdependent system model which consists of two networks whose extent of degree heterogeneity can be controlled simultaneously by a tuning parameter. Meanwhile, a new quantity, which can better measure the performance of interdependent networks after attack, is proposed. Numerical simulation results demonstrate that degree heterogeneity can significantly increase the vulnerability of both single and interdependent networks. Moreover, it is found that interdependent links between two networks make the entire system much more fragile to attacks. Enhancing coupling strength between networks can greatly increase the fragility of both networks against targeted attacks, which is most evident under the case of max-max assortative coupling. Current results can help to deepen the understanding of structural complexity of complex real-world systems.

  6. Generating IDS Attack Pattern Automatically Based on Attack Tree

    Institute of Scientific and Technical Information of China (English)

    向尕; 曹元大

    2003-01-01

    Generating attack pattern automatically based on attack tree is studied. The extending definition of attack tree is proposed. And the algorithm of generating attack tree is presented. The method of generating attack pattern automatically based on attack tree is shown, which is tested by concrete attack instances. The results show that the algorithm is effective and efficient. In doing so, the efficiency of generating attack pattern is improved and the attack trees can be reused.

  7. The attack navigator

    DEFF Research Database (Denmark)

    Probst, Christian W.; Willemson, Jan; Pieters, Wolter

    2016-01-01

    -technical system, the attack navigator identifies routes to an attacker goal. Specific attacker properties such as skill or resources can be included through attacker profiles. This enables defenders to explore attack scenarios and the effectiveness of defense alternatives under different threat conditions....

  8. Factors governing risk of cougar attacks on humans

    Science.gov (United States)

    Mattson, David; Logan, Kenneth; Sweanor, Linda

    2011-01-01

    Since the 1980s wildlife managers in the United States and Canada have expressed increasing concern about the physical threat posed by cougars (Puma concolor) to humans. We developed a conceptual framework and analyzed 386 human–cougar encounters (29 fatal attacks, 171 instances of nonfatal contact, and 186 close-threatening encounters) to provide information relevant to public safety. We conceived of human injury and death as the outcome of 4 transitions affected by different suites of factors: (1) a human encountering a cougar: (2) given an encounter, odds that the cougar would be aggressive; (3) given aggression, odds that the cougar would attack; and (4) given an attack, odds that the human would die. We developed multivariable logistic regression models to explain variation in odds at transitions three and four using variables pertaining to characteristics of involved people and cougars. Young (≤ 2.5 years) or unhealthy (by weight, condition, or disease) cougars were more likely than any others to be involved in close (typically females were more likely than males to attack, and of attacking animals, adults were more likely than juveniles to kill the victim (32% versus 9% fatality, respectively). During close encounters, victims who used a weapon killed the involved cougar in 82% of cases. Other mitigating behaviors (e.g., yelling, backing away, throwing objects, increasing stature) also substantially lessened odds of attack. People who were moving quickly or erratically when an encounter happened (running, playing, skiing, snowshoeing, biking, ATV-riding) were more likely to be attacked and killed compared to people who were less active (25% versus 8% fatality). Children (≤ 10 years) were more likely than single adults to be attacked, but intervention by people of any age reduced odds of a child’s death by 4.6×. Overall, cougar attacks on people in Canada and the United States were rare (currently 4 to 6/year) compared to attacks by large felids and

  9. A Strategic Analysis of Information Sharing Among Cyber Attackers

    Directory of Open Access Journals (Sweden)

    Kjell Hausken

    2015-10-01

    Full Text Available We build a game theory model where the market design is such that one firm invests in security to defend against cyber attacks by two hackers. The firm has an asset, which is allocated between the three market participants dependent on their contest success. Each hacker chooses an optimal attack, and they share information with each other about the firm’s vulnerabilities. Each hacker prefers to receive information, but delivering information gives competitive advantage to the other hacker. We find that each hacker’s attack and information sharing are strategic complements while one hacker’s attack and the other hacker’s information sharing are strategic substitutes. As the firm’s unit defense cost increases, the attack is inverse U-shaped and reaches zero, while the firm’s defense and profit decrease, and the hackers’ information sharing and profit increase. The firm’s profit increases in the hackers’ unit cost of attack, while the hackers’ information sharing and profit decrease. Our analysis also reveals the interesting result that the cumulative attack level of the hackers is not affected by the effectiveness of information sharing between them and moreover, is also unaffected by the intensity of joint information sharing. We also find that as the effectiveness of information sharing between hackers increases relative to the investment in attack, the firm’s investment in cyber security defense and profit are constant, the hackers’ investments in attacks decrease, and information sharing levels and hacker profits increase. In contrast, as the intensity of joint information sharing increases, while the firm’s investment in cyber security defense and profit remain constant, the hackers’ investments in attacks increase, and the hackers’ information sharing levels and profits decrease. Increasing the firm’s asset causes all the variables to increase linearly, except information sharing which is constant. We extend

  10. Formalized Description of Distributed Denial of Service Attack

    Institute of Scientific and Technical Information of China (English)

    杜彦辉; 马锐; 刘玉树

    2004-01-01

    The distributed denial of service (DDoS) attack is one of the dangers in intrusion modes. It's difficult to defense and can cause serious damage to the system. Based on a careful study of the attack principles and characteristics, an object-oriented formalized description is presented, which contains a three-level framework and offers full specifications of all kinds of DDoS modes and their features and the relations between one another. Its greatest merit lies in that it contributes to analyzing, checking and judging DDoS. Now this formalized description has been used in a special IDS and it works very effectively.

  11. A Comparison of Link Layer Attacks on Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Shahriar Mohammadi

    2011-03-01

    Full Text Available Wireless sensor networks (WSNs have many potential applications [1, 5] and unique challenges. Theyusually consist of hundreds or thousands small sensor nodes such as MICA2, which operateautonomously; conditions such as cost, invisible deployment and many application domains, lead to smallsize and limited resources sensors [2]. WSNs are susceptible to many types of link layer attacks [1] andmost of traditional networks security techniques are unusable on WSNs [2]; due to wireless and sharednature of communication channel, untrusted transmissions, deployment in open environments, unattendednature and limited resources [1]. So, security is a vital requirement for these networks; but we have todesign a proper security mechanism that attends to WSN's constraints and requirements. In this paper, wefocus on security of WSNs, divide it (the WSNs security into four categories and will consider them,include: an overview of WSNs, security in WSNs, the threat model on WSNs, a wide variety of WSNs' linklayer attacks and a comparison of them. This work enables us to identify the purpose and capabilities ofthe attackers; also, the goal and effects of the link layer attacks on WSNs are introduced. Also, this paperdiscusses known approaches of security detection and defensive mechanisms against the link layerattacks; this would enable it security managers to manage the link layer attacks of WSNs more effectively

  12. Robustness of controllability for networks based on edge-attack.

    Directory of Open Access Journals (Sweden)

    Sen Nie

    Full Text Available We study the controllability of networks in the process of cascading failures under two different attacking strategies, random and intentional attack, respectively. For the highest-load edge attack, it is found that the controllability of Erdős-Rényi network, that with moderate average degree, is less robust, whereas the Scale-free network with moderate power-law exponent shows strong robustness of controllability under the same attack strategy. The vulnerability of controllability under random and intentional attacks behave differently with the increasing of removal fraction, especially, we find that the robustness of control has important role in cascades for large removal fraction. The simulation results show that for Scale-free networks with various power-law exponents, the network has larger scale of cascades do not mean that there will be more increments of driver nodes. Meanwhile, the number of driver nodes in cascading failures is also related to the edges amount in strongly connected components.

  13. Performance Comparison of Routing Attacks in Manet and WSN

    Directory of Open Access Journals (Sweden)

    Shyamala Ramachandran

    2012-08-01

    Full Text Available Routing is a basic step for data exchange. In wirel ess ad-hoc networks each node acts as a router and executes a routing protocol. Wireless ad-hoc networ ks are highly resource constrained in terms of network topology, memory and computation power. The reliable data transfer is a difficult task in wireless ad-hoc networks because of resource constr aints. A mobile ad-hoc network (MANET is a kind of wireless ad-hoc network, and is a self-configuri ng network of mobile routers connected by wireless links. A wireless sensor network (WSN is a highly constrained wireless ad-hoc network. In these network, multicast is the efficient routing service for data broadcasting. Denial of service (DOS att ack, sinkhole, wormhole, sybil, black hole and rushing a ttacks are some routing attacks. So, it is necessar y to study the impact of routing attacks on existing mul ticast routing protocols to suggest a suitable secu re multicast routing protocol. The objective of this p aper is to study the effects of black hole and rush ing attack on MANET and WSN. The NS-2 based simulation is used in analyzing the black hole and rushing attacks. From performance metrics such as packet de livery ratio (PDR, packet drop ratio (PDrR, network throughput (NTh and energy consumption it is observed that the routing attacks have severe impact on MANET than WSN.

  14. The Rebound Attack: Cryptanalysis of Reduced Whirlpool and Grøstl

    DEFF Research Database (Denmark)

    Mendel, Florian; Rechberger, Christian; Schläffer, Martin;

    2009-01-01

    In this work, we propose the rebound attack, a new tool for the cryptanalysis of hash functions. The idea of the rebound attack is to use the available degrees of freedom in a collision attack to efficiently bypass the low probability parts of a differential trail. The rebound attack consists of ...

  15. INTRA-SNAIL LIDOCAIN FOR TREATMENT OF MIGRAINE ATTACK

    Institute of Scientific and Technical Information of China (English)

    Qu Songbin; Wang Xiaofeng

    2000-01-01

    OBJECTIVE To explore a mcthod of trcating migraine attack. BACKROUND Migraine is the most common disorder which causcs .severe headache, nausea and vomiting in attack continuing several hours. There is little method to cease migraine attack quickly. METHOD The patients lied down and kept the head backward. Lidocain 2% 1 to 2 ml was slowly instilled into the nostril ipsilatcral to thc headache. RESULTS Pain relief was achievcd in minutes. The headache disappeared in 19 cases and slight headache rcmained in 2 cases mong 21 cascs. TCD (transcranial dopple ) was tested in 6 cases before thc treatment and 5 minutes after thc treatment. The results showed that CBF (cerebral blood flow) velocity diminished before thc treatment and increased to normal value after the treatment in 5 cases, and it increased beforc thc treatment in another case and diminished after the treatment. DISSCUSION Thc migraine attacks are associated with dysfunction of the vascular constriction and vasodilatation. It was reported that Lidocain had diplex effect that induce the vascular constriction and also induce vasodilatation on the bases of regulation of the autonomic nerves. Medications to abort the attack dramatically by the transnasal route.. CONCLUSION This method is casy to use, painless and effective.

  16. Vulnerability of complex networks under three-level-tree attacks

    Science.gov (United States)

    Hao, Yao-hui; Han, Ji-hong; Lin, Yi; Liu, Lin

    2016-11-01

    We investigate vulnerability of complex networks including model networks and real world networks subject to three-level-tree attack. Specifically, we remove three different three-level-tree structures: RRN (Random Root Node), MaxDRN (Max Degree Root Node) and MinDRN (Min Degree Root Node) from a network iteratively until there is no three-level-tree left. Results demonstrate that random network is more robust than scale-free network against three tree attacks, and the robustness of random network decreases as the increases. And scale-free network shows different characteristics in different tree attack modes. The robustness of scale-free is not affected by the parameters for RRN, but increases as the increases for MinDRN. The important thing is that MaxDRN is the most effective in the three tree attack modes, especially for scale-free network. These findings supplement and extend the previous attack results on nodes and edges, and can thus help us better explain the vulnerability of different networks, and provide an insight into more tolerant real complex systems design.

  17. Detection of Attacks on MAODV Association Rule Mining Optimization

    Directory of Open Access Journals (Sweden)

    A. Fidalcastro

    2015-02-01

    Full Text Available Current mining algorithms can generate large number of rules and very slow to generate rules or generate few results, omitting interesting and valuable information. To address this problem, we propose an algorithm Optimized Featured Top Association Rules (OFTAR algorithm, where every attack have many features and some of the features are more important. The Features are selected by genetic algorithm and processed by the OFTAR algorithm to find the optimized rules. The algorithm utilizes Genetic Algorithm feature selection approach to find optimized features. OFTAR incorporate association rules with several rule optimization techniques and expansion techniques to improve efficiency. Increasing popularity of Mobile ad hoc network users of wireless networks lead to threats and attacks on MANET, due to its features. The main challenge in designing a MANET is protecting from various attacks in the network. Intrusion Detection System is required to monitor the network and to detect the malicious node in the network in multi casting mobility environment. The node features are processed in Association Analysis to generate rules, the generated rules are applied to nodes to detect the attacks. Experimental results show that the algorithm has higher scalability and good performance that is an advantageous to several association rule mining algorithms when the rule generation is controlled and optimized to detect the attacks.

  18. Matrix metalloproteinases during and outside of migraine attacks without aura

    DEFF Research Database (Denmark)

    Ashina, M.; Tvedskov, J.F.; Thiesen, Kerstin Lipka

    2010-01-01

    Ashina M, Tvedskov JF, Lipka K, Bilello J, Penkowa M & Olesen J. Matrix metalloproteinases during and outside of migraine attacks without aura. Cephalalgia 2009. London. ISSN 0333-1024To test the hypothesis that permeability of the blood-brain barrier (BBB) is altered during migraine attack due...... to enhanced activation of matrix metalloproteinases (MMPs), we investigated MMP-3, MMP-9 and tissue inhibitor of metalloproteases (TIMP)-1 in the external jugular vein during and outside of migraine attacks in 21 patients with migraine without aura. In addition, we measured plasma levels of several other...... and interictal plasma levels of MMP-7, -8, -10 and TIMP-2 (P > 0.05). Our data suggest that plasma MMP-9 cannot be used as a biomarker of BBB disruption in migraine without aura. Decreased MMP-3 levels are an interesting and unexpected finding warranting further investigation....

  19. A Case Of Transient Ischemic Attack Presenting As Hemichroea

    Directory of Open Access Journals (Sweden)

    Hasan Hüseyin Özdemir

    2013-12-01

    Full Text Available Chorea is defined as; involuntary movements of the distal parts of limbs which have arrhythmic, rapid, bouncing or smooth, simple or complex properties. Choreiform movements occur when putamen, globus pallidus and subthalamic nucleus are affected. Chorea can be observed during the course of metabolic and vascular diseases, neurodegenerative or hereditary diseases. Chorea may be a rare symptom of cerebral hypoperfusion. Transient ischemic attack is an event that occurs in short term characterized by a temporary ischemia of brain. A wide variety of symptoms can be seen depending on the localization of cerebral hypoperfusion. Hemichorea is a very rare finding observed during transient ischemic attacks. In this article hemichorea in a case of symptomatic transient ischemic attack is discussed with relevant literature.

  20. Method of Preventing Buffer Overflow Attacks by Intercepting DLL Functions

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    The way of intercepting Windows DLL functions against buffer overflow attacks is evaluated. It's produced at the expense of hooking vulnerable DLL functions by addition of check code. If the return address in the stack belongs to a heap or stack page, the call is from illicit code and the program is terminated. The signature of malicious code is recorded, so it is possible for the next attack to be filtered out. The return-into-libc attacks are detected by comparing the entry address of DLL functions with the overwritten return address in the stack. The presented method interrupts the execution of malicious code and prevents the system from being hijacked when these intercepted DLL functions are invoked in the context of buffer overflow.

  1. A video-polygraphic analysis of the cataplectic attack

    DEFF Research Database (Denmark)

    Rubboli, G; d'Orsi, G; Zaniboni, A

    2000-01-01

    with bradycardia, that was maximal during the atonic phase. CONCLUSIONS: Analysis of the muscular phenomena that characterize cataplectic attacks in a standing patient suggests that the cataplectic fall occurs with a pattern that might result from the interaction between neuronal networks mediating muscular atonia......OBJECTIVES AND METHODS: To perform a video-polygraphic analysis of 11 cataplectic attacks in a 39-year-old narcoleptic patient, correlating clinical manifestations with polygraphic findings. Polygraphic recordings monitored EEG, EMG activity from several cranial, trunk, upper and lower limbs...... muscles, eye movements, EKG, thoracic respiration. RESULTS: Eleven attacks were recorded, all of them lasting less than 1 min and ending with the fall of the patient to the ground. We identified, based on the video-polygraphic analysis of the episodes, 3 phases: initial phase, characterized essentially...

  2. Identifying optimal targets of network attack by belief propagation

    CERN Document Server

    Mugisha, Salomon

    2016-01-01

    For a network formed by nodes and undirected links between pairs of nodes, the network optimal attack problem aims at deleting a minimum number of target nodes to break the network down into many small components. This problem is intrinsically related to the feedback vertex set problem that was successfully tackled by spin glass theory and an associated belief propagation-guided decimation (BPD) algorithm [H.-J. Zhou, Eur.~Phys.~J.~B 86 (2013), 455]. In the present work we apply a slightly adjusted version of the BPD algorithm to the network optimal attack problem, and demonstrate that it has much better performance than a recently proposed Collective Information algorithm [F. Morone and H. A. Makse, Nature 524 (2015), 63--68] for different types of random networks and real-world network instances. The BPD-guided attack scheme often induces an abrupt collapse of the whole network, which may make it very difficult to defend.

  3. Resistance to Statistical Attacks of Parastrophic Quasigroup Transformation

    Directory of Open Access Journals (Sweden)

    Verica Bakeva

    2015-09-01

    Full Text Available The resistance to statistical kind of attacks of encrypted messages is a very important property for designing cryptographic primitives. In this paper, the parastrophic quasigroup PE-transformation, proposed elsewhere, is considered and the proof that it has this cryptographic property is given. Namely, it is proven that if PE-transformation is used for design of an encryption function then after n applications of it on arbitrary message the distribution of m-tuples (m = 1; 2; : : : ; n is uniform. These uniform distributions imply the resistance to statistical attack of the encrypted messages. For illustration of theoretical results, some experimental results are presented as well.

  4. [The hospital care of victims of terrorist attacks].

    Science.gov (United States)

    Bouhaddou, Assena; Nion, Nathalie; Riou, Bruno; Blandeau, Fanny; Moreau, Pilar; Guemache, Sofia

    2017-04-01

    The treatment of victims of terrorist attacks in a trauma centre requires the putting in place of plans, training and simulation exercises. Previous experiences have highlighted the areas which require improvement. As exceptional health situations are unpredictable, it is essential to always be vigilant and prepared for an unforeseen event.

  5. Computing Preferred Extensions for Argumentation Systems with Sets of Attacking

    DEFF Research Database (Denmark)

    Nielsen, Søren Holbech; Parsons, Simon

    2006-01-01

    The hitherto most abstract, and hence general, argumentation system, is the one described by Dung in a paper from 1995. This framework does not allow for joint attacks on arguments, but in a recent paper we adapted it to support such attacks, and proved that this adapted framework enjoyed the same...... formal properties as that of Dung. One problem posed by Dung's original framework, which was neglected for some time, is how to compute preferred extensions of the argumentation systems. However, in 2001, in a paper by Doutre and Mengin, a procedure was given for enumerating preferred extensions...... for these systems. In this paper we propose a method for enumerating preferred extensions of the potentially more complex systems, where joint attacks are allowed. The method is inspired by the one given by Doutre and Mengin....

  6. An Assessment of Worm Hole attack over Mobile Ad-Hoc Network as serious threats

    Directory of Open Access Journals (Sweden)

    Vikas Kumar Upadhyay

    2013-07-01

    Full Text Available Now these day Mobile Ad hoc networks vulnerable from number of security threats like black hole attack, DOS attack, Byzantine attack and wormhole attack. Wormhole attack is one of most important attack and having great attention in recent year. Wormhole attack, demonstrate a illusion over the network that show two far away node to be an neighbor node and attracted all traffic by presenting an greediness of shortest path over the network. This paper presents a bird eye over different existing wormhole deduction mechanism and their problem.

  7. Attacks to Cryptography Protocols of Wireless Industrial Communication Systems

    Directory of Open Access Journals (Sweden)

    Tomas Ondrasina

    2010-01-01

    Full Text Available The paper deals with problems of safety and security principles within wireless industrial communication systems. First safety requirements to wireless industrial communication system, summarisation of attack methods and the available measures for risks elimination are described with orientation to safety critical applications. The mainly part is oriented to identification of risks and summarisation of defensive methods of wireless communication based on cryptographic techniques. Practical part the cryptoanalytic’s attacks to COTS (Commercial Off-The-Shelf wireless communications are mentioned based on the IEEE 802.11 standards.

  8. An ensemble approach for feature selection of Cyber Attack Dataset

    CERN Document Server

    Singh, Shailendra

    2009-01-01

    Feature selection is an indispensable preprocessing step when mining huge datasets that can significantly improve the overall system performance. Therefore in this paper we focus on a hybrid approach of feature selection. This method falls into two phases. The filter phase select the features with highest information gain and guides the initialization of search process for wrapper phase whose output the final feature subset. The final feature subsets are passed through the Knearest neighbor classifier for classification of attacks. The effectiveness of this algorithm is demonstrated on DARPA KDDCUP99 cyber attack dataset.

  9. A 3-Subset Meet-in-the-Middle Attack: Cryptanalysis of the Lightweight Block Cipher KTANTAN

    DEFF Research Database (Denmark)

    Bogdanov, Andrey; Rechberger, Christian

    2011-01-01

    In this paper we describe a variant of existing meet-in-the-middle attacks on block ciphers. As an application, we propose meet-in-the-middle attacks that are applicable to the KTANTAN family of block ciphers accepting a key of 80 bits. The attacks are due to sonic weaknesses in its bitwise key s...... requirements, these attacks are valid even in RFID-like environments where only a very limited amount of text material may be available to an attacker....

  10. Multi-Level Parsing Based Approach Against Phishing Attacks With the Help of Knowledge Bases

    OpenAIRE

    2013-01-01

    The increasing use of internet all over the world,be it in households or in corporate firms, has ledto anunprecedented rise in cyber-crimes. Amongst these the major chunk consists of Internet attacks which arethe most popular and common attacks are carried over the internet. Generally phishing attacks, SSLattacks and some other hacking attacks are kept into this category. Security against these attacks isthemajor issue of internet security in today’s scenario where internet has very deep pene...

  11. Contact angle hysteresis of microbead suspensions.

    Science.gov (United States)

    Waghmare, Prashant R; Mitra, Sushanta K

    2010-11-16

    Microbead suspensions are often used in microfluidic devices for transporting biomolecules. An experimental investigation on the wettability of microbead suspension is presented in this study. The variation in the surface tension and the equilibrium contact angle with the change in the volume fraction of the microbead is presented here. The surface tension of the microbead suspension is measured with the pendant drop technique, whereas the dynamic contact angle measurements, i.e., advancing and receding contact angles, are measured with the sessile drop technique. An equilibrium contact angle of a suspension with particular volume fraction is determined by computing an average over the measured advancing and receding contact angles. It is observed that the surface tension and the equilibrium contact angle determined from advancing and receding contact angles vary with the magnitude of the microbeads volume fraction in the suspension. A decrease in the surface tension with an increase in the volume fraction of the microbead suspension is observed. The advancement and the recession in contact line for dynamic contact angle measurements are achieved with the motorized dosing mechanism. For microbead suspensions, the advancement of the contact line is faster as compared to the recession of the contact line for the same flow rate. The presence of microbeads assists in the advancement and the recession of the contact line of the suspension. A decrease in the equilibrium contact angles with an increase in the microbead suspension volume fraction is observed. Inclusion of microbeads in the suspension increases the wetting capability for the considered combination of the microbead suspension and substrate. Finally, empirical correlations for the surface tension and the contact angle of the suspension as a function of microbead volume fraction are proposed. Such correlations can readily be used to develop mechanistic models for the capillary transport of microbead

  12. Reliable measurement of the receding contact angle.

    Science.gov (United States)

    Korhonen, Juuso T; Huhtamäki, Tommi; Ikkala, Olli; Ras, Robin H A

    2013-03-26

    Surface wettability is usually evaluated by the contact angle between the perimeter of a water drop and the surface. However, this single measurement is not enough for proper characterization, and the so-called advancing and receding contact angles also need to be measured. Measuring the receding contact angle can be challenging, especially for extremely hydrophobic surfaces. We demonstrate a reliable procedure by using the common needle-in-the-sessile-drop method. Generally, the contact line movement needs to be followed, and true receding movement has to be distinguished from "pseudo-movement" occurring before the receding angle is reached. Depending on the contact angle hysteresis, the initial size of the drop may need to be surprisingly large to achieve a reliable result. Although our motivation for this work was the characterization of superhydrophobic surfaces, we also show that this method works universally ranging from hydrophilic to superhydrophobic surfaces.

  13. ATTACK ON WATER BY CARBON OF SOLID FUEL

    Directory of Open Access Journals (Sweden)

    N. S. Nazarov

    2008-01-01

    Full Text Available The paper considers a continuous method for attack of high temperature water steam by carbon of solid fuel (coke. Design of water-coal gas generator and experimental stand, methodology for  measurements of parameters of water-coal gasification are described in the paper.

  14. The Attacks of September 11 in Three Temporalities

    Directory of Open Access Journals (Sweden)

    Steven Sherman

    2015-08-01

    Full Text Available The attacks of September 11 are explored from the perspective of three temporalities—that of US hegemony (roughly the last 50 years, that of the history of modernity (roughly the last three hundred and ?fty years and that of the ‘clash’ between Western and non–Western civilizations (roughly the last one thousand years. The attacks are symptomatic of the emergence of regional, networked actors that the US is not well prepared to address and which disrupt the national–developmental world order organized under US hegemony. By demonstrating one of the unintended consequences of modernity—the democratization of means of destruction—the attacks mark another nail in the co?n of the idea that progress can be attained through technological breakthroughs and the rational organization of the world (which we call hegemonic rationalistic modernity. The attempt to galvanize the Islamic community through an assault on its perceived rivals parallels the strategy of the Christian crusades 1000 years ago. The attacks mark a moment in the declining ability of the West to control the non–Western world. In conclusion, world order is likely to be reconstructed only if there is a move beyond US hegemony, rationalistic modernity, and the presumption of Western supremacy that characterize the contemporary world.

  15. The Spatial and Temporal Patterns of Insurgent Attacks

    Science.gov (United States)

    2014-06-13

    decision making of criminology scholarship to predict why attacks occur within space and time. The significance of this proposal is important to...environment. I propose a theoretical construct that combines the systematic analysis of Kalyvas with the individual decision making of criminology ...

  16. Controlling The Spread of Land-Attack Cruise Missiles.

    Science.gov (United States)

    2007-11-02

    Debate in the ’New’ European Community," Arms Control Today 23, no. 2 (March 1993): 12. 38 Controlling the Spread of Land-Attack Cruise Missiles...of temperature, pressures or atmosphere in autoclaves or hydro- claves when used for the production of composites or partially processed composites

  17. Extracranial arterial aneurysms: a cause of crescendo transient ischaemic attacks.

    Science.gov (United States)

    Paterson, H M; Holdsworth, R J

    2000-12-01

    Crescendo transient ischaemic attacks (TIAs) should be regarded as a medical emergency. Patients require hospitalisation with urgent assessment and symptom control with anticoagulant therapy. We report on three patients, all of whom had atherosclerotic aneurysmal disease of the extracranial arterial circulation who presented with crescendo TIAs. The possibility of extracranial aneurysmal disease should always be considered and excluded.

  18. Vulnerabilities in GSM technology and feasibility of selected attacks

    Science.gov (United States)

    Voznak, M.; Prokes, M.; Sevcik, L.; Frnda, J.; Toral-Cruz, Homer; Jakovlev, Sergej; Fazio, Peppino; Mehic, M.; Mikulec, M.

    2015-05-01

    Global System for Mobile communication (GSM) is the most widespread technology for mobile communications in the world and serving over 7 billion users. Since first publication of system documentation there has been notified a potential safety problem's occurrence. Selected types of attacks, based on the analysis of the technical feasibility and the degree of risk of these weaknesses, were implemented and demonstrated in laboratory of the VSB-Technical University of Ostrava, Czech Republic. These vulnerabilities were analyzed and afterwards possible attacks were described. These attacks were implemented using open-source tools, software programmable radio USRP (Universal Software RadioPeripheral) and DVB-T (Digital Video Broadcasting - Terrestrial) receiver. GSM security architecture is being scrutinized since first public releases of its specification mainly pointing out weaknesses in authentication and ciphering mechanisms. This contribution also summarizes practically proofed and used scenarios that are performed using opensource software tools and variety of scripts mostly written in Python. Main goal of this paper is in analyzing security issues in GSM network and practical demonstration of selected attacks.

  19. Prevention of Co-operative Black Hole Attack in MANET

    Directory of Open Access Journals (Sweden)

    Latha Tamilselvan

    2008-05-01

    Full Text Available A mobile ad hoc network (MANET is an autonomous network that consists of mobile nodes that communicate with each other over wireless links. In the absence of a fixed infrastructure, nodes have to cooperate in order to provide the necessary network functionality. One of the principal routing protocols used in Ad hoc networks is AODV (Ad hoc On demand Distance Vector protocol. The security of the AODV protocol is compromised by a particular type of attack called ‘Black Hole’ attack In this attack a malicious node advertises itself as having the shortest path to the node whose packets it wants to intercept. To reduce the probability it is proposed to wait and check the replies from all the neighboring nodes to find a safe route. Our approach to combat the Black hole attack is to make use of a ‘Fidelity Table’ wherein every participating node will be assigned a fidelity level that acts as a measure of reliability of that node. In case the level of any node drops to 0, it is considered to be a malicious node, termed as a ‘Black hole’ and is eliminated. Computer simulation using GLOMOSIM shows that our protocol provides better security and also better performance in terms of packet delivery than the conventional AODV in the presence of Black holes with minimal additional delay and Overhead.

  20. Globographic visualisation of three dimensional joint angles.

    Science.gov (United States)

    Baker, Richard

    2011-07-07

    Three different methods for describing three dimensional joint angles are commonly used in biomechanics. The joint coordinate system and Cardan/Euler angles are conceptually quite different but are known to represent the same underlying mathematics. More recently the globographic method has been suggested as an alternative and this has proved particularly attractive for the shoulder joint. All three methods can be implemented in a number of ways leading to a choice of angle definitions. Very recently Rab has demonstrated that the globographic method is equivalent to one implementation of the joint coordinate system. This paper presents a rigorous analysis of the three different methods and proves their mathematical equivalence. The well known sequence dependence of Cardan/Euler is presented as equivalent to configuration dependence of the joint coordinate system and orientation dependence of globographic angles. The precise definition of different angle sets can be easily visualised using the globographic method using analogues of longitude, latitude and surface bearings with which most users will already be familiar. The method implicitly requires one axis of the moving segment to be identified as its principal axis and this can be extremely useful in helping define the most appropriate angle set to describe the orientation of any particular joint. Using this technique different angle sets are considered to be most appropriate for different joints and examples of this for the hip, knee, ankle, pelvis and axial skeleton are outlined.

  1. Impact of migraine attacks on the blood-brain barrier

    Institute of Scientific and Technical Information of China (English)

    GAO Hong-mei; LI Le; ZHANG Ke-ling; CHEN Xu-hui; TIAN Shu-qing; ZHANG Zhong-ling

    2010-01-01

    Background Cortical spreading depression can cause migraine attack, and up-regulate matrix metalloproteinase-9 (MMP-9) expression in animal. This study aimed to determine the impact on the structure and function of the blood-brain barrier by measuring plasma MMP-9 levels in patients at the acute and late stages of migraine attacks in order to elucidate the pathological mechanisms involved.Methods We recruited a case-control cohort of 38 adult migraine patients and 20 age- and gender-matched healthy control subjects. Five milliliter blood samples were collected at the acute and late stages of migraine (days 1-7), and also from the control subjects. Solid phase double antibody sandwich enzyme-linked immunosorbent assay was used to determine plasma MMP-9 levels. Statistical analysis was performed using the SAS version 9.1.Results Initial plasma MMP-9 levels of migraine patients were significantly higher than those of controls ((12.612±0.016)μg/L vs. (6.069±0.023) μg/L, respectively, P 0.05); in addition, levels were not correlated with degree of headache pain (P >0.05).Conclusions We hypothesize that migraine could lead to increased plasma MMP-9 levels resulting in blood-brain barrier damage. MMP-9 levels increase during days 1-6 of migraine attacks, peaking on day 3. Therefore, MMP-9 could be used as a biological marker to guide treatment of migraine attacks.

  2. Modelling Based Approach for Reconstructing Evidence of VOIP Malicious Attacks

    Directory of Open Access Journals (Sweden)

    Mohammed Ibrahim

    2015-05-01

    Full Text Available Voice over Internet Protocol (VoIP is a new communication technology that uses internet protocol in providing phone services. VoIP provides various forms of benefits such as low monthly fee and cheaper rate in terms of long distance and international calls. However, VoIP is accompanied with novel security threats. Criminals often take advantages of such security threats and commit illicit activities. These activities require digital forensic experts to acquire, analyses, reconstruct and provide digital evidence. Meanwhile, there are various methodologies and models proposed in detecting, analysing and providing digital evidence in VoIP forensic. However, at the time of writing this paper, there is no model formalized for the reconstruction of VoIP malicious attacks. Reconstruction of attack scenario is an important technique in exposing the unknown criminal acts. Hence, this paper will strive in addressing that gap. We propose a model for reconstructing VoIP malicious attacks. To achieve that, a formal logic approach called Secure Temporal Logic of Action(S-TLA+ was adopted in rebuilding the attack scenario. The expected result of this model is to generate additional related evidences and their consistency with the existing evidences can be determined by means of S-TLA+ model checker.

  3. Parent-Reported Predictors of Adolescent Panic Attacks.

    Science.gov (United States)

    Hayward, Chris; Wilson, Kimberly A.; Lagle, Kristy; Killen, Joel D.; Taylor, C. Barr

    2004-01-01

    Objective: To identify parent-reported risk factors for adolescent panic attacks. Method: Structured diagnostic interviews were obtained from 770 parents of participants in a school-based risk factor study for adolescent panic. Parent-reported risk factors assessed included characteristics of the child (negative affect, separation anxiety disorder…

  4. Plasma Exchange in Severe Attacks of Neuromyelitis Optica

    Directory of Open Access Journals (Sweden)

    Mickael Bonnan

    2012-01-01

    Full Text Available Background. Neuromyelitis optica (NMO attacks are poorly controlled by steroids and evolve in stepwise neurological impairments. Assuming the strong humoral response underlying NMO attacks, plasma exchange (PLEX is an appropriate technique in severe NMO attacks. Objective. Presenting an up-to-date review of the literature of PLEX in NMO. Methods. We summarize the rationale of PLEX in relation with the physiology of NMO, the main technical aspects, and the available studies. Results. PLEX in severe attacks from myelitis or optic neuritis are associated with a better outcome, depending on PLEX delay (“time is cord and eyes”. NMO-IgG status has no influence. Finally, we build up an original concept linking the inner dynamic of the lesion, the timing of PLEX onset and the expected clinical results. Conclusion. PLEX is a safe and efficient add-on therapy in NMO, in synergy with steroids. Large therapeutic trials are required to definitely assess the procedure and define the time opportunity window.

  5. A Comparative Study of Power Consumption Models for CPA Attack

    Directory of Open Access Journals (Sweden)

    Hassen Mestiri

    2013-03-01

    Full Text Available Power analysis attacks are types of side channel attacks that are based on analyzing the power consumption of the cryptographic devices. Correlation power analysis is a powerful and efficient cryptanalytic technique. It exploits the linear relation between the predicted power consumption and the real power consumption of cryptographic devices in order to recover the correct key. The predicted power consumption is determined by using the appropriate consumption model. Until now, only a few models have been proposed and used.In this paper, we describe the process to conduct the CPA attack against AES on SASEBO-GII board. We present a comparison between the Hamming Distance model and the Switching Distance model, in terms of number of power traces needed to recover the correct key using these models. The global successful rate achieves 100% at 11100 power traces. The power traces needed to recover the correct key have been decreased by 12.6% using a CPA attack with Switching Distance model.

  6. Hydrogen attack - Influence of hydrogen sulfide. [on carbon steel

    Science.gov (United States)

    Eliezer, D.; Nelson, H. G.

    1978-01-01

    An experimental study is conducted on 12.5-mm-thick SAE 1020 steel (plain carbon steel) plate to assess hydrogen attack at room temperature after specimen exposure at 525 C to hydrogen and a blend of hydrogen sulfide and hydrogen at a pressure of 3.5 MN/sq m for exposure times up to 240 hr. The results are discussed in terms of tensile properties, fissure formation, and surface scales. It is shown that hydrogen attack from a high-purity hydrogen environment is severe, with the formation of numerous methane fissures and bubbles along with a significant reduction in the room-temperature tensile yield and ultimate strengths. However, no hydrogen attack is observed in the hydrogen/hydrogen sulfide blend environment, i.e. no fissure or bubble formation occurred and the room-temperature tensile properties remained unchanged. It is suggested that the observed porous discontinuous scale of FeS acts as a barrier to hydrogen entry, thus reducing its effective equilibrium solubility in the iron lattice. Therefore, hydrogen attack should not occur in pressure-vessel steels used in many coal gasification processes.

  7. The anatomy of a shark attack: a case report and review of the literature.

    Science.gov (United States)

    Caldicott, D G; Mahajani, R; Kuhn, M

    2001-07-01

    Shark attacks are rare but are associated with a high morbidity and significant mortality. We report the case of a patient's survival from a shark attack and their subsequent emergency medical and surgical management. Using data from the International Shark Attack File, we review the worldwide distribution and incidence of shark attack. A review of the world literature examines the features which make shark attacks unique pathological processes. We offer suggestions for strategies of management of shark attack, and techniques for avoiding adverse outcomes in human encounters with these endangered creatures.

  8. Finding new drug targets for the treatment of migraine attacks

    DEFF Research Database (Denmark)

    Olesen, J; Olesen, Jes; Tfelt-Hansen, P

    2009-01-01

    No new preventive drugs specific to migraine have appeared for the last 20 years and existing acute therapies need improvement. Unfortunately, no animal models can predict the efficacy of new therapies for migraine. Because migraine attacks are fully reversible and can be aborted by therapy...

  9. Prevalence of eating disorders and eating attacks in narcolepsy

    Directory of Open Access Journals (Sweden)

    Norbert Dahmen

    2008-03-01

    Full Text Available Norbert Dahmen, Julia Becht, Alice Engel, Monika Thommes, Peter TonnPsychiatry Department, University of Mainz, GermanyAbstract: Narcoleptic patients suffer frequently from obesity and type II diabetes. Most patients show a deficit in the energy balance regulating orexinergic system. Nevertheless, it is not known, why narcoleptic patients tend to be obese. We examined 116 narcoleptic patients and 80 controls with the structured interview for anorectic and bulimic eating disorders (SIAB to test the hypothesis that typical or atypical eating attacks or eating disorders may be more frequent in narcoleptic patients. No difference in the current prevalence of eating disorders bulimia nervosa, binge eating disorder, or anorexia nervosa was found, nor was the frequency of eating attacks higher in the narcolepsy group. We conclude that present eating disorders and eating attacks as defined in DSM IV are not the reason for the observed differences in body composition. Additional factors, such as basal metabolic rates and lifestyle factors need to be considered.Keywords: narcolepsy, eating disorder, SIAB, bulimia, anorexia, eating attack

  10. Detection techniques of selective forwarding attacks in wireless sensor networks: a survey

    CERN Document Server

    Sharma, Preeti; Saluja, Krishan Kumar

    2012-01-01

    The wireless sensor network has become a hot research area due its wide range of application in military and civilian domain, but as it uses wireless media for communication these are easily prone to security attacks. There are number of attacks on wireless sensor networks like black hole attack, sink hole attack, Sybil attack, selective forwarding attacks etc. in this paper we will concentrate on selective forwarding attacks In selective forwarding attacks, malicious nodes behave like normal nodes and selectively drop packets. The selection of dropping nodes may be random. Identifying such attacks is very difficult and sometimes impossible. In this paper we have listed up some detection techniques, which have been proposed by different researcher in recent years, there we also have tabular representation of qualitative analysis of detection techniques

  11. A Case of Brucellosis with Recurrent Attacks of Vasculitis

    OpenAIRE

    Pınar Korkmaz; Mehtap Kıdır; Nazlı Dizen Namdar; Ahmet Özmen; Cemile Uyar; Ayşe Nur Değer

    2016-01-01

    Brucellosis is a zoonosis that affects several organs or systems. Skin involvement is nonspecific and it is reported to range between 0,4 and 17% of the patients with brucellosis. Here, we defined a 36-year-old female patient presented to our clinic with a clinical picture of recurrent attacks of vasculitis due to brucellosis for the first time. Skin involvement and vasculitic lesions as a finding of skin involvement are nonspecific in brucellosis. Therefore, in the regions like Turkey where ...

  12. Managing the Threat of Denial-of-Service Attacks

    Science.gov (United States)

    2001-10-01

    Cooperative Association for Internet Data Analysis ( CAIDA ) address this question in their paper, “Inferring Internet Denial-of-Service Activity.” (see...belonging to more than 2,000 distinct organizations during a three-week period.” In addition, CAIDA reports that 90% of attacks last for one hour or less...Engineering Task Force http://www.ietf.org/html.charters/ipngwg-charter.html Inferring Internet Denial-of-Service Activity CAIDA , University of

  13. EMERGENCE ANGLE OF FLOW OVER AN AERATOR

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Aerator is an important device for release works of hydraulic structures with high-speed flow in order to protect them from cavitation damage. This kind of protecting effect is related closely to cavity length below the aerator, while the cavity length is dominated by the emergence angle over the aerator. Therefore it is crucial to determine this angle accurately. In the present paper the affecting intensities of flow depth and the fluctuating velocity on this angle were analyzed through two introduced parameters. Furthermore, the improved expressions of emergence angle estimation, for both ramp-type and step-type aerators, were presented by means of 68 sets of experimental data from 6 projects based on error theory. The results showed that the present method has higher accuracy than the previously reported methods.

  14. Pareto Efficient Solutions of Attack-Defence Trees

    DEFF Research Database (Denmark)

    Aslanyan, Zaruhi; Nielson, Flemming

    2015-01-01

    Attack-defence trees are a promising approach for representing threat scenarios and possible countermeasures in a concise and intuitive manner. An attack-defence tree describes the interaction between an attacker and a defender, and is evaluated by assigning parameters to the nodes, such as proba......Attack-defence trees are a promising approach for representing threat scenarios and possible countermeasures in a concise and intuitive manner. An attack-defence tree describes the interaction between an attacker and a defender, and is evaluated by assigning parameters to the nodes...... on a new and general formalism for attack-defence trees....

  15. Generation of plasmin during acute attacks of hereditary angioedema.

    Science.gov (United States)

    Cugno, M; Hack, C E; de Boer, J P; Eerenberg, A J; Agostoni, A; Cicardi, M

    1993-01-01

    Hereditary angioedema is caused by a genetic deficiency of C1-inhibitor, a serine protease inhibitor that regulates activation of complement, contact, and fibrinolytic systems. Symptoms (bouts of subcutaneous and mucous swelling) depend on the release of a vasoactive mediator, probably through activation of these three systems. We studied the interrelationship among complement, contact, and fibrinolytic activation in 23 patients with hereditary angiodema, 18 during remission and five during an attack, by measuring plasma levels of C1-C1 inhibitor, factor XIIa-C1 inhibitor, kallikrein-C1 inhibitor, and plasmin-alpha 2-antiplasmin complexes, tissue plasminogen activator, and urokinase plasminogen activator. In addition, cleavage of high-molecular weight kininogen was detected by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis and quantified by densitometry. During remission, plasma levels of C1-C1 inhibitor complexes were elevated (p = 0.0002), whereas the other parameters were within the normal range. During acute attacks, not only plasma levels of C1-C1 inhibitor complexes but also those of plasmin-alpha 2-antiplasmin complexes (P = 0.0009) and cleaved high-molecular weight kininogen were elevated. A positive correlation between plasmin-alpha 2-antiplasmin complexes and cleaved high-molecular weight kininogen was observed (r = 0.75, p attacks is associated with the activation of the fibrinolytic system.

  16. Resistance of the double random phase encryption against various attacks.

    Science.gov (United States)

    Frauel, Yann; Castro, Albertina; Naughton, Thomas J; Javidi, Bahram

    2007-08-06

    Several attacks are proposed against the double random phase encryption scheme. These attacks are demonstrated on computer-generated ciphered images. The scheme is shown to be resistant against brute force attacks but susceptible to chosen and known plaintext attacks. In particular, we describe a technique to recover the exact keys with only two known plain images. We compare this technique to other attacks proposed in the literature.

  17. Winding angles of long lattice walks

    Science.gov (United States)

    Hammer, Yosi; Kantor, Yacov

    2016-07-01

    We study the winding angles of random and self-avoiding walks (SAWs) on square and cubic lattices with number of steps N ranging up to 107. We show that the mean square winding angle of random walks converges to the theoretical form when N → ∞. For self-avoiding walks on the square lattice, we show that the ratio /2 converges slowly to the Gaussian value 3. For self-avoiding walks on the cubic lattice, we find that the ratio /2 exhibits non-monotonic dependence on N and reaches a maximum of 3.73(1) for N ≈ 104. We show that to a good approximation, the square winding angle of a self-avoiding walk on the cubic lattice can be obtained from the summation of the square change in the winding angles of lnN independent segments of the walk, where the ith segment contains 2i steps. We find that the square winding angle of the ith segment increases approximately as i0.5, which leads to an increase of the total square winding angle proportional to (lnN)1.5.

  18. Traits of Masson Pine Affecting Attack of Pine Wood Nematode

    Institute of Scientific and Technical Information of China (English)

    Juan Shi; You-Qing Luo; Ji-Ying Song; Hai-Wei Wu; Lei Wang; Gary Z. Wang

    2007-01-01

    Masson pine characteristics were analyzed in five sample plots in Zhejiang Province, China.Bursaphelenchus xylophilus (Steiner et Buhrer) Nickle (pine wood nematode, PWN) carried by Monochamus alternatus predominately attacked Masson pines in the lower diameter classes.Among the 10 tree characteristics examined, mean crown width, percentage of bole with crown, 5-year cumulative diameter growth, and resin amount showed significant variation between successfully attacked and unattacked trees.The attacked trees had a lower percentage of the bole covered with tree crown, lower crown width, lower radial growth in the last 5 years, and produced less induced resinosis than unattacked trees.Results allowed for effective ranking of the pine forest based on individual tree resistance to PWN.This Index of resistance should be considered throughout the development of an "Evaluation Criterion and Indicator System".The preceding ranking can be used to evaluate the resistance and resiliency of the pine forest ecosystem to PWN's invasion, which is similar to Pest Risk Analysis (PRA).

  19. A Method of Detecting Sql Injection Attack to Secure Web Applications

    Directory of Open Access Journals (Sweden)

    Manesh T

    2012-12-01

    Full Text Available Web applications are becoming an important part of our daily life. So attacks against them also increasesrapidly. Of these attacks, a major role is held by SQL injection attacks (SQLIA. This paper proposes anew method for preventing SQL injection attacks in JSP web applications. The basic idea is to checkbefore execution, the intended structure of the SQL query. For this we use semantic comparison. Ourfocus is on stored procedure attack in which query will be formed within the database itself and sodifficult to extract that query structure for validation. Also this attack is less considered in the literature.

  20. Pressure dependence of the contact angle.

    Science.gov (United States)

    Wu, Jiyu; Farouk, T; Ward, C A

    2007-06-07

    When a liquid and its vapor contact a smooth, homogeneous surface, Gibbsian thermodynamics indicates that the contact angle depends on the pressure at the three-phase line of an isothermal system. When a recently proposed adsorption isotherm for a solid-vapor interface is combined with the equilibrium conditions and the system is assumed to be in a cylinder where the liquid-vapor interface can be approximated as spherical, the contact-angle-pressure relation can be made explicit. It indicates that a range of contact angles can be observed on a smooth homogeneous surface by changing the pressure at the three-phase line, but it also indicates that the adsorption at the solid-liquid interface is negative, and leads to the prediction that the contact angle increases with pressure. The predicted dependence of the contact angle on pressure is investigated experimentally in a system that has an independent mechanism for determining when thermodynamic equilibrium is reached. The predictions are in agreement with the measurements. The results provide a possible explanation for contact angle hysteresis.

  1. Prevention of Spoofing Attacks in the Infrastructure Wireless Networks

    Directory of Open Access Journals (Sweden)

    Samraa A. AlAsady

    2012-01-01

    Full Text Available Problem statement: Spoofing Attack is one of the vulnerabilities in the wireless networks, which is a situation in which the intruder successfully masquerades as legal one. Spoofing Attacks will decrease the performance of the network and violate many security issues. In the networks that use MAC address based filtering approach to authenticate the clients, the spoofer just needs to get a valid MAC address that belong to some authorized client in the network in order to gain an illegitimate advantage. Approach: In this article, it has proposed an algorithm that uses an additional authentication process beside MAC address filtering and periodically re-authenticates the client after sending every specific number of Data frames. The proposed additional authentication process is based on two parts. First: Using unique information that belongs to every client in the network such as computer name, CPU ID and the current time as inputs to a hash function (one-way function, then insert the hash value in the slack fields of the header of the frame (Steganography. Second: Make a modification to the access point access control list by adding that unique information belong to each client in addition to its MAC address in the access control list. Thus, when the AP receives an Authentication frame from a client, it will first check the MAC address, if it is legal; the AP will re-compute the Hash value depending on the corresponding identifiers stored in the access control list and the time of creating the frame, then compare the resulted hash value with the received one and decide whether to reject or accept the access. Results: The results has been found is that even the attacker is spoofed the MAC address; he/she cannot communicate with the network because the attacker will fail in computing the hash value that depends on the Computer name and CPU ID. Also the attacker will be prevented even if he/she enters the network after the legal client finished the

  2. Open-label, multicenter study of self-administered icatibant for attacks of hereditary angioedema

    DEFF Research Database (Denmark)

    Aberer, W; Maurer, M; Reshef, A

    2014-01-01

    Historically, treatment for hereditary angioedema (HAE) attacks has been administered by healthcare professionals (HCPs). Patient self-administration could reduce delays between symptom onset and treatment, and attack burden. The primary objective was to assess the safety of self...

  3. Conestat alfa for the treatment of angioedema attacks

    Directory of Open Access Journals (Sweden)

    Davis B

    2011-07-01

    Full Text Available Benjamin Davis, Jonathan A BernsteinUniversity of Cincinnati College of Medicine, Department of Internal Medicine, Division of Immunology/Allergy Section, Cincinnati, OH, USAAbstract: Recently, multiple C1 inhibitor (C1-INH replacement products have been approved for the treatment of hereditary angioedema (HAE. This review summarizes HAE and its current treatment modalities and focuses on findings from bench to bedside trials of a new C1-INH replacement, conestat alfa. Conestat alfa is unique among the other C1-INH replacement products because it is produced from transgenic rabbits rather than derived from human plasma donors, which can potentially allow an unlimited source of drug without any concern of infectious transmission. The clinical trial data generated to date indicate that conestat alfa is safe and effective for the treatment of acute HAE attacks.Keywords: androgens, adverse events, patients, HAE attacks 

  4. STUDY OF PRIVILEGE ESCALATION ATTACK ON ANDROID AND ITS COUNTERMEASURES

    Directory of Open Access Journals (Sweden)

    REJO MATHEW

    2012-09-01

    Full Text Available Android is most commonly used platform for smartphones today which boasts of an advanced security model having MAC and sandboxing. These features allow developers and users to restrict the execution of anapplication to the privileges assigned. The exploitation of vulnerabilities of the program is confined within the privilege boundaries of an applications sandbox. Privilege escalation attacks have grown manifold as the use of android systems have increased. Different kinds of mechanisms have provided some sort of respite to the developers but the security feature handling by the developers has not helped much. In this paper we discuss the basics of the privilege escalation attack and the various techniques used to counter and prevent this problem.

  5. The pathophysiology of the migraine attack

    NARCIS (Netherlands)

    E.L.H. Spierings

    1980-01-01

    textabstractMigraine, a word of French origin, is a mediaeval corruption of the Greek hemicrania". Its etymological meaning, half-headache, indicates two important features of the disorder, the headache and its onesidedness. In classical migraine, the headache is preceded by an 'aura' of focal neuro

  6. Multilevel Modeling of Distributed Denial of Service Attacks in Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Katarzyna Mazur

    2016-01-01

    Full Text Available The growing popularity of wireless sensor networks increases the risk of security attacks. One of the most common and dangerous types of attack that takes place these days in any electronic society is a distributed denial of service attack. Due to the resource constraint nature of mobile sensors, DDoS attacks have become a major threat to its stability. In this paper, we established a model of a structural health monitoring network, being disturbed by one of the most common types of DDoS attacks, the flooding attack. Through a set of simulations, we explore the scope of flood-based DDoS attack problem, assessing the performance and the lifetime of the network under the attack condition. To conduct our research, we utilized the Quality of Protection Modeling Language. With the proposed approach, it was possible to examine numerous network configurations, parameters, attack options, and scenarios. The results of the carefully performed multilevel analysis allowed us to identify a new kind of DDoS attack, the delayed distributed denial of service, by the authors, referred to as DDDoS attack. Multilevel approach to DDoS attack analysis confirmed that, examining endangered environments, it is significant to take into account many characteristics at once, just to not overlook any important aspect.

  7. Distributed Detection of Wormhole Attacks in Wireless Sensor Networks

    Science.gov (United States)

    de Graaf, Rennie; Hegazy, Islam; Horton, Jeffrey; Safavi-Naini, Reihaneh

    Sensors in a wireless sensor network depend on their neighbours to route their messages. Yet, routing protocols in wireless sensor network are vulnerable to different types of attacks. In this paper, we consider the wormhole attack in which the adversary diverts traffic from one part of the network to another part by introducing a low cost tunnel between the two parts. We introduce a distributed intrusion detection system that monitors the communication in the network and propose a criterion for the placement of intrusion detection nodes. The intrusion detection system searches for violations of that criterion to detect wormholes of length above a certain minimum value. We evaluate the effectiveness of our system in a simulated environment. The experiments show that our system can detect 100% of the wormholes that are beyond the communication range of the intrusion detection nodes. Finally, we discuss our results and show directions for future work.

  8. A Study of Black Hole Attack on MANET Performance

    Directory of Open Access Journals (Sweden)

    C. K. Nagpal

    2012-08-01

    Full Text Available Mobile Ad hoc Network (MANET is a self-organized wireless network, consisting of nodes (mobile devices responsible for its creation, operation and maintenance. The communication in the MANET is of multihop in nature due to absence of any fixed infrastructure. An attacker may intrude easily into MANET by posing as legitimate intermediate node and present various types of security attacks on data exchanges taking place between source and destination. In this paper we study the impact of presence of black hole node on MANET performance on the basis of reachability, hop count, neighbor node density and path optimality. We observe that as the percentage of black hole nodes increases, the MANET performance degrades significantly.

  9. Cyber Attack! Crime or Act of War?

    Science.gov (United States)

    2011-04-13

    to count the number of electrons dancing on the head of a pin. But the definition of what is an act of war and what is not carries a great deal of...being evaluated is in a traditional domain or the cyber domain, the standard for determining if a casus belli exists should be the same. Nevertheless...features of the cyber domain.14 We want to focus on just the factors in the cyber domain that make determinations regarding casus belli more difficult

  10. Analysis of signature wrapping attacks and countermeasures

    DEFF Research Database (Denmark)

    Gajek, Sebastian; Jensen, Meiko; Liao, Lijun

    2009-01-01

    In recent research it turned out that Boolean verification, of digital signatures in the context of WSSecurity, is likely to fail: If parts of a SOAP message, are signed and the signature verification applied to, the whole document returns true, then nevertheless the, document may have been...

  11. Study of attack in college volleyball

    Directory of Open Access Journals (Sweden)

    Yordan Portela Pozo

    2014-03-01

    Full Text Available AbstractThis work is done in order to analyze the positive and negative aspects that affected the performance of the auction action in volleyball players performing this action (in this case male in the Provincial University Games in 2012 in Havana , for which I take as a case study to the players of the University of Information Sciences and its opponents in those games, completing a total of 268 shares auctions in 7 games with a total of 15 September analyzed taking account of changes in the sport of Volleyball university in Cuba, data recorded by an observation sheet previously completed by the authors. The main results in this paper show that the greatest amount of shots that were done in these games were diagonal and a good percentage of positive linear auctions however were few and with very poor results. The primary role of the auction for the game's success is fully confirmed in this work because this action is achieved through many points in the game of volleyball and thus leads to a better result.

  12. Performance analyses of wormhole attack in Cognitive Radio Network (CRN

    Directory of Open Access Journals (Sweden)

    Prabhjot

    2015-06-01

    Full Text Available Mobile wirelesses networks are generally open to various attacks like information and physical security attacks than fixed wired networks. Securing wireless ad hoc networks is particularly more difficult for many of the reasons for example vulnerability of channels and nodes, absence of infrastructure, dynamically changing topology etc. After that we initialize the number of nodes. Then implement protocol for the communication of nodes. Due to these protocols communication start. And this will be then implemented in CRNs which stand for cognitive radio network in which channel sensing is done. By the use of CRN security will be improved and performance will be enhanced. Find the malicious nodes occur in the network. One malicious node uses routing protocol to claim itself of being shortest path to last node but drops routing packets and doesn’t send packets to its neighbors. In last evaluate the parameters.

  13. Applying the Principles of Homicide by Heart Attack.

    Science.gov (United States)

    Hlavaty, Leigh; Sung, LokMan

    2016-06-01

    Homicide by heart attack is a well-established model in forensic pathology that describes death elicited during or immediately after a criminal act where a threat or fear of physical injury is present. After its introduction nearly 4 decades ago, the principle has undergone a handful of modifications but still maintains its core concepts. All cases of this nature during a 20-year period at the Wayne County Medical Examiner's Office were compared and contrasted for demographics, circumstances and scene investigation, and autopsy and toxicology findings. Of the cases fulfilling the previously established criteria for homicide by heart attack, more than 80% displayed significant changes because of hypertension. This finding coincides with the high prevalence of hypertension in our urban population and highlights the significance of this disease. Also present were minor external and internal injuries in select cases, which reinforce the understanding that physical contact between the decedent and assailant does not preclude this diagnosis.

  14. Use of forensic analysis to better understand shark attack behaviour.

    Science.gov (United States)

    Ritter, E; Levine, M

    2004-12-01

    Shark attacks have primarily been analyzed from wound patterns, with little knowledge of a shark's approach, behaviour and intention leading to such wounds. For the first time, during a shark-human interaction project in South Africa, a white shark, Carcharodon carcharias, was filmed biting a vertically positioned person at the water surface, and exhibiting distinct approach patterns leading to the bite. This bite was compared to ten white shark attacks that occurred (i) in the same geographical area of South Africa, and (ii) where the same body parts were bitten. Close similarity of some of these wound patterns to the bite imprint of the videotaped case indicate that the observed behaviour of the white shark may represent a common pattern of approaching and biting humans.

  15. Identification of Secret Algorithms Using Oracle Attacks

    Science.gov (United States)

    2011-01-28

    very little information. Since it is likely for steganography to be used on very large multimedia files, e.g. audio and video, there are substantial...algorithms, the PI developed methods to better detect and estimate +/-K embedding, a common form of steganography . This research project was undertaken at...exist at all. The use of an unusually artificial carrier is suspicious on its face, negating the purpose of steganography . If, however, such a

  16. Under attack: a way of life

    Directory of Open Access Journals (Sweden)

    David Eubank

    2008-04-01

    Full Text Available Much of what is happening in the conflict zones ofeastern Burma is difficult to capture with photos, videoand reports. It is a slow and insidious strangulation of thepopulation rather than an all-out effort to crush them.

  17. Resilience of LTE networks against smart jamming attacks: Wideband model

    KAUST Repository

    Aziz, Farhan M.

    2015-12-03

    LTE/LTE-A networks have been successfully providing advanced broadband services to millions of users worldwide. Lately, it has been suggested to use LTE networks for mission-critical applications like public safety, smart grid and military communications. We have previously shown that LTE networks are vulnerable to Denial-of-Service (DOS) and loss of service attacks from smart jammers. In this paper, we extend our previous work on resilience of LTE networks to wideband multipath fading channel, SINR estimation in frequency domain and computation of utilities based on observable parameters under the framework of single-shot and repeated games with asymmetric information. In a single-shot game formulation, network utility is severely compromised at its solutions, i.e. at the Nash Equilibria (NE). We propose evolved repeated-game strategy algorithms to combat smart jamming attacks that can be implemented in existing deployments using current technology. © 2015 IEEE.

  18. Controlling Sulfate Attack in Mississippi Department of Transportation Structures

    Science.gov (United States)

    2010-08-01

    one of the materials that normally forms during the early setting of portland cement from a reaction between calcium aluminate and gypsum in the...such as calcium aluminates and calcium hydroxide, can influence the degree of damage observed. In all cases, the deterioration observed appears to be...counterions, such as calcium, magnesium , or sodium. Additionally, there are well-documented cases of concrete deterioration due to acid sulfate attack

  19. Diagnosis of slight and subacute coronary attacks in the community.

    OpenAIRE

    Short, D.

    1981-01-01

    A series of 456 episodes of spontaneous chest pain not considered by the primary medical attendant to be sufficiently severe or suggestive of coronary disease to warrant admission to hospital has been studied prospectively in an attempt to provide guidelines for diagnosis and management. A final diagnosis of acute myocardial infarction was made in 40 per cent, spontaneous (or unstable) angina in 15 per cent, doubtful coronary attack in 12 per cent, and non-coronary chest pain in 33 per cent o...

  20. Classification of artificial intelligence ids for smurf attack

    CERN Document Server

    Ugtakhbayar, N; Sodbileg, Sh

    2012-01-01

    Many methods have been developed to secure the network infrastructure and communication over the Internet. Intrusion detection is a relatively new addition to such techniques. Intrusion detection systems (IDS) are used to find out if someone has intrusion into or is trying to get it the network. One big problem is amount of Intrusion which is increasing day by day. We need to know about network attack information using IDS, then analysing the effect. Due to the nature of IDSs which are solely signature based, every new intrusion cannot be detected; so it is important to introduce artificial intelligence (AI) methods / techniques in IDS. Introduction of AI necessitates the importance of normalization in intrusions. This work is focused on classification of AI based IDS techniques which will help better design intrusion detection systems in the future. We have also proposed a support vector machine for IDS to detect Smurf attack with much reliable accuracy.

  1. Resilience of LTE networks against smart jamming attacks

    KAUST Repository

    Aziz, Farhan M.

    2014-12-08

    Commercial LTE networks are being studied for mission-critical applications, such as public safety and smart grid communications. In this paper, LTE networks are shown vulnerable to Denial-of-Service (DOS) and loss of service attacks from smart jammers, who may employ simple narrowband jamming techniques to attack without any need to hack the network or its users. We modeled the utilities of jamming and anti-jamming actions played by the jammer and the network under the framework of single-shot and repeated Bayesian games. In a single-shot game formulation the only Nash Equilibria (NE) are pure strategy equilibria at which network utility is severely compromised. We propose a repeated-game learning and strategy algorithm for the network that outperforms single-shot games by a significant margin. Furthermore, all of our proposed actions and algorithms can be implemented with current technology.

  2. Detection Techniques of DOS/DDOS/DRDOS Attacks in Networks of Mass Service

    Directory of Open Access Journals (Sweden)

    G. Shangytbayeva

    2015-08-01

    Full Text Available The study describes the basic network attacks such as "denial of service", algorithm of operation of malefactors with attacks of this type, techniques of detection of DOS/DDOS/DRDOS attacks in networks of mass service. For detection of DDoS-attacks is offered the valuation method of probability of loss of arbitrary request in case of its passing on networks of mass service. Developed the architecture and constructed program implementation of system of detection of DDoS-attacks. The developed technique allows to receive an adequate assessment of frequency of loss of requests on a network if the network of mass service is in the stationary mode.

  3. Error and attack vulnerability of temporal networks

    NARCIS (Netherlands)

    Trajanovski, S.; Scellato, S.; Leontiadis, I.

    2012-01-01

    The study of real-world communication systems via complex network models has greatly expanded our understanding on how information flows, even in completely decentralized architectures such as mobile wireless networks. Nonetheless, static network models cannot capture the time-varying aspects and, t

  4. Web Application Scanning and Identification of Vulnerabilities for Different Attacks

    Directory of Open Access Journals (Sweden)

    Haridas V.Kanure,

    2014-05-01

    Full Text Available Now days there are lots of websites present in internet. And providing different services to the client is not only important task for website owner but also protecting their website from different attacks. Now days Identification of vulnerabilities in web application is becoming serious issue. Protecting website by identifying vulnerabilities and taking important attack prevention steps is very much important task.Different vulnerabilities identification is based on different test cases which we have and which we are going to build by use of this tool. Those test cases come from combination of some effective code. SQL injection test case can work with effective database query. And Cross site scripting can works with some java script code or other scripting language code etc.

  5. Use of outcomes to evaluate surveillance systems for bioterrorist attacks

    Directory of Open Access Journals (Sweden)

    Abrams Allyson M

    2010-05-01

    Full Text Available Abstract Background Syndromic surveillance systems can potentially be used to detect a bioterrorist attack earlier than traditional surveillance, by virtue of their near real-time analysis of relevant data. Receiver operator characteristic (ROC curve analysis using the area under the curve (AUC as a comparison metric has been recommended as a practical evaluation tool for syndromic surveillance systems, yet traditional ROC curves do not account for timeliness of detection or subsequent time-dependent health outcomes. Methods Using a decision-analytic approach, we predicted outcomes, measured in lives, quality adjusted life years (QALYs, and costs, for a series of simulated bioterrorist attacks. We then evaluated seven detection algorithms applied to syndromic surveillance data using outcomes-weighted ROC curves compared to simple ROC curves and timeliness-weighted ROC curves. We performed sensitivity analyses by varying the model inputs between best and worst case scenarios and by applying different methods of AUC calculation. Results The decision analytic model results indicate that if a surveillance system was successful in detecting an attack, and measures were immediately taken to deliver treatment to the population, the lives, QALYs and dollars lost could be reduced considerably. The ROC curve analysis shows that the incorporation of outcomes into the evaluation metric has an important effect on the apparent performance of the surveillance systems. The relative order of performance is also heavily dependent on the choice of AUC calculation method. Conclusions This study demonstrates the importance of accounting for mortality, morbidity and costs in the evaluation of syndromic surveillance systems. Incorporating these outcomes into the ROC curve analysis allows for more accurate identification of the optimal method for signaling a possible bioterrorist attack. In addition, the parameters used to construct an ROC curve should be given careful

  6. A Review of Virtual Machine Attack Based on Xen

    Directory of Open Access Journals (Sweden)

    Ren xun-yi

    2016-01-01

    Full Text Available Virtualization technology as the foundation of cloud computing gets more and more attention because the cloud computing has been widely used. Analyzing the threat with the security of virtual machine and summarizing attack about virtual machine based on XEN to predict visible security hidden recently. Base on this paper can provide a reference for the further research on the security of virtual machine.

  7. Robustness of networks against propagating attacks under vaccination strategies

    CERN Document Server

    Hasegawa, Takehisa

    2011-01-01

    We study the effect of vaccination on robustness of networks against propagating attacks that obey the susceptible-infected-removed model. By extending the generating function formalism developed by Newman (2005), we analytically determine the robustness of networks that depends on the vaccination parameters. We consider the random defense where nodes are vaccinated randomly and the degree-based defense where hubs are preferentially vaccinated. We apply the obtained results to the random graph and scale-free networks.

  8. Management of acute attacks of hereditary angioedema: role of ecallantide

    Directory of Open Access Journals (Sweden)

    Duffey H

    2015-04-01

    Full Text Available Hannah Duffey,1 Rafael Firszt1,2 1Department of Pediatrics, 2Division of Allergy, Immunology and Rheumatology, University of Utah, Salt Lake City, UT, USA Abstract: Hereditary angioedema (HAE is characterized as an episodic swelling disorder with autosomal dominant inheritance. Clinical features include nonpitting edema of external or mucosal body surfaces, and patients often present with swelling of the extremities, abdominal pain, and swelling of the mouth and throat, which can lead to asphyxiation. Patients with HAE classically have no associated urticaria, which is often referred to as nonhistaminergic angioedema. Treatment for HAE involves long-term prophylaxis, short-term prophylaxis, and management of acute attacks. Up until the past few years, acute HAE episodes were predominately treated with supportive measures. Three classes of medications have recently been approved by the US Food and Drug Administration (FDA for the management of acute HAE attacks. Ecallantide, a recombinant protein that acts as a reversible inhibitor of kallikrein, is currently indicated for acute attacks of HAE in those aged 12 years. In two randomized, double-blind, placebo-controlled, multicenter trials, EDEMA3 and EDEMA4, patients treated with 30 mg of ecallantide demonstrated statistically significant improvement in symptoms compared to those on placebo. In addition to its use as treatment for HAE, ecallantide has been used off label in the management of nonhistaminergic angioedema, not due to HAE. Ecallantide has shown promise in the treatment of these other forms; however, data are limited to mainly case reports at this time. Ecallantide is generally a safe and well-tolerated medication; however, based on reports of anaphylaxis, ecallantide does contain a black box warning. Due to the risk of anaphylaxis, ecallantide cannot be self-administered and must be given by a health care professional. Overall, ecallantide is a safe and effective medication for the

  9. Animal attack: an unusual case of multiple trauma in childhood.

    Science.gov (United States)

    O'Grady, E; Doyle, M; Fitzgerald, C W R; Mortell, A; Murray, D

    2014-01-01

    A 2½ year old girl attended our facility following attack by a tapir at a city zoo. She sustained multiple injuries including a forearm laceration and multiple perforating wounds to her abdominal wall. She had several procedures, including bowel resection, performed under the care of the General Paediatric Surgery and Plastic Surgery teams and was treated with a course of IV antibiotics. She recovered well and to date has suffered no long-term adverse outcome.

  10. Animal attack: an unusual case of multiple trauma in childhood.

    LENUS (Irish Health Repository)

    O'Grady, E

    2014-11-01

    A 2½ year old girl attended our facility following attack by a tapir at a city zoo. She sustained multiple injuries including a forearm laceration and multiple perforating wounds to her abdominal wall. She had several procedures, including bowel resection, performed under the care of the General Paediatric Surgery and Plastic Surgery teams and was treated with a course of IV antibiotics. She recovered well and to date has suffered no long-term adverse outcome.

  11. [Hereditary angioedema. Treatment of acute attacks in Argentina].

    Science.gov (United States)

    Malbrán, Alejandro; Malbrán, Eloisa; Menéndez, Alejandra; Fernández Romero, Diego S

    2014-01-01

    In the world, hereditary angioedema (HAE) affects 1 every 50000 persons. It is characterized by highly disabling and recurrent episodes of cutaneous, abdominal and laryngeal episodes of angioedema. Asphyxia related mortality ranges from 15 to 50%. In Argentina a plasma derived C1 inhibitor concentrate (pdC1INH) has been available for the treatment of acute attacks for many decades, however, only15 (26%) out of 58 patients had received pdC1INH at least once until 2008, and only2 (3.4%) had used it regularly. After worldwide approval of the new drugs for the treatment of acute HAE attacks, adding icatibant to pdC1INH in Argentina, and after publication of the therapeutic guide for the country, 42 (82%) out of 51 patients from the original group has pdC1INH available to treat their next attack. However, 16 (18%) patients continue without access to medication and other 15 (35.7%) obtain their therapy spuriously through some other affected relative in their environment. Only 12 (28.6%) patients of the group self-treated at home. Access to treatment has greatly improved, but needs to be extended to all patients and self-treatment at home should be encouraged.

  12. Realization of correlation attack against the fuzzy vault scheme

    Science.gov (United States)

    Kholmatov, Alisher; Yanikoglu, Berrin

    2008-02-01

    User privacy and template security are major concerns in the use of biometric systems. These are serious concerns based on the fact that once compromised, biometric traits can not be canceled or reissued. The Fuzzy Vault scheme has emerged as a promising method to alleviate the template security problem. The scheme is based on binding the biometric template with a secret key and scrambling it with a large amount of redundant data, such that it is computationally infeasible to extract the secret key without possession of the biometric trait. It was recently claimed that the scheme is susceptible to correlation based attacks which assume the availability of two fuzzy vaults created using the same biometric data (e.g. two impressions of the same fingerprint) and suggests that correlating them would reveal the biometric data hidden inside. In this work, we implemented the fuzzy vault scheme using fingerprints and performed correlation attacks against a database of 400 fuzzy vaults (200 matching pairs). Given two matching vaults, we could successfully unlock 59% of them within a short time. Furthermore, it was possible to link an unknown vault to a short list containing its matching pair, for 41% of all vaults. These results prove the claim that the fuzzy vault scheme without additional security measures is indeed vulnerable to correlation attacks.

  13. Threat Assessment of Potential Terrorist Attacks to the Transport Infrastructure

    Directory of Open Access Journals (Sweden)

    Gabriel Nowacki

    2014-06-01

    Full Text Available The paper presents threat assessment of potential terrorist attacks to the transport infrastructure. The range of transportation infrastructure has spread and includes railway, inland waterways, road, maritime, air, intermodal transport infrastructure and intelligent transport systems (ITS. ITS service is the provision of an ITS application through a well-defined organisational and operational framework with the aim of contributing to the user safety, efficiency, comfort and/or to facilitate or support transport and travel operations. Terrorism means acts of violence committed by groups that view themselves as victimized by some notable historical wrong. Although these groups have no formal connection with governments, they usually have the financial and moral backing of sympathetic governments. Typically, they stage unexpected attacks on civilian targets, including transport infrastructure, with the aim of sowing fear and confusion. Based on the analyses, transportation infrastructure is potentially threatened with terrorism attacks, especially road and rail infrastructure (about 23 %, and to a smaller degree the maritime and air transport infrastructure (about 2 %. There were 90,3% of incidents involve land transport (74,5% – vehicles, 9,5% – buses, 6,3% - rail covered the 41-year period 1967-2007 in the USA. Legal steps to fight terrorism have been taken on the international level, furthermore, some institutions have been established for this purpose.

  14. Comparison of artificial intelligence classifiers for SIP attack data

    Science.gov (United States)

    Safarik, Jakub; Slachta, Jiri

    2016-05-01

    Honeypot application is a source of valuable data about attacks on the network. We run several SIP honeypots in various computer networks, which are separated geographically and logically. Each honeypot runs on public IP address and uses standard SIP PBX ports. All information gathered via honeypot is periodically sent to the centralized server. This server classifies all attack data by neural network algorithm. The paper describes optimizations of a neural network classifier, which lower the classification error. The article contains the comparison of two neural network algorithm used for the classification of validation data. The first is the original implementation of the neural network described in recent work; the second neural network uses further optimizations like input normalization or cross-entropy cost function. We also use other implementations of neural networks and machine learning classification algorithms. The comparison test their capabilities on validation data to find the optimal classifier. The article result shows promise for further development of an accurate SIP attack classification engine.

  15. Packet track and traceback mechanism against denial of service attacks

    Institute of Scientific and Technical Information of China (English)

    LI Li; SHEN Su-bin

    2008-01-01

    The denial of service attack is a main type of threat on the Internet today. On the basis of path identification (Pi) and Internet control message protocol (ICMP) traceback (iTrace) methods, a packet track and traceback mechanism is proposed, which features rapid response and high accuracy. In this scheme, routers apply packet marking scheme and send traceback messages, which enables the victim to design the path tree in peace time. During attack times the victim can trace attackers back within the path tree and perform rapid packet filtering using the marking in each packet. Traceback messages overcome Pi's limitation, wherein too much path information is lost in path identifiers; whereas path identifiers can be used to expedite the design of the path-tree, which reduces the high overhead in iTrace. Therefore, our scheme not only synthesizes the advantages but also compromises the disadvantages of the above two methods. Simulation results with NS-2 show the validity of our scheme.

  16. Attack and improvements of fair quantum blind signature schemes

    Science.gov (United States)

    Zou, Xiangfu; Qiu, Daowen

    2013-06-01

    Blind signature schemes allow users to obtain the signature of a message while the signer learns neither the message nor the resulting signature. Therefore, blind signatures have been used to realize cryptographic protocols providing the anonymity of some participants, such as: secure electronic payment systems and electronic voting systems. A fair blind signature is a form of blind signature which the anonymity could be removed with the help of a trusted entity, when this is required for legal reasons. Recently, a fair quantum blind signature scheme was proposed and thought to be safe. In this paper, we first point out that there exists a new attack on fair quantum blind signature schemes. The attack shows that, if any sender has intercepted any valid signature, he (she) can counterfeit a valid signature for any message and can not be traced by the counterfeited blind signature. Then, we construct a fair quantum blind signature scheme by improved the existed one. The proposed fair quantum blind signature scheme can resist the preceding attack. Furthermore, we demonstrate the security of the proposed fair quantum blind signature scheme and compare it with the other one.

  17. EFFICACY AND TOLERABILITY OF STOPAIN FOR A MIGRAINE ATTACK

    Directory of Open Access Journals (Sweden)

    Andrea eSt. Cyr

    2015-02-01

    Full Text Available ObjectiveTo determine whether topical menthol 6% gel will relieve a migraine attack.Materials and MethodsA single-center, open-label pilot trial of 25 patients with at least one year of diagnosed episodic migraine and < 15 headache days per month. Patients treated one migraine attack with STOPAIN topical menthol 6% gel to skull base within 2 hours of headache onset. Headache pain severity was assessed prior to and after gel application. ResultsThirty-two patients enrolled and 25 completed the study. Prior to treatment, seven patients had mild pain, 13 moderate pain, and five severe pain. Two hours following gel application, 7 patients had no pain, 7 mild pain, 6 moderate pain and 5 severe pain. The majority of patients had similar pain intensity (8; 32 % or improvement (13; 52%. At 24-hour, only 2 non-rescued patients still had mild headache. Of the 25 completers, two patients took rescue medication prior to the 2-hour period, and an additional 10 patients rescued between 2 and 24 hours. ConclusionStudy results showed a significant improvement in headache intensity by 2 hours after gel application. This pilot study shows STOPAIN gel may be effective in treating an acute migraine attack.

  18. Identifying optimal targets of network attack by belief propagation

    Science.gov (United States)

    Mugisha, Salomon; Zhou, Hai-Jun

    2016-07-01

    For a network formed by nodes and undirected links between pairs of nodes, the network optimal attack problem aims at deleting a minimum number of target nodes to break the network down into many small components. This problem is intrinsically related to the feedback vertex set problem that was successfully tackled by spin-glass theory and an associated belief propagation-guided decimation (BPD) algorithm [Zhou, Eur. Phys. J. B 86, 455 (2013), 10.1140/epjb/e2013-40690-1]. In the present work we apply the BPD algorithm (which has approximately linear time complexity) to the network optimal attack problem and demonstrate that it has much better performance than a recently proposed collective information algorithm [Morone and Makse, Nature 524, 65 (2015), 10.1038/nature14604] for different types of random networks and real-world network instances. The BPD-guided attack scheme often induces an abrupt collapse of the whole network, which may make it very difficult to defend.

  19. Attack Robustness of Scale-Free Networks Based on Grey Information

    Institute of Scientific and Technical Information of China (English)

    LI Jun; WU Jun; LI Yong; DENG Hong-Zhong; TAN Yue-Jin

    2011-01-01

    We introduce an attack robustness model of scale-free networks based on grey information, which means that one can obtain the information of all nodes, but the attack information may be imprecise. The known random failure and the intentional attack are two extreme cases of our investigation. Using the generating function method, we derive the analytical value of the critical removal fraction of nodes for the disintegration of networks, which agree with the simulation results well. We also investigate the effect of grey information on the attack robustness of scale-free networks and find that decreasing the precision of attack information can remarkably enhance the attack robustness of scale-free networks.%@@ We introduce an attack robustness model of scale-free networks based on grey information,which means that one can obtain the information of al1 nodes,but the attack information may be imprecise.The known random failure and the intentional attack are two extreme cases of our investigation.Using the generating function method,we derive the analytical value of the critical removal fraction of nodes for the disintegration of networks,which agree with the simulation results well.We also investigate the effect of grey information on the attack robustness of scale-free networks and find that decreasing the precision of attack information can remarkably enhance the attack robustness of scale-free networks.

  20. Device Measures Angle Of Deployment

    Science.gov (United States)

    Jermakian, Joel B.

    1991-01-01

    Simple electromechanical device indicates angular position of unfolding panel during and after deployment. Resistance of potentiometer gradually increases as unfolding of solar panel about hinge moves wiper of potentiometer. At full deployment, panel pushes and opens normally closed switch. Designed for use on panel of solar photovoltaic cells in spacecraft, modified for use in other, similar position-indicating applications.

  1. Understanding how components of organisations contribute to attacks

    NARCIS (Netherlands)

    Gu, Min; Aslanyan, Zaruhi; Probst, Christian W.

    2016-01-01

    Attacks on organisations today explore many different layers, including buildings infrastructure, IT infrastructure, and human factor – the physical, virtual, and social layer. Identifying possible attacks, understanding their impact, and attributing their origin and contributing factors is difficul

  2. Precision measurements of the CKM angle gamma

    CERN Document Server

    CERN. Geneva

    2016-01-01

    The level of CP-violation permitted within the Standard Model cannot account for the matter dominated universe in which we live. Within the Standard Model the CKM matrix, which describes the quark couplings, is expected to be unitary. By making precise measurements of the CKM matrix parameters new physics models can be constrained, or with sufficient precision the effects of physics beyond the standard model might become apparent. The CKM angle gamma is the least well known angle of the unitarity triangle. It is the only angle easily accessible at tree-level, and furthermore has almost no theoretical uncertainties. Therefore it provides an invaluable Standard Model benchmark against which other new physics sensitive tests of the CP-violation can be made. I will discuss recent measurements of gamma using the the Run 1 LHCb dataset, which improve our knowledge of this key parameter.

  3. ANOMALY BASED APPROACH FOR DEFENDING DENIAL OF SERVICE ATTACK IN WEB TRAFFIC

    Directory of Open Access Journals (Sweden)

    R. Ramkumar

    2015-10-01

    Full Text Available Distributed Denial of Service (DDOS attacks has become a great threat for internet security. This attackis an advanced form of DOS (Denial of Service attack. This attack changes its whole origin ID and it gives trouble to find it out and it has become a serious threat for internet security.

  4. The accountability problem of flooding attacks in service-oriented architectures

    DEFF Research Database (Denmark)

    Jensen, Meiko; Schwenk, Jörg

    2009-01-01

    The threat of Denial of Service attacks poses a serious problem to the security of network-based services in general. For flooding attacks against service-oriented applications, this threat is dramatically amplified with potentially much higher impact and very little effort on the attacker's side...

  5. COMPARING THE IMPACT OF BLACK HOLE AND GRAY HOLE ATTACKS IN MOBILE ADHOC NETWORKS

    Directory of Open Access Journals (Sweden)

    Bose

    2012-01-01

    Full Text Available Mobile Adhoc Networks (MANETs are dynamic in nature. Any nodes can join and leave the network at any time. Hence any type of intruders can attack the communication at any time, especially the routing mechanism between the nodes. In this study, we study and understand two types of attacks which cause more damage to the routing performance of MANET; the attacks are Black Hole attacks and Gray Hole attacks and compare the impact of these attacks on MANET. “Send Fake Route Reply to the nodes” type of attack is used to understand the behavior of these two types of attacks. Existing AODV protocol is modified in order to study these types of attacks in MANET. Performance evaluation of the proposed method is carried out using NS-2. In the presence of these attacks the network performance degrades for various network attributes. The performance of MANET under attack is thoroughly investigated, by applying it on various network parameters with various node densities. Not only had that which attack causes more damage to the environment also studied.

  6. A Case of Brucellosis with Recurrent Attacks of Vasculitis

    Directory of Open Access Journals (Sweden)

    Pınar Korkmaz

    2016-01-01

    Full Text Available Brucellosis is a zoonosis that affects several organs or systems. Skin involvement is nonspecific and it is reported to range between 0,4 and 17% of the patients with brucellosis. Here, we defined a 36-year-old female patient presented to our clinic with a clinical picture of recurrent attacks of vasculitis due to brucellosis for the first time. Skin involvement and vasculitic lesions as a finding of skin involvement are nonspecific in brucellosis. Therefore, in the regions like Turkey where brucellosis is endemic, brucellosis should be kept in mind necessarily in the differential diagnosis of vasculitis.

  7. Shark attack.

    Science.gov (United States)

    Guidera, K J; Ogden, J A; Highhouse, K; Pugh, L; Beatty, E

    1991-01-01

    Shark attacks are rare but devastating. This case had major injuries that included an open femoral fracture, massive hemorrhage, sciatic nerve laceration, and significant skin and muscle damage. The patient required 15 operative procedures, extensive physical therapy, and orthotic assistance. A review of the literature pertaining to shark bites is included.

  8. Damage Measurement of Collision Attacks on Performance of Wireless Sensor Networks

    Directory of Open Access Journals (Sweden)

    Mina Malekzadeh

    2014-12-01

    Full Text Available Wireless sensor networks (WSN are widely developed to monitor different phenomena in a variety of areas including nature, medical centers, home automation, industrial and military applications. Such development in many different fields, raises important security issues related to the reliability of the WSNs. Due to the resource constrained nature of the WSNs, these networks are the target of many different types of attacks and prone to failure. In this paper, we consider the collision attack. An attempt has been made to measure the impact of the collision attack on the performance of WSNs under variety scenarios performed by the attackers. The main contribution of this paper is to present that although the attack does not consume much energy of the attacker, it can highly disrupt the normal operation of the target sensor networks. The implementation of the proposed attack model has been done by using NS2 network simulator.

  9. An Analysis of Media’s Role: Case Study of Army Public School (APS Peshawar Attack

    Directory of Open Access Journals (Sweden)

    Qureshi Rameesha

    2016-12-01

    Full Text Available The study aimed at analyzing the role of media during and after terrorist attacks by examining the media handling of APS Peshawar attack. The sample consisted of males and females selected on convenience basis from universities of Rawalpindi and Islamabad. It was hypothesized that (1 Extensive media coverage of terrorist attacks leads to greater publicity/recognition of terrorist groups (2 Media coverage of APS Peshawar attack increased fear and anxiety in public (3 Positive media handling/coverage of APS Peshawar attack led to public solidarity and peace. The results indicate that i Media coverage of terrorist attacks does help terrorist groups to gain publicity and recognition amongst public ii Media coverage of Aps Peshawar attack did not increase fear/anxiety in fact it directed the Pakistani nation towards public solidarity and peace.

  10. Angle-Resolved Spectroscopy of Parametric Fluorescence

    CERN Document Server

    Hsu, Feng-kuo

    2013-01-01

    The parametric fluorescence from a nonlinear crystal forms a conical radiation pattern. We measure the angular and spectral distributions of parametric fluorescence in a beta-barium borate crystal pumped by a 405-nm diode laser employing angle-resolved imaging spectroscopy. The experimental angle-resolved spectra and the generation efficiency of parametric down conversion are compared with a plane-wave theoretical analysis. The parametric fluorescence is used as a broadband light source for the calibration of the instrument spectral response function in the wavelength range from 450 to 1000 nm.

  11. Examination of Impact of Flooding attack on MANET and to accentuate on Performance Degradation

    Directory of Open Access Journals (Sweden)

    Bhuvaneshwari. K

    2013-01-01

    Full Text Available Mobile Adhoc Networks (MANET are new paradigm of wireless networks providing unrestricted mobility to nodes with no fixed or centralized infrastructure. Each node participating in the network acts as router to route the data from source to destination. This characteristic makes MANET more vulnerable to routing attacks. Flooding attack is one such attack which consumes more resource like bandwidth, battery power, etc. Reactive routing protocols like Adhoc On Demand Distance Vector (AODV and Dynamic Source Routing (DSR used in MANET has route discovery scheme and this makes it more easy for malicious node to launch flooding attack by flooding the route request packets(RREQ in the network. In this paper, the behavior of flooding attack and the performance impact of flooding attack on AODV protocol is studied. The NS2 network simulator is used to evaluate the impact of flooding attack on AODV.

  12. The attack navigator

    DEFF Research Database (Denmark)

    Probst, Christian W.; Willemson, Jan; Pieters, Wolter

    2016-01-01

    -technical system, the attack navigator identifies routes to an attacker goal. Specific attacker properties such as skill or resources can be included through attacker profiles. This enables defenders to explore attack scenarios and the effectiveness of defense alternatives under different threat conditions....... that are caused by the strategic behaviour of adversaries. Therefore, technology-supported methods are needed to help us identify and manage these risks. In this paper, we describe the attack navigator: a graph-based approach to security risk assessment inspired by navigation systems. Based on maps of a socio...

  13. Research on Coordinated Antisumarine Attack Effeciency of Two Helicopters Under Countermeasures

    Institute of Scientific and Technical Information of China (English)

    丁红岩; 董晓明; 蹇明裕

    2012-01-01

    The organization of coordinated attack and the selection of aiming point which affect hit probability were analyzed for the countermeasures taken by the hostile submarines at two helicopters' coordinated attack.A computational model of coordinated attack parameters,a model of submarine maneuver,and a model of noise jammer were established.Compared to single helicopter' torpedo attack,the coordinated attack of two helicopters can effectively increase the hit probability of torpedo and achieve the higher target detecting probability under counterwork condition.

  14. Statistical analysis of Contact Angle Hysteresis

    Science.gov (United States)

    Janardan, Nachiketa; Panchagnula, Mahesh

    2015-11-01

    We present the results of a new statistical approach to determining Contact Angle Hysteresis (CAH) by studying the nature of the triple line. A statistical distribution of local contact angles on a random three-dimensional drop is used as the basis for this approach. Drops with randomly shaped triple lines but of fixed volumes were deposited on a substrate and their triple line shapes were extracted by imaging. Using a solution developed by Prabhala et al. (Langmuir, 2010), the complete three dimensional shape of the sessile drop was generated. A distribution of the local contact angles for several such drops but of the same liquid-substrate pairs is generated. This distribution is a result of several microscopic advancing and receding processes along the triple line. This distribution is used to yield an approximation of the CAH associated with the substrate. This is then compared with measurements of CAH by means of a liquid infusion-withdrawal experiment. Static measurements are shown to be sufficient to measure quasistatic contact angle hysteresis of a substrate. The approach also points towards the relationship between microscopic triple line contortions and CAH.

  15. Mathematical Attacks on RSA Cryptosystem

    Directory of Open Access Journals (Sweden)

    Imad K. Salah

    2006-01-01

    Full Text Available In this paper some of the most common attacks against Rivest, Shamir, and Adleman (RSA cryptosystem are presented. We describe the integer factoring attacks, attacks on the underlying mathematical function, as well as attacks that exploit details in implementations of the algorithm. Algorithms for each type of attacks are developed and analyzed by their complexity, memory requirements and area of usage.

  16. Incidence angle normalization of radar backscatter data

    Science.gov (United States)

    NASA’s Soil Moisture Passive Active (SMAP) satellite (~2014) will include a radar system that will provide L-band multi-polarization backscatter at a constant incidence angle of 40º. During the pre-launch phase of the project there is a need for observations that will support the radar-based soil mo...

  17. Risk factors of transient ischemic attack: An overview.

    Science.gov (United States)

    Khare, Supreet

    2016-01-01

    Transient ischemic attack (TIA) is a transient episode of neurologic dysfunction caused due to loss of blood flow to the brain or spinal cord without acute infarction. Depending on the area of the brain involved, symptoms of TIA vary widely from patient to patient. Since the blockage period in TIA is very short-lived, there is no permanent damage. Risk factors for TIA include family history of stroke or TIA, age above 55 years or older, higher risk of TIA in males than females, high blood pressure, diabetes mellitus, and tobacco smoking. Genetics, race, and imbalance in lipid profile are other risk factors of TIA. TIA is usually diagnosed after taking a thorough history and a physical examination. Several radiological tests such as computed tomography and magnetic resonance imaging are useful in the evaluation of patients who have had a TIA. Ultrasound of the neck and an echocardiogram of the heart are other tests useful in the diagnosis and evaluation of the attack. The treatment following acute recovery from a TIA depends on the underlying cause. Patients who have more than 70% stenosis of the carotid artery, removal of atherosclerotic plaque is usually done by carotid endarterectomy surgery. One-third of the people with TIA can later have recurrent TIAs and one-third can have a stroke because of permanent nerve cell loss. Having a TIA is a risk factor for eventually having a stroke. Educating the patients and inculcating lifestyle modifications in them are initial steps to minimize the prevalence of transient ischemic attack.

  18. Risk factors of transient ischemic attack: An overview

    Directory of Open Access Journals (Sweden)

    Supreet Khare

    2016-01-01

    Full Text Available Transient ischemic attack (TIA is a transient episode of neurologic dysfunction caused due to loss of blood flow to the brain or spinal cord without acute infarction. Depending on the area of the brain involved, symptoms of TIA vary widely from patient to patient. Since the blockage period in TIA is very short-lived, there is no permanent damage. Risk factors for TIA include family history of stroke or TIA, age above 55 years or older, higher risk of TIA in males than females, high blood pressure, diabetes mellitus, and tobacco smoking. Genetics, race, and imbalance in lipid profile are other risk factors of TIA. TIA is usually diagnosed after taking a thorough history and a physical examination. Several radiological tests such as computed tomography and magnetic resonance imaging are useful in the evaluation of patients who have had a TIA. Ultrasound of the neck and an echocardiogram of the heart are other tests useful in the diagnosis and evaluation of the attack. The treatment following acute recovery from a TIA depends on the underlying cause. Patients who have more than 70% stenosis of the carotid artery, removal of atherosclerotic plaque is usually done by carotid endarterectomy surgery. One-third of the people with TIA can later have recurrent TIAs and one-third can have a stroke because of permanent nerve cell loss. Having a TIA is a risk factor for eventually having a stroke. Educating the patients and inculcating lifestyle modifications in them are initial steps to minimize the prevalence of transient ischemic attack.

  19. Incidence and impact of dog attacks on guide dogs in the UK.

    Science.gov (United States)

    Brooks, A; Moxon, R; England, G C W

    2010-06-19

    In a retrospective survey, researchers identified 100 incidents of attacks on guide dogs by other dogs. These were reviewed in order to determine the number, severity and impact on the handler and dog, and the characteristics of the aggressors and victims. During the study period there were more than three attacks reported each month, with 61 per cent of the attacks being upon dogs that were in harness and working with an owner or trainer. The majority of the dogs that were attacked were male (62 per cent), and the breeds that were over-represented (relative to their prevalence in the general guide dog population) were the labrador and the golden retriever x flat-coated retriever crossbreed. Most of the attacks occurred in public places between 09.00 and 15.00 and the majority (61 per cent) of the attacking dogs were off the lead at the time of the attack. Thirty-eight per cent of the attacking dogs were of bull breeds, which were over-represented among attackers compared with the proportion of this breed type in the general dog population. Veterinary attention was sought after 41 per cent of the attacks, and in 19 per cent of instances there was injury to the handler or to a member of the public. The attacks were reported to have affected the working performance and behaviour of the victim dog in 45 per cent of the instances, and two dogs had to be subsequently withdrawn from working as guide dogs.

  20. Nonlinear analysis of NPP safety against the aircraft attack

    Science.gov (United States)

    Králik, Juraj; Králik, Juraj

    2016-06-01

    The paper presents the nonlinear probabilistic analysis of the reinforced concrete buildings of nuclear power plant under the aircraft attack. The dynamic load is defined in time on base of the airplane impact simulations considering the real stiffness, masses, direction and velocity of the flight. The dynamic response is calculated in the system ANSYS using the transient nonlinear analysis solution method. The damage of the concrete wall is evaluated in accordance with the standard NDRC considering the spalling, scabbing and perforation effects. The simple and detailed calculations of the wall damage are compared.

  1. Postangioedema attack skin blisters: an unusual presentation of hereditary angioedema.

    Science.gov (United States)

    Wiesen, Jonathan; Gonzalez-Estrada, Alexei; Auron, Moises

    2014-04-10

    Hereditary angioedema (HAE) is an autosomal dominant disorder characterised by attacks of self-limited swelling affecting extremities, face and intra-abdominal organs, most often caused by mutations in the C1-inhibitor gene with secondary Bradykinin-mediated increased vascular permeability. We describe a 36-year-old man with a history of HAE who presented with painful interdigital bullae secondary to an acute oedema exacerbation. Biopsy and cultures of the lesions were negative and they resolved spontaneously. It is important to highlight and recognise the development of oedema blisters after resolution of a flare of HAE (only 1 previous case report), and hence avoid unnecessary dermatological diagnostic workup and treatment.

  2. Experimental Validation of the Invariance of Electrowetting Contact Angle Saturation

    NARCIS (Netherlands)

    Chevalliot, S.; Dhindsa, M.; Kuiper, S.; Heikenfeld, J.

    2011-01-01

    Basic electrowetting theory predicts that a continued increase in applied voltage will allow contact angle modulation to zero degrees. In practice, the effect of contact angle saturation has always been observed to limit the contact angle modulation, often only down to a contact angle of 60 to 70°.

  3. Measurement of the angle alpha at BABAR

    CERN Document Server

    Pérez, A

    2009-01-01

    We present recent measurements of the CKM angle alpha using data collected by the BABAR detector at the PEP-II asymmetric-energy e^+e^- collider at the SLAC National Accelerator Laboratory, operating at the Upsilon(4S) resonance. We present constraints on alpha from B->pipi, B->rhorho and B->rhopi decays.

  4. Design and Analysis of an Attack Resilient and Adaptive Medium access Control Protocol for Computer Networks

    CERN Document Server

    Shukla, Piyush Kumar; Bhadoria, Dr Sarita Singh

    2009-01-01

    The challenge of designing an efficient Medium Access Control (MAC) protocol and analyzing it has been an important research topic for over 30 years. This paper focuses on the performance analysis (through simulation) and modification of a well known MAC protocol CSMA/CD. The existing protocol does not consider the wastage of bandwidth due to unutilized periods of the channel. By considering this fact, performance of MAC protocol can be enhanced. The purpose of this work is to modify the existing protocol by enabling it to adapt according to state of the network. The modified protocol takes appropriate action whenever unutilized periods detected. In this way, to increase the effective bandwidth utilization and determine how it behaves under increasing load, and varying packet sizes. It will also include effects of attacks i.e. Denial of service attacks, Replay Attack, Continuous Channel Access or Exhaustion attack, Flooding attack, Jamming (Radio interference) attack, Selective forwarding attack which degrade...

  5. Cultural Memory of Sorrow in Advertising after the Terrorist Attacks

    Directory of Open Access Journals (Sweden)

    Esther Martínez Pastor

    2015-09-01

    Full Text Available The general objective of this research study is to do a comparative research to investigate the perception of sorrow in the advertising in the press after the terrorist attacks: 11/09/2001 (U.S. and 11/04/2004 (Spain. The general hypothesis considers that there are similar perceptions of the sorrow towards the ads although there are cultural differences. On a computer program the subject was shown these images about announcement advertisement published in the press after the 09/11 and 11/04 in a random order and was asked different questions that explored their perception and attitudes with regard to these advertisements

  6. Magnetic resonance colonography in severe attacks of ulcerative colitis

    Energy Technology Data Exchange (ETDEWEB)

    Savoye-Collet, C.; Roset, J.B.; Koning, E.; Dacher, J.N. [Rouen University Hospital Charles Nicolle, Radiology Department - QUANTIF - LITIS EA 4108, Rouen (France); Charpentier, C.; Hommel, S.; Lerebours, E.; Savoye, G. [Rouen University Hospital Charles Nicolle, Gastroenterology Department - ADEN U 1073, Rouen (France)

    2012-09-15

    To evaluate the ability of MR colonography (MRC) to detect lesions in severe attacks of ulcerative colitis (UC) and to assess its concordance with rectosigmoidoscopy. Eighteen patients underwent MRC and rectosigmoidoscopy. MRC consisted of a water-filled colonic procedure followed by T1/T2w images. Image quality was recorded. Inflammatory lesions and the existence of signs of severity were analysed. We calculated MR accuracy in the diagnosis of inflammatory lesions, as well as per segment and per patient concordance depending on the presence or absence of severe lesions. The MR image quality of the 108 segments was satisfactory. Endoscopy was used to study 36 segments (rectum and sigmoid). MRC had a positive predictive value of 100% and a sensitivity of 64% in the diagnosis of inflammatory lesions. Concordance for the diagnosis of severe lesions was excellent for the rectum (k = 0.85) and good for the sigmoid (k = 0.64). MRC diagnosed signs of severity in all patients affected at endoscopy. MRC also disclosed signs of severity located higher in the colon in four patients with nonsevere lesions at rectosigmoidoscopy. MRC can accurately diagnose inflammatory lesions in severe attacks of UC and significantly correlates with rectosigmoidoscopy in the diagnosis of severe lesions. (orig.)

  7. Detection of malicious attacks by Meta classification algorithms

    Directory of Open Access Journals (Sweden)

    G.Michael

    2015-03-01

    Full Text Available We address the problem of malicious node detection in a network based on the characteristics in the behavior of the network. This issue brings out a challenging set of research papers in the recent contributing a critical component to secure the network. This type of work evolves with many changes in the solution strategies. In this work, we propose carefully the learning models with cautious selection of attributes, selection of parameter thresholds and number of iterations. In this research, appropriate approach to evaluate the performance of a set of meta classifier algorithms (Ad Boost, Attribute selected classifier, Bagging, Classification via Regression, Filtered classifier, logit Boost, multiclass classifier. The ratio between training and testing data is made such way that compatibility of data patterns in both the sets are same. Hence we consider a set of supervised machine learning schemes with meta classifiers were applied on the selected dataset to predict the attack risk of the network environment . The trained models were then used for predicting the risk of the attacks in a web server environment or by any network administrator or any Security Experts. The Prediction Accuracy of the Classifiers was evaluated using 10-fold Cross Validation and the results have been compared to obtain the accuracy.

  8. Effect of target change during the simple attack in fencing.

    Science.gov (United States)

    Gutiérrez-Dávila, Marcos; Rojas, F Javier; Caletti, Matteo; Antonio, Raquel; Navarro, Enrique

    2013-01-01

    The aim of this study was to test the effect that changing targets during a simple long lunge attack in fencing exerts on the temporal parameters of the reaction response, the execution speed, and the precision and the coordination of the movement pattern. Thirty fencers with more than 10 years of experience participated in this study. Two force platforms were used to record the horizontal components of the reaction forces and thereby to determine the beginning of the movement. A three-dimensional (3D) system recorded the spatial positions of the 9 markers situated on the fencer plus the epee, while a moving target was projected on a screen, enabling the control of the target change. The results indicated that when a target change is provoked the reaction time (RT), movement time (MT), and the time used in the acceleration phase of the centre of mass (CM) increases significantly with respect to the attack executed with a straight thrust. The speed and horizontal distance reached by the CM at the end of the acceleration phase (VX(CM) and SX(CM), respectively) significantly decreased, while the errors increased. However, the temporal sequence of the movement pattern did not appreciably change.

  9. Microstructural Effects of Sulphate Attack in Sustainable Grouts for Micropiles

    Directory of Open Access Journals (Sweden)

    José Marcos Ortega Álvarez

    2016-11-01

    Full Text Available Nowadays, the use of micropiles has undergone a great development. In general, they are made with cement grout, reinforced with steel tubing. In Spain, these grouts are prepared using OPC, although the standards do not forbid the use of other cements, like sustainable ones. Micropiles are in contact with soils and groundwater, in which the presence of sulphates is common. Their deleterious effects firstly affect to the microstructure. Then, the aim of this research is to study the effects of sulphate attack in the microstructure of micropiles grouts, prepared with OPC, fly ash and slag commercial cements, compared to their behaviour when they are exposed to an optimum hardening condition. The microstructure evolution has been studied with the non-destructive impedance spectroscopy technique, which has never been used for detecting the effects of sulphate attack when slag and fly ash cements are used. Its results have been contrasted with mercury intrusion porosimetry and “Wenner” resistivity ones. The 28-day compressive strength of grouts has been also determined. The results of microstructure characterization techniques are in agreement, although impedance spectroscopy is the most sensitive for following the changes in the porous network of grouts. The results showed that micropiles made using fly ash and slag cements could have a good performance in contact with aggressive sodium sulphate media, even better than OPC ones.

  10. Kinematical and EMG-classifications of a fencing attack.

    Science.gov (United States)

    Frère, J; Göpfert, B; Nüesch, C; Huber, C; Fischer, M; Wirz, D; Friederich, N F

    2011-01-01

    8 expert fencers were studied with a 3-dimensional motion analysis system. Each subject performed 10 flèche attacks toward a standardized target. Surface electromyography signals (EMG) were recorded of the deltoid pars clavicularis, infraspinatus and triceps brachii caput laterale muscles of the weapon arm. The recorded EMGs were averaged using EMG wavelet-transformation software. 4 phases were defined based on the arm kinematics and used to classify fencers into 2 groups. A first group of 4 fencers showed an early maximal elbow extension (Early MEE) whereas the second group presented a late maximal elbow extension (Late MEE). 2 EMG-classifications were based on this kinematical classification, one in the time-domain and the other in the frequency-domain by using the spherical classification. The time-domain EMG-classification showed a significantly ( P=0.03) higher normalized deltoid intensity for the Early MEE group (91 ± 18%) than the Late MEE group (36 ± 13%) in the attack phase. The spherical classification revealed that the activity of all the muscles was significantly classified (recognition rate 75%, P=0.04) between the 2 groups. This study of EMG and kinematics of the weapon upper limb in fencing proposes several classifications, which implies a relationship between kinematic strategies, muscular activations and fencing success.

  11. Target Localization Based on Angle of Arrivals

    Institute of Scientific and Technical Information of China (English)

    Yi-Chao Cao

    2007-01-01

    Mobile location using angle of arrival (AOA) measurements has received considerable attention. This paper presents an approximation of maximum likelihood estimator (MLE) for localizing a source based on AOA measurements. By introducing an intermediate variable, the nonlinear equations relating AOA estimates can be transformed into a set of equations which are linear in the unknown parameters. It is an approximate realization of the MLE. Simulations show that the proposed algorithm outperforms the previous contribution.

  12. Stability of Random Networks under Evolution of Attack and Repair

    Institute of Scientific and Technical Information of China (English)

    CHI Li-Ping; YANG Chun-Bin; CAI Xu

    2006-01-01

    With a simple model, we study the stability of random networks under the evolution of attack and repair. We introduce a new quantity, i.e. invulnerability I(s), to describe the stability of the system. It is found that the network can evolve to a stationary state. The stationary value Ic has a power-law dependence on the initial average degree , with the slope about -1.5. In the stationary state, the degree distribution is a normal distribution, rather than a typical Poisson distribution for general random graphs. The clustering coefficient in the stationary state is much larger than that in the initial state. The stability of the network depends only on the initial average degree , which increases rapidly with the decrease of .

  13. On accurate determination of contact angle

    Science.gov (United States)

    Concus, P.; Finn, R.

    1992-01-01

    Methods are proposed that exploit a microgravity environment to obtain highly accurate measurement of contact angle. These methods, which are based on our earlier mathematical results, do not require detailed measurement of a liquid free-surface, as they incorporate discontinuous or nearly-discontinuous behavior of the liquid bulk in certain container geometries. Physical testing is planned in the forthcoming IML-2 space flight and in related preparatory ground-based experiments.

  14. Multi-Level Parsing Based Approach Against Phishing Attacks With the Help of Knowledge Bases

    Directory of Open Access Journals (Sweden)

    Gaurav Kumar Tak

    2013-11-01

    Full Text Available The increasing use of internet all over the world,be it in households or in corporate firms, has ledto anunprecedented rise in cyber-crimes. Amongst these the major chunk consists of Internet attacks which arethe most popular and common attacks are carried over the internet. Generally phishing attacks, SSLattacks and some other hacking attacks are kept into this category. Security against these attacks isthemajor issue of internet security in today’s scenario where internet has very deep penetration. Internet hasno doubt made our lives very convenient. It has provided many facilities to us at penny’s cost. For instanceit has made communication lightning fast and that too at a very cheap cost. But internet can pose addedthreats for those users who are not well versed inthe ways of internet and unaware of the security risksattached with it. Phishing Attacks, Nigerian Scam,Spam attacks, SSL attacks and other hacking attacksaresome of the most common and recent attacks to compromise the privacy of the internet users. Many a timesif the user isn’t careful, then these attacks are able to steal the confidential information of user (orunauthorized access. Generally these attacks are carried out with the help of social networking sites,popular mail server sites, online chatting sites etc. Nowadays, Facebook.com, gmail.com, orkut.com andmany other social networking sites are facing thesesecurity attack problems.This paper discusses a Knowledge Base Compound approach which is based on query operations andparsing techniques to counter these internet attacks using the web browser itself. In this approach wepropose to analyze the web URLs before visiting theactual site, so as to provide security against webattacks mentioned above. This approach employs various parsing operations and query processing whichuse many techniques to detect the phishing attacksas well as other web attacks. The aforementionedapproach is completely based on operation through the

  15. Constitutive modeling of contact angle hysteresis.

    Science.gov (United States)

    Vedantam, Srikanth; Panchagnula, Mahesh V

    2008-05-15

    We introduce a phase field model of wetting of surfaces by sessile drops. The theory uses a two-dimensional non-conserved phase field variable to parametrize the Gibbs free energy of the three-dimensional system. Contact line tension and contact angle hysteresis arise from the gradient term in the free energy and the kinetic coefficient respectively. A significant advantage of this approach is in the constitutive specification of hysteresis. The advancing and receding angles of a surface, the liquid-vapor interfacial energy and three-phase line tension are the only required constitutive inputs to the model. We first simulate hysteresis on a smooth chemically homogeneous surface using this theory. Next we show that it is possible to study heterogeneous surfaces whose component surfaces are themselves hysteretic. We use this theory to examine the wetting of a surface containing a circular heterogeneous island. The contact angle for this case is found to be determined solely by the material properties at the contact line in accord with recent experimental data.

  16. Measurement of the angle alpha at BABAR

    Energy Technology Data Exchange (ETDEWEB)

    Perez, A.; /Orsay, LAL

    2009-06-25

    The authors present recent measurements of the CKM angle {alpha} using data collected by the BABAR detector at the PEP-II asymmetric-energy e{sup +}e{sup -} collider at the SLAC National Accelerator Laboratory, operating at the {Upsilon}(4S) resonance. They present constraints on {alpha} from B {yields} {pi}{pi}, B {yields} {rho}{rho} and B {yields} {rho}{pi} decays.

  17. Strategies of detecting Profile-injection attacks in E-Commerce Recommender System: A survey Partha

    Directory of Open Access Journals (Sweden)

    Sarathi Chakraborty,

    2015-12-01

    Full Text Available E-commerce recommender systems are vulnerable to different types of shilling attack where the attacker influences the recommendation procedure in favor of him by inserting fake user-profiles into the system. From one point of view, the attacks can be of type push or nuke-either to promote or to demote a product. On the other hand, attacks can be classified as high-knowledge or low-knowledge attack depending on the amount of system knowledge required for making the attack successful. Several research works have been done in the last two decades for defending attacks on recommender systems. In this paper, we have surveyed the major works done in this area by different researchers. After a brief explanation of different attack types and attack models, we discussed the attack detection strategies proposed by the researchers mainly under five categories- Generic and model specific attribute based, rating distribution based, outlier analysis based, statistical approach based and clustering based.

  18. Characteristic features of injuries due to shark attacks: a review of 12 cases.

    Science.gov (United States)

    Ihama, Yoko; Ninomiya, Kenji; Noguchi, Masamichi; Fuke, Chiaki; Miyazaki, Tetsuji

    2009-09-01

    Shark attacks on humans might not occur as often as is believed and the characteristic features of shark injuries on corpses have not been extensively reviewed. We describe the characteristic features of shark injuries on 12 corpses. The analysis of these injuries might reveal the motivation behind the attacks and/or the shark species involved in the attack. Gouge marks on the bones are evidence of a shark attack, even if the corpse is decomposed. Severance of the body part at the joints without a fracture was found to be a characteristic feature of shark injuries.

  19. Cooperating attackers in neural cryptography.

    Science.gov (United States)

    Shacham, Lanir N; Klein, Einat; Mislovaty, Rachel; Kanter, Ido; Kinzel, Wolfgang

    2004-06-01

    A successful attack strategy in neural cryptography is presented. The neural cryptosystem, based on synchronization of neural networks by mutual learning, has been recently shown to be secure under different attack strategies. The success of the advanced attacker presented here, called the "majority-flipping attacker," does not decay with the parameters of the model. This attacker's outstanding success is due to its using a group of attackers which cooperate throughout the synchronization process, unlike any other attack strategy known. An analytical description of this attack is also presented, and fits the results of simulations.

  20. AN ANALYSIS OF CURRENT COMPUTER NETWORK ATTACK PROCEDURES, THEIR MITIGATION MEASURES AND THE DEVELOPMENT OF AN IMPROVED DENIAL OF SERVICE (DoS ATTACK MODEL

    Directory of Open Access Journals (Sweden)

    IHEKWEABA OGECHI

    2013-04-01

    Full Text Available This paper presents the major network attack profiles, taxonomies, classification and identification frameworks. Further, current approaches for intrusion detection on networks were x-rayed though, with emphasis on Denial of Service (DoS attacks only. The concept of intelligent agents and subsequently adaptive systems was elucidated, the properties derived were used as a proof of concept, and then applied in the development of a model for an adaptive intelligent multi-agent for network protection, against denial of service attacks.

  1. Performance Analysis of AODV under Black Hole Attack through Use of OPNET Simulator

    CERN Document Server

    Esmaili, H A; gharaee, Hossein

    2011-01-01

    Mobile ad hoc networks (MANETs) are dynamic wireless networks without any infrastructure. These networks are weak against many types of attacks. One of these attacks is the black hole. In this attack, a malicious node advertises itself as having freshest or shortest path to specific node to absorb packets to itself. The effect of black hole attack on ad hoc network using AODV as a routing protocol will be examined in this research. Furthermore, we investigate solution for increasing security in these networks. Simulation results using OPNET simulator depict that packet delivery ratio in the presence of malicious nodes, reduces notably.

  2. The Oracle a New Intelligent Cooperative Strategy of Attacks on Trust and Reputation Systems

    Directory of Open Access Journals (Sweden)

    Janiszewski Marek

    2014-06-01

    Full Text Available The paper presents a new concept of attack on trust and reputation systems. The oracle attack could violate the security provided by some of the existing reputation systems. The formal model of the attack is presented in the article on the base of the reference trust model, provided by the author. The author has proved that this type of attack could be eficient. On the other hand, a sort of measures is provided in the paper which could be implemented in the reputation systems to overcome identified vulnerabilities, unfortunately at the cost of increase of system complication. The paper also provides a definition of intelligent strategies of attacks on trust and reputation systems based on cooperation of many malicious nodes and justifies why this type of attacks is a serious threat

  3. Detection and Modeling of Cyber Attacks with Petri Nets

    Directory of Open Access Journals (Sweden)

    Bartosz Jasiul

    2014-12-01

    Full Text Available The aim of this article is to present an approach to develop and verify a method of formal modeling of cyber threats directed at computer systems. Moreover, the goal is to prove that the method enables one to create models resembling the behavior of malware that support the detection process of selected cyber attacks and facilitate the application of countermeasures. The most common cyber threats targeting end users and terminals are caused by malicious software, called malware. The malware detection process can be performed either by matching their digital signatures or analyzing their behavioral models. As the obfuscation techniques make the malware almost undetectable, the classic signature-based anti-virus tools must be supported with behavioral analysis. The proposed approach to modeling of malware behavior is based on colored Petri nets. This article is addressed to cyber defense researchers, security architects and developers solving up-to-date problems regarding the detection and prevention of advanced persistent threats.

  4. Impact of Rushing attack on Multicast in Mobile Ad Hoc Network

    CERN Document Server

    Palanisamy, V

    2009-01-01

    A mobile ad hoc network (MANETs) is a self-organizing system of mobile nodes that communicate with each other via wireless links with no fixed infrastructure or centralized administration such as base station or access points. Nodes in a MANETs operate both as host as well as routers to forward packets for each other in a multihop fashion. For many applications in wireless networks, multicasting is an important and frequent communication service. By multicasting, since a single message can be delivered to multiple receivers simultaneously. It greatly reduces the transmission cost when sending the same packet to multiple recipients. The security issue of MANETs in group communications is even more challenging because of involvement of multiple senders and multiple receivers. At that time of multicasting, mobile ad hoc network are unprotected by the attacks of malicious nodes because of vulnerabilities of routing protocols. Some of the attacks are Rushing attack, Blackhole attack, Sybil attack, Neighbor attack ...

  5. Composite Dos Attack Model

    Directory of Open Access Journals (Sweden)

    Simona Ramanauskaitė

    2012-04-01

    Full Text Available Preparation for potential threats is one of the most important phases ensuring system security. It allows evaluating possible losses, changes in the attack process, the effectiveness of used countermeasures, optimal system settings, etc. In cyber-attack cases, executing real experiments can be difficult for many reasons. However, mathematical or programming models can be used instead of conducting experiments in a real environment. This work proposes a composite denial of service attack model that combines bandwidth exhaustion, filtering and memory depletion models for a more real representation of similar cyber-attacks. On the basis of the introduced model, different experiments were done. They showed the main dependencies of the influence of attacker and victim’s properties on the success probability of denial of service attack. In the future, this model can be used for the denial of service attack or countermeasure optimization.

  6. A Comparison of Link Layer Attacks on Wireless Sensor Networks

    CERN Document Server

    Mohammadi, Shahriar; 10.5121/jgraphhoc.2011.3103

    2011-01-01

    Wireless sensor networks (WSNs) have many potential applications [1, 5] and unique challenges. They usually consist of hundreds or thousands small sensor nodes such as MICA2, which operate autonomously; conditions such as cost, invisible deployment and many application domains, lead to small size and limited resources sensors [2]. WSNs are susceptible to many types of link layer attacks [1] and most of traditional networks security techniques are unusable on WSNs [2]; due to wireless and shared nature of communication channel, untrusted transmissions, deployment in open environments, unattended nature and limited resources [1]. So, security is a vital requirement for these networks; but we have to design a proper security mechanism that attends to WSN's constraints and requirements. In this paper, we focus on security of WSNs, divide it (the WSNs security) into four categories and will consider them, include: an overview of WSNs, security in WSNs, the threat model on WSNs, a wide variety of WSNs' link layer a...

  7. On Attack-Relevant Ranking of Network Features

    Directory of Open Access Journals (Sweden)

    Adel Ammar

    2015-11-01

    Full Text Available An Intrusion Detection System (IDS is an important component of the defense-in-depth security mechanism in any computer network system. For assuring timely detection of intrusions from millions of connection records, it is important to reduce the number of connection features examined by the IDS, using feature selection or feature reduction techniques. In this scope, this paper presents the first application of a distinctive feature selection method based on neural networks to the problem of intrusion detection, in order to determine the most relevant network features, which is an important step towards constructing a lightweight anomaly-based intrusion detection system. The same procedure is used for feature selection and for attack detection, which gives more consistency to the method. We apply this method to a case study, on KDD dataset and show its advantages compared to some existing feature selection approaches. We then measure its dependence to the network architecture and the learning database.

  8. Advances in the Management of Transient Ischaemic Attack and Stroke

    Directory of Open Access Journals (Sweden)

    Mayra J Montalvo

    2016-07-01

    Full Text Available Among many important advances in the management of transient ischaemic attack (TIA and stroke are: the updated definition of TIA; risk stratification scores for TIA; the urgent diagnostic and treatment process for TIA; thrombectomy treatment for large vessel occlusive ischaemic stroke; cryptogenic stroke evaluation and treatment, including long-term monitoring for paroxysmal atrial fibrillation; and strategies to improve outcomes for patients including mirror therapy for neglect and timing of mobilisation after stroke. Future research will focus on: antiplatelet strategies after TIA; selecting patients for treatment with recanalisation therapies in an extended time window; uncovering the cause of strokes previously defined as cryptogenic; and better defining the optimal timing and dose of mobilisation after stroke.

  9. Cerebral blood flow velocities are reduced during attacks of unilateral migraine without aura

    DEFF Research Database (Denmark)

    Thomsen, L L; Iversen, Helle Klingenberg; Olesen, J

    1995-01-01

    aura in 25 patients. Blood velocity in the middle cerebral artery was lower on the headache side (59 cm/s) than on the non-headache side (65 cm/s) during the migraine attack. No such difference was found outside of attack (65 cm/s both sides). The difference (headache side minus non-headache side......) was on average -6.1 cm/s during attack compared to -0.4 cm/s outside of attack (p = 0.01). Assuming that rCBF is unchanged during attacks of migraine without aura, our results suggest a 9% increase in middle cerebral artery lumen (cross-sectional area) on the affected side during unilateral attacks of migraine...... without aura. The findings, however, do not necessarily mean that arterial dilatation is the only or even the most significant cause of pain....

  10. Estimation of Anonymous Email Network Characteristics through Statistical Disclosure Attacks

    Science.gov (United States)

    Portela, Javier; García Villalba, Luis Javier; Silva Trujillo, Alejandra Guadalupe; Sandoval Orozco, Ana Lucila; Kim, Tai-Hoon

    2016-01-01

    Social network analysis aims to obtain relational data from social systems to identify leaders, roles, and communities in order to model profiles or predict a specific behavior in users’ network. Preserving anonymity in social networks is a subject of major concern. Anonymity can be compromised by disclosing senders’ or receivers’ identity, message content, or sender-receiver relationships. Under strongly incomplete information, a statistical disclosure attack is used to estimate the network and node characteristics such as centrality and clustering measures, degree distribution, and small-world-ness. A database of email networks in 29 university faculties is used to study the method. A research on the small-world-ness and Power law characteristics of these email networks is also developed, helping to understand the behavior of small email networks. PMID:27809275

  11. Attacks and intrusion detection in wireless sensor networks of industrial SCADA systems

    Science.gov (United States)

    Kamaev, V. A.; Finogeev, A. G.; Finogeev, A. A.; Parygin, D. S.

    2017-01-01

    The effectiveness of automated process control systems (APCS) and supervisory control and data acquisition systems (SCADA) information security depends on the applied protection technologies of transport environment data transmission components. This article investigates the problems of detecting attacks in wireless sensor networks (WSN) of SCADA systems. As a result of analytical studies, the authors developed the detailed classification of external attacks and intrusion detection in sensor networks and brought a detailed description of attacking impacts on components of SCADA systems in accordance with the selected directions of attacks.

  12. Research on recognition of ramp angle based on transducer

    Directory of Open Access Journals (Sweden)

    Wenhao GU

    2015-12-01

    Full Text Available Focusing on the recognition of ramp angle, the relationship between the signal of vehicle transducer and real ramp angle is studied. The force change of vehicle on the ramp, and the relationship between the body tilt angle and front and rear suspension scale is discussed. According to the suspension and tire deformation, error angle of the ramp angle is deduced. A mathematical model is established with Matlab/Simulink and used for simulation to generate error curve of ramp angle. The results show that the error angle increases with the increasing of the ramp angle, and the limit value can reach 6.5%, while the identification method can effectively eliminate this error, and enhance the accuracy of ramp angle recognition.

  13. Angle of arrival estimation using spectral interferometry

    Energy Technology Data Exchange (ETDEWEB)

    Barber, Z.W.; Harrington, C.; Thiel, C.W.; Babbitt, W.R. [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States); Krishna Mohan, R., E-mail: krishna@spectrum.montana.ed [Spectrum Lab, Montana State University, Bozeman, MT 59717 (United States)

    2010-09-15

    We have developed a correlative signal processing concept based on a Mach-Zehnder interferometer and spatial-spectral (S2) materials that enables direct mapping of RF spectral phase as well as power spectral recording. This configuration can be used for precise frequency resolved time delay estimation between signals received by a phased antenna array system that in turn could be utilized to estimate the angle of arrival. We present an analytical theoretical model and a proof-of-principle demonstration of the concept of time difference of arrival estimation with a cryogenically cooled Tm:YAG crystal that operates on microwave signals modulated onto a stabilized optical carrier at 793 nm.

  14. Case Studies of Attacks over Adaptive Modulation Based Tactical Software Defined Radios

    Directory of Open Access Journals (Sweden)

    David Fernandes Cruz Moura

    2012-01-01

    Full Text Available This paper presents case studies of attacks aimed at tactical software defined radios based on a classification with the most common sources of vulnerabilities, classes of attacks, and types of intrusions that military radio sets may suffer. Besides that, we also describe how attack mitigation strategies can impact the development of SDR infrastructures. By using such approach, we identify several possible sources of vulnerabilities, attacks, intrusions, and mitigation strategies, illustrating them onto typical tactical radio network deployment scenarios, as an initial and necessary step for the definition of realistic and relevant security requirements for military software defined radio applications.

  15. Incidence and impact of dog attacks on guide dogs in the UK: an update.

    Science.gov (United States)

    Moxon, R; Whiteside, H; England, G C W

    2016-04-09

    Data on dog attacks on Guide Dogs' stock were reviewed to investigate the characteristics of the attacks. An average of 11.2 attacks occurred each month. Nearly all of the attacks occurred in public areas, 68.4 per cent of victim dogs were qualified guide dogs and 55.5 per cent of victim dogs were working in harness when they were attacked. Guide Dogs' stock were injured in 43.2 per cent of attacks and veterinary costs for attacks were estimated at £34,514.30. Over 40 per cent of qualified guide dogs' working ability was affected and >20 per cent of qualified guide dogs required some time off from working after a dog attack. Twenty dogs were permanently withdrawn from the Guide Dogs' programme as a result of dog attacks, 13 of which were qualified and working with guide dog owners at the time of the withdrawal; this resulted in a financial cost of >£600,000 to the charity. More importantly perhaps, temporary and permanent withdrawals have a significant impact upon the mobility and independence of guide dog owners and in many cases significantly impacted their emotional well-being.

  16. MECH: Algorithms and Tools for Automated Assessment of Potential Attack Locations (Software User Guide)

    Science.gov (United States)

    2015-10-02

    a Halo,” or MECH, is an analytical abstraction to model the locational relationships between a target and its attackers (around the route) in...line) A range for M/C points to see the target continuously move along the route to the attack engagement location E. Device Triggering Range (yellow...Behaviors in Tactical Planning (Views 3,4 of Figure 2.5) Attackers go through formal or informal optimization (i.e., prioritization , trade off choices) of

  17. An effective Denial of Service Attack Detection Method in Wireless Mesh Networks

    Science.gov (United States)

    Luan, Liangyu; Fu, Yingfang; Xiao, Peng

    In order to detect the DoS attack (Denial-of-Service attack) when wireless mesh networks adopt AODV routing protocol of Ad Hoc networks. Such technologies as an end-to-end authentication, utilization rate of cache memory, two pre-assumed threshold value and distributed voting are used in this paper to detect DoS attacker, which is on the basic of hierarchical topology structure in wireless mesh networks. Through performance analysis in theory and simulations experiment, the scheme would improve the flexibility and accuracy of DoS attack detection, and would obviously improve its security in wireless mesh networks.

  18. Adaptive Consensus of Distributed Varying Scale Wireless Sensor Networks under Tolerable Jamming Attacks

    Directory of Open Access Journals (Sweden)

    Jinping Mou

    2013-01-01

    Full Text Available Consensus problem is investigated for a varying scale wireless sensor network (VSWSN under tolerable jamming attacks, where the scale of the network is increasing or decreasing due to the newly joined nodes or the removed nodes, respectively; the tolerable jamming attack means that the attack strength is limited. It supposes that during the communications, all nodes may encounter with the tolerable jamming attacks; when the attack power is larger than the given value, the attacked nodes fall asleep, or otherwise the nodes are awakened. Under the sleep method, based on the Lyapunov method, it shows that if the communicating graph is the global limited intersectional connection (GLI connection and the system has the enough dwell time in the intersectional topology, then under the designed consensus protocol, all nodes achieve the global average consensus.

  19. A simple coherent attack and practical security of differential phase shift quantum cryptography

    Science.gov (United States)

    Kronberg, D. A.

    2014-02-01

    The differential phase shift quantum key distribution protocol reveals good security against such powerful attacks as unambiguous state discrimination and beam splitting attacks. Its complete security analysis is complex due to high dimensions of the supposed spaces and density operators. In this paper, we consider a particular and conceptually simple coherent attack, available in practical implementations. The main condition for this attack is the length of used coherent state tuples of order 8-12. We show that under this condition, no high level of practical distance between legitimate users can be achieved.

  20. Characteristics of acute pain attacks in patients with irritable bowel syndrome meeting Rome III criteria

    DEFF Research Database (Denmark)

    Hellström, P.M.; Saito, Y.A.; Bytzer, P.;

    2011-01-01

    Objectives: An international multicenter, prospective, non-interventional, 2-month study characterized acute pain attacks in patients with irritable bowel syndrome (IBS). Methods: Adult patients meeting the Rome III IBS diagnostic criteria with a history of 3 pain attacks per month participated...... in a survey that captured daily and episodic information regarding IBS symptoms and pain attacks for 2 months. Acute pain attacks were defined as a sudden onset or increase in the intensity of IBS abdominal pain with a minimum intensity of 4 (0-10 scale). Results: The majority (84%) of the 158 patients taking...

  1. Multi-Layer Approach for the Detection of Selective Forwarding Attacks.

    Science.gov (United States)

    Alajmi, Naser; Elleithy, Khaled

    2015-11-19

    Security breaches are a major threat in wireless sensor networks (WSNs). WSNs are increasingly used due to their broad range of important applications in both military and civilian domains. WSNs are prone to several types of security attacks. Sensor nodes have limited capacities and are often deployed in dangerous locations; therefore, they are vulnerable to different types of attacks, including wormhole, sinkhole, and selective forwarding attacks. Security attacks are classified as data traffic and routing attacks. These security attacks could affect the most significant applications of WSNs, namely, military surveillance, traffic monitoring, and healthcare. Therefore, there are different approaches to detecting security attacks on the network layer in WSNs. Reliability, energy efficiency, and scalability are strong constraints on sensor nodes that affect the security of WSNs. Because sensor nodes have limited capabilities in most of these areas, selective forwarding attacks cannot be easily detected in networks. In this paper, we propose an approach to selective forwarding detection (SFD). The approach has three layers: MAC pool IDs, rule-based processing, and anomaly detection. It maintains the safety of data transmission between a source node and base station while detecting selective forwarding attacks. Furthermore, the approach is reliable, energy efficient, and scalable.

  2. Multi-Layer Approach for the Detection of Selective Forwarding Attacks

    Directory of Open Access Journals (Sweden)

    Naser Alajmi

    2015-11-01

    Full Text Available Security breaches are a major threat in wireless sensor networks (WSNs. WSNs are increasingly used due to their broad range of important applications in both military and civilian domains. WSNs are prone to several types of security attacks. Sensor nodes have limited capacities and are often deployed in dangerous locations; therefore, they are vulnerable to different types of attacks, including wormhole, sinkhole, and selective forwarding attacks. Security attacks are classified as data traffic and routing attacks. These security attacks could affect the most significant applications of WSNs, namely, military surveillance, traffic monitoring, and healthcare. Therefore, there are different approaches to detecting security attacks on the network layer in WSNs. Reliability, energy efficiency, and scalability are strong constraints on sensor nodes that affect the security of WSNs. Because sensor nodes have limited capabilities in most of these areas, selective forwarding attacks cannot be easily detected in networks. In this paper, we propose an approach to selective forwarding detection (SFD. The approach has three layers: MAC pool IDs, rule-based processing, and anomaly detection. It maintains the safety of data transmission between a source node and base station while detecting selective forwarding attacks. Furthermore, the approach is reliable, energy efficient, and scalable.

  3. On resilience studies of system detection and recovery techniques against stealthy insider attacks

    Science.gov (United States)

    Wei, Sixiao; Zhang, Hanlin; Chen, Genshe; Shen, Dan; Yu, Wei; Pham, Khanh D.; Blasch, Erik P.; Cruz, Jose B.

    2016-05-01

    With the explosive growth of network technologies, insider attacks have become a major concern to business operations that largely rely on computer networks. To better detect insider attacks that marginally manipulate network traffic over time, and to recover the system from attacks, in this paper we implement a temporal-based detection scheme using the sequential hypothesis testing technique. Two hypothetical states are considered: the null hypothesis that the collected information is from benign historical traffic and the alternative hypothesis that the network is under attack. The objective of such a detection scheme is to recognize the change within the shortest time by comparing the two defined hypotheses. In addition, once the attack is detected, a server migration-based system recovery scheme can be triggered to recover the system to the state prior to the attack. To understand mitigation of insider attacks, a multi-functional web display of the detection analysis was developed for real-time analytic. Experiments using real-world traffic traces evaluate the effectiveness of Detection System and Recovery (DeSyAR) scheme. The evaluation data validates the detection scheme based on sequential hypothesis testing and the server migration-based system recovery scheme can perform well in effectively detecting insider attacks and recovering the system under attack.

  4. Enhancement of KaPoW Plugin to Defend Against DDoS Attacks

    Directory of Open Access Journals (Sweden)

    Farah Samir Barakat

    2016-06-01

    Full Text Available DDoS attack is one of the hardest attacks to detect and mitigate in the computer world. This paper introduces two quantitative models, which use the client puzzling to detect and thwart application DDoS attacks. We simulated the models to use the probabilistic metrics to penalize the malicious users and prevent them from launching a DDoS attack while offering a stable environment to the normal users and decreasing the number of false positives and false negatives.

  5. A Lanchester model of submarine attack on a carrier battlegroup

    OpenAIRE

    Eagle, James N.

    1987-01-01

    A Lanchester model is developed for a battlegroup ASW engagement. Two variations are included. In the first, long-range missile firing submarines, short-range missile or torpedo firing submarines, and submarines firing only torpedoes distribute their attack uniformly over battlegroup escort ships and carriers. In the second variation, the attack is concentrated on the carriers. supported by the Naval War College http://archive.org/details/lanchestermodelo00eagl NA

  6. An Assessment of User Response to Phishing Attacks: The Effects of Fear and Self-Confidence

    Science.gov (United States)

    House, Deanna

    2013-01-01

    Phishing attacks have threatened the security of both home users and organizations in recent years. Individuals of varying levels of computer proficiency are potential targets for a phishing attack; all that is needed is an email address and Internet access. Phishing uses social engineering to fraudulently obtain information that is confidential…

  7. Characterization of collective Gaussian attacks and security of coherent-state quantum cryptography.

    Science.gov (United States)

    Pirandola, Stefano; Braunstein, Samuel L; Lloyd, Seth

    2008-11-14

    We provide a simple description of the most general collective Gaussian attack in continuous-variable quantum cryptography. In the scenario of such general attacks, we analyze the asymptotic secret-key rates which are achievable with coherent states, joint measurements of the quadratures and one-way classical communication.

  8. Mechanism of hypothalamic paraventricular nucleus in regulating asthmatic attack

    Institute of Scientific and Technical Information of China (English)

    Jia Liu; Rong Dong; Jian Xiao; Nina Liu

    2006-01-01

    BACKGROUD: It has been confirmed that c-fos expession increased markedly in hypothalamic paraventricular nucleus(PVN)during asthmatic attack in rats,and PVN has extensive physiological functions,involving in the regulation of respiratory system,etc.OBJECTIVE: To observe the alteration of electroencephalogram(EEG)and power spectra in PVN during the asthmatic attack,and the alteraiton of lung function and diaphragmatic muscle discharge after bilateral PVN lesion in asthmatic rats.DESIGN:A randomized control study.SETTING: Laboratory of Physiology and Pharmacology,School of Basic Medical Sciences,Southeast University.MATERIALS: Forty-eight male adult SD rats of 260-300g were used.The rats were randomly divided into 6 groups(n=8):control group,asthma group,electrolytic lesion of PVN group,KA-induced lesion of PVN group,sham electrolytic lesion of PVN group and sham kainic acid(KA)-induced lesion of PVN group.KA,chicken ovalbumin and aluminum hydroxide were purchased from American Sigma Company.Bordetella pertrssis vaccine (Institute of Biological Products of Shanghai);stereotaxic apparartus (Jianwan Ⅱ,China);Iesion-producing device (YC-2 programmable stimulato,Chengdu Iustrument Company);MD2000 signal processing system(Nanjing Medical School); data acquisition system (RM6240B,Chengdu Instrument Company).METHODS:The experiments were carried out in the Laboratory of Physiology and Pharmacology,School of Basic Medical Sciences,Southeast University from January to August in 2006.①Rats except for control group were sensitized with an intraperitoneal injection of 100 mg chicken ovalbumin and 100 mg aluminum hydroxide and Bordetella pertussis vaccine containing 5×109 heat-killed in 1 mL of sterile saline.From the fifteenth to seventeenth days rats received three times aerosolized ovalbumin challenge. In rats of the control group and asthma group three steel electrodes were placed into the left PVN(AP-1.8 mm,LR 0.4 mm,OH-7.9 mm).parietal cortex and subcutaneous tissue in

  9. Indirect Speculative Attacks and the Black Market for Foreing Exchange: The Example of Sudan Indirect Speculative Attacks and the Black Market for Foreing Exchange: The Example of Sudan

    OpenAIRE

    1993-01-01

    Indirect Speculative Attacks and the Black Market for Foreing Exchange: The Example of Sudan The paper extends the recent literature on collapsing exchange roles and balance of payment crises to the case when currency inconvertibility gives rise to the emergence of an "illegal" black market. The presence of the black market generates indirect speculative attacks on the official reserves because, due to inconvertibility, agents cannot directly buy official reserves. The paper derives several c...

  10. Help-Seeking Behaviours of Adolescents in Relation to Terrorist Attacks: The Perceptions of Israeli Parents

    Science.gov (United States)

    Tatar, Moshe; Amram, Sima; Kelman, Talia

    2011-01-01

    Exposure to terrorism poses a challenge for children and adolescents as well as parents. For many years, Israeli citizens have been exposed to ongoing terrorist attacks. The present article is aimed at revealing the reactions of Israeli parents when facing terrorist attacks and their perceptions regarding the help-seeking behaviours of their…

  11. A Hydrodynamic Model of Dynamic Contact Angle Hysteresis.

    Science.gov (United States)

    contact angle hysteresis is developed in terms of the interaction of capillary, viscous, and...used to obtain the equations which describe the contact angle region and thereby to define the dynamic contact angle . The analysis is limited to...velocity dependence of the receding contact angle and of the thickness of the deposited film of the receding interface of a wetting liquid are determined as functions of the capillary, viscous, and disjoining forces.

  12. Empirical Analysis of Virtual Carrier Sense Flooding Attacks Over Wireless Local Area Network

    Directory of Open Access Journals (Sweden)

    Mina Malekzadeh

    2009-01-01

    Full Text Available Problem statement: Wireless Local Areas (WLANs are subject to different types of vulnerabilities. Denial of Service (DoS attack is the most current challenging issue on the WLANs. The objectives of the study were to (i Provide an empirical analysis to conduct a series of wireless virtual carrier sense DoS attacks using wireless control frames vulnerabilities, (ii Design a testbed to compared and analyzed the damage that these attacks can imposed on wireless networks, and (iii Evaluated the effectiveness of such attacks on performance of WLAN in term of data transmission rate. Approach: The testbed employed ubuntu distribution along a network analyzer, Atheros chipset, and frame injection to the tested WLAN. All experiments were placed on two phases: Targeting wireless access point and targeting wireless client. Each phase presented the results of experiments under three circumstances: Before, during, and after the attacks. Results: Even when virtual carrier sense communication was disabled in the tested WLAN, still the target nodes answered to these forgery frames which made the attacks easier. Attacks over the wireless clients were more effective than the access point. In VCS-RTS-C the rate of data transmission from 3547.384 B sec1 decreased to 9.185 B sec1. In contrast with VCS-CTS-C, it decreased from 4959.887-44.740 B sec1 and amount of decrease for VCS-ACK-C was from 7057.401-136.96 B sec1. The obtained results demonstrated that during the attacks the target clients were completely disconnected from the wireless network and unable to do any communication. Conclusion: The influence of wireless virtual carrier sense attacks on performance of the wireless network was analyzed. The data transmission rate of the tested WLAN under the attacks was compared with the transmission rate of the WLAN operated under normal conditions. The obtained results confirmed the attacks could easily overwhelmed and shut down the wireless network.

  13. Rare lesions of the cerebellopontine angle.

    Science.gov (United States)

    Yilmaz, Cem; Altinors, Nur; Sonmez, Erkin; Gulsen, Salih; Caner, Hakan

    2010-07-01

    Vestibular schwannomas, meningiomas and epidermoids account for a vast majority of the lesions occurring in the cerebellopontine angle (CPA). Neoplastic and non-neoplastic pathologies other than these tumors constitute 1% of all lesions located in the CPA. The aim of this study was to reveal our experience in the treatment of the rare lesions of the CPA. We have retrospectively reviewed the medical files and radiological data of all patients who underwent surgery involving any kind of pathology in the CPA. We have excluded those patients with a histopathological diagnosis of meningioma, schwannoma and epidermoids. Our research revealed a case of craniopharyngioma, a case of chloroma, a case of solitary fibrous tumor, a case of pinealoblastoma, a case of atypical teratoid rhabdoid tumor, a case of an aneurysm, a case of hemorrhage and a case of abscess.

  14. Effect of hydrogen attack on acoustic emission behavior of low carbon steel

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    In order to investigate the effect of hydrogen attack degree on acoustic emission (AE) behavior of low carbon steel during tensiling, specimens made of low carbon steel was exposed to hydrogen gas of 18 MPa at 450 and 500℃ for 240, 480 and 720 h respectively. Experimental results show that with increase of the hydrogen attack degree, the totally AE activity decreases during tensiling. In addition, the count of AE signals with high amplitude for the specimens with hydrogen attack keeps a constant which is less than that without hydrogen attack. It is concluded that AE signals originate in the specimens with hydrogen attack from intergranular fracture induced by methane blisterings or/and microcracks on grain boundaries.

  15. High Order Differential Attack and Trace Attack to Block Ciphers

    Institute of Scientific and Technical Information of China (English)

    HU Yupu; CHEN Kai; Xiao Guozhen

    2001-01-01

    In this paper, we prove a high or-der differential property of power function, then giverespectively high order differential attack and traceattack to block ciphers. These attacks depend onlyon block cipher's algebraic shape on GF(2n) and haveno relation with its designing structure. The condi-tions are given for both effective attacks and strengthagainst attacks.

  16. Application of stochastic discrete event system framework for detection of induced low rate TCP attack.

    Science.gov (United States)

    Barbhuiya, F A; Agarwal, Mayank; Purwar, Sanketh; Biswas, Santosh; Nandi, Sukumar

    2015-09-01

    TCP is the most widely accepted transport layer protocol. The major emphasis during the development of TCP was its functionality and efficiency. However, not much consideration was given on studying the possibility of attackers exploiting the protocol, which has lead to several attacks on TCP. This paper deals with the induced low rate TCP attack. Since the attack is relatively new, only a few schemes have been proposed to mitigate it. However, the main issues with these schemes are scalability, change in TCP header, lack of formal frameworks, etc. In this paper, we have adapted the stochastic DES framework for detecting the attack, which addresses most of these issues. We have successfully deployed and tested the proposed DES based IDS on a test bed.

  17. Angioedema attacks in patients with hereditary angioedema : Local manifestations of a systemic activation process

    NARCIS (Netherlands)

    Hofman, Zonne L M; Relan, Anurag; Zeerleeder, Sacha; Drouet, Christian; Zuraw, Bruce; Hack, C. Erik

    2016-01-01

    Hereditary angioedema (HAE) caused by a deficiency of functional C1-inhibitor (C1INH) becomes clinically manifest as attacks of angioedema. C1INH is the main inhibitor of the contact system. Poor control of a local activation process of this system at the site of the attack is believed to lead to th

  18. The Role of Initial Attack and Performer Expertise on Instrument Identification

    Science.gov (United States)

    Cassidy, Jane W.; Schlegel, Amanda L.

    2016-01-01

    The purpose of this study was to examine the role initial attack and expertise play in the identification of instrumental tones. A stimulus CD was made of 32 excerpts of instrumental tones. Sixteen possible combinations of the variables of initial attack (present or absent), expertise (beginner versus professional), and timbre (flute, clarinet,…

  19. Attack Coverage in High-Level Men’s Volleyball: Organization on the Edge of Chaos?

    Directory of Open Access Journals (Sweden)

    Laporta Lorenzo

    2015-09-01

    Full Text Available Change is pervasive, but emerging patterns are occasionally detectable through analysis of systemic behaviors. Match analysis uses these patterns in order to reduce the degree of improvisation and to optimize the training process. However, it is possible that certain game phases elude systematic patterning. In this vein, our aim was to analyze the case of attack coverage in men’s volleyball, as we suspected it would elude systematic patterning and has received negligible attention in scientific research. We analyzed the occurrence of attack coverage in 4544 plays of the 2011 Volleyball World League. A Chi-square test with residual adjusted values was applied to explore significant associations between variables. A Monte Carlo correction was applied, as some cells had n<5. Effect sizes were determined using Cramer’s V. Overall, attack coverage occurred in 3.89% of ball possessions, and 23 distinct structures emerged. These structures lacked significant associations with the game complex, setting zone, and effect of attack coverage. Conversely, attack coverage structures showed significant associations with the attack zone and tempo, with very strong effect sizes (V=0.472 and V=0.521, respectively. As certain attack zones are deeply associated with attack tempo, it is apparent that quicker attack plays affect attack coverage structuring, promoting the formation of less complex structures. Ultimately, attack coverage structures seem to depend on momentary constraints, thereby rendering rigid systematization impracticable. Still, we contended that a principle-based approach might be suitable. This invites researchers to rethink how to interpret game regularities.

  20. INFLUENCE OF SURFACE-ROUGHNESS ON THE WETTING ANGLE

    NARCIS (Netherlands)

    Zhou, X.B; de Hosson, J.T.M.

    1995-01-01

    In this paper the influence of surface roughness on contact angles in the system of liquid Al wetting solid surfaces of Al2O3 has been studied. It was observed that contact angles of liquid Al vary significantly on different rough surfaces of Al2O3 A model is proposed to correlate contact angles wit

  1. Distinguishing features of shallow angle plunging jets

    Science.gov (United States)

    Deshpande, Suraj S.; Trujillo, Mario F.

    2013-08-01

    Numerical simulations employing an algebraic volume-of-fluid methodology are used to study the air entrainment characteristics of a water jet plunging into a quiescent water pool at angles ranging from θ = 10° to θ = 90° measured from the horizontal. Our previous study of shallow angled jets [S. S. Deshpande, M. F. Trujillo, X. Wu, and G. L. Chahine, "Computational and experimental characterization of a liquid jet plunging into a quiescent pool at shallow inclination," Int. J. Heat Fluid Flow 34, 1-14 (2012)], 10.1016/j.ijheatfluidflow.2012.01.011 revealed the existence of a clearly discernible frequency of ingestion of large air cavities. This is in contrast with chaotic entrainment of small air pockets reported in the literature in case of steeper or vertically plunging jets. In the present work, the differences are addressed by first quantifying the cavity size and entrained air volumes for different impingement angles. The results support the expected trend - reduction in cavity size (D43) as θ is increased. Time histories of cavity volumes in the vicinity of the impingement region confirm the visual observations pertaining to a near-periodic ingestion of large air volumes for shallow jets (10°, 12°), and also show that such cavities are not formed for steep or vertical jets. Each large cavity (defined as Dc/Dj ≳ 3) exists in close association with a stagnation point flow. A local mass and momentum balance shows that the high stagnation pressure causes a radial redirection of the jet, resulting in a flow that resembles the initial impact of a jet on the pool. In fact, for these large cavities, their speed matches closely Uimpact/2, which coincides with initial cavity propagation for sufficiently high Froude numbers. Furthermore, it is shown that the approximate periodicity of air entrainment scales linearly with Froude number. This finding is confirmed by a number of simulations at θ = 12°. Qualitatively, for steeper jets, such large stagnation

  2. Studying of the Contact Angle Hysteresis on Various Surfaces

    OpenAIRE

    Kirichenko E. O.; Gatapova E. Ya.

    2016-01-01

    This paper is devoted to investigation of the contact angle hysteresis on various surfaces. It was carried out by two different methods: measuring the advancing and the receding contact angles and measuring the contact angles at water droplet evaporation under isothermal conditions. Data obtained using two methods have been compared. The influence of the contact angle hysteresis on the mode of the drop evaporation has been shown.

  3. Studying of the Contact Angle Hysteresis on Various Surfaces

    Directory of Open Access Journals (Sweden)

    Kirichenko E. O.

    2016-01-01

    Full Text Available This paper is devoted to investigation of the contact angle hysteresis on various surfaces. It was carried out by two different methods: measuring the advancing and the receding contact angles and measuring the contact angles at water droplet evaporation under isothermal conditions. Data obtained using two methods have been compared. The influence of the contact angle hysteresis on the mode of the drop evaporation has been shown.

  4. Attacks by jaguars (Panthera onca) on humans in central Brazil: report of three cases, with observation of a death.

    Science.gov (United States)

    Neto, Manoel Francisco Campos; Garrone Neto, Domingos; Haddad, Vidal

    2011-06-01

    Conflicts between humans and big cats have been known for centuries throughout the world, but have intensified in recent decades. Recently, attacks by Panthera onca on humans in Brazil have been brought to the forefront through exposure in the press and because of the severity of the attacks. We report 3 cases of patients attacked by jaguars in provoked and predatory situations. Two patients survived the attacks and one died. Attack mechanisms and lesions in victims are discussed. The attacks demonstrate a real risk of accidents from jaguars in certain regions, such as the Pantanal and the Amazon.

  5. Booters - an analysis of DDoS-as-a-Service attacks

    NARCIS (Netherlands)

    Santanna, José Jair; Rijswijk-Deij, van Roland; Sperotto, Anna; Wierbosch, Mark; Zambenedetti Granville, Lisandro; Pras, Aiko; Badonnel, Remi; Xiao, Jin; Ata, Shingo; De Turck, Filip; Groza, Voicy; Santos, dos Carlos Raniery P.

    2015-01-01

    In 2012, the Dutch National Research and Education Network, SURFnet, observed a multitude of Distributed Denial of Service (DDoS) attacks against educational institutions. These attacks were effective enough to cause the online exams of hundreds of students to be cancelled. Surprisingly, these attac

  6. 3 CFR - Continuation of the National Emergency With Respect to Certain Terrorist Attacks

    Science.gov (United States)

    2010-01-01

    ... 3 The President 1 2010-01-01 2010-01-01 false Continuation of the National Emergency With Respect to Certain Terrorist Attacks Presidential Documents Other Presidential Documents Notice of September 10, 2009 Continuation of the National Emergency With Respect to Certain Terrorist Attacks Consistent with section 202(d) of the National...

  7. Security of Quantum-Readout PUFs against quadrature based challenge estimation attacks

    NARCIS (Netherlands)

    Skoric, B.; Mosk, A.P.; Pinkse, P.W.H.

    2013-01-01

    The concept of quantum-secure readout of Physical Unclonable Functions (PUFs) has recently been realized experimentally in an optical PUF system. We analyze the security of this system under the strongest type of classical attack: the challenge estimation attack. The adversary performs a measurement

  8. Assassination in the United States: an operational study of recent assassins, attackers, and near-lethal approachers.

    Science.gov (United States)

    Fein, R A; Vossekuil, B

    1999-03-01

    This study is the first operational exploration of the thinking and behavior of all 83 persons known to have attacked, or approached to attack, a prominent public official or public figure in the United States since 1949. In addition to data about each attack or near-attack and each subject's demographic and background characteristics, information was gathered about each subject's ideas and actions in the days and weeks before their attacks or near-lethal approaches. Questions were examined about each subject's movement from the idea of attack to actual attack, motives, selection of targets, planning, communication of threat and intent, symptoms of mental illness, and significant life experiences. In every case, the attack or near-attack was the end result of an understandable, and often discernible, process of thinking and action. Implications for protectors, investigators, and researchers are discussed.

  9. Attack or attacked: The sensory and fluid mechanical constraints of copepods’ predator–prey interactions

    DEFF Research Database (Denmark)

    Kiørboe, Thomas

    2013-01-01

    , and mechanisms for mobility of the parties involved. Here, I describe the mechanisms of sensing, escaping predators, and capturing prey in marine pelagic copepods. I demonstrate that feeding tradeoffs vary with feeding mode, and I describe simple fluid mechanical models that are used to quantify these tradeoffs...

  10. Major depressive disorder following terrorist attacks: A systematic review of prevalence, course and correlates

    Science.gov (United States)

    2011-01-01

    Background Terrorist attacks are traumatic events that may result in a wide range of psychological disorders for people exposed. This review aimed to systematically assess the current evidence on major depressive disorder (MDD) after terrorist attacks. Methods A systematic review was performed. Studies included assessed the impact of human-made, intentional, terrorist attacks in direct victims and/or persons in general population and evaluated MDD based on diagnostic criteria. Results A total of 567 reports were identified, 11 of which were eligible for this review: 6 carried out with direct victims, 4 with persons in general population, and 1 with victims and general population. The reviewed literature suggests that the risk of MDD ranges between 20 and 30% in direct victims and between 4 and 10% in the general population in the first few months after terrorist attacks. Characteristics that tend to increase risk of MDD after a terrorist attack are female gender, having experienced more stressful situations before or after the attack, peritraumatic reactions during the attack, loss of psychosocial resources, and low social support. The course of MDD after terrorist attacks is less clear due to the scarcity of longitudinal studies. Conclusions Methodological limitations in the literature of this field are considered and potentially important areas for future research such as the assessment of the course of MDD, the study of correlates of MDD or the comorbidity between MDD and other mental health problems are discussed. PMID:21627850

  11. Predicting Suicide Attacks: Integrating Spatial, Temporal, and Social Features of Terrorist Attack Targets

    Science.gov (United States)

    2013-01-01

    geocoded all returnees within the state of California and all mental health, substance abuse, and hospital facilities using GIS . The spatial information...themes. The data were then processed with SAS through regression analysis to identify key areas of concern. She used GIS to geocode and assign...criminal justice fields. She has developed expertise in using geographic information systems ( GIS ), ATLAS.ti, SAS, and GeoClip to perform a combination

  12. Detection and Discrimination of DDoS Attacks from Flash Crowd Using Entropy Variations

    Directory of Open Access Journals (Sweden)

    Pragya Katiyar

    2013-08-01

    Full Text Available Internet is a worldwide network that combines millions local to global scope, private public, academics, business, optical network technologies, government networks. It carries an expandable rangeof information resources and services which lead to bulk exchange of traffic over the Internet every day. This excessive popularity creates some troubles in the networks. Among them, Flash Crowd andDistributed Denial of Service (DDoS attacks are the two major events. Web services needs stability and security from these two concerns. There are some methods that can discriminate DDoS attack from flash crowd and trace the sources of the attack in huge volume of network traffic. However, it is difficult to detect the exact sources of DDoS attacks in network traffic when Flash crowd event is also present. Due to the alikeness of these two anomalies, attacker can easily mimic the malicious flow into legitimate traffic patterns and defence system cannot detect real sources of attack on time. In this paper, entropy variation, a theoretic parameter, is used to discriminate DDoS attack from Flash Crowd and trace the sources of theDDoS attack. Entropy variation is a theoretic concept which is a measure of changes in concentration of distribution of flows at a router for a given time duration. The proposed strategy is effective and efficiently scalable that has several advantages like memory non intensive, minimum overhead in terms of resources and time, and independent of traffic pattern.

  13. Computer simulation of dislocation core structure of metastable left angle 111 right angle dislocations in NiAl

    Energy Technology Data Exchange (ETDEWEB)

    Xie, Z.Y. (Dept. of Materials Science and Engineering, Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)); Vailhe, C. (Dept. of Materials Science and Engineering, Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States)); Farkas, D. (Dept. of Materials Science and Engineering, Virginia Polytechnic Inst. and State Univ., Blacksburg, VA (United States))

    1993-10-01

    The atomistic structure of dislocation cores of left angle 111 right angle dislocations in NiAl was simulated using embedded atom method potentials and molecular statics computer simulation. In agreement with previous simulation work and experimental observations, the complete left angle 111 right angle dislocation is stable with respect to the two superpartials of 1/2 left angle 111 right angle separated by an antiphase boundary. The structure of the latter configuration, though metastable, is of interest in the search for ways of improving ductility in this material. The structure of the complete dislocation and that of the metastable superpartials was studied using atomistic computer simulation. An improved visualization method was used for the representation of the resulting structures. The structure of the partials is different from that typical of 1/2 left angle 111 right angle dislocations in b.c.c. materials and that reported previously for the B2 structure using model pair potentials. (orig.)

  14. Clinical Characterization and Imaging of Triggered Attacks in Chronic Migraine and Posttraumatic Headache

    Science.gov (United States)

    2016-02-01

    research was to characterize clinical features and changes in brain metabolism associated with attacks of headache triggered by either nitroglycerin (NTG...These studies were not performed Task 6. Comparison of baseline brain connectivity and metabolism between patients with persistent posttraumatic...to develop human models of PTH by characterizing clinical features and correlated changes in brain activity before and during triggered attacks. The

  15. Denial-of-service attack detection based on multivariate correlation analysis

    NARCIS (Netherlands)

    Tan, Zhiyuan; Jamdagni, Aruna; He, Xiangjian; Nanda, Priyadarsi; Liu, Ren Ping; Lu, Bao-Liang; Zhang, Liqing; Kwok, James

    2011-01-01

    The reliability and availability of network services are being threatened by the growing number of Denial-of-Service (DoS) attacks. Effective mechanisms for DoS attack detection are demanded. Therefore, we propose a multivariate correlation analysis approach to investigate and extract second-order s

  16. 77 FR 56515 - Continuation of the National Emergency With Respect to Certain Terrorist Attacks

    Science.gov (United States)

    2012-09-12

    ..., 2012. [FR Doc. 2012-22708 Filed 9-11-12; 2:15 pm] Billing code 3295-F2-P ... With Respect to Certain Terrorist Attacks Notice of September 11, 2012--Continuation of the National... the National Emergency With Respect to Certain Terrorist Attacks Consistent with section 202(d) of...

  17. Evolution of Swarming Behavior Is Shaped by How Predators Attack.

    Science.gov (United States)

    Olson, Randal S; Knoester, David B; Adami, Christoph

    2016-01-01

    Animal grouping behaviors have been widely studied due to their implications for understanding social intelligence, collective cognition, and potential applications in engineering, artificial intelligence, and robotics. An important biological aspect of these studies is discerning which selection pressures favor the evolution of grouping behavior. In the past decade, researchers have begun using evolutionary computation to study the evolutionary effects of these selection pressures in predator-prey models. The selfish herd hypothesis states that concentrated groups arise because prey selfishly attempt to place their conspecifics between themselves and the predator, thus causing an endless cycle of movement toward the center of the group. Using an evolutionary model of a predator-prey system, we show that how predators attack is critical to the evolution of the selfish herd. Following this discovery, we show that density-dependent predation provides an abstraction of Hamilton's original formulation of domains of danger. Finally, we verify that density-dependent predation provides a sufficient selective advantage for prey to evolve the selfish herd in response to predation by coevolving predators. Thus, our work corroborates Hamilton's selfish herd hypothesis in a digital evolutionary model, refines the assumptions of the selfish herd hypothesis, and generalizes the domain of danger concept to density-dependent predation.

  18. Influence of higher order modes on angled-facet amplifiers

    DEFF Research Database (Denmark)

    Wang, Z.; Mikkelsen, B.; Stubkjær, Kristian

    1991-01-01

    The influence of the first-order mode on the residual reflectivity of angled-facet amplifiers is analyzed. For a 7 degrees angled-facet ridge waveguide amplifier with a single-layer antireflective (AR) coating, a gain ripple lower than 1-dB at 25-dB gain can be obtained independent...... by increasing the facet angles to 10 degrees...

  19. Seven Deadliest Wireless Technologies Attacks

    CERN Document Server

    Haines, Brad

    2010-01-01

    How can an information security professional keep up with all of the hacks, attacks, and exploits? One way to find out what the worst of the worst are is to read the seven books in our Seven Deadliest Attacks Series. Not only do we let you in on the anatomy of these attacks but we also tell you how to get rid of them and how to defend against them in the future. Countermeasures are detailed so that you can fight against similar attacks as they evolve. Attacks featured in this book include:Bluetooth AttacksCredit Card, Access Card, and Passport AttacksBad Encryption

  20. A Novel Metric For Detection of Jellyfish Reorder Attack on Ad Hoc Network

    Directory of Open Access Journals (Sweden)

    B. B. Jayasingh

    2010-01-01

    Full Text Available Ad Hoc networks are susceptible to many attacks due to its unique characteristics such as open network architecture, stringent resource constraints, shared wireless medium and highly dynamic topology. The attacks can be of different types out of which denial of service is one of the most difficult attacks to detect and defend. Jellyfish is a new denial of service attack that exploits the end to end congestion control mechanism of TCP (Transmission Control Protocol which has a very devastating effect on the throughput. The architecture for detection of such attack should be both distributed and cooperative to suit the needs of wireless ad-hoc networks that is every node in the wireless ad-hoc network should participate in the intrusion detection. We intend to develop an algorithm that detects the jellyfish attack at a single node and that can be effectively deployed at all other nodes in the ad hoc network. We propose the novel metric that detects the Jellyfish reorder attack based on the Reorder Density which is a basis for developing a metric. The comparison table shows the effectiveness of novel metric, it also helps protocol designers to develop the counter strategies for the attack.

  1. Formal reconstruction of attack scenarios in mobile ad hoc and sensor networks

    Directory of Open Access Journals (Sweden)

    Rekhis Slim

    2011-01-01

    Full Text Available Abstract Several techniques of theoretical digital investigation are presented in the literature but most of them are unsuitable to cope with attacks in wireless networks, especially in Mobile Ad hoc and Sensor Networks (MASNets. In this article, we propose a formal approach for digital investigation of security attacks in wireless networks. We provide a model for describing attack scenarios in a wireless environment, and system and network evidence generated consequently. The use of formal approaches is motivated by the need to avoid ad hoc generation of results that impedes the accuracy of analysis and integrity of investigation. We develop an inference system that integrates the two types of evidence, handles incompleteness and duplication of information in them, and allows possible and provable actions and attack scenarios to be generated. To illustrate the proposal, we consider a case study dealing with the investigation of a remote buffer overflow attack.

  2. ANM to Perceive and Thwart Denial of Service Attack in WLAN

    Directory of Open Access Journals (Sweden)

    Durairaj M

    2015-05-01

    Full Text Available Wireless infrastructure network is vulnerable to Denial of Service (DoS attack which makes the resources unavailable for its intended user. As an outcome of DoS attack, authenticated user is denied from accessing the network by spoofing legitimate client identity. Reduced protection in management frame led to MAC spoof DoS attack. Though 802.11w was developed to protect the management frame, the network is vulnerable to different DoS attacks and unable to prevent all types of DoS attacks. This motivated us to propose a mechanism to detect and prevent substantial number of DoS attacks. This paper proposes an algorithm called Alternative Numbering Mechanism (ANM which prevents DoS attacks. The proposed solution is simulated in NS2 for experimentation. Packet delivery ratio, control overhead, normalized routing overhead, delay time, throughput and packet drop were measured for experimentation and to evaluate the performance of ANM. The experimental results of ANM demonstrate that the performance of ANM is encouraging and prevents nearly all types of DoS attacks.

  3. A system for denial-of-service attack detection based on multivariate correlation analysis

    NARCIS (Netherlands)

    Tan, Zhiyuan; Jamdagni, Aruna; He, Xiangjian; Nanda, Priyadarsi; Liu, Ren Ping

    2014-01-01

    Interconnected systems, such as Web servers, database servers, cloud computing servers and so on, are now under threads from network attackers. As one of most common and aggressive means, denial-of-service (DoS) attacks cause serious impact on these computing systems. In this paper, we present a DoS

  4. Development of an Attack-Resistant and Secure SCADA System using WSN, MANET, and Internet

    Directory of Open Access Journals (Sweden)

    N. Rajesh kumar

    2014-06-01

    Full Text Available Industrial Control Systems (ICS are open to security attacks when they are integrated with IT systems and wireless technologies for enhanced processing and remote control. These Critical Infrastructures (CIs are highly important as they provide service for an entire nation and causes serious danger even when interrupted for a while. Some of the common SCADA (Supervisory Control and Data Acquisition systems involve energy and water distribution systems. In this paper, the energy distribution SCADA system comprising several substations is considered. A secure framework is proposed that combines the energy control system with Wireless Sensor Networks (WSNs, Mobile Ad hoc Networks (MANETs, and the Internet, providing anomaly prevention and status management. SCADA attacks occur at the state estimators of the power systems which are used to route power flows and detect faulty devices. These estimators are located in the SCADA control center which is a sensitive area and measurements must be transmitted over a secure communication channel. The attack-resistance of the SCADA system is enhanced by increasing the hardness and complexity of the attack problem. The Attack-Resistant and Secure (ARS SCADA system is evaluated against existing techniques like NAMDIA (Network-Aware Mitigation of Data Integrity Attacks, Retrofit IDS (Intrusion Detection System, and CSBF (Critical State-Based Filtering for enhancing the attack-resistance and security of SCADA systems. It is found that the performance of ARS SCADA system is good compared to the existing methods in terms of maximum normalized attack impact and latency.

  5. Defense of Cyber Infrastructures Against Cyber-Physical Attacks Using Game-Theoretic Models.

    Science.gov (United States)

    Rao, Nageswara S V; Poole, Stephen W; Ma, Chris Y T; He, Fei; Zhuang, Jun; Yau, David K Y

    2016-04-01

    The operation of cyber infrastructures relies on both cyber and physical components, which are subject to incidental and intentional degradations of different kinds. Within the context of network and computing infrastructures, we study the strategic interactions between an attacker and a defender using game-theoretic models that take into account both cyber and physical components. The attacker and defender optimize their individual utilities, expressed as sums of cost and system terms. First, we consider a Boolean attack-defense model, wherein the cyber and physical subinfrastructures may be attacked and reinforced as individual units. Second, we consider a component attack-defense model wherein their components may be attacked and defended, and the infrastructure requires minimum numbers of both to function. We show that the Nash equilibrium under uniform costs in both cases is computable in polynomial time, and it provides high-level deterministic conditions for the infrastructure survival. When probabilities of successful attack and defense, and of incidental failures, are incorporated into the models, the results favor the attacker but otherwise remain qualitatively similar. This approach has been motivated and validated by our experiences with UltraScience Net infrastructure, which was built to support high-performance network experiments. The analytical results, however, are more general, and we apply them to simplified models of cloud and high-performance computing infrastructures.

  6. Review of syn-flooding attack detection mechanism

    CERN Document Server

    Manna, Mehdi Ebady

    2012-01-01

    Denial of Service (DoS) is a security threat which compromises the confidentiality of information stored in Local Area Networks (LANs) due to unauthorized access by spoofed IP addresses. SYN Flooding is a type of DoS which is harmful to network as the flooding of packets may delay other users from accessing the server and in severe cases, the server may need to be shut down, wasting valuable resources, especially in critical real-time services such as in e-commerce and the medical field. The objective of this paper is to review the state-of-the art of detection mechanisms for SYN flooding. The detection schemes for SYN Flooding attacks have been classified broadly into three categories - detection schemes based on the router data structure, detection schemes based on statistical analysis of the packet flow and detection schemes based on artificial intelligence. The advantages and disadvantages for various detection schemes under each category have been critically examined. The performance measures of the cate...

  7. Migraine Trainers as Models: the effectiveness of Lay trainerswith migraine for behavioural attack prevention

    NARCIS (Netherlands)

    S.Y.M. Mérelle (Saskia)

    2008-01-01

    textabstractMigraine is a chronic brain disorder, characterized by attacks of severe headache accompanied by nausea, vomiting and sensitivity to light, sound and smell. Attacks can be preceded by premonitory symptoms such as fatigue, muscular stiff ness or negative aff ect. It has been shown that co

  8. 76 FR 56631 - Continuation of the National Emergency With Respect to Certain Terrorist Attacks

    Science.gov (United States)

    2011-09-13

    .... (Presidential Sig.) THE WHITE HOUSE, September 9, 2011. [FR Doc. 2011-23609 Filed 9-12-11; 11:15 am] Billing... With Respect to Certain Terrorist Attacks #0; #0; #0; Presidential Documents #0; #0; #0;#0;Federal... Certain Terrorist Attacks Consistent with section 202(d) of the National Emergencies Act, 50 U.S.C....

  9. 78 FR 56579 - Continuation of the National Emergency With Respect to Certain Terrorist Attacks

    Science.gov (United States)

    2013-09-12

    ... the Congress. (Presidential Sig.) THE WHITE HOUSE, September 10, 2013. [FR Doc. 2013-22406 Filed 9-11... Emergency With Respect to Certain Terrorist Attacks #0; #0; #0; Presidential Documents #0; #0; #0;#0;Federal... to Certain Terrorist Attacks Consistent with section 202(d) of the National Emergencies Act, 50...

  10. Study of DSR and AODV under Sinkhole Attack and Its Proposed Prevention Technique

    Directory of Open Access Journals (Sweden)

    Winnie Main

    2014-03-01

    Full Text Available Mobile Ad-hoc Networks (MANET are wireless mobile nodes that communicate without any predefined infrastructure. This allows MANETs to be easily setup in geographical and terrestrial constraints. To achieve this kind of communication MANET routing protocols play an important role. Two routing protocols, DSR and AODV are studied in detail. This basic trait of a MANET makes its routing protocols very vulnerable to security attacks. One such attack is the ‘Sinkhole’ attack which lures packets towards the sinkhole node. A malicious Sinkhole node severely degrades the network once the attack is in progress. This paper describes two of the popular MANET routing protocols, DSR and AODV and the sinkhole attack on these protocols. Prior research carried out to prevent the sinkhole attack is analyzed. Multiple procedures are documented to prevent and mitigate the problem of Sinkhole in MANETs. The proposed solution relies on tackling the sequence number discontinuity to contain Sinkhole attacks. A prevention technique is proposed that relies on the fact that the sequence number discontinuity if tackled can go a long way in containing Sinkhole attacks.

  11. 基于灰色理论的攻击者攻击能力评估%Attack Ability Evaluation of Attackers Based on Grey Theory

    Institute of Scientific and Technical Information of China (English)

    赵博夫; 殷肖川; 吴传芝

    2011-01-01

    分析网络攻击对目标网络的破坏效果以及攻击者的攻击能力.基于灰色理论,提出一种评估攻击者攻击能力的方法,给出评估的指标体系,对评估准则进行计算.在实际网络中进行攻击实验,结果表明,该评估方法能有效对网络攻击过程中攻击者的攻击能力进行定量评估.%This paper analyzes the attack effect of target network and the ability of attackers, basing on Grey theory, it evaluates the ability of attackers in the process of network attacks.It gives the evaluation index system, and calculates the evaluation criterions.Experimental results in the actual network show that the method can quantitatively evaluates the ability of attacker in the process of network attacks.

  12. Study and Performance Evaluation on Recent DDoS Trends of Attack & Defense

    Directory of Open Access Journals (Sweden)

    Muhammad Aamir

    2013-07-01

    Full Text Available Different types and techniques of DDoS attacks & defense are studied in this paper with some recent information on attacks dominated in year 2012 (1st Quarter. We further provide simulation based analysis of an FTP server’s performance in a typical enterprise network under distributed denial of service attack. Simulations in OPNET show noticeable variations in connection capacity, task processing and delay parameters of the attacked server as compared to the performance without attack. DDoS detection and mitigation mechanisms discussed in this paper mainly focus on some recently investigated techniques. Finally, conclusions are drawn on the basis of survey based study as well as simulation results.

  13. PERFORMANCE ANALYSIS OF ADHOC ON DEMAND DISTANCE VECTOR PROTOCOL WITH BLACKHOLE ATTACK IN WSN

    Directory of Open Access Journals (Sweden)

    Adnan Ahmed

    2014-01-01

    Full Text Available The security is major challenging issue in wireless sensor network applications because they are operated in public and unrestrained areas which also makes difficult to protect against tampering or captured by an adversary force that can launch insider attacks to make a node compromised. One type of such attack is black hole attack. Existing AODV routing protocol does not have mechanism to defend against such attacks. In this study, we comprehensively investigates the performance of AODV protocol by simulating it on the various network parameters with various number of blackhole nodes. The metrics for evaluation has been considered as packet delivery ratio, end to end delay, normalized routing overhead and total number of packets drop. The simulation results show that blackhole attack severely degrades the performance of WSN.

  14. Investigation of drop dynamic contact angle on copper surface

    Directory of Open Access Journals (Sweden)

    Orlova Evgenija

    2015-01-01

    Full Text Available This paper presents experimental results of the studying the effect of surface roughness, microstructure and flow rate on the dynamic contact angle at spreading of distilled non deaerate water drop on a solid horizontal substrates. Copper substrates with different roughness have been investigated. For each substrate static contact angles depending on volume flow rate have been obtained using shadow system. Increasing the volume flow rate resulted in an increase of the static contact angle. It was found that with increasing surface roughness dynamic contact angle arises. Also difference in formation of the equilibrium contact angle at low and high rates of drop growth has been detected.

  15. Investigation of drop dynamic contact angle on copper surface

    Science.gov (United States)

    Orlova, Evgenija; Feoktistov, Dmitriy; Kuznetsov, Geniy

    2015-01-01

    This paper presents experimental results of the studying the effect of surface roughness, microstructure and flow rate on the dynamic contact angle at spreading of distilled non deaerate water drop on a solid horizontal substrates. Copper substrates with different roughness have been investigated. For each substrate static contact angles depending on volume flow rate have been obtained using shadow system. Increasing the volume flow rate resulted in an increase of the static contact angle. It was found that with increasing surface roughness dynamic contact angle arises. Also difference in formation of the equilibrium contact angle at low and high rates of drop growth has been detected.

  16. Abnormal brain processing of cutaneous pain in migraine patients during the attack.

    Science.gov (United States)

    de Tommaso, Marina; Guido, Marco; Libro, Giuseppe; Losito, Luciana; Sciruicchio, Vittorio; Monetti, Carlo; Puca, Francomichele

    2002-11-15

    We examined cutaneous pain thresholds using CO(2) laser stimuli during migraine attacks, and defined the evoked cortical potential characteristics. Ten patients without aura were studied during attacks and for at least 72 h subsequently. Pain stimuli were generated on the dorsum of both hands and the right and left supraorbital zones, using pulses from a CO(2) laser. Absolute latencies of scalp potentials were measured at the highest peak of each response component, and the peak-to-peak amplitudes of N2a-P2 components were recorded. Cutaneous pain thresholds were significantly reduced on both the symptomatic and non-symptomatic sides during the attack, in comparison with the headache-free phase. The N2a-P2 complexes also increased in amplitude during attacks in comparison with the pain-free side. Thus, cutaneous hyperalgesia occurs during migraine attack, and is subtended by central sensitization phenomena, probably involving the cortex.

  17. Effect of Helicobacter Pylori Treatment on the Number and Intensity of Migraine Attacks

    Directory of Open Access Journals (Sweden)

    Alireza Bakhshipour

    2012-06-01

    Full Text Available Background: Migraine is a common headache with an unknown cause. Migraine is about three times more common in women (18.2% than in men (6.2%. The recent studies have posed the possible relationship between the Helicobacter pylori infection and migraine headache. This study tries to analyze the effect of treating H. pylori infection on number and severity of migraine attacks.Materials and Methods: In this clinical pilot study, a number of 60 patients with migraine were examined in terms of infecting with H. pylori. Patients with the infections were treated by H. pylori eradication treatment standard triple regimen and the frequency and severity of their migraine attacks were measured for three months and finally the average of frequency and severity of attacks before and after treatment were compared. Results: The average frequency of the migraine attacks in patients with the H.pylori infection who have been treated was 7.1 before treatment and 2.7 after treatment (p=0.001. Likewise, the severity rate of such attacks in such patients was 9 which decreased to 4.5 after treatment (p=0.002. Conclusion: According to our study, patients with migraine attacks are preferred to be examined tested in terms of infecting with H. pylori. Thus, and eradication of this infection can be effective in decreasing of the migraine attacks.

  18. Real-Time Detection of Application-Layer DDoS Attack Using Time Series Analysis

    Directory of Open Access Journals (Sweden)

    Tongguang Ni

    2013-01-01

    Full Text Available Distributed denial of service (DDoS attacks are one of the major threats to the current Internet, and application-layer DDoS attacks utilizing legitimate HTTP requests to overwhelm victim resources are more undetectable. Consequently, neither intrusion detection systems (IDS nor victim server can detect malicious packets. In this paper, a novel approach to detect application-layer DDoS attack is proposed based on entropy of HTTP GET requests per source IP address (HRPI. By approximating the adaptive autoregressive (AAR model, the HRPI time series is transformed into a multidimensional vector series. Then, a trained support vector machine (SVM classifier is applied to identify the attacks. The experiments with several databases are performed and results show that this approach can detect application-layer DDoS attacks effectively.

  19. An Entropy Architecture for Defending Distributed Denial-of-service Attacks

    Directory of Open Access Journals (Sweden)

    S. K. Srivatsa

    2009-10-01

    Full Text Available The goal of intrusion detection is to identify entities attempting to destabilize the security controls. Network based intrusion detection techniques are used to identify unauthorized, illicit and anomalous behavior based on the network traffic. Identifying the network intruders is the most significant problem for network administrators and network security experts. Intrusion detection systems are an important component of defensive measures protecting computer systems and networks from abuse. New threats are emerging at an increasing rate. Distributed Denial-of-Service (DDoS attacks have emerged as a popular means of causing mass damage. The impacts of DoS attack will cause greater collateral damage. DoS attacks remain a serious threat to the users, organizations, and infrastructures of the Internet. The approaches used in the existing defense techniques are based on traffic characteristics such as traffic deviation, attack pattern matching etc, which may not yield accurate detection and involves high complexity. In this paper, the router based entropy algorithm has been designed to improve the performance and protection from the distributed denial-of-service attacks. This work includes attack tree construction, attacks detection and clustering of alerts. By calculating the predicted entropy for a router, alerts are raised for flows in which the predicted entropy is more than a threshold value. Then the alerts are grouped into different clusters according to their source, target, time and attack-type. It helps to avoid group redundant alerts and to associate alerts that are of the same nature. By Simulation results, it has been shown that the proposed architecture improves the detection accuracy and throughput while reducing the alert overhead. In this paper, we have explored the current research potential in terms of security, throughput performance of the router and impact of DoS attack technology based on intruder activity and attack tools.

  20. Measurement of dihedral angles by scanning electron microscopy.

    Science.gov (United States)

    Achutaramayya, G.; Scott, W. D.

    1973-01-01

    The extension of Hoover's (1971) technique to the case of dihedral-angle measurement is described. Dihedral angles are often determined by interferometry on thermally grooved grain boundaries to obtain information on relative interfacial energies. In the technique considered the measured angles approach the true angles as the tilt angle approaches 90 deg. It is pointed out that the scanning electron microscopy method provides a means of seeing the real root of a groove at a lateral magnification which is higher than that obtainable with interferometry.

  1. Development of a Contact Angle Measurement Method Based Upon Geometry

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dong Su; Pyo, Na Young; Seo, Seung Hee [Ewha Womans University, Seoul (Korea); Choi, Woo Jin [Suwon University, Suwon (Korea); Kwon, Young Shik [Suwon Science College, Suwon (Korea)

    1998-12-31

    A new way of contact angle measurement is derived based on simple geometrical calculation. Without using complicated contact angle measurement instrument, just measuring the diameter and height of liquid lens made it possible to calculate the contact angle value with a reasonable reliability. To validate the contact angle value obtained by this method, contact angle of the same liquid lens is measured using conventional goniometer and it is verified that two values are nearly same within the limit of observational error. (author). 6 refs., 2 tabs., 3 figs.

  2. RESILIENT SCHEME AGAINST REDUCTION OF QUALITY (ROQ DISTRIBUTED DENIAL OF SERVICE ATTACK IN MANET

    Directory of Open Access Journals (Sweden)

    S.A. Arunmozhi

    2011-09-01

    Full Text Available Defending against denial-of-service attacks (DoS in a mobile ad hoc network (MANET is challenging because of the dynamic network topology. Security primitives must be dynamically adjusted to cope with the network. The Reduction-of-Quality (RoQ Distributed Denial of Service (DDoS attack is one which throttles the tcp throughput heavily and reduces the quality-of-service (QoS to end systems gradually rather than refusing the clients from the services completely. Supporting QoS in MANET is a challenging task, particularly in the presence of malicious users. In this paper, we propose a DoS resilient technique that uses a flow table to detect the attackers. The proposed defense mechanism identifies the attackers based on the congestion bit notification and asks the sending node to reduce the sending rate. Once the attackers are identified, all the packets from those nodes will be blocked. The throughput and delay performance of TCP or UDP flows are very sensitive to such RoQ attacks. Through extensive ns2 network simulations, we demonstrate the achievement of high throughput and low delay for a network under the RoQ attack.

  3. Impacts of tropical cyclone inflow angle on ocean surface waves

    Institute of Scientific and Technical Information of China (English)

    ZHAO Wei; HONG Xin

    2011-01-01

    The inflow angle of tropical cyclones (TC) is generally neglected in numerical studies of ocean surface waves induced by TC. In this study, the impacts of TC inflow angle on ocean surface waves were investigated using a high-resolution wave model. Six numerical experiments were conducted to examine, in detail, the effects of inflow angle on mean wave parameters and the spectrum of wave directions. A comparison of the waves simulated in these experiments shows that inflow angle significantly modifies TC-induced ocean surface waves. As the inflow angle increases, the asymmetric axis of the significant wave height (SWH) field shifts 30° clockwise, and the maximum SWH moves from the front-right to the rear-right quadrant. Inflow angle also affects other mean wave parameters, especially in the rear-left quadrant, such as the mean wave direction, the mean wavelength, and the peak direction. Inflow angle is a key factor in wave models for the reproduction of double-peak or multi-peak patterns in the spectrum of wave directions. Sensitivity experiments also show that the simulation with a 40° inflow angle is the closest to that of the NOAA statistical SLOSH inflow angle. This suggests that 40° can be used as the inflow angle in future TC-induced ocean surface wave simulations when SLOSH or observed inflow angles are not available.

  4. Volume and efficiency of attacking actions in repertoire of qualified foil fencers at the modern stage of development of fencing.

    Directory of Open Access Journals (Sweden)

    Voronegskiy E.V.

    2011-06-01

    Full Text Available Studied indices of volume and effectiveness of attacking actions in competitive duels of qualified foil fencers in the competition activity. The study analyzed 35 video recording duels of foreign and domestic highly skilled foil fencers. Established that the compound attacks occupy a leading place (65,3% among other types of attacks in competitive activity of qualified foil fencers. Volume of simple attacks is equal 34,7 % with a productivity of 31,9 % from the total number the of attacks of qualified foil fencers have been determined.

  5. Clinical analysis on neuroprotection of transient ischemic attacks

    Institute of Scientific and Technical Information of China (English)

    Dimitar Maslarov; Desislava Drenska

    2011-01-01

    Transient ischemic attack (TIA) is an acute cerebrovascular incident, and is generally considered the best opportunity for early neuroprotective treatment against cerebral ischemia. This study retrospectively analyzed 80 patients with TIA (38 males and 42 females). Among 61 patients who received neuroprotective cerebrolysin treatment within 24 hours after TIA onset, 13 (21.31%)patients suffered subsequent strokes. Among 19 patients who received neuroprotective

  6. A Review of Network Forensics Techniques for the Analysis of Web Based Attack

    Directory of Open Access Journals (Sweden)

    Mr. Sudhakar Parate, Ms. S. M. Nirkhi

    2012-12-01

    Full Text Available Network forensics has been the most prevalenttechnology to investigate different attack. It used fortroubleshooting connection issues and helping tosolve various network security problems, such assystem log, router log, and access control. NetworkForensic help to identify the evidences of datasource as intermediate side and the end sides. Thispaper gives comprehensive review on varioustechniques that helps to improve the system,analysis of different attack, detection of attack. Itfocuses on the critical stages of preservation andacquisition of digital evidence from the differentsource to be used as evidence for aidinginvestigation.

  7. Superwide-angle acoustic propagations above the critical angles of the Snell law in liquid—solid superlattice

    Science.gov (United States)

    Zhang, Sai; Zhang, Yu; Gao, Xiao-Wei

    2014-12-01

    In this paper, superwide-angle acoustic propagations above the critical angles of the Snell law in liquid—solid superlattice are investigated. Incident waves above the critical angles of the Snell law usually inevitably induce total reflection. However, incident waves with big oblique angles through the liquid—solid superlattice will produce a superwide angle transmission in a certain frequency range so that total reflection does not occur. Together with the simulation by finite element analysis, theoretical analysis by using transfer matrix method suggests the Bragg scattering of the Lamb waves as the physical mechanism of acoustic wave super-propagation far beyond the critical angle. Incident angle, filling fraction, and material thickness have significant influences on propagation. Superwide-angle propagation phenomenon may have potential applications in nondestructive evaluation of layered structures and controlling of energy flux.

  8. Note: A gel based imaging technique of the iridocorneal angle for evaluation of angle-closure glaucoma

    Science.gov (United States)

    Shinoj, V. K.; Murukeshan, V. M.; Baskaran, M.; Aung, T.

    2014-06-01

    Noninvasive medical imaging techniques have high potential in the field of ocular imaging research. Angle closure glaucoma is a major disease causing blindness and a possible way of detection is the examination of the anterior chamber angle in eyes. Here, a simple optical method for the evaluation of angle-closure glaucoma is proposed and illustrated. The light propagation from the region associated with the iridocorneal angle to the exterior of eye is considered analytically. The design of the gel assisted probe prototype is carried out and the imaging of iridocorneal angle is performed on an eye model.

  9. Seven Deadliest Network Attacks

    CERN Document Server

    Prowell, Stacy; Borkin, Mike

    2010-01-01

    Do you need to keep up with the latest hacks, attacks, and exploits effecting networks? Then you need Seven Deadliest Network Attacks. This book pinpoints the most dangerous hacks and exploits specific to networks, laying out the anatomy of these attacks including how to make your system more secure. You will discover the best ways to defend against these vicious hacks with step-by-step instruction and learn techniques to make your computer and network impenetrable. Attacks detailed in this book include: Denial of Service War Dialing Penetration "Testing" Protocol Tunneling Spanning Tree At

  10. Magic angle spinning NMR of paramagnetic proteins.

    Science.gov (United States)

    Knight, Michael J; Felli, Isabella C; Pierattelli, Roberta; Emsley, Lyndon; Pintacuda, Guido

    2013-09-17

    Metal ions are ubiquitous in biochemical and cellular processes. Since many metal ions are paramagnetic due to the presence of unpaired electrons, paramagnetic molecules are an important class of targets for research in structural biology and related fields. Today, NMR spectroscopy plays a central role in the investigation of the structure and chemical properties of paramagnetic metalloproteins, linking the observed paramagnetic phenomena directly to electronic and molecular structure. A major step forward in the study of proteins by solid-state NMR came with the advent of ultrafast magic angle spinning (MAS) and the ability to use (1)H detection. Combined, these techniques have allowed investigators to observe nuclei that previously were invisible in highly paramagnetic metalloproteins. In addition, these techniques have enabled quantitative site-specific measurement of a variety of long-range paramagnetic effects. Instead of limiting solid-state NMR studies of biological systems, paramagnetism provides an information-rich phenomenon that can be exploited in these studies. This Account emphasizes state-of-the-art methods and applications of solid-state NMR in paramagnetic systems in biological chemistry. In particular, we discuss the use of ultrafast MAS and (1)H-detection in perdeuterated paramagnetic metalloproteins. Current methodology allows us to determine the structure and dynamics of metalloenzymes, and, as an example, we describe solid-state NMR studies of microcrystalline superoxide dismutase, a 32 kDa dimer. Data were acquired with remarkably short times, and these experiments required only a few milligrams of sample.

  11. Seven Deadliest Microsoft Attacks

    CERN Document Server

    Kraus, Rob; Borkin, Mike; Alpern, Naomi

    2010-01-01

    Do you need to keep up with the latest hacks, attacks, and exploits effecting Microsoft products? Then you need Seven Deadliest Microsoft Attacks. This book pinpoints the most dangerous hacks and exploits specific to Microsoft applications, laying out the anatomy of these attacks including how to make your system more secure. You will discover the best ways to defend against these vicious hacks with step-by-step instruction and learn techniques to make your computer and network impenetrable. Windows Operating System-Password AttacksActive Directory-Escalat

  12. Seven deadliest USB attacks

    CERN Document Server

    Anderson, Brian

    2010-01-01

    Do you need to keep up with the latest hacks, attacks, and exploits effecting USB technology? Then you need Seven Deadliest USB Attacks. This book pinpoints the most dangerous hacks and exploits specific to USB, laying out the anatomy of these attacks including how to make your system more secure. You will discover the best ways to defend against these vicious hacks with step-by-step instruction and learn techniques to make your computer and network impenetrable. Attacks detailed in this book include: USB Hacksaw USB Switchblade USB Based Virus/Malicous Code Launch USB Device Overflow RAMdum

  13. Study of the course of the incidence angle during growth.

    Science.gov (United States)

    Mangione, P; Gomez, D; Senegas, J

    1997-01-01

    Standing posture is made possible by hip extension and lumbar lordosis. Lumbar lordosis is correlated with pelvic parameters, such as the declivity angle of the upper surface of the sacrum and the incidence angle, which determine the sagittal morphotype. Incidence angle, which is different for each individual, is known to be very important for up-right posture, but its course during life has not yet been established. Incidence angle was measured on radiographs of 30 fetuses, 30 children and 30 adults, and results were analysed using the correlation coefficient r and Student's t test. A statistically significant correlation between age and incidence angle was observed. Incidence angle considerably increases during the first months, continues to increase during early years, and stabilizes around the age of 10 years. Incidence is a mark of bipedism, and its role in sagittal balance is essential.

  14. The correlation of multi-angle thermal infrared data and the choice of optimal view angles

    Institute of Scientific and Technical Information of China (English)

    FAN; Wenjie; XU; Xiru

    2004-01-01

    Based on the matrix formula of thermal infrared radiant system, the components temperature can be retrieved by the inversive matrix. Around the stability problem of retrieved result, the research work we did was focused on (i) the correlation of (wk,j) which is the key to affect the retrieval accuracy, (ii) a general method which can help us find the number of retrievable parameters and evaluate the retrieval error before its performance, (iii) the choice of "optimal viewing angle group" based on the formula of absolute error propagation. The row winter wheat field was chosen as an example. The results can provide a theoretical basis for multi-angle thermal infrared remote sensing and components temperature retrieval.

  15. Magnetic resonance imaging of cerebellopontine angle lesions

    Directory of Open Access Journals (Sweden)

    Pratiksha Yadav

    2015-01-01

    Full Text Available Background: Cerebellopontine angle (CPA tumors are usually benign, and they are divided into extra-axial, intra-axial, extradural, and petrous axis tumors. CPA pathologies can be asymptomatic or it may present with vertigo, tinnitus, or unilateral hearing loss depending upon the site of tumor origin and displacement of the neurovascular structure. Aim and Objectives: To evaluate the role of magnetic resonance imaging (MRI aided with contrast-enhanced MRI as an imaging modality for diagnosis of CPA lesions. Materials and Methods: Analysis of 36 patients of CPA lesions over a period of 2 years was done. MRI was performed on Siemens 1.5 Tesla MAGNETOM Avanto Machine. Conclusion: There are spectrums of pathologies, which can present with these symptoms, which includes tumors, vascular malformations, and vascular loop compressing vestibulocochlear nerve or mastoid pathology so it is important to investigate the patient by MRI. Contrast-enhanced MRI is the most sensitive investigation in the evaluation of the CPA lesions, its characteristic, and its extent.

  16. Increase of productivity attacks of young basketbal players on the basis perfection their competitive activity.

    Directory of Open Access Journals (Sweden)

    Kozin V.V.

    2011-02-01

    Full Text Available Research objective is increase of productivity attacks of basketball players 15-17 years on the basis perfection their competitive activity creation of situations of counteractions is carried out by connection of models in the directed programming system of game activity. The system has different character and allows to model individual and group counteractions. The gain of indicators of mental qualities is as a result established, increase of indicators of force and speed qualities, productivity of attacking actions is noted.

  17. Prevention of Co-operative Black Hole attack in Manet on DSR protocol using Cryptographic Algorithm

    Directory of Open Access Journals (Sweden)

    G.Vennila

    2014-10-01

    Full Text Available The Mobile ad-hoc network (MANET is a collection of wireless mobile node in which each node can communicate with other node without use of predefined infrastructure. Currently, a lot of efficient protocols have been proposed for MANET. All of these efficient Routing protocols are depends only conviction and supportive environment. Conversely, the networks are more vulnerable to various kinds of routing attacks with the presence of malicious nodes. Black hole attack is one of network layer attack. In this attack, A malicious node make use of routing protocol to advertise itself that has a shortest path to reach destination, drops at the cost of original routing packets. In our work, the proposed algorithm is used to secure the DSR protocol. This will help to improve the performance of Mobile Ad hoc network due to the attack. There are several prevention mechanisms to eliminate the Black Hole attack in MANET. The aim of the paper is to provide better prevention of Co-operative Black hole attack in MANET and how it affects the performance metrics in terms of throughput and delay of the network by comparing the network performance with and without black hole nodes.

  18. Before Using Aspirin to Lower Your Risk of Heart Attack or Stroke, Here Is What You Should Know

    Science.gov (United States)

    ... Medicines Safe Daily Use of Aspirin Before Using Aspirin to Lower Your Risk of Heart Attack or ... care provider can determine whether regular use of aspirin will help to prevent a heart attack or ...

  19. [Risk perception and psychological reactions in public crisis situations using the example of terror attacks].

    Science.gov (United States)

    Grimm, A; Hulse, L; Schmidt, S

    2009-12-01

    The reactions to the 9/11 terror attacks were immense in the western population. In the current review, the impact of terror attacks is presented with surveys, clinical interviews, and scientific polls, which were identified in a comprehensive literature search. Results show that the fear of further terror attacks is comparatively overestimated in the population and is associated with numerous psychological consequences and reactions. The overestimation of the probability of further terror attacks is related among other reasons to its unique features and its strong representation in the media. Several independent studies proved that the number of stress symptoms and psychiatric diagnoses is associated with a high risk perception in relation to terror attacks. This was not only the case for victims of terror attacks, but also for people indirectly exposed to the terror attacks. In addition, there is evidence that the number of the stress symptoms correlate with the duration of TV consumption of new findings about terror attempts. Methodologically, there is a critical lack of more in-depth analyses to explain the development of risk perceptions and its influence on mental and physical health. Because of the international importance and cross-cultural differences, an international standardization of research is desirable.

  20. Denial of Service (DoS Attacks at Network Layer in WSN

    Directory of Open Access Journals (Sweden)

    Sunil Ghildiyal,

    2015-11-01

    Full Text Available Recent advancements in technology, tiny size, cost effectiveness have made sensors as a crucial part of real world sensitive applications. These sensor nodes are scattered over an area to monitor the situations like fire, flood and record the data and to forward meaningful data to the center head node for observation, resulting an advance prompt to control the situation. In last decade, WSN have grown significantly in variety of areas and applications, resulted the high, consistent security mechanism. Also, there is variety of attacks on WSN at their different layers of architecture. Though sensor nodes are not capable enough in terms of power, processing etc. but applications based on these sensors demand on-time collection of information or data and then to send same on reliable, secure delivery medium. Small sensors with limited hardware, processing cannot afford traditional security mechanisms to face or sustain the attacks. There is variety of attacks at different layers of WSN architecture to affect sensor‟s roles like signaling, framing, transmission etc. Many Denial of Service (DoS attacks are identified at each layer of WSN which are purposeful, planned attacks to hamper the availability of service, restricting the sensor node‟s utility for problem solution. In this paper we will focus on the WSN architecture, characteristics, constraints and various types of DoS attacks primarily on physical and data link layer and particularly at network layer in details with some suggestions against attacks.

  1. An Efficient Algorithm for the Detection of Exposed and Hidden Wormhole Attack

    Directory of Open Access Journals (Sweden)

    ZUBAIR AHMED KHAN

    2016-07-01

    Full Text Available MANETs (Mobile Ad Hoc Networks are slowly integrating into our everyday lives, their most prominent uses are visible in the disaster and war struck areas where physical infrastructure is almost impossible or very hard to build. MANETs like other networks are facing the threat of malicious users and their activities. A number of attacks have been identified but the most severe of them is the wormhole attack which has the ability to succeed even in case of encrypted traffic and secure networks. Once wormhole is launched successfully, the severity increases by the fact that attackers can launch other attacks too. This paper presents a comprehensive algorithm for the detection of exposed as well as hidden wormhole attack while keeping the detection rate to maximum and at the same reducing false alarms. The algorithm does not require any extra hardware, time synchronization or any special type of nodes. The architecture consists of the combination of Routing Table, RTT (Round Trip Time and RSSI (Received Signal Strength Indicator for comprehensive detection of wormhole attack. The proposed technique is robust, light weight, has low resource requirements and provides real-time detection against the wormhole attack. Simulation results show that the algorithm is able to provide a higher detection rate, packet delivery ratio, negligible false alarms and is also better in terms of Ease of Implementation, Detection Accuracy/ Speed and processing overhead.

  2. ATTACK DETECTION AND CLASSIFICATION OF HETEROGENEOUS WIRELESS SENSORS USING CO-CLUSTERING

    Directory of Open Access Journals (Sweden)

    K.V.RAMANA

    2012-02-01

    Full Text Available In a Wireless Sensor Network a large number of sensors are deployed for the purpose of sensing data and then to bring the data back securely to nearby base stations. The base stations then perform thecostly computation on behalf of the sensors to analyze the data sensed by the sensors. Due to resource limitations of the nodes and also due to the vulnerability of physical captures of the nodes, the traditional cryptographic techniques are very complex and should not fit for energy constrained environments. Data mining techniques can be applied to find the malicious behavior of the nodes of the SensorNetwork. By analyzing the traffic patterns one can differentiate the normal behavior from malicious behaviour.Those techniques are used to identify various attacks. This paper addresses the issue of Attacks using data mining techniques. There exist two types of attacks: (i external and (ii internal. External attacks are those in which an attacker manipulates the communication between pairs of trusted nodes and causes the nodes to de-synchronize. Internal attacks are those in which internal attackers report false clock references to their neighboring nodes proposed an approach to develop a protocol. The protocol not only finds malicious node(s but also counts them withinthe group using data mining clustering techniques.

  3. [A boy with nystagmus, refractory dystonia and apneic attack due to alternating hemiplegia of childhood].

    Science.gov (United States)

    Shiota, Naoki; Shimono, Masayuki; Tomioka, Shiho; Takano, Kenichi; Kato, Ayako; Kawakami, Akihiro; Ishizuka, Takehiro

    2007-07-01

    We herein report the findings of a 2-year-6-month-old boy, who had been experiencing monocular pendular nystagmus, strabismus, and episodic eye deviation nystagmus, intractable dystonia and apneic attack which all began when he was 2 days of age. He underwent a complete blood count test, blood chemistry test, analysis of amino acids in the blood and urine, analysis of pyruvate/lactate in blood and cerebrospinal fluid, head computed tomography and magnetic resonance imaging and no abnormal results were identified. His attacks were resistant to multiple antiepileptic and dopaminergic drugs. He showed transient left and/or right hemiplegia after nystagmus, dystonia and/or apneic attacks at 8-months of age with retardation in intelligence. We diagnosed him to have alternating hemiplegia of childhood (AHC). We were unsure how to deal with his attacks after he was discharged from the hospital, however, resuscitation with the ambu bag by his mother at home and the intravenous infusion of diazepam or thiamylal at the hospital together was proven to be an effective method for treating his severe apneic attacks. The effect of diazepam and amantadine on these attacks was transient, however, the administration of flunarizine with amantadine resulted in an improvement in his attacks. We therefore consider the administration of flunarizine to be essential for the effective treatment of AHC in this case.

  4. Apparent contact angle of an evaporating drop

    Science.gov (United States)

    Morris, S. J. S.

    2012-11-01

    In experiments by Poulard et al. (2005), a sessile drop of perfectly wetting liquid evaporates from a non-heated substrate into an under-saturated mixture of vapour with an inert gas; evaporation is limited by vapour diffusion. The system exhibits an apparent contact angle θ that is a flow property. Under certain conditions, the apparent contact line was stationary relative to the substrate; we predict θ for this case. Observed values of θ are small, allowing lubrication analysis of the liquid film. The liquid and vapour flows are coupled through conditions holding at the phase interface; in particular, vapour partial pressure there is related to the local value of liquid pressure through the Kelvin condition. Because the droplet is shallow, the interfacial conditions can be transferred to the solid-liquid interface at y = 0 . We show that the dimensionless partial pressure p (x , y) and the film thickness h (x) are determined by solving ∇2 p = 0 for y > 0 subject to a matching condition at infinity, and the conditions - p = L hxx +h-3 and (h3px) x + 3py = 0 at y = 0 . The parameter L controls the ratio of Laplace to disjoining pressure. We analyse this b.v.p. for the experimentally-relevant case L --> 0 .

  5. Modelling the attack success of planktonic predators: patterns and mechanisms of prey size selectivity

    DEFF Research Database (Denmark)

    Caparroy, P.; Thygesen, Uffe Høgsbro; Visser, Andre

    2000-01-01

    A mathematical model of the attack success of planktonic predators (fish larvae and carnivorous copepods) is proposed. Based on a geometric representation of attack events, the model considers how the escape reaction characteristics (speed and direction) of copepod prey affect their probability...... of being captured. By combining the attack success model with previously published hydrodynamic models of predator and prey perception, we examine how predator foraging behaviour and prey perceptive ability affect the size spectra of encountered and captured copepod prey. We examine food size spectra of (i...... also acts in modifying the prey escape direction. The model demonstrates that the reorientation of the prey escape path towards the centre of the feeding current's flow field results in increased attack success of the predator. Finally, the model examines how variability in the kinetics of approach...

  6. Dyspnea during panic attacks. An Internet survey of incidences of changes in breathing.

    Science.gov (United States)

    Anderson, B; Ley, R

    2001-09-01

    This article presents the results of a survey that investigated breathing-related symptoms of panic attacks together with the frequency of other symptoms reported by active panickers. All the participants of this study experienced naturally occurring panic attacks and sought treatment guidance by visiting a Web site devoted to the treatment of panic. The results of a symptom questionnaire showed that 195 respondents (95.1%) reported breathing changes during panic attacks, and remarkable dyspnea was reported by more than two thirds (68%) of respondents. These findings are consistent with earlier studies but are contrary to conclusions that only a small number of panickers report shortness of breath as a symptom. This study concludes that outside of the laboratory, a large majority of people who suffer from panic attacks experience symptoms of dyspnea.

  7. Rhynchophorus ferrugineus attack affects a group of compounds rather than rearranging Phoenix canariensis metabolic pathways.

    Science.gov (United States)

    Giovino, Antonio; Martinelli, Federico; Saia, Sergio

    2016-04-01

    The red palm weevil (RPW; Rhynchophorus ferrugineus) is spreading worldwide and severely harming many palm species. However, most studies on RPW focused on insect biology, and little information is available about the plant response to the attack. In the present experiment, we used metabolomics to study the alteration of the leaf metabolome of Phoenix canariensis at initial (1st stage) or advanced (2nd stage) attack by RPW compared with healthy (unattacked) plants. The leaf metabolome significantly varied among treatments. At the 1st stage of attack, plants showed a reprogramming of carbohydrate and organic acid metabolism; in contrast, peptides and lipid metabolic pathways underwent more changes during the 2nd than 1st stage of attack. Enrichment metabolomics analysis indicated that RPW attack mostly affected a particular group of compounds rather than rearranging plant metabolic pathways. Some compounds selectively affected during the 1st rather than 2nd stage (e.g. phenylalanine; tryptophan; cellobiose; xylose; quinate; xylonite; idonate; and iso-threonate; cellobiotol and arbutine) are upstream events in the phenylpropanoid, terpenoid and alkaloid biosynthesis. These compounds could be designated as potential markers of initial RPW attack. However, further investigation is needed to determine efficient early screening methods of RPW attack based on the concentrations of these molecules.

  8. Rhynchophorus ferrugineus attack affects a group of compounds rather than rearranging Phoenix canariensis metabolic pathways

    Institute of Scientific and Technical Information of China (English)

    Antonio Giovino; Federico Martinelli; Sergio Saia

    2016-01-01

    The red palm weevil (RPW; Rhynchophorus ferrugi-neus) is spreading worldwide and severely harming many palm species. However, most studies on RPW focused on insect biology, and little information is available about the plant response to the attack. In the present experiment, we used metabolomics to study the alteration of the leaf metabolome of Phoenix canariensis at initial (1st stage) or advanced (2nd stage) attack by RPW compared with healthy (unattacked) plants. The leaf metabolome significantly varied among treatments. At the 1st stage of attack, plants showed a reprogramming of carbohydrate and organic acid metabolism;in contrast, peptides and lipid metabolic pathways underwent more changes during the 2nd than 1st stage of attack. Enrichment metabolomics analysis indicated that RPW attack mostly affected a particular group of compounds rather than rearranging plant metabolic pathways. Some compounds selectively affected during the 1st rather than 2nd stage (e.g. phenylalanine;tryptophan;cel obiose;xylose;quinate;xylonite;idonate;and iso-threonate;cel obiotol and arbutine) are upstream events in the phenylpropanoid, terpenoid and alkaloid biosynthesis. These compounds could be designated as potential markers of initial RPW attack. However, further investigation is needed to determine efficient early screening methods of RPW attack based on the concentrations of these molecules.

  9. Denial of Service Attack: Analysis of Network Traffic Anormaly using Queuing Theory

    CERN Document Server

    Singh, Neetu; Chaudhuri, Pranay

    2010-01-01

    Denial-of-service (DOS) attacks increasingly gained reputation over the past few years. As the Internet becomes more ubiquitous, the threat of the denial-of-service attacks becomes more realistic and important for individuals, businesses, governmental organizations, and even countries. There is intensive need to detect an attack in progress as soon as possible. The efficiency of diagnosing the DOS attack using concepts of queuing theory and performance parameter of the system has been investigated in the present work, as the servers definitely have some mechanisms to store and process the requests. Utilizing this concept of queuing theory, the collection of data patterns were generated. With the performance parameter of the system, the analysis of the data pattern had been made to diagnose the network anomaly. Performance analysis and results show the accuracy of the proposed scheme in detecting anomalies.

  10. Mapping of low flip angles in magnetic resonance

    Energy Technology Data Exchange (ETDEWEB)

    Balezeau, Fabien; Saint-Jalmes, Herve [LTSI, INSERM U642, Universite Rennes 1 (France); Eliat, Pierre-Antoine [PRISM, IFR 140, Universite Rennes 1 (France); Cayamo, Alejandro Bordelois, E-mail: fabien.balezeau@gmail.com [Centro De BiofIsika Medica, Universidad de Oriente, Santiago de Cuba (Cuba)

    2011-10-21

    Errors in the flip angle have to be corrected in many magnetic resonance imaging applications, especially for T1 quantification. However, the existing methods of B1 mapping fail to measure lower values of the flip angle despite the fact that these are extensively used in dynamic acquisition and 3D imaging. In this study, the nonlinearity of the radiofrequency (RF) transmit chain, especially for very low flip angles, is investigated and a simple method is proposed to accurately determine both the gain of the RF transmitter and the B1 field map for low flip angles. The method makes use of the spoiled gradient echo sequence with long repetition time (TR), such as applied in the double-angle method. It uses an image acquired with a flip angle of 90{sup 0} as a reference image that is robust to B1 inhomogeneity. The ratio of the image at flip angle alpha to the image at a flip angle of 90{sup 0} enables us to calculate the actual value of alpha. This study was carried out at 1.5 and 4.7 T, showing that the linearity of the RF supply system is highly dependent on the hardware. The method proposed here allows us to measure the flip angle from 1{sup 0} to 60{sup 0} with a maximal uncertainty of 10% and to correct T1 maps based on the variable flip angle method.

  11. A Survey On Various Defense Mechanisms Against Application Layer Distributed Denial Of Service Attack

    Directory of Open Access Journals (Sweden)

    Ms. Anuja R. Zade

    2011-11-01

    Full Text Available The severity of application layer Distributed Denial of Service attack has become a major threat to network operators nowadays. Application layer Distributed Denial of Service attack causes unavailability of resources, revenue loss, and customer churns etc and is one of the most difficult problems to defend against in the internet. The goal of paper is to understand various techniquesproposed recently to defend against specifically application layer Distributed Denial of Service attack. The next step in the path would be to come up with a better solution to solve this problem. Undoubtedly the following discussed techniques are extremely good. A collaborative approach using few of them can be a better solution.

  12. The Framework for Simulation of Bioinspired Security Mechanisms against Network Infrastructure Attacks

    Directory of Open Access Journals (Sweden)

    Andrey Shorov

    2014-01-01

    Full Text Available The paper outlines a bioinspired approach named “network nervous system" and methods of simulation of infrastructure attacks and protection mechanisms based on this approach. The protection mechanisms based on this approach consist of distributed prosedures of information collection and processing, which coordinate the activities of the main devices of a computer network, identify attacks, and determine nessesary countermeasures. Attacks and protection mechanisms are specified as structural models using a set-theoretic approach. An environment for simulation of protection mechanisms based on the biological metaphor is considered; the experiments demonstrating the effectiveness of the protection mechanisms are described.

  13. The framework for simulation of bioinspired security mechanisms against network infrastructure attacks.

    Science.gov (United States)

    Shorov, Andrey; Kotenko, Igor

    2014-01-01

    The paper outlines a bioinspired approach named "network nervous system" and methods of simulation of infrastructure attacks and protection mechanisms based on this approach. The protection mechanisms based on this approach consist of distributed procedures of information collection and processing, which coordinate the activities of the main devices of a computer network, identify attacks, and determine necessary countermeasures. Attacks and protection mechanisms are specified as structural models using a set-theoretic approach. An environment for simulation of protection mechanisms based on the biological metaphor is considered; the experiments demonstrating the effectiveness of the protection mechanisms are described.

  14. Heavy-tailed distribution of the SSH Brute-force attack duration in a multi-user environment

    Science.gov (United States)

    Lee, Jae-Kook; Kim, Sung-Jun; Park, Chan Yeol; Hong, Taeyoung; Chae, Huiseung

    2016-07-01

    Quite a number of cyber-attacks to be place against supercomputers that provide highperformance computing (HPC) services to public researcher. Particularly, although the secure shell protocol (SSH) brute-force attack is one of the traditional attack methods, it is still being used. Because stealth attacks that feign regular access may occur, they are even harder to detect. In this paper, we introduce methods to detect SSH brute-force attacks by analyzing the server's unsuccessful access logs and the firewall's drop events in a multi-user environment. Then, we analyze the durations of the SSH brute-force attacks that are detected by applying these methods. The results of an analysis of about 10 thousands attack source IP addresses show that the behaviors of abnormal users using SSH brute-force attacks are based on human dynamic characteristics of a typical heavy-tailed distribution.

  15. Handbook of biometric anti-spoofing trusted biometrics under spoofing attacks

    CERN Document Server

    Marcel, Sébastien; Li, Stan Z

    2014-01-01

    As the plethora of approaches to biometrics and their deployment continues to grow, so too does the need to combat the techniques used to subvert the aim of such biometric systems. Presenting the first definitive study of the subject, this Handbook of Biometric Anti-Spoofing reviews the state of the art in covert attacks against biometric systems, and in deriving countermeasures to these attacks. Across a range of common biometrics, including face, iris, fingerprint, speaker and gait, the book describes spoofing methods and examines the vulnerabilities of biometric systems to these attacks.

  16. Knowledge of Signs and Symptoms of Heart Attack and Stroke among Singapore Residents

    OpenAIRE

    Joy Li Juan Quah; Susan Yap; Si Oon Cheah; Yih Yng Ng; E. Shaun Goh; Nausheen Doctor; Benjamin Sieu-Hon Leong; Ling Tiah; Michael Yih Chong Chia; Marcus Eng Hock Ong

    2014-01-01

    Aim. To determine the level of knowledge of signs and symptoms of heart attack and stroke in Singapore resident population, in comparison to the global community. Methods. A population based, random sample of 7,840 household addresses was selected from a validated national sampling frame. Each participant was asked eight questions on signs and symptoms of heart attack and 10 questions on stroke. Results. The response rate was 65.2% with 4,192 respondents. The level of knowledge for preselec...

  17. Impact Angle Control of Interplanetary Shock Geoeffectiveness

    CERN Document Server

    Oliveira, D M

    2015-01-01

    We use OpenGGCM global MHD simulations to study the nightside magnetospheric, magnetotail, and ionospheric responses to interplanetary (IP) fa st forward shocks. Three cases are presented in this study: two inclined oblique shocks, here after IOS-1 and IOS-2, where the latter has a Mach number twice stronger than the former. Both shocks have impact angles of 30$^o$ in relation to the Sun-Earth line. Lastly, we choose a frontal perpendicular shock, FPS, whose shock normal is along the Sun-Earth line, with the same Mach number as IOS-1. We find that, in the IOS-1 case, due to the north-south asymmetry, the magnetotail is deflected southward, leading to a mild compression. The geomagnetic activity observed in the nightside ionosphere is then weak. On the other hand, in the head-on case, the FPS compresses the magnetotail from both sides symmetrically. This compression triggers a substorm allowing a larger amount of stored energy in the magnetotail to be released to the nightside ionosphere, resulting in stronger...

  18. Severe attacks of familial hemiplegic migraine, childhood epilepsy and ATP1A2 mutation.

    Science.gov (United States)

    Lebas, A; Guyant-Maréchal, L; Hannequin, D; Riant, F; Tournier-Lasserve, E; Parain, D

    2008-07-01

    We studied four members of a family suffering from typical attacks of familial hemiplegic migraine (FHM) caused by a new mutation, R548C, of ATP1A2 gene in exon 12. One individual had also childhood absence epilepsy and generalized tonic-clonic seizures (GTCS). GTCS were followed by a severe attack of hemiplegic migraine at four times. Sodium valproate enabled control of both the epileptic seizures and the most severe FHM attacks. This association of FHM and epileptic seizures and their control with the same treatment suggest similar pathophysiological mechanisms.

  19. Study of the advancing and receding contact angles: liquid sorption as a cause of contact angle hysteresis.

    Science.gov (United States)

    Lam, C N C; Wu, R; Li, D; Hair, M L; Neumann, A W

    2002-02-25

    Two types of experiments were used to study the behavior of both advancing and receding contact angles, namely the dynamic one-cycle contact angle (DOCA) and the dynamic cycling contact angle (DCCA) experiments. For the preliminary study, DOCA measurements of different liquids on different solids were performed using an automated axisymmetric drop shape analysis-profile (ADSA-P). From these experimental results, four patterns of receding contact angle were observed: (1) time-dependent receding contact angle; (2) constant receding contact angle; (3) 'stick/slip'; (4) no receding contact angle. For the purpose of illustration, results from four different solid surfaces are shown. These solids are: FC-732-coated surface; poly(methyl methacrylate/n-butyl methacrylate) [P(MMA/nBMA)]; poly(lactic acid) (DL-PLA); and poly(lactic/glycolic acid) 50/50 (DL-PLGA 50/50). Since most of the surfaces in our studies exhibit time dependence in the receding contact angle, a more extended study was conducted using only FC-732-coated surfaces to better understand the possible causes of decreasing receding contact angle and contact angle hysteresis. Contact angle measurements of 21 liquids from two homologous series (i.e. n-alkanes and 1-alcohols) and octamethylcyclotetrasiloxane (OCMTS) on FC-732-coated surfaces were performed. It is apparent that the contact angle hysteresis decreases with the chain length of the liquid. It was found that the receding contact angle equals the advancing angle when the alkane molecules are infinitely large. These results strongly suggest that the chain length and size of the liquid molecule could contribute to contact angle hysteresis phenomena. Furthermore, DCCA measurements of six liquids from the two homologous series on FC-732-coated surfaces were performed. With these experimental results, one can construe that the time dependence of contact angle hysteresis on relatively smooth and homogeneous surfaces is mainly caused by liquid retention

  20. Numerical aperture characteristics of angle-ended plastic optical fiber

    Science.gov (United States)

    Gao, Cheng; Farrell, Gerard

    2003-03-01

    With the increasing information rates demanded in consumer, automotive and aeronautical applications, a low cost and high performance physical transmission medium is required. Compared with Silica Optical Fiber, Plastic Optical Fiber (POF) offers an economic solution for a range of high-capacity, short-haul applications in industrial and military environments. Recently, a new type of POF, the perfluorinated graded-index plastic optical fiber (PF GI-POF), has been introduced that has low losses and high bandwidth at the communication wavelengths 850 nm and 1300nm. POF is normally terminated perpendicular to the fiber axis. We propose an angle-ended POF, which is terminated at non-perpendicular angles to the fiber axis. The aim of the research is to investigate the numerical aperture (NA) characteristics of angle-ended POF along the major axis of the elliptical endface. A theoretical model indicates that the NA of the angle-ended POF will increase nonlinearly with tilt-angle and the acceptance cone will be deflected with the angle of the deflection increasing nonlinearly with tilt-angle. We present results for the measured NA and the measured deflection angle using the far-field radiation method. Results are presented for 13 angle-ended SI-POF tilt-angles. We also present results for theoretical value of NA and deflection angle as a function of tilt-angle. The agreement between the measured and theoretical value is good up to tilt-angles of about 15 degrees, beyond which deviation occurs.

  1. Does the initiation of urate-lowering treatment during an acute gout attack prolong the current episode and precipitate recurrent attacks: a systematic literature review.

    Science.gov (United States)

    Eminaga, Fatma; Le-Carratt, Jonathan; Jones, Adrian; Abhishek, A

    2016-12-01

    The aim of this study was to systematically review the literature on effect of initiating urate-lowering treatment (ULT) during an acute attack of gout on duration of index attack and persistence on ULT. OVID (Medline), EMBASE and AMED were searched to identify randomized controlled trials (RCTs) of ULT initiation during acute gout attack published in English language. Two reviewers appraised the study quality and extracted data independently. Standardized mean difference (SMD) and relative risk (RR) were used to pool continuous and categorical data. Meta-analysis was carried out using STATA version 14. A total of 537 studies were selected. A total of 487 titles and abstracts were reviewed after removing duplicates. Three RCTs were identified. There was evidence from two high-quality studies that early initiation of allopurinol did not increase pain severity at days 10-15 [SMDpooled (95 % CI) 0.18 (-0.58, 0.93)]. Data from three studies suggested that initiation of ULT during an acute attack of gout did not associate with dropouts [RRpooled (95 % CI) 1.16 (0.58, 2.31)]. There is moderate-quality evidence that the initiation of ULT during an acute attack of gout does not increase pain severity and risk of ULT discontinuation. Larger studies are required to confirm these findings so that patients with acute gout can be initiated on ULT with confidence.

  2. Detection and Avoidance of SQL Injection Attack In Multi-Tier Web Based Application

    Directory of Open Access Journals (Sweden)

    Ms. S.Raichal

    2013-06-01

    Full Text Available The aim of this paper is to prevent sql injection attack using stored procedure. In SQL injection attack,an attacker might deliver malicious SQL query segments as user input which could effect in a different database request. Using SQL injection attacks, an attacker might thus obtain and modify confidential information. An attacker could even use a SQL injection vulnerability as a basic IP or Port scanner of the internal corporate network. The stored procedure does not permit conditional statement there by the hacker cannot identify the IDs. The stored procedure is the new approach that is executed. Stored procedure avoids the attack which is more secured one where the conditional statements are not permitted. In sql injection input is set as conditional statements and the user can able to login into the website. But in this paper every condition are checked in the procedural language of stored procedure.Once it notices the condition statement the user will be blocked to log into the website. Only the correct form of passwords is acceptable.

  3. On Linear Hulls, Statistical Saturation Attacks, PRESENT and a Cryptanalysis of PUFFIN

    DEFF Research Database (Denmark)

    Leander, Gregor

    2011-01-01

    We discuss complexities of advanced linear attacks. In particular, we argue why it is often more appropriate to examine the median of the complexity than the average value. Moreover, we apply our methods to the block ciphers PUFFIN and PRESENT. For PUFFIN, a 128 bit key cipher, we present an attack...... which breaks the cipher for at least a quarter of the keys with a complexity less than 258. In the case of PRESENT we show that the design is sound. The design criteria are sufficient to ensure the resistance against linear attacks, taking into account the notion of linear hulls. Finally, we show...

  4. Classification of HTTP Attacks: A Study on the ECML/PKDD 2007 Discovery Challenge

    Energy Technology Data Exchange (ETDEWEB)

    Gallagher, Brian [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Eliassi-Rad, Tina [Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)

    2009-07-08

    As the world becomes more reliant on Web applications for commercial, financial, and medical transactions, cyber attacks on the World Wide Web are increasing in frequency and severity. Web applications provide an attractive alternative to traditional desktop applications due to their accessibility and ease of deployment. However, the accessibility of Web applications also makes them extremely vulnerable to attack. This inherent vulnerability is intensified by the distributed nature ofWeb applications and the complexity of configuring application servers. These factors have led to a proliferation of Web-based attacks, in which attackers surreptitiously inject code into HTTP requests, allowing them to execute arbitrary commands on remote systems and perform malicious activities such as reading, altering, or destroying sensitive data. One approach for dealing with HTTP-based attacks is to identify malicious code in incoming HTTP requests and eliminate bad requests before they are processed. Using machine learning techniques, we can build a classifier to automatically label requests as “Valid” or “Attack.” For this study, we develop a simple, but effective HTTP attack classifier, based on the vector space model used commonly for Information Retrieval. Our classifier not only separates attacks from valid requests, but can also identify specific attack types (e.g., “SQL Injection” or “Path Traversal”). We demonstrate the effectiveness of our approach through experiments on the ECML/PKDD 2007 Discovery Challenge data set. Specifically, we show that our approach achieves higher precision and recall than previous methods. In addition, our approach has a number of desirable characteristics, including robustness to missing contextual information, interpretability of models, and scalability.

  5. DETECTION AND LOCALIZATION OF MULTIPLE SPOOFING ATTACKERS FOR MOBILE WIRELESS NETWORKS

    Directory of Open Access Journals (Sweden)

    R. Maivizhi

    2015-06-01

    Full Text Available The openness nature of wireless networks allows adversaries to easily launch variety of spoofing attacks and causes havoc in network performance. Recent approaches used Received Signal Strength (RSS traces, which only detect spoofing attacks in mobile wireless networks. However, it is not always desirable to use these methods as RSS values fluctuate significantly over time due to distance, noise and interference. In this paper, we discusses a novel approach, Mobile spOofing attack DEtection and Localization in WIireless Networks (MODELWIN system, which exploits location information about nodes to detect identity-based spoofing attacks in mobile wireless networks. Also, this approach determines the number of attackers who used the same node identity to masquerade as legitimate device. Moreover, multiple adversaries can be localized accurately. By eliminating attackers the proposed system enhances network performance. We have evaluated our technique through simulation using an 802.11 (WiFi network and an 802.15.4 (Zigbee networks. The results prove that MODELWIN can detect spoofing attacks with a very high detection rate and localize adversaries accurately.

  6. A MAC Layer Based Defense Architecture for Reduction of Quality (RoQ) Attacks in Wireless LAN

    CERN Document Server

    Singh, Jatinder; Kaur, Lakhwinder

    2010-01-01

    Recently an alternative of DDoS attacks called shrew attacks or Reduction of Quality (RoQ) has been identified which is very much difficult to detect. The RoQ attacks can use source and destination IP address spoofing, and they do not have distinct periodicity, and may not filter the attack packets precisely. In this paper, we propose to design the MAC layer based defense architecture for RoQ attacks in Wireless LAN which includes the detection and response stages. The attackers are detected by checking the RTS CTS packets from the MAC layer and the corresponding attack flows are blocked or rejected. By our simulation results, we show that our proposed technique achieves reduces the attack throughput there by increasing the received bandwidth and reducing the packet loss of legitimate users.

  7. Determination of the angle of attack on the mexico rotor using experimental data

    DEFF Research Database (Denmark)

    Yang, Hua; Shen, Wen Zhong; Sørensen, Jens Nørkær

    2010-01-01

    characteristics from experimental data on the MEXICO (Model Experiments in controlled Conditions) rotor. Detailed surface pressure and Particle Image Velocimetry (PIV) flow field at different rotor azimuth positions were examined for determining the sectional airfoil data. It is worthwhile noting that the present...

  8. Cycles of violence, and terrorist attacks index for the State of Oklahoma

    OpenAIRE

    Gómez-Sorzano, Gustavo

    2007-01-01

    I apply the Beveridge-Nelson business cycle decomposition method to the time series of per capita murder of Florida State (1933-2005). Separating out “permanent” from “cyclical” murder, I hypothesize that the cyclical part coincide with documented waves of organized crime, internal tensions, crime legislation, social, and political unrest, and with the periodic terrorist attacks to the U.S. The estimated cyclical component of murder shows that terrorist attacks against the U.S. have affecte...

  9. Comparative study of Attacks on AODV-based Mobile Ad Hoc Networks

    Directory of Open Access Journals (Sweden)

    Ipsa De

    2011-01-01

    Full Text Available In recent years, the use of mobile ad hoc networks (MANETs has been widespread in many applications, The lack of infrastructures in MANETs makes the detection and control of security hazards allthe more difficult. The security issue is becoming a major concern and bottle neck in the application of MANET. In this paper, an attempt has been made to thoroughly study the blackhole attack which is one ofthe possible attacks in ad hoc networks in routing protocol AODV with possible solution to blackhole attack detection.

  10. Knowledge of Signs and Symptoms of Heart Attack and Stroke among Singapore Residents

    Directory of Open Access Journals (Sweden)

    Joy Li Juan Quah

    2014-01-01

    Full Text Available Aim. To determine the level of knowledge of signs and symptoms of heart attack and stroke in Singapore resident population, in comparison to the global community. Methods. A population based, random sample of 7,840 household addresses was selected from a validated national sampling frame. Each participant was asked eight questions on signs and symptoms of heart attack and 10 questions on stroke. Results. The response rate was 65.2% with 4,192 respondents. The level of knowledge for preselected, common signs and symptoms of heart attack and stroke was 57.8% and 57.1%, respectively. The respondents scored a mean of 5.0 (SD 2.4 out of 8 for heart attack, while they scored a mean of 6.8 (SD 2.9 out of 10 for stroke. Respondents who were ≥50 years, with lower educational level, and unemployed/retired had the least knowledge about both conditions. The level of knowledge of signs and symptoms of heart attack and stroke in Singapore is comparable to USA and Canada. Conclusion. We found a comparable knowledge of stroke and heart attack signs and symptoms in the community to countries within the same economic, educational, and healthcare strata. However older persons, those with lower educational level and those who are unemployed/retired, require more public health education efforts.

  11. The Relationships Between Weather and Climate and Attacks of Bronchitis

    Science.gov (United States)

    Talaia, M. A. R.; Saraiva, M. A. C.; Vieira da Cruz, A. A.

    The area of Aveiro, more concretely Aveiro lagoon, a natural laboratory has been con- sidered, for promoting the development and the application of several investigations worked. The importance of the influences of weather and climate on human health has been well known since ancient teams and many decisions concerning human be- haviour it are clearly weather related. However, decisions related to weather criteria can be important and economically significant, but the real economic effect of the weather is difficult to assess. Talaia et al. (2000) and Talaia and Vieira da Cruz (2001) have shown the possible harmful effect of certain meteorological factors on respiratory conditions. Bronchitis is a disease caused by inflammation of the bronchi as a result of infectious agents or air pollutants. In this study our attention is to relate, the be- ginning of bronchitis attacks in the services of urgency of the Hospital of Aveiro with meteorological factors, and the risk group are studied. We used the medical records and the database of meteorological factors. The obtained analysis allows to conclude that some meteorological factors have correlation with the occurrences of the disease and to allow improving the work in the urgency services in the requested periods. The knowledge that will be extracted of this study can be used later in studies that inte- grate other important components for the characterisation of the environmental impact in the area. References: Talaia, M.A.R., Vieira da Cruz, A.A., Saraiva, M.A.C., Amaro, G.S., Oliveira, C.J. and Carvalho, C.F., 2000, The Influence of Meteorological Fac- tors on Pneumonia Emergencies in Aveiro, International Symposium on Human- Biometeorology, St. Petersburg (Pushkin), Russia, pp. 67-68. Talaia, M.A.R. and Vieira of Cruz, A.A., (2001), Meteorological Effects on the Resistance of the Body to Influenza - One Study in Aveiro Region, Proceedings 2nd Symposium of Meteorol- ogy and Geophysics of APMG and 3rd Meeting

  12. Effect of Blackhole Attack on Single Hop and Multihop Leach Protocol

    Directory of Open Access Journals (Sweden)

    Siddiq Iqbal,

    2014-05-01

    Full Text Available Wireless micro sensor networks provide reliable monitoring of remote areas for data-gathering. Due to the limited battery capacity of sensor nodes, energy consumption plays an important role in the operation of WSN. This can be improved by using a protocol called Low energy adaptive clustering hierarchy (LEACH.Malicious attacks are generated in the network due to power supply, processing abilities and capacity for high power radio transmission. In this paper one such attack namely BlackHole attack and its effect on single hop LEACH and multihop LEACH has been compared, simulated and analyzed.

  13. SIMULATION STUDY OF BLACKHOLE ATTACK IN THE MOBILE AD HOC NETWORKS

    Directory of Open Access Journals (Sweden)

    SHEENU SHARMA

    2009-06-01

    Full Text Available A wireless ad hoc network is a temporary network set up by wireless nodes usually moving randomly and communicating without a network infrastructure. Due to security vulnerabilities of the routing protocols, however, wireless ad hoc networks may be unprotected against attacks by the malicious nodes. In this study we investigated the effects of Blackhole attacks on the network performance. We simulated Blackhole attacks in Qualnet Simulator and measured the packet loss in the network with and without a blackhole. The simulation is done on AODV (Ad hoc On Demand Distance Vector Routing Protocol. The network performance in the presence of a blackhole is reduced up to 26%.

  14. 77 FR 56985 - Honoring the Victims of the Attack in Benghazi, Libya

    Science.gov (United States)

    2012-09-17

    ... Victims of the Attack in Benghazi, Libya By the President of the United States of America A Proclamation As a mark of respect for the memory of John Christopher Stevens, United States Ambassador to...

  15. Properties of tangential and radial angles of muons in EAS

    OpenAIRE

    Zabierowski, J.; Daumiller, K.; Doll, P.

    2002-01-01

    Tangential and radial angles of muons in EAS, a useful concept in investigation of the muon production height, can be used also for the investigation of the muon momenta. A parameter zeta, being a combination of tangential and radial angles, is introduced and its possible applications in investigation of muons in showers are presented.

  16. EVALUATION OF NECK SHAFT ANGLE OF FEMUR ON DRY BONES

    OpenAIRE

    Radha; Ravi Shankar; Naveen; Roopa

    2015-01-01

    BACKGROUND: Evaluation of the neck shaft angle of femur helps to understand clinical relevance in bio mechanics of the hip joint. It helps for the better treatment of different pathological conditions of hip and femur and also to design prosthesis. Femoral neck shaft angle is important to convey the information regarding the race to ...

  17. Advances in SCA and RF-DNA Fingerprinting Through Enhanced Linear Regression Attacks and Application of Random Forest Classifiers

    Science.gov (United States)

    2014-09-18

    CDF Cumulative Distribution Function CEMA Correlation Electro-Magnetic Attack DPA Differential Power Analysis DRA Dimensionality Reduction Assessment... CEMA ) SCA attacks are examined. A novel method to find time samples with high information leakage of sensitive data using the adjusted coefficient of...correlation R2a in a linear regression attack is introduced [92]. Three linear regression attacks from current literature [34, 50, 115] and CEMA [19] are

  18. Indirect Speculative Attacks and the Black Market for Foreing Exchange: The Example of Sudan Indirect Speculative Attacks and the Black Market for Foreing Exchange: The Example of Sudan

    Directory of Open Access Journals (Sweden)

    Ibrahim A. Elbadawi

    1993-03-01

    Full Text Available Indirect Speculative Attacks and the Black Market for Foreing Exchange: The Example of Sudan The paper extends the recent literature on collapsing exchange roles and balance of payment crises to the case when currency inconvertibility gives rise to the emergence of an "illegal" black market. The presence of the black market generates indirect speculative attacks on the official reserves because, due to inconvertibility, agents cannot directly buy official reserves. The paper derives several conditional probability statements regarding the likelihood of successful devaluation as a way to unify the official and black market exchange rates and achieve economic stabilization.

  19. Mortality and management of 96 shark attacks and development of a shark bite severity scoring system.

    Science.gov (United States)

    Lentz, Ashley K; Burgess, George H; Perrin, Karen; Brown, Jennifer A; Mozingo, David W; Lottenberg, Lawrence

    2010-01-01

    Humans share a fascination and fear of sharks. We predict that most shark attacks are nonfatal but require skilled, timely medical intervention. The development of a shark bite severity scoring scale will assist communication and understanding of such an injury. We retrospectively reviewed records of the prospectively maintained International Shark Attack File (ISAF) at the University of Florida. The ISAF contains 4409 investigations, including 2979 documented attacks, 96 of which have complete medical records. We developed a Shark-Induced Trauma (SIT) Scale and calculated the level of injury for each attack. Medical records were reviewed for the 96 documented shark attack victims since 1921. Calculated levels of injury in the SIT Scale reveal 40 Level 1 injuries (41.7%), 16 Level 2 injuries (16.7%), 18 Level 3 injuries (18.8%), 14 Level 4 injuries (14.6%), and eight Level 5 injuries (8.3%). The overall mortality of shark attacks was 8.3 per cent. However, SIT Scale Level 1 injuries comprised the greatest percentage of cases at 41.7 per cent. Injury to major vascular structures increases mortality and necessitates immediate medical attention and definitive care by a surgeon. Shark bites deserve recognition with prompt resuscitation, washout, débridement, and follow up for prevention of infection and closure of more complex wounds.

  20. Variable angle transmittance of silver grid transparent electrodes

    Science.gov (United States)

    Zhao, Yuan-Yuan; Zheng, Mei-Ling; Dong, Xian-Zi; Zhao, Zhen-Sheng; Duan, Xuan-Ming

    2016-10-01

    We focus on investigating the optical transmittance of silver grid transparent electrodes (SGTEs) in variable angle view theoretically and experimentally, rather than the optical transmittance under the normal incidence. The variable angle transmittance (VAT) values of SGTEs are measured on a home-made experimental setup. The experimental results about difference of the transmittance difference under different angles are small and negligible, although the measured angle is changed. Theoretically, the physical mechanism on nearly constant transmittance for different angle view can be well explained according to the theory of geometrical optics. This study provides an approach for investigating the VAT values of SGTEs in a controllable fashion and the influence of viewing angle of the touch screen.