Dissertations / Theses on the topic 'Dynamics in media'
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Durling, Nicola Emma. "Reaction dynamics in supercritical media." Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/30077.
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An in situ dielectric method is used to measure aromatic solubilities as a function of pressure and to follow the progress of an Esterification, Aldol and Friedel-Crafts reactions in supercritical (sc) difluoromethane (HFC 32). This is achieved by measuring the changes in the sc solution capacitance as the composition of the sc system changes. The solubility of p-hydroxybenzoic, p-toluic, p-aminobenzoic and p-chlorobenzoic acids and also p-chlorophenol and p-aminophenol is determined in sc HFC 32 at 363 K using the dielectric method, and presented as a function of pressure. The compounds are shown to be more soluble than in the commonly employed sc solvent, CO2 under comparative conditions. The enhancement factor is used as a way of expressing solubility to remove the effect of vapour pressure and the observed trend in solubility is found to be highly dependent on the polarity of the substituents present on the aromatic ring. The use of the in situ dielectric method for monitoring a reaction in a sc fluid is proposed. The Esterification. Aldol and Friedel-Crafts reactions in sc HFC 32 were used to test the applicability of this technique. These are the first reported reactions to be carried out in sc HFC 32. The rate/equilibrium constants for these reactions are determined and found to decrease with increasing pressure. It is proposed that the observed high reaction rates at low pressure are due to local composition enhancements. Determination of solvent-solute interactions is key to the understanding of solvent, properties in liquids and sc fluids. The Kamlet-Taft parameters were determined for HFC 32 and 1,1,1,2-tetrafluoroethane (HFC 134a) as a function of temperature and pressure in the range 313 to 403 K and 50 to 220 bar using three solvatochromic dyes. It is shown that both solvents exhibit considerable hydrogen bond donor and acceptor properties and these parameters also obey the three region density model often invoked when describing the polarisability/dipolarity parameter in sc fluids.
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Molale, Dimpho Millicent. "A computational evaluation of flow through porous media." Thesis, Link to the online version, 2007. http://hdl.handle.net/10019/686.
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Iotov, Mihail S. Goddard William A. "Diffusion in amorphous media." Diss., Pasadena, Calif. : California Institute of Technology, 1998.
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Thesis (Ph. D.)--California Institute of Technology, 1998. UM #9842258.Advisor names found in the Acknowledgments pages of the thesis. Title from home page. Viewed 02/01/2010. Includes bibliographical references.
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Reitberger, Wolfgang Heinrich. "Affective Dynamics in Responsive Media Spaces." Thesis, Georgia Institute of Technology, 2004. http://hdl.handle.net/1853/4975.
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In this thesis computer-mediated human interaction and human computer interaction in responsive spaces are discussed. Can such spaces be de-signed to create an affective response from the players? What are the de-sign heuristics for a space that allows for the establishment of affective dy-namics? I research the user experience of players of existing spaces built by the Topological Media Lab. In addition to that I review other relevant ex-perimental interfaces, e.g. works by Myron Krueger and my own earlier piece Riviera in order to analyze their affective dynamics. Also, I review the different applications and programming paradigms involved in authoring such spaces (e.g. Real-time systems like Max/MSP/Jitter and EyeCon) and how to apply them in compliance with the design heuristics.
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Palapanidis, Konstantinos. "Relativistic fluid dynamics and electromagnetic media." Thesis, University of Southampton, 2018. https://eprints.soton.ac.uk/427364/.
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In this thesis we describe fluid media with electromagnetic properties in the context of general relativity. Using the variational principle we derive the Einstein equations from the Einstein-Hilbert action, the Euler-Lagrange equations for a multicomponent fluid and the Maxwell equations. We provide a covariant description of linear electromagnetic media and we also discuss media with non linear electromagnetic properties. We also provide a formula that generalises the expression for the Lagrangian of linear media, to that of non linear media and we discuss a set of constraints for linear electromagnetic media in terms of the material derivative. We discuss a model for a multifluid with general electromagnetic properties. We also derive the limit for the single fluid ideal magnetohydrodynamics in general relativistic context. In the final part we look into the linear stability of specific systems using the geometric optics method along with the notion of "fast" and "slow" variables. Employing this method we reproduce a number of results in Newtonian context, building gradually to the derivation of the magnetorotational instability. Additionally, we discuss the vanishing magnetic field of this configuration. Subsequently, considering an unperturbed background spacetime we derive the characteristic equations describing the relativistic inertial waves, the relativistic Rayleigh shearing instability and the relativistic magnetorotational instability. Finally, by assuming a low velocity and flat metric limit of the relativistic equations we reproduce the Newtonian characteristic equations.
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Xu, Jinshan. "Dynamics and synchronization in biological excitable media." Phd thesis, Ecole normale supérieure de lyon - ENS LYON, 2012. http://tel.archives-ouvertes.fr/tel-00776373.
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This thesis investigates the origin of spontaneous activity in the uterus. This organ does not show any activity until shortly before delivery, where fast and efficient contractions are generated. The aim of this work is to provide insight into the origin of spontaneous oscillations and into the transition from asynchronous to synchronized activity in the pregnant uterus. One intriguing aspect in the uterus is the absence of any pacemaker cell. The organ is composed of muscular cells, which are excitable, and connective cells, whose behavior is purely passive; None of these cells, taken in isolation, spontaneously oscillates. We develop an hypothesis based on the observed strong increase in the electrical coupling between cells in the last days of pregnancy. The study is based on a mathematical model of excitable cells, coupled to each other on a regular lattice, and to a fluctuating number of passive cells, consistent with the known structure of the uterus. The two parameters of the model, the coupling between excitable cells, and between excitable and passive cells, grow during pregnancy.Using both a model based on measured electrophysiological properties, and a generic model of excitable cell, we demonstrate that spontaneous oscillations can appear when increasing the coupling coefficients, ultimately leading to coherent oscillations over the entire tissue. We study the transition towards a coherent regime, both numerically and semi-analytically, using the simple model of excitable cells. Last, we demonstrate that, the realistic model reproduces irregular action potential propagation patterns as well as the bursting behavior, observed in the in-vitro experiments.
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Borek, Bartlomiej. "Dynamics of heterogeneous excitable media with pacemakers." Thesis, McGill University, 2012. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=107795.
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The heart is a heterogeneous excitable tissue embedded with pacemakers. To understand the fundamental rules governing its behaviour it is useful to investigate the interplay between structure and dynamics in simplified experimental and mathematical models. This thesis examines FitzHugh-Nagumo type reaction-diffusion equation models motivated by experiments with engineered cardiac tissue culture. The aim is to relate how the design properties of these systems determine the underlying spatiotemporal dynamics. First, a functional relation between randomly distributed heterogeneities and conduction velocity is proposed in two dimensional heterogeneous excitable media. The transitions to wave break are studied for two types of heterogeneities related to fibroblasts and collagen deposits. The effects of pacemakers are next considered with a theoretical study of the transitions in one-dimensional wave patterns of a pacemaker reset by a stimulus pulse from a distance. Reflected wave solutions are found near the apparent discontinuity in the phase transition curve of the system, and they grow into more multi-reflected trajectories for a coarser spatial discretization of the model. Finally, the dynamical regimes arising from the interaction of two pacemakers in heterogeneous excitable media are investigated. A novel chick culture is developed to exhibit dominant pacemaker dynamics. This stable rhythm undergoes transitions to more complex reentrant patterns following induction of new pacemakers by the application of the potassium channel blocker, E-4031. The dynamics are reproduced by the FitzHugh-Nagumo model, which further demonstrates the effects of pacemaker size and heterogeneity density on the transition to wave break and reentry. These findings may contribute to our understanding of the generic mechanisms governing the dynamics of wave propagation through heterogeneous excitable media with pacemakers, including healthy and diseased hearts.Le coeur est un tissu hétérogène excitable qui contient des générateurs de rythme. Pour comprendre les règles fondamentales qui dirigent son comportement, il est utile d'étudier l'interaction entre la structure et la dynamique des modèles expérimentaux et mathématiques simplifiés. Dans cette thèse, j'utilise des modèles d'équations de FitzHugh-Nagumo. Ces modèles sont motivés par l'expérimentation avec des tissus cardiaques modifiés pour étudier comment les propriétés des conceptions influencent la dynamique d'ondes. Tout d'abord, une relation fonctionelle entre la densité des hétérogénéités distribuées au hasard et la vitesse de conduction est proposée dans un modèle numérique de deux dimensions de média hétérogènes excitables. Les transitions à l'onde rupturée sont différentes pour deux types de substrats hétérogènes. Les effets des régions automatiques sont alors considérés avec une étude théorique des transitions dans les ondes unidimensionelles des générateurs de rythme réinitialisés par une seule impulsion d'une distance. Des solutions d'ondes réfléchies se trouvent près de la discontinuité apparente de la courbe de transition de phase du système et deviennent des trajectoires plus complexes pour une discrétisation spatiale plus grossière du modèle. Enfin, les modèles d'ondes résultant de l'interaction de deux générateurs de rythme dans des médias hétérogènes excitables sont étudiés. Une nouvelle culture de tissu cardiaque de poussin est développée pour présenter la dynamique dominante déterminée par un générateur de rythme. Ce rythme stable subit des transitions à des modèles d'ondes réentrants plus complexes suivant l'induction de nouveaux générateurs de rythme, par l'application du bloqueur des canaux potassiques, E-4031. La dynamique est reproduite par le modèle FitzHugh-Nagumo, prévoyant l'effet de la taille du générateur de rythme et la densité de l'hétérogèneité sur la transition de l'onde rupturée et à la réentrée. Ces résultants contribuent à notre compréhension des mécanismes de média hétérogènes excitables avec des générateurs de rythme, dont les coeurs sains et malades.
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Dambal, Ajey Krishnamurty. "Polymer dynamics in confined and concentrated media /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Seebaluck, Ajay. "How social media affects the dynamics of protest." Thesis, Monterey, California: Naval Postgraduate School, 2014. http://hdl.handle.net/10945/44666.
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Approved for public release; distribution is unlimitedDigital technologies have created a new environment in the virtual world, which may either reinforce or undermine state authority. The wave of protests that erupted in the North African region during the last decade has increased the interest of scholars in investigating the catalysts for these uprisings. While there are conflicting views about the role of new technology in social protest, the Arab Spring has highlighted the role played by social media as a key tool in garner mass mobilization. However, a number of other factors could have been involved in the Arab uprisings. Thus, focusing only on one particular cause may lead to incorrect conclusions. Using cross-sectional-time series data, and multivariate regression, this thesis seeks to demonstrate that the Internet has a direct relationship with the onset of civil protests in Africa when certain economic conditions exist.
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Shokri-Kuehni, Salomé Michelle Sophie. "Dynamics of saline water evaporation from porous media." Thesis, University of Manchester, 2018. https://www.research.manchester.ac.uk/portal/en/theses/dynamics-of-saline-water-evaporation-from-porous-media(df48eec0-7bf4-46f5-96ef-d7f3f9419ec2).html.
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Saline water evaporation from porous media with the associated salt precipitation patterns is frequently observed in a number of industrial and environmental applications and it is important in a variety of topics including, but not limited to, water balance and land-atmosphere interaction, terrestrial ecosystem functioning, geological carbon storage, and preservation of historical monuments. The excess accumulation of salt in soil is a global problem and is one of the most widespread soil degradation processes. Thus, it is important to understand the dominant mechanisms controlling saline water evaporation from porous media. This process is controlled by the transport properties of the porous medium, the external conditions, and the properties of the evaporating fluid. During saline water evaporation from porous media, the capillary induced liquid flow transports the solute towards the evaporation surface while diffusive transport tends to spread the salt homogeneously thorough the porous medium. Therefore, the solute distribution is influenced by the competition between the diffusive and convective transport. As water evaporates, salt concentration in the pore space increases continually until it precipitates. The formation of precipitated salt adds to the complexity of the description of saline water evaporation from porous media. In this dissertation, the effects of salt concentration, type of salt, and the presence of precipitated salt, on the evaporation dynamics have been investigated. The obtained results show that the precipitated salt has a porous structure and it evolves as the drying progresses. The presence of porous precipitated salt at the surface causes top-supplied creeping of the evaporating solution, feeding the growth of subsequent crystals. This could be visualized by thermal imaging in the form of appearance and disappearance of cold-spots on the surface of the porous medium, brought about by preferential water evaporation through the salt crust. My results show that such a phenomenon influences the dynamics of saline water evaporation from porous media. Moreover, a simple but effective tool was developed in this dissertation capable of describing the effects of ambient temperature, relative humidity, type of salt and its concentration, on the evaporative fluxes. Additionally, pore-scale data obtained by synchrotron x-ray tomography was used to study ion transport during saline water evaporation from porous media in 4D (3D space + time). Using iodine K-edge dual energy imaging, the ion concentration at pore scale with a high temporal and spatial resolution could be quantified. This enabled us to reveal the mechanisms controlling solute transport during saline water evaporation from porous media and extend the corresponding physical understanding of this process. Within this context, the effects of particle size distribution on the dispersion coefficient were investigated together with the evolution of the dispersion coefficient as the evaporation process progresses. The results reported in this dissertation shed new insight on the physics of saline water evaporation from porous media and its complex dynamics. The results of this dissertation have been published in 3 peer-reviewed journal papers together with one additional manuscript which is currently under review.
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Munjiza, Ante. "Discrete elements in transient dynamics of fractured media." Thesis, Swansea University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.601150.
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A discrete element methodology capable of analysing a wide range of discrete materials, with the emphasis being placed on the dynamic behaviour of fracturing rock masses is presented. Standard problems that appear in any discrete element method are discussed as follows: a) contact detection and interaction among bodies in contact b) model of solid material a discrete element consists of Coordinate based space-cell decomposition, space searching using binary tree, direct evidence approach to contact detection and direct checking approach to contact detection have all been combined in a robust contact detection algorithm presented in the thesis. Interaction among bodies in contact is solved by introducing a concept of the contact element. Deformability is dealt with by discretisation of individual bodies into finite elements. Finite strain formulation using logarithmic stretches as a strain measure is considered in combination with an isotropic strain softening material. A fracture criterion based on isotropic strain softening assumptions is developed. Iso-h approach is applied to deal with mesh sensitivity. Finally an attempt to model rock blasting is made. A model that includes flow of the detonation gas through fracturing rock is presented. At the end some examples that illustrate possible applications of presented methodology in practical engineering problems are given. Some computational issues are discussed as well, including object oriented coding, unpredictibility and possible chaotic behaviour of systems with large number of bodies.
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Su, Chunmeizi. "Changing dynamics of digital entertainment media in China." Thesis, Queensland University of Technology, 2019. https://eprints.qut.edu.au/130744/1/Chunmeizi_Su_Thesis.pdf.
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This study is about the rise of Chinese technology companies and their integrated power in screen production culture. It examines the dynamics between BAT - Baidu, Alibaba and Tencent, the Chinese equivalent of Google, Facebook and Amazon, and the streaming services in China. This study adopted case studies to explore Chinese online productions via genres of TV, variety shows and user-generated content. In doing so, BAT is identified as the new digital power, and that they are reconfiguring power distributions of media industries in the content professionalising process.
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Wikström, Patrik. "Reluctantly Virtual : Modelling Copyright Industry Dynamics." Doctoral thesis, Karlstad University, Faculty of Economic Sciences, Communication and IT, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-478.
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During the evolution of the music industry, developments in the media environment have required music firms to adapt in order to survive. Changes in broadcast radio programming during the 1950s; the Compact Cassette during the 1970s; and the deregulation of media ownership during the 1990s are all examples of changes which have heavily affected the music industry. This study explores similar contemporary dynamics, examines how decision makers in the music industry perceive and make sense of the developments, and reveals how they revise their business strategies, based on their mental models of the media environment.
A qualitative system dynamics model is developed in order to support the reasoning brought forward by the study. The model is empirically grounded, but is also based on previous music industry research and a theoretical platform constituted by concepts from evolutionary economics and sociology of culture. The empirical data primarily consist of 36 personal interviews with decision makers in the American, British and Swedish music industrial ecosystems. The study argues that the model which is proposed, more effectively explains contemporary music industry dynamics than music industry models presented by previous research initiatives.
Supported by the model, the study is able to show how “new” media outlets make old music business models obsolete and challenge the industry’s traditional power structures. It is no longer possible to expose music at one outlet (usually broadcast radio) in the hope that it will lead to sales of the same music at another (e.g. a compact disc).
The study shows that many music industry decision makers still have not embraced the new logic, and have not yet challenged their traditional mental models of the media environment. Rather, they remain focused on preserving the pivotal role held by the CD and other physical distribution technologies.
Further, the study shows that while many music firms remain attached to the old models, other firms, primarily music publishers, have accepted the transformation, and have reluctantly recognised the realities of a virtualised environment.
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Rodriguez, Donaire Silvia. "Social media, interactive tools that change business model dynamics." Doctoral thesis, Universitat Politècnica de Catalunya, 2012. http://hdl.handle.net/10803/83599.
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The aim of this research is two-folded. On the one hand, it attempts to assist
employers of Catalan micro-retailers in designing, implementing and developing their
Social Media strategy as a complementary channel of communication. On the other
hand, it attempts to contribute to the research community with a better understanding
on both which building block of the micro-retailer¿s Business Model is more
influenced by the customer level of interaction by means of the Social Media and how
a transformation can be observed in the micro-retailers¿ Business Models as a result
of the Social Media implementation.
The research question to be answered in this paper is how the transformation of the
activity system of the micro-retailers¿ Business Model would allow the emergence of
a Participatory Business Model by means of Social Media. To carry out this research
the Participatory Action Research methodology was used, whose contribution has two
results: the one is more practitioner oriented and the other is more academic.
The incipient results of the research showed a scarce transformation of Catalan microretailer¿s
business model as a consequence of the implementation of social media.
However, it is significant enough to be considered as more than just a simple adoption
of an alternative channel of communication.
One of the main contributions is related to how customer influences the activity
system of the micro-retailer¿s business model beyond four levels of customer
interaction (communication, interaction, participation and collaboration) by means of
social media. On the one hand, the activity system of a business model is referred to
the eight building blocks of Osterwalder, Pigneur and Tucci (2005) research that
includes customer segment, customer relationship, distribution channel, capabilities,
partner, value configuration, value proposition, profit and cost. On the other hand, the
four defined levels of customer interaction are based on the literature of group
collaboration systems.
The results showed that not all the building blocks forming the business model are
influenced by consumer interaction. The only building blocks influenced by an initial
communication level in the current social media strategy implementation stage of our
sample (five micro-retailers) are the following: customer segment, customer
relationship, distribution channel, value proposition and cost. This incipient stage of
transformation can be justified by a lack of effort made due to the small size of the
business and a lack of team working inside the companies, easily adapting to changes.
It can also be justified by the fact it was carried out by the micro-retailers only during
a short period of time (14 month).
Another contribution of the paper shows that Social Media transformation drives a
BM innovation according to the following mediator elements: (1) the dynamic
capabilities, (2) the ability of learning, (3) the dedicated effort, (4) the implementation
time and (5) the level of customer participation.
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Soneson, Joshua Eric. "Optical Pulse Dynamics in Nonlinear and Resonant Nanocomposite Media." Diss., Tucson, Arizona : University of Arizona, 2005. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu%5Fetd%5F1274%5F1%5Fm.pdf&type=application/pdf.
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Page, Adam Freddie. "Surface plasmon emission and dynamics in active planar media." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/30760.
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By reducing the number of dimensions that light can propagate in from three to two, control over the properties of propagation can be achieved. The plasmonic modes of planar metal-dielectric heterostructures will confine light in one dimension, enhancing the electromagnetic fields within the structure. This thesis focuses on two particular aspects of active nanoplasmonics in planar systems, stopped light lasing and plasmons with gain in nonequilibrium graphene. For stopped-light lasing, a plasmonic waveguide mode is designed to have two points of zero group velocity in a narrow frequency range, in order to increase the local density of optical states that a gain medium can emit into. The two stopped light points form a band of slow light that supports a wide range of wavevectors, allowing localisation over a sub-wavelength gain medium and providing the feedback required for lasing. This results in a new type of laser that does not rely on predefined cavity modes, in fact is cavity-free in 2D, dynamically forming its lasing mode about a locally pumped region of carrier inversion. Graphene, a single-atom thick semimetal, provides the ultimate miniaturisation as a truly 2D material. It is shown that graphene can support plasmons with gain, under realistic conditions of collision loss, temperature, doping, and carrier relaxation via amplified spontaneous emission. This is made possible by developing a scheme to evaluate polarisabilities for nonequilibrium carrier distributions, allowing the calculation of the exact RPA complex-frequency plasmon dispersion solutions. The rates of spontaneous emission are calculated and are critically dependant on the exact dispersion relation. The instantaneous rates are found to be 5 times faster than previously reported and, when coupled with phonons, lead to carrier relaxations on 100 fs timescales. The polarisability and relaxation rates must form the basis of any active graphene device, where electromagnetic energy is coupled to an evolving electronic system.
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Irwin, Matthew L. "The Dynamics of Media Use, Attention, and Behavioral Control." The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492700316011036.
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Little, Sylvia Bandy. "Multiphase flow through porous media." Thesis, Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/11779.
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Sailer, Franz-Xaver. "Controlling excitable media with noise." Doctoral thesis, [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=980114284.
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Tartakovsky, Daniel. "Prediction of transient flow in random porous media by conditional moments." Diss., The University of Arizona, 1996. http://etd.library.arizona.edu/etd/GetFileServlet?file=file:///data1/pdf/etd/azu_e9791_1996_263_sip1_w.pdf&type=application/pdf.
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Russian, Anna. "Anomalous dynamics of Darcy flow and diffusion through heterogeneous media." Doctoral thesis, Universitat Politècnica de Catalunya, 2013. http://hdl.handle.net/10803/116499.
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This thesis studies diffusion phenomena in heterogeneous media, which includes Darcy flow and diffusive solute transport in geological media. Natural media are heterogeneous at different scales, which induces complexity in diffusion phenomena. The work is centered on the integration of the effects of heterogeneity on Darcy flow and solute diffusion into large scale models.
The quantification of the effects of heterogeneity in diffusion phenomena is highly important for a large number of problems such as diffusion and reaction of chemicals and radionuclides in low permeability media, which is essential in subsurface hazardous waste storage problems, CO2 sequestration performance and groundwater management.
In a stochastic framework we quantify the effects of heterogeneity in large scale models considering two interrelated strategies that can be called Ôcoefficient approachÕ, which deals with the derivation of effective coefficients to insert in equivalent homogeneous models, and Ôdynamic approachÕ, which deals with the upscaling of the local scale equations and the derivation of large scale formulations which can differ from their local counterparts. Whenever a diffusion process cannot be described in terms of effective coefficient, that behaviour is named anomalous or non-Fickian.
Anomalous diffusion behaviours observed experimentally are frequently modelled by effective theories such as fractional diffusion equations, continuous time random walks. One limitation of these models is that often they are rather phenomenological and the relation to the local scale heterogeneity and dynamics may not be clear. In the dynamic approach we derive large scale descriptions that can explain anomalous behaviour and link it with a description of the local scale medium heterogeneity. To this end, we upscale the local scale governing equations using different methods depending on the type of medium heterogeneity.
For moderately heterogeneous media we upscale flow equation by stochastic averaging. Starting from the classical flow equation at local scale determined by Darcy's law, we derive an upscaled non-local effective formulation. The non-local effective formulation is compared with its local counterpart by considering the head response for a pulse injection.
Numerically, we solve flow and diffusion in heterogeneous media using particle tracking methods. While classical random walk particle tracking is an efficient numerical tool to solve for diffusion problems in moderately heterogeneous media, strong medium contrasts, as encountered in fractured media, render this method inefficient. For highly heterogeneous media efficiency of classical random walk can be increased by the use of the time domain random walk (TDRW) method. We rigorously derive the equivalence of the TDRW algorithm and the diffusion equation and we extend the classical TDRW method to solve diffusion problem in a heterogeneous medium with multi-rate mass transfer properties. Moreover we use the TDRW method in connection with a stochastic model for the heterogeneity in order to upscale heterogeneous diffusion processes. For a certain class of heterogeneity, the upscaled dynamics obey a CTRW.
Analytically we upscale diffusion in highly heterogeneous media by using a multicontinuum representation of the media. Using volume and ensemble averaging we derive a multicontinuum model that can explain anomalous diffusion behavior and link it with a suitable local scale description of the medium heterogeneity.
Finally, we integrate the multicontinuum model derived in the context of aquifer modelling. We derive a multicontinuum catchment model that can explain anomalous behavior observed in the aquifer dynamics at basin scale. We identify the physical mechanisms that induce anomalous behaviour and we determine the time scales that control its temporal evolution.
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Vallabh, Rahul. "Modeling Tortuosity in Fibrous Porous Media using Computational Fluid Dynamics." NCSU, 2009. http://www.lib.ncsu.edu/theses/available/etd-08062009-153236/.
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Tortuosity factor is often used to characterize the structure of the pore volume in fibrous porous media. This work involves the determination of tortuosity using computational fluid dynamic (CFD) simulation and particle tracking analysis. A new method has been adopted to generate 3-D geometry for modeling fibrous porous structures using ANSYS® Parametric Design Language (APDL). Computation fluid dynamics has been used to simulate permeability of modeled 3-D fiberweb structures. The simulated permeability results are in good agreement with the models proposed by other authors. The experimental results were found to be slightly higher compared to simulated results and existing models due to the layered configuration of the samples. Permeability is found to be significantly influenced by fiber diameter, and porosity as well as fiberweb thickness. The relationship between air permeability and fiberweb thickness has been used to develop an indirect method for determination of tortuosity factor. Tortuosity factor has also been determined using a more direct method involving CFD simulation and Particle Tracking analysis. Different models established using the direct and indirect methods of determination show that tortuosity is significantly influenced by porosity, fiber diameter and fiberweb thickness, whereas the models available in the literature express tortuosity as a function of porosity only.
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Parra, Martinez Juan Pablo. "On multilayered system dynamics and waves in anisotropic poroelastic media." Doctoral thesis, KTH, VinnExcellence Center for ECO2 Vehicle design, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-195801.
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The mechanical and acoustic anisotropy of media is a governing factor in the behaviour of multilayered systems including such media. The understanding of the mechanisms conditioning the dynamic behaviour of multilayered systems is of paramount importance. In particular, the intrinsic anisotropy of poroelastic media presents a potential for the optimal design of systems for multifunctional performances. Indeed, these multilayered systems are bound by stiffness, thermal and acoustic performance constraints in simultaneously. A plane wave method is presented to study the influence of material orientation in the dynamic behaviour of multilayered systems composed of anisotropic poroelastic media. The method is applied to a system composed of an anisotropic open-celled melamine foam core in between two metal sheets. This particular multilayered configuration allows to shed light on phenomena intrinsic to layers composed of anisotropic poroelastic materials, such as the frequency shift of the fundamental resonance of the panel, or the compression-shear coupling effects taking place in the poroelastic core layers. The latter phenomena is of particular importance, as it is evidenced on the unconventional polarisation of waves in anisotropic poroelastic media. Finally, the method is adapted to the optimisation of multilayered systems for acoustic performance. the design variables are consequently the core material orientations with respect to the global coordinate system. The solutions to the optimisation problem are analysed in terms of dynamic behaviour, thus allowing to correlate acoustic performance of the overall structure, and the response of each individual layer.QC 20161110
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Stevar, M. S. P. "Dissolution dynamics of liquid/liquid binary mixtures in porous media." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/349974/.
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In this project has been undertaken an experimental study aimed at understanding the dissolution dynamics of binary mixtures within porous media. The porous medium can be roughly represented as a network of capillary tubes. This allowed for the initial research to be focused on understanding the dissolution dynamics of binary mixtures (i.e. glycerol/water, soybean oil/hexane, and isobutyric acid/water) within single capillary tubes. Further, the dissolution process was investigated within a 2D micromodel built as a network of capillary tubes. In the experiments with the capillary tubes, the dissolution (i.e. the interfacial mass transfer) could be isolated from the hydrodynamic motion while using glycerol/water and soybean oil/hexane binary mixtures. Despite the fact that these are fully miscible liquids, the interface could be observed for rather long time periods. In particular, two phase boundaries were observed moving from the ends into the middle section of the capillary tube with the speeds v∼D^1/3t^-2/3d^2(D, t and d are the coefficient of diffusion, time and diameter of the capillary tube, respectively). The boundaries slowly smeared but their smearing occurred very slow in comparison to their motion. The motion of the phase boundaries cannot be explained by the dependency of the diffusion coefficient on concentration, and could possibly be explained by the effect of barodiffusion. In addition, these solute/solvent boundaries were endowed with non-zero interfacial tension. This experimental study also revealed that the solvent penetration into the micromodel is diffusion-dominated for completely miscible binary mixtures. This is however non-Fickian diffusion with the dissolution rate dV/dt∼D^1/3t^-0.4 for almost the entire duration of the experiment (V is the volume occupied by the solvent, D is the diffusion coefficient and t is time). For the IBA/water mixture the experiments performed at undercritical temperatures revealed that the diffusive mass transport was negligible despite the mixture being out of its thermodynamic equilibrium. Despite a seeming simplicity of the experiments, to the author’s best knowledge, there is no theory that could correctly describe the observed diffusional penetration of a solvent into a solute-filled capillary tube and hence, into a more complex porous volume.
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Hohenberger, Matthias. "The dynamics of strong laser-driven shocks in cluster media." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/5642.
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Shocks and blast waves are ubiquitous features observed in plasma physics and in astrophysical phenomena and, as such, have long been the subject of experimental and theoretical studies. This thesis describes experimental and numerical investigations of the dynamics of laser driven shocks in cluster media. Target gases of atomic clusters have been shown to exhibit e cient absorption of high-intensity laser radiation, allowing to use `table-top' scale laser systems to drive high Mach-number shock waves. By applying hydrodynamic scaling laws, these systems can provide insight into the physics governing much larger astrophysical phenomena, such as supernova remnants. Experiments were conducted to investigate the structure and propagation dynamics of cylindrical blast waves in radiative and non-radiative gases. Shock pro ling studies performed at Imperial College London are presented, that highlight the need for non-LTE calculations of the shock physics. Investigations into the onset of the radiation driven thermal cooling instability (TCI) were performed by means of a streaked Schlieren technique, developed to obtain single-shot shock trajectory measurements, while removing any ambiguities imposed by shot-to-shot uctuations. In order to scale previous results to higher drive energies, experiments were performed using the Vulcan laser facility at the Rutherford Appleton Laboratory. The resulting cluster absorption and shocked gas comparison data is discussed in detail, including data indicating the rst experimental observation of TCI. To study shock collisions, a unique focal geometry has been employed, creating two near-parallel cylindrical shocks. By means of an interferometric tomography technique, the full 3D electron density pro le was reconstructed, showing complex material transport and Mach stem formation at the oblique shock collision interface, con rmed by 3D hydrodynamics simulations. To investigate this feature further, shock interactions with an obstruction were also performed, showing interesting propagation features through density steps imposed by the obstruction in the cold gas stream.
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Yeates, Christopher. "Multi-Scale Study of Foam Flow Dynamics in Porous Media." Thesis, Sorbonne université, 2019. http://www.theses.fr/2019SORUS023/document.
Full textAbstract:
Pour ce travail, nous utilisons un micromodèle à haute complexité et à structure fixe pour faire une série d’expériences en variant la vitesse d’injection, la qualité de la mousse, les distributions de taille de bulles d’injection, et la méthode d’injection. Nous mettons en œuvre un suivi individuel de bulles pour associer les propriétés d’écoulement aux propriétés de taille de bulles ainsi que les caractéristiques structurelles du milieu poreux. Nous proposons de nouveaux outils pour décrire l’écoulement d’un point de vue global et local de différentes manières. Nous établissons des comportements spécifiques à chaque taille de bulle, en montrant que les bulles des mousses piégées sont plus probables d’être de taille inférieure aux tailles de bulles moyennes, alors que les mousses en mouvement accèdent elles-mêmes à différents chemins d’écoulement selon les tailles de bulles. Les bulles plus volumineuses s’écoulent en majorité dans des chemins préférentiels à haute vitesse, généralement parallèles au gradient de pression, mais les petites bulles sont transportées en supplément à l’intérieur de chemins transversaux liant les chemins préférentiels. Ailleurs, pour nos données nous démontrons l’importance supérieure de la fraction de mousse piégée vis-à-vis de la densité de bulles quant à l’explication microscopique de la viscosité apparente, malgré une contribution des deux. Nous caractérisons structurellement les zones piégées à répétition, comme étant soit des zones à faible coordination de pore, de faible taille de seuil d’entrée, d’orientation de seuil désavantageuse, ou une combinaison de ceux-ci. Les zones à fort écoulement échappent à une caractérisation en termes de paramètres de structure locale et nécessitent une considération de l’information des différents chemins traversant la totalité du modèle. À ce but, afin de décrire les zones à fort écoulement, nous développons un modèle générant des chemins, utilisant une représentation en graphe du milieux poreux, basé sur une décomposition initiale en pores et seuils, qui intègre seulement les notions de taille de seuil et d’orientation de seuil relatif au gradient de pression pour caractériser les cheminsIn this work, we use of a high-complexity micromodel of fixed structure on which we perform a series of experiments with varying injection rates, foam qualities, inlet bubble size distributions and injection methods. We perform individual bubble tracking and associate flow properties with bubble size properties and structural characteristics of the medium. We propose new tools describing the local and global flow in different ways. We establish specific behaviors for different bubble sizes, demonstrating that trapped foams are more likely to have smaller than average bubble sizes, while flowing bubbles also tend to segregate in different flow paths according to bubble size. Larger bubbles tend to flow in high-velocity preferential paths that are generally more aligned with pressure gradient, but smaller bubbles tend to access in supplement transversal paths linking the different preferential paths. Furthermore, for our data we establish the pre-eminence of the trapped foam fraction over bubble density within the microscopic explanation of apparent viscosity, although both contribute to some degree. We structurally characterize consistently trapped zones as areas with either low pore coordination, low entrance throat size, unfavorable throat orientation or a combination thereof. High-flow zones however cannot be characterized in terms of local structural parameters and necessitate integration of complete path information from the entire model. In this regard, in order to capture the high-flow zones, we develop a path-proposing model that makes use of a graph representation of the model, from an initial decomposition into pores and throats, that uses only local throat size and throat orientation relative to pressure gradient to characterize paths
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Soroka, Stuart Neil. "Agenda-setting dynamics in Canada." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://hdl.handle.net/2429/11201.
Full textAbstract:
Agenda-setting hypotheses inform political communications studies of media influence
(public agenda-setting), as well as examinations of the policymaking process (policy agenda-setting).
In both cases, studies concentrate on the salience of issues on actors' agendas, and
the dynamic process through which these agendas change and effect each other. The results,
narrowly conceived, offer a means of observing media effects or the policy process. Broadly
conceived, agenda-setting analyses speak to the nature of relationships between major actors
in a political system.
This study differs from most past agenda-setting research in several ways. First, this project
draws together public and policy agenda-setting work to build a more comprehensive model
of the expanded agenda-setting process. Secondly, the modeling makes no assumptions
about the directions of causal influence - econometric methods are used to establish
causality, allowing for a more nuanced and accurate model of issue dynamics.
Quantitative evidence is derived from a longitudinal dataset (1985-1995) including the
following: a content analysis of Canadian newspapers (media agenda), 'most important
problem' results from all available commercial polls (public agenda), and measures of
attention to issues in Question Period, committees, Throne Speeches, government spending,
and legislative initiatives (policy agenda). Data is collected for eight issues: AIDS, crime,
debt/deficit, environment, inflation, national unity, taxation, and unemployment. The present
study, then, is well situated to add unique information to several ongoing debates in agenda-setting
studies, and provide a bird's eye view of the media-public-policy dynamics in
Canadian politics.
Many hypotheses are introduced and tested. Major findings include: (1) there is a Canadian
national media agenda; (2) the salience of issues tends to rise and fall simultaneously across
Canada, although regional variation exists based on audience attributes and issue
obtrusiveness; (3) there is no adequate single measure of the policy agenda - government
attention to issues must be measured at several points, and these tend to be only loosely
related; (4) the agenda-setting dynamics of individual issues are directly and systematically
related to attributes such as prominence and duration; (5) Canadian media and public agendas
can be affected by the US media agenda.
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Whelan, Michael P. "Dissolution of non-aqueous phase liquid pools in saturated porous media." Thesis, Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20140.
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Momken, Bahareh. "Fluid flow and deformation in composite porous media /." Full text (PDF) from UMI/Dissertation Abstracts International, 2000. http://wwwlib.umi.com/cr/utexas/fullcit?p3004343.
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Ribeiro, Andre Figueiredo. "Graph dynamics : learning and representation." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34184.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2006.Includes bibliographical references (p. 58-60).
Graphs are often used in artificial intelligence as means for symbolic knowledge representation. A graph is nothing more than a collection of symbols connected to each other in some fashion. For example, in computer vision a graph with five nodes and some edges can represent a table - where nodes correspond to particular shape descriptors for legs and a top, and edges to particular spatial relations. As a framework for representation, graphs invite us to simplify and view the world as objects of pure structure whose properties are fixed in time, while the phenomena they are supposed to model are actually often changing. A node alone cannot represent a table leg, for example, because a table leg is not one structure (it can have many different shapes, colors, or it can be seen in many different settings, lighting conditions, etc.) Theories of knowledge representation have in general concentrated on the stability of symbols - on the fact that people often use properties that remain unchanged across different contexts to represent an object (in vision, these properties are called invariants). However, on closer inspection, objects are variable as well as stable. How are we to understand such problems? How is that assembling a large collection of changing components into a system results in something that is an altogether stable collection of parts?
(cont.) The work here presents one approach that we came to encompass by the phrase "graph dynamics". Roughly speaking, dynamical systems are systems with states that evolve over time according to some lawful "motion". In graph dynamics, states are graphical structures, corresponding to different hypothesis for representation, and motion is the correction or repair of an antecedent structure. The adapted structure is an end product on a path of test and repair. In this way, a graph is not an exact record of the environment but a malleable construct that is gradually tightened to fit the form it is to reproduce. In particular, we explore the concept of attractors for the graph dynamical system. In dynamical systems theory, attractor states are states into which the system settles with the passage of time, and in graph dynamics they correspond to graphical states with many repairs (states that can cope with many different contingencies). In parallel with introducing the basic mathematical framework for graph dynamics, we define a game for its control, its attractor states and a method to find the attractors. From these insights, we work out two new algorithms, one for Bayesian network discovery and one for active learning, which in combination we use to undertake the object recognition problem in computer vision. To conclude, we report competitive results in standard and custom-made object recognition datasets.
by Andre Figueiredo Ribeiro.
S.M.
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Mantel, Rolf-Martin. "Periodic forcing and symmetry breaking of waves in excitable media." Thesis, University of Warwick, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.263610.
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Bordyugov, Grigory. "Dynamics and stability of pulses and pulse trains in excitable media." [S.l.] : [s.n.], 2006. http://deposit.ddb.de/cgi-bin/dokserv?idn=981984177.
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Lai, Zhong Yuan [Verfasser]. "Wave dynamics in random, absorptive or laseractive media / Zhong Yuan Lai." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1127666320/34.
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Robb-Smith, Tyler. "Electric filed induced rotational dynamics of carbon nanotubes in viscous media." Thesis, Queen Mary, University of London, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.538670.
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Tränkle, Marion. "Material agency and performative dynamics in the practices of media art." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/8767.
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This dissertation identifies a strategy of artistic inquiry within contemporary media art practice. It applies the concept of material that acts in an agential capacity, generating performative acts. It argues that the emergent potentials of materials and their interconnectedness with the compositional layers of a work can facilitate modes of effecting change in the artistic system. Through the theoretical investigation of the production processes of physical structures and environments, the thesis focuses on the compositional dynamics within which materials actively perform. It examines how Lars Spuybroek’s architectural design method of Material Machines (2004), and both the tactile potential as well as tactical uses of materials as generators to the formtaking process, might describe an open and active artistic strategy for employing the experimental capacities of such materialization processes. Building on philosophical and conceptual arguments that trace concepts of agency (Bruno Latour’s Actant-Network theory) and enactment (Karen Barad’s concept of intra-acting), the thesis introduces the two installation works ANI_MATE (described as a performative pneumatic stage machine) and ON TRACK (described as a mechanic-robotic installation). These apply the introduced artistic strategies. The analyses of these two artworks traces the particular capacities of the materials involved (respectively, their elasticity or viscosity) to negotiate forces of physical movement, which effect the system to transiently or irreversibly transform. ANI_MATE is a machine that is artist-operated and that explores the relationship between liveanimation procedures and the transformability and flexibility of its material environment. In contrast, ON TRACK’s performative machine ecology removes human agency. The machines act autonomously, giving rise to chance in the artistic system and allowing agency to emerge from the dynamic interconnectivity between materials, parts, and processes, eventually producing an entropic scenario of spilling resources. The thesis concludes that, in the context of a post digital paradigm in-development, such artistic practice offers a new strategy for an emergent aesthetics within contemporary physical-digital performance.
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Chen, Xi. "The Dynamics of Chinese Media Practices and Regulation: Explanations and Interpretations." Diss., Virginia Tech, 2007. http://hdl.handle.net/10919/30035.
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Based on the understanding that a countryâ s media system can provide important insights into its politics, this dissertation reexamines the development of Chinese politics in the reform era through the media lens, and television in particular. Given that Chinese media have been a marker of the nationâ s socio-political developments, the media perspective is believed to be particularly useful in interpreting Chinaâ s changing political circumstances. By tracing the dynamics of television news reporting practices and government regulation of the news media, this analysis will map out the evolving roles of television in todayâ s China to use them as subtle indications of how Chinese politics are evolving in the reform era. Chinese television adopted a Soviet TASS style from its very beginnings due to the heavy Soviet influence that placed an emphasis on imparting a heavily ideological messages and propagating government policies and rules. This practice, however, has been substantially changed during the reform era. Television news reporting in todayâ s China is moving towards the liberal media style in both format and content. What specific changes have taken places in television industry? To what extent has Chinese media departed from the Soviet style? What are the implications of these media changes for Chinaâ s politics? To answer these questions, I conducted content analysis of the China Radio and Television Broadcasting Awards news reports and television regulations in the reform era, which revealed that Chinese media was developing towards a hybrid of Soviet and liberal models in which both control and liberalization trends can be identified. While encouraging and authorizing increased managerial, editorial, and programming freedom and autonomy, the Party-State has managed to retain its control over political content through increasingly indirect and sophisticated means. The continued marginalization of alternative political voices confirms that democracy with political pluralism, free flow of information and rule of law has not yet materialized after more than two decadesâ economic reform. By collaborating with market and technology, the Communist Party of China has actually managed to consolidate its control over both the political and economic power while authorizing increased freedom in individual, cultural, and social domains.Ph. D.
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Mattea, Carlos. "Molecular dynamics in porous media studied by Nuclear Magnetic Resonance techniques." [S.l. : s.n.], 2006. http://nbn-resolving.de/urn:nbn:de:bsz:289-vts-55830.
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Newlon, Scott. "INTRUDER DYNAMICS RESPONSE OF GRANULAR MEDIA WITH NON-LINEAR INTERACTION POTENTIALS." OpenSIUC, 2017. https://opensiuc.lib.siu.edu/theses/2252.
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An investigation into the intruder dynamics of dry dimensionless, frictionless discs in bidispersed, disordered systems is carried out using computer simulations. The velocity of an intruder particle driven under constant force is used as a tool to determine scaling of velocity as a function of packing pressure. Using these velocity for a range of pressures, $4 \times 10^{-7}\leq P \leq 4 \times 10^{-2}$. A universal scaling relation is proposed and plotted. The force required to cause the packing to yield to the driven intruder is determined and plotted as function of pressure. Power law exponents were extracted for the yielding force vs. the pressure. The extracted values were used to study the micro-rheology of the intruder particle. Grain scale characteristics are used to infer global elastic modulus properties.
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Hamisi, Rajabu. "Modelling phosphorus dynamics in constructed wetlands upgraded with reactive filter media." Licentiate thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-207613.
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Developing low-cost and effective technologies to upgrade phosphorus (P) removal from the catchment runoffs and rural wastewater treatment facilities is one of the main research agendas to save the Baltic Sea from eutrophication. In Sweden, the construction of the constructed wetlands has been one of the environmental objectives for wastewater quality improvement in the small communities. However, the insufficiently understanding of the mechanisms underlying the process of phosphorus mobility and sorption in the constructed wetlands has limited design of the effective constructed wetlands. To provide the better understanding of sorption process in the catchment and constructed wetland system, this thesis used the GIS-based Soil and Water Assessment Tool (SWAT) to predict phosphorus mobility and identify the critical diffusing sources of phosphorus loss in the Oxunda catchment (Paper I). Then, the study developed the three-dimensional numerical Reactive TRAnsPort Model (RETRAP - 3D) in the COMSOL Multiphysics® for evaluating the long - term sorption processes and removal efficiencies of the porous reactive media for upgrading the performance of constructed wetlands (Paper II and III). The latter model coupled many physics equations to solve process of water flow, reaction kinetics and solute transport in the porous reactive adsorbent media for application in the constructed wetlands. The data from the field measurements and column experiments have been used to demonstrate the model simulation accuracy to capture the process of phosphorus sorption in the real environment. Modeling results ranked the phosphorus removal efficiency of the adsorbent media as follows: Polonite® (88 %), Filtralite P® (85%), BFS (62%), Wollastonite (57 %). The satisfactory agreement which obtained between the simulated outputs and measured data confirmed that the SWAT and RETRAP-3D are useful tools for describing various processes in the complicated system. However, further study is required to generate and validate more experimental data to evaluate the sensitivity of local parameters.This reserch project was finacially supported by Lars Erik Lundberg scholarship foundation for projectnumber (2015/34 and 2016/12), ÅkeochGreta Lissheds Stiftelsen for project number (2015-00026), J.Gust. Richert Stiftelsen and Ecopool researchproject for smart and sustainable environment. QC 20170523
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Moon, Miri. "Journalistic challenges and international news dynamics in the Korean peninsula." Thesis, Brunel University, 2015. http://bura.brunel.ac.uk/handle/2438/11221.
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This thesis explores national and international news reporting of a major controversial news story – the sinking of South Korean corvette, Cheonan in March 2010. The thesis draws upon a comparative analysis of major news coverage pertaining to the incident with a sample of US/UK and South Korean media (AP, CNN, The New York Times, BBC, The Guardian, Yonhap,The Hankyoreh Shinmun, The DongA Ilbo). In addition 18 semi-structured interviews with foreign correspondents and Korean journalists were conducted in order to explore news gathering practices concerning the incident and to investigate factors that influence news production. There has been a growing debate that a paradigm shift in journalism theory is necessary in the post-Cold War era. This study examines how a new paradigm shift might be applicable in the case of North Korea. This study also addresses international news flow and explores the propaganda model by Herman and Chomsky (2002) in light of media influence in foreign policy. Specifically, this study attempts to investigate the applicability of some filters in the propaganda model in the context of the North and South Korea’s conflict coverage, concentrating on the use of news sources and the impact of new media on journalism practices. This is contextualised by addressing journalistic challenges of covering South and North Korean conflicts. Key findings are that the dominant news frames identified were conflict frames in international news media and human interest frame in national news respectively. The primary factor that influenced journalism practices at a national and an international level include a journalist’s ideology - one of the most significant factors in news framing. Moreover, a routinized journalism practice, and inaccessibility to North Korea that entailed limited news sources also influenced the ways in which news relating to the Cheonan incident was reported. Some filters of the propaganda model, which are routinized news sources relying on officials and ideological convergence such as anti-communism were operationalised in the case of the Cheonan. The international news agencies also played a pivotal role as primary definer and seemed to influence national and international mainstream media. Correspondents perceived that the Korean news media’s ideological cleavage hampered Korean social integration. On a global scale, South Korea’s security is under the influence of geopolitical power control with peripheral countries. Given the impact of newsmaking on society and policy making, this study highlights that investigative journalism practices based on gathering ‘facts’ and the personal ethics of journalists themselves are indispensable.
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Long, Jacob Andrew. "Time Dynamics and Stability of Political Identity and Political Communication." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1595519865595447.
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Budu, Paula. "Conditional and unconditional nonlinear stability in fluid dynamics." Thesis, Durham University, 2002. http://etheses.dur.ac.uk/3938/.
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In this thesis we examine some of the interesting aspects of stability for some convection problems. Specifically, the first part of the thesis deals with the Bénard problem for various Non-Newtonian fluids, whereas the second part develops a stability analysis for convection in a porous medium. The work on stability for viscoelastic fluids includes nonlinear stability analyses for the second grade fluid, the generalised second grade fluid, the fluid of dipolar type and the fluid of third grade. It is worth remarking that throughout the work the viscosity is supposed to be any given function of temperature, with the first derivative bounded above by a positive constant. The connection between the two parts of the thesis is made through the method used to approach the nonlinear stability analysis, namely the energy method. It is shown in the introductory chapter how this method works and what are its advantages over the linear analysis. Nonlinear stability results established in both Part I and Part II are the best one can get for the considered physical situations. Different choices of energy have been considered in order to achieve conditional or unconditional nonlinear stability results.
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Seale, Michael David. "Propagation of guided acoustic waves in composite media." W&M ScholarWorks, 1996. https://scholarworks.wm.edu/etd/1539623884.
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Composite materials are being more widely used today by aerospace, automotive, and a number of other commercial industries because of their advantages over conventional metals. Composites are finding applications ranging from bicycle frames to the proposed High-Speed Civil Transport (HSCT). Determining the response to a variety of damage mechanisms is necessary for a complete understanding of the total use environment of composite structures. The objective of the research presented here is to provide a method of quantifying the amount of damage in composite materials for a number of different damage scenarios. Components which have non-visible damage, but have degraded performance, are of interest. at this level of damage, the safety margin designed into the structure may be compromised.;Nondestructive Evaluation (NDE) is a field of measurement physics where energy is imparted to a material and information is obtained from observing how the energy interacts with the system. Many different forms of energy can be used to obtain useful information from these measurements: acoustic, thermal, x-ray, optical, and electromagnetic. Among the many various techniques available, ultrasonic Lamb waves offer a convenient method of evaluating these composite materials. as a material is damaged, the elastic parameters of the structure change. Since the Lamb wave velocity depends on these properties, an effective tool exists to monitor damage in composites by measuring the velocity of these waves. Additionally, Lamb wave measurements are beneficial because they can propagate over long distances and are sensitive to the desired in-plane elastic properties of the material.;Presented in this study are the results involving the investigation of a variety of damage mechanisms (fatigue, thermal, and thermal-mechanical) using the Lamb wave technique. Two fatigue studies were conducted which showed that the change in modulus and change in velocity of the Lamb wave squared follow the same general trend. The Lamb wave velocity was also observed to decrease with increasing crack density. For the thermal damage study, the results showed that the velocity of the lowest order symmetric Lamb mode dropped significantly for extended thermal damage. When the experimental results were compared to model calculations, good agreement was observed for both fatigue and thermal damage. Finally, for thermal-mechanical damage, it was found that the Lamb wave technique was also able to predict a local defect in a specimen, which was later found to have a large delamination zone.;The Lamb wave velocity is a quantitative measurement and it has been shown by this work to be an effective tool in monitoring different types of damage in composites. Since the Lamb wave velocity depends on a variety of material properties, an ideal technique exists to monitor composites as damage is incurred. With the continued development of damage assessment techniques such as the Lamb wave method, the safety of such structures can be assured.
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Kampel, Guido. "Mathematical modeling of fines migration and clogging in porous media." Atlanta, Ga. : Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/19764.
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Thesis (Ph.D)--Mathematics, Georgia Institute of Technology, 2008.Committee Chair: Goldsztein, Guillermo; Committee Member: Dieci, Luca; Committee Member: McCuan, John; Committee Member: Santamarina, Juan; Committee Member: Zhou, Haomin.
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Lederman, Oren. "Hacking innovation - group dynamics in innovation teams." Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/101790.
Full textAbstract:
Thesis: S.M., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2015.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 95-101).
Innovative work is gradually shifting towards collaborative efforts by larger, multidisciplinary teams, making team efficacy an increasingly important field of study. Researchers in this field have mainly focused on laboratory experiments, which may not fully capture the complex situations that teams encounter in real life. The alternative, field studies, are difficult to maintain and often require significant time to produce results. In this thesis we propose a methodology that bridges the gap between these two settings -- the laboratory and the field. By combining a new, affordable electronic badge that captures vocalization data with an innovative setting -- the Hackathon -- we create a new environment for studying team performance. This methodology reduces the duration and maintenance burden of such studies, and offers new opportunities for examining the effects of interventions on teamwork. The preliminary results from our studies show a variety of individual and team behaviors that can be captured in Hackathons using badges, such as participation, the parity of contribution to group discussions, the level of turn taking, and the frequency and duration of meetings. In a Hackathon, we measure these behaviors throughout the entire life cycle of each team, observe how they change in response to different shocks, and study how well the team members collaborate and perform as a team.
by Oren Lederman.
S.M.
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Robbel, Philipp. "Exploiting object dynamics for recognition and control." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/41752.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2007.Includes bibliographical references (p. 127-132).
This thesis explores how state-of-the-art object recognition methods can benefit from integrating information across multiple observations of an object. Considered are active vision systems that allow to steer the camera along predetermined trajectories, resulting in sweeps of ordered views of an object. For systems of this kind, a solution is presented that exploits the order relationship between successive frames to derive a classifier based on the characteristic motion of local features across the sweep. It is shown that this motion model reveals structural information about the object that can be exploited for recognition. The main contribution of this thesis is a recognition system that extends invariant local features (shape context) into the time domain by adding the mentioned feature motion model into a joint classifier. Second, an entropy-based view selection scheme is presented that allows the vision system to skip ahead to highly discriminative viewing positions. Using two datasets, one standard (ETH-80) and one collected from our robot head, both feature motion and active view selection extensions are shown to achieve a higher-quality hypothesis about the presented object quicker than a baseline system treating object views as an unordered stream of images.
by Philipp Robbel.
S.M.
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Post, E. Rehmi 1966. "Inertial measurement via dynamics of trapped particles." Thesis, Massachusetts Institute of Technology, 2003. http://hdl.handle.net/1721.1/29991.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2003.Includes bibliographical references (leaves 69-70).
We describe theoretical and practical aspects of the particle trap as an inertial sensor. The insight motivating this approach is that a trapped particle acts like a mass on a spring, but the restoring forces are provided by electrostatic fields. Exquisitely machined physical mechanisms can be replaced by carefully tuned mechanical physics. Such inertial sensors could be simpler to build yet exhibit superior performance because their operating parameters can be dynamically controlled. Most currently available inertial sensors are inherently planar devices that obtain no more than two degrees of motional sensitivity from a given proof mass. The availability of an accurate, inexpensive, integrated six-degree-of-freedom inertial sensor would enable new applications of inertial sensing that are presently either infeasible or unconsidered. By adding inertial terms to the Paul trap dynamics we derive classical observables that depend on the local acceleration field. We also confirm that these observables appear in practice, in what we believe to be the first electrodynamic particle trap accelerometer. An important (and unusual) aspect of our accelerometer is its dynamic tunability: its effective spring constant depends on the trap drive parameters. Our roughly constructed trap also exhibits a large region of linear response to acceleration, and we present evidence suggesting that our accelerometer has performance comparable to commercially available sensors.
by Ernest Rehmatulla Post.
Ph.D.
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Hardy, Jonathan James. "Convergence and commercial speech : a study of the dynamics and the regulation of cross-media promotion in UK media." Thesis, Goldsmiths College (University of London), 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.408041.
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Pfab, Robert Joseph. "Dynamics of single molecules in confined media and towards two-photon interference /." Zürich : ETH, 2006. http://e-collection.ethbib.ethz.ch/show?type=diss&nr=16755.
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Comolli, Alessandro. "Mechanism and stochastic dynamics of transport in Darcy-scale heterogeneous porous media." Doctoral thesis, Universitat Politècnica de Catalunya, 2018. http://hdl.handle.net/10803/620618.
Full textAbstract:
Solute transport in heterogeneous porous media in general exhibits anomalous behaviors, in the sense that it is characterized by features that cannot be explained in terms of traditional models based on the advection-dispersion equation with constant effective coefficients. Signatures of anomalous transport are the non-linear temporal growth of the variance of solute concentration, non- Gaussian density profiles and heavy-tailed breakthrough curves. Understanding and predicting transport behavior in groundwater systems is crucial for several environmental and industrial applications, including groundwater management and risk assessment for nuclear waste repositories. The complexity of this task lies in the intrinsic multi-scale heterogeneity of geological formations and in the large amount of degrees of freedom. Hence, the predictive description of transport requires a process of upscaling that is based on measurable medium and flow attributes. The time domain random walk (TDRW) and continuous time random walk (CTRW) approaches provide suitable frameworks for transport upscaling.
In this thesis, we identify different mechanisms that induce anomalous transport and we quantify their impact on transport attributes. We propose average transport models that can be parameterized in terms of flow and medium properties. Among the mechanisms that induce non-Fickian behaviors, a pivotal role is played by the heterogeneity of the flow field, which is directly linked to medium
disorder. Due to its importance, the impact of advective heterogeneity is studied throughout the thesis, alongside with other mechanisms.
First, we consider solute trapping due to physical or chemical heterogeneity, which we parameterize in terms of a constant trapping rate and a distribution of return times. We observe three distinct transport regimes that are linked to characteristic trapping time scales. At early times, transport is advection- controlled until particles start to get trapped. Then, the increasing distance between mobile and immobile particles gives rise to a superdiffusive regime which finally evolves towards a trapping-controlled regime.
Second, we study transport in correlated porous media. We show that particle motion describes a coupled CTRW that is parameterized in terms of the distribution of flow velocity and length scales. We show that disorder and correlation may lead to similar behaviors in terms of displacement moments, but the difference between these mechanisms is manifest in the distributions of particle
positions and arrival times.
Next, we study the relationship between flow and transport properties and the impact of different injection conditions on transport. To this end, the relationship between Eulerian and Lagrangian velocities is investigated. Lagrangian statistics evolves to a steady-state that depends on the injection conditions. We study the velocity organization in Darcy flows and we develop a CTRW model for transport that is parameterized in terms of flow and medium attributes only. This CTRW
accounts for non-stationarity through Markovian velocity models. We study the impact of advective heterogeneity by considering different disorder scenarios.
Finally, we quantify the impact of diffusion in layered and fibrous heterogeneous media by considering two disorder scenarios characterized by quenched random velocities and quenched retardation properties, respectively. These mechanisms lead to different, dimension-dependent disorder samplings that give rise to dual transport processes in space and time. Specifically, transport describes correlated Lévy flights in the random velocity model and correlated CTRWs in the random retardation model.El transporte de solutos en medios heterogéneos porosos exhibe comportamientos anómalos, que se caracteriza por rasgos que no pueden ser explicados en términos de modelos tradicionales basados en la ecuación de advección-dispersión con coeficientes efectivos constantes. Las características del transporte anómalo son el crecimiento temporal no lineal de la varianza de la concentración de soluto, los perfiles de densidad no gausianos y la curvas de llegada con colas pronunciadas. Entender y predecir el comportamiento del transporte en hidrología subterránea es crucial para aplicaciones ambientales e industriales, como la gestión de aguas subterráneas o la evaluación de riesgos en repositorios de residuos nucleares. La complejidad de estas tareas se debe a la heterogeneidad intrínseca en múltiples escalas de las formaciones geológicas y del gran número de grados de libertad. Por lo tanto, una descripción predictiva del transporte requiere un proceso de upscaling basado en propiedades medibles del medio y el flujo para el que los modelos time domain random walk (TDRW) y continuous time random walk (CTRW) proporcionan un marco adecuado. En esta tesis, se identifican los mecanismos que inducen transporte anómalo y se cuantifica su impacto en el transporte. Se proponen modelos de transporte parametrizados en términos de las propiedades del medio y el flujo. Entre los mecanismos que inducen comportamientos no fickianos, la heterogeneidad del flujo, relacionada con el desorden del medio, desempeña un papel fundamental. Por lo tanto, su impacto se estudia junto con los de otros mecanismos a lo largo de toda la tesis. Primero, se considera el atrapamiento de soluto debido a heterogeneidades físicas o químicas parametrizadas en términos de un ratio de atrapamiento constante y una distribución de tiempos de retorno. Se observan tres regímenes de transporte relacionados con las escalas temporales características del atrapamiento. A tiempos pequeños, el transporte está controlado por la advección hasta que las partículas comienzan a ser atrapadas. A continuación el incremento de la distancia entre partículas móviles e inmóviles origina un régimen superdifusivo que finalmente evoluciona hacia un régimen controlado por el atrapamiento. Después, se estudia el transporte en medios correlacionados en los que el movimiento de las partículas es descrito por un CTRW acoplado parametrizado según la distribución de velocidades del flujo y de las escalas espaciales. El desorden y la correlación generan comportamientos similares en los momentos del desplazamiento de las partículas, pero diferentes en las distribución de posiciones y de tiempos de llegada. A continuación, se estudia la relación entre flujo y transporte bajo diferentes condiciones de inyección, a través de las velocidades eulerianas y lagrangianas. La estadística lagrangiana evoluciona hacia un estado estacionario que depende de los modos de inyección. Se estudia la organización de las velocidades en flujos de Darcy y se desarrolla un CTRW para el transporte que se parametriza solo en términos de las propiedades del medio y del flujo. Este CTRW considera la no estacionariedad a través de modelos de velocidad markovianos. El impacto de la heterogeneidad advectiva se estudia considerando diferentes escenarios de desorden. Finalmente, se cuantifica el impacto de la difusión en medios heterogéneos estratificados considerando dos escenarios de heterogeneidad que se caracterizan respectivamente por velocidades y propiedades de retraso aleatorias. Estos mecanismos originan diferentes muestreos del desorden que generan procesos de transportes duales en tiempo y espacio. El transporte describe un Lévy flight correlacionado en el modelo de velocidades aleatorias y un CTRW correlacionado en el modelo de retraso.