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1
Sun, Bo. "Modelling of Interaction Units." Thesis, Linköping University, Department of Computer and Information Science, 2005. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-2859.
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Developing a model of a service system and mobile units including cellphone, PDA, Laptop is an important preliminary step of designing the systems which could provide these units some convenient and entertainment services through common short range communication like blue tooth, wireless LAN, etc.
In this project, an ontology is created to represent this model. Meanwhile, some basic service rules are also programmed and combined with this ontology can be used to simulate some interactions between items inside this model.
The description of this model (ontology) has been made through Protégé and demonstrated by using its graphical interface. The rules have been created by using Jess and implemented with the ontology by using JessTab.
2
Weir, Daryl. "Modelling uncertainty in touch interaction." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/6318/.
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Touch interaction is an increasingly ubiquitous input modality on modern devices. It appears on devices including phones, tablets, smartwatches and even some recent laptops. Despite its popularity, touch as an input technology suffers from a high level of measurement uncertainty. This stems from issues such as the ‘fat finger problem’, where the soft pad of the finger creates an ambiguous contact region with the screen that must be approximated by a single touch point. In addition to these physical uncertainties, there are issues of uncertainty of intent when the user is unsure of the goal of a touch. Perhaps the most common example is when typing a word, the user may be unsure of the spelling leading to touches on the wrong keys. The uncertainty of touch leads to an offset between the user’s intended target and the touch position recorded by the device. While numerous models have been proposed to model and correct for these offsets, existing techniques in general have assumed that the offset is a deterministic function of the input. We observe that this is not the case — touch also exhibits a random component. We propose in this dissertation that this property makes touch an excellent target for analysis using probabilistic techniques from machine learning. These techniques allow us to quantify the uncertainty expressed by a given touch, and the core assertion of our work is that this allows useful improvements to touch interaction to be obtained. We show this through a number of studies. In Chapter 4, we apply Gaussian Process regression to the touch offset problem, producing models which allow very accurate selection of small targets. In the process, we observe that offsets are both highly non-linear and highly user-specific. In Chapter 5, we make use of the predictive uncertainty of the GP model when applied to a soft keyboard — this allows us to obtain key press probabilities which we combine with a language model to perform autocorrection. In Chapter 6, we introduce an extension to this framework in which users are given direct control over the level of uncertainty they express. We show that not only can users control such a system succesfully, they can use it to improve their performance when typing words not known to the language model. Finally, in Chapter 7 we show that users’ touch behaviour is significantly different across different tasks, particularly for typing compared to pointing tasks. We use this to motivate an investigation of the use of a sparse regression algorithm, the Relevance Vector Machine, to train offset models using small amounts of data.
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Ospina, Forero Luis Eduardo. "Modelling protein-protein interaction networks." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:c5150074-e160-4c59-8c23-f8804ae3dd2e.
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Proteins, the main motors of the cell, are in charge of performing a diverse array of biological functions. They rarely perform those functions alone, but generally work as groups of proteins that through a complex array of interactions perform a single biological function. These complex interactions between different proteins are often analysed via network theory, where a protein-protein interaction (PPI) network is created considering each protein as a node and each of their interactions as edges. Different approaches from the perspective of network analysis have been proposed to describe, analyse, and predict PPI networks. Some methods focus on the use of network summary statistics, community detection, random graph models, and machine learning procedures. However, despite the large effort invested in PPI network research, current models fail to describe well the structure of PPI networks. Small overrepresented subgraphs, which have been thought as the building blocks of networks, have been shown to be important patterns in gene regulatory networks, and there is evidence that suggests they may be evolutionarily conserved across the PPI networks of different organisms. Hence, a first step to better understand the structure of protein-protein interaction networks, is to describe how the local structure of these networks, accounted by the occurrence of small connected subgraphs, is created. We approach this problem in two stages. In the first stage, we provide a framework to statistically assess if a random graph model can describe the occurrence of different small connected subgraphs observed in PPI networks. Then, by applying this framework we find that state-of-the-art network comparison methods based on subgraph counts struggle at finding similarities between networks that have different numbers of nodes or edges. Hence, in joint work with Dr. Anatol Wegner, Dr. Robert Gaunt, Professor Gesine Reinert, and Professor Charlotte M. Deane, we propose a novel network comparison method, NetEmd, that tackles this problem indirectly by proposing a method that is invariant to translations and rescalings of subgraph count distributions, and which is better able to detect similarities across networks with different number of nodes or edges. In the second stage, we use NetEmd, along with three other state-of-the-art network comparison methods, to test the ability of several random graph models to describe the occurrence of subgraphs counts in the PPI networks of six organisms, and in multiple smaller sections of these networks. We find that the overall occurrence of small connected subgraphs could potentially be described by two network generation mechanisms operating in complementary sections of the PPI networks. In addition we find that cellular compartment-specific PPI networks can be potentially described by a single model that captures, with only two parameters, both, the common properties between the different cellular compartment networks, and their individual structural features.
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Cheong, T. P. "Numerical modelling of soil-pipeline interaction." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.597580.
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This thesis investigates the interaction between soil and pipeline in sand subjected to lateral ground loading. The purpose of this study is to improve the structural modelling of buried pipelines; and also aims to produce design guidelines and construct normalised charts which will be of direct benefit to practising pipeline engineers. The research was performed entirely using the finite element (FE) method, and utilised the user subroutine of an advanced constitutive soil model that was implemented in this thesis. The problems examined in this research can be categorised into four main topics. First, 2-D FE analyses were conducted concerning with the effects of loading rate on a laterally-loaded pipeline buried in saturated sand. All indications support the conclusion that both the sand dilatancy and hydraulic conductivity of the soil in relation to the loading rate are important factors for mobilisation of the lateral resistance of a pipeline in a saturated soil medium. Second, soil loading on a pipeline under global soil shearing conditions was investigated by performing different types of relative ground and pipeline movement modes, with the aim of generating both passive and active failure states. Overall, it can be concluded that the effect of global soil shearing on the interaction of soil and pipeline is relatively small in terms of Nq, implying that local soil deformation and soil dilation characteristics are most important and influential factors contributing to the magnitude of the lateral pressure on pipelines. Third, investigations of the behaviour of an elbow-bend pipe, under lateral soil loading were performed using a 3-D FE modelling method. It was found that deeper burial pipeline, denser soil and elbow-bend pipe with larger bending angle accounted higher Nq. Also Nq at the elbow-bend pipe was about 2.7 times higher than a straight pipe. The results confirmed that the ‘3-D elbow effect’ can be ignored in the closing mode case, but in the opening mode case, the effect was computed at about 17% when compared to a 2-D bilinear soil-spring model case. Additionally, a larger effective plastic strain region was observed when 3-D soil-spring models were adopted in the design. Fourth, in order to achieve a reliable design procedure against permanent ground deformation (PGD), a full-scale 3-D FE numerical analysis and a full-scale 3-D spring model analysis were both carried out on a 90° elbow pipeline. Encouraging and good results were achieved from both of the numerical models when compared with the data from experiments carried out at Cornell University. Thus, it is shown that the adopted 3-D FE method was able to simulate the observed pipeline performance under PGD ground failure in a reliable way.
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Carlin, Paul. "Modelling vergence, accommodation and their interaction." Thesis, Glasgow Caledonian University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.241881.
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The vergence and accommodation systems, which are examples of physiological control systems, enable us to acquire and maintain clear single images of objects at a variety of distances in our visual world. Vergence and accommodation systems are interact with one each other and have both visual and non-visual components thus adding to their complexity. This thesis reviews the evolution of control theory models of vergence and accommodation from the 1960's to the present day and has outlined several properties of the systems which require further study. The thesis introduces the concept of Fuzzy Logic Control (FLC) to models of oculomotor control. FLC offers a new approach to modelling natural control systems and produces more realistic models than those obtained using conventional control theory techniques. Several characteristics of the vergence and accommodation systems were investigated with the aim of incorporating experimental data into control theory models using conventional techniques and FLC. The accommodation response to anisometropic stimuli was measured objectively. No evidence of a non-consensual response was found, from which it can be concluded that accommodation is consensual. A control theory model of binocular accommodation was simulated to illustrate the control strategies adopted by the accommodation during anisometropic stimulation. A Virtual Reality (VR) stimulus was used to investigate the possibility of adaptation of the crosslink components of vergence and accommodation by placing different demands on the vergence and accommodation systems. Crosslink behaviour was altered as a result of the VR stimulus which suggests that the links between vergence and accommodation (accommodative vergence and vergence accommodation) are amenable to adaptation. Control theory models were used to illustrate the effects of the VR stimulus on vergence and accommodation. The effect of proximity was investigated by measuring accommodation responses in the presence and absence of proximal cues. The effect of proximal cues under closed loop conditions was found to be minimal which suggests that proximal cues are only effective when visual cues are reduced. The results were extended to include the vergence system and a FLC model of proximal vergence and accommodation was implemented. Simulation of the model produced similar findings to a previous study which supports the use of FLC in models of oculomotor control. Voluntary vergence and accommodation were measured objectively under open loop conditions in a group of naive subjects. All subjects were able to produce voluntary responses corresponding to near and far. The ability of subjects to distinguish intermediate distances was more varied. The results show that voluntary responses can be produced without training and it is suggested that voluntary vergence and accommodation may be an important mode of response. The results were included in a control model of voluntary vergence and accommodation using FLC. The work presented provides support for the use of Fuzzy Logic in models of oculomotor control which can be used to improve models and complement existing models using conventional techniques.
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Townson, Peter Gerard Allan Luke. "Load-maintenance interaction : modelling and optimisation /." [St. Lucia, Qld.], 2002. http://adt.library.uq.edu.au/public/adt-QU20021108.134015/index.html.
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LoVetri, Joseph (Joe). "Computer techniques for electromagnetic interaction modelling." Thesis, University of Ottawa (Canada), 1991. http://hdl.handle.net/10393/7619.
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Computer techniques for the modelling of complex electromagnetic interactions are explored. The main thesis is that these techniques, or methods, can be divided into two types: non-algorithmic and algorithmic techniques. Approximate algorithmic methods for the modelling of electromagnetic interactions have undergone great advances in the past twenty years but they are still only feasible for relatively small problems (i.e. where the space-time discretization produces and requires only a relatively small number of unknowns). The computer implementation of non-algorithmic methods have recently become a reality with the maturing of expert system technology and knowledge based engineering. In Part I of this thesis, a knowledge-based approach for the modelling of electromagnetic (EM) interactions in a system is described. The purpose is to determine any unwanted EM effects which could jeopardize the safety and operation of the system. Modelling the interactions in a system requires the examination of the compounded and propagated effects of the electromagnetic fields. A useful EM modelling approach is one which is incremental and constraint-based. The approach taken here subdivides the modelling task into two parts: (a) the definition of the related physical topology, and (b) the propagation of the electromagnetic constraints. A prototype of some of the EM constraints has been implemented in Quintus Prolog under NeWS on a Sun workstation. User interaction is through a topology drawing tool and a stack-based attribute interface similar to the HyperCard$\sp{\rm TM}$ interface of the Apple Macintosh computer. In Part II, numerical methods which discretize the space-time region of interest and provide a solution to the electromagnetics problem, given appropriate initial and boundary conditions, are investigated. Specifically, time-domain finite difference methods as applied to Maxwell's equations are analyzed, compared and implemented. As the basis of this analysis, Maxwell's equations are expressed as a system of hyperbolic conservation laws. Analytical properties of these systems, based on the method of characteristics, are used to study the numerical solution of Maxwell's equations. Practical issues, such as computational efficiency and memory requirements, are discussed for the implementation of the finite difference schemes. Advanced programming techniques are used to implement all the finite difference schemes discussed. The schemes are used to solve the problem of the penetration of electromagnetic energy through a shield with a thick gap. A two-dimensional time-domain finite element method, implemented as the software package PDE/PROTRAN, is also applied to shielding problems. The software package is first validated for simple hyperbolic problems and is then applied to perfectly conducting shields with apertures.
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Nelson, R. B. "Modelling vortex-vortex and vortex-boundary interaction." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/19222/.
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The motion of two-dimensional inviscid, incompressible fluid with regions of constant vorticity is studied for three classes of geophysically motivated problem. First, equilibria consisting of point vortices located near a vorticity interface generated by a shear flow are found analytically in the linear (small-amplitude) limit and then numerically for the fully nonlinear problem. The equilibria considered are mainly periodic in nature and it is found that an array of equilibrium shapes exist. Numerical equilibria agree well with those predicted by linear theory when the amplitude of the waves at the interface is small. The next problem considered is the time-dependent interaction of a point vortex with a single vorticity jump separating regions of opposite signed vorticity on the surface of a sphere. Initially, small amplitude interfacial waves are generated where linear theory is applicable. It is found that a point vortex in a region of same signed vorticity initially moves away from the interface and a point vortex in a region of opposite signed vortex moves towards it. Configurations with weak vortices sufficiently far from the interface then undergo meridional oscillation whilst precessing about the sphere. A vortex at a pole in a region of same sign vorticity is a stable equilibrium whereas in a region of opposite-signed vorticity it is an unstable equilibrium. Numerical computations using contour dynamics confirm these results and nonlinear cases are examined. Finally, techniques based on conformal mapping and the numerical method of contour dynamics are presented for computing the motion of a finite area patch of constant vorticity on a sphere and on the surface of a cylinder in the presence of impenetrable boundaries. Several examples of impenetrable boundaries are considered including a spherical cap, longitudinal wedge, half-longitudinal wedge, and a thin barrier with one and two gaps in the case of the sphere, and a thin island and ‘picket’ fence in the case of the cylinder. Finite area patch motion is compared to exact point vortex trajectories and good agreement is found between the point vortex trajectories and the centroid motion of finite area patches when the patch remains close to circular. More exotic motion of the finite area patches on the sphere, particularly in the thin barrier case, is then examined. In the case when background flow owing to a dipole located on the barrier is present, the vortex path is pushed close to one of the barrier edges, leading to vortex shedding and possible splitting and, in certain cases, to a quasi-steady trapped vortex. A family of vortex equilibria bounded between the gap in the thin barrier on a sphere is also computed.
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Fischer, Manfred M., and Daniel A. Griffith. "Modelling spatial autocorrelation in spatial interaction data." WU Vienna University of Economics and Business, 2007. http://epub.wu.ac.at/3948/1/SSRN%2Did1102183.pdf.
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Spatial interaction models of the gravity type are widely used to model origindestination
flows. They draw attention to three types of variables to explain variation in spatial
interactions across geographic space: variables that characterise an origin region of a flow,
variables that characterise a destination region of a flow, and finally variables that measure the
separation between origin and destination regions. This paper outlines and compares two
approaches, the spatial econometric and the eigenfunction-based spatial filtering approach, to
deal with the issue of spatial autocorrelation among flow residuals. An example using patent
citation data that capture knowledge flows across 112 European regions serves to illustrate the
application and the comparison of the two approaches.(authors' abstract)
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David, Thevaneyan Krishta David. "Integral bridges: modelling the soil-structure interaction." Thesis, University of Leeds, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581881.
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Integral abutment bridges, also known as integral bridges, have become one of the most common types of joint-less bridge construction, certainly over the last three decades. Their principal advantages are derived from the elimination of expansion joints and bearings, making them a very cost-effective system in terms of construction, maintenance, and longevity. The elimination of joints from bridges creates a significant soil-structure interaction behind the abutment and the piles generating an interesting problem since the response of the different elements of the integral bridge are interdependent. This research project used numerical analyses to investigate the complex interactions that exist between the structural components of the stub-type integral abutment bridge and the backfill soil. Where possible, these results were validated with existing field data. A literature review was conducted to gain an insight into the behaviour of integral abutment bridges, particularly the soil-structure interaction of integral bridges. To gain a better understanding of the behaviour of integral abutment bridges and their interaction with the backfill soil adjacent to the abutment and the piles, particularly due to thermally induced movement/loads, a 2D finite element analysis was performed on a typical integral abutment bridge using OASYS GSA and OASYS SAFE. The results from this research are believed to help answer two of the most debated issues with respect to stub-type integral abutment bridge-soil interaction analyses. Firstly, it is clear, and now possible, that a reliably accurate soil profile is used in the analysis/design. The Mohr-Coulomb soil model was found to realistically represent the soil behaviour. Secondly, the research may suggest that cyclic movements / loads may not significantly influence the overall behaviour of integral abutment bridges. In addition, it was found that the development of earth pressure behind the integral abutment is significantly affected by the backfill soil properties and is a function of the integral abutment displacement. Limiting values for the abutment displacement, which induces maximum backfill pressure, have been suggested. The soil separation phenomenon (gapping) was also found to significantly affect the backfill/foundation soil-load relationship behaviour. Implications· of this research for practising engineers and recommendations for future research work are also included.
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Dewsbury, Jonathan J. "Numerical modelling of soil-pile-structure interaction." Thesis, University of Southampton, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.582152.
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Soil-pile-structure interaction analysis is the simultaneous consideration of the structural frame, pile foundations, and the soil forming the founding material. Failure to consider soil-pile-structure interaction in design will lead to a poor prediction of load distribution within the structure. A poor prediction of load distribution will cause the structure to deform under loads that have not been calculated for. This may result in the structure cracking or the overstressing of columns. If the actual load distribution significantly differs from that designed for, the factor of safety on structural elements may be substantially decreased. Despite the importance, there are currently no studies quantifying the effect of soil-pile-structure interaction for simple office structures. As a result the effects of soil-pile-structure interaction are often deemed unimportant, and ignored in the design of simple structures. Numerical methods are often relied upon to consider soil-pile-structure interaction for complex structures, such as tall towers. However in their current form they are limited because the meshes required for analysis, especially when in three dimensions, are difficult to verify, and take a long time to set up and run. Therefore this thesis proposes a meshing method within the framework of the finite element method that allows large, complex, and non-symmetrical pile foundation layouts to be meshed in a manner that is quick, can be easily checked, and significantly reduces the analysis run time. Application of the meshing method to an office structure (recently designed for the 2012 Olympic Games) has allowed the effects of soil-pile-structure interaction to be quantified. The subsequent normalisation of the results provides a method for assessing when it is necessary to consider soil- pile-structure interaction in future design. Comparison between the monitored performance of 'The Landmark' (a 330m tower founded on a piled raft) and numerical predictions have demonstrated the importance of correct ground stiffness selection for achieving accurate predictions of piled raft settlement, and load distribution. The role of single pile load tests and in situ testing for ground stiffness selection for piled raft design has also been assessed
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Taunton, Paul R. "Centrifuge modelling of soil/masonry structure interaction." Thesis, Cardiff University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.244112.
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Zamuner, Stefano. "Ligand-receptor interaction modelling using PET imaging." Thesis, City University London, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274523.
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Gallo, Ignacio Alejandro <1981>. "An equilibrium approach to modelling social interaction." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2009. http://amsdottorato.unibo.it/2126/.
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The aim of this work is to put forward a statistical mechanics theory of social interaction, generalizing econometric discrete choice models. After showing the formal equivalence linking econometric multinomial logit models to equilibrium statical mechanics, a multi- population generalization of the Curie-Weiss model for ferromagnets is considered as a starting point in developing a model capable of describing sudden shifts in aggregate human behaviour. Existence of the thermodynamic limit for the model is shown by an asymptotic sub-additivity method and factorization of correlation
functions is proved almost everywhere. The exact solution for the model is provided in the thermodynamical limit by nding converging upper and lower bounds for the system's pressure, and the solution is used to prove an analytic result regarding the number of possible equilibrium states of a two-population system. The work stresses the importance of linking regimes predicted by the model to real phenomena, and to this end it proposes two possible
procedures to estimate the model's parameters starting from micro-level data. These are applied to three case studies based on census type data: though these studies are found to be ultimately inconclusive on an empirical level, considerations are drawn that encourage further refinements of the chosen modelling approach, to be considered in future work.
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Siddorn, Philip David. "Efficient numerical modelling of wave-structure interaction." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:de36bd2f-cd23-4f11-b67f-9d8cd48ecd3c.
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Offshore structures are required to survive in extreme wave environments. Historically, the design of these offshore structures and vessels has relied on wave-tank experiments and linear theory. Today, with advances in computing power, it is becoming feasible to supplement these methods of analysis with fully nonlinear numerical simulation. This thesis is concerned with the development of an efficient method to perform this numerical modelling, in the context of potential flow theory. The interaction of a steep ocean wave with a floating body involves a moving free surface and a wide range of length scales. Attempts to reduce the size of the simulation domain cause problems with wave reflection from the domain edge and with the accurate creation of incident waves. A method of controlling the wave field around a structure is presented. The ability to effectively damp an outgoing wave in a very short distance is demonstrated. Steep incident waves are generated without the requirement for the wave to evolve over a large time or distance before interaction with the body. This enables a general wave-structure interaction problem to be modelled in a small tank, and behave as if it were surrounded by a large expanse of water. The suitability of the boundary element method for performing this modelling is analysed. Potential improvements are presented with respect to accuracy, robustness, and computational complexity. Evidence of third order diffraction is found for an FPSO model.
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Fischer, Manfred M., and Martin Reismann. "Evaluating Neural Spatial Interaction Modelling by Bootstrapping." WU Vienna University of Economics and Business, 2000. http://epub.wu.ac.at/4241/1/WGI_DP_7200.pdf.
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This paper exposes problems of the commonly used technique of splitting the available
data in neural spatial interaction modelling into training, validation, and test sets that
are held fixed and warns about drawing too strong conclusions from such static splits.
Using a bootstrapping procedure, we compare the uncertainty in the solution stemming
from the data splitting with model specific uncertainties such as parameter
initialization. Utilizing the Austrian interregional telecommunication traffic data and
the differential evolution method for solving the parameter estimation task for a fixed
topology of the network model [ i.e. J = 9] this paper illustrates that the variation due to
different resamplings is significantly larger than the variation due to different parameter
initializations. This result implies that it is important to not over-interpret a model,
estimated on one specific static split of the data. (authors' abstract)Series: Discussion Papers of the Institute for Economic Geography and GIScience
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Steiglechner, Peter. "A Spatially Explicit Agent-Based Model of Human-Resource Interaction on Easter Island." Thesis, KTH, Numerisk analys, NA, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-277730.
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The history of Easter Island, with its cultural and ecological mysteries, has attracted the interests of archaeologists, anthropologists, ecologists, and economists alike. Despite the great scientific efforts, uncertainties in the available archaeological and palynological data leave a number of critical issues unsolved and open to debate. The maximum size reached by the human population before the arrival of Europeans and the temporal dynamics of deforestation are some of the aspects still fraught with controversies. By providing a quantitative workbench for testing hypotheses and scenarios, mathematical models are a valuable complement to the observational-based approaches generally used to reconstruct the history of the island. Previous modelling studies, however, have shown a number of shortcomings in the case of Easter Island, especially when they take no account of the stochastic nature of population growth in a temporally and spatially varying environment. Here, I present a new stochastic, Agent-Based Model characterised by (1) realistic physical geography of the island and other environmental constraints (2) individual agent decision-making processes, (3) non-ergodicity of agent behaviour and environment, and (4) randomised agent-environment interactions. I use the model and the best available data to determine plausible spatial and temporal patterns of deforestation and other socioecological features of Easter Island prior to the European contact. I further identify some non-trivial connections between microscopic decisions or constraints (like local confinement of agents' actions or their adaptation strategy to environmental degradation) and macroscopic behaviour of the system that can not easily be neglected in a discussion about the history of Easter Island before European contact.Påsköns historia har, med dess kulturella och ekologiska mysterier, väckt intressen hos arkeologer, antropologer, ekologer och ekonomer. Trots de stora vetenskapliga ansträngningarna lämnar osäkerheten i de tillgängliga arkeologiska och palynologiska data ett antal kritiska frågor olösta och öppna för debatt. Den maximala storleken som den mänskliga befolkningen nådde före européernas ankomst, och avskogningens tidsmässiga dynamik, är några av de aspekter som fortfarande är fyllda med kontroverser. Genom att tillhandahålla en kvantitativ arbetsbänk för att testa hypoteser och scenarier är matematiska modeller ett värdefullt komplement till de observationsbaserade metoder som vanligtvis används för att rekonstruera öns historia. Tidigare modelleringsstudier har emellertid visat ett antal brister i fallet med Påskön, särskilt när de inte tar hänsyn till den stokastiska karaktären av befolkningsökningen i en tillfällig och rumsligt varierande miljö. Här presenters en ny stokastisk, agentbaserad modell som kännetecknas av (1) realistisk fysisk geografi av ön och andra miljömässiga begränsningar, (2) individuella beslutsprocesser av agenter, (3) icke-ergodicitet av agentens beteende och miljö och (4) randomiserade agent-miljöinteraktioner. Modellen används tillsammans med de bästa tillgängliga data för att bestämma rimliga rumsliga och temporära mönster av avskogning och andra socioekologiska egenskaper på Påskön före européers ankoms. Vidare identifieras några icke-triviala förbindelser mellan mikroskopiska beslut eller begränsningar (till exempel lokal inneslutning av agentens handlingar eller deras anpassningsstrategi till miljöförstöring) och makroskopiskt beteende hos systemet som inte lätt kan försummas i en diskussion om påsköns historia före europeisk kontakt.
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Ritter, Stefan. "Experiments in tunnel-soil-structure interaction." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/273891.
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Urbanisation will require significant expansion of underground infrastructure, which results in unavoidable ground displacements that affect the built environment. Predicting the interaction between a tunnel, the soil and existing structures remains an engineering challenge due to the highly non-linear behaviour of both the soil and the building. This thesis investigates the interaction between a surface structure and tunnelling-induced ground displacements. Specifically, novel three-dimensionally printed building models with brittle material behaviour, similar to masonry, were developed and tested in a geotechnical centrifuge. This enabled replication of building models with representative global stiffness values and realistic building features including strip footings, intermediate walls, a rough soil-structure interface, building layouts and façade openings. By varying building characteristics, the impact of structural features on both the soil and building response to tunnelling in dense sand was investigated. Results illustrate that the presence of surface structures considerably altered the tunnelling-induced soil response. The building-to-tunnel position notably influences the magnitude of soil displacements and causes localised phenomena such as embedment of building corners. An increase of the façade opening area and building length reduces the alteration of the theoretical greenfield settlements, in particular the trough width. Moreover, the impact of varying the building layout is discussed in detail. For several building-tunnel scenarios, building distortions are quantified and the crucial role of building features is demonstrated. Structures spanning the greenfield inflection point experienced more deformation than identical structures positioned in either sagging or hogging, and partitioning a structure either side of the greenfield inflection point is shown to lead to unconservative damage assessments. Results also quantify the significant extent to which structural distortions increase as façade openings and building length increases. Observed building damage and cracking patterns confirm the reported trends. The experimental results are used to evaluate the performance of available methods to assess the behaviour of buildings to tunnelling. Predictions ignoring soil-structure interaction are usually overly conservative, while approaches based on the relative stiffness of a structure and the soil result in inconsistent predictions, though some methods performed better than others. Practical improvements to consider structural details when assessing this tunnel-soil-structure system are finally proposed.
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Lucero, Tenorio Luz Alexandra. "Hydro Turbine and Governor Modelling : Electric - Hydraulic Interaction." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-11105.
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This Masters Thesis work deals with the development of improved hydro turbine models for the evaluation of a hydraulic power generating system performance in response to small disturbances in power system analysis tool. These improved models must be able to reflect the possible interaction between the hydraulic system and power system in the computer simulations of a power plant equipped with Francis turbines.The accuracy of a Hydraulic Power Generating System is studied by means of analysis of the dynamic behaviour of different models of the hydraulic machine and conduit system. The stability study of different models for Synchronous Machines and Turbine Governing System are beyond the scope of this work.Appropriate representations of the hydraulic turbine and conduit system are developed in various models of varying degrees of detail. Firstly, nonlinear models for a simple turbine without surge tank considering the inelastic and elastic travelling wave effects have been developed. After that, nonlinear models considering the inelastic and elastic travelling wave effects for a turbine with surge tank for Hydropower Systems with long length penstocks are implemented. Finally, the nonlinear models for a turbine with long length penstocks are linearized at an operating point considering both the nonlinear turbine characteristics and the travelling wave effects.The Masters Thesis work is divided into three parts. The first part, comprising Chapters 2 to 8, reviews the physical characteristics and mathematical models of the components of a hydraulic power generating system. The influence of each component of the power system by means of appropriate mathematical models is essential for the understanding of system stability. The second part, comprising Chapters 9 to 11, deals with the dynamic study of the system stability characteristics of the different hydraulic power generating system models implemented in SIMPOW and LVTrans. Finally, the third part, Chapter 12 and Chapter 13, presents the discussion of the simulation results of the hydroelectric power system models, and draws general conclusions on this work and suggests possibilities for the approach further work, respectively.It was concluded that approaches based on nonlinear and linear models including the elasticity of the conduit system and the nonlinear turbine characteristics extracted from the Hill Charts, are the most accurate models for any acceptable study of the interaction between hydraulic system and power system.The study of dynamic performance and interaction between the hydraulic system and power system of these extended linear and nonlinear models including the elastic water hammer effect and varying the nonlinear characteristics of the hydraulic turbine must be studied in detail.
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Bennett, Gary Stuart. "Mathematical modelling of wave interaction with vertical structures." Thesis, Brunel University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.332808.
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Aly, Emad Hassan. "Modelling the behaviour of soil-cooling tower-interaction." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/16745.
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Natural draught cooling towers belong to a category of exceptional civil engineering structures. These towers are an effective and economic choice among all technical solutions for the prevention of thermal pollution of natural water resources caused by heated cooling water in various industrial facilities. They are therefore widely used in most electric power generation units, chemical and petroleum industries and space conditioning processes. The cooling tower shell is the most important part of the cooling tower, both in technical and financial terms and also the most sensitive, since its collapse would put all or part of the cooling tower out of action for a considerable length of time. In this thesis, the 2D and 3D behaviour of soil-cooling tower-interaction, via the idealisation of the structure and soil on the resulting parameters, have been investigated, taking into consideration the effect of temperature changes in the cooling tower on the simultaneous interaction of the cooling tower and underlying soil. The temperature effect has been considered because it plays an important role in the design of the cooling towers. The capabilities of the two-dimensional Geotechnical Finite Element Analysis Program (GeoFEAP) have been updated in this project and the new version has been referred to as GeoFEAP2. New modelling capabilities and the ability to model 3D problems, with accompanying postprocessing features, were introduced, including 3D first order 8-noded hexahedrons. In addition, the Drucker-Prager yield criterion was programmed in GeoFEAP2 to model the elasto-plastic behaviour of the soil. A new 4-noded quadrilateral flat shell element, based on discrete the Kirchhoff's quadrilateral plate bending element, was also added to the software to model the elastic behaviour of the cooling tower shell. Furthermore, this element was modified to accommodate a temperature profile. The new software (GeoFEAP2) was then validated for soil behaviour and using several standard widely-used benchmark problems and the results compared well with the analytical and/or numerical results obtained by other researchers. A 3D finite element model was created, comprising the cooling tower, columns support, foundation, and elasto-plastic soil behaviour. The analyses of soil-cooling tower-interaction in this thesis have indicated the need to model the soil and structure as a combined problem, rather than by applying loads onto soil as geotechnical engineers' model, or by assuming the soil comprises springs and model the cooling tower, as structural engineers' model. The results have shown how unrealistic the latter two approaches are. In addition, the analysis necessitates the incorporation of thermal effects when modelling cooling tower problems. Moreover, from a design point of view, it has been recommended that circular footing with two cross-columns is better than pad footings and/or one column. Several other conclusions have been made that would improve the modelling of soil-cooling tower-interaction. Furthermore, the designer needs to ensure that enough modelling of soil conditions is done and an extensive site investigation is required to ensure that the variation in soil properties is represented correctly. Finally, the engineer needs also to ensure that the site tests performed to measure shear strength with depth via drilling and other methods needs to go deep enough into the ground to ensure that enough site information is available when designing the cooling tower.
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Manchester, L. N. "Modelling the interaction of streptomycetes and their phage." Thesis, University of Liverpool, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372675.
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Kalenka, Susanne. "Modelling social interaction attitudes in multi-agent systems." Thesis, Queen Mary, University of London, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.395937.
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Mieczakowski, Anna Katarzyna. "Modelling interaction between product features and human capabilities." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610155.
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Oyeyemi, Oyebode. "Modelling HIV-1 interaction with the host system." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/modelling-hiv1-interaction-with-the-host-system(41095e34-78dd-4b75-bd25-9695a4cc768f).html.
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Human immunodeficiency virus (HIV-1) is the pathogenic agent of HIV infection thatprecedes the total breakdown of cellular immunity, a condition known as acquiredimmunodeficiency syndrome (AIDS). The pandemic nature of the disease has promptedintense research into its biology. Already, much is known about HIV-1 infection, lifecycle,and progression to aids. Systems biology enables the combination of complex data fromthese studies into a framework where their effect on the various levels of cellularorganization (i.e. Pathways, cells, tissues, organs and the whole body) could be studied insilico. In this thesis, first, we reviewed our knowledge of the HIV-1 Human InteractionDatabase. We examined its contents and identified processes that HIV-1 was not previouslyknown to interact with. Then, we attempted an in silico dynamic model of HIV-1 interaction. We built a model of HIV-1 interaction with the CD4 T cell activation pathway comprised of137 nodes (16 HIV-1, 121 human) and 336 interactions. The model reproduced expectedpatterns of T cell activation. Using interaction graph properties, we identified 26 host cellfactors, including MAPK1&3, Ikkb-Ikky-Ikka and PKA, which contribute to the net activationor inhibition of viral proteins. By following a logical Boolean formalism, we identified 9 hostcell factors essential to the functions of viral proteins in the activation pathway. This wasthe first attempt to model dynamic viral-host interaction relationships. Then, we organize HIV-1 interacting host genes into modules to represent cellular processesneeded by the virus. We combined HIV-1 interactions with host gene GO annotations toclassify host genes according to these needed cellular processes. We obtained 201 modulesand found the same set of viral proteins do not interact with host genes having similarmodules suggesting intelligence in its co-ordination of host processes. This work is one of agrowing list that explores coordination of HIV-1 interactions. But more importantly, it would bebeneficial to functionally downsize the large dynamic HIV-1 interaction network. Finally, in our discussion, we discuss our results and suggest possible ways in which our workon dynamic models could be improved. This work is opening up a new field of systems virologythat studies the effect of viruses on the host in terms of its temporal and spatial aspects.
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Khodabakhshi, Goodarz. "Computational modelling of fluid-porous solid interaction systems." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/35182.
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Deformation of a porous medium due to the pressure applied by an interacting fluid passing through it is a phenomenon which occurs in a number of applications such as filtration and membrane separation processes. Mathematical modelling of these systems using porous medium theory has proved to be beneficial in the design of experiments and equipments as well as gaining better insight about multi-physics phenomenon such as combined fluid flow and solid deformation regimes. In the present work the interaction of fluid and porous solid medium has been studied.
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Foy, Lindsay. "Developing interaction potentials from first principles." Thesis, University of Edinburgh, 2009. http://hdl.handle.net/1842/3795.
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Interaction potentials for the double-perovskite cryolite, Na3AlF6, have been developed for use in classical Molecular Dynamics (MD) simulations using a method whereby ionic configurations are generated with empirical pair potentials, the multipoles and forces on the ions and the stress tensor of the cell are extracted from ab initio single-point DFT calculations, and then the multipoles, forces and stresses from the MD simulations are ‘fit’ to the ab initio quantities in a series of steps in which the potential parameters are optimized, for models of varying complexity. Previously, interaction potentials have been developed empirically by tuning the parameters to reproduce experimentally-derived properties such as structure factors and densities, and so the testing and development of the newer method is necessary in order to standardize a way of obtaining potentials from first principle considerations. A fitted potential was then used to characterize the ion dynamics in crystalline cryolite: a monoclinic to orthorhombic phase transition and the low-temperature-phase tilt-domain structure of the AlF3− 6 , the dominant structural features, are reproduced. The motional processes, which have been studied indirectly in NMR, conductivity and diffraction experiments, include oscillation of the AlF3− 6 and sodium ion diffusion - it has been suggested that these occur at a remarkably fast rate. The nature of the AlF3− 6 oscillatory motion is studied in more depth than accessible to experiment, and its connection with diffusion is investigated. Given the intrinsically defective nature of cryolite and the absence of diffusion in the initial simulations, defects are introduced to observe their effect on the dynamics: they are shown to be necessary for diffusion. This work has been written up in an article accepted for publication in the Journal of Physical Chemistry. The ab initio potentials developed as above involve representing a system with formally charged monatomic ions. We extended the scope of the method significantly with technical developments to allow for the inclusion of molecular ions, such as the hydroxide ion, the sulphate ion or the uranyl ion, where the intraionic bonding has significant covalent character. The appropriate modifications of the MD code were made and a modified force-fitting procedure was developed. The new method was applied to Mg(OH)2 which is an important mineral (brucite) and to the melts of uranyl chloride which are of interest in nuclear waste reprocessing. Although we found good potentials were harder to obtain for these compounds, we found this arose from their layered structure rather than the molecular nature of the ions, and that our method could achieve a level of success approaching that used in the cryolite work on further iterations of the fitting process.
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Honorato-Zimmer, Ricardo. "On a thermodynamic approach to biomolecular interaction networks." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/28904.
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We explore the direct and inverse problem of thermodynamics in the context of rule-based modelling. The direct problem can be concisely stated as obtaining a set of rewriting rules and their rates from the description of the energy landscape such that their asymptotic behaviour when t → ∞ coincide. To tackle this problem, we describe an energy function as a finite set of connected patterns P and an energy cost function e which associates real values to each of these energy patterns. We use a finite set of reversible graph rewriting rules G to define the qualitative dynamics by showing which transformations are possible. Given G and P, we construct a finite set of rules Gp which i) has the same qualitative transition system as G and ii) when equipped with rates according to e, defines a continuous-time Markov chain that has detailed balance with respect to the invariant probability distribution determined by the energy function. The construction relies on a technique for rule refinement described in earlier work and allows us to represent thermodynamically consistent models of biochemical interaction networks in a concise manner. The inverse problem, on the other hand, is to i) check whether a rule-based model has an energy function that describes its asymptotic behaviour and if so ii) obtain the energy function from the graph rewriting rules and their rates. Although this problem is known to be undecidable in the general case, we find two suitable subsets of Kappa, our rule-based modelling framework of choice, were this question can be answer positively and the form of their energy functions described analytically.
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Jasevičius, Raimondas. "The Numerical Modelling of Normal Interaction of Ultrafine Particles." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2010~D_20110224_161120-06365.
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Recently, powders of the size d (0.1 μm < d < 10 μm) have been referred to ultrafine particles. The particle shape considered is assumed to be a sphere of the diameter d. The handling of powders is of great importance for processing of pharmaceuticals, cement, chemicals and other products. Most of these technological processes involve powder compaction, storage, transportation, mixing, etc, therefore, understanding of the fundamentals of particles interaction behaviour is very essential in the design of machines and equipment as well as in powder technology, cleaning of environment and other areas.
The dynamic behaviour of particulate systems is very complicated due to the complex interactions between individual particles and their interaction with the surroundings. Understanding the underlying mechanisms can be effectively achieved via particle scale research. The problem of a normal contact may be resolved in a number of ways. In spite of huge progress in experimental techniques, direct lab tests with individual particles are still rather time-consuming and expensive.
The interaction of particles as solid bodies is actually a classical problem of contact mechanics. In the case of ultrafine particles, the reduction of the particle size shifts the contact zones into the nanoscale or subnanoscale. Thus, steadily increasing contribution of adhesion has to be considered in the development of the physically correct constitutive models and numerical tools. Consequently, it may... [to full text]Ultrasmulkios dalelės yra šiuolaikinės chemijos, farmacijos, maisto ir kitų pramonės šakų produktų sudėtinė dalis. Tiriant pramoninius technologinius procesus, neišvengiamai reikalingos teorinės žinios apie ultrasmulkių dalelių elgseną. Išsamus supratimas įmanomas tik atlikus įvairius tyrimus. Pastaruoju metu milteliai, klasifikuojami kaip ultrasmulkios (0,1 < d < 10 μm) dalelės, imti plačiai naudoti pramoniniuose procesuose, todėl suprasti ultrasmulkių dalelių elgsenos fundamentalumą miltelių technologijoje yra labai svarbu. Ultrasmulki dalelė yra itin maža, todėl su ja atlikti fizinį eksperimentą, kuris reikalauja specialios įrangos bei žinių, labai sunku. Tokiu atveju dažniausiai naudojamas skaitinis eksperimentas, kurį galima atlikti virtualiai. Skaitinio eksperimento metu yra tiriamos dinaminės ultrasmulkios dalelės savybės bei sprendžiamas dinaminis uždavinys. Taikant skaitinius modelius bei dalelės judėjimą aprašančias jėgų lygtis, naudojami sąveikos modeliai, apimantys adhezinę, klampią, tamprią bei tampriai plastinę sąveikas. Mikroskopinis adhezinės sąveikos modeliavimas – aktualus mechanikos mokslo uždavinys. Taikant sąveikos modelius, svarbu pritaikyti ir diskrečiųjų elementų metodą, kadangi, norint aprašyti dalelių elgseną, visų pirma reikia su-vokti ir aprašyti dalelės modelį. Dalelės elgsenos skaitiniam modeliavimui siūlomi teoriniai modeliai leidžia tirti dalelės sąveiką su dalele ar tampria puserdve bei sąveikos dinamiką. Šie modeliai galėtų būti pritaikyti... [toliau žr. visą tekstą]
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Cloherty, Shaun Liam Graduate School of Biomedical Engineering Faculty of Engineering UNSW. "Cellular interaction in the cardiac pacemaker: a modelling study." Awarded by:University of New South Wales. Graduate School of Biomedical Engineering, 2005. http://handle.unsw.edu.au/1959.4/22512.
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In mammalian hearts, initiation of the heartbeat occurs in a region of specialised pacemaker cells known as the sinoatrial node (SAN). The SAN is a highly complex spatially distributed structure which displays considerable cellular heterogeneity and is subject to complex electrotonic interactions with the surrounding atrial tissue. In this study, biophysically detailed ionic models of central and peripheral SAN pacemaker cells are described. These models are able to accurately reproduce experimental recordings of the membrane potential from central and peripheral SAN tissue. These models are used to investigate frequency synchronisation of electrically coupled cardiac pacemaker cells. Based on simulation results presented, it is proposed that cellular heterogeneity in the SAN plays an important role in achieving rhythm coordination and possibly contributes to the efficient activation of the surrounding atrial myocardium. This represents an important, previously unexplored, mechanism underlying pacemaker synchronisation and cardiac activation in vivo. A spatial-gradient model of action potential heterogeneity within the SAN is then formulated using a large-scale least squares optimisation technique. This model accurately reproduces the smooth spatial variation in action potential characteristics observed in the SAN. One and two dimensional models of the intact SAN are then formulated and three proposed models of SAN heterogeneity are investigated: 1) the discrete-region model, in which the SAN consists of a compact central region surrounded by a region of transitional pacemaker cells, 2) the gradient model, in which cells of the SAN exhibit a smooth variation in properties from the centre to the periphery of the SAN, and 3) the mosaic model, in which SAN and atrial cells are scattered throughout the SAN region with the proportion of atrial cells increasing towards the periphery. Simulation results suggest that the gradient model achieves frequency entrainment more easily than the other models of SAN heterogeneity. The gradient model also reproduces action potential waveshapes and a site of earliest activation consistent with experimental observations in the intact SAN. It is therefore proposed that the gradient model of SAN heterogeneity represents the most plausible model of SAN organisation.
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Minoarivelo, Henintsoa Onivola. "Probabilistic modelling of the evolution of ecological interaction networks." Thesis, Stellenbosch : Stellenbosch University, 2011. http://hdl.handle.net/10019.1/17990.
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Thesis (MSc)--Stellenbosch University, 2011.ENGLISH ABSTRACT: In any ecological system, organisms need to interact with each other for their survival. Such interactions form ecological networks which are usually very complex. Nevertheless, they exhibit well de ned patterns; these regularities are often interpreted as products of meaningful ecological processes. As the networks are evolving through time, biological evolution is one of the factors that affects ecological network architecture. In this work, we develop a mathematical model that represents the evolution through time of such ecological interaction networks. The problem is approached by modelling network evolution as a continuous time Markov process, in such a way that the interactions in which a parent species is involved are potentially inherited by its descendant species. This approach allows us to infer ecological parameters and ecological network histories from real-world network data, as well as to simulate ecological networks under our model. While ecologists have long been aware of the in uence of evolutionary processes in shaping ecological networks, we are now able to evaluate the importance of such in uence.
AFRIKAANSE OPSOMMING: In enige ekologiese stelsel benodig organismes wisselwerkings met mekaar ten einde te oorleef. Sulke interaksies vorm ekologiese netwerke wat gewoonlik baie kompleks is maar nogtans goed-gede nieerde patrone vertoon. Hierdie patrone word dikwels geïnterpreteer as die produk van betekenisvolle ekologiese prosesse. Aangesien die netwerke met die verloop van tyd ontwikkel, is biologiese ewolusie een van die faktore wat ekologiese netwerkargitektuur beïnvloed. In hierdie studie ontwikkel ons 'n wiskundige model wat die ewolusie van sulke ekologiese interaksienetwerke voorstel. Die probleem word benader deur netwerkewolusie as 'n kontinue-tyd Markov-proses te modelleer, op so 'n manier dat die interaksies waarin 'n voorouerspesie betrokke is potensieel oorerf kan word deur die afstammelingspesies. Hierdie benadering laat ons toe om ekologiese parameters en ekologiese netwerkgeskiedenisse vanuit regte-wêreld data af te lei, sowel as om ekologiese netwerke onder ons model te simuleer. Alhoewel ekoloë al lank reeds bewus is van die invloed wat ewolusionêre prosesse het op die vorming van ekologiese netwerke, is ons nou in staat om die belangrikheid van hierdie invloed te evalueer.
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Formentin, Sara Mizar <1987>. "Neural network modelling of the wave-structure interaction processes." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amsdottorato.unibo.it/7001/.
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This thesis presents a new Artificial Neural Network (ANN) able to predict at once the main parameters representative of the wave-structure interaction processes, i.e. the wave overtopping discharge, the wave transmission coefficient and the wave reflection coefficient. The new ANN has been specifically developed in order to provide managers and scientists with a tool that can be efficiently used for design purposes.
The development of this ANN started with the preparation of a new extended and homogeneous database that collects all the available tests reporting at least one of the three parameters, for a total amount of 16’165 data. The variety of structure types and wave attack conditions in the database includes smooth, rock and armour unit slopes, berm breakwaters, vertical walls, low crested structures, oblique wave attacks.
Some of the existing ANNs were compared and improved, leading to the selection of a final ANN, whose architecture was optimized through an in-depth sensitivity analysis to the training parameters of the ANN. Each of the selected 15 input parameters represents a physical aspect of the wave-structure interaction process, describing the wave attack (wave steepness and obliquity, breaking and shoaling factors), the structure geometry (submergence, straight or non-straight slope, with or without berm or toe, presence or not of a crown wall), or the structure type (smooth or covered by an armour layer, with permeable or impermeable core).
The advanced ANN here proposed provides accurate predictions for all the three parameters, and demonstrates to overcome the limits imposed by the traditional formulae and approach adopted so far by some of the existing ANNs. The possibility to adopt just one model to obtain a handy and accurate evaluation of the overall performance of a coastal or harbor structure represents the most important and exportable result of the work.Questa tesi presenta una nuova Rete Neurale Artificiale (RNA) per la predizione dei principali parametri rappresentativi del processo di interazione onda-struttura: la portata di tracimazione ondosa e i coefficienti di trasmissione e riflessione ondosa. Il primo passo ha consistito nella raccolta e organizzazione dei dati disponibili in letteratura. Complessivamente, sono stati assemblati 16'165 dati in unico database omogeneo, includendo una vasta tipologia di opere, fra cui: strutture lisce e impermeabili, strutture permeabili in massi naturali o rivestite di unità artificiali in cemento, opere con e senza nucleo impermeabile, muri a parete verticale, strutture dalla geometria articolata da berme e/o protezioni al piede, strutture a cresta bassa, condizioni di attacco ondoso obliquo. L’assetto finale della RNA è stato definito mediante il confronto e il miglioramento di alcune delle reti esistenti, e in seguito a un’approfondita analisi di sensitività ai diversi parametri di calibrazione del modello. Ciascuno dei 15 parametri di ingresso della rete è finalizzato alla rappresentazione di un diverso aspetto dell’unico fenomeno dell’interazione onda-struttura, descrivendo la tipologia di attacco ondoso (ripidità e obliquità delle onde, indici di frangimento e di shoaling), la sezione geometrica (sommergenza, caratteristiche del paramento a mare, quali presenza o assenza di berme e protezioni al piede, presenza o meno di muro di coronamento) e il tipo di struttura (liscia, o rivestita di una mantellata di massi artificiali o naturali, con o senza nucleo impermeabile). La RNA produce stime accurate dei 3 parametri e supera i limiti imposti dalle formule tradizionali presenti in letteratura e dalle RNA esistenti, usualmente ottimizzate per la predizione di uno solo dei parametri. La possibilità di utilizzare un unico modello che fornisca una stima accurata e rapida della risposta idraulica di una struttura di difesa costiera o portuale alla sollecitazione ondosa rappresenta il risultato più importante ed esportabile di tale lavoro.
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Zheng, Yue. "Modelling, tracking and generating human interaction behaviours in video." Thesis, Cardiff University, 2009. http://orca.cf.ac.uk/54108/.
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Intelligent virtual characters are becoming increasingly popular in en tertainment, educational and simulation software. A virtual charac ter is the creation or re-creation of a human being in an image, using computer-generated imagery. It must act and react in the environment, drawing on the disciplines of automated reasoning and planning. Creating characters with human-like behaviours that respond interactively to a real person in a video, is still a serious challenge. There are several major reasons for this. First, human motion is very complex, which makes it particularly difficult to simulate. Second, the human form is also not straightforward to design due to the large number of degrees of freedom of the motion. Third, creating novel contextual movements for virtual characters in real time is a new research area.
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Tomasio, Susana de Miranda. "Modelling of the interaction between peptides and graphitic surfaces." Thesis, University of Warwick, 2010. http://wrap.warwick.ac.uk/34619/.
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The aim of this thesis is to understand the interactions of peptides with graphitic surfaces such as carbon nanotubes and graphite, in order to help establish guiding principles for the design of peptide sequences with controllable affinity to graphitic surfaces. Atomistic molecular dynamics (MD) simulations with our extended polarisable AMOEBAPRO force-field, which includes parameters for graphitic surfaces is used throughout. The peptide sequences studied were identified by phage-display experiments for their strong affinity to CNTs, and are rich in tryptophan and histidine residues [94]. The importance of the tryptophan residues on the binding affinity to CNTs is investigated by mutating each tryptophan by either tyrosine and phenylalanine. In addition, the effect of the surface curvature on the binding affinity is also explored. It is found that sequences containing tryptophan residues have more affinity to graphitic surfaces than those containing tyrosine or phenylalanine. Furthermore, it is suggested that these peptide sequences were selected for interfacial shape, since in the case of graphite, a compromise between having all the aromatic residues close to the surface and also allowing the non-aromatic residues to approach the surface is found. Following this study, the interaction of peptide sequences with CNTs is again studied, but this time with the aim to investigate the order of the residues, on the binding affinity to CNTs. The influence of the peptide sequence on the binding affinity to CNTs is studied by scrambling the sequence (HWKHPWGAWDTL). This study suggests that binding affinity is strongly dependent on the order of the content of the peptide sequences and gives some useful insights to the identification of principles that may help in the design of peptide sequences with controllable binding affinity to CNTs. For instance, it is found that strong binding may be due to the presence of isolated pairs of tryptophans, while weaker binding may be due to the presence of two tryptophan residues intercalated by another residue. The interactions of water with graphitic surfaces – CNTs, fullerenes and graphite – are also considered and it is found that the water structuring at the interface is weak and that there are no more than tree layers of structured water on the graphitic surfaces. Finally, the effect of the presence of OH defects on CNTs on the binding affinity to peptides is investigated. The results show that the binding affinity is not significantly affected by the presence of OH defects, but a general increase in the peptide mobility is noticed, giving insights for the applications of real CNTs with peptides. The work described in this thesis helps to understand what are the key residues involved in the interaction with CNTs, why do these key residues bind better to CNTs and provide insights on the mechanisms of peptided binding to CNTs, by demonstrating the role of peptide conformation.
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Seddon, Caroline Michelle. "Modelling transient dynamic fluid-structure interaction in aerospace applications." Thesis, University of Salford, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.492434.
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Although significant progress has been made in the study of dynamic loading of aircraft structures, several areas have been identified that require further research. In particular, attention is drawn to problems involving transient, dynamic fluid-structure interaction, where fluids play an important role, heavily influencing the response of the structure to the applied dynamic load. In this work the use of existing numerical modelling techniques for the evaluation of such problems is investigated.
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Azimi, Ali. "Wheel-soil interaction modelling for rover simulation and analysis." Thesis, McGill University, 2014. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=121231.
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Appropriate modelling of the interaction between wheel and terrain is a key element in simulating wheeled mobile robots and analyzing their functionality on soft terrain. In this thesis, two modelling approaches, with their implementation in a multi-body dynamics environment and their experimental validation, are introduced. The first approach is based on well-established semi-empirical terramechanics models. The multi-pass effect is considered in the implementation by storing terrain deformation and changes in hardening of soil under the wheel. A high-resolution height-field (HF) is used to model the terrain surface, with relevant information stored in the HF vertices. A novel framework is developed for implementation of this model in a multi-body dynamics environment. For every wheel in contact with soft soil, unilateral contact constraints are added to the solver in the normal direction. Terramechanics forces in the tangent plane and the resistant moment are formulated as set-valued functions associated with kinematic constraints on their complementary variables. The new formulation leads to the dynamics representation in the form of a linear complementarity problem. The properties of these constraints are set based on the soil reactions determined from the semi-empirical terramechanics model, at every time-step of the simulation. With this approach, fast and stable simulation is achieved. In the second approach, normal and shear stress distributions in the contact area are determined using continuum mechanics with a computationally efficient technique compared to finite element modelling. The author proposes a velocity field in the vicinity of the contact area motivated by the physical nature of the problem. Using this field, the incremental changes to the stress field are determined by resorting to classical elasto-plasticity theory and an appropriate constitutive relation for soil. As opposed to finite element approaches, which model the soil in contact with the wheel as a high-resolution mesh, our approach focuses on the wheel-soil contact patch only. This localized representation provides the basis for fast wheel-soil interaction modelling. By combining this approach with a height-field as terrain representation, elasto-plastic soil deformation and changes in the hardening state of soil are directly captured. In addition, because of the elasto-plastic representation for soil, energy dissipation during soil compaction is directly captured. The dynamic slip-sinkage behaviour of the wheel and the semi-elliptical shape of the normal stress distribution under the wheel are natural outcomes of the proposed model. The results obtained from the proposed approach are compared with experimental data available in the literature, which show good agreement between the model and experiments under various ranges of wheel slippage and loading conditions.Moreover, an extensive set of experiments was conducted using a version of the Juno rover (Juno II), owned by the Canadian Space Agency (CSA). The analysis of the results shows good agreement between the experimental rover behaviour and the simulation runs using both models developed.Afin de simuler et d'analyser les mouvements de robots mobiles (rovers) sur terrain déformable, il est essentiel de correctement modéliser les interactions entre les roues du véhicule et le terrain. Dans cette thèse, deux approches de modélisation seront présentées et analysées, avec leurs mises en œuvre dans un environnement de simulation en temps réel. La première approche est basée sur un modèle semi-empiriques de mécanique des sols. L'effet du passage répété d'un véhicule sur le terrain est pris en compte par le stockage de la déformation du terrain et du durcissement du sol sous les roues. Un champ de hauteur (Height Field) à haute résolution est utilisé pour modéliser la surface du terrain; les informations nécessaires sont stockées dans les sommets du champ de hauteur. Une approche originale est développée pour la mise en œuvre dans l'engin de simulation. Pour chaque roue en contact avec le sol mou, une contrainte de contact unilatéral est ajouté au solveur pour la direction normal au mouvement. Les forces dans le plan tangent, issus de la mécanique des sols, et la résistance au moment sont traités comme des fonctions multivaluées associées à des contraintes cinématique pour les variables complémentaires. Cette nouvelle formulation conduit à une représentation dynamique sous forme d'un problème de complémentarité linéaire. Les propriétés des contraintes sont définies en fonction des réactions du sol, calculées par le modèle semi-empirique à chaque pas de simulation. Avec cette approche, une simulation rapide et stable est obtenue. Dans la seconde approche, la répartition des contraintes normales et de cisaillement dans la zone de contact est déterminée en utilisant la mécanique des milieux continus avec une technique de calcul efficace par rapport à la modélisation par éléments finis. Nous proposons l'utilisation d'un champ de vitesses au voisinage de la zone de contact, dans une approche motivée par la nature physique du problème. Avec ce champ de vitesse, les changements progressifs du champ de contraintes sont calculées en recourant à la théorie d'élasto-plasticité classique et à une relation de comportement appropriée pour les sols. Contrairement aux approches par éléments finis, qui modélisent le sol en contact avec la roue comme un maillage haute résolution, notre approche est axée uniquement sur l'aire de contact roue-sol. En combinant cette approche avec un champ de hauteur comme représentation du terrain, la déformation élasto-plastique du sol et les changements dans le durcissement du sol sont directement pris en compte. En outre, en raison de la représentation élasto-plastique du sol, la dissipation d'énergie au cours du compactage du sol est aussi directement prise en compte. Le comportement dynamique de compaction et de glissement de la roue et la forme semi-elliptique de la répartition des contraintes normales sous la roue sont les résultats naturels du modèle proposé. Les résultats obtenus par cet approche sont comparés à des données disponibles dans des études expérimentales, et montre un bon accord avec la théorie pour un large domaine de valeur de glissement et de charge. En outre, un vaste ensemble d'expériences ont été menées en utilisant une version du rover Juno (Juno II) de l'Agence spatiale canadienne (ASC). L'analyse des résultats montre un bon accord entre le comportement expérimental des rovers et des simulations utilisant les deux modèles développés.
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Kiébré, Rimyalegdo. "Contribution to the modelling of aircraft tyre-road interaction." Phd thesis, Université de Haute Alsace - Mulhouse, 2010. http://tel.archives-ouvertes.fr/tel-00601774.
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This thesis is a part of the French national project called MACAO (Modélisation Avancée de Composants Aéronautiques et Outils associés). In collaboration with Messier-Dowty company (a landing gears manufacturer), the thesis has contributed to better understand the actual literature studies in the field of aircraft tyre-road interaction modelling and therefore, to help making an optimal choice of model for a specifie application. The objectives have been to propose models for representing the tyre behaviour on the ground with respect to the aircraft run types. Physical oriented models are preferred. To complete this study, a literature survey of the previous researches in tyre modelling for steadystate responses is first carried out. Then, based on the main factors playing an important role in tyre modelling, it is proposed a classification for the physical and the semi-empirical models, which are also investigated. Based on this classification, the study requirements and the measurement data constraints, an a priori choice of suitable models are studied. A further investigation of the tyre deformation at pure lateral slip is carried out. It has allowed to physically describe the mechanism of generation of the longitudinal component of the tyre force at pure lateral slip. This force is refened as induced longitudinal force. By taking this force into consideration, it has been possible to explain why the self-aligning moment can drop to zero before the tyre gets to full sliding at pure lateral slip. Besides, the sensitivity analysis is proposed as a means for determining the parameters that have most influence on the model output and thus, are responsible for the output uncertainty.
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HassabAllah, AbdulRahman Adam. "Modelling the interaction between rigid wheels and deformable soils." Thesis, University of Newcastle Upon Tyne, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.239236.
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Daniel, Gwenaelle Monique. "Optical and thermal transport modelling of laser-tissue interaction." Thesis, University of the West of England, Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392811.
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Stergiou, Christos. "A policy based framework for modelling agent interaction protocols." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415750.
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Welzel, Udo Siegfried. "Diffraction analysis of residual stress modelling elastic grain interaction /." Stuttgart : Univ, 2002. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB10221702.
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Chegancas, Rito Tiago Miguel. "Modelling and comparing protein interaction networks using subgraph counts." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:dcc0eb0d-1dd8-428d-b2ec-447a806d6aa8.
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The astonishing progress of molecular biology, engineering and computer science has resulted in mature technologies capable of examining multiple cellular components at a genome-wide scale. Protein-protein interactions are one example of such growing data. These data are often organised as networks with proteins as nodes and interactions as edges. Albeit still incomplete, there is now a substantial amount of data available and there is a need for biologically meaningful methods to analyse and interpret these interactions. In this thesis we focus on how to compare protein interaction networks (PINs) and on the rela- tionship between network architecture and the biological characteristics of proteins. The underlying theme throughout the dissertation is the use of small subgraphs – small interaction patterns between 2-5 proteins. We start by examining two popular scores that are used to compare PINs and network models. When comparing networks of the same model type we find that the typical scores are highly unstable and depend on the number of nodes and edges in the networks. This is unsatisfactory and we propose a method based on non-parametric statistics to make more meaningful comparisons. We also employ principal component analysis to judge model fit according to subgraph counts. From these analyses we show that no current model fits to the PINs; this may well reflect our lack of knowledge on the evolution of protein interactions. Thus, we use explanatory variables such as protein age and protein structural class to find patterns in the interactions and subgraphs we observe. We discover that the yeast PIN is highly heterogeneous and therefore no single model is likely to fit the network. Instead, we focus on ego-networks containing an initial protein plus its interacting partners and their interaction partners. In the final chapter we propose a new, alignment-free method for network comparison based on such ego-networks. The method compares subgraph counts in neighbourhoods within PINs in an averaging, many-to-many fashion. It clusters networks of the same model type and is able to successfully reconstruct species phylogenies solely based on PIN data providing exciting new directions for future research.
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Ilyina, Vera. "FDTD modelling of light interaction with liquid crystal devices." Thesis, University of Southampton, 2006. https://eprints.soton.ac.uk/45964/.
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This thesis is devoted to the application of the Finite Difference Time Domain (FDTD) method for describing light interaction with liquid crystal media. This method has been known in the electromagnetic community since 1966, but has so far only found limited application in liquid crystal optics. The thesis consists of four parts. In the first part of the thesis I extend the conventional FDTD algorithm to be used for studying anisotropic media with continuous spatial variations of the dielectric properties. In the second part I discuss tests of the algorithm and software on various dielectric systems with known response. The third and the fourth parts of the thesis are concerned with the nonlinear interaction between light and liquid crystals. In the third part I develop a FDTD self-consistent algorithm that takes into account the coupling between light and liquid crystal orientation. The algorithm is used to simulate the optical Freedericksz transition in a homeotropic liquid crystal cell. I find that solving the problem self-consistently significantly modifies the main characteristics of the transition. In the fourth part I use the liquid crystal FDTD algorithm to investigate the birth of optical singularities. The results are compared to a recent analytical theory. I find that the analytic theory is only qualitatively useful except in the extreme short wave limit.
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Taylor, Richard. "Finite element modelling of three dimensional fluid-structure interaction." Thesis, Swansea University, 2013. https://cronfa.swan.ac.uk/Record/cronfa42308.
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This work is focused on the numerical modelling of fluid-structure interaction in three dimensions. Both internal and external laminar flow around flexible bodies are considered. The fluid flow simulated is based on the incompressible Navier-Stokes equations and the general focus is on laminar Newtonian flow. The streamline upwind/ pressure stabilising Petrov-Galerkin (SUPG/PSPG) method is employed to achieve a stable low order finite element discretisation of the fluid, while the solid is discretised spatially by a standard Galerkin finite element approach. The behavior of the solid is governed by Neo-Hooke elasticity. For temporal discretisation the discrete implicit generalised-alpha method is employed for both the fluid and the solid domains. The motion of the fluid mesh is solved using an arbitrary Lagrangian-Eulerian (ALE) scheme employing a nonlinear pseudo-elastic mesh update method. The fluid-solid interface is modelled using a finite element interpolation method that allows for non-matching meshes and satisfies the required conservation laws. The resulting sets of fully implicit strongly coupled nonlinear equations are then decomposed into a general framework consisting of fluid, interface and solid domains. These equations are then solved using different solution techniques consisting of strongly coupled monolithic Newton and block Gauss-Seidel methods as well as a weakly coupled novel staggered scheme. These solvers are employed to solve a number of three dimensional numerical examples consisting of: External flow: o a soft elastic beam fixed at both ends o a thin cantilever plate.
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Guadarrama, Lara Rodrigo. "Modelling fluid-structure interaction problems with coupled DEM-LBM." Thesis, University of Leeds, 2017. http://etheses.whiterose.ac.uk/17444/.
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When studying the properties and behaviour of particulate systems, a multi-scale approach is an efficient way to describe interactions at different levels or dimensions; this means that phenomena taking place at one scale will inherently impact the properties and behaviour of the same system in a different scale. Numerical representation and simulation of fluid-structure interaction (FSI) systems is of particular interest in the present work. Conventional computational fluid dynamics (CFD) methods involve a top-down approach based on the discretisation of the macroscopic continuum Navier-Stokes equations; cells are typically much larger than individual particles and the hydrodynamic force is calculated for all the solid particles contained in singular a cell. Unlike traditional CFD solvers, the lattice Boltzmann method (LBM) is an alternative approach to simulate fluid flows in complex geometries in a mesoscale level. In LBM the fluid is deemed as a collection of cells, each one containing a particle that represents a density distribution function with a velocity field. The distinct element method (DEM) is in charge of handling the motion of particles and calculating the interparticle contact forces. The two methodologies LBM and DEM were selected among the available approaches to be combined in a single computational code to represent FSI systems. The key task to undertake was the implementation of a coupling code to exchange information between the two solvers LBM and DEM in a correct and efficient manner. The calculation of hydrodynamic forces exerted by the fluid on the particles is the major challenge in coupled FSI simulations. This was addressed by including the momentum exchange method, based on the link bounce-back technique, together with the immersed boundary method to deal with moving particles immersed in a fluid. In addition, in order to better understand the dynamics of FSI systems in a mesoscale level, the present work paid special attention to the accurate representation of individual particles displaying irregular geometries instead of the preferred spherical particles. This goal was achieved by means of X-ray microtomography digitisation of particles, allowing the capture of complex micro-structural features such as particle shape, texture and porosity. In this way a more realistic particle representation was achieved, extending its use to the implementation into computational simulations. The DEM-LBM coupling implementation carried out was tested quantitatively and qualitatively based on theoretical models and experimental data. Different cases were selected to simulate the dynamic process of packing particles, particle fluidisation and segregation, particles sedimentation, fluid permeability calculations and fluid flow through porous media. Results and predictions from simulations for a number of configurations showed good agreement when compared with analytical and experimental data. For instance, the relative error in terminal velocity of a non-spherical particle settling down in a column of water was 4.2%, showing an asymptotic convergence to the reference value. In different tests like the drag on two interacting particles and the flow past a circular cylinder at Re = 100, the corresponding deviations from the references published were 20% and 8.23% respectively. The extended Re range for the latter case followed closely the reference curve for the case of a rough cylinder, indicating the effects of the inherent staircase-like boundary in digital particles. Three dimensional simulations of applications such as fluidisation and sedimentation showed the expected behaviour, not only for spherical particles but also considering complex geometries such as sand grains. A symmetric array of spheres and randomly mixed particles were simulated successfully. Segregation was observed in a case configured with particles with different size and density. Hindered settling was also observed causing the slow settling of the small particles. Incipient fluidisation of spherical and irregular geometries was observed in relatively large computational domains. However, the minimum fluidisation velocity configured at the inlet was commonly 10 times larger than the calculated from the Ergun equation.
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Joosten, Martina Maria. "Aspects of interface modelling in fluid-structure interaction problems." Thesis, Swansea University, 2011. https://cronfa.swan.ac.uk/Record/cronfa42211.
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Different aspects of computational fluid-structure interaction are considered in this work. A brief introduction to fluid dynamics, structural mechanics and the finite element method is given, followed by an overview of interface modelling and the different solution strategies available for the coupling of the domains. A number of time integration schemes are explained in detail with a focus on their stability and accuracy properties. A model problem is introduced to investigate the situation where different domains of a coupled problem are solved with different time integration schemes. It is shown that appropriate interpolation of the solution variables at the interface is required to maintain the stability and accuracy properties of the individual time integration schemes. The Gauss-Seidel solution strategy is analysed in detail. Stability limitations are investigated and are shown to be related to the mass ratio between the different domains. Different relaxation strategies are introduced to improve the convergence behaviour. Finally, a number of 2D fluid-structure interaction examples are considered, in order to compare the different solution strategies.
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Ionascu, Beatrice. "Modelling user interaction at scale with deep generative methods." Thesis, KTH, Skolan för elektroteknik och datavetenskap (EECS), 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-239333.
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Understanding how users interact with a company's service is essential for data-driven businesses that want to better cater to their users and improve their offering. By using a generative machine learning approach it is possible to model user behaviour and generate new data to simulate or recognize and explain typical usage patterns. In this work we introduce an approach for modelling users' interaction behaviour at scale in a client-service model. We propose a novel representation of multivariate time-series data as time pictures that express temporal correlations through spatial organization. This representation shares two key properties that convolutional networks have been built to exploit and allows us to develop an approach based on deep generative models that use convolutional networks as backbone. In introducing this approach of feature learning for time-series data, we expand the application of convolutional neural networks in the multivariate time-series domain, and specifically user interaction data. We adopt a variational approach inspired by the β-VAE framework in order to learn hidden factors that define different user behaviour patterns. We explore different values for the regularization parameter β and show that it is possible to construct a model that learns a latent representation of identifiable and different user behaviours. We show on real-world data that the model generates realistic samples, that capture the true population-level statistics of the interaction behaviour data, learns different user behaviours, and provides accurate imputations of missing data.Förståelse för hur användare interagerar med ett företags tjänst är essentiell för data-drivna affärsverksamheter med ambitioner om att bättre tillgodose dess användare och att förbättra deras utbud. Generativ maskininlärning möjliggör modellering av användarbeteende och genererande av ny data i syfte att simulera eller identifiera och förklara typiska användarmönster. I detta arbete introducerar vi ett tillvägagångssätt för storskalig modellering av användarinteraktion i en klientservice-modell. Vi föreslår en ny representation av multivariat tidsseriedata i form av tidsbilder vilka representerar temporala korrelationer via spatial organisering. Denna representation delar två nyckelegenskaper som faltningsnätverk har utvecklats för att exploatera, vilket tillåter oss att utveckla ett tillvägagångssätt baserat på på djupa generativa modeller som bygger på faltningsnätverk. Genom att introducera detta tillvägagångssätt för tidsseriedata expanderar vi applicering av faltningsnätverk inom domänen för multivariat tidsserie, specifikt för användarinteraktionsdata. Vi använder ett tillvägagångssätt inspirerat av ramverket β-VAE i syfte att lära modellen gömda faktorer som definierar olika användarmönster. Vi utforskar olika värden för regulariseringsparametern β och visar att det är möjligt att konstruera en modell som lär sig en latent representation av identifierbara och multipla användarbeteenden. Vi visar med verklig data att modellen genererar realistiska exempel vilka i sin tur fångar statistiken på populationsnivå hos användarinteraktionsdatan, samt lär olika användarbeteenden och bidrar med precisa imputationer av saknad data.
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Lissauer, Samantha Mary. "Modelling hepatitis C viral host interaction and co-infection." Thesis, University of Birmingham, 2018. http://etheses.bham.ac.uk//id/eprint/8774/.
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Hepatitis C Virus (HCV) is a clinically important infection that leads to chronic liver disease and Human Immunodeficiency Virus (HIV) co-infected patients have more rapid progression to severe liver disease and show higher rates of HCV vertical transmission. Hepatocytes are a highly differentiated cell type and support low level HCV replication. Most studies of the viral life cycle use de-differentiated hepatoma cell lines, which are highly permissive. The mechanism behind this difference is poorly understood. We show that dimethylsulfoxide (DMSO) differentiated Huh-7 cells have a 100-fold reduction in permissivity to HCV infection. We confirm that these cells are differentiated and upregulate key liver specific markers including miR122. They are metabolically active and have intact innate signaling pathways in response to infection. We observed a 10-fold reduction in the initiation of replication and a 10-fold loss in extra-cellular particle infectivity. In contrast cell-to-cell dissemination rates were comparable and cell-contact dependent infection of differentiated cells can overcome the restrictions seen in cell-free infection. HCV cell-to-cell transmission can also be mediated by other cell types. T cells are the primary cell supporting HIV-1 infection. We have shown that HCV can bind primary and immortalized T cells and trans-infect hepatoma cells. This requires replicating HIV but is independent of co-receptor engagement. HIV-1 infection of CD4+ T cells induces a significant increase in HCV trans-infection by increased viral binding. T cells provide a vehicle for HIV-1 to promote HCV infectivity, transmission and persistence.
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Paulov, Ján. "Towards Comparison of Two Entropy Formulae." WU Vienna University of Economics and Business, 1996. http://epub.wu.ac.at/4173/1/WSG_DP_5196.pdf.
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The basic objective of this paper is to compare two entropy formulae used as objective functions in spatial
intreraction modelling. This is carried out by comparing some attributes of the interaction models derived from
both of them. The comparison results in the design of the third formula, which, however, represents a slight
modification of one of them. (author's abstract)Series: Discussion Papers of the Institute for Economic Geography and GIScience
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Tzanavari, Aimilia. "User modeling for intelligent human-computer interaction." Thesis, University of Bristol, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.364961.
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