Дисертації: "Stress modelling"

1

Jenter, Harry Leonard. "Modelling bottom stress in depth-averaged flows." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/58501.

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Thesis (Ph. D.)--Joint Program in Oceanographic Engineering (Massachusetts Institute of Technology, Dept. of Civil Engineering; and the Woods Hole Oceanographic Institution), 1989.
Includes bibliographical references (leaves 140-145).
The relationship between depth-averaged velocity and bottom stress for wind-driven flow in unstratified coastal waters is examined here. The adequacy of traditional linear and quadratic drag laws is addressed by comparison with a 2 1/2-D model. A 2 1/2-D model is one in which a simplified 1-D depth-resolving model (DRM) is used to provide an estimate of the relationship between the flow and bottom stress at each grid point of a depth-averaged model (DAM). Bottom stress information is passed from the DRM to the DAM in the form of drag tensor with two components: one which scales the flow and one which rotates it. This eliminates the problem of traditional drag laws requiring the flow and bottom stress to be collinear. In addition, the drag tensor field is updated periodically so that the relationship between the velocity and bottom stress can be time-dependent. However, simplifications in the 2 1/2-D model that render it computationally efficient also impose restrictions on the time-scale of resolvable processes. Basically, they must be much longer than the vertical diffusion time scale. Four progressively more complicated scenarios are investigated. The important factors governing the importance of bottom friction in each are found to be 1) non-dimensional surface Ekman depth ... is the surface shear velocity, f is the Coriolis parameter and h is the water depth 2) the non-dimensional bottom roughness, zo/h where zo is the roughness length and 3) the angle between the wind stress and the shoreline. Each has significant influence on the drag law. The drag tensor magnitude, r, and the drag tensor angle, 0 are functions of all three, while a drag tensor which scales with the square of the depth-averaged velocity has a magnitude, Cd, that only depends on zo/h. The choice of drag law is found to significantly affect the response of a domain. Spin up times and phase relationships vary between models. In general, the 2 1/2-D model responds more quickly than either a constant r or constant Cd model. Steady-state responses are also affected. The two most significant results are that failure to account for 0 in the drag law sometimes leads to substantial errors in estimating the sea surface height and to extremely poor resolution of cross-shore bottom stress. The latter implies that cross-shore near-bottom transport is essentially neglected by traditional DAMs.
by Harry Leonard Jenter, II.
Ph.D.

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2

Thomson, Stuart. "Mathematical modelling of elastoplasticity at high stress." Thesis, University of Oxford, 2017. http://ora.ox.ac.uk/objects/uuid:a7d565c6-abeb-4932-8c1e-aebc38da7584.

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This thesis is concerned with the mathematical modelling of elastic-plastic deformation in regimes of stress far exceeding the yield stress. Such scenarios are typically encountered in violent impact testing, where millimetre-thick samples of metal are subjected to pressures on the order of the bulk modulus of the material. We begin with an overview of violent impact testing, with particular attention paid to a specific class of experiments known as isentropic compression experiments (ICEs), which will provide motivation for the mathematical modelling and analysis in subsequent chapters. In chapter 2, by appealing to sound notions from rational mechanics and thermodynamics, we construct a mathematical model which aims to encapsulate the essential phenomena involved in violent elastic-plastic deformation. This is followed in chapter 3 with a numerical analysis of the mathematical model in uniaxial strain, which is the geometry relevant ICEs. In chapters 4 and 5, we corroborate the observations made in chapter 3 via a systematic mathematical analysis. In particular, our focus will be on the elastic and plastic waves that can propagate through finite metal samples during isentropic compression. Finally, in chapter 6, we explore the applicability of our model to other geometries, specifically the radially axisymmetric expansion of a circular cavity embedded in an infinite elastic-plastic medium. We conclude with a summary of our findings and suggest some avenues for future investigation.

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3

Solowski, Wojciech Tomasz. "Unsaturated soils : constitutive modelling and explicit stress integration." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2083/.

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4

Haque, Mainul. "Mathematical modelling of eukaryotic stress-response gene networks." Thesis, University of Nottingham, 2012. http://eprints.nottingham.ac.uk/12509/.

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Mathematical modelling of gene regulatory networks is a relatively new area which is playing an important role in theoretical and experimental investigations that seek to open the door to understanding the real mechanisms that take place in living systems. The current thesis concentrates on studying the animal stress-response gene regulatory network by seeking to predict the consequence of environmental hazards caused by chemical mixtures (typical of industrial pollution). Organisms exposed to pollutants display multiple defensive stress responses, which together constitute an interlinked gene network (the Stress-Response Network; SRN). Multiple SRN reporter-gene outputs have been monitored during single and combined chemical exposures in transgenic strains of two invertebrates, Caenorhabditis elegans and Drosophila melanogaster. Reporter expression data from both species have been integrated into mathematical models describing the dynamic behaviour of the SRN and incorporating its known regulatory gene circuits. We describe some mathematical models of several types of different stress response networks, incorporating various methods of activation and inhibition, including formation of complexes and gene regulation (through several known transcription factors). Although the full details of the protein interactions forming these types of circuits are not yet well-known, we seek to include the relevant proteins acting in different cellular compartments. We propose and analyse a number of different models that describe four different stress response gene networks and through a combination of analytical (including stability, bifurcation and asymptotic) and numerical methods, we study these models to gain insight on the effect of several stresses on gene networks. A detailed time-dependent asymptotic analysis is performed for relevant models in order to clarify the roles of the distinct biochemical reactions that make up several important proteins production processes. In two models we were able to verify the theoretical predictions with the corresponding laboratory experimental observations that carried out by my coworkers in Britain and India.

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5

Hicks, Michael A. "Numerically modelling the stress-strain behaviour of soils." Thesis, University of Manchester, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.256573.

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6

Radmaneshfar, Elahe. "Mathematical modelling of the cell cycle stress response." Thesis, University of Aberdeen, 2012. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=192232.

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7

Karschau, Jens. "Mathematical modelling of chromosome replication and replicative stress." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=202763.

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Previous theoretical work on DNA replication neglected how the starting points (origins) take their place and how replication time is a ected when origins fail to activate. It is however crucial that origin loci are chosen so that too large gaps between them are avoided; otherwise the time until completion of chromosome replication becomes much longer than is allowed by the cell cycle. We investigate what the optimal origin location should be depending on the likelihood of origins failing. We show analytically and numerically that there exist regimes for origins, either to be positioned together in groups spaced far away from the next, or as equally scattered single origins depending on the uncertainty when activation occurs. The model reproduces origin distributions of frog embryos which are thought to be random, and shows contrarily that grouping must occur in order to swiftly complete replication; known as the random completion problem. The model also holds when considering a circular DNA topology for archaeal genomes, as well as if applied to the whole replication pro ling data of yeast. We study how an optimal origin distribution can arise and propose a mechanism to solve the random completion problem. We show that regular spacing emerges as an inherent property of the car parking model. We introduce a spatial requirement for origins to bind to DNA; origins occupy space on the DNA and can only bind stably if there is su cient space for them. Such a model leads to a well ordered origin distribution with minimal gaps as required for on time DNA replication in frog embryos. The optimal origin distribution emerges directly from our model because origins have a higher chance to bind to large empty regions instead of small once, therefore destroying large inter origin gaps. We also introduce a model to account for the interaction of replication forks with each other which leads to their assembly into replication factories. We show using Boltzmann statistics that their assembly is stochastic. A rst model only considers two pairs of forks which we then extend to describe properties of measured experimental distributions such as fork numbers per factory during on a whole yeast genome approach. Our in silico distribution of forks per factory matches in vivo data well; which suggests that active forks encounter each other randomly for an association into replication factories.

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8

Lykostratis, K. "Mathematical modelling of shear stress signalling in endothelial cells." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1445634/.

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In recent years it has become clear that cell signalling pathways are not simple linear chains of events as was once thought but frequently diverge, converge and employ positive and negative feedback. As a result signals show a complex pattern of spatial and temporal activity that is difficult to explain despite a wealth of experimental data. Systems Biology attempts to predict and understand the behaviour of complex systems by integrating information from diverse sources and principles drawn from a large number of different scientific disciplines. The signalling pathways regulating endothelial responses to shear stress have been extensively studied, since perturbed fluid flow contributes significantly to the development of heart disease. Shear stress activates many signals in endothelial cells, from ion influxes to protein phosphorylation and gene expression, and induces changes in endothelial morphology. Here a modelling and Systems Biology approach was taken to investigate and understand better the endothelial signal transduction networks that convert fluid flow stimulation into biochemical signals. A static signal transduction network was built from integrin cell surface receptors to activation of the tyrosine kinases focal adhesion kinase (FAK) and Src. Parameters for each reaction in this network were collected from the literature or, when necessary, estimated. To model how fluid flow initiates signalling in this network, the shear stress-induced calcium influx and the viscoelastic response of transmembrane receptors such as integrins to mechanical force were examined by means of mathematical modelling, using ordinary differential equations. These effects were used as primary activators of the shear stress response in endothelial cells, allowing quantitative analysis of the intracellular signal transduction flow which propagates from integrin to paxillin, FAK and Src activation. The magnitude and dependencies of each influence were examined individually and in conjunction with each other. The model was used to investigate the role and dynamic regulation of previously unstudied molecules in the network and the simulated results were compared against experimental data in order to validate hypotheses and increase our understanding of the molecular processes underlying the shear stress response.

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9

Lamb, Angharad. "Mathematical Modelling of the Biological Stress Response to Chronium." Thesis, University of Nottingham, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.517846.

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10

Roth, Hugh. "Fundamental modelling of single crystal nickel superalloy yield stress." Thesis, University of Cambridge, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.627177.

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11

Stefanatos, Rhoda Katerina Anne. "Modelling tumourigenesis and the stress response in Drosophila melanogaster." Thesis, University of Glasgow, 2013. http://theses.gla.ac.uk/4865/.

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12

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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13

Aldakheel, Yousef Yacoub. "Remote sensing of crop water stress : measurements and modelling." Thesis, University of Salford, 1998. http://usir.salford.ac.uk/43021/.

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14

Salvati, Enrico. "Residual stress evaluation and modelling at the micron scale." Thesis, University of Oxford, 2017. https://ora.ox.ac.uk/objects/uuid:b737925e-a200-4a61-87f1-0d834d642d7b.

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The presence of residual stresses in engineering components may significantly affect damage evolution and progression towards failure. Correct evaluation of residual stress is of crucial importance for assessing mechanical components, predicting response and ensuring reliability. For example, when failure occurs due to cyclic loading, the underlying damage begins at the nano-, and then micro-scale. It is clear that improving engineering reliability at the micro-scale requires the ability to evaluate residual stress and mechanical properties at the appropriate scale. The key objective of the thesis is to advance the understanding and practice of residual stress evaluation at the micro-scale, and to examine the implications and applications that follow. Significant effort was devoted to the evaluation of two aspects of the relatively novel FIB-DIC micro-ring-core experimental technique: assessing the effects of Ga-ion damage and the quantification of uncertainty in stress evaluation due to unknown crystal orientation. FIB-DIC micro-ring-core milling was then used alongside with synchrotron XRD to study residual stress effects on fatigue crack growth propagation rate following the occurrence of overload or underload. The effects of the two principal mechanisms of crack retardation following an overload, residual stress and crack closure, were separated by testing samples at different loading ratios. Whilst, the acceleration after an underload was studied using validated non-linear FEM analyses. Conceptual focus was placed on the macro-micro-nano residual stress decomposition into Type I, II & III according to scale and, detailed examination was conducted experimentally and numerically. In the context of shot-peening surface treatment, residual stresses were modelled using a novel eigenstrain-based modelling procedure for arbitrarily shaped components. Furthermore, a fine scale characterisation was performed of the recast layer produced by EDM, with particular attention paid to the residual stress. The investigations presented in this thesis open new perspectives for the assessment of material reliability. Improved failure prediction models will be elaborated based on the insights obtained in the present study.

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15

Shuttle, Dawn Alison. "Numerical modelling of localisation in soils." Thesis, University of Manchester, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.277841.

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16

Nilsson, Cecilia. "Modelling of Dynamically Loaded Shotcrete." Thesis, KTH, Betongbyggnad, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-36923.

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17

Dzomeku, Israel K. "Modelling seed dormancy, germination and emergence of Striga hermonthica." Thesis, University of Reading, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252261.

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18

Bayliss, Martin. "The numerical modelling of elastomers." Thesis, Cranfield University, 2003. http://hdl.handle.net/1826/87.

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This thesis reports onreview and research work carried out on the numerical analysis of elastomers. The two numerical techniques investigated for this purpose are the finite and boundary element methods. The finite element method is studied so that existing theory is used to develop a finite element code both to review the finite element method as applied to the stress analysis of elastomers and to provide a comparison of results and numerical approach with the boundary element method. The research work supported on in this thesis covers the application of the boundary element method to the stress analysis of elastomers. To this end a simplified regularization approach is discussed for the removal of strong and hypersingularities generated in the system on non-linear boundary integral equations. The necessary programming details for the implementation of the boundary element method are discussed based on the code developed for this research. Both the finite and boundary element codes developed for this research use the Mooney-Rivlin material model as the strain energy based constitutive stress strain function. For validation purposes four test cases are investigated. These are the uni-axial patch test, pressurized thick wall cylinder, centrifugal loading of a rotating disk and the J-Integral evaluation for a centrally cracked plate. For the patch test and pressurized cylinder, both plane stress and strain have been investigated. For the centrifugal loading and centrally cracked plate test cases only plane stress has been investigated. For each test case the equivalent results for an equivalent FEM program mesh have been presented. The test results included in this thesis prove that the FE and BE derivations detailed in this work are correct. Specifically the simplified domain integral singular and hyper-singular regularization approach was shown to lead to accurate results for the test cases detailed. Various algorithm findings specific to the BEM implementation of the theory are also discussed.

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19

Alkathafi, Maftah Hussien Abdulgader. "Modelling of carbonate-bicarbonate stress corrosion cracking of pipeline steels." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498675.

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This research work has been concerned with the physical and numerical modelling of the conditions developed under disbonded coatings on steel, with a view to understanding the processes responsible for the conditions that lead to carbonate-bicarbonate stress corrosion cracking. The physical model has used a polyethylene coating covering a crevice of controlled thickness, with a controlled gas connposition (air with 1% CO₂) on the exterior of the coating. An optical fibre chemical sensor was developed to monitor the pH at locations along the crevice, and the potential has been monitored at the same locations using salt-bridge to conventional reference electrodes. A mathematical model of the same system has been developed using a commercial finite element package. The model was based on a one-dimensional crevice and results have been obtained for a high and a low permeability of coating. The results showed that the permeability of the coating plays an important role in controlling the conditions at the end of the crevice. At a high h permeability of coating the gas transport through the coating creates more alkaline solution inside the crevice, the generation of hydroxyl ions due to the oxygen reduction reaction increasing the pH. With a low permeability coating, no gas diffusion through the coating occurs, and the solution inside the crevice becomes less alkaline where the iron dissolution reaction takes place. So the pH and potential inside the crevice with a high permeability coating were greater than with the low permeability coating. In addition, the carbonate and bicarbonate ion concentrations were also higher with the high permeability coating. The results of this model were in good agreement with the physical model and with mathematical models reported in the literature.

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20

Richardson, G. A. "Algebraic stress modelling for shock-wave/turbulent boundary-layer interactions." Thesis, Cranfield University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267213.

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21

Kan, Chui-Chui Flora. "Modelling the behaviour of a process control operator under stress." Thesis, City University London, 1992. http://openaccess.city.ac.uk/14854/.

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In this study, a framework to model the effects of stress on a process control operator is proposed. There exists many cognitive models, each of which attempts to model a specific class of human behaviour. One major effect of stress is the cause of errors, both physical and cognitive. In order to model the effects of stress, two cognitive models, a cognitive model of human errors and a cognitive model of process control operators are examined in detail. In this thesis, the basic functions of the human cognitive system, its organization and a cognitive model of error commission are first examined. The behaviour of a process control operator and a cognitive model of the behaviour of the operator are then discussed. The known effects of stress on the process control operator's behaviour are described and a framework for modelling the behaviour of process control operators under stress is proposed. The inadequacies associated with existing cognitive models for process control operators are explained and a modified cognitive model is proposed, which takes into account the cognitive model of error. Finally, an architecture design for the implementation of the cognitive model is provided and suggestions for the next step forward are proposed.

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22

Isiaka, Fatima. "Modelling stress levels based on physiological responses to web contents." Thesis, Sheffield Hallam University, 2017. http://shura.shu.ac.uk/16551/.

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Capturing data on user experience of web applications and browsing is important in many ways. For instance, web designers and developers may find such data quite useful in enhancing navigational features of web pages; rehabilitation therapists, mental-health specialists and other biomedical personnel regularly use computer simulations to monitor and control the behaviour of patients. Marketing and law enforcement agencies are probably two of the most common beneficiaries of such data - with the success of online marketing increasingly requiring a good understanding of customers' online behaviour. On the other hand, law enforcement agents have for long been using lie detection methods - typically relying on human physiological functions - to determine the likelihood of falsehood in interrogations. Quite often, online user experience is studied via tangible measures such as task completion time, surveys and comprehensive tests from which data attributes are generated. Prediction of users' stress level and behaviour in some of these cases depends mostly on task completion time and number of clicks per given time interval. However, such approaches are generally subjective and rely heavily on distributional assumptions making the results prone to recording errors. We propose a novel method - PHYCOB I - that addresses the foregoing issues. Primary data were obtained from laboratory experiments during which forty-four volunteers had their synchronized physiological readings - Skin Conductance Response, Skin Temperature, Eye tracker sensors and users activity attributes taken by a specially designed sensing device. PHYCOB I then collects secondary data attributes from these synchronized physiological readings and uses them for two purposes. Firstly, naturally arising structures in the data are detected via identifying optimal responses and high level tonic phases and secondly users are classified into three different stress levels. The method's novelty derives from its ability to integrate physiological readings and eye movement records to identify hidden correlates by simply computing the delay for each increase in amplitude in reaction to webpages contents. This addresses the problem of latency faced in most physiological readings. Performance comparisons are made with conventional predictive methods such as Neural Network and Logistic Regression whereas multiple runs of the Forward Search algorithm and Principal Component Analysis are used to cross-validate the performance. Results show that PHYCOB I outperforms the conventional models in terms of both accuracy and reliability - that is, the average recoverable natural structures for the three models with respect to accuracy and reliability are more consistent within the PHYCOB I environment than with the other two. There are two main advantages of the proposed method - its resistance to over-fitting and its ability to automatically assess human stress levels while dealing with specific web contents. The latter is particularly important in that it can be used to predict which contents of webpages cause stress-induced emotions to users when involved in online activities. There are numerous potential extensions of the model including, but not limited to, applications in law enforcement - detecting abnormal online behaviour; online shopping (marketing) - predicting what captures customers attention and palliative in biomedical application such as detecting levels of stress in patients during physiotherapy sessions.

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23

Li, Xiangqian. "Modelling stress and damage interaction in fibre reinforced composite laminates." Thesis, University of Bristol, 2009. http://hdl.handle.net/1983/ac610f80-ded7-4d51-b390-5c6548e5c3cd.

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24

Friedrich, Anett, Astrid Ziemann, and Uwe Schlink. "Measurement and modelling of the cumulated thermal stress in Leipzig." Universität Leipzig, 2010. https://ul.qucosa.de/id/qucosa%3A16364.

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This paper shows first results of mobile measurements, which carried out in summer 2009 to evaluate the thermal comfort for a „standardized‟ pedestrian in several urban areas of Leipzig. The analysis of the obtained data was conducted by calculating the mean radiant temperature as well as the Predicted Mean Vote (PMV). The results were compared to simulations applying the RayMan-program. Additionally to these findings to short-term stress, a study to the cumulated thermal stress was implemented into the analysis for the first time. Thereby, the thermal stress was considered which is perceived by a healthy ‟standardized‟ person during a one hour walk. As a first step a time rate of change of the PMV was defined for a measurement period. Using the example of the 20th August, 2009 in Leipzig, urban district Lößnig, a cumulated PMVaggregation of 0.7 was calculated and hence, a total (cumulated) PMV of 3.4 results in comparison to an arithmetically averaged PMV of only 2.7 for all measurement points along the route that were taken that day. Thus, a person perceives a severe thermal stress when walking the typical pedestrian route in Leipzig-Lößnig in one hour.

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25

Abolghasemi, Sobhan. "Materials selection, stress analysis and CFD modelling of flare tips." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9540.

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Oil and gas platforms, refineries and chemical plants need to burn off the excess gas resulting from pressure variations during production. The failure of flare tips, sometimes with short lifetimes, has been a major cause for concern in the oil and gas industry for many years. The aim of this study was to evaluate and improve the performance of flare tips. The study has been approached from two perspectives: (i) material requirements, identifying the most suitable alloys for use in flare tips, and (ii) design optimisation, aimed at the development of a flare tip that minimises interaction with flame, therefore giving lower operating temperatures and longer lifetimes. The thesis also includes an Infra-Red (IR) thermal imaging study to establish flare tip temperature profiles during flaring. Examination of failed flare tips has provided evidence of intergranular oxidation and stress corrosion cracking as possible failure mechanisms. A study of the effect of thermal shock on the oxidation resistance of alloys 800H and 625, currently used in flare tips, is presented. The embrittlement of alloy 625 in the range 650 °C to 800 °C has also been investigated. Thermal imaging of three flares in operation has indicated metal temperatures of up to 1000 °C, above levels that can be sustained by alloys currently in use. A Finite Element model of stress distributions based on the temperature profiles has been developed. It was concluded that flare tip lifetimes would be limited by a combination of creep and fatigue of the support brackets, and by plastic deformation at the top of the windshield. The model successfully predicted the failure of two flare tips and lead to a timely replacement, resulting in significant financial savings and the prevention of catastrophic failure. Commercial Computational Fluid Dynamics software, that solves the Navier-Stokes equation combined with a combustion model, has been used to assess the effect of gas flow rates and wind conditions on combustion behaviour and the resulting operating temperatures of flare tips. The model has been validated with data obtained from thermal imaging studies and shows reasonable agreement, especially at low gas flow rates. As a result, a procedure has been developed to calculate flare tip temperature profiles (via CFD) and mechanical integrity (via FE stress analysis) of flare tips, and thus assess suitability of any flare tip design prior to manufacture and installation.

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26

Nogueira, Antonio Jose Arsenia. "Modelling the physiological performance of Daphnia (Crustacea: Cladocera) under stress." Thesis, University of Stirling, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.320355.

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27

Lim, Yee Mei. "Detecting and modelling stress levels in e-learning environment users." Thesis, De Montfort University, 2017. http://hdl.handle.net/2086/14210.

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A modern Intelligent Tutoring System (ITS) should be sentient of a learner's cognitive and affective states, as a learner’s performance could be affected by motivational and emotional factors. It is important to design a method that supports low-cost, task-independent and unobtrusive sensing of a learner’s cognitive and affective states, to improve a learner's experience in e-learning, as well as to enable personalized learning. Although tremendous related affective computing research were done in this area, there is a lack of empirical research that can automatically measure a learner's stress using objective methods. This research is set to examine how an objective stress measurement model can be developed, to compute a learner’s cognitive and emotional stress automatically using mouse and keystroke dynamics. To ensure the measurement is not affected even if the user switches between tasks, three preliminary research experiments were carried out based on three common tasks during e-learning − search, assessment and typing. A stress measurement model was then built using the datasets collected from the experiments. Three stress classifiers were tested, namely certainty factors, feedforward back-propagation neural network and adaptive neuro-fuzzy inference system. The best classifier was then integrated into the ITS stress inference engine, which is designed to decide necessary adaptation, and to provide analytical information of learners' performances, which include stress levels and learners’ behaviours when answering questions.

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28

Beesley, Ross. "Crack growth modelling from stress concentrations under cyclic loading histories." Thesis, University of Strathclyde, 2017. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=28446.

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Structural integrity is a vitally important field of engineering with fracture and fatigue causing the vast majority of mechanical failures. This is of particular importance within the power industry where the consequences of failure can be severe. Power plant components may contain complex geometries and critical features which can introduce stress concentrations, and are often subject to complex cyclic loading histories. Consequently,fatigue is a dominant failure mechanism which can limit the component life. This research is targeted towards industrial gas turbines, with a specific application to nozzle guide vanes, in which, the extreme temperatures involved induce great thermal loading, compromising their integrity. To this end, extensive development is continually performed to carefully balance their thermal and structural requirements. However,there is still a need to improve understanding of these complex stress distributions. Conventional fatigue life assessment methods can be overly simplistic and tend to offer a one-size-fits-all approach, potentially providing overly conservative values of fatigue life. More realistic methods with improved levels of accuracy are therefore needed. This highlights the requirement for more bespoke techniques that can offer a greater understanding of the stress distributions in these complex components and high specification materials. During the development of such bespoke methods, it is important that they are readily accessible for routine use within engineering, by providing a user-friendly step-by-step approach. This industrial sponsored research aims to address these issues and provide a turn-key solution. Included in this procedure, are two novel methodologies which have been developed during the course of this work. These are the Reversed Plasticity Domain Method for the determination of the critical loads to cause low cycle fatigue failure, and the Modified Monotonic Loading Concept for the calculation of the cyclic J-integral.

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29

Lobosco, Vinicius. "On the Modelling of Mechanical Dewatering in Papermaking." Doctoral thesis, KTH, Fibre and Polymer Technology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3702.

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Most of the water fed into a paper machine is removedmechanically in the forming and press sections. One of thefactor which has an important influence on mechanicaldewatering, i.e. in both forming and pressing, is thestress-strain behaviour of the fibre network.

The focus of this thesis is on the development of improvedmathematical descriptions of the stress-strain behaviourexhibited by fibre networks in the forming and press sections.The first part of the thesis presents a physically based modelof the forming and densification of fibre mats in twin-wireformers. The model can calculate the ecect of the applicationof a varied load through the forming section. It was developedfrom mass and momentum balances of the fibre and liquid phases,the fibre mat stress-porosity relation and an expression forthe permeability as a function of the porosity. The fibre-matstress-porosity relation used is rate-independent and presentshysteresis. Simulations have been conducted to study theeffects of roll pressure, blade pulses, wire tension andbeating. The effect of sequential blade pressure pulses afterthe forming roll on the dewatering and the concentrationgradients could be characterised. The simulations alsoexhibited rewetting by expansion when the fibre mats left theforming roll. Increasing wire tension resulted in increaseddewatering, but the rate of increase diminished rapidly withincreasing tension. The simulation results also indicated thatbeating has a large influence on dewatering.

The second part of the thesis presents two models of therate-dependent stress-strain behaviour of the fibre networkthat is observed in wet pressing. The first model was based onthe approach pioneered by Perzyna (1966) for strain-ratedependent plasticity and was quite satisfactory for calculatingthe stress-strain behaviour of the fibre network in singlepress nips. It was successfully applied for studyingdensification and dewatering in both normal wet pressing andhigh temperature wet pressing. However, the first model onlyincludes rate dependence in the compression phase of thecompressionexpansion cycle; the expansion phase is treated asbeing rate independent

The second model of the stress-strain behaviour of the fibrenetwork treats both compression and expansion as being ratedependent, according to experimental observations. It is basedon the idea that the wet fibre web may be conceived as alayered network of restricted swelling gels. A swollen fibre isa restricted gel, the inner swelling pressure in a swollenfibre wall being balanced by the stresses in the fibre wallstructure. The observed rate dependence of wet webs in bothcompression and expansion phases was attributed to the flow ofwater out of and into the fibre walls. The second model gavepredictions that are in good agreement with results fromuniaxial experiments using pressure pulses of arbitrary shapefor both a single pulse and a sequence of pulses. It maytherefore be used as a general model for the rheologicalbehaviour of the wet fibre network in wet pressing, providedthe model parameters are estimated from experimental data withsmall experimental error.

KEYWORDS:Paper, modelling, dewatering, forming, wetpressing, fibre network stress, rheology, hysteresis,intra-fibre water, compressibility, structural stress,stress-strain, restricted gels, swelling.

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30

Ventura, Antunes Fernando Jorge. "Influence of frequency, stress ratio and stress state on fatigue crack growth in nickel base superalloys at elevated temperature." Thesis, University of Portsmouth, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.285929.

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31

Mok, K. K. K. "The physical and numerical modelling of anisotropic and discontinuous rock masses." Thesis, University of the West of Scotland, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372554.

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32

Howard, Richard John Anderson. "Direct numerical simulation and modelling of turbulent channel flows subjected to complex distortions." Thesis, Queen Mary, University of London, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.313782.

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33

Agwubilo, Ikenna. "Manufacture, modelling and characterisation of novel composite tubes." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/manufacture-modelling-and-characterisation-of-novel-composite-tubes(c11f005b-e651-481f-8ef5-4e6784bfbaa7).html.

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This thesis primarily focused on the development of novel composite tubes by braiding. The objective was to use hierarchical scale technique, i.e., micro, meso and macro scales, with the transfer of information from one scale to another to develop novel braided composite tubes. This research was conducted and reported in three journal papers. The aim of the first paper was to predict plane elastic properties for E-glass/epoxy braided composite structures at different braid orientations, by analytical and finite element techniques. The lenticular shape has been used to describe the geometry of the tow. Modified lenticular geometric model was developed to improve an existing geometric model, in terms of tow parameters, thereafter, plane elastic properties from Chamis micromechanical model for E-glass fibre and epoxy matrix without any knockdown effects were used as benchmark to develop predictive models, namely; Lekhnitskii's methodology and braided unit cell meso-scale finite element model to account for the effects of tow geometry, undulations/crimp, cross-over and braid orientations on the plane elastic properties of E-glass/epoxy composite. The results showed agreement in trend between the predictive models, Chamis micromechanical model, and a similar existing model. However, the plane elastic properties were knocked down in predictive models by 30% in the E11 direction and 32% in the E22 direction, when compared with Chamis micro-mechanical model for largest ±65° braid angle, among the braid angles, considered. The aim of the second paper was to manufacture E-glass/epoxy braided tubes at different braid orientations by vacuum bag infusion technique, conduct internal pressure tests, and determine the hoop and axial moduli of the infused tubes. Lekhnitskii's methodology was also used to develop plane elastic moduli by experiment using microscopy results, and by calculation. The experimental elastic moduli of the infused tubes and the experimental elastic moduli from Lekhnitskii's methodology were used to compare the predictive elastic moduli for E-glass/epoxy braided structures by Chamis micro-mechanical model, and the braided unit cell meso-scale finite element model. The two were from another paper. Results showed a perfect agreement in trend between the experimental results and the predictive results. However, the values of the experimental results were close but lower than the predicted results. Optical microscopy was performed on braided tube cross-section to evaluate the level of crimp or undulation. This was done by the determination of tow centreline crimp angle and aspect ratio. Results show that when compared with the predicted crimp, there was an agreement in trend, although the experimental results were lower than the predicted. Also, the knockdown factor was evaluated and used to quantify the reduction in experimental elastic moduli when compared with the predicted. Results showed that the absences of crimp in the Chamis model caused a tremendous difference between it, other predicted models and the experiment results. The elastic moduli of Chamis were by far higher than all others, including other predictive models. The purpose of the third paper was to manufacture E-glass/epoxy braided tube at ±31°, ±45°, ±55°, ±65° braid orientations using vacuum bagging and resin infusion technique, to design and manufacture a rig for tube internal pressures experiment, to determine the hoop and axial stress performances of the tubes by internal pressure experiment, to compare experimental results with laminate analysis predictions to evaluate the effect of crimp on the internal pressure performance of the braided tubes. To use E-glass braided tow meso-scale unit cell finite element model to predict the tow critical stresses, and the optimum braided tube architecture, using tube hoop and axial failure stresses or strains. The tubes were manufactured and subjected to internal pressure test (2:1), to failure. Failure mode was by weeping and bursting. Hoop stress was twice the axial stress. The highest value of hoop stress was at the ±65° braid angle, higher than the hoop stresses at the ±31°, ±45°, and ±55 ° braid angles by 50%, 39%, and 28% respectively. Hoop stress increased with increase in braid angle. The experimental results were validated by laminate analysis predictions by Chamis micro-mechanical model and Lekhnitskii's methodology, and the trend of the laminate analysis prediction matched that of the experimental results. However, the predicted values were higher than the experimental results by 21%, 14%, 11%, 10% for the ±31°, ±45°, ±55°, ±65° braid angles for the Chamis micro-mechanical model and 5%, 7%, 7%, 5% for the ±31°, ±45°, ±55°, ±65 braid angles respectively for the Lekhnitskii's model, showing the severe effect of crimp in the experimental tube, mostly when compared with Chamis micro-mechanical model. Braided tow unit cell finite element model prediction, showed that tow axial stresses increased with increase in braid angle, while the tow transverse stresses decreased with increase in braid angle. The predictions showed that the tow critical stresses and the tube optimum braided architecture lie between the ±65° and 90° braid angles. The tow critical stresses are the stresses at which the tow decreasing transverse stress and the tow increasing axial stress causes the tube to fail.

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34

Mishra, Sanjay Kumar. "Evaluation of finite element modelling techniques and healing hypotheses for a tibial fracture." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302131.

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35

Fjeldstad, Arne. "Modelling of Fatigue Crack Growth at Notches and Other Stress Raisers." Doctoral thesis, Norwegian University of Science and Technology, Department of Engineering Design and Materials, 2007. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1811.

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This thesis consists of an introduction and eight papers [1–8]. Paper 1 presents simple and flexible methods to enhance the fatigue life of welded aluminium components. The key element of the methods is to change residual stresses from tension to compression at locations vulnerable to fatigue crack growth. This is accomplished by mechanical pre-stressing using elastic pre-deformation or thermal pre-stressing using induction heating. Based on fatigue test results induction heating tuned out to be the most promising method.

In Paper 2, an approximate method based on asymptotic solutions for estimating the stress intensity factor for cracks at stress concentrations is presented. The proposed solution makes use of the near-notch and remote-notch solution to interpolate over the entire range from shallow to deep cracks. Paper 3 extends the theory presented in Paper 2 to cover through-cracked plates of finite width subjected to bending or tension. Paper 4 examines how a decreasing stress field influences the fatigue crack growth. Even though the stress generally decreases from a maximum at some critical point, fatigue crack growth analyses are often performed assuming a homogeneous stress state to avoid the difficulties related to crack growth analyses in complex components. The degree of conservatism has been determined by comparing the calculated fatigue life of cracks growing in a homogeneous stress field with the fatigue life of cracks growing in a gradient stress field. In Paper 5, an approximate method based on asymptotic solutions for estimating the stress intensity factor for cracked V-notched plates is presented. The proposed solutions make use of a reference solution to interpolate from shallow to deep cracks. The reference solution is obtained by considering the current crack emanating from the associated specimen with a sharp notch. It is showed how the proposed theory can be used for estimating the stress intensity factor for a crack located at the root of a weld toe in a T-joint.

Paper 6 and 7 presents the probabilistic fatigue assessment tool, P•FAT, for the fatigue analysis of arbitrary components. General concepts which have to be considered for the accomplishment of a 3D fatigue crack simulation by postprocessing results from a standard finite element analysis are introduced. General features such as determination of the life controlling defect, fatigue strength and fatigue life distribution, and probability of component failure, have been presented. Furthermore, a new short crack growth model that accounts for short crack growth is presented. In Paper 8, the short crack growth model is used to predict the arrest of cracks growing in stress gradient fields. The predictions have been compared with experimentally obtained data for notched specimens and found to agree well.

Paper I and II reprinted with kind permission of Elsevier, sciencedirect.com

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36

Olden, Vigdis. "FE modelling of hydrogeninduced stress crackingin 25% Cr duplex stainless steel." Doctoral thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for produktutvikling og materialer, 2008. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-5026.

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37

Gonzalez, David. "A contribution on modelling deformation and residual stress in 3D polycrystals." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/a-contribution-on-modelling-deformation-and-residual-stress-in-3d-polycrystals(dad0c6be-0494-46e6-8dc8-d3a968212401).html.

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Polycrystalline materials are widely used for industrial applications. These materials are highly anisotropic with different responses under different loading conditions. This dissertation uses a crystal plasticity scheme in the finite element framework (CPFEM) to study deformation mechanisms in alumina, aluminium and stainless steel – all polycrystalline. Four research cases in this dissertation have been presented in the form of manuscripts for publication. When possible, modelling predictions have been compared against various experimental techniques such as Diffraction Contrast Tomography (DCT), Neutron Diffraction (ND) and Electron Back Scatter Diffraction (EBSD). After an introduction (Chapter 1) and a literature review (Chapter 2) on plastic deformation and modelling techniques, the methodology and results are presented and discussed (Chapters 3 and 4). Measurements of elastic strains for individual grain families (ND) and local rotations (DCT and EBSD) are compared against corresponding predictions by the model following different loading modes. Each study reveals different degrees of agreement between predictions and measurements. The individual conclusions to each study are presented in Chapter 4. Some overall conclusions and suggestions for further work are presented in Chapter 5.

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38

Ollander, Simon. "Wearable Sensor Data Fusion for Human Stress Estimation." Thesis, Linköpings universitet, Reglerteknik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-122348.

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With the purpose of classifying and modelling stress, different sensors, signal features, machine learning methods, and stress experiments have been compared. Two databases have been studied: the MIT driver stress database and a new experimental database, where three stress tasks have been performed for 9 subjects: the Trier Social Stress Test, the Socially Evaluated Cold Pressor Test and the d2 test, of which the latter is not classically used for generating stress. Support vector machine, naive Bayes, k-nearest neighbor and probabilistic neural network classification techniques were compared, with support vector machines achieving the highest performance in general (99.5 ±0.6 %$on the driver database and 91.4 ± 2.4 % on the experimental database). For both databases, relevant features include the mean of the heart rate and the mean of the galvanic skin response, together with the mean of the absolute derivative of the galvanic skin response signal. A new feature is also introduced with great performance in stress classification for the driver database. Continuous models for estimating stress levels have also been developed, based upon the perceived stress levels given by the subjects during the experiments, where support vector regression is more accurate than linear and variational Bayesian regression.
I syfte att klassificera och modellera stress har olika sensorer, signalegenskaper, maskininlärningsmetoder och stressexperiment jämförts. Två databaser har studerats: MIT:s förarstressdatabas och en ny databas baserad på egna experiment, där stressuppgifter har genomförts av nio försökspersoner: Trier Social Stress Test, Socially Evaluated Cold Pressor Test och d2-testet, av vilka det sistnämnda inte normalt används för att generera stress. Support vector machine-, naive Bayes-, k-nearest neighbour- och probabilistic neural network-algoritmer har jämförts, av vilka support vector machine har uppnått den högsta prestandan i allmänhet (99.5 ± 0.6 % på förardatabasen, 91.4 ± 2.4 % på experimenten). För båda databaserna har signalegenskaper såsom medelvärdet av hjärtrytmen och hudens ledningsförmåga, tillsammans med medelvärdet av beloppet av hudens ledningsförmågas derivata identifierats som relevanta. En ny signalegenskap har också introducerats, med hög prestanda i stressklassificering på förarstressdatabasen. En kontinuerlig modell har också utvecklats, baserad på den upplevda stressnivån angiven av försökspersonerna under experimenten, där support vector regression har uppnått bättre resultat än linjär regression och variational Bayesian regression.

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39

Moisio, K. (Kari). "Numerical lithospheric modelling: rheology, stress and deformation in the central Fennoscandian Shield." Doctoral thesis, University of Oulu, 2005. http://urn.fi/urn:isbn:9514279514.

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Abstract This thesis deals with the analysis of the rheological structure and tectonic modelling of the Fennoscandian Shield. First, a short introduction to the geology and geophysics of the Fennoscandian Shield is presented followed by a description of rheological concepts. Second, the applied modelling procedures, together with the sources of error are explained. Last a brief summary of each original paper including conclusions is given. Understanding rheological conditions through the entire lithosphere and even deeper is the key for understanding the deformation of the earth's interior. Thus, investigating the rheological structure and possible consequences resulting from tectonic loading are required to some extent when interpreting geophysical data into tectonic models. In this thesis rheological structure is obtained by calculating rheological strength in different locations of the central Fennoscandian Shield. These locations are mainly situated along different deep seismic sounding (DSS) profiles as they provide necessary geophysical information required for model construction. Modelling begins by solving the thermal structure in the lithosphere, as rheological behaviour, mainly ductile flow is strongly controlled by temperature. Results from these calculations show that the rheological structure of the lithosphere depends on the thermal conditions resulting in significant areal variations. Generally, the central Fennoscandian Shield can be considered to be rheologically rather strong. Rheologically weak layers are however usually found in the lower crust. Correlation of the rheological structure with earthquake focal depth data shows that brittle fracture is the relevant mechanism in the earthquake generation and that non-occurrence of deep earthquakes implies low stress or high strength conditions deeper in the crust. Calculated rheological structure is furthermore used as a material parameter in the structural models which are solved next. These results suggest that it is highly unlikely that any considerable ductile deformation in the crust of the central Fennoscandian Shield exists and it seems that the present-day thermal and mechanical conditions in the investigated area do not favour such processes in significant amounts.

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40

Spira, Daniel. "Near-wall Reynolds stress modelling in rotating channel flows using elliptic relaxation." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0004/MQ44042.pdf.

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41

Spira, Daniel. "Near-wall Reynolds stress modelling in rotating channel flows using elliptic relaxation." Thesis, McGill University, 1997. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=20521.

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Over the past twenty-five years, there has been considerable research devoted to the development of Reynolds stress turbulence models. One particular research area is the development of representations for the pressure-strain correlation which reliably account for the effects of solid walls with complex geometries. This thesis is a theoretical and numerical study of a fairly recent method: elliptic relaxation.
There are two challenges in using this method: (1) the determination of appropriate boundary conditions for the elliptic relaxation equations, and (2) the numerical implementation of those boundary conditions in non-Cartesian geometries. In this thesis, a set of 2D boundary conditions are derived via an asymptotic analysis of the Reynolds stress transport equations through the viscous sublayer. 1D and 2D finite volume numerical models to solve two elliptic relaxation models, the k-epsilon- vv model and a Reynolds stress version, are developed. These formulations are then used to compute the steady flow through stationary and rotating plane channels, and through a plane diffuser. The results are compared with benchmark direct numerical simulation and experimental data.

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42

Cacace, Mauro [Verfasser]. "Stress and Strain modelling of the Central European Basin System / Mauro Cacace." Berlin : Freie Universität Berlin, 2008. http://d-nb.info/1023169886/34.

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43

Drews, Michael C. "Modelling stress-dependent effective porosity-permeability relationships of metre-scale heterogeneous mudstones." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1672.

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The importance of shales and mudstones to applied geosciences and in particular to fluid migration in sedimentary basins has never been more recognized than today. Prominent examples are conventional or unconventional petroleum systems, where shales and mudstones act as source, reservoir or cap rock, but also CO2 and nuclear waste storage or hydrogeology. Despite their importance, shales and mudstones are yet not as far well understood as sandstones or carbonate rocks. In particular, the influence of heterogeneity on fluid migration has been poorly addressed in the past, although many authors have identified and studied heterogeneities in shales and mudstones. Nevertheless, their flow properties are fairly well understood when treated as homogeneous on sample scale (centimetre-scale). Typical flow relevant heterogeneities are grain size and thus petrophysical property (e.g. porosity, permeability, capillary entry pressures) variations due to spatial lithological variation induced by primary and secondary sedimentary structures. In this study we investigate flow relevant heterogeneities of shales and mudstones on submetre scale derived from core and borehole images from an off-shore gas field in the Western Nile Delta, Egypt. Thereby, we combine latest models and published measurements of sample-scale petrophysical properties with interpretation, quantitative analyses, advanced modelling and numerical fluid flow simulation to assess the influence of shale and mudstone heterogeneity on fluid flow and hence, fluid migration, retention and mudstone seal capacity. Additionally, the set of mudstone heterogeneities used in this study has been derived from a combined visual and geostatistical interpretation of more than 500 m of mud-rich core and borehole images. As final results, we deliver stress-dependent effective porosity-permeability relationships for a broad range of shale and mudstone heterogeneities, representative model sizes and resolution as well as measures of uncertainty for each heterogeneity type. Moreover, probability density functions describing where and how these heterogeneities appear in larger scale geological units, such as seismic facies or local depositional environments, are provided. As a key result, heterogeneity and lithological variation have great influences on effective permeability and effective permeability anisotropy (Kh/Kv). Furthermore, our results indicate that mudstone heterogeneity is very common in all investigated larger scale geological units (hemipelagites, levees, channels). Modelling of fluid flow through mud-rich sedimentary basins without inclusion of these sub-metre scale heterogeneities of mudstones can therefore lead to misleading results. Thus, effective porosity-permeability (anisotropy) relationships are provided for different lithological variations and mudstone heterogeneities as a final result.

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44

Parikh, Tejas. "Determination and modelling of residual stress and strain in Nb3Sn superconducting wires." Thesis, Oxford Brookes University, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.506092.

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45

Ward, David John. "Finite element modelling of stress development during deposition of ion assisted coatings." Thesis, University of Salford, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.366326.

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46

Parsa, Arash. "Finite element modelling of stress concentrations in a reinforced concrete offshore structure." Thesis, University of Southampton, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292406.

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47

Scanlon, Thomas Joseph. "Work and non-work stress among solicitors : modelling the work-home interface." Thesis, University of Central Lancashire, 2005. http://clok.uclan.ac.uk/22005/.

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Focusing upon solicitors working in private law firms in England and Wales, the study investigates the interrelationships between domain-specific and work-home interference factors and their predictive value in relation to different categories of strain symptomatology and satisfaction outcomes. The research also examines the moderating influences of gender and family type on the interface between work and home, and their differential impacts on well-being. Data were gathered in two stages. Stage one involved 20 interviews that allowed respondents to identify sources of work and home pressures for themselves. Content analysis of the interview transcripts facilitated the development of separate work and home pressure inventories. In addressing the difficulties associated with construct measurement, stage two developed an unorthodox approach for measuring both forms of work-home interference, which was part of an extensive survey instrument that included established outcome measures. The sample group was devised using a cluster sampling strategy whereby legal firms were grouped according to their size and then by regional cities. Nearly 2,500 surveys were distributed with a return rate of nearly 30%. The data set was split into two sub-sets via a cluster sampling strategy based on gender and family type to allow for a series of exploratory and confirmatory analyses in the development and testing of structural equation models of the work and home domain. A distinguishing feature of this study is its examination of the work-home interface at the microlevel, which involved developing a series of structural equation models relevant to the most salient sources of work-home interference and domain-specific pressures experienced by solicitors. Through a series of exploratory and confirmatory analyses, the study' tested three differing sets of explanatory relations as to the interplay between specific aspects of the two domains, and the implications of this interplay for a range of outcomes. The findings provide strong empirical support to assert that work-to-home interference (e. g., concerns over ability) and home-to-work interference (e. g., unfulfilled domestic responsibilities) represent two distinct dimensions of individuals functioning with different rates of prevalence and different role related antecedents and outcomes that indicate that solicitors are being stretched in both domains. The empirical evidence indicates an increasing convergence in the public and private roles of male and female solicitors, highlighting the importance of both sexes having the opportunity to attain a balance between the domains of work and home. The study also demonstrates that work-home interference is not exclusively a problem for employees located in traditional nuclear families and shows that solicitors within differing familial situations (e. g., single persons) experience high levels of work-home interference that can exacerbate domainspecific pressures resulting in a poor state of health and low levels of work and home satisfaction.

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48

Banks, James R. "Numerical modelling of lateral stress on integral abutments due to cyclic loading." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/210943/.

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The integral bridge concept eliminates problems associated with expansion joints and bearings used on conventional bridges. However, integral structures are not free from problems, and of particular concern is the magnitude of lateral soil stress which acts on the abutments. The cyclic nature of abutment displacement, caused by thermal loading of the deck, results in increased lateral soil stress from the granular backfill. Previous experiments investigated the fundamental behaviour of a granular soil element under integral bridge loading. No existing constitutive soil model replicated this behaviour, and therefore a soil model has been developed based upon this data. It was designed to account for the changes in secant stiffness and vertical strain due to the density and rolling/sliding behaviour of soil particles at the active state, found to be important in the previous research. The model was implemented into a finite difference method program, and initially validated by modelling the experimental triaxial tests. Subsequent modelling of centrifuge tests of bridge abutments, carried out by independent researchers, allowed the soil model to be validated at system level. After validation and testing, the model was considered suitable for predicting the lateral stress profile acting on integral bridge abutments and used in a parametric study. This highlighted that the value of wall friction coefficient is particularly significant in the system behaviour. The centrifuge test is an idealised system where only rotation/flexure is possible, so a spread base abutment was modelled to investigate the predicted stress profile for an in-service bridge. These were shown to be significantly different to those prescribed by BA42/96, both in shape and magnitude. Additionally, modelling daily cycles results in a different profile to yearly cycles. This research has shown that the soil model developed can provide good estimates of lateral soil stress. This can be used to further investigate soil loads acting on integral bridge abutments with the aim of improving the design of such structures.

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49

Su, Yang. "Modelling study of stress displacement theories for retaining walls under seismic excitation." Thesis, Curtin University, 2014. http://hdl.handle.net/20.500.11937/2253.

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A strutted retaining wall system under seismic excitation was modeled by PLAXIS and ABAQUS. The results were evaluated based on analytical theories based on stress displacement behavior. The results showed good general agreement between modeling and theoretical results. A method is produced to utilize numerical output to gain relevant theoretical parameters. The variance in local wall response was critically studied and a new direction was proposed for seismic stress displacement behavior of retaining walls.

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50

Mineault-Guitard, Alexandre. "Validation of Observed Bedload Transport Pathways Using Morphodynamic Modelling." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34587.

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Braiding is a mesmerizing phenomenon since flow and sediment transport interact and are able to change the morphology of a channel in a rapid and complex fashion. Conventional two-dimensional morphodynamic models estimate bedload distribution using shear stress distribution. However, it is unclear if the use of such shear stress distributions is relevant or applicable for all situations when using two-dimensional morphodynamic modelling. This thesis strives to investigate whether shear stress distributions are useful to predict bedload transport pathways. This study focuses upon prediction of bedload transport pathways using a morphodynamic model (Delft3D) of an anabranch of the Rees River (New Zealand). Observed bedload transport pathways were compared to modelled bedload transport pathways in an attempt to validate the predictive ability of the model. Results show that there is a significant correlation between predicted bedload transport pathways and the apparent bedload transport pathways derived from the field measurements. Furthermore, bedload transport predictions were in good agreement with observed data in areas where the model’s predictions of high shear stress were comparable to field observations. However, substantial bedload transport predictions in low shear stress areas were not adequately captured by the model, suggesting that the observed pathways were not due to high shear stress, but rather to other sediment supply sources.

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