Dissertations / Theses on the topic 'Lightning strike to aircraft'
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Mouratidis, Theodore. "Aircraft charging using ion emission for lightning strike mitigation : an experimental study." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/122708.
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Thesis: S.M., Massachusetts Institute of Technology, Department of Aeronautics and Astronautics, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 96-97).
Lighting strikes are a problem for aircraft flying in large external electric fields. In most cases, the strike is triggered by the aircraft; as it flies through an electric field, it becomes polarized, and on areas with small radius of curvature, the electric field is magnified. This can result in bidirectional leaders which extend from opposite polarity aircraft extremities. These can connect to oppositely charged regions in a cloud or the ground, resulting in a lightning strike. Current methods to avoid lightning are limited to avoiding thunderstorm regions, as recommended by weather radar or conversations between pilots and the ground. Methods to treat the symptom of a strike have been relatively successful; a mesh placed under the skin of the aircraft can distribute the current and heat of the localized strike. However, there are currently no active measures to prevent the strike from happening.
The Boeing Lightning Strike team at MIT has recently proposed an active system that exploits the physics of how a lightning arc is triggered from an aircraft in flight based on net charge control of the vehicle. The objective of this thesis is to prove the feasibility of controlling the net charge of an aircraft in flight by using ion emission from its surface. Different strategies to control the net charge of a flying isolated body were explored and analyzed. The first strategy tested was based on using charge emission from an electrospray source. A passive flow and forced flow configuration were tested, however it was shown that there were numerous difficulties associated with running the electrosprays in atmospheric pressure. To overcome the limitations of the electrospray source, a second strategy was tested based on a controlled corona discharge, which is known to have increasing current emission with increasing wind speed.
The first experiment was setup in the Wright Brothers Wind Tunnel; sharp tips were used to generate a corona discharge and a metallic sphere was used to simulate the aircraft. Significant electrical potential saturation was observed on the sphere, and it is likely this was due to the filamentary streamer corona regime which produces both positive and negative ions. Thus a new experiment was designed; a thin wire was used to generate a glow corona, which produces predominantly positive ions, and this was attached using GlO (a fiberglass composite material) to a metallically coated airfoil. Charging of much higher magnitudes was observed, indicating the glow corona regime is critically important in optimizing the potential of the airfoil. Charge control of an airfoil (Chord 0.2 m, Span 1 m) at 40 m/s was demonstrated to a level of -42 kV.
For an object of a given characteristic size, a certain amount of charge is required to satisfy the optimal charge condition, where negative and positive leader strikes are both equally likely or unlikely. The achieved potential of -42 kV is the order of magnitude required for this size airfoil based on the theoretical estimates, and these tests also showed a trend of linear potential variation with wind speed.
"Boeing Company for financially supporting my Research Assistantship"
by Theodore Mouratidis.
S.M.
S.M. Massachusetts Institute of Technology, Department of Aeronautics and Astronautics
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Zhang, Bangwei. "Manufacturing, characterization, and modeling of graphene-based nanocomposites for aircraft structural and lightning strike applications." Diss., Wichita State University, 2012. http://hdl.handle.net/10057/5591.
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Research and development of graphene and graphene-based materials have been attracting significant interest since they were invented. This dissertation mainly focused on the graphene-based materials: (a) a fundamental understanding of nanosize functionalized graphene inclusions in resin and fiber systems, (b) the development of graphene based hierarchical nanocomposites incorporated with thin layers of graphene papers, and carbon and glass fibers, and (c) the mathematical modeling of a process that can be useful for aircraft and wind turbine applications. Dispersion, wet layup, and vacuum-assisted resin transfer molding (VARTM) processes were used in the fabrication process, and then mechanical, thermal, electrical, and electromagnetic interference (EMI) properties of the materials were characterized using various techniques. Results of experiments conducted at different concentrations, thicknesses, pressures, and types of reinforcement materials show that the graphene-based fiber composites provided substantially better physical properties than other conventional carbon and glass-fiber-reinforced composites because of the extraordinary physical properties of graphene nanoflakes, rate of dispersion, and stronger covalent bonding between the resin and the reinforcement systems. MESOTEX (MEchanical Simulation of TEXtile) was utilized to predict the bulk-scale elastic modulus of the graphene-based fiber-reinforced composites. Graphene nanoflakes are assumed to be randomly and homogenously distributed in Epon 862 epoxy resin. Halpin-Tsai theories/equations were first used to simulate the tensile modulus of two phase graphene-based polymeric nanocomposites; however, today’s nanocomposite materials have three-phase structures. MESOTEX modeling results on variable laminate composite geometries confirmed that this modeling had a good prediction on a three-phase nanocomposite system and the test results indicated the existence of agglomeration effects on the properties of nanocomposites.Thesis (Ph.D.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Ashok, Kumar Sachin Sharma. "Incorporation of graphene thin films into the carbon fiber reinforced composite via 3d composite concept against the lightning strikes on composite aircraft." Thesis, Wichita State University, 2012. http://hdl.handle.net/10057/5592.
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Research and development of graphene and graphene based materials have been increasing significantly since they were invented. This report presents the development of a highly conductive graphene thin film (GTF) to reduce the damage of lightning effects on composite aircrafts. Furthermore, there are three new developments that are presented in this research: (a) the development of a highly conductive functionalized nanosize GTF, (b) a new approach of incorporating the GTF into the carbon fiber reinforced composite panel, and (c) a new development of 3D stitching concept were introduced specifically using polyester threads instead of fiber yarns that can be useful for the applications of aircraft protections against the effects of lightning strike. In addition, graphene was chemically functionalized and oxidized to form GTF. The highest electrical conductivity measured on the GTF was approximately 1800 S/cm. Furthermore, the GTF was then incorporated into the carbon fiber reinforced composite. Delamination was observed between the GTF and the composite. To investigate this issue, the composite was mechanically tested and there was a 40% decrease in tensile strength compared to the baseline. Therefore, 3D stitching concept was then introduced to reduce the delamination. Four stitch configurations having different stitch length, thread to thread thickness, thread tension, and thread thickness respectively were used in this study. 3D stitching was initially done on six sheets of unidirectional prepreg, MTM45-1 without the incorporation of GTF. Furthermore, mechanical testing was carried out and the stitch configuration that delivered the most appropriate result was then further used on twelve sheets of unidirectional prepreg, 5320. Here, three samples which was the baseline, 5320 with and without the incorporation of GTF respectively were prepared and mechanically tested, and the strength values were observed.Thesis (M.S.)--Wichita State University, College of Engineering, Dept. of Mechanical Engineering
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Wan, Ahmad Wan Fatinhamamah. "Modelling of lightning strike on an earth ground conductor." Thesis, University of Nottingham, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.438449.
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Lee, Steve H. K. "Route optimization model for strike aircraft." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1995. http://handle.dtic.mil/100.2/ADA306230.
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Mastrolembo, Giuseppe. "Understanding and optimising parameters for lightning strike testing of CFRP materials." Thesis, Cardiff University, 2017. http://orca.cf.ac.uk/113125/.
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In this thesis experimental tests and numerical simulations were carried out on the effects of the grounding system on CFRP test samples for the aerospace industry. The grounding system was assessed as one of the parts that can contribute to increasing the cost effectiveness of the sample and the relative test campaign. A numerical investigation was performed to understand the current distribution within anisotropic CFRP laminates. The influence of the grounding system and the interlaminar impedance on the current distribution were studied using parametric simulations and the results were compared. It was found that the side grounding system produces the best performance between the arrangements investigated. It allows for the best current spreading within the sample and for the lowest voltage drop between the injection and grounding points. Furthermore, it allows for the manufacturing of more cost effective test samples. However, a real implementation of the side grounding system introduces the contact pressure variable between the sample and the grounding electrode which influences the contact resistance. To implement the side grounding system, a test rig was designed and manufactured. This made it possible to control the compression force. A low current DC test campaign was carried out on five test samples with the same number of grounding systems. It was found that the contact resistance for the three side grounding systems is dependent on the compression force applied between the grounding electrode and the side of the sample. The influence was more pronounced for the sample without any metal coating on the side in contact with the electrode. Furthermore, the resistances measured for the two side grounding systems with metalized sides were comparable with the resistances measured for the fastener grounding systems. It was found in the literature that the variation of contact resistance due to compression force, for the side grounding cases, is related to variations in the topography of the surfaces in contact, specifically, the variations in the real contact area. Therefore, an investigation on the effects of the compression force on the surfaces in contact was carried out. It was found that the increase in compression force contributes to the decrease in the roughness mean; the increase in the material ratio curve which is a parameter related to the load bearing area; and the modification of the distribution of the height of the surfaces with the appearance of a negative tail. Further to the low current tests and the characterization of the surfaces of the side grounding samples a high current test campaign was performed. Through the use of typical lightning current waveforms, the thermal and electrical limits of the five grounding systems were investigated. The side grounding systems were tested at the maximum compression force to improve the contact area between the sample and the return electrode and therefore, decrease the risk of the sparking phenomena. The side grounding system paired with the sample with the metal sputtered side showed the best performance in terms of sustaining the highest current peak without appreciably increasing the risk of sparking phenomena at the contact interface between the sample and the IV return electrode. Conversely, the sample without any metal coating on its side showed the poorest performance, showing the sparking phenomena at the lowest current peak. The results of the thermal investigation were used for a visual validation of the numerical model created in the first part of the thesis. A comparison between a numerical model and an analytical model was performed. The dynamics of the temperature when a carbon fibres tow is subjected to a lightning current and thus to Joule effects were studied. The analytical model had the advantage of offering a simpler solution compared to the numerical model and a limited amount of data to input into the problem. The two models were found to produce similar results for the first transient of the temperature. However, the analytical model did not take into account the heat dissipation effects of the carbon fibres in the surrounding environment therefore, after the first transient the analytical model was found not to be as accurate as the numerical model.
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Ericsson, Max. "Simulating Bird Strike on Aircraft Composite Wing Leading Edge." Thesis, KTH, Hållfasthetslära (Inst.), 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-103783.
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In this master thesis project the possibility to model the response of a wing when subjected to bird strike using finite elements is analyzed. Since this transient event lasts only a few milliseconds the used solution method is explicit time integration. The wing is manufactured using carbon fiber laminate. Carbon fiber laminates have orthotropic material properties with different stiffness in different directions. Accordingly, there are damage mechanisms not considered when using metal that have to be modeled when using composites. One of these damage mechanisms is delamination which occurs when cured layers inside a component become separated. To simulate this phenomenon, multiple layers of shell elements with contact in between are used as a representation of the interface where a component is likely to delaminate. By comparing experimental and simulated results the model of delamination is verified and the influence of different parameters on the results is investigated. Furthermore, studies show that modeling delamination layers in each possible layer of a composite stack is not optimal due to the fact that the global stiffness of the laminate is decreased as more layers are modeled. However, multiple layers are needed in order to mitigate the spreading of delamination and obtain realistic delaminated zones. As the laminates are comprised of carbon fiber and epoxy sheets it is of importance to include damage mechanisms inside each individual sheet. Accordingly, a composite material model built into the software is used which considers tensile and compressive stress in fiber and epoxy. The strength limits are then set according to experimental test data. The bird is modeled using a mesh free technique called Smooth Particle Hydrodynamics using a material model with properties similar to a fluid. The internal pressure of the bird model is linked to the change in volume with an Equation of State. By examining the bird models behavior compared to experimental results it is determined to have a realistic impact on structures. A model of the leading edge is then subjected to bird strike according to European standards. The wing skin is penetrated indicating that reinforcements might be needed in order to protect valuable components inside the wing structure such as the fuel tank. However, the results are not completely accurate due to the fact that there is little experimental data available regarding soft body penetration of composite laminates. As a consequence, the simulation cannot be confirmed against real experimental results and further investigations are required in order to have confidence in modeling such events. Furthermore, the delamination due to the bird strike essentially spreads across the whole model. Since only one layer of delamination is included the spread is most likely overestimated.
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Bigand, Audrey. "Damage assessment on aircraft composite structure due to lightning constraints." Thesis, Toulouse, ISAE, 2020. http://www.theses.fr/2020ESAE0027.
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L’utilisation des matériaux composites dans l’industrie aéronautique s’étant largement étendue, ledimensionnement de ces structures et de leur protection vis-à-vis de la foudre est devenu un enjeu majeur. Ilest important de pouvoir développer des outils prédictifs permettant d’obtenir une conception de structurerépondant aux critères de certification avec des temps et coûts de conception maitrisés. L’interaction de lafoudre avec une structure composite est un phénomène multiphysique complexe, avec une difficulté ajoutéepar la présence d’une protection métallique en surface et d’une couche de peinture. Dans ce contexte, cetteétude a visé à développer la compréhension par rapport aux forces générées par la foudre et d’en évaluer sesconséquences quant à l’endommagement du composite. Dans cet objectif, le phénomène a d’abord étédécomposé pour en étudier ses différentes parties et définir l’impact des interactions. Dans un premier temps,l’arc libre a été comparé au pied d’arc en interaction avec différents substrats permettant de définir un modèlede vaporisation de la protection foudre. Dans un second temps, la surpression générée par l’explosion de laprotection en surface lors de la vaporisation a été évaluée pour définir des profils de pression spatio-temporels.Dans un troisième temps, une caractérisation mécanique de la peinture a été développée afin de quantifier soneffet de confinement sur l’explosion de surface. A chaque étape, une théorie a été développée et analysée viades modèles numériques et des essais. Enfin, ces trois différentes briques ont été rassemblées dans un modèlemécanique simulant l’impact foudre sur une structure composite afin d’en prédire l’endommagement. De plus,une loi utilisateur a été développée pour appliquer ce chargement complexe ainsi qu’une loid’endommagement. Ces modèles sont comparés aux résultats d’essai foudre en laboratoire afin d’endéterminer les limites de validité et leur capacité à prédire l'endommagementAs composite materials are now widely used in the aeronautical industry, the sizing of these structures andtheir protection against lightning has become a major issue. It is important to develop predictive tools to obtaina structure concept that meets certification requirements with a controlled time and cost during the designphase. The interaction of lightning with a composite structure is a complex multi-physics phenomenon, with afurther difficulty due to the presence of a metallic protection on the surface and a layer of paint. In this context,this study aimed to develop an understanding of the forces generated by lightning and to assess itsconsequences in terms of damage to the composite. To this end, the phenomenon was first broken down tostudy its different components and define the impact of their interactions. In a first step, the free arc wascompared to the arc root in interaction with different substrates to define a vaporisation model of the lightningprotection. In a second step, the overpressure generated by the explosion of the surface protection duringvaporisation was evaluated to define spatio-temporal pressure profiles. In a third step, a mechanicalcharacterization of the paint was developed in order to quantify its confinement effect on the surface explosion.At each stage, a theory was developed and analysed via numerical models and tests. Finally, these threedifferent bricks are brought together in a mechanical model simulating the lightning impact on a compositestructure in order to predict the damage. In addition, a user subroutine has been developed to apply thiscomplex loading as well as a damage law. These models are compared with lightning laboratory test results todetermine their validity limits and their ability to predict the damage
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Callahan, Jeremy. "Metrics of METOC forecast performance and operational impacts on carrier strike operations." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Sep%5FCallahan.pdf.
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Thesis (M.S. in Meteorology and Physical Oceanography)--Naval Postgraduate School, September 2006.Thesis Advisor(s): Tom Murphree, Rebecca Stone. "September 2006." Includes bibliographical references (p. 61-62). Also available in print.
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Tedrow, Christine Atkins. "Bird Strike Risk Assessment for United States Air Force Airfields and Aircraft." Thesis, Virginia Tech, 1998. http://hdl.handle.net/10919/40926.
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Analysis of strike data is critical to determine the true economic costs of bird strikes, determine the magnitude of safety issues, and develop preventive measures. Analysis of USAF bird-strike data identified trends and indicated suggested relationships among factors contributing to damaging strikes. From FY 1988 through FY 1997, the annual mean was 2,668 bird strikes with peaks evident in fall and spring. Daylight and dusk were hazardous for bird strikes. More bird strikes occurred during airfield operations - aircraft are at low altitudes and soaring birds are more numerous. Aircraft speed, phase of flight, taxonomic group, bird mass and aircraft group were the strongest predictors of damaging bird strikes. Bird strike rates were calculated for USAF aircraft and selected USAF airfields. Bomber aircraft had the highest strike rate; these aircraft frequently fly long missions at low altitudes where they are likely to encounter birds. Logistic regression analyses estimated odds of occurrence for damaging bird strikes during airfield operations. General statistics, odds for a damaging airfield strike, and airfield strike rates, were used to identify USAF airfields with higher bird strike risks. Howard AFB, Panama, had a higher number and rate of bird strikes, and greater odds for a damaging bird strike than other airfields analyzed.
This study allows recommendations for improving reporting of bird strikes and data management. Results will enable USAF to better estimate bird strike risks aircraft, better focus research on preventing bird strikes, and assess the effectiveness of bird management programs.Master of Science
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Evans, Simon. "Characterisation of outgassing from carbon fibre composite aircraft joints subjected to lightning current." Thesis, Cardiff University, 2018. http://orca.cf.ac.uk/117887/.
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Outgassing is a lightning direct effect that may occur at structural joints in the fuel laden volume of an aircraft. If uncontrolled, the event is extremely hazardous due to its potential to cause fuel vapour ignition. The aerospace industry has been aware of the threat for many years and lightning strike protection is well established. However, there is a lack of understanding particularly concerning the fundamental mechanisms for the creation of the event. Modern aircraft designs that utilise materials such as carbon fibre reinforced plastic (CFRP), are more dependent on manufacturing process control. Knowledge of the fundamental mechanisms responsible for outgassing can enable relaxation of specifications concerning manufacturing variables that exist, specifically, for the lightning protection of CFRP structures. Evidence from previous studies has revealed the significance of parameters relating to the interface between the fastener and the surrounding structure. However, the electrical parameter that drives the creation of the phenomenon remains unclear. The principle aim of this thesis was to determine a single measurable electrical parameter related to outgassing intensity in CFRP structures which can be used as a performance metric for the optimisation of lightning strike protection. Following the execution of three controlled experiments, it was found that outgassing intensity is a direct consequence of the magnitude of electrical energy absorbed, specifically, at the interface between the fastener shank and the surrounding CFRP structure. Characterisation techniques for robust voltage measurement and the distribution of current to the critical interface were developed to deduce the magnitude of energy absorption. This critical parameter can be now used as a control parameter in future aircraft development for the optimisation of lightning strike protection.
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Brown, Robert Jeffrey. "BIRD STRIKE HAZARDS AT AIRPORTS AND ASSESSMENT OF BIRD STRIKES AT A MIDWESTERN AIRPORT: 2000-2007." Miami University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=miami1229046725.
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Wang, Yeqing. "Modeling of lightning-induced thermal ablation damage in anisotropic composite materials and its application to wind turbine blades." Diss., University of Iowa, 2016. https://ir.uiowa.edu/etd/2164.
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A primary motivation for this research comes from the need to improve the ability of polymer-matrix composites to withstand lightning strikes. In particular, we are concerned with lightning strike damage in composite wind turbine blades. The direct effects of lightning strike on polymer-matrix composites often include rapid temperature rise, melting or burning at the lightning attachment points, and mechanical damage due to lightning-induced magnetic force and acoustic shock wave. The lightning strike damage accumulation problem is essentially multiphysic. The lightning plasma channel discharges an electric current up to 200 kA, inducing a severe heat flux at the surface of the composite structure, as well as generating Joule heating through the composite structure. The resulting electro-thermo-mechanical response of the composite structure may include matrix degradation and decomposition, delamination, and fiber breakage and sublimation, thus leading to catastrophic failure.
The existing studies related to the lightning strike damage in composites ignored the lightning channel radius expansion during the initial lightning discharge and lacked adequate treatment of material phase transitions. These assumptions significantly simplify the mathematical treatment of the problem and affect the predictive capabilities of the models. Another common feature of these limited studies is that they all focused on carbon-fiber-reinforced polymer-matrix (CFRP) composites, which are electrically conductive.
In the present thesis, the thermal responses and thermal ablations in a non-conductive glass-fiber-reinforced polymer-matrix (GFRP) composite wind turbine blade and in a conductive CFRP composite wind turbine blade are studied, respectively. In the case of non-conductive GFRP composite wind turbine blade, prior to the thermal response and thermal ablation analysis, a finite element analysis is performed to calculate the electric field due to lightning stepped leader to estimate the dielectric breakdown of the non-conductive composite wind turbine blade. The estimation of dielectric breakdown is used to determine whether Joule heating needs to be included in the problem formulation. To predict the thermal response and thermal ablation in the composite structure due to lightning strike, a physics-based model describing surface interaction between the lightning channel and the composite structure has been developed. The model consists of: (i) spatial and temporal evolution of the lightning channel as a function of the electric current waveform; (ii) temporary and spatially non-uniform heat flux and current density (in the case of electrically conductive CFRP composite or if dielectric breakdown occurs in the case of non-conductive GFRP composite) generated at the composite structure; and (iii) nonlinear transient heat transfer problem formulation for layered anisotropic composites that includes the moving boundary of the expanding lightning channel and the phase transition moving boundary associated with instantaneous material removal due to sublimation. The model has been employed to investigate the thermal responses and thermal ablations in a GFRP composite laminated panel used in a Sandia 100-meter all-glass baseline wind turbine blade (SNL 100-00) and a typical CFRP composite laminated panel subjected to lightning strike. The temperature-dependent directional material properties for both the GFRP and CFRP composites have been determined in this thesis using a micromechanics approach based on the experimental data for fibers and resin. An integrated Matlab-ABAQUS numerical procedure features the aforementioned aspects (i), (ii), and (iii) of the developed model. The obtained results include the evolution of temperature fields in the composite laminated panel and the progressive shape change of the composite laminated panel due to thermal ablation. The predictions of thermal ablation in the CFRP composite laminated panel are validated by reported experimental results.
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Bakis, Gökhan [Verfasser], and Volker [Akademischer Betreuer] Altstädt. "Towards electrically conductive and interleaf-toughened carbon black-epoxy-carbon fiber laminates with enhanced lightning strike resistance / Gökhan Bakis ; Betreuer: Volker Altstädt." Bayreuth : Universität Bayreuth, 2020. http://d-nb.info/1214297528/34.
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Milluzzi, Anthony J. "An Avian Target Processing Algorithm to Mitigate Bird Strike Risk in Aviation." Ohio University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1556144831508548.
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Hamilton, Marla Elizabeth. "Risk assessment of Bird Aircraft Strike Hazard for grassland birds at the McEntire Air National Guard Station, Eastover, South Carolina." Connect to this title online, 2009. http://etd.lib.clemson.edu/documents/1263409656/.
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Mertz, Julien. "Development of protecting coatings for composites in an aero-engine." Thesis, Luleå tekniska universitet, Materialvetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-87245.
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Carbon fibre reinforced polymer (CFRP) composite materials exhibit high specificstrength and stiffness therefore they can be a lightweight alternative to metalliccomponents for the front section of an aero-engine. Despite the benefit of CFRP composite materials for aero-engine applications, there arealso new challenges due to their inherent properties compared to conventionalaerospace metallic structures, such as a lower erosion resistance, poor thermalresistance, and poor electrical conductivity. In aero-engines, some components can be subjected to harsh erosive environmentsduring operation, therefore the erosion resistance of CFRP composite materials need tobe investigated. CFRP composites are not able to withstand as high temperatures astraditional metallic components and their ability to resist fire events need to beenhanced. On the other side, the poor electrical conductivity of CFRP composites canalso be critical when the aircraft is struck by lightning. Therefore, improving theconductivity of CFRP composite is of large interest. This thesis work is focusing on investigating innovative coating solutions to overcomethese three independent challenges in order to enhance CFRP composite applicationsinto the front section of an aero-engine. Coating systems for lightning strike protection have been investigated and developed.A fire protection has been identified and tested; the tests showed promising results forfire application. Furthermore, investigations on erosion resistant coatings indicated thepossible improvement of replacing the currently used erosion resistant coating by othercoatings presented in this thesis work.
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Lombetti, D. M. "Tufting of complex composite structures." Thesis, Cranfield University, 2015. http://dspace.lib.cranfield.ac.uk/handle/1826/11076.
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This study focuses on the effect of tufting on the mechanical and electrical properties of carbon composites using a variety of tuft materials, such as aramid, steel and copper. Several configurations were investigated based on a case study, involving the reinforcement of stiffener-to-skin interfaces of a tail cone. The effect of tuft and base composite material, tufting depth and inclination on the delamination resistance in mode I was evaluated, the associated bridging laws were determined and the failure mechanisms were identified. A simplified superposition model of the delamination response of tufted composites was developed. The electrical performance of tufted composites was determined in simulated lightning strike tests and set against the through-the-thickness electrical conductivity of the materials. The results of mechanical testing showed that the delamination performance depends strongly on the material response of the tufts, with both the bridging behaviour and final toughness levels influenced directly by the strength, ductility and ultimate strain of the tufts. Interactions between the tufts and the surrounding composite, such as interfacial shear and bridging induced by tuft pull-out, play a significant role in the overall behaviour generating a deviation from a simple superposition of the base material and tuft response. The balance between interfacial shear and tuft elongation results in a decreasing trend of delamination toughness with increasing tufting depth for low ductility materials, whilst the trend is reversed for the high ductility copper tufts. This balance is also affected by the properties of the base material, with tougher matrices leading to dominance of shear effects and a weaker enhancement introduced by tufting. Inclination of tufts leads to an increase in crack energy release rate due to the activation of a ploughing mechanism. Metallic and carbon tufts have a positive effect on lightning strike response, with copper tufting offering strike protection at an improved level compared to standard copper mesh solutions.
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Bedel, Vincent. "Mise en oeuvre et optimisation d'un revêtement conducteur poly(époxy) : fils submicroniques d'argent pour la protection foudre de structures aéronautiques." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30144/document.
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Ce travail s'inscrit dans une problématique de mise en œuvre et d'étude d'un revêtement conducteur polymère extrinsèque pour la protection foudre des structures aéronautiques de type composite polymère renforcé fibres de carbone (CFRP). Le revêtement est composé d'une matrice poly(époxy) haute performance bi-composant fluide à température ambiante et de fils submicroniques d'argent à haut facteur de forme (AgNWs) obtenus par un procédé polyol. Une attention particulière a été portée à l'étude de l'influence des AgNWs sur la modification de la cinétique de réticulation du système, sa structure physique et sa mobilité moléculaire. La mesure des niveaux de conductivité volumique et surfacique du revêtement met en avant un seuil de percolation électrique pour un taux volumique en AgNWs inférieur à 1%. Une approche originale permettant la détermination des mécanismes de conduction a été effectuée au moyen des mesures de densités de courant imposées dans le revêtement en fonction du taux de charge en AgNWs et de la température. L'analyse du comportement électrique des échantillons aux valeurs critiques de densités de courant a permis d'appréhender les phénomènes responsables des mécanismes de dégradation. Enfin des essais foudres ont été effectués sur des substrats représentatifs d'une structure aéronautique avec différents types de protection foudre. L'analyse des échantillons par ultrasons après essais foudres a mis en avant l'efficacité du revêtement composite polymère conducteur poly(époxy)/AgNWs développé pour lutter contre le délaminage structurel du CFRPThis work deals with the processing and the study of an extrinsic conductive polymer coating for the lightning strike protection of the aircraft carbon fibre reinforced polymer (CFRP) structural parts. The coating consist in a low viscosity bi component high performance poly(epoxy) matrix and silver submicronic wires with a high aspect ratio (AgNWs) obtained by a polyol process. The kinetic parameters, the physical structure and the molecular mobility of the matrix had been investigated as a function of the filler content. The surface and bulk conductivities had been measured as a function of filler content. It exhibits a percolation threshold below 1% in volume. The conduction mechanisms had been studied following an uncommon method of current density measurement as a function of the AgNWs content and the temperature. The critical electrical behaviour of each sample had been investigated through the current density method. It has permitted to understand the phenomenon responsible for the composite's degradation. Finally, lightning strike tests on representative configurations had been carried out. The ultrasonic inspections have highlighted the efficiency of the poly(epoxy)/AgNWs coating to avoid the structural delamination of the CFRP
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Großmann, Katja [Verfasser], and Klaus [Akademischer Betreuer] Pfeilsticker. "Aircraft-borne DOAS limb observations of UV/visible absorbing trace gas species over Borneo: Implications for the photochemistry of iodine, volatile organic oxide degradation, and lightning-produced radicals / Katja Großmann ; Betreuer: Klaus Pfeilsticker." Heidelberg : Universitätsbibliothek Heidelberg, 2014. http://d-nb.info/1180301099/34.
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Vogt, Juliane. "Modeling gap dynamics, succession, and disturbance regimes of mangrove forests." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-89901.
Full textAbstract:
Despite their important ecosystem benefits for terrestrial and marine flora and fauna and the human livelihood mangrove forests suffer a high loss rate mainly due to human activity. Aside from these impacts, natural forest disturbances exist more commonly in mangroves compared to other forests as a direct consequence of their exposed coastal location.
Within this thesis I investigate the influence of natural disturbance regimes on the mangrove forest dynamics focusing in particular on the ecological role of disturbances, disturbance patterns, forest structure, succession behavior and long-term vulnerability evaluation.
The study areas were set in the Indian River Lagoon in Florida (USA) and in Can Gio an UNESCO Biosphere Reserve (Vietnam). In addition, theoretical simulation studies were carried out to complement the field studies. Thereby, in our study at the Indian River Lagoon site I investigated the ecosystem response to hurricane events of an artificially impounded mangrove forest. In Can Gio, the suitability of lightning strike – caused gaps for setting a homogenous plantation into more natural-like state according to species composition and forest structure was analyzed. Finally, a theoretical simulation study was carried out to compare lightning strike and hurricane events regarding their homogenization and heterogenization effects on the spatio-temporal forest structure.
The findings of the field study in the Indian River Lagoon indicate that hurricane events had a severe impact on forest areas in higher successional stages by creating open patches, whereas areas in lower successional stages remained largely undisturbed. Furthermore, the impoundment determines the species selection of the post-hurricane succession by favoring flooding-tolerant species. However, regeneration was found to be impaired by the artificially high inundation regime at some disturbed patches.
The lightning-strike disturbances enhance the species composition in the monospecific plantation in Can Gio by providing a sufficient light regime for entering seeds to establish. In addition, lightning-strike gaps increased the plantation structure complexity. Regenerating lightning-strike gaps remained as “green islands” within windthrow sites in the plantation due to their low stature and provided seeds for surrounding disturbed areas thereby accelerating their recolonization.
The results of the simulation analysis of a theoretical landscape showed that in the simulated highly complex natural mature forests all disturbance regimes entail homogenization on the spatial structure compared to an undisturbed scenario. The hurricane scenario showed an increased temporal variation of the forest dynamics whereas lightning-strike gaps were not able to contribute to additional heterogeneity in the simulated area, despite of having the same tree mortality probability during disturbances.
The interaction of the large-scale impoundment in the Indian River Lagoon and medium-sized hurricane events is characterized by partially impeded post-hurricane regeneration. In contrast, small-scaled lightning strikes influenced the regeneration of medium-sized windthrow sites positively within the homogenous plantation.
We therefore suggest management activities aimed at creating small clearances within the plantation in Can Gio to simulate additional small-scale disturbances in order to facilitate heterogenization of the plantation structure. Natural disturbances are found to be able to enhance the species diversity and the interactions of ecological processes. In particular, where sustainable management strategies focused on maintaining ecosystem services especially in restored sites or plantations act as a supportive part.
Natural disturbances are an integral component of mangrove forests and fulfill specific ecological functions. However, our findings indicate that these disturbances, on top of altered environmental conditions associated with climate change and direct human impacts, might jeopardize the natural development in unnatural forest structures as on plantations or restored sites.
This thesis gives an extensive overview about the effect of various disturbances in different mangrove forest systems, including semi-natural forests and strongly modified plantations, on species composition and forest structure. Field studies and simulation analyses contribute in equal parts to the results of the thesis.
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Duhan, Daniel P. "Tactical decision aid for unmanned vehicles in maritime missions." Thesis, Monterey, California. Naval Postgraduate School, 2005. http://hdl.handle.net/10945/2274.
Full textAbstract:
Approved for public release; distribution is unlimitedAn increasing number of unmanned vehicles (UV) are being incorporated into maritime operations as organic elements of Expeditionary and Carrier Strike Groups for development of the recognized maritime picture. This thesis develops an analytically-based planning aid for allocating UVs to missions. Inputs include the inventory of UVs, sensors, their performance parameters, and operational scenarios. Operations are broken into mission critical functions: detection, identification, and collection. The model output assigns aggregated packages of UVs and sensors to one of the three functions within named areas of interest. A spreadsheet model uses conservative time-speed-distance calculations, and simplified mathematical models from search theory and queuing theory, to calculate measures of performance for possible assignments of UVs to missions. The spreadsheet model generates a matrix as input to a linear integer program assignment model which finds the best assignment of UVs to missions based on the user inputs and simplified models. The results provide the mission planner with quantitatively-based recommendations for unmanned vehicle mission tasking in challenging scenarios.
Lieutenant, United States Navy
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Данильченко, Дмитро Олексійович. "Захист ліній електропередавання з захищеними проводами від прямих ударів блискавки." Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/36492.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.14.02 - Електричні станції, мережі і системи (141 – Електроенергетика, електротехніка та електромеханіка). – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018.
Дисертація присвячена розв'язанню актуальної науково-прикладної задачі у галузі блискавко захисту повітряних ліній електропередавання із захищеними проводами середніх класів напруги від прямих ударів блискавки. В роботі експериментально доведено, що захищені проводи рідше вражаються прямими ударами блискавки, ніж неізольовані проводи. Це пов'язано з захисною оболонкою захищених проводів, оскільки умови виникнення зустрічного лідеру значно ускладнюються, то і зона захоплення блискавки значно зменшується. Діючі методики розрахунку кількості прямих ударів блискавки не враховують тип проводу на ПЛ, що призводить до не коректних розрахунків кількості прямих ударів блискавки, і, як наслідок, кількості вимкнень лінії. Отримані результати дозволили створити новий підхід до блискавкозахисту ПЛ з захищеними проводами, створити комбіновану лінію електропередавання. Ця лінія містить в своїй конструкції захищені проводи і неізольований провід, який виконує роль блискавкозахисного дроту. Створена модель комбінованої лінії була експериментально перевірена, жодного удару блискавки в захищені проводи зафіксовано не було.Dissertation for the degree of candidate of technical sciences (doctor of philosophy) in specialty 05.14.02 - Electric power stations, networks and systems (141 – Power engineering, electrical engineering and electromechanics). – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2018. The thesis is devoted to the solution of the current scientific and applied problem in the field of lightning protection of overhead transmission lines with protected wires of medium voltage classes from direct lightning strikes. In the work it has been experimentally proved that the protected wires are less likely to be struck by direct lightning strikes than bare wires. This is due to the protective envelope of the protected wires, since the conditions for the appearance of the oncoming streamer are significantly more complicated, then the lightning capture zone is significantly reduced. The current methods for calculating the number of direct lightning strikes do not take into account the type of wire on the overhead line, which leads to incorrect calculations of the number of direct lightning strikes, and, as a consequence, the number of line outages. The obtained results made it possible to create a new approach to lightning protection of overhead lines with protected wires, to create a combined power transmission line. This line contains in its design protected wires and bare wire, which acts as a lightning protection cable. The created model of the combined line was experimentally tested, not a single lightning strike into the protected wires was recorded.
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Данильченко, Дмитро Олексійович. "Захист ліній електропередавання з захищеними проводами від прямих ударів блискавки." Thesis, НТУ "ХПІ", 2018. http://repository.kpi.kharkov.ua/handle/KhPI-Press/36490.
Full textAbstract:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.14.02 - Електричні станції, мережі і системи (141 – Електроенергетика, електротехніка та електромеханіка). – Національний технічний університет "Харківський політехнічний інститут", Харків, 2018.
Дисертація присвячена розв'язанню актуальної науково-прикладної задачі у галузі блискавко захисту повітряних ліній електропередавання із захищеними проводами середніх класів напруги від прямих ударів блискавки. В роботі експериментально доведено, що захищені проводи рідше вражаються прямими ударами блискавки, ніж неізольовані проводи. Це пов'язано з захисною оболонкою захищених проводів, оскільки умови виникнення зустрічного лідеру значно ускладнюються, то і зона захоплення блискавки значно зменшується. Діючі методики розрахунку кількості прямих ударів блискавки не враховують тип проводу на ПЛ, що призводить до не коректних розрахунків кількості прямих ударів блискавки, і, як наслідок, кількості вимкнень лінії. Отримані результати дозволили створити новий підхід до блискавкозахисту ПЛ з захищеними проводами, створити комбіновану лінію електропередавання. Ця лінія містить в своїй конструкції захищені проводи і неізольований провід, який виконує роль блискавкозахисного дроту. Створена модель комбінованої лінії була експериментально перевірена, жодного удару блискавки в захищені проводи зафіксовано не було.Dissertation for the degree of candidate of technical sciences (doctor of philosophy) in specialty 05.14.02 - Electric power stations, networks and systems (141 – Power engineering, electrical engineering and electromechanics). – National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2018. The thesis is devoted to the solution of the current scientific and applied problem in the field of lightning protection of overhead transmission lines with protected wires of medium voltage classes from direct lightning strikes. In the work it has been experimentally proved that the protected wires are less likely to be struck by direct lightning strikes than bare wires. This is due to the protective envelope of the protected wires, since the conditions for the appearance of the oncoming streamer are significantly more complicated, then the lightning capture zone is significantly reduced. The current methods for calculating the number of direct lightning strikes do not take into account the type of wire on the overhead line, which leads to incorrect calculations of the number of direct lightning strikes, and, as a consequence, the number of line outages. The obtained results made it possible to create a new approach to lightning protection of overhead lines with protected wires, to create a combined power transmission line. This line contains in its design protected wires and bare wire, which acts as a lightning protection cable. The created model of the combined line was experimentally tested, not a single lightning strike into the protected wires was recorded.
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Vandeveld, Thierry F. R. "Etude expérimentale multisensorielle de la dynamique des impacts d'oiseaux sur structures d'avions." Doctoral thesis, Universite Libre de Bruxelles, 2009. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210274.
Full textAbstract:
Chaque année, d'innombrables collisions se produisent entre des avions en vol et des oiseaux. L'impact aviaire, menace redoutée par les pilotes, concerne tant l'aviation civile que son pendant militaire. Les statistiques démontrent que, même si fort heureusement le nombre d'accidents graves reste limité, les incidents sont de plus en plus nombreux.Parmi les acteurs qui luttent contre ce danger, les constructeurs d'avions jouent un rôle prépondérant. Contraints par des réglementations internationales, ils s'attachent à produire des éléments de structure qui résistent à l'impact d'oiseaux.
Dans la mise au point de leur produits, les avionneurs démontrent cette résistance à l'aide d'essais d'impact :on accélère un simulant d'oiseau jusqu'à la vitesse voulue -- de l'ordre de la vitesse de croisière nominale de l'avion -- et on le projette sur un aileron ou un morceau de fuselage.
La présente thèse doctorale, co-dirigée par les professeurs Philippe Bouillard de l'ULB et Marc Pirlot de l'ERM, contribue doublement à l'amélioration de ces techniques d'essais dynamiques.
D'une part, elle réalise la mise au point et la validation d'un lanceur pyrotechnique à double étage pour l'accélération du simulant d'oiseau. Un canon de calibre 20 mm est combiné avec un accélérateur de calibre 160 mm. La combustion d'un mélange de poudre propulsive contenu dans une douille adaptée génère les gaz à haute température et à haute pression nécessaires à l'accélération d'un simulant d'oiseau dûment confiné dans un conteneur de protection. Un dispositif de séparation arrête le conteneur afin que seul le simulant d'oiseau percute l'élément d'avion à l'essai. La solution pyrotechnique à double étage mise au point est validée par de nombreux tirs instrumentés en vitesse, en accélération et en pression ;elle se révèle conforme aux exigences de sécurité et de reproductibilité. Le lanceur pyrotechnique présente par rapport aux solutions pneumatiques, utilisées à notre connaissance dans tous les autres centres d'essais, des avantages indéniables de compacité ainsi que de rapidité et de souplesse de mise en oeuvre.
D'autre part, la migration des alliages métalliques vers les matériaux composites est amorcée depuis plusieurs années déjà dans le monde de la construction aéronautique. Pour optimiser les structures, une connaissance des caractéristiques de ces matériaux est indispensable. Les modes de rupture font partie des caractéristiques encore mal connues. La mesure du déplacement hors-plan lors du tir sur panneaux plans est une des manières de quantifier le comportement du matériau sous l'action d'un impact. Cette mesure s'opère généralement de manière statique, après le tir. Une méthode de mesure dynamique a été mise au point, basée sur l'emploi de techniques de stéréoscopie par corrélation numérique d'images. Cette technique a été validée au moyen d'une méthode métrologique indépendante d'extensométrie laser.
ABSTRACT
Countless collisions occur each year between airplanes and birds. Bird strike is a concern to both civilian and militay aircraft. Statistics show that, although the number of serious accidents fortunately remains low, the number of incidents keeps increasing.
Amongst the actors tackling this issue, aircraft manufacturers play an important role. In compliance with international regulations, they have to produce structural elements that withstand bird impact. During the development of their products, aircraft manufacturers have to demonstrate this resistance through bird impact trials :a bird surrogate is accelerated to the required velocity - often close to the nominal cruise speed of the aircraft - and launched onto a flap or a piece of fuselage.
This PhD thesis has been co-supervised by Professor Philippe Bouillard (ULB) and Professor Marc Pirlot (ERM-KMS). Its contribution to the improvement of the aforementioned dynamic trials is twofold.
One one hand, a two-stage pyrotechnical launcher for bird surrogates has been developed and assessed. A 20 mm caliber gun is connected to a 160 mm diameter launcher. The combustion of a propellant mixture in a cartridge case generates high pressure, high temperature gases which accelerate a bird surrogate protected by a cylindrical container. A stripper refrains the container from hitting the target pane.
The pyrotechnical solution has been assessed through an important number of firings where pressure, velocity and acceleration have been measured. The solution has proven compliance with both the safety requirements and the repeatability specifications. Its advantages compared to the pneumatic solutions used, as far as we know, in all other test centres, include compactedness as well as flexibility and high firing rate.
On the other hand, migration towards composite materials has been initiated years ago in the area of aeronautical constructions.
To optimize structures, a thorough knowledge of these new materials is required. Failure modes belong to the still badly known features of carbon reinforced plastics. Measuring the out-of-plane deformation when firing on a flat pane is one way of quantifying the material's behaviour under impact. This measurement is most frequently made in a static way, after completion of the firing. A dynamic measuring method has been developed, based upon stereoscopic digital image correlation techniques. This technique has been validated by means of an independent laser extensometer measuring method.
Doctorat en Sciences de l'ingénieur
info:eu-repo/semantics/nonPublished
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Wilson, David Joseph Humanities & Social Sciences Australian Defence Force Academy UNSW. "The eagle and the albatross : Australian aerial maritime operations 1921-1971." Awarded by:University of New South Wales - Australian Defence Force Academy. School of Humanities and Social Sciences, 2003. http://handle.unsw.edu.au/1959.4/38665.
Full textAbstract:
The aim of this thesis is to examine the relationship between the Royal Australian Air Force (RAAF) and the Royal Australian Navy (RAN) regarding the operation of aircraft from ships of the RAN and from RAAF shore bases. The effects of the separate intellectual development of maritime doctrine in the RAAF and RAN, and the efforts of the two Australian services to transfer theory into practice will be considered in the pre- (and post) World War II period, with due consideration of the experience of the services in both wars. The thesis will also discuss the problems that were faced by the RAAF and RAN to develop mutually acceptable operational procedures to enable the efficient use of aircraft in a maritime setting. The influence and effect on RAAF and RAN doctrine and equipment procurement, as a result of the special relationships that developed between the Air Force and Navy of Australia and Britain will be critically examined. A similar approach to the post war US/Australian relationship, and its effect on the Australian services, will also be critically examined. The thesis being propounded is that the development of a unique Australian maritime policy was retarded due to a combination of the relationship with Britain and the United States, lack of suitable equipment, lack of clear operational concepts in both the RAAF and RAN and the parochial attitude of the most senior commanders of both Services. The study has been based on Department of Navy, Department of Air and Department of Defence documents held in the National Archives of Australia in Canberra and Melbourne. In addition, relevant documents from the Admiralty and Air Ministry related to the development of naval aviation on RAN vessels during World War I, the attitude of the RAF toward the deployment of RAAF units to Singapore, and the negotiations that resulted in the procurement of HMA Ships Sydney and Melbourne, have been perused. Wartime operational records of the RAAF have been examined to obtain data to enable a critical study to be made of the RAAF anti-submarine campaign, torpedo bomber operations and the maritime campaign undertaken from bases in North Western Area during World War II. The influence of the commander of the United States 5th Air Force has also been incorporated in the discussion. The research uncovered procedural and operational variations between the two Services, the diversion of key elements from Australian command and the priority given to the American line of advance that resulted in Australian operations being given a secondary, supportive, status. A conclusion reached as a result of this research has been that the development of a unique Australian maritime aerial capability was restricted by the requirement of Britain to deploy flying units to Singapore in 1940. Similarly, the pressure exerted on the RAN by the Admiralty to purchase the Light Fleet Carriers in the late 1940s was more in the interests of the RN and British foreign policy than that of the RAN. Overall, the relationship with the Britain and the United States masked the real weakness in Australia???s maritime operations and retarded its development.
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Searle, Deane. "Low Intensity Conflict: Contemporary Approaches and Strategic Thinking." The University of Waikato, 2007. http://hdl.handle.net/10289/2591.
Full textAbstract:
Low Intensity Conflict (LIC) is a significant feature of the contemporary world and it is a particular challenge to the armed forces of many states which are involved is such conflict, or are likely to become so. This thesis is not concerned with how such difficult conflict situations arise. Rather it is concerned with how, from the point of view of the state, they may be contained and ultimately brought to a satisfactory resolution. The work is thus concerned with the practicalities of ending LIC. More specifically, the purpose of this research is to establish a framework of doctrinal and military principles applicable to the prevention and resolution of LIC. The principles of this thesis are based in numerous historical examples of LIC and six in depth case studies. These distilled principles are analysed in two central chapters, and are then applied in two latter defence force chapters so as to ensure there practicality and resilience. Numerous defence academics and military practitioners have been consulted in the production of this thesis; their contribution has further reinforced the functionality of the principles examined in this research. The research illustrates the criticality of a holistic approach to LIC. The function of this approach is to guarantee the stability of the sovereign state, by unifying civil, police, intelligence and military services. The effectiveness of the military elements must also be ensured, as military force is central to the suppression of LIC. Consequently, the research makes strategic and operational prescriptions, so as to improve the capability of defence forces that are concerned with preventing or resolving LIC.
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Berdahl, J. Scott. "Geological Effects on Lightning Strike Distributions." Thesis, 2016. http://hdl.handle.net/10754/610555.
Full textAbstract:
Recent advances in lightning detection networks allow for detailed mapping of lightning flash locations. Longstanding rumors of geological influence on cloud-to-ground (CG) lightning distribution and recent commercial claims based on such influence can now be tested empirically. If present, such influence could represent a new, cheap and efficient geophysical tool with applications in mineral, hydrothermal and oil exploration, regional geological mapping, and infrastructure planning.
This project applies statistical analysis to lightning data collected by the United States National Lightning Detection Network from 2006 through 2015 in order to assess whether the huge range in electrical conductivities of geological materials plays a role in the spatial distribution of CG lightning. CG flash densities are mapped for twelve areas in the contiguous United States and compared to elevation and geology, as well as to the locations of faults, railroads and tall towers including wind turbines. Overall spatial randomness is assessed, along with spatial correlation of attributes. Negative and positive polarity lightning are considered separately and together. Topography and tower locations show a strong influence on CG distribution patterns. Geology, faults and railroads do not. This suggests that ground conductivity is not an important factor in determining lightning strike location on scales larger than current flash location accuracies, which are generally several hundred meters. Once a lightning channel is established, however, ground properties at the contact point may play a role in determining properties of the subsequent stroke.
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Hanuta, Irene. "A lightning climatology for Manitoba using cloud-to-ground strike data from a lightning detection network." 1989. http://hdl.handle.net/1993/7183.
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While thunderstorm data have been traditionally collected at first order weather stations, this thesis uses lightning detector data with a higher spatial and temporal resolution as a source of thunderstorm information. Cloud-to-ground lightning strike data for Manitoba during 1985 have been analyzed for spatial variability and diurnal/seasonal distribution. Almost 68 000 strikes were detected over a four month period with July recording the most activity. Three areas of the province had the greatest concentration of lightning strikes, indicating some influence by topography and position of large lakes. Comparisons are made between thunderstorm climatologies derived from lightning detectors and those from weather stations. Forest fire and Manitoba Hydro disruption data are compared with lightning distributions. A selection of the most active lightning storms was chosen in order to study associated weather patterns.
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Bacci, Nicholas. "Traumatic effects of lightning strike on human bone morphology and ultrastructure." Thesis, 2016. http://hdl.handle.net/10539/21230.
Full textAbstract:
A Dissertation submitted to the Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, in fulfilment of the requirements for the degree of Master of Science
FACULTY OF HEALTH SCIENCES
UNIVERSITY OF THE WITWATERSRAND, JOHANNESBURG
2016South Africa reports lightning fatality rates as high as 8.8 per million annually. Traditionally, forensic lightning fatality identification consists of soft tissue traumatic pattern recognition. This does not allow for manner of death identification in cases of full skeletonization. This study has expanded upon our earlier research, which identified characteristic patterns of lightning disruption in non-human bone. We thus explored the effects of induced lightning high voltage current on human cadaveric material in order to recognise electrically induced trauma. The objectives comprised analysis of microstructural damage through conventional thin-section histology, micro-focus computed tomography and histomorphometry. Experimentation was undertaken on bone blocks extracted from human lower limbs obtained from cadaveric specimens. An experimental system for simulated lightning induction to bone was developed and investigations were carried out on twenty-two bone block specimens. Micro-focus computed tomography was undertaken prior and after experimental treatment; while three blocks were used unmodified as control samples. Thin sections were obtained following post-trauma imaging. Measurements and photomicrographs of the alteration patterns were taken, while micro-focus computed tomography data were reconstructed and visualised as 2D orthoslices and 3D rendered volumes. Results indicated a poor efficiency of micro-focus computed tomography to resolve traumatic features in cortical bone. However, conventional histological methods demonstrated cortical bone trauma patterns well, allowing easy identification. Statistical analyses demonstrated relationships between current intensity and extent as well as typology of damage observed. The relationships identified suggested a dual mechanism of bone trauma, consisting of a combination of both electrically and thermally induced alterations. This study has thus allowed a primary overview and analysis of lightning trauma to human skeletal tissues.
MT2016
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Huang, Chih-Min, and 黃志民. "An Analysis of Transient of Transmission Lines Caused by a Lightning Strike." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/33814087254190881017.
Full textAbstract:
碩士逢甲大學
電機工程所
94
The purpose of this study was to analyze the transient phenomena of transmission lines and towers with and without line arresters caused by lightning strokes, through which the specifications of structure design were modified in order to improve the reliability of power transmission. From this premise, by using ATP Draw model, three power configuration modes of the 345kv overhead transmission lines and towers were simulated and analyzed: (1) The four phases JMarti transmission line module (applied to overhead transmission lines with shields) joined the single phase distributive parameters Z module (used to simulate the field conditions of towers). (2) The single phase JMarti simulated for shield lines joined the single phase distributive parameters Z module for tower, and the three phases distributive parameters Z-T module for overhead transmission lines without shields. (3) The single phase distributive parameters Z module simulated for shield lines and towers joined the three phase distributive parameters Z-T modules for overhead transmission lines. In addition, the researcher sought to reply to other relevant modes set out in the literature to evaluate the present simulated conditions by way ofATP Draw. The results provided some evidence of the effectiveness of the aforementioned three modes.
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Alonso, Daniel Filipe Moreira. "Numerical modelling of damage induced by lightning strike events in composite plates." Master's thesis, 2019. https://hdl.handle.net/10216/124304.
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Zhang, Wei-Yu, and 張瑋育. "Simulation and Analysis of Lightning Strike Protection and Protection Margin for Secondary Substation." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/665z84.
Full textAbstract:
碩士國立高雄應用科技大學
電機工程系博碩士班
102
This study is developing lightning strike protection for S/S (Secondary Substation) and protection margin simulation analysis. To protect arresters on transmission lines or substation outdoor, Taipower applies ZnO Arresters widely used for its characteristics as non-linear, fast-response, great absorptive capacity, and non-continuity. In this ATP-EMTP to simulate whether S/S outside meets protection margin criteria of ANSI/IEEE under various lightning current and analyze the relationship between arresters location and protection margin. Based on the results, this study builds up lightning strike protection model for S/S and sets up transmission equipment parameters. Through this model, power designers will figure the characteristics of substation and plan the quantities and location of Arresters with fair cost while substation rebuilding.
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ZHENG, JING-FU, and 鄭景富. "Analysis of Lightning Strike Accident Simulation and Prevention Strategy in Transmission Line Maintenance." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/8pafav.
Full textAbstract:
碩士國立虎尾科技大學
電機工程系碩士在職專班
107
This paper uses the TFlah software simulation analysis. When the overhead transmission line is subjected to different lightning currents, the insulation hinders the flashover and causes the line to jump and the voltage suddenly. The simulation is 161kV Jiamin E/S to Dougong P/S red line, #29 tower to #43 tower two return line overhead transmission line. It is necessary to first familiarize with the basic operation of the software, and set lightning protection measures according to local lightning density, frequency, and lightning classification to reduce lightning blackouts. General lightning strike accident improvement methods include reducing the grounding resistance of the tower tower foot, installing the line arrester, strengthening the insulation strength, adding the coupling ground line and increasing the width of the ground line to prevent lightning protection. The research results can be used as a reference for lightning protection design of overhead transmission lines. At the same time, the "Lightning Strike Information Platform" also revealed that the accident was caused by frequent lightning strikes, which ensured that the line was struck by lightning and the simulation results were mutually verified, thereby improving the overall power supply stability and quality of the transmission line.
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Pan, Po-Hsun, and 潘柏勳. "Computation of Magnetic Intensity and Analysis of Lightning Strike in Taiwan High Speed Railway." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/01425089054151611637.
Full textAbstract:
碩士國立雲林科技大學
電機工程系碩士班
93
This thesis is divided into two parts. The first part calculates magnetic intensities of power-contact-wire exposure in Taiwan High Speed Railway (THSR). The new equation derived by Biot-Savart Law is used in this paper. It takes into account of conductor’s size, operating temperature, conductivity of contact wire as well as the skin effect. Thus, it can be accurate to estimate the distribution of magnetic intensities of the conductor. The second part is to simulate the lightning strike on the catenary in THSR. The structure of catenary and grounding systems can be constructed accurately by using CDEGS software packages. The efficiency of arrester location will be estimated when the lightning strike on the return feeder and the contact wire; furthermore, we discuss the phenomenon of back-flashover on the pole and the overhead grounding wire. Based on the simulation results, the improvement policy and method are concluded at the end.
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WU, SZU-YI, and 吳思儀. "A Study of the Bird-Strike Prevention on Aircraft Type for Gangshan Airport." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/7ssv3t.
Full textAbstract:
碩士高苑科技大學
資訊科技應用研究所
106
A reference to the safety of the aircraft is the safety of people's lives and the cost of aircraft damage. In the event of flying accident not only caused huge damage to the property is more likely to directly endanger the safety of personnel on board. "Bird Strike" is the most difficult to avoid in flight and the most hard to expect the occurrence of flying security incident, so the prevention of bird strike is even more important. According to the study the occurrence and severity of the bird strike will vary depending on the type of aircraft. With the modern technological progress and people’s promotion of the safety protection and conservation awareness, it gradually developed a different ways on bird strike prevention.
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Ngqungqa, Sphiwe Hamilton. "A critical evaluation and analysis of methods of determining the number of times that lightning will strike a structure." Thesis, 2006. http://hdl.handle.net/10539/1594.
Full textAbstract:
Faculty of Engineering & Built Environment, School of Electrical & Info Engineering, DissertationThe primary objective of this paper is to present results regarding data obtained from Eskom’s Lightning Positioning and Tracking System (LPATS) and is a continuation of the work presented at the two SAUPEC Conferences in Pretoria and Stellenbosch [1, 2]. LPATS provides some useful information regarding the lightning field measurements around the Brixton and Hillbrow Towers, in Johannesburg, for the two seasons of June 2001 to June 2003. The results suggest that there is a significant increase in apparent ground flash density in the vicinity of the towers when compared to the surrounding areas. The observation of mean current values in the order of -20kA suggests that the increased contribution of upward flashes to the total incidence of flashes in tall structures should lead to a decrease in measured current amplitudes.
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Yang, Shuxin. "The effect of soil resistivity on the LV surge environment." Thesis, 2007. http://hdl.handle.net/10539/1993.
Full textAbstract:
Student Number : 0418388R -
MSc(Eng) research report -
School of Electrical and Information Engineering -
Faculty of Engineering and the Built EnvironmentDue to the high soil resistivities and high frequency of lightning strikes in South Africa, the background theory about the effect of soil resistivity on the LV surge environment is important, but the present local and international standards do not give reasonable explanations for this effect. The previously published experimental results and research results related to this effect were investigated. From these investigations, it can be shown that the soil resistivity can affect surge generation, surge propagation and surge attenuation significantly. Also, soil resistivity plays a main role in the lightning surges caused by both direct strikes and indirect strikes, which can cause severe damage to the LV distribution system. Soil resistivity also has a significant impact on the resistance of an earth electrode.
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Milroy, Andrew G. "Impacts of Mowing on Bird Abundance, Distribution, and Hazards to Aircraft at Westover Air Reserve Base, Massachusetts." 2007. https://scholarworks.umass.edu/theses/22.
Full textAbstract:
Few studies have measured the impacts of mowing on bird use of habitat and the risk of bird collisions with aircraft on North American airfields. The need for this research has increased as airfields become some of the only large contiguous grasslands available to rare migratory birds in some areas. I studied bird abundance, distribution and behaviors at Westover Air Reserve Base, Massachusetts, USA in June and July 2004. I compared my data with bird strike records to discern any patterns associated with mowing of airfield vegetation. There was no difference in total number of birds or species between mowed and unmowed plots adjacent to runways and taxiways. There were more Upland Sandpipers and Eastern Meadowlarks in mowed vegetation and more sparrows (Grasshopper and Savannah) in unmowed vegetation. From 1997 to 2005, swallows were the birds most often struck by aircraft in June and July at Westover, and were also the second most numerous birds in both mowed and unmowed plots. Bird species that pose high Bird/Wildlife Aircraft Strike Hazard (BASH) risk at Westover included Turkey Vulture, Red-tailed Hawk, Great Blue Heron, and Canada Goose. I did not observe those species in paired plots of mowed or unmowed airfield vegetation adjacent to runways and taxiways at Westover. I opportunistically observed 64 incidents where species that pose high BASH risk were in or adjacent to areas where aircraft operate. Birds struck most frequently at Westover between April 1997 and January 2005 were “swallows”, American Kestrel, Killdeer, Horned Lark, Eastern Meadowlark, and Mourning Dove. Current mowing practices at Westover may have adverse effects on Upland Sandpiper and Grasshopper Sparrow, both state-listed, rare, grassland birds, but may not measurably reduce overall risk to aircraft, given the continued presence of large, high BASH risk species. I recommend methods to reduce threats posed by high-risk species at Westover, and further research to seek ways to reduce adverse effects of mowing on state-listed, rare, migratory species of birds.
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Goldsmith, Sam. "China’s Anti-Access & Area-Denial operational concept and the dilemmas for Japan." Master's thesis, 2012. http://hdl.handle.net/1885/9721.
Full textAbstract:
The People's Republic of China is developing a sophisticated Anti-Access/Area-Denial operational concept utilising a variety of defensive military capabilities, entwined with offensive components. The United States, Japan and other Asia-Pacific countries remain sceptical about China's defensive rationale for developing this operational concept because it threatens to undermine Asia-Pacific security. Specifically, the threat posed by China's military modernisation to the security of Japan may force the Japanese Government to adopt a more self-reliant defence posture. However, there are a variety of factors that complicate Japan's perception of China and restrict the number of feasible response options open to the Japanese Government. As such, this sub-thesis will examine the nature of China's Anti-Access/Area-Denial operational concept in addition to the factors complicating Japan's response and finally the ways that Japan may respond to the rising power of China.