Dissertations / Theses on the topic 'Imact dynamics'
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Wagg, David James. "Vibro-impact dynamics of engineering systems." Thesis, University College London (University of London), 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.314220.
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Yeow, Hoe Chian. "Soil classification through dynamic soil signatures." Thesis, University of Aberdeen, 1990. http://digitool.abdn.ac.uk/R?func=search-advanced-go&find_code1=WSN&request1=AAIU031990.
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The demand for a cost effective site investigation method has resulted in the introduction of various advanced in-situ testing techniques. These techniques utilise modern electronics instrumentation to monitor various soil parameters during site investigation. The data is then processed using high speed, low cost digital computers which allow an accurate and rapid assessment of the conditions of the foundation soil under a proposed construction site. In this thesis, a site investigation tool that drives a coring tube into the ground under a combination of vibration and impact is considered. This machine, called a vibro-impact corer, is fully instrumented to provide penetrometer-type information and a core sample for further inspection in the laboratory. The self-adjusting mechanism inherent in this machine delivers the minimum level of energy required to overcome soil resistance which thereby allows continuous penetration of the coring tube. This mechanism is also results in minimal induced disturbance during the coring process. This thesis investigates use of the vibro-impact corer as a soil classification tool. It involves the design of data analysis software to perform the soil classification procedure. Due to the nature of the system, the resistance monitored through the annular load cell fitted at the tip of the coring tube consists of the dynamic end resistance waveform and the peak magnitude of these waveforms over a sampling period. The vibro-impact soil classification system is based on the distinct self-adjusting mechanism of the machine. The self-adjustment mechanism imparts a different level of impact and vibration as soil conditions change which produces distinct dynamic soil resistance waveforms. In addition, the penetration rate and the magnitude of the soil resistance encountered also varies according to the material being penetrated. These two features are used to form the basis of the soil classification system in this software. The software also includes options for empirical correlation of the results obtained from the vibro-impact penetrometer with the CPT and SPT tests to allow comparison. The vibro-impact soil classification software is designed to be user-friendly. It reads the data files from a Biodata Transient Capture System for the classification process. The output devices such as plotter and printer are used to produce hardcopy records for various data. All the options are menu driven. A two degree freedom simulation of the operational responses of the vibro-impact machine is also included in this thesis. The main objective of this simulation is to study the soil response during vibro-impact mode of driving. This allows a comparison of the simulation soil responses to the model test results to provide an understanding of the soil behaviour under a combination of both vibratory and impact loadings. This thesis presents the results of several laboratory model and full scale vibro-impact penetrometer tests. It concentrates on the main subject of soil classification during the discussions although in some occasions the operational mechanism of the machine is mentioned. The results justify the approaches adopted for the soil classification system using a vibro-impact machine.
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Anandika, Muhammad Nevin. "An Experimental Investigation of the Impact of Random Spacing Errors onthe Transmission Error of Spur and Helical Gear Pairs." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574680868815187.
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Knudsen, Jakob. "Vibro-impact dynamics of fretting wear." Licentiate thesis, Luleå tekniska universitet, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-18592.
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The dynamics and wear of non-linear impact oscillators, comprising a single-degree of freedom system as well as continuous beam systems are analysed. The considered beams are of cantilever type with the lateral motion of the free end constrained by elastic supports. They are modelled as Bernoulli beams with Rayleigh damping. A finite-element method is used for discretisation in space and Newmark's method for time integration. Wear is quantified using the work-rate concept. The model calculations are compared with measurements of contact forces and displacements made on a loosely supported nuclear fuel rod span subject to both harmonic and random excitation. Details of the vibro-impact dynamics in the time domain are well reproduced in the digital simulations. Work-rates computed from measured and simulated quantities are also in good agreement. Furthermore, the dynamics of vibro-impacts are characterised through global and local stability and bifurcation analysis. Global analysis is made by extensive time integration for both harmonic and stochastic excitation. The local analysis is made by way of a Poincaré mapping method relating the states at subsequent impacts at the elastic supports for harmonically excited systems. The domains of stability are mapped out and the work-rate at stable periodic orbits is examined.Godkänd; 2001; 20070225 (ysko)
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DI, BENEDETTO GIOVANNI. "Impact dynamics of tool steel penetrators." Doctoral thesis, Politecnico di Torino, 2017. http://hdl.handle.net/11583/2678424.
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Armor-piercing (AP) ammunition generally carries a hard penetrator within a copper jacket. Upon
impact on a hard target, the copper case is destroyed, but the penetrator continues its motion and
pierces the target.
The most efficient AP ammunition is built with penetrators made from either tungsten alloys or
depleted uranium, but alloy steel penetrators are also commonly used, because they are less
expensive and less polluting, even if they are much less efficient.
The impact deformation and fracture behavior of armor-piercing penetrators fabricated with three
tool steels, and their resultant ballistic efficiency, are investigated, both to better understand the
optimal mechanical properties of armor piercing materials, and to describe the fracture mechanics
of the tested materials. Moreover, the ballistic results of the three tool steels are compared with
those of plain medium-carbon steel and cemented tungsten carbide.
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Gao, Fan. "The Impact Dynamics of Weakly Charged Droplets." Diss., Virginia Tech, 2019. http://hdl.handle.net/10919/92888.
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Electric charges are often found in naturally or artificially formed droplets, such as raindrops and those generated by Kelvin's water dropper. In contrast to the impact of neutral droplets on a flat solid surface upon which a thin convex lens shape layer of the gas film is typically formed, I show that the delicate gas thin film can be fundamentally altered for even weakly charged droplets both experimentally and numerically. As the charge level is raised above a critical level of about 1% of the Rayleigh limit for representative impact conditions, the Maxwell stress overcomes the gas pressure buildup to deform the droplet bottom surface. A conical liquid tip forms and pierces Through the gas film, leading to a circular contact line moving outwards that does not trap any gas. The critical charge level only depends on the capillary number based on the gas viscosity. The deformation applies to common liquids and molten alloy droplets. Even dielectric surfaces can also induce conical deformation. The charged droplets can also deform upon hydrophobic surfaces, and increase the contact time on hydrophobic surfaces or even avoid bouncing.Doctor of Philosophy
Electric charges are often found in naturally or artificially formed droplets, such as raindrops, waterfall, and inkjet printer. Neutral droplets impact on flat surfaces will usually trap a bubble inside because of the viscosity of air. The air bubble entrapped can be ignored if the droplet is water because the air bubble will eventually pinch-off. However, if the droplet is metal or some other viscous liquid, the air bubble will stay inside the liquid. This entrapped air bubble is undesired under some circumstances. For example, the existence of air bubble during metal 3D printing can influence the physical property. I show that the delicate gas thin film can be fundamentally altered for even weakly charged droplets both experimentally and numerically. As the charge level is raised above a critical level of about 1% of the maximum charges a droplet can carry for representative impact conditions, the electric stress will dominate the deformation of droplet. A conical liquid tip forms at the droplet bottom, avoiding the entrapment of air bubble. The critical charge level is experimentally proved to be only dependent on the gas viscosity and impact velocity. The deformation applies to common liquids and molten alloy droplets. Even dielectric surfaces can also induce conical deformation. The charged droplets can also deform upon hydrophobic surfaces, and increase the contact time on hydrophobic surfaces or even avoid bouncing.
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Murias, dos Santos Antonio E. Ferrand de Almeida. "Intertidal ecology of northern Portuguese rocky shores." Thesis, University of Southampton, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.326590.
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Soundranayagam, Sally Ann. "Investigation of nonlinear transformation of impulses in impact units for improvement of hammer drill performance." Thesis, Loughborough University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324489.
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Matzinger, Thomas. "An Overview of Body Armor and Single Plate Impact Dynamics." DigitalCommons@CalPoly, 2018. https://digitalcommons.calpoly.edu/theses/1808.
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In the past, personal body armor was constructed of simple plates of high- strength alloys. However, with the advancement of modern combat and weaponry, particularly armor-piercing ammunition, personal body armor has evolved into more complex and effective metal, ceramic, and composite structures. This paper lays the groundwork for experimental and modeling methods used to understand the effectiveness of new armor designs. Focusing on the first layer of modern body armor, the ”High Impedance” layer. Experiments measuring the change in velocity of bullets passing through aluminum and titanium plates were conducted. These experiments were then replicated through FEA simulation.
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Emms, Rhys Mullin. "Impact of Plasma Dynamics On Femtosecond Filamentation." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/35126.
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In this thesis we ran a series of 2D simulations of femtosecond laser pulses filamenting in air using the FDTD method, a saturable Lorentz oscillator model of air [1], and two separate models of plasma: a Drude model where the plasma density is static in space, and a particle-in-cell model where plasma is free to migrate throughout the simulation space. By comparing matched pairs of simulations, which varied in pulse size, duration, and intensity, we can gauge the impact plasma dynamics has upon the evolution of a filamenting laser pulse. From these tests we determine that, while there are some visible differences between dynamic
and static plasmas, plasma dynamics do not significantly alter the evolution of the pulse.
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Qiu, Jin 1974. "Modeling of plate impact dynamics and noise." Thesis, Massachusetts Institute of Technology, 1999. http://hdl.handle.net/1721.1/80514.
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Feroz, Kottamal Thanduparakal. "Impact dynamics of rods, beams and panels." Thesis, University of Manchester, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.488081.
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A methodology to study the impact dynamics of rods, beams and panels using modern numerical solution technique and instrumentation is developed. The numerical study is carried out using the commercial finite element package ABAQUS. The general approach of this tool is illustrated and verified for the static analysis of the stress distribution in a castellated beam and for the dynamic analysis of a cantilevered beam subjected to multiple impact loading. The finite element analysis technique is used to assess the optimal performance of steel plate panels of different cross-sections and thicknesses under the same blast loading conditions. Also, the structural response of folded plate panels of different cross-sections and thicknesses subjected to various blast pressures is studied numerically and compared with the existing experimental measurements. It is shown that the strength to weight ratio of the folded plate panels is higher than those of the single and double plate panels and that the folded plate panel is the more blast-resistant design. Stress wave propagation in circular mild steel rods is studied both numerically and experimentally. The rods are impacted longitudinally using spherical balls. The Hertzian law of impact and the associated non-linear ordinary differential equation of motion are used to determine the force-time history of impact. This force-time history is used in a finite element analysis of the rods to predict the propagation of pulses in the rods. The use of finite element simulation in predicting the wave propagation phenomena and its application to non-destructive testing (NDT) of rods and bars is demonstrated. For the experimental measurements, the stress waves propagated in rods and bars are monitored using PZT patches of size 5x3 mm which are calibrated by means of a finite element approach and by the use of a standard wire-resistance strain gauge. A time domain, frequency domain, regression analysis and autocorrelation procedures are developed to detect defects in rods and bars using wave propagation data. The defects are introduced in the form of slots. By analysing the stress wave data for the defect-free rods and bars and for the rods and bars with defects, it is possible to pinpoint the location of the defects. The results show that defects can be identified using any of the procedures and that their location can be estimated using the time domain technique. It is also shown that a high degree of correlation is obtained between measured and predicted characteristics.
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Sharker, Saberul Islam. "Water Entry Impact Dynamics of Diving Birds." DigitalCommons@USU, 2017. https://digitalcommons.usu.edu/etd/6441.
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Some seabirds (such as Northern Gannets and Brown Boobies) can dive from heights as high as 30 m reaching speeds of up to 24 m/s as they impact the water surface. It is perceived that physical geometry, particularly of the beak, allows them to endure relatively high impact forces that could otherwise kill non-diving birds. Acceleration data from simplified models of diving birds agree with simulated data for one species (Northern Gannet), however, no reliable experimental data with real bird geometries exist for comparison purposes. This study utilizes eleven 3D printed diving birds (five plunge-diving, five surface-diving and one dipper) with embedded accelerometers to measure water-entry impact accelerations for impact velocities ranging between 4.4 - 23.2 m/s. Impact forces for all bird types are found to be comparable under similar impact conditions and well within the safe zone characterized by neck strength as found in recent studies. However, the time each bird requires to reach maximum impact acceleration and its effect represented here by the derivative of acceleration (i.e., jerk), is different based on its beak and head shape. We show that surface diving birds cannot dive at high speeds as the non-dimensional jerk experienced exceeds a safe limit estimated from human impact analysis, whereas those by plunge divers do not.
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BARDINI, LAURA. "Impact of hyporheic zones on nutrient dynamics." Doctoral thesis, Politecnico di Torino, 2013. http://hdl.handle.net/11583/2507376.
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Riverine sediments play a fundamental role within the fluvial system, since they represent potential removal zones of stream-borne pollutants and, in particular, nutrients derived by anthropogenic activities. The region of sediments where the exchange and mixing of surface and subsurface waters occurs is the hyporheic zone. This region is also a place of intense biogeochemical activity, influencing both the flora and the fauna living in the fluvial environment. In the last decades several works were focused either on the water exchanges or the biochemical reactions in the hyporheic zone but just few considered the interactions of both hydraulic and biochemical processes. In this thesis the reactive transport of oxygen and the most common water-borne nutrients (i.e., dissolved organic carbon, nitrate and ammonium) in a duned streambed is investigated. In particular, a numerical model is employed to simulate the flow field, the biogeochemical reactions and the solute spatial distribution in the hyporheic zone. Sensitivity analyses are also performed to study the influence of different hydrological and chemical properties of the system on the net solute fluxes across the streambed. Finally, the effect of sediment heterogeneity on substance reaction rates and, specifically, on nitrate source/sink role played by the sediments is also analyzed for a rippled streambed.
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Wheeler, Jeffrey M. "Nanoindentation under dynamic conditions." Thesis, University of Cambridge, 2009. https://www.repository.cam.ac.uk/handle/1810/218320.
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Nanoindentation has emerged as a leading technique for the investigation of mechanical properties on small volumes of material. Extensive progress has been made in the last 20 years in refining the nstrumentation of nanoindentation systems and in analysis of the resulting data. Recent development has enabled investigation of materials under several dynamic conditions. The palladium-hydrogen system has a large miscibility gap, where the palladium lattice rapidly expands to form a hydrogen-rich β phase upon hydrogenation. Nanoindentation was used to investigate the mechanical effects of these transformations on foils of palladium. Study of palladium foils, which had been cycled through hydrogenation and dehydrogenation, allowed the extent of the transformed region to be determined. Unstable palladium foils, which had been hydrogenated and were subject to dynamic hydrogen loss, displayed significant hardening in the regions which were not expected to have transformed. The reason for this remains unclear. Impact indentation, where the indenter encounters the sample at relatively high speeds, can be used to probe the strain rate dependence of materials. By combining impact indentation and elevated temperature indentation, the strain rate dependence of the superelasticity of nickel-titanium was probed over a range of temperatures. Similar trends in elastic energy ratios with temperature were observed with the largest elastic proportions occurring at the Austenite finish transformation temperature. Multiple impact and scratch indentation are two modes of indentation which are thought to approximate erosive and abrasive wear mechanisms, respectively. These were utilised to investigate the wear resistance of several novel coatings formed by plasma electrolytic oxidation (PEO) of Ti-6Al4-V. Multiple impact indentation results appear to subjectively rank the erosive wear performance of both ductile and brittle materials. Comparison of normalised performance of coating systems on aluminium in abrasive wear to scratch hardness showed similar degrees of resistance.
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Eriksson, Johan. "Experimental and numerical studies of nonsmooth mechanical systems : applications of dimension estimation." Licentiate thesis, Stockholm, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-288.
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Sim, Min Kyu. "Empirical findings in asset price dynamics revealed by quantitative modelling." Diss., Georgia Institute of Technology, 2014. http://hdl.handle.net/1853/54302.
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This dissertation addresses the fundamental question of what factors drive equity prices and investigates the mechanisms through which the drivers influence the price dynamics. The studies are based on the two different frequency levels of financial data. The first part aims to identify what systematic risk factors affect the expected return of stocks based on historical data with frequency being daily or monthly. The second part aims to explain how the hidden supply-demand of a stock affects the stock price dynamics based on market data observed at frequency levels generally between a millisecond and a second. With more and more financial market data becoming available, it greatly facilitates quantitative approaches for analyzing asset price dynamics and market microstructure problems.
In the first part, we propose an econometric measure, terms as modularity, for characterizing the cluster structure in a universe of stocks. A high level of modularity implies that the cluster structure of the universe of stocks is highly evident, and low modularity implies a blurred cluster structure. The modularity measure is shown to be related to the cycle of the economy. In addition, individual stock's sensitivity to the modularity measure is shown to be related to its expected return. From 1992 to 2011, the average annual return of stocks with the lowest sensitivity exceeds that of the stocks with highest sensitivities by approximately 7.6%. Considerations of modularity as an asset pricing factor expand the investment opportunity set to passive investors.
In the second part, we analyze the effect of hidden demands/supplies in equity trading market on the stock price dynamics. We propose a statistical estimation model for average hidden liquidity based on the limit orderbook data. Not only the estimated hidden liquidity explains the probabilistic property in market microstructure better, it also refines the existing price impact model and achieves higher explanation powers. Our enhanced price impact model offers a base for devising optimal order execution strategies. After we develop an optimal execution strategy based on the price impact function, the advantage of this strategy over benchmark strategies is tested on a simulated stock trading model calibrated by historical data. Simulation tests indicate that our strategy yields significant savings in transaction cost over the benchmark strategies.
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Moore, Matthew Richard. "New mathematical models for splash dynamics." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:c94ff7f2-296a-4f13-b04b-e9696eda9047.
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In this thesis, we derive, extend and generalise various aspects of impact theory and splash dynamics. Our methods throughout will involve isolating small parameters in our models, which we can utilise using the language of matched asymptotics. In Chapter 1 we briefly motivate the field of impact theory and outline the structure of the thesis. In Chapter 2, we give a detailed review of classical small-deadrise water entry, Wagner theory, in both two and three dimensions, highlighting the key results that we will use in our extensions of the theory. We study oblique water entry in Chapter 3, in which we use a novel transformation to relate an oblique impact with its normal-impact counterpart. This allows us to derive a wide range of solutions to both two- and three-dimensional oblique impacts, as well as discuss the limitations and breakdown of Wagner theory. We return to vertical water-entry in Chapter 4, but introduce the air layer trapped between the impacting body and the liquid it is entering. We extend the classical theory to include this air layer and in the limit in which the density ratio between the air and liquid is sufficiently small, we derive the first-order correction to the Wagner solution due to the presence of the surrounding air. The model is presented in both two dimensions and axisymmetric geometries. In Chapter 5 we move away from Wagner theory and systematically derive a series of splash jet models in order to find possible mechanisms for phenomena seen in droplet impact and droplet spreading experiments. Our canonical model is a thin jet of liquid shot over a substrate with a thin air layer trapped between the jet and the substrate. We consider a variety of parameter regimes and investigate the stability of the jet in each regime. We then use this model as part of a growing-jet problem, in which we attempt to include effects due to the jet tip. In the final chapter we summarise the main results of the thesis and outline directions for future work.
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Movahedi-Lankarani, Hamid. "Canonical equations of motion and estimation of parameters in the analysis of impact problems." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184490.
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The transient dynamic analysis of constrained mechanical systems may require the solution of a mixed set of algebraic and differential equations of motion. The usual formulation of these equations is expressed in terms of the accelerations of the system components. A canonical form of the equations of motion in terms of the system velocities and the time derivative of the system momenta may be used instead. This is a natural form of the equations in which all the state variables are explicitly expressed, and have the same physical importance. The numerical solution obtained from the canonical equations shows more accuracy and stability, specifically for systems with large and fluctuating forces. For the mechanical systems that undergo an impact, the usual numerical solution of the equations of motion is not valid. Two different methods of analysis of impact problems are presented. In one method, the variations of the impulsive force during the contact period are directly added to the vector of forces in the canonical equations of motion. In the second method, based on the assumption of instantaneous nature of impact, a set of momentum balance-impulse equations is derived by explicitly integrating the canonical equations. These equations are solved at the time of impact for the jump in the system momenta right after impact. Necessary parameters are evaluated for the performance of the two methods of analysis. These parameters include the maximum relative indentation, the maximum contact force, and the coefficient of restitution. The parameters are determined for the collision between two bodies in a system with any general geometric or material properties. The influence of friction modeling in the magnitude and the direction of the total force at the contact surfaces is discussed. The dynamics of a vehicle collision is studied in order to illustrate the efficiency of obtaining a solution to the canonical equations, the simplicity of solving the momentum balance-impulse equations.
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Malik, M. A. A. "Limit order book dynamics and market impact estimation." Thesis, University of Essex, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.571506.
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This thesis focuses on two closely related areas of liquidity and market impact. The historic limit order book of Stock Exchange Trading Sys- tem (SETS) operated by the London Stock Exchange (LSE) is rebuilt using this framework for empirical analysis of information contained in the limit order book. The concept of Notional Volume Weighted Average Price (NVWAP) is introduced to construct liquidity supply and demand curves based on real time bid and ask schedules of the full length of the limit or- der book. This unique approach is used to determine how the order book behaves and I find consistent wave-like patterns between up- ward and downward price trends. Regression coefficients of the slope of the curves for each market event are estimated using an exponen- tial model. Four statistics are defined to identify bullish and bearish trends without prior knowledge of the market price. Detailed analy- sis shows that these statistics correctly identify market conditions for 88% to 97% of the observations. The intraday patterns of regression coefficients are revealed using a nonparametric kernel regression model. These intraday patterns are not found to be consistent between stocks over time. A resampled and deseasonalised set of estimated regression coefficients is analysed for temporal dependence using a multivariate vector autoregression (VAR) model. Inferences drawn from marginal probabilities regarding Cranger-causality do not show significant impact of slope coefficients on the opposite side of the limit order book implying that each side of the market is simultaneously rather than sequentially influenced by prevailing market conditions. The VWAP concept is extended to estimate the average shape of the limit order book and average market impact. The average market impact estimates are found to be superior than the order imbalance based approach. A time-of-day market impact for a given aggregate volume is estimated using a multivariate kernel regression model with monotonicity constraint. The estimated market impact shows stock- specific and wave-like impact that is asymmetric for buyers and sellers.
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Potter, Andrew Thomas. "The impact of supply chain dynamics on transport." Thesis, Cardiff University, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.440759.
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Skeppström, Lehto Hugo, and Richard Hedlund. "Impact of Vehicle Dynamics Modelling on Feature Based SLAM for Autonomous Racing." Thesis, KTH, Skolan för industriell teknik och management (ITM), 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-262646.
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In autonomous racing there is a need to accurately localize the vehicle while simultaneously creating a map of the track. This information can be delivered to planning and control layers in order to achieve fully autonomous racing. The kinematic model is a commonly used motion model in feature-based SLAM. However, it is a poor representation of the vehicle when considering high lateral accelerations since the model is only based on trigonometric relationships. This Master’s Thesis investigates the consequence of using the kinematic model when undertaking demanding maneuvers; and if by switching to a dynamic model, which takes the tire forces into account, can improve the localization performance. An EKF-SLAM algorithm comprising the kinematic and dynamic model was implemented on a development platform. The pose estimation accuracy was compared using either model when subject to typical maneuvers in racing-scenarios. The results showed that the pose estimation accuracy was in general similar when using either of the vehicle models. When exposed to large slip angles, the implications of switching from a kinematic model to a dynamic model resulted in a significantly better pose estimation accuracy when driving in an unknown environment. However, switching to a dynamic model had little effect when driving in a known environment. The implications of the study suggest that, during the first lap of a racing track, the kinematic model should be switched to a dynamic model when subject to high lateral accelerations. For the consecutive laps, the choice of vehicle model has less impact. Keywords: SLAM, EKF-SLAM, Localization, Estimation, Vehicle Dynamics, Kinematic Model, Dynamic Model, Autonomous RacingI autonom racing är det viktigt att kunna lokalisera fordonet med hög noggrannhet samtidigt som en karta över banan skapas. Den här informationen kan vidare bli hanterad av planerings- och reglersystem för att uppfylla autonom racing fullt ut. Den kinematiska modellen är en vanligt förekommande rörelsemodell i SLAM. Den är däremot en bristande representation av fordonet vid höga laterala accelerationer eftersom modellen enbart är baserad på trigonometriska samband. Det här masterarbetet undersöker den kinematiska modellens påverkan vid olika manövrar och huruvida den dynamiska modellen, som modellerar däckkrafterna, kan förbättra prestandan. En EKF-SLAM algorithm innehållande den kinematiska- och dynamiska modellen implementerades på en utvecklingsplattform. Estimeringsnoggrannheten av positionen och orienteringen jämfördes vid typiska manövrar för racingscenarier. Resultatet visade att estimeringsnoggrannheten av positionen och orienteringen var generellt sett lika vid användandet av antingen den kinematiska eller den dynamiska modellen. Implikationerna av att byta från den kinematiska modellen till den dynamiska modellen vid höga glidvinklar, resulterade i en signifikant bättre estimeringsnoggrannhet av positionen och orienteringen vid körning i en okänd miljö. Emellertid så var effekterna av att byta till en dynamisk modell insignifikanta vid körning i en känd miljö. Implikationerna av denna studie föreslår att under det första varvet av racingbanan byta från den kinematiska modellen till den dynamiska vid höga laterala accelerationer. Under kommande varv har valet av fordonsmodell mindre effekt. Nyckelord: SLAM, EKF-SLAM, lokalisering, estimering, fordonsmodellering, kinematisk modell, dynamisk modell, autonom racing.
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Jafri, Syed M. "Modeling of impact dynamics of tennis ball with a flat surface." Thesis, Texas A&M University, 2003. http://hdl.handle.net/1969.1/2441.
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A two-mass model with a spring and a damper in the vertical direction, accounting for vertical translational motion and a torsional spring and a damper connecting the rotational motion of two masses is used to simulate the dynamics of a tennis ball as it comes into contact with a flat surface. The model is supposed to behave as a rigid body in the horizontal direction. The model is used to predict contact of the ball with the ground and applies from start of contact to end of contact. The springs and dampers for both the vertical and the rotational direction are linear. Differential equations of motion for the two-mass system are formulated in a plane. Two scenarios of contact are considered: Slip and no-slip. In the slip case, Coulomb??s law relates the tangential contact force acting on the outer mass with the normal contact force, whereas in the no-slip case, a kinematic constraint relates the horizontal coordinate of the center of mass of the system with the rotational coordinate of the outer mass. Incorporating these constraints in the differential equations of motion and applying initial conditions, the equations are solved for kinematics and kinetics of these two different scenarios by application of the methods for the solutions of second-order linear differential equations. Experimental data for incidence and rebound kinematics of the tennis ball with incidence zero spin, topspin and backspin is available. The incidence angles in the data range from 17 degrees up to 70 degrees. Simulations using the developed equations are performed and for some specific ratios of inner and outer mass and mass moments of inertia, along with the spring-damper coefficients, theoretical predictions for the kinematics of rebound agree well with the experimental data. In many cases of incidence, the simulations predict transition from sliding to rolling during the contact, which is in accordance with the results obtained from available experimental measurements conducted on tennis balls. Thus the two-mass model provides a satisfactory approximation of the tennis ball dynamics during contact.
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Li, Kuinian. "Impact dampers for structural dynamic control." Thesis, University of Bath, 2004. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.409881.
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Zhu, Ling. "Dynamic inelastic behaviour of ship plates in collision." Thesis, University of Glasgow, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324960.
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Gebhardt, Christoph R. "Reactive cluster impact dynamics and ion processes investigated by cluster impact mass spectrometry." [S.l. : s.n.], 2000. http://deposit.ddb.de/cgi-bin/dokserv?idn=962138657.
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Cox, Simon John. "Pressure impulses caused by wave impact." Thesis, University of East Anglia, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266731.
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Ariyo, Adeyemi Idowu. "Droplet Dynamics of Aqueous Polymeric Solutions on Solid Surfaces." University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1236212747.
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Modarres, Najafabadi Seyed Ali. "Dynamics modelling and analysis of impact in multibody systems." Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=115886.
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In this thesis, we discuss a novel approach to the dynamics modelling and analysis of impact in unilaterally constrained multibody systems. This approach is based on an analysis of energy absorption and restitution during impact, using a decomposition technique, which decouples the kinetic energy associated with the spaces of admissible and constrained motions of unilateral contacts. This is done based on the decomposition of the tangent space of the configuration manifold at the pre-impact instant. The decomposition of the kinetic energy can provide a picture of how the energy absorption and dissipation during impact is related to the variation of the generalized velocities and the configuration of multibody systems.Further, based on the above analysis approach, we introduce a new interpretation of the energetic coefficient of restitution, specially applicable to contact involving multibody systems. This interpretation generalizes the concept of the energetic coefficient of restitution and allows for consideration of simultaneous multiple-point contact scenarios. Moreover, based on the concept of the generalized energetic coefficient of restitution, the contact modes and the post-impact state of planar single-point impact are determined. Further, the problem of simultaneous multiple-point impact is considered, where it is shown that our approach can also be advantageous to characterize the dynamics of interaction in such systems.
The use and applicability of the approach reported are further investigated by conducting an experimental study on a robotic testbed. The open architecture of the testbed allows us to perform various contact experiments, such as single- and multiple-point impact scenarios, with different pre-impact configurations and velocities. The kinematic and dynamic models of the system have been developed and implemented for real-time analysis. It is shown that impact between multibody systems is considerably affected by not only the local dynamics characteristics of the interacting bodies, but also the (global) configuration of the interacting multibody systems. The reported results suggest that the material presented herein offers a useful means to characterize impact in complex systems.
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Ghazavi, M. R. "Pin dynamics and impact in revolute joints with clearance." Thesis, University of Bath, 1990. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.760604.
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Kamarainen, Outi Katriina. "Dynamics of ligand-protein interactions : impact on drug discovery." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/18445/.
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Introducing a new drug to market is a lengthy and expensive process (typically 10-15 years and $1.7 billion). Better understanding of how and why a drug molecule binds to a target and what changes in the atomistic structure and chemistry could improve the binding affinity and shorten the process. In addition to structure-based approaches, the role of thermodynamics and molecular motions in binding selectivity and efficiency have attracted increasing attention. Whilst calorimetric methods can quantify total free energy and entropy change, it is difficult to estimate contributions from the different components of entropy, one of the largest unknowns being the magnitude of the configurational entropy. Molecular dynamics (MD) simulations of the drug and target protein can provide more details of the different atomistic movements contributing to the total entropy change, thus potentially providing valuable clues for lead optimisation. In this study we use the well characterised N-terminal domain of the Hsp90 chaperone protein as a model system to study the changes in conformational flexibility (configurational entropy) upon binding of small molecule inhibitors using MD simulations, NMR and ITC. We show that the two inhibitors studied cause different changes in the protein dynamics. These effects were seen with NMR relaxation dispersion methods and with MD but the dynamic changes however are not reflected in the global ITC parameters. Here the water is assumed to have a dominating effect in the overall entropy change. However, as some Hsp90 clients have been shown to preferentially interact with only one conformation of the protein, we propose that the changes seen with NMR and MD could be of interest for drug design. Manipulating the dynamics by small molecules could favour interaction with a subset of client proteins, without affecting the interaction of others, all together providing specificity and potentially allowing to design an ‘ideal’ drug that only prevents the folding of ‘bad’ cancer related proteins without affecting Hsp90 functions in the normal cells. As the MD simulations also reflect these dynamic changes, we propose that simulations could be also used as a screening tool for selecting which inhibitors could be taken for further development in the lab.
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Yang, Yongqian. "Impact of Patchy Vegetation on Wave and Runup Dynamics." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/72278.
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Coastal regions are vulnerable to various natural processes, ranging from normal waves to extreme events. Given the flourishing development and large population along coastlines, various measures have been taken to mitigate the water-induced damage. Nature-based coastal protection, especially vegetation, has attracted unprecedented studies over the past two decades. To enhance understanding of this subject, this dissertation evaluates the impact of patchy vegetation on wave and runup dynamics along coastlines. Selecting from a prototype in Dalehite Cove, Galveston Bay, TX, results from a Boussinesq model (COULWAVE) showed patchy vegetation reduced up to 75% mean shoreward current in the mound-channel wetland systems. These vegetation patches also reduced the primary circulation around mounds, with a power-form relation between circulation size and various parameters (i.e., bathymetry, incident wave and vegetated roughness). Substituting spectral waves for regular waves in the similar wetlands, more energy was transferred into the higher frequencies. The impact of patchy vegetation on wave energy was frequency- and space-dependent, with increased energy observed in specific harmonics and locations. Comparison with unvegetated horizontal bathymetry demonstrated that mound-channel bathymetry was the dominant factor in transferring and dissipating wave energy, while vegetation patches added a fair contribution. As for extreme events, such as tsunamis, laboratory experiments and numerical simulations were conducted to assess the effectiveness of patchy vegetation with various roughness levels, spacings and sizes. Overall, vegetation patches reduced the most destructive loads onshore by up to 80%. Within-patch roughness variation only caused uncertainty on the hydrodynamics around the seaward patches, while the mitigation of extreme loads was not undermined. A logarithmic relation was observed between the protected area from extreme loads and the vegetated coverage. These findings will fill the knowledge gap of hydrodynamics in the presence patchy vegetation, and improve the engineering practice of coastal protection using nature-based infrastructure.Ph. D.
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GATNE, KALPAK PRAKASH. "EXPERIMENTAL INVESTIGATION OF DROPLET IMPACT DYNAMICS ON SOLID SURFACES." University of Cincinnati / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1163531264.
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Lee, Gordon. "The theoretical and numerical analysis of impact oscillators." Thesis, University of Bristol, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.336875.
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Zhu, Bin. "p-Version finite elements and applications in structural impact and damage detection /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-bc-b19887565a.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2005."Submitted to Department of Building and Construction in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references (leaves 253-269)
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Maak, Travis Gardner. "Dynamic Intervertebral Foramen Narrowing During Whiplash." Yale University, 2006. http://ymtdl.med.yale.edu/theses/available/etd-06282006-113354/.
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A biomechanical study of intervertebral foraminal narrowing during simulated automotive head-forward and head-turned rear impacts. The objective of this study was to quantify foraminal width, height and area narrowing during head-forward and head-turned rear impacts, and evaluate the potential for nerve root and ganglion impingement. Muscle weakness and paresthesias, documented in whiplash patients, have been associated with neural compression within the cervical intervertebral foramen. Rotated head posture at the time of rear impact has been correlated with increased frequency and severity of chronic radicular symptoms, as compared to facing forward. No studies have quantified dynamic changes in foramen dimensions during head-forward or head-turned rear impacts. Six whole cervical spine specimens with muscle force replication and surrogate head underwent simulated whiplash at 3.5, 5, 6.5 and 8 g, following non-injurious baseline 2 g acceleration. Continuous dynamic foraminal width, height and area narrowing were recorded, and the peaks were determined during each impact and statistically compared to baseline narrowing. During head-forward rear impacts, significant increases (P<0.05) in average peak foraminal width narrowing above baseline were observed at C5-C6 beginning with 3.5 g impact. No significant increases in average peak foraminal height narrowing were observed, while average peak foraminal areas were significantly narrower than baseline at C4-C5 at 3.5, 5 and 6.5 g. During head-turned rear impacts, significant increases (P<0.05) in average peak foraminal width narrowing above baseline of up to 1.8 mm in the left C5-C6 foramen at 8 g were observed. Average peak dynamic foraminal height was significantly narrower than baseline at right C2-C3 foramen at 5 g and 6.5 g, while no significant increases in foraminal area were observed. Extrapolation of the present head-forward rear impact results indicated that the greatest potential for ganglia compression injury was at the lower cervical spine, C5-C6 and C6-C7. The present head-turned rear impact results indicated that the greatest potential ganglia compression injury exists at C5-C6 and C6-C7. Greater potential for ganglia compression injury exists at C3-C4 and C4-C5 due to head-turned rear impact, as compared to head-forward rear impact. Acute ganglia compression may produce a sensitized neural response to repeat compression leading to chronic radiculopathy following head-forward and head-turned rear impacts. Dynamic ganglion or nerve root compression may also lead to chronic radiculopathy.
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Lee, Eunjeong. "Force and impact control for robot manipulators with unknown dynamics and disturbances." Case Western Reserve University School of Graduate Studies / OhioLINK, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=case1057933316.
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Djahansouzi, B. "Effect of dynamic response on impact damage." Thesis, Imperial College London, 1988. http://hdl.handle.net/10044/1/47033.
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Saleh, Almahdi. "Assessment of Nonlinear Damping Elements for Vibro-Impacts inAutomotive Torsional Systems with Discontinuous Nonlinearities." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1449148151.
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Šafr, Karel. "Analýza dopadů regulací pomocí dynamického input-output modelu." Master's thesis, Vysoká škola ekonomická v Praze, 2013. http://www.nusl.cz/ntk/nusl-194207.
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This diploma thesis discusses utilization of dynamic Input-Output models as a basis for decision-making for policy makers. The first part is focused on theoretical derivation of the basic dynamic models. This part is followed by a practical application of the presented models, which proposes a method of deriving the matrix of capital and it facilitates the construction of data sources. The results show that the dynamic models are usable, but it is necessary to take into consideration their structural constraints and data limits. Data applied for 2009 show that the economic crisis has led to a 6% decline in GVA growth rates.
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Rupčík, Jan. "Deformační člen formulového vozidla." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2015. http://www.nusl.cz/ntk/nusl-231790.
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The diploma thesis deals with Formula Student Impact Attenuator design of TU Brno Racing team. The aim of the thesis is the design, the dynamic tests and the production of Impact Attenuator of racing formulas called Dragon 4 and Dragon 5, so to meet the Formula Student rules. The thesis deals further with FEM dynamic analysis of Impact Attenuator.
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Kennedy, Eric Allen. "Lateral and Posterior Dynamic Bending of the Mid-Shaft Femur: Fracture Risk Curves for the Adult Population." Thesis, Virginia Tech, 2004. http://hdl.handle.net/10919/32216.
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The purpose of this study was to develop injury risk functions for dynamic bending of the human femur in the lateral-to-medial and posterior-to-anterior loading directions. A total of 45 experiments were performed on human cadaver femurs using a dynamic three-point drop test setup. All 45 tests resulted in mid-shaft femur fractures with comminuted wedge and oblique fractures as the most common fracture patterns. The reaction loads were used to develop the injury criteria given that they represent the inertially compensated bending strength of the femur that is more appropriate for dummy load cell application. In the lateral-to-medial bending tests the peak reaction bending moments were 352 ± 83 Nm. In the posterior-to-anterior bending tests the peak reaction bending moments were 348 ± 96 Nm. Regression analysis was used to identify significant parameters, and parametric survival analysis was used to estimate risk functions. Femur cross-sectional area, area moment of inertia (I), maximum distance to the neutral axis (c), I/c, occupant gender, and occupant mass are shown to be significant predictors of fracture tolerance, while no significant difference is shown for loading direction, bone mineral density, leg aspect and age. Risk functions are presented for femur cross-sectional area, I/c, and a combined occupant gender and mass. The risk function that utilizes the most highly correlated (R2 = 0.77) and significant (p = 0.0001) variable, cross-sectional area, predicts a 50 percent risk of femur fracture of 240 Nm, 395 Nm, and 562 Nm for equivalent cross-sectional area of the 5th percentile female, 50th percentile male, and 95th percentile male respectively.Master of Science
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DOMMATA, SANDEEP KUMAR GOUD, and SAMARA CHANDRA HASON KONAGALA. "IMPACT OF GROUP DYNAMICS ON TEAMS WORKING IN SOFTWARE ENGINEERING." Thesis, Blekinge Tekniska Högskola, Institutionen för programvaruteknik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-4696.
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Context: Group dynamics play an important role in software projects. All of the existing software engineering methodologies (like Rational Unified Process, Microsoft Solutions Framework, Agile, etc.) use the concept of the teamwork and emphasize the necessity to manage them in order to organize the business processes in the best way. The application of group dynamic techniques is aimed at improvement of teamwork management to make it more efficient. The implementation of group dynamic techniques has an impact on teams working in software engineering and it also faces some challenges for industry such as lack of resources and preparation. Both need additional investigation which regard to the actual practiced situation in industry. Objectives: The given work is devoted to identification of group dynamics techniques and their impact on teams in the context of industrial software development projects. The objectives of the research is to identify the existing and in an industrial context, actually used group dynamics techniques in software engineering as well as their impact and methods of its evaluation. Since the application of group dynamics techniques is not a trivial task, we also identify those challenges and corresponding mitigation strategies. Methods: The basic methods applied during the research conduction are systematic literature review and survey. Literature review was used in order to collect the data on group dynamics techniques, their impact and implementation challenges. The survey and additional interviews with the practitioners from the software development companies were done with the purpose to find out which of the techniques are applied in practice. Results: Based on the data from systematic literature review we identified group dynamics techniques such as equalizing participation, electronic communication, conflict resolution, summarizing, whole and small group discussions, brainstorming, etc. The discovered impacts include team performance and cohesiveness, staff satisfaction and communication quality, software quality, reasonable decision-making and knowledge sharing. The possible challenges of group dynamics techniques implementation are company’s limited resources, lack of leadership and preparation, over-dominating of some team members and cultural diversity. The survey provided us with additional information about the importance of mentioned group dynamics techniques and their impact on team performance and cohesiveness, job satisfaction and software quality. Conclusions: We conclude that group dynamics techniques in software development projects influence the performance and cohesiveness of the teamwork as well as the quality of the software solutions and products. The possible challenges can be overcome by promotion of open communication and trust among team members, and additional psychological preparation and training of facilitator. The research discovered a slight difference in the literature review and survey results. In particular we found out that, some group dynamics techniques are overestimated in literature, while the others are undervalued. Also the survey results helped to identify the techniques such as small group discussion, conflict resolution and many more were used by the teams of definite size, which was not possible to discover in the SLR for example large teams pay much attention to feedback and electronic communication The obtained results can be used by software engineering practitioners in order to organize and rearrange their teamwork, which can positively affect team performance and project success.SANDEEP KUMAR GOUD DOMMATA: +91-9848783435
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Stoenescu, Eleonor D. Marghitu Dan B. "Dynamics and synthesis of kinematic chains with impact and clearance." Auburn, Ala., 2005. http://repo.lib.auburn.edu/EtdRoot/2005/SPRING/Mechanical_Engineering/Dissertation/STOENESCU_ELEONOR_32.pdf.
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Ward, Zoe. "Exploring the impact of heterogeneities on HIV dynamics within host." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.550615.
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This thesis is concerned with exploring how cell heterogeneity and drug resistance can cause long term persistence of HIV. We examine models of multiple viral strains to assess the impact of drug resistance on viral persistence and extend our cell heterogeneity models to include multiple strains. Chapter 1 summarises the nature of HIV infection within host. The key barriers to HIV eradication within host and the role of mathematical models to help understand these issues are discussed. In Chapter 2 we analyse models that include cell heterogeneity. We find robust long term viral persistence is possible on therapy and differences in viral load between body compartments explained by cell heterogeneity. The inclusion of a drug sanctuary also allows low level viral load on treatment. Competition and evolutionary models of wildtype and drug resistant strains of virus are described in Chapter 3. We analyse two models containing three strains of virus with different mutation mechanisms. We find that the proportion of the minority strains of virus is determined by the number of mutations away from the dominant strain. In Chapter 4 we extend our cell heterogeneity models from Chapter 2 to include a drug resistant strain of virus. We find that when a drug sanctuary is present coexistence is possible in the absence of an evolutionary mechanism. The two compartment model also shows differential dominance whereby a different strain is dominant in each compartment. within the host. We find the latent cell reservoir acts as an archive for previously dominant viral strains when there is a mechanism for latent cell maintenance and that the balance between ongoing viral and latent cell replication determines the longevity of the archive.
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Kundu, Reema. "Impact of engine icing on jet engine compressor flow dynamics." Diss., Georgia Institute of Technology, 2015. http://hdl.handle.net/1853/54870.
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Core engine icing has been recognized to affect a wide variety of engines since the 1990's. This previously unrecognized form of icing occurs in flights through high altitude convective regions and vicinity of thunderstorms. Engine icing events involve power loss or damage associated to the engine core, namely instabilities such as compressor surge, stall, engine rollback and even combustor flameout events.
The effects on compressor performance are significant in understanding the response of the engine to atmospheric ice ingestion. A one-dimensional axisymmetric flow model is used to simulate the continuous phase through the compressor. The steady state operation of dry air is validated with an industrial database. By changing an exit throttle, the point where the dry compressor mass flow rate slowly starts to drop, is predicted. The stage that is the first to locally collapse, causing the remaining stages and eventually the complete compressor failure, is determined. The continuous flow model is then coupled with a Lagrangian model for the discrete phase in a framework that conserves mass, momentum and energy. From numerical simulations of the coupled, continuous-discrete phase flow model, it is observed that a rematching of the stages across the compressor occurs with increasing ice flow rates to accommodate loss of energy to the ice flow. The migration of the operating point towards the stall point at the rear stage eventually causes the compressor to stall. The onset of stall is characterized by initial oscillations followed by a rapid decay of pressures of the last stage with the instability traveling quickly towards the front of the compressor. Effectively, a reduction in the compressor stall margin is observed as the ice flow rate increases.
Further, the relevance of factors such as blockage due to discrete particles and break/splash semi-empirical models in the icing physics, are analyzed through parametric studies.
Conclusions are drawn that underscore the influence of the assumptions and models in prediction of the flow behavior in the presence of ice ingestion. Smaller ice crystal diameters have a greater influence on the gas flow dynamics in terms of a higher reduction in surge margin. The break empirical model for ice crystals and splash model for the droplets that are used to calculate the secondary particle size upon impact with rotor blades have a significant influence on the gas flow predictions.
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Warner, Sharon Elaine. "Foot design, locomotor impact dynamics and pathology in large mammals." Thesis, Royal Veterinary College (University of London), 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.618328.
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Aoki, Takaaki. "Molecular Dynamics Simulation of Cluster Ion Impact on Solid Surface." Kyoto University, 2000. http://hdl.handle.net/2433/8942.
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学位授与年月日: 2000-03-23 ; 学位の種類: 新制・課程博士 ; 学位記番号: 1891In this thesis, the impact process of cluster ions on solid surfaces was studied using molecular dynamics (MD) simulation. Cluster is an aggregated material which consists of a few to thousand atoms. The impact process of cluster ion on solid surface is of great interest because the effect of impact by cluster ion cannot be explained by the summation of individual monomer ions, and it is termed as 'nonlinear effect.' In order to understand the nonlinear effect by cluster, the dynamics of collisional process between cluster and solid surface should be examined. MD simulation is one method of computer simulation to solve numerically the Newton's equation of motion for each atom in the system using difference equation technique, so MD can make it possible to trace the time evolution of coordinates and velocity for every atom with high resolution. The basic theory of molecular dynamics and the acceleration method are described in chapter 2. For this study, the original MD program was developed, which can accelerate the calculation speed of collisional process of high-energy atoms with a solid surface by applying different timestep to each atom depending on its velocity. Due to this acceleration technique and recent progress in computers, it can be possible to simulate the system with a large number of atoms, or more than hundred simulations in order to obtain statistics. In the following chapters, MD simulation is used to examine the impacts of various types of clusters on a number of well defined substrates. Chapter 3 describes the typical impact process of cluster on solid surface examined using large argon cluster and silicon substrate. The differences between cluster and monomer impact are shown in penetration range, damage formation and sputtering. The energy dependence of penetration depth of cluster was examined and it was fond that the penetration depth is proportional to the cube root of the incident energy. This is due to a large number of collisions between cluster atoms and surface atoms, which cause isotropic propagation of incident energy. Through this multiple-collision process, a crater-shaped damage is formed on the surface. In chapter 4, the impacts of carbon cluster onto carbon substrate are examined both by MD simulation and experimentally. Carbon is a suitable material to generate well-defined small size clusters such as C7 , C19 and C60 in experiments. It was found that the penetration depth of carbon clusters with several keV/atom is similar to that of monomer ion, but a larger number of displacements are formed with the cluster size of larger than 10. From this study, the boundary size of cluster size where a cluster shows the nonlinear effect is discussed. Shallow junction formation by boron cluster implantation into silicon substrate is discussed in chapter 5. Decaborane (B10H14) is a stable material of boron cluster and each boron atom can be irradiated with 1/10 energy of the total acceleration energy. This implies that the low-energy implantation can be obtained easily. The penetration depth by B10H14 is shown to be the same as that by boron monomer ions with same acceleration energy per atom. Furthermore, it is found that B10H14 implantation can form larger number of displacements in the near surface region, with lower atomic dose than monomer ions. The high-yield damage formation on the surface suggested to suppress the transient enhanced diffusion (TED). These properties of B10H14 implantation are considered as advantageous for small LSI fabrication. In chapter 6, the impact of uorine cluster and neon cluster onto silicon substrate are compared, in order to examine the sputtering effect by reactive cluster ion. Fluorine cluster shows higher sputtering yield than both uorine atom and neon cluster at low energy region. It is suggested that the high-density atomic and energy deposition by cluster ion impact prompt the formation of volatile silicon- uoride materials and desorption of uoride materials. As the incident energy increases, uorine and neon cluster shows similar sputtering yield because the physical sputtering effect through atomic collisions is major effect in high energy region. From these results, characteristics of cluster ion impact depending on incident energy, cluster size and cluster and substrate species are discussed.
Kyoto University (京都大学)
0048
新制・課程博士
博士(工学)
甲第8326号
工博第1891号
新制||工||1165(附属図書館)
UT51-2000-F230
京都大学大学院工学研究科電子物性工学専攻
(主査)教授 山田 公, 教授 今西 信嗣, 助教授 高岡 義寛
学位規則第4条第1項該当
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Clapham, Hannah Eleanor. "Modelling dengue infection dynamics and the impact of control measures." Thesis, Imperial College London, 2013. http://hdl.handle.net/10044/1/18022.
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Dengue is a vector-borne disease found across much of the world, with an increasing number of cases annually. This thesis explores the dynamics of dengue infection within an individual, and the possible impact of this at a population level. I use mathematical modelling and statistical analysis, tightly coupled with data, as a way of tying together the important components and processes during infection. I model the virus and immune dynamics, capturing the differences between individuals, disease severity and primary/secondary disease (with a focus on hypothesised secondary mechanisms). Within the immune dynamics I concentrate on antibody, looking at the role of antibody in limiting infection. Within this framework I also consider the impact on these dynamics of an antiviral. The final section of this thesis brings together this closer consideration of virus dynamics and considers their impact at a population level. Using data from biting experiments I am able to characterise the “infectivity” of an individual over time, how this varies between individuals and groups (as above), and how this compares to previous transmission modelling assumptions. In terms of control I look at how this “infectivity” is altered by antivirals and by wolbachia infected mosquitoes.
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Kaiser, Thomas. "Impact of Flow Rotation on Flame Dynamics and Hydrodynamic Stability." Thesis, Toulouse, INPT, 2019. http://oatao.univ-toulouse.fr/24115/1/Kaiser_Thomas.pdf.
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This thesis investigates large scale flow rotation in two configurations. In the first, the effect of flow rotation on a laminar flame is investigated. The flame is anchored in the wake of a cylindrical bluff body. The flow rotation is introduced by turning the cylinder along its axis. It is shown by Direct Numerical Simulation (DNS), that the cylinder rotation breaks the symmetry of both flame branches. Flame Transfer Function (FTF) measurements performed by the Wiener-Hopf Inversion suggest, that low rotation rates lead to deep gaps in the gain and the flame becomes almost insensitive to acoustic perturbation at a specific frequency. It furthermore is demonstrated that this decrease in gain of the FTF is due to destructive interference of the heat release signals caused by the two flame branches. The frequency at which the gain becomes almost zero can be adjusted by tuning the cylinder rotation rate. The study suggests that controlling the symmetry of the flame could be a tool of open-loop control of thermoacoustic instabilities.