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Mujahid, Aazani. "Vertical structure of propagating features." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/209541/.
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The inter- and intra-annual variability of the western boundary North Atlantic 26.5 ◦N region has been central in the observations of the strength and structure of the Atlantic Meridional Overturning Circulation (AMOC). Interest in this work began when some recent work estimated the inter-annual fluctuations of the AMOC at 26.5 ◦N to be up to 3 Sv, and with a 25% reduction in strength over the last 50 years. There was increased need to understand both the short and long-term changes in the region and the responsible mechanisms for its variability. With the unique use of RAPID-MOC and MOCHA transatlantic mooring array in combination with satellite altimetry and transatlantic hydrographic observations, we find evidence that a significant amount of the variability can be accounted for by various mechanisms on different time-space scales including propagating features. Here we present simultaneous assimilation of surface and sub-surface observations that shows fresh insights into the contribution of the propagating features in the vertical structure of the temporal-spatial evolution in the western boundary 26.5 ◦N Atlantic. There is great prospect in using altimetry observations to reflect and infer the variability throughout the water-column - an effort vital in future interpretations of the AMOC fluctuations using altimetry and numerical models.
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Christy, Clifford T. "Numerical modeling of a propagating crack." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA272604.
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Collier, Joanne Ruth. "Spatial and propagating patterns in embyrology." Thesis, University of Oxford, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389214.
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Adamson, Fiona. "Propagating reaction fronts in zirconia tubes." Thesis, University of Birmingham, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.487432.
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Patel, Samir N. D. H. "Modelling of premixed turbulent propagating flames." Thesis, Loughborough University, 2001. https://dspace.lboro.ac.uk/2134/6810.
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Combustion has an active role in our modern lives as we continue to exploit its potential for many of our requirements. For example, its use to produce electricity and to power land, air and space transport vehicles. Increasing competition from the onset of the Industrial Revolution has led to a greater emphasis on improving technology. Furthermore, the ongoing issue of global warming has led to government legislation on emissions. These problems have led to increasing interest in gaining fundamental critical details on flow and combustion in simple and complex engineering geometries. Over the past twenty to thirty years numerical methods have demonstrated their success at obtaining information on flow and combustion. However, there is a continuing need to develop many of the components comprising a numerical method. The work reported here stems from the modelling of turbulent premixed flames. Turbulent premixed flames is a mode of combustion where the fuel and air mix before reacting. Such a combustion mode is present in spark ignition (SI) and gas turbine (GT) engines, and in explosions. Modelling of the combustion process within these practical applications can provide useful information. For example, in aiding the design of the piston bowl and the combustion chamber of SI and GT engines, respectively. Furthermore, the simulation of explosions can result in safer designs for fuel storage and supply facilities. A central parameter to be modelled in turbulent premixed flame propagation is the rate of chemical reaction. This is a crucial parameter since it controls the rate of flame propagation, flame structure, and resulting pressure history. However, to date the challenge of accurately modelling the rate of chemical reaction over a range of turbulence conditions remains. Therefore, in this thesis, mathematical models for the mean rate of reaction are examined, developed, and validated against time-resolved experimental data. The aim of the work is to improve the modelling of the mean rate of reaction in order to achieve closer agreement with available experimental results on rates of flame propagation, flame structure, and pressure history. Recent, practical and numerical experiments have provided support for algebraic and transport equation models for the flame surface area to volume ratio to model the mean rate of reaction. Here, these models are examined and developed with one-, two-, and three-dimensional computational fluid dynamics (CFD) calculations. The simulations were carried out using both an in-house code (Turbulent Reacting Flows, TRF) and a commercially available CFD code (FIRE). The TRF code was used to investigate the ability of existing and developed models to accurately predict turbulent burning velocity. The models were then validated further by simulating turbulent flame propagation in two combustion chamber configurations with built-in solid obstacles. Hence verifying the models for different turbulence and geometry conditions. A nonlinear eddy-viscosity model was implemented into the TRF code to assess the significance of turbulence modelling in turbulent premixed flames. Finally, the developed models were implemented in the FIRE code to carry out three-dimensional calculations to verify reproducibility of the TRF code results and to investigate secondary flow effects. Two reaction rate models were developed namely the algebraic (BML) and transport flame surface density (FSD) models. Both BML and FSD models yield plausible results for flame propagation in turbulent premixed combustion. However, modifications to the BML model were required for low turbulence conditions, and superior results were obtained with the FSD model. Both models struggled in capturing the interaction between flame and turbulent wakes behind obstacles when the standard linear eddy-viscosity turbulence was used. However, the application of a non-linear version of the eddy-viscosity model yields improved results for flame structure and speed around the obstacle, highlighting the importance of the turbulence model. The 3D calculations using the developed combustion model show good reproducibility of the 2D findings. Furthermore, the flame propagation, pressure history, and flame speed results are found to be in plausible agreement with the experimental data. It is shown that secondary flow mainly has the effect of increasing the rate of flame propagation in the single obstacle combustion chamber, and that the influence of secondary flow is dominant in the turbulent wake behind the obstacles.
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Vilela, Proaño Pablo Martin. "Propagating reaction fronts in moving fluids." Doctoral thesis, Pontificia Universidad Católica del Perú, 2015. http://tesis.pucp.edu.pe/repositorio/handle/123456789/6345.
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La presente tesis tuvo como objetivo estudiar frentes de reacción modelados mediante la ecuación de Kuramoto-Sivashinsky sujetos a diferentes tipos de movimiento de fluido: flujo externo de Poiseuille, el cual es contrastado con el flujo de Couette, y flujo convectivo debido a la inestabilidad de Rayleigh-Taylor. En el primer caso, los frentes se propagan a favor o en contra de un flujo estacionario bidimensional entre dos placas paralelas que se conoce como flujo de Poiseuille. Para pequeñas distancias entre las placas, encontramos frentes estacionarios que pueden ser planos, simétricos o asimétricos, dependiendo de la separación de las placas y de la velocidad promedio del fluido externo. Adicionalmente, descubrimos que los frentes simétricos estables que se propagan en sentido opuesto al flujo simétrico externo se vuelven asimétricos al incrementar la rapidez del flujo externo. En el caso del flujo externo de Couette, el flujo es producido por el movimiento de dos placas paralelas en sentidos opuestos. Hallamos que la estabilidad y la forma de los frentes estacionarios dependen de la velocidad relativa entre las placas y de su separación. Estos parámetros desempeñan un papel importante, puesto que pueden convertir frentes inestables en estables. En el último caso, las inestabilidades en el frente producidas cuando un fluido más denso se encuentra encima de un fluido menos denso se conocen como inestabilidades de Rayleigh-Taylor y son causadas por la diferencia de densidades a través del frente bajo la acción de la gravedad. El frente describe la interfaz delgada que separa los fluidos de diferente densidad dentro de dos placas paralelas verticales; mientras que la convección causada por las fuerzas de flotación a través de la interfaz delgada determina el flujo debido a la inestabilidad de Rayleigh-Taylor. Para el estudio de los efectos del flujo externo sobre los frentes de reacción, primero obtuvimos los frentes y luego realizaremos un análisis de estabilidad lineal para determinar la estabilidad de los frentes bajo los tres tipos de movimiento del fluido. La forma de los frentes y sus respectivas regiones de estabilidad fueron contrastadas con los frentes en ausencia de flujo externo. Los resultados de la investigación fueron publicados en tres revistas internacionales arbitradas e indexadas: Physical Review E (2012), Chaos (2014), y European Physics Journal (2014). Adicionalmente, la tesis presenta resultados para frentes oscilantes y sus transiciones al caos debido a la interacción del frente de reacción con los flujos externos antes mencionados.Tesis
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Weidlich, Matthias, Jan Mendling, and Mathias Weske. "Propagating Changes between Aligned Process Models." Elsevier, 2012. http://epub.wu.ac.at/3497/1/JSS12%2Dchange.pdf.
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There is a wide variety of drivers for business process modelling initiatives, reaching from organisational redesign to the development of information systems. Consequently, a common business process is often captured in multiple models that overlap in content due to serving different purposes. Business process management aims at exible adaptation to changing business needs. Hence, changes of business processes occur frequently and have to be incorporated in the respective process models. Once a process model is changed, related process models have to be updated accordingly, despite the fact that those process models may only be loosely coupled. In this article, we introduce an approach that supports change propagation between related process models. Given a change in one process model, we leverage the behavioural
abstraction of behavioural profiles for corresponding activities in order to determine a change region in another model. Our approach is able to cope with changes in pairs of models that are not related by hierarchical refinement and show behavioural inconsistencies. We evaluate the applicability of our approach with two real-world process model collections. To this end, we either deduce change operations from different model revisions or rely on synthetic change operations.
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Morris, Harold Campbell. "Typogenetics : a logic of artificial propagating entities." Thesis, University of British Columbia, 1989. http://hdl.handle.net/2429/41447.
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This thesis deals with abstract models of propagation
(especially, self—replication). As some of these reflector
borrow from nature, a summary of biology's current
understanding of natural reproduction (mitosis) is provided
for background. However, the predominant concern is with
entities realized in uninterpreted symbolic systems, and
associated philosophical and design problems. Thus the
comparison that is made between artificial and natural modes
of propagation is intended primarily to enhance conception
of the former.
Automata constitute one type of formal model. With a
simple Turing Table the concept of a self-replicating string
is illustrated. The idea of a logical universe in which
propagating "virtual" entities emerge and interact is
explored with reference to cellular automata.
A formal system called Typogenetics provides the
centerpiece of this thesis. The system, first presented in an
incomplete form in Hofstadter (1979), is here fully
developed (augmented with a useful program for personal
computers). A Typogenetics string ("strand," in
analogy to a DNA strand) codes for operations that act to transform that very strand into descendant strands.
Typogenetics strands exhibited include, among others, a
pallindromc self-replicator coding for operations sufficient
to replicate itself; a "self-perpetuator" deforming and then
reforming itself through fully compensatory operations; and
an "infinitely fertile" strand bearing an infinitude of
unique descendants.
Meta-logical proofs establish certain general
propositions about the Typogenetics system, e.g. that for
every strand there is a mother strand. Redactio reasoning, of
potential general is ability beyond Typogenetics, shows how a
hypothetical strand can be ruled out by establishing the
incommensurability of its two identities qua packet of
operations and qua operand.
A Russellian—type paradoxical strand that has all and
only the non—self-replicating strands for offspring is
considered (is it a self—replicator?), spurring discussion of
the Theory of Types and Hofstadter's "strange loops."Arts, Faculty of
Philosophy, Department of
Graduate
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Hector, Andrew Lee. "Self propagating metathesis preparations of inorganic materials." Thesis, University College London (University of London), 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243565.
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Aldurayhim, Abdullah Mohammed. "Propagating waves in reaction cross-diffusion systems." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/31129.
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This research focuses on the reaction diffusion systems where the matrix of diffusion co- efficients is not diagonal. We call these systems reaction cross-diffusion systems. These systems possess interesting solutions that do not appear in the reaction self-diffusion systems that have a diagonal diffusion matrix. Compared to research conducted on re- action self-diffusion systems, the reaction cross-diffusion systems have received little attentions. The aim of this research is to extend existing literature on these systems. In this thesis we considered two-components reaction cross-diffusion systems. We find an ana- lytical solution of reaction diffusion system with replacing FitzHugh-Nagumo kinetics by quartic polynomial. Finding the analytical solution is extends analytical results pre- sented in [9]. This analytical solution is presented in a wave front profile. We study the possibility of imitating Fisher-KPP and ZFK-Nagumo front waves by our analytical solution which we have introduced. The existence of a quartic polynomial yields four different cases with respect to the positions of the roots of the quartic polynomial and the resting states of the wave front. We solve the problem numerically and compare the numerical solution to the analytical solution for those four cases. Finally, we extend the analysis of the different wave regimes in reaction cross- diffusion system with FitzHugh-Nagumo kinetics by varying parameters in the system using numerical continuation. We compute the speed of propagating waves in this sys- tem and show the corresponding eigenvalues of equilibrium which gives an indication about the profile of the propagating waves. We find a stable propagating wave that is not obtained by direct numerical simulation in [55]. We investigate the stability of prop- agating waves by using direct numerical simulation.
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Harichandran, Puveedran. "Propagating gravity currents in a turbulent fluid." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620514.
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Jøssang, Ivan. "Propagating transformations of state in reactive media." Thesis, University of Cambridge, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.621779.
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Zhu, Wenbo. "Soldering interconnects through self-propagating reaction process." Thesis, Loughborough University, 2016. https://dspace.lboro.ac.uk/2134/23259.
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This thesis presents a research into the solder interconnects made through the reactive bonding process based on the self-propagating reaction. A numerical study of soldering conditions in the heat affected zone (HAZ) during bonding was initially carried out in order to understand the self-propagating reactive bonding and the related influencing factors. This was subsequently followed by an extensive experimental work to evaluate the feasibility and reliability of the reactive bonding process to enable the optimisation of processing parameters, which had provided a detailed understanding in terms of interfacial characteristics and bonding strengths. In addition, by focusing on the microstructure of the bonds resulted from the self-propagating reactions, the interfacial reactions and microstructural evolution of the bonded structures and effects of high-temperature aging were studied in details and discussed accordingly. To study the soldering conditions, a 3D time-dependent model is established to describe the temperature and stress field induced during self-propagating reactions. The transient temperature and stress distribution at the critical locations are identified. This thus allows the prediction of the melting status of solder alloys and the stress concentration points (weak points) in the bond under certain soldering conditions, e.g. ambient temperature, pressure, dimension and type of solder materials. Experimentally, the characterisation of interconnects bonded using various materials under different technical conditions is carried out. This ultimately assists the understanding of the feasibility, reliability and failure modes of reactive bonding technique, as well as the criteria and optimisation to form robust joints. The formation of phases such as intermetallic compounds (IMCs) and mechanism of interfacial reactions during reactive bonding and subsequent aging are elaborated. The composition, dimension, distribution of phases have been examined through cross-sectional observations. The underlying temperature and stress profile determining the diffusion, crystallization and growth of phases are defined by numerical predictions. XXI Through the comparative analysis of the experimental and numerical results, the unique phases developed in the self-propagating joints are attributed to the solid-liquid-convective diffusion, directional solidification and non-equilibrium crystallization. The recrystallization and growth of phases during aging are revealed to be resulted from the solid-state diffusion and equilibration induced by the high-temperature heating. In conclusion, the interfacial reactions and microstructural evolution of interconnect developed through self-propagating reactive bonding are studied and correlated with the related influencing factors that has been obtained from these predictions and experiments. The results and findings enable the extensive uses of self-propagating reactive bonding technology for new design and assembly capable of various applications in electronic packaging. It also greatly contributes to the fundamentals of the crystallization and soldering mechanism of materials under the non-equilibrium conditions.
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Pfeffer, William Ted. "Structure and deformation in a propagating surge front /." Thesis, Connect to this title online; UW restricted, 1988. http://hdl.handle.net/1773/6810.
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McCann, Heather Alison. "Time-resolved measurement of freely propagating turbulent flames." Thesis, Imperial College London, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300096.
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Gracewski, Travis E. "Identifying internal best practices and propagating standard work." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61866.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (M.B.A.)--Massachusetts Institute of Technology, Sloan School of Management; in conjunction with the Leaders for Global Operations Program at MIT, 2010.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 59-60).
Standard work is commonly used in manufacturing and assembly operations to minimize process variation by providing detailed instruction to operators. Internal best practices are processes within the firm that achieve a more beneficial result when compared to alternative existing methods. Standard work is one approach to share best practices, and the challenge is in identifying their existence and effectively capturing the information in written documentation. Best practices are often tacit in nature, being difficult to codify and to put into writing. Effectively finding internal best practices and transferring them from tacit to explicit form as standard work is a desirable objective, improving knowledge transfer and operational efficiency within the company. There are techniques that can be applied to the standard work development process that increase the likelihood of successful best practice capture and organizational adoption. These techniques are developed and implemented through application at Sikorsky Aircraft, in creating and deploying a system of standard work titled, the "Assembly and Flight Operations Franchise Book." Major process steps in developing and sustaining standard work include an initial planning phase characterized by an upfront analysis, organizational structuring, and content framework development; and a sustaining phase characterized by a repeating cycle of best practice discovery, documentation, and sharing.
by Travis E. Gracewski.
M.B.A.
S.M.
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Giannitsis, Constantine 1971. "Non-linear saturation of vertically propagating Rossby waves." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/53043.
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Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, February 2001.Includes bibliographical references (p. 203-208).
Linear quasi-geostrophic theory predicts an exponential amplitude increase with height for Rossby waves propagating vertically through a stratified atmosphere, as a result of wave activity density conservation. At the same time layer-wise conservation of potential enstrophy constrains wave amplitudes, given the limited amount of potential enstrophy available in the initial mean flow. A break down of linear theory is thus expected above a certain critical wave amplitude, raising the question of how the non-linear flow reacts to limit the vertical penetration of waves. Keeping in mind the potential importance for the dynamics of the winter stratosphere, where strong wave penetration and amplitude growth are often observed, the issue of wave saturation in a non-linear flow is examined in a generally abstract context, through a variety of simple model studies. We thus consider the cases of a topographically forced barotropic beta plane channel model, of vertical propagation through a three-dimensional beta plane channel model, and of a polar coordinate model with realistic basic state and geometry. In the barotropic model transient wave growth is forced through the use of bottom topography and the deviations of the non-linear flow evolution from the predictions of both a linear and a quasi-linear analytical solution are examined for strong topographic anomalies. The growth of the forced wave is found to decelerate the zonal mean flow which in turn reduces the topographic forcing. Wave-mean flow interactions are thus found to be sufficient in leading to saturation of the eddy amplitudes. Interestingly it is the formation of zonal mean easterlies, rather than the depletion of mean available potential enstrophy, that is found to be the crucial factor in the saturation dynamics. Similar results are obtained for the case of vertical propagation through a three dimensional beta plane channel. The vertical penetration of the forced wave is shown to cause a reduction of the zonal mean winds and mean potential vorticity gradients in the center of the channel, eventually leading to the formation of either a critical line or a refractive index turning surface. In both cases the penetration of the wave to high altitudes is prohibited, thus constraining wave amplitudes. While signs of non-linear behaviour are clear in synoptic maps of potential vorticity, wave-wave interactions are found to play a secondary role in the saturation process. The results of the three-dimensional beta plane channel model are then extended to a more realistic set-up, using a polar coordinate model with a basic state based on the observed winter stratosphere climatology. The basic conclusions of the idealized study are shown to remain unchanged.
by Constantine Giannitsis.
Ph.D.
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Lawrence, Andrew Robert. "Observation of vertically-propagating atmospheric waves above Antarctica." Thesis, University of Cambridge, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.620693.
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Gilpin, Ruth Elisabeth. "Interaction between stream development and propagating extensional faults." Thesis, University of Edinburgh, 2002. http://hdl.handle.net/1842/13909.
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Li, Fang. "Modelling of premixed laminar flame propagating in channels." Thesis, University of Central Lancashire, 2004. http://clok.uclan.ac.uk/21904/.
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The dynamics of the intrinsically unstable premixed flames propagating in channels is studied by means of numerical modelling in this work. Critical conditions of extinction and the influence of the thermal-diffusive effect on the dynamics of flame propagating in planar channels with cold sidewalls under gravity is investigated. For the horizontally propagating flames, the appearance of inversion influences the effect of thermal-diffusion on the asymmetry of flame fronts. For upwards propagating flames, the convex shape of the flame imposed by the mode of ignition combined with buoyancy can suppress the thermal-diffusive effects; in contrast, the buoyancy alone cannot damp the thermal diffusive effects even for quite large Froud numbers in regard to the appearance of inversion. The variation of Lewis number has no essential effect on the planar flame shape formation when flame propagates downward. Lowering Lewis number can significantly decrease the critical conditions of extinction. However, if Lewis number is smaller than some limit, its further effect on the critical extinction conditions is unsignificant. In the two-step consecutive reaction, the effects of the ratio of Damkohler numbers, heat release rates, activation energy and Lewis number on the separation and fragmentation of flames are considered. The inversion is more pronounced in combustion with separated flame fronts than for single-step reactions. However, the inversion is obvious only when the two flame fronts are close enough to each other. Thus, the details of combusiiition chemistry may have a strong effect on the stability of the flame front. The thermal diffusive effect of the first flame is, in certain way, dominant and has influence on the second flame. The presence of the first reaction suppresses the thermal-diffusive effect of the second reaction in regard to the appearance of inversion. The propagation of flames at a variety of Reynolds number ranging from 70 to 1000 are explored. For longer channels or a flat initial flame front, the inversion of the flame is apparent for Reynolds number higher than 200. For large &, the computational grids should be very fine because of the small thickness of preheat zone. The Generalized Curvilinear Coordinate Gridding method is introduced and an elliptic grid generator based on the variational approach is employed to construct the solution-adaptive grids. However, we found out that the global structure of the algorithm required by the adaptive grid approach might be not as efficient as simplified non-adaptive grids for prospective use of massively parallel computers.
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Ali, Ahmed M. S. "Large-eddy simulations of premixed turbulent propagating flames." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/35297.
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The importance of turbulent premixed combustion comes from the fact that it is present in many engineering applications such as spark ignition engines and gas turbines. It is also present in explosion incidents where premixed mixture is burnt rapidly. Interaction of the flame with highly turbulent flows causes flame acceleration. Unsteady turbulent premixed combustion is a complex engineering phenomenon that is still not well understood. The nature of the unsteady turbulent premixed flame is so unstable, much wrinkled and too fast. A wide range of turbulence scales are formed in the flow region around the flame, which produce a variety of premixed combustion regimes during the course of flame propagation. Studies on premixed combustion have been a need for long time. Despite of its importance as a physical reference, combustion experiment is an expensive tool in both research and industry. Advances in premixed combustion predictive tools together with growing computational power have made computer simulation of flow and combustion in practical systems an effective alternative to experimental tests.
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Aminpour, Mohammad Ali. "Finite element analysis of propagating interface cracks in composites /." Thesis, Connect to this title online; UW restricted, 1986. http://hdl.handle.net/1773/9993.
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Chao, Yu-Hsing. "A propagating ductile fracture model for a pressurized pipeline /." Thesis, Connect to this title online; UW restricted, 1987. http://hdl.handle.net/1773/7056.
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Backeman, Peter. "Propagating the nVector Constraint : Haplotype Inference using Constraint Programming." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-211862.
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Genetics research is a wide field and needs computer aid in many different areas. One such problem is the haplotype inference problem by pure parsimony (HIPP). In this thesis the HIPP problem is attacked with a constraint programming (CP) model based on the nVector constraint, for which a new propagator is designed. The results show that the current state-of-the-art model based on SAT-solvers are in general the most efficient, but that the CP approach in some cases finds a better solution when time is limited.
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Reinhart, Marcia. "Calcium signalling cascades triggered by back-propagating action potentials." Thesis, University of Oxford, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.540295.
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Hyland, Luke. "A study of fluxons propagating in annular Josephson junctions." Thesis, Loughborough University, 2013. https://dspace.lboro.ac.uk/2134/13445.
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In this research we looked at how fluxons propagate in an annular Josephson junction containing a microshort. We studied this from a theoretical stance and looked at how a single fluxon based on the sine-Grodon soliton equation propagates in this type of junction. It has been seen from a variety of studies that fluxons have many applications through the use of Josephson junctions. The aim of this thesis was to see whether a fluxon will show new properties whilst coming into contact with a microshort located in the junction. We also explored the different geometries a Josephson junction can have and whether that would show the fluxon to present new phenomena. We will also examine point particle systems. With this in mind we took a keen interest in how the interaction between two of these particles in a double well potential would present itself and whether a relationship would become apparent. Alongside the point particle system we modelled fluxons in a double well potential and comment on the similarities with the point particle system. With the aid of the computer programmes Mathematica and COMSOL Multiphysics we were able to compute these different theoretical models and present the work in a logical order with a progression from a single point particle in a double well potential to a fluxon in a heart-shaped Josephson junction. We have looked at current theories and ideas present in this area of condensed matter physics and have explained these in the subsequent thesis.
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Landesman, Barbara Tehan. "A new mathematical model for a propagating Gaussian beam." Diss., The University of Arizona, 1988. http://hdl.handle.net/10150/184545.
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A new mathematical model for the fundamental mode of a propagating Gaussian beam is presented. The model is two-fold, consisting of a mathematical expression and a corresponding geometrical representation which interprets the expression in the light of geometrical optics. The mathematical description arises from the (0,0) order of a new family of exact, closed-form solutions to the scalar Helmholtz equation. The family consists of nonseparable functions in the oblate spheroidal coordinate system and can easily be transformed to a different set of solutions in the prolate spheroidal coordinate system, where the (0,0) order is a spherical wave. This transformation consists of two substitutions in the coordinate system parameters and represents a more general method of obtaining a Gaussian beam from a spherical wave than assuming a complex point source on axis. Further, each higher-order member of the family of solutions possesses an amplitude consisting of a finite number of higher-order terms with a zero-order term that is Gaussian. The geometrical interpretation employs the skew-line generator of a hyperboloid of one sheet as a ray-like element on a contour of constant amplitude in the Gaussian beam. The geometrical characteristics of the skew line and the consequences of treating it as a ray are explored in depth. The skew line is ultimately used to build a nonorthogonal coordinate system which allows straight-line propagation of a Gaussian beam in three-dimensional space. Highlights of the research into other methods used to model a propagating Gaussian beam--such as complex rays, complex point sources and complex argument functions--are reviewed and compared with this work.
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Renger, Jan. "Excitation, Interaction, and Scattering of Localized and Propagating Surface Polaritons." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2006. http://nbn-resolving.de/urn:nbn:de:swb:14-1153478195966-65404.
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Surface polaritons, i.e., collective oscillations of the surface charges, strongly influence the optical response at the micro- and nanoscale and have to be accounted for in modern nanotechnology. Within this thesis, certain basic phenomena involving surface polaritons are investigated by means of the semianalytical multiple-multipole (MMP) method. The results are compared to experiments. In the first part, the surface plasmon resonance (SPR) of metal nanoparticles is analyzed. This resonant collective oscillation of the free electrons in a metallic nanoparticle leads to an enhancement and confinement of the local electric field at optical frequencies. The local electric field can be further increased by tailoring the shape of the particle or by using near-field-interacting dimers or trimers of gold nanospheres. The hot spots found under such conditions increase the sensitivity of surface-enhanced Raman scattering by several orders of magnitude and simultaneously reduce the probed volume, thereby providing single-molecule sensitivity. The sub-wavelength-confined strong electromagnetic field associated with a SPR provides the basis for scattering-type near-field optical microscopy or tip-enhanced Raman spectroscopy, where the metal particle serves as a probe that is scanned laterally in the vicinity of a substrate. The presence of the latter causes a characteristic shift of the SPR towards lower frequencies. This effect originates in the near-field interaction of the surface charges on the objects. Furthermore, the excitation of higher-order modes becomes possible in case of an excitation by a strongly inhomogeneous wave, such as an evanescent wave. These modes may significantly contribute to the near field but have only very little influence on the far-field signature. Instead of using resonant probes, one may place a nonresonant probe in the vicinity of a substrate having a high density of electromagnetic surface states. This also produces a resonance of the light scattering by the system. Especially polar crystals, such as the investigated silicon carbide, feature such a high density of surface phonon polariton states in the mid-infrared spectral region, which can be excited due to the near-field interaction with a polarized particle. Thereby, a resonance is created leading to a strong increase of the electric field at the interface. In the second part of the thesis, special emphasis is put on surface plasmon polaritons (SPPs). Such propagating surface waves can be excited directly by plane waves only at patterned interfaces. This process is studied for the case of a groove. The groove breaks the translational invariance, so that the SPPs can be launched locally at the edges of the groove. Additionally, the mode(s) inside the groove are excited. These modes can basically be understood as metal-insulator-metal cavity modes. Their dispersion strongly depends on the groove width. The cavity behavior caused by the finite depth provides another degree of freedom for optimizing the SPP excitation by plane waves. Thin metallic films deposited on glass offer two different SPP waveguide modes, each of which can be addressed preferentially by a proper choice of the width of the groove. The reflection, transmission, scattering, and the conversion of the modes at discontinuities such as edges, steps, barriers, and grooves can be controlled by appropriately designing the geometry at the nanoscale. Furthermore, the excitation of SPPs at single and multiple slits in thin-film metal waveguides on glass and their propagation and scattering is shown by scanning near-field optical experiments. Such waveguide structures offer a means for transporting light in a confined way. Especially triangularly shaped waveguides can be used to guide light in sub-wavelength spacesDie Wechselwirkung von elektromagnetischer Strahlung mit subwellenlängenkleinen Teilchen bzw. Oberflächenstrukturen ermöglicht nicht nur eine Miniaturisierung optischer Geräte, sondern erlaubt sehr interessante Anwendungen, beispielsweise in der Sensorik und Nahfeldoptik. In der vorliegenden Arbeit werden die zu Grunde liegenden Effekte im Rahmen der klassischen Elektrodynamik mit Hilfe der semianalytischen Methode der multiplen Multipole (MMP) analysiert, und die Ergebnisse werden mit Experimenten verglichen. Im ersten Teil werden Oberflächenplasmonenresonanzen (engl. surface plasmon resonance - SPR) einzelner und wechselwirkender Metallteilchen untersucht. Die dabei auftretende resonante kollektive Schwingung der freien Elektronen des Partikels bewirkt eine deutliche Erhöhung und Lokalisierung des elektromagnetischen Feldes in seiner Umgebung. Die spektrale Position und die Stärke der SPR eines Nanoteilchens, die von dessen geometrischer Form, Permittivität und Umgebung abhängen, können nur im Grenzfall sehr kleiner Teilchen elektrostatisch beschrieben werden, wohingegen der verwendete semianalytische MMP-Ansatz weitaus flexibler ist und insbesondere auch auf größere Partikel, Teilchen mit komplizierterer Form bzw. Ensembles von Partikeln anwendbar ist. Die betrachteten einzelnen kleinen (< Wellenlänge) Goldkügelchen und Silberellipsoide besitzen eine stark ausgeprägte SPR im sichtbaren optischen Bereich. Diese ist auf eine dipolartige Polarisierung des Teilchens zurückzuführen. Höhere Moden der Polarisation können entweder als Folge von Retardierungseffekten an größeren (mit der Wellenlänge vergleichbaren) Teilchen oder bei der Verwendung inhomogener (z.B. evaneszenter) Wellen angeregt werden. Partikel, die sich in der Nähe eines Substrates befinden, unterliegen der Nahfeldwechselwirkung zwischen den (lichtinduzierten) Oberflächenladungen auf der Oberfläche des Teilchens und des Substrats. Dies führt zu einer Verschiebung der SPR zu niedrigeren Frequenzen und einer Erhöhung des lokalen elektrischen Feldes. Letzteres bildet die Grundlage z.B. der spitzenverstärkten Raman-Spektroskopie und der optischen Nahfeldmikroskopie mit Streulichtdetektion. Dasselbe Prinzip bewirkt ein stark überhöhtes elektrisches Feld zwischen miteinander wechselwirkenden Nanopartikeln, welches z.B. die Sensitivität der oberflächenverstärkten Raman-Mikroskopie um mehrere Größenordnungen steigern kann. Im Gegensatz zur SPR einzelner Nanopartikel kann die Resonanz der Lichtstreuung im Fall eines Partikels in der Nähe eines Substrats aus der durch die Nahfeldwechselwirkung induzierten Anregung elektromagnetischer Oberflächenzustände entstehen. Diese wirken ihrerseits auf das Nanopartikel zurück, wobei eine resonante Lichtstreuung beobachtbar ist. Dieser, am Beispiel einer metallischen Nahfeldsonde über einem Siliziumcarbid-Substrat analysierte, Effekt ermöglicht bei einer ganzen Klasse von polaren Kristallen interessante Anwendungen in der Mikroskopie und Sensorik basierend auf der hohen Dichte von Oberflächenphononpolaritonen dieser Kristalle im mittleren infraroten Spektralbereich und deren nahfeldinduzierten Anregung. Im zweiten Teil der Arbeit werden kollektive Anregungen von Elektronen an Metalloberflächen untersucht. Die dabei auftretenden plasmonischen Oberflächenwellen (engl. surface plasmon polaritons - SPPs) weisen einen exponentiellen Abfall der Intensität senkrecht zur Grenzfläche auf. Diese starke Lokalisierung der Energie an der Oberfläche bildet die Grundlage vieler Anwendungen, z.B. im Bereich der hochempfindlichen Detektion (bio)chemischer Verbindungen oder für eine zweidimensionale Optik (engl. plasmonics). Das Aufheben der Translationsinvarianz längs der Oberfläche ermöglicht die direkte Anregung von SPPs durch ebene Wellen. Die Abhängigkeit dieser Kopplung von der Geometrie wird am Beispiel eines Nanograbens untersucht. Dabei werden neben den SPPs ebenfalls eine oder mehrere Moden im Graben angeregt. Folglich ermöglicht die geeignete Wahl der Grabengeometrie die Optimierung der Umwandlung von ebenen Wellen in SPPs. Im - in der Praxis weit verbreiteten - Fall asymmetrisch eingebetteter metallischer Dünnschichtwellenleiter existieren zwei Moden. In Abhängigkeit von der Grabenbreite kann die eine oder die andere Mode bevorzugt angeregt werden. Die Analyse der Wechselwirkung von SPPs mit Oberflächenstrukturen, z.B. Kanten, Stufen, Barrieren und Gräben, zeigt die Möglichkeit der Steuerung der Reflexions-, Transmissions- und Abstrahleigenschaften durch die gezielte Wahl der Geometrie der "Oberflächendefekte" auf der Nanoskala und deckt die zu Grunde liegenden Mechanismen und die daraus resultierenden Anforderungen bei der Herstellung neuer plasmonischer Komponenten auf. Exemplarisch wird das Prinzip der SPP-Anregung an einzelnen und mehreren Gräben in dünnen metallischen Filmen sowie der subwellenlängen Feldlokalisierung an sich verjüngenden metallischen Dünnschichtwellenleitern unter Verwendung der optischen Nahfeldmikroskopie experimentell gezeigt
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MEN'SHOV, Igor, and Yoshiaki NAKAMURA. "On Instability of Acoustic Waves Propagating in Stratified Vortical Flows." The Japan Society of Mechanical Engineers, 2002. http://hdl.handle.net/2237/9091.
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Lally, Richard W. "Analysis of radio frequency radiation from a propagating electron beam." Thesis, Monterey, California. Naval Postgraduate School, 1990. http://hdl.handle.net/10945/37527.
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Approved for public release, distribution is unlimitedAn experiment was conducted which measured the Radio Frequency (RF) radiation from the PHERMEX accelerator, capable of 30 MeV and 600 A. This was accomplished by placing TEM horn antennae at varying angles from the path of the electron beam. The signals received by the antennae were then recorded by using a Digitizing Camera System (DCS). Measurements were taken of the radiation from propagating and non-propagating beams, beams with energy above and below Cherenkov threshold, and beams with varied currents. The captured RF signals and their corresponding frequency spectra were then analyzed. This analysis showed that the radio frequency radiation from the beams below the cherenkov threshold contained primarily transition radiation; when above, diffracted Cherenkov radiation was observed. Non-propagating beams produced larger-angle radiation and had less definition in their spectrum. All electric fields measured were proportional to the beam current. Lastly, the electron beam pulse width and separation were determined by both the received signals and their spectrum.
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Moore, David Franklin. "Passive sonar target recognition using a back-propagating neural network." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/30962.
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Approved for public release; distribution is unlimitedThe prompt and accurate processing of sonar data is essential in undersea warfare. The ability to quickly detect and classify sonar targets is crucial to the performance and survivability of all navy surface ships and submarines. With the advent of neural network technology, new opportunities have arisen which could greatly enhance current sonar target recognition capabilities. The main objective of this research is to demonstrate the practical usage of neural networks in recognizing the acoustic signatures of passive sonar targets using simulated-at-sea conditions. We will review the theory behind neural networks, the problems associated with recognizing acoustic signals in an underwater environment, and we will make a detailed case study of a neural network's performance using test data generated from simulated sonar targets.
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Johnson, Matthew E. "Relaxation effects on sonic boom waveforms propagating through the atmosphere." Thesis, University of East Anglia, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.396723.
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Kuzmenko, Dmytro. "Microwave-initiated self-propagating high-temperature synthesis of submicron SiC." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.404042.
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Parry, Simon Wyn. "The interaction between a propagating coastal vortex and topographic waves." Thesis, University College London (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.411324.
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Affleck, Louise. "Self propagating high temperature synthesis of ferrites in magnetic fields." Thesis, University College London (University of London), 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268412.
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So, Damon Wai Kwan. "The dynamics of two-dimensional propagating jumps and density currents." Thesis, Imperial College London, 1986. http://hdl.handle.net/10044/1/38165.
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Welch, Matthew G. "Compressing and propagating solitons in hollow core photonic crystal fibre." Thesis, University of Bath, 2010. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.520840.
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The development of photonic crystal fibre from conventional optical fibre follows a trend in the development of materials, to create composites and structured materials on smaller and smaller scales. In fact the great success of photonic crystal fibre is largely due to the ability to structure it on scales comparable to the wavelength of light. It is this micron size structure that allows the creation of an (out of plane) optical bandgap in silica and allows hollow core fibre to guide light in an air core freeing the guided mode from the properties of bulk silica. This thesis focuses on the propagation and compression of high peak power optical solitons in hollow core fibre. As the Kerr nonlinear response of air is approximately a thousand times less than that of silica, the air core of hollow core fibre can support much higher peak powers than conventional optical fibre without the manifestation of nonlinear effects, making it ideal for the delivery of high peak power laser pulses. Coupled with this, hollow core fibre has a large region of anomalous dispersion in its transmission window allowing optical pulses to be transmitted as temporal solitons freeing them from the effects of dispersion. The author started his Ph.D. in 2006, three years after the first demonstration of soliton propagation in hollow core fibre and as the first demonstrations of soliton compression in hollow core fibre were being undertaken. Work by the author to build upon these early demonstrations is presented in this thesis in the following manner: Chapters 1, 2 and 3 are theory chapters. Chapter 1 explains the background waveguide theory and theory of nonlinear optics that is used throughout the thesis. Chapter 2 details the properties of photonic crystal fibres focusing on hollow core fibre. Chapter 3 details recent papers relevant to the propagation and compression of solitons in hollow core fibre. Chapters 4, 5 and 6 are experimental chapters reporting work undertaken by the author. Chapter 4 focuses on modifying the nonlinearity of hollow core fibre and measuring the dispersion of hollow core fibre accurately. Chapter 5 focuses on the compression of chirped and unchirped picosecond pulses in dispersion decreasing hollow core fibre tapers. Chapter 6 reports the compression in hollow core fibre of femtosecond pulses centred at 540nm wavelength through soliton effect compression.
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Klettner, Christian. "On the fundamental principles of waves propagating over complex geometry." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/624504/.
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In 2004 the Indian Ocean tsunami once again showed the world the destructive capabilities of these natural disasters. In this work this practical problem was abstracted to a simplified problem of waves propagating over complex geometry, specifically the processes involved in a solitary and leading depression wave interacting with a bottom seated semi-cylinder over uniform depth and shoaling topography. A purpose written Arbitrary-Lagrangian-Eulerian finite element code to solve the two-dimensional Navier-Stokes equation was developed. It utilised high performance libraries PETSc, Hypre and Triangle to perform simulations with approximately 8 million degrees of freedom across 256 cores on UCL’s supercomputer, Legion. The code was validated against five benchmark test cases and mesh convergence was shown. The code exhibited linear weak scaling and superlinear strong scaling and with this capability, these problems could be analysed using two tools; firstly, global conservation measures such momentum and energy. The rate of change of these integral measures were related to forces on obstacles and boundaries and agreement with model estimates was found even when the wave/boundary interactions were complex. Secondly, flow diagnostics such as the rate of strain and vorticity were used to characterise the velocity field. The large scale capability also allowed the free surface boundary layer to be captured which revealed an (weaker) oscillatory nature of that found at a rigid boundary. The code could not handle breaking and inundation, therefore experiments were carried out to study a depression wave as it interacts and breaks on a beach. Using a novel mechanism for generating isolated depression waves, general features such as extent and speed of recession and surge where characterised and it is noteworthy that the shoreline recession, a defining feature of shoaling depression waves, which was seen during the 2004 tsunami, was captured.
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Ho, William Ka Wing. "Organisation of the feather periodic pattern through propagating molecular waves." Thesis, University of Edinburgh, 2016. http://hdl.handle.net/1842/25777.
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Members of the class Aves possess integumentary structures which distinguish them from other vertebrate lineages. The characteristic integumentary structure that defines the Aves from other vertebrates are the feathers, whose functions include insulation, camouflage, visual display, gliding, and powered flight. The recent discoveries of theropod dinosaur fossils displaying feather-like structures have led to interest in the morphological innovations of the feathers, which are associated with the evolution of flight in Aves. Most modern birds, display a highly ordered, hexagonal arrangement of feather follicles, which aids in the streamlining of the body to increase aerodynamic efficiency. Using the chicken embryo as a developmental model, I address the cellular and molecular processes involved in the initiation and formation of a high fidelity periodic pattern of feather primordia. From my studies, I propose a model in which the induction of individual feather primordia begins with the activation of FGF20 expression. This gene encodes a protein that serves as a chemoattractant. Aggregation of cells towards sources of FGF20 stimulates and reinforces FGF20 expression and also induces the expression of BMP4. Via a reaction-diffusion-like mechanism, BMP4 acts to limit the growth of the cell aggregate and promotes lateral inhibition to prevent fusions between neighbouring feather primordia through transcriptional regulation of FGF20. In order to achieve a high fidelity periodic pattern of feather primordia, three components are required; 1) a competent epidermis displaying β-Catenin and EDAR expression, 2) wave-like propagation of EDA expression, which acts synergistically with β-Catenin expression to activate FGF20 expression at the β-Catenin/EDA junction, 3) and a dermis of sufficient cell density. The spatiotemporal wave-like propagation of EDA expression, specifically, promotes the sequential induction of new feather primordium rows and is associated with the formation of a high fidelity periodic pattern. The importance of these three components appears to be evolutionarily conserved among the Aves and differences in the periodic pattern of feather primordia between species can be explained by how the three components are expressed or regulated in individual species. Independent losses of flight in ratites, such as ostriches and emus, are associated with the loss of feather pattern fidelity. In emus, this loss of pattern fidelity results from the delayed formation of a dermis of sufficient cell density, which prevents the induction of feather primordium formation within the dorsal tract, despite the presence of a fully primed and competent epidermis. These studies demonstrate how the precise feather pattern arises during embryonic development in birds, and how feather patterns can be modified through differential regulation of the molecular and cellular toolkit involved in feather primordium induction in different bird species.
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Akour, Mohammed Abd Alwahab. "Towards Change Propagating Test Models In Autonomic and Adaptive Systems." Diss., North Dakota State University, 2012. https://hdl.handle.net/10365/26504.
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The major motivation for self-adaptive computing systems is the self-adjustment of the software according to a changing environment. Adaptive computing systems can add, remove, and replace their own components in response to changes in the system itself and in the operating environment of a software system. Although these systems may provide a certain degree of confidence against new environments, their structural and behavioral changes should be validated after adaptation occurs at runtime.
Testing dynamically adaptive systems is extremely challenging because both the structure and behavior of the system may change during its execution. After self adaptation occurs in autonomic software, new components may be integrated to the software system. When new components are incorporated, testing them becomes vital phase for ensuring that they will interact and behave as expected. When self adaptation is about removing existing components, a predefined test set may no longer be applicable due to changes in the program structure. Investigating techniques for dynamically updating regression tests after adaptation is therefore necessary to ensure such approaches can be applied in practice.
We propose a model-driven approach that is based on change propagation for synchronizing a runtime test model for a software system with the model of its component structure after dynamic adaptation. A workflow and meta-model to support the approach was provided, referred to as Test Information Propagation (TIP). To demonstrate TIP, a prototype was developed that simulates a reductive and additive change to an autonomic, service-oriented healthcare application.
To demonstrate the generalization of our TIP approach to be instantiated into the domain of up-to-date runtime testing for self-adaptive software systems, the TIP approach was applied to the self-adaptive JPacman 3.0 system.
To measure the accuracy of the TIP engine, we consider and compare the work of a developer who manually identifyied changes that should be performed to update the test model after self-adaptation occurs in self-adaptive systems in our study. The experiments show how TIP is highly accurate for reductive change propagation across self-adaptive systems. Promising results have been achieved in simulating the additive changes as well.
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Cho, Chang Gi. "Controlled polymerization of alkyl vinyl ethers via 'covalent' propagating species." Diss., Virginia Polytechnic Institute and State University, 1988. http://hdl.handle.net/10919/53930.
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The study of the polymerization of alkyl vinyl ethers initiated by HI/I₂ catalyst is directed into two areas: the kinetics of the polymerization and the strategy of amine functionalized prepolymer synthesis.
The polymerization reactions show living behavior in nonpolar solvents at low temperatures. The observed rate of polymerization under reaction conditions is linearly dependent on the initial concentration of hydrogen iodide and iodine, respectively. However, the monomer concentration does not influence the rate of polymerization(apparent zero-order). Two possible reaction schemes are proposed from the observed rate equation and attempts are made to distinguish them by using UV/visible spectroscopy and carbon-13 NMR spectroscopy. In both schemes a reversible interaction between a monomer and an iodine molecule is postulated as a necessary elemental reaction to fit the observed expression for the rate of polymerization. From spectroscopic analysis results, the interaction between the iodide compound(chain end) and the iodine molecule seems to be very weak compared to the interaction between the monomer and the iodine molecule.
A synthetic strategy for amine functionalized prepolymer synthesis has been developed via a series of model reactions. Incorporation of a styrenic monomer at the propagating chain end of living poly(alkyl vinyl ethers) provides a convenient intermediate synthesis of a relatively stable amine functionalized prepolymer. Proper selection of substituents at the styrenic monomer optimizes the cross addition reaction and amination reactions. Linear alkylamines with lower carbon numbers are used in the amination reaction in order to promote the nucleophilic substitution reaction and to minimize possible elimination reactions. A series of amine functionalized oligomers are synthesized by employing the synthetic strategy in combination with the previous kinetic result of the homopolymerization. For oligomers, incorporation of a few units of ethyl vinyl ethers at the chain end facilitates the cross addition reaction. Synthesized amines are characterized by various spectroscopic methods. Then, titrated molecular weights show good agreement with their theoretical molecular weights in several cases.Ph. D.
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Lee, Jonghee. "Fracture analysis of a propagating crack in a ductile material /." Thesis, Connect to this title online; UW restricted, 1996. http://hdl.handle.net/1773/7081.
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Lally, Ricahrd W. "Analysis of radio frequency radiation from a propagating electron beam." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA237941.
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Thesis (M.S. in Physics)--Naval Postgraduate School, June 2009.Thesis Advisor(s): Neighbours, John R. "June 1990." Second Reader: Buskirk, Fred R. Description based on title screen as viewed on 19 October 2009. DTIC Identifier(s): Electron accelerators, leakage (electrical), phermex acceleration, DCS (Digitizing Camera System), theses. Author(s) subject terms: Cherenkov radiation, transition radiations, EMP, radio frequency radiation, electron beam. Includes bibliographical references (p. 78-79). Also available in print.
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Scott, Michael Brian. "General relativistic shock-waves propagating at the speed of light /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
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Tokyay, Talia Ekin. "A LES study on gravity currents propagating over roughness elements." Diss., University of Iowa, 2010. https://ir.uiowa.edu/etd/610.
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Predicting the evolution of turbulent gravity currents is of great interest in many areas of geophysics and engineering, in particular due to their impact on the environment. In most practical applications in river, coastal and ocean engineering, gravity currents propagate over loose surfaces containing large scale bedforms (e.g., dunes). In others, arrays of obstacles (e.g., ribs) are often used as protective measures on hilly terrains to stop or slow down gravity currents in the form of powder-snow avalanches. To predict the capacity of a turbulent gravity current propagating over a loose bed to entrain, carry, and deposit sediment requires a detailed understanding of its structure and the role played by the large-scale instabilities present in the flow.
The present study uses high-resolution Large Eddy Simulation to study the physics of high Reynolds number compositional Boussinesq gravity currents with large and small volume of release in lock-exchange configurations and their dynamic effects on various obstacles (e.g., bedforms, flow retarding obstacles, submerged dams that are used to control sediment deposition in reservoirs). The study shows that gravity currents propagating over large-scale roughness elements reach a turbulent drag-dominated regime in which the front velocity decays proportional to t-1/2, similar to the case of gravity currents propagating within a porous medium. Though the establishment of a regime in which the flow evolution is mainly determined by the balance between the turbulent drag and the buoyancy force driving the flow was expected, the fact that the law of decay of the front velocity with time is identical for gravity currents propagating over roughness elements and in a porous medium of uniform porosity is not obvious.
The simulations provide detailed information on the temporal evolutions of the front velocity, energy balance, sediment entrainment capacity and the flow instabilities, and of the distributions of the density, velocity, local dissipation rate and bed shear stresses at different stages of the propagation of the gravity current. The study investigates of the effect of the shape and relative size of the obstacles, with respect to the current height, on the structure of the current and on the differences with the simpler, but much more widely studied case of a gravity current propagating over a flat smooth surface. For example, the simulation results are used to explain why gravity currents propagating over dunes have a much larger capacity to entrain sediment than gravity currents propagating over ribs of the same height and with similar spacing.
The accurate estimation of impact of gravity current on the structures over its path is very important from engineering point of view since many submerged cables over the ocean bottom or submerged dams in reservoirs are under the risk of such impacts. The simulations of gravity currents propagating past arrays of ribs or isolated dams are used to estimate the characteristic times and magnitudes of the hydrodynamic impact forces on these obstacles. This information is crucial for the proper design of these structures. The study shows the critical role played by flow disturbances (e.g., backward propagating hydraulic jumps) that form as a result of the interaction between the current and the large-scale obstacles. Finally, the study investigates scale effects between the Reynolds numbers at which most experimental investigations of gravity currents are conducted and Reynolds numbers at field scale.
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Twardus, Jesse. "The use of heuristics in identifying self-propagating malicious mobile code." Morgantown, W. Va. : [West Virginia University Libraries], 2005. https://eidr.wvu.edu/etd/documentdata.eTD?documentid=4195.
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Thesis (M.S.)--West Virginia University, 2005.Title from document title page. Document formatted into pages; contains viii, 104 p. : ill. (some col.). Includes abstract. Includes bibliographical references (p. 89-92).
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Sleath, John. "A new model of spiral galaxies based on propagating star formation." Thesis, University of Cambridge, 1996. https://www.repository.cam.ac.uk/handle/1810/241031.
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Many models exist in the literature of either star formation or galactic structure, but the former concentrate on small-scale details, whilst the latter, if they include star formation at all, adopt a very simple approach, for example by assuming a power law relationship between the rate of star formation and the gas density (a Schmidt Law). The new model described in this dissertation bridges the gap between these two extremes by adopting a simple, but not simplistic, approach to the detailed physics, allowing the effects of star formation on the broader scale to be investigated. 'Propagating star formation' considers the collapse of molecular clouds (and subsequent creation of new stars) to be triggered by the passage of a shock wave resulting from the supernovae explosions of members of the previous generation of stars. The approach taken is a stochastic one, i.e. we determine from the mass of a cloud the probability of star formation occurring, given that it has been shocked. Models using a similar approach have been described before, but the new model is unique in that it uses a particulate representation of the gas clouds and stellar associations. This permits us to simulate collisions between the particles as they orbit in a realistic galactic gravitational potential and more importantly, to impose a spiral density wave perturbation in a natural way. Such waves arise naturally in N-body simulations where the collective forces between particles are considered explicitly, but we are more interested in its effect on the star formation rate, and hence to make the code more manageable, impose the perturbation by hand. The model has been extremely successful; for example, predicting accurately, with no free parameters, the cluster formation rate for the Milky Way. A Schmidt Law arises as a natural consequence and with a power law index which is consistent with observational constraints. A wide range of galactic morphologies can be produced, including long-lived two-armed grand-design spirals, which have not resulted from any of the previous propagating star formation models. The spiral density wave orders the star formation, but does not simply result in the star formation tracing directly the potential minima - it is found that the pitch angles of the imposed and observed spiral patterns differ significantly. Moreover, the pitch angle of the observed pattern exhibits a maximum value equal to the maximum pitch angle observed in late-type spirals. To compare the results of this, and other, models of galactic structure with observed galaxies, we require some way of classifying the appearance of the data sets. There already exist a number of schemes, but they are all somewhat subjective, and a reliable, quantitative approach would form a valuable addition. I have investigated a number of schemes, namely Fourier transforms, minimal spanning tree edge-length spectra and multifractal dimensions, and considered their application to both simulated and observed data. The results of the analysis are encouraging, particularly for the multifractals, although it is not as yet possible to calculate a single, unique number which fully characterises the morphology.
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Wong, Wai-ting. "Propagating native tree seedlings for forest rehabilitation in Hong Kong, China." Click to view the E-thesis via HKUTO, 2006. http://sunzi.lib.hku.hk/hkuto/record/B37670578.
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Williams, David. "Modelling crustal earthquakes as propagating shear faults in a layered earth." Thesis, University of Oxford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365369.
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Bowen, Christopher Rhys. "Manufacture of multiphase ceramic composites by self-propagating high-temperature synthesis." Thesis, University of Oxford, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306903.
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