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1
Stamatopoulos, Ioannis D. "Analytical techniques for modelling the laminated waveguide." Thesis, University of Surrey, 2003. http://epubs.surrey.ac.uk/844108/.
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This thesis is focused on a study on the dispersion formulation of the recently appeared ''laminated waveguide". In this framework a new method for the analysis of a wide variety of microwave components like posts, circular junctions or corners in rectangular waveguides is developed. This method can be used to model the posts in the laminated waveguide geometry and this was the main motivation of the present work. The method gives the impedance or admittance matrix of the microwave component by applying discrimination between the localised and accessible modes on the indirect mode matching (IMM) formulation. In all cases the method proved to be fast, very accurate and easy to implement. The application of the IMM technique to the dispersion formulation of the laminated waveguide is undertaken by implementing the Transverse Resonance Method. It is the first time that effort is paid, so that every possible polarisation of both bounded and unbounded modes is considered. In the process a new analytic solution is given for the modelling of the transverse bifurcation. Its significance relies on the the fact that the method of moments is not to be used in the analysis and thus its overall speed is increased. The total procedure is expected to be straightforward and flexible.
2
Robin, Victor Paul Michel. "Analytical and numerical modelling of artificially structured soils." Thesis, University of Exeter, 2014. http://hdl.handle.net/10871/16565.
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The effects of lime treatment on the mechanical properties of soils are usually not accounted for in the design of geotechnical structures. As a result the potential of lime treatment has not been fully exploited. In this thesis, a comprehensive experimental program has been carried out to identity the key features of the mechanical behaviour of structured materials. The chemical modifications arising from lime treatment were quantified using thermal analysis methods. From these results a non-linear chemo-mechanical coupling was established between the concentration of cementitious compounds and the yield stress. Using these results, a new formulation to model the degradation of the structure at yield has been developed and implemented in a constitutive model for structured materials. This new model, developed in the framework of the Modified Cam Clay model, requires a limited number of additional parameters that all have a physical meaning and can all be determined from a single isotropic compression test. The model has proven to be successful in reproducing the key features of structured materials and for the modelling of the mechanical behaviour of lime treated specimens under various stress paths. Due to similarities in behaviour, it is shown that the formulation is also suitable for naturally structured soils. To account for a structured material in the design of geotechnical structures, a fully functional finite element program for elasto-plastic problems was developed including the pre- and post-processing of the results. A thorough validation has confirmed the good implementation of the finite element method and its suitability for the modelling of complex geometries involving structured materials.
3
Weaver, Andrew John. "Numerical and analytical modelling of oceanic/atmospheric processes." Thesis, University of British Columbia, 1987. http://hdl.handle.net/2429/27560.
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Two problems in oceanic/atmospheric modelling are examined in this thesis. In the first problem the release of fresh water from a midlatitude estuary to the continental shelf is modelled numerically as a Rossby adjustment problem using a primitive equation model. As the initial salinity front is relaxed, a first baroclinic mode Kelvin wave propagates into the estuary, while along the continental shelf, the disturbance travels in the direction of coastally trapped waves but with a relatively slow propagation speed. When a submarine canyon extends offshore from the estuary, the joint effect of baroclinicity and bottom relief provides forcing for barotropic flow. The disturbance now propagates along the shelf at the first coastally trapped wave mode phase speed, and the shelf circulation is significantly more energetic and barotropic than in the case without the canyon. For both the experiments with and without a canyon an anticyclonic circulation is formed off the mouth of the estuary, generated by the surface outflow and deeper inflow over changing bottom topography. As the deeper inflow encounters shallower depth, the column of fluid is vertically compressed, thereby spinning up anticyclonically due to the conservation of potential vorticity. This feature is in qualitative agreement with the Tully eddy observed off Juan de Fuca Strait. A study of the reverse estuary (where the estuarine water is denser than the oceanic water) shows that this configuration has more potential energy available for conversion to kinetic energy than the normal estuary. Bass Strait may be considered as a possible reverse estuary source for the generation of coastally trapped waves. Model solutions are compared with field observations in the Bass Strait region and with the results of the Australian Coastal Experiment. The effects of a wider shelf and a wider estuary are examined by two more experiments. For the wider shelf, the resulting baroclinic flow is similar to that of the other runs, although the barotropic flow is weaker. The wide estuary model proves to be the most dynamic of all, with the intensified anticyclonic circulation now extending well into the estuary.
In the second problem the effect of the horizontal structure of midlatitude oceanic heating on the stationary atmospheric response is examined by means of a continuously stratified model and a simple two level model, both in the quasigeostrophic β-plane approximation.
Solutions are obtained for three non-periodic zonal heating structures (line source, segmented cosine, and segmented sine). Little difference is observed between the solutions for these two different models (continuously stratified and two level). There are two cases which emerge in obtaining analytic solutions. In case 1, for large meridional wavenumbers, there exists a large local response and a constant downstream response. In case 2, for small meridional wavenumbers, the far field response is now sinusoidal. A critical wavenumber separating these two cases is obtained. The effect of oceanic heating on the atmosphere over the Kuroshio region is examined in an attempt to explain the large correlations observed between winter Kuroshio oceanic heat flux anomalies, and the winter atmospheric surface pressure and 500 & 700 mb geopotential heights, both upstream and downstream of the heating region. In both models, the response is consistent with the observed
correlations. When western North Pacific heating and eastern North Pacific cooling are introduced into the models, a large low pressure response is observed over the central North Pacific. This feature is in excellent agreement with the observed correlations. A time dependent, periodic, two level model (with and without surface friction) is also introduced
in order to study the transient atmospheric response to oceanic heating. The height at which the thermodynamic equation is applied is found to be crucial in determining the response of this model. When the heating is entered into the model near to the surface, unstable modes are prevalent sooner than they would be when the heat forcing is applied at a higher level. As in the steady state models, two cases dependent on the meridional wavenumber ɭ emerge in the analysis. For small scale meridional heating structures (large ɭ), the response consists of an upper level high and a lower level low which propagate eastward with time. For large scale meridional heating structures (small ɭ) the response essentially consists of a wavenumber 3-4 perturbation superimposed on the solution for large ɭ.Science, Faculty of
Mathematics, Department of
Graduate
4
Bullock, Richard Simon. "Modelling analytical and physical variation in animal feeds." Thesis, University of Exeter, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.324065.
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Vitucci, Gennaro. "Analytical and numerical modelling of thin functional layers." Thesis, Aberystwyth University, 2018. http://hdl.handle.net/2160/21af2cbb-6c9e-4b1a-8521-0113628e854e.
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The thesis deals with the study of thin layers and their function within larger structures. Different thin intephases appearing in mechanics and biomechanics are considered. The work aims at setting a manageable mathematical framework in mechanical modelling. Analytical methods are provided in order to achieve closed-form solutions and effective numerical procedures. Cartilage, which reveals crucial in transmitting loads without friction along the skeleton, is thoroughly investigated. Governing equations derived within mixture theory are used for a biphasic description of the tissue. Inhomogeneity and anisotropy are introduced and their effect on the global behavior of the tissue is investigated. This is accomplished via integral transforms for relatively small thickness of the layer and short-time asymptotics. The model is extended to study the three-dimensional contact of cartilage surfaces in the joint. The involved integro-differential equations are solved in closed-form. Next, intra-articular pressurization is taken into account via modelling the whole joint capsule. Implications for healthy degenerated and tissues are discussed. Lastly, cylindrical multilayer assemblies of layers are examined in the framework of thermoelasticity. The general solutions for the single components are arranged in a way to conveniently constitute a linear system. Perfect and imperfect contact between the layers are considered. An efficient numerical scheme is developed. Simulations are run with a special eye on ceramics.
6
Birchenko, Vasily Mihailovich. "Analytical modelling of wells with inflow control devices." Thesis, Heriot-Watt University, 2010. http://hdl.handle.net/10399/2349.
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Inflow Control Devices (ICD) have been successfully used in hundreds of wells around the world during the last decade and are now considered to be a mature well completion technology. This work is dedicated to the methodology of making following three decisions with respect to ICD application: 1. Selection between ICD and Interval Control Valves (ICV), the other advanced completion technology. 2. Identification of whether particular well is likely to benefit from ICD. 3. Quantification of the anticipated positive effect. Design of an advanced completion for a particular field application often includes feasibility studies on both ICV and ICD. The choice between these two technologies is not always obvious and the need for general methodology on making this choice is recognised by the petroleum industry. In this dissertation ICD has been compared against the competing ICV technology with particular emphasis on issues such as uncertainty in the reservoir description, inflow performance and formation permeability. The methodology of selection between ICD and ICV is proposed. The benefits of ICD application can, by and large, be attributed to reduction of the following two effects detrimental to horizontal well performance: Inflow profile skewing by frictional pressure loss along the completion (heel-toe effect). Inflow variation caused by reservoir heterogeneity. Frictional pressure drop along the completion is an important design factor for horizontal wells. It has to be taken into account in order to secure optimum reservoir drainage and avoid overestimation of well productivity. Many authors have previously addressed various aspects of this problem, but an explicit analytical solution for turbulent flow in wellbore has not so far been published. This dissertation presents such a solution based on the same assumptions as those of previous researchers. New method to quantify the reduction of inflow imbalance caused by the frictional pressure loss along a horizontal completion is proposed. The equation describing this phenomenon in homogeneous reservoir is derived and two solutions presented: an analytical approximation and a more precise numerical solution. Mathematical model for effective reduction of the inflow imbalance caused by the reservoir heterogeneity is also presented. The trade-off between well productivity and inflow equalisation is a key engineering issue when applying ICD technology. Presented solutions quantitatively addresses this issue. Their practical utility is illustrated through case studies.
7
Kostovasilis, Dimitrios. "Analytical modelling of the vibration of railway track." Thesis, University of Southampton, 2017. https://eprints.soton.ac.uk/413811/.
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The high frequency dynamic behaviour of railway track, in both vertical and lateral directions, strongly affects the generation of rolling noise as well as other phenomena such as rail corrugation. One aspect that has received little attention is the coupling between the vertical and lateral directions. This thesis sets out to build an analytical model of a railway track with three principal targets: to improve the modelling for lateral vibration compared with existing models, to identify the most important sources of coupling between the vertical and lateral directions and to quantify the implications for rolling noise phenomena. Simple models for the axial, torsional, vertical and lateral vibrations of beams are first introduced. The results from these models are analysed based on their dispersion curves and their characteristic behaviour is identified. Furthermore, effects of cross-section asymmetry, shear deformation, rotational inertia, restrained warping and curvature are considered, as well as the fact that the loads at the rail head do not always act through the centroid of the rail section. These beam models are then brought together to formulate a fully coupled beam model. An elastic foundation is then introduced to the beam model to represent the railpads and the dispersion characteristics of the whole track are discussed. Subsequently, the effect of the foundation location is investigated, as well as the inclusion of additional layers of masses and springs, representing the sleepers and ballast. Two different sleeper models are introduced. The first is that of a simple mass allowed to translate and rotate, representing a single block of a bibloc sleeper. The second is that of a flexible finite length beam accounting for vertical, lateral, axial and torsional vibration, representing a monobloc sleeper, which is more widely used in railway tracks. The response of the beam model is compared against measurements performed on sleepers in the laboratory. An average error of less that 1% is observed for the natural frequency of all modes, excluding the first mode. This mode is most influenced by the sleeper cross-section variation which is not directly accounted for in the model.
8
Klyukin, Yury Igorevich. "Modelling and analytical studies of magmatic-hydrothermal processes." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/84442.
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Hydrothermal processes play a major role in transporting mass and energy in Earth’s crust. These processes rely on hydrothermal fluid, which is dissolving, transporting and precipitating minerals and distribute heat. The composition of the hydrothermal fluid is specific for various geological settings, but in most cases it can be approximated by H₂O-NaCl-CO₂ fluid composition. The flow of hydrothermal fluid is controlled by differences in temperature, pressure and/or density of the fluid and hydraulic conductivity of the rock. In my work, I was focused on modeling of the hydrothermal fluid properties and experimental characterization of fluid that formed emerald deposit in North Carolina, USA. The dissertation based on the result of three separate projects.
The first project has been dedicated to characterization of the H₂O-NaCl hydrothermal fluid ability to transport mass and energy. This ability of the fluid is defined by a change in fluid density and enthalpy in response to changing pressure or temperature. In this project we quantified the derivatives of mass, enthalpy and SiO₂ solubility in wide range of pressure, temperature and composition (PTx) of H₂O-NaCl fluid. Our study indicated that the PT region in which fluid is most efficiently can transport mass and energy, located in the critical region near liquid-vapor phase boundary and the sensitivity to changing pressure-temperature conditions decrease with increasing salinity.
In second project we developed the revised H₂O-NaCl viscosity model. Revised model to calculate the viscosity of H₂O-NaCl reproduces experimental data with ±10% precision in PTx range where experimental data available and follows expected trends outside of the range. This model is valid over the temperature range from the H₂O solidus (~0 °C) to ~1,000 °C, from ~0.1 MPa to ≤500 MPa, and for salinities from 0-100 wt.% NaCl.
The third project has been focused on the characterization of formation conditions of the emerald at North American Emerald Mine, Hiddenite, North Carolina, USA. The emerald formation conditions defined as 120-220 MPa, 450-625 °C using stable isotope, Raman spectrometry, and fluid inclusion analysis. Hydrothermal fluid had a composition of CO2-H2O±CH4, which indicates mildly reducing environment of emerald growth.Ph. D.
9
Robin, Victor. "Analytical and numerical modelling of artificially structured soils." Thesis, Université de Lorraine, 2014. http://www.theses.fr/2014LORR0264/document.
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Le traitement des sols à la chaux est une méthode couramment utilisée pour améliorer les propriétés mécaniques de sols aux performances insuffisantes. Cependant, ces améliorations mécaniques ne sont pas prises en compte dans les calculs de dimensionnement. Cette thèse propose une méthodologie pour pallier à ce problème. Un programme expérimental approfondi est réalisé afin de décrire avec précision le comportement mécanique d’un sol traité et les processus associés à la structuration introduite par le traitement. La composition chimique, et notamment la quantité de composés cimentaires hydratés, est déterminée par analyses thermogravimétriques et thermodifférentielles. Un couplage non-linéaire entre la quantité d’hydrates et la limite élastique se basant sur ces résultats expérimentaux est proposé. À partir de ces résultats, une nouvelle formulation a été développée afin de modéliser la dégradation de la structure en plasticité, et a servi au développement d’une nouvelle loi de comportement élasto-plastique basée sur le modèle de Cam Clay Modifié. Cette dernière a montré reproduire correctement les principaux traits de comportement spécifiques aux sols traités. Il est démontré que ce modèle est également adapté aux sols naturellement structurés. Afin de prendre en compte les effets du traitement et la présence de structure dans le dimensionnement, un programme basé sur la méthode des éléments finis, comprenant le pré- et le post-processing de la géométrie et des résultats du problème, a été développé. Une validation rigoureuse a confirmé l'implémentation correcte de la méthode et son potentiel pour l’optimisation du dimensionnement des ouvragesThe effects of lime treatment on the mechanical properties of soils are usually not accounted for in the design of geotechnical structures. As a result the potential of lime treatment has not been fully exploited. In this thesis, a comprehensive experimental program has been carried out to identity the key features of the mechanical behaviour of structured materials. The chemical modifications arising from lime treatment were quantified using thermal analysis methods. From these results a non-linear chemo-mechanical coupling was established between the concentration of cementitious compounds and the yield stress. Using these results, a new formulation to model the degradation of the structure at yield has been developed and implemented in a constitutive model for structured materials. This new model, developed in the framework of the Modified Cam Clay model, requires a limited number of additional parameters that all have a physical meaning and can all be determined from a single isotropic compression test. The model has proven to be successful in reproducing the key features of structured materials and for the modelling of the mechanical behaviour of lime treated specimens under various stress paths. Due to similarities in behaviour, it is shown that the formulation is also suitable for naturally structured soils. To account for a structured material in the design of geotechnical structures, a fully functional finite element program for elasto-plastic problems was developed including the pre- and post-processing of the results. A thorough validation has confirmed the good implementation of the finite element method and its suitability for the modelling of complex geometries involving structured materials
10
Thosar, A. "PEM fuel cells: analytical modelling and experimental validation." Thesis(Ph.D.), CSIR-National Chemical Laboratory, Pune, 2019. http://dspace.ncl.res.in:8080/xmlui/handle/20.500.12252/5188.
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Sternberger, Ronny. "Analytical modelling and controller design of a multilevel STATCOM." Thesis, Available from the University of Aberdeen Library and Historic Collections Digital Resources, 2009. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?application=DIGITOOL-3&owner=resourcediscovery&custom_att_2=simple_viewer&pid=25797.
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Inniss, Clifton F. "Analytical and experimental modelling of timber-concrete composite beams." Thesis, University of Surrey, 1994. http://epubs.surrey.ac.uk/842780/.
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This thesis investigates the behaviour of timber-concrete composite beams with mechanical shear connectors. The analysis of these structures is complex due to the discontinuity caused by slip at the interface between the timber and concrete and can only be achieved by the use of sophisticated analytical techniques. A literature review has been carried out highlighting the fact that only a limited amount of theoretical and experimental work exists on timber- concrete composite beams. The fundamental objectives of this study were to develop suitable analytical and experimental models so as to better understand the behaviour of these structures. Fifty seven push-out specimens and seven beams were tested in order to determine the load/slip characteristics of the coach screw connectors and how these influence the behaviour of the beams. It was found that the bond and friction at the timber-concrete interface had a significant effect on the behaviour of the joints and beams. Analyses were carried out using a fully non-linear finite element package, LUSAS. The finite element model developed consisted of standard two dimensional elements and the results from the beam tests were used in a validation exercise. In general, good agreement was obtained for the stiffness of the beams throughout their loading history. Studies were carried out using the analytical model to determine the influence of the main parameters on the stiffness of the beams. The connector stiffness and timber properties were found to have a strong influence while the concrete properties were not significant at working load level. Further analytical studies were carried out for a wide range of geometric properties. The information obtained was used in the formulation of a design procedure which allowed for slip at the interface of the beams. Recommendations are included for future research on timber-concrete composite beams.
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Milovanovic, Ana. "Semi-analytical modelling of time-variable blazar jet spectra." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496136.
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Selsil, Alana. "Analytical and numerical modelling of a compact catalytic reformer." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.415761.
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Corney, Ransome Kyle Tyrone. "Numerical, analytical & experimental modelling of channelised gravity currents." Thesis, University of Leeds, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.426853.
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Aghababaie, Arian Aziz. "Experimental characterisaion analytical modelling of rocket nozzle side-loads." Thesis, University of Bristol, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.682561.
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During sea-level transients, such as engine start-up or shut-down, ramping chamber pressure causes the nozzle exit pressure to fall below ambient conditions, resulting in flow over-expansion. Internal shockwaves form that incite unsteady boundary layer separation producing an asymmetric internal pressure field that manifests as dynamic off-axis loads. These side-loads reduce the safe-life of the vehicle and have also be known to cause sudden catastrophic failure. As a result, rocket nozzle area ratio is purposely limited to ensure that flow separation does not occur elsewhere in the mission profile and as such, the vacuum performance of the vehicle is reduced by as much as 20%. An experimental study comparing the side-load distributions of four conical nozzles with wall angles, 8.3°, 10.4°, 12.6° and 14.8° a truncated ideal contour and thrust optimised parabolic nozzle has been carried out. Direct side-load measurements taken using a strain tube have shown that conical nozzle wall angle has very little affect on the side-load magnitude. The truncated ideal contour nozzle displayed the lowest side-load distribution and was found to be approximately 50% lower than the magnitudes produced by the thrust optimised parabolic. An analytical model has been developed to simulate the side-load distribution across geometries which only produce free-shock separation. A universal method of replicating the pressure distribution across a free-shock separated nozzle was first developed, validated with a high level of confidence against three nozzle geometries. This was used in conjunction with a shock excursion model, whereby the oblique shock relation was perturbed to first order in order to generate internal pressure field asymmetry. Comparisons made to experimental results have shown the side-load model can predict distributions with errors as low as 3.58% for truncated ideal contour nozzles.
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Ramli, Nabilah Binti. "Analytical modelling of sound transmission in a lined duct." Thesis, University of Southampton, 2013. https://eprints.soton.ac.uk/361186/.
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The focus of this thesis is on the prediction of sound attenuation through a lined duct, based on a mathematical model. Ducts with a single section as well as multi-segmented sections are discussed. The duct of interest has a rectangular cross-section as normally used for ventilation purposes. The mean flow in a ventilation duct is very low and can be neglected. In this thesis, two-dimensional analytical models are developed for sound transmission in a series of different duct configurations. Two models of the lining behaviour are considered, either locally-reacting or bulk-reacting. The models are used first to obtain the transverse and axial wavenumbers of various modes of the duct. The required finite numbers of wavenumbers are tracked using Müller’s method. The wavenumbers are traced from a very low frequency to high frequency using small frequency steps. It is found that, for a duct with a bulk-reacting lining, the number of modes with a transverse wavenumber below a particular value may exceed the corresponding number of modes in a duct with a locally-reacting lining. These additional modes are termed lining modes. The number of lining modes depends on the lining thickness. Dispersion curves are presented for both types of lining. The transmission of sound through the duct is then calculated using the mode-matching technique. The mode-matching model allows analysis of multi-modal wave propagation in the duct. The model is first developed for an infinitely long rigid duct with a finite length of lined insert. The estimation from the locally reacting model, that is widely available in the literature, is compared with the estimation from the newly developed bulk-reacting model. Although the locally reacting model often overestimates the performance of a bulk-reacting lining it is found that this is not always the case, especially for a small lining thickness and at lower frequencies where the locally reacting model may under-estimate the performance. The analytical model is then extended to a multi-segmented lining where the lined section is uniformly segmented with rigid walled sections in a periodic manner. For a bulk-reacting lining, the segmented arrangement renders the lining more similar to the behaviour of a duct with a locally-reacting lining and improves the peak attenuation. Little improvement is found in the case of a multi-segmented locally-reacting lining. The effect of duct height, lining thickness and lining flow resistivity on sound attenuation is studied using the analytical model. Experiments are presented which validate the analytical model.
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Hosseini, Ehsan. "The analytical modelling of collective capability of human networks." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/12445.
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This thesis is an attempt to propose an analytical model for estimating and predicting capability in human networks (i.e. work teams). Capability in this context is the ability to utilise the collective inherent and acquired resources of individuals to complete a given task. The motivation of proposing a method for measuring collective capability of teams is to assist project managers and team builders to allocate and assign “The most capable teams” to a project to maximise the likelihood of success. The review of literature in engineering, human sciences and economics has led to a definition of capability. One of the key findings of this research work is that collective capability can be predicted by: 1. Demographic homophily of members of the team, 2. The diversity of skills that each member brings to the team, 3. The past experience or attainments of the members, and 4. The strength of relationship amongst the members of the team. The influence of the four predictors of capability is investigated through the design of empirical surveys conducted among postgraduate students over a period of 2 years. The data collected from the surveys are used to assess the correlation between the predictors and the dependent variable using standard statistical methods. The conclusions of the study confirm that there are positive and significant relationships between the independent predictors and collective capability of project teams. The demographic homophily of the individuals in team and their instrumental (task related) relationships’ strength become the two most effective predictors which have the highest effect on the collective capability of a team as a whole. The skills diversity of the members in a group and their previous level of attainments/experiences in similar projects were also proved to be effective factors (with lower level of effect) in increasing the capability of the whole team in fulfilling the requirements of a pre-defined project.
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Kendall, James D. (James Douglas) 1959 Carleton University Dissertation Engineering Electrical. "Two-dimensional analytical modelling of the short-channel mosfet." Ottawa.:, 1987.
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Msadala, V. P. "Sediment yield prediction based on analytical methods and mathematical modelling." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2863.
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Thesis (MScEng (Civil Engineering)--University of Stellenbosch, 2009.ENGLISH ABSTRACT: A study of the state of reservoir sedimentation in South Africa based on reservoir sediment deposit data, has shown that a considerable number of reservoirs have serious sedimentation problems. The analysis of the reservoir sediment deposit data showed that almost 25% of the total number of reservoirs have lost between 10 to 30% of their original storage capacity. The average storage loss due to sedimentation in South African reservoirs is approximately 0.3% per year while the average annual storage loss for all the reservoirs in the world is 0.8%. The aim of this research was to develop sediment yield prediction methods based on analytical approaches and mathematical modelling. The sediment yield prediction methods can be used in planning and management of water resources particularly in reservoir sedimentation control. The catchment erosion and sediment yield modelling methods can be applied in temporal and spatial analysis of sediment yields which results are essential for detailed design of water resources, particularly in the identification of critical erosion areas, sediment sources and formulation of catchment management strategies. Current analytical methods for the prediction of sediment yield have been reviewed. Nine sediment yield regions have been demarcated based on the observed sediment yields and catchment characteristics. Empirical and probabilistic approaches were investigated. The probabilistic approach is based on analysis of the observed sediment yields that were calculated from reservoir sediment deposit, river suspended sediment sampling data and soil erodibility data. The empirical equations have been derived from regression analysis of the variables that were envisaged to have a significant effect on erosion and sediment yields in South Africa. Empirical equations have been developed and shown to have accurate and reliable predictive capability in six of the nine regions. The probabilistic approach has been recommended for the prediction of sediment yields in the remaining three regions where reliable regression equations could not be derived. The predictive accuracy of both the probabilistic and empirical approaches was checked and verified using the discrepancy ratio and graphs of the observed and calculated data. While the analytical methods are needed to predict the sediment yield for the whole catchment, mathematical modelling to predict sediment yields is applied for more detailed analysis of sediment yield within the catchment. An evaluation of available catchment sediment yield mathematical modelling systems was carried out. The main criteria for the choice of a numerical model to be adopted for detailed evaluation was based on the following considerations: the model’s capabilities, user requirements and its application. The SHETRAN model (Ewen et al., 2000) was therefore specifically chosen because of its ability to simulate relatively larger catchment areas (it can handle catchment scales from less than 1km2 to 2500km2), its ability to simulate erosion in channels, gullies and landslides, its applicability to a wide range of land-use types and ability to simulate land use changes. Another model, ACRU (Smithers et al., 2002) was also reviewed. The aim of the model evaluation was to provide a conceptual understanding of catchment sediment yield modelling processes comprising model set up, calibration, validation and simulation. The detailed evaluation of the SHETRAN model was done through a case study of Glenmaggie Dam in Australia. The flow was calibrated and validated using data from 1975 to 1984, and 1996 to 2006 respectively. The results for both the calibration and validation were reasonable and reliable. The sediment load was validated against turbidity derived sediment load data from 1996 to 2006. The model was used to identify sources of sediment and areas of higher sediment yield. The land use of a selected sub-catchment was altered to analyse the impact of land use and vegetative cover on the sediment yield. Based on the results, the SHETRAN model was confirmed to be a reliable model for catchment sediment yield modelling including simulation of different land uses.
AFRIKAANSE OPSOMMING: ‘n Studie van die stand van damtoeslikking in Suid-Afrika toon dat daar ernstige toeslikkingsprobleme by baie reservoirs bestaan. ’n Ontleding van die toeslikkingsyfers gegrond op damkomopmetings toon dat omtrent 25% van die totale getal reservoirs tussen 10 en 30% van hulle oorspronklike opgaarvermoë verloor het. Die gemiddelde tempo van damtoeslikking in Suid-Afrika is 0.3%/jaar, wat laer is as die wêreld gemiddeld van 0.8%/jaar. Die oogmerk met hierdie navorsing was om sedimentlewering voorspellingsmetodes te ontwikkel deur gebruik te maak van analitiese metodes en wiskundige modellering. Die sedimentlewering voorspellingsmetodes kan gebruik word vir die beplanning en bestuur van waterbronne en veral vir damtoeslikking beheer. Die opvangsgebied erosie en die sedimentlewering modelleringsmetodes kan toegepas word in tydveranderlike en ruimtelike ontleding van sedimentlewering. Hierdie inligting word benodig vir die detail ontwerp van waterhulpbronne en veral vir die identifisering van kritiese erosiegebiede, bronne van sediment en die formulering van opvangsgebied-bestuur strategië. ‘n Literatuuroorsig oor die huidige metodes vir die voorspelling van erosie en sedimentlewering is gedoen. Nege sedimentasie streke is afgebaken in Suid-Afrika, gegrond op waargenome damtoeslikkingsdata en opvangsgebied-eienskappe. Proefondervindelike en waarskynlikheidsbenaderinge is ondersoek. Die waarskynlikheidsbenadering is gegrond op die ontleding van waargenome damtoeslikking wat bereken is uit reservoir opmeting data en rivier gesuspendeerde sediment data, asook data oor gronderosie. Die proefondervindelike metode se vergelykings is afgelei vanuit regressie ontleding van die veranderlikes wat ‘n belangrike invloed het op die erosie en sedimentlewering in Suid-Afrika. Daar is bevestig dat die ontwikkelde proefondervindelike (empiriese) vergelykings ‘n akkurate en betroubare voorspellingsvermoë in ses van die nege streke het. Die waarskynlikheidsbenadering is aanbeveel vir die voorspelling van sedimentlewering in die ander drie streke, waar betroubare regressie vergelykings nie afgelei kon word nie. Die voorspellingsakkuraatheid van albei metodes is nagegaan en bevestig deur gebruik te maak van die teenstrydigheidsverhouding en grafieke van die waargenome en berekende data. Analitiese metodes van sedimentleweringsvoorspelling is nodig vir ‘n volle opvangsgebied, terwyl wiskundige modellering om sedimentlewerings te voorspel gebruik kan word om ‘n meer in diepte ontleding van die sedimentlewering binne ‘n opvanggebied te doen. ‘n Evaluasie van beskikbare wiskundige modelle wat opvangsgebied sedimentlewering kan voorspel, is gedoen. Die hoofkriteria vir die keuse van ‘n model vir gebruik by gedetailleerde ontleding is gegrond op die volgende: die vermoëns van die model, wat verbruikers benodig en die aanwending van die model. Die SHETRAN model (Ewen et al., 2000) is spesifiek gekies weens sy vermoë om relatief groter opvangsgebiede te simuleer (dit kan opvangsgebiede van 1km2 tot 2500km2 wees) asook om erosie in kanale, dongas en grondverskuiwing simuleer. Dit kan toegepas word op ‘n wye reeks grondtipes en kan ook die gevolge simuleer as die gebruik van die grond verander. ‘n Ander model, ACRU (Smithers et al., 2002) is ook ondersoek. Die doel van die modelevaluering was om ‘n konseptuele begrip te kry van sedimentlewering modelleringsprosesse wat die opstelling, kalibrasie, toetsing en simulasies insluit. Die volledige evaluasie van SHETRAN is gedoen deur middel van ‘n gevalle-studie van die Glenmaggiedam in Australia. Die riviervloei is gekalibreer en getoets deur gebruik te maak van data wat strek van 1975 tot 1984, en van 1996 tot 2006 onderskeidelik. Die resultate van beide die kalibrasie en die toetswas redelik en betroubaar. Die sedimentlading is gekalibreer teen velddata van 1996 tot 2006. Die model is gebruik om bronne van sediment te identifiseer, asook gebiede met ‘n hoër sedimentlewering. Die gebruik van die grond op ‘n gekose sub-opvangsgebied is verander om die impak van grondgebruik en plantbedekking op sedimentlewering te ontleed. Die resultate bewys dat die SHETRAN model ‘n betroubare model is vir groot opvangsgebied sedimentlewering modellering, asook vir die simulasie van verskillende grondgebruike.
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Vosloo, Surika. "Analytical modelling and optimization of a thermal convective microfluidic gyroscope." Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4135.
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Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: This thesis deals with the mathematical optimization of the detecting chamber of a thermal convective microfluidic gyroscope and the comparison of several different optimization strategies. An analytical model is developed for the gyroscope and some design considerations are discussed. Sequential approximate optimization strategies are explained and compared to each other by implementing test problems fromthe literature. The optimization problem is formulated from the analytical model and implemented using the different optimization strategies. Results are presented and compared to find the most effective optimization strategy. A sequential approximate optimization algorithm is implemented in MATLAB and tested using the gyroscope design problem and common test problems from the literature. Results and iteration history are compared with an existing FORTRAN implementation.
AFRIKAANSE OPSOMMING: Hierdie tesis handel oor die wiskundige optimering van die deteksiekamer van n termies-konvektiewe mikrovloeier giroskoop en die vergelyking van verskeie optimeringsstrategieë. ’n Analitiese model is opgestel vir die giroskoop en verskeie ontwerpsoorwegings word bespreek. Sekwensiëel benaderde optimeringsstrategieë word bespreek en met mekaar vergelyk, deur dit op toetsprobleme uit die literatuur toe te pas. Die optimeringsprobleem is geformuleer uit die analitiese model en geimplementeer deur gebruik te maak van verskeie optimeringsstrategieë. Resultate word getoon en vergelyk, omdie mees effektiewe optimeringsstrategie te vind. ’n Algoritme vir sekwensiëel benaderde optimeringsprobleme is inMATLAB geimplementeer. Die giroskoop probleem, asook probleme uit die literatuur, is gebruik om resultate en iterasie geskiedenis te vergelyk met ’n bestaande FORTRAN implementasie.
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Ziebart, Marek. "High precision analytical solar radiation pressure modelling for GNSS spacecraft." Thesis, University of East London, 2001. http://roar.uel.ac.uk/3563/.
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In global navigation satellite systems (GNSS) a fundamental operational component is the calculation of the orbits of the system spacecraft. This requires understanding and modelling the forces that act on the spacecraft. Solar radiation pressure (SRP) is the force caused by the impact of solar photons on the spacecraft surface. For GNSS spacecraft this is a significant force. If SRP is not included in the force model, then the calculated position of the spacecraft can be in error by between one and two hundred metres after one 12-hour orbit. SRP can be modelled using either analytical or empirical methods, or by some combination of the two. Historically, analytical SRP modelling has been somewhat neglected and high precision orbit estimation has relied upon empirical methods to account for SRP. Even so, most of these empirical methods start the estimation process with an a priori analytical model. The success of this empirical approach relies upon having many observations of the range between the system spacecraft and ground-based tracking stations, and works well within the context of the International Global Positioning System Service (IGS) network, which provides the necessary data volume. However, empirical methods do not work as well in operational GNSS, as these typically have a relatively small number of tracking stations. Moreover, empirical methods cannot be applied at the GNSS design stage, where knowledge of the system dynamics plays a key role. Existing methods for calculating analytical SRP models can only be used with relatively simple spacecraft structures, and lack flexibility as tools for analysis. In this study a new method is developed for calculating analytical SRP models that can cope with a high level of complexity in the spacecraft structure. The method is based upon simulating the solar photon flux with a pixel array. Using the method, models are calculated and tested for the Russian GLONASS IIv spacecraft. This particular spacecraft was used as the testbed because, at the time the study was being conducted, an international scientific campaign - called IGEX-98, the International GLONASS Experiment - was being carried out to analyse the Russian system. Developing force models for the spacecraft was one of the campaign goals, and the IGEX-98 steering committee accepted a proposal to use SRP models for GLONASS from this study. A detailed description is given of all the mathematics and physics that was used to develop the modelling technique. The method by which the models can be calculated and applied in practical orbit determination is also provided. In order to test the performance of the SRP models computed for the GLONASS spacecraft using the new method, comparisons were made between two kinds of trajectory. The first kind was calculated by numerical integration of the spacecraft's second order differential equation of motion, where this force model included the custom SRP models developed in the thesis. The second kind of trajectory, which is used as a 'truth' model in the study, was a precise orbit computed by the University of Berne using IGS range data and an empirical SRP model. Such precise orbits are the best estimates available of the true trajectories, as they are derived from the simultaneous estimation of multiple receiver tracking station network positions and spacecraft force model parameters. The repeatability of the Berne orbit is circa 0.75m. The RMS differences between the two trajectories over one twelve-hour orbit (an arc length of circa 160,000km) were 0.7m in height, 1.3m across track and 3.5m along track. This shows that the trajectory derived from the force model alone is very close to the precise orbit. The time-varying pattern of the differences between the two trajectories strongly indicates that the residual mismodelling of the forces acting on the spacecraft is due to thermal re-radiation effects. Further tests of the method were also conducted using satellite laser ranging (SLR) data to calculate arc lengths of 400 days, again using SRP models from the study. This enabled the calculation of model scale factors and additional empirical terms. The average SRP model scale factor was circa 1.01, which implies that the average error in the a priori SRP models calculated for the GLONASS IIv spacecraft is at the 1% level. This is consistent with an error budget based on an assessment of the accuracy of the source data supplied by the Russian authorities. The magnitude and parameterisation of the SLR empirical terms again strongly suggest that most of the remaining mis-modelling is caused by thermal effects. An analysis is given of the effect on the a priori SRP model of unmodelled, SRP-related forces acting along the spacecraft Y-axis. This is the so-called Y-bias. It is shown that whilst Y-bias effects are important in orbit determination, they are less critical in the process of calculating the a priori SRP model. A discussion is provided on how the new method can be adapted to improve the modelling and understanding of thermal re-radiation and Y-bias effects, and also on what benefits might accrue from such studies. The new method is an improvement over existing techniques as it enables the calculation of high precision SRP models that can be applied in the design, operation and scientific analysis of GNSS. A UK patent application has been made in respect of the new method.
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Minton, Jeremy John. "Mathematical modelling of asymmetrical metal rolling processes." Thesis, University of Cambridge, 2017. https://www.repository.cam.ac.uk/handle/1810/270348.
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This thesis explores opportunities in the mathematical modelling of metal rolling processes, specifically asymmetrical sheet rolling. With the application of control systems in mind, desired mathematical models must make adequate predictions with short computational times. This renders generic numerical approaches inappropriate. Previous analytical models of symmetrical sheet rolling have relied on ad hoc assumptions about the form of the solution. The work within this thesis begins by generalising symmetric asymptotic rolling models: models that make systematic assumptions about the rolling configuration. Using assumptions that apply to cold rolling, these models are generalised to include asymmetries in roll size, roll speed and roll-workpiece friction conditions. The systematic procedure of asymptotic analysis makes this approach flexible to incorporating alternative friction and material models. A further generalisation of a clad-sheet workpiece is presented to illustrate this. Whilst this model was formulated and solved successfully, deterioration of the results for any workpiece inhomogeneity demonstrates the limitations of some of the assumptions used in these two models. Attention is then turned to curvature prediction. A review of workpiece curvature studies shows that contradictions exist in the literature; and complex non-linear relationships are seen to exist between asymmetries, roll geometry and induced curvature. The collated data from the studies reviewed were insufficient to determine these relationships empirically; and neither analytical models, including those developed thus far, nor linear regressions are able to predict these data. Another asymmetric rolling model is developed with alternative asymptotic assumptions, which shows non-linear behaviour over ranges of asymmetries and geometric parameters. While quantitative curvature predictions are not achieved, metrics of mechanisms hypothesised to drive curvature indicate these non-linear curvature trends may be captured with further refinement. Finally, coupling a curved beam model with a curvature predicting rolling model is proposed to model the ring rolling process. Both of these parts are implemented but convergence between them is not yet achieved. By analogy this could be extended with shell theory and a three-dimensional rolling model to model the wheeling process.
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Doan, Luong T. "Analytical and numerical modelling of transient convective transfers on SAGD performance." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2001. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/NQ60286.pdf.
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Vafai, Fereydoon. "Analytical modelling and laboratory studies of particle transport in filter media." Online version, 1996. http://bibpurl.oclc.org/web/23534.
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Parry, M. R. "Finite element and analytical modelling of roughness induced fatigue crack closure." Thesis, University of Southampton, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342763.
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Crofts, Jonathan Daniel. "Analytical modelling of multi-spacecraft reconnection layer measurements at the magnetopause." Thesis, University of Sussex, 2011. http://sro.sussex.ac.uk/id/eprint/6338/.
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An approach to determine and analyse the structure of Petschek-type magnetic reconnection is developed. This is achieved by extending an analytical model based on the Rankine-Hugoniot wave equation for shock jump conditions and is described in terms of its past applications and limitations. The model is applied to data from the CLUSTER multi-spacecraft mission using a boundary condition method optimised by two interlinked genetic algorithms. Case studies for a range of locations within the magnetopause region and local conditions are described and subjected to fluid and particle analyses to confirm the presence of reconnective signatures. Genetic algorithms are used to optimise the fit of the model, by modifying the boundary condition selection and internal structure parameters. This information then facilitates the construction of a more accurate modelled layer structure for each event. The calculated values for state variables within these layers are compared quantitatively and qualitatively to the magnetopause boundary crossings present in the CLUSTER data. Case study results are summarised and compared before being compiled into quantitative statistics for describing the local and possibly global applicability of the model. The fast application of these methods by means of an automatic process to a large set of data is described, as are the wider possibilities arising from this and the limitations of model, methods and data. These results are used to support several assertions. Firstly, that this model is indeed applicable, within its limitations, to the study of reconnection events within the magnetospheric environment. It can also facilitate deeper studies of individual reconnection events, in addition to being employed as a basis to classify wider statistical trends in spatio-temporal structures.
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Reyes, Olivia Maria Lei. "Experimental study and analytical modelling of compressive fracture in brittle materials." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13869.
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Al-Aasam, Hameed. "Modern engineering design : analytical and numerical modelling of semi-rigid connections." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/modern-engineering-design-analytical-and-numerical-modelling-of-semirigid-connections(cdf16391-fc23-4a1a-aa15-443e0ae5adf3).html.
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The concept of semi-rigid connection and steel-concrete composite action has been extensively researched in the past. However, they are not widely used in practice due to the lack of detailed information, not only about the advantages of the semi-rigid design philosophy, but also about the potential risks if its effect is not accounted for. The above considerations were the motivations in taking up this research. Firstly, a numerical study to investigate the effect of connection stiffness on the natural frequency of semi-rigid frame was carried out using ABAQUS software. The results of this numerical study confirmed the necessity of incorporating this effect to get safe and economical design. Consequently, an analytical procedure for a beam with semi-rigid connections under gravity load was developed which overcomes the limitations of previously published procedures. The frequency of a steel beam was also calculated using effective length concept. Furthermore, two new analytical “hand’’ calculation methods to estimate the first three frequencies of a semi-rigid frame were developed. Both methods were developed by modifying or improving for existing methods in the literature for rigid-jointed plane steel frame to incorporate the effect of connection stiffness. Fist method is suitable only for a semi-rigid plane steel frame which has uniform properties along its height so as it can be modelled as equivalent flexural-shear cantilever beam. The proposed second method is suitable for non-uniform plane steel frame. Both the above methods can be extended to composite structure using the equivalent stiffness concept of composite beam. Moreover, examples of steel frame were used to demonstrate the application of the proposed analytical methods. It was shown that the proposed methods not only can predict the difference in frequency of rigid and semi-rigid frames, but they are also simple enough to be used in day-to-day design practices. Secondly, as the stiffness of connection is essential in the calculation of natural frequency of a semi-rigid frame, a new simple mechanical component-based model was developed to determine the initial rotational stiffness of commonly used flush end-plate steel or composite connection incorporating the partial interaction effect. The traditional axial spring of shear connectors was replaced by rotational spring to make the model suitable to extending further than the linear region. A chart was developed to estimate the appropriate values of the secant stiffness and strength of a shear stud, since the empirical equations that researchers have used in the past can lead to unrealistic results in some cases. Thirdly, a simplified model, which combined three components of a composite connection in one “lump’’ component (RCCS), was developed. It can be used in the finite element modelling of a composite connection to overcome the convergence problems associated with cracking of concrete and also it will reduce the computational time significantly with adequate accuracy. A new procedure to determine the number of “active’’ studs was developed. The relationship between the number of “active’’ shear studs and the maximum number of shear studs required for a full shear connection was derived. Finally, the relationship between connection ductility and frame ductility was investigated. It was found that the moment resistance and ductility of connection affect significantly the whole behaviour of a frame. Consequently, a simple flowchart to predict the failure mode of a flush end-plate composite connection was developed. A procedure to estimate the moment resistance of a flush end-plate composite connection by modifying the existing procedures in the literature to incorporate the partial shear connection effect was proposed. Also, the proposed mechanical model was further extended using the appropriate post-linear values of its components in order to calculate the rotational ductility of a connection. All the suggested procedures have been validated with the numerical results using ABAQUS, the results from other existing models and experimental tests in the literature where available.
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Lee, Nang Lap. "Analytical, centrifuge and numerical modelling of underwater vacuum consolidation of soft clay /." View abstract or full-text, 2007. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202007%20LEEN.
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Murcia, A. J. (Armando J. ). "Analytical modelling of the performance of a snow deposit under plate loading." Thesis, McGill University, 1987. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=64057.
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Venet, Aurele. "Semi-analytical modelling of the star formation history in a dusty universe." Thesis, Imperial College London, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.271685.
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Wu, Lijian. "Analytical modelling of electromagnetic performance and parasitic effects of permanent magnet machines." Thesis, University of Sheffield, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.647997.
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Barker, Peter Jay. "Analytical and simulation performance modelling of indoor infrared wireless data communications protocols." Thesis, Bournemouth University, 2003. http://eprints.bournemouth.ac.uk/302/.
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The Infrared (IR) optical medium provides an alternative to radio frequencies (RF) for low cost, low power and short-range indoor wireless data communications. Low-cost optoelectronic components with an unregulated IR spectrum provide the potential for very high-speed wireless communication with good security. However IR links have a limited range and are susceptible to high noise levels from ambient light sources. The Infrared Data Association (IrDA) has produced a set of communication protocol standards (IrDA I. x) for directed point-to-point IR wireless links using a HDLC (High-level Data Link Control) based data link layer which have been widely adopted. To address the requirement for multi-point ad-hoc wireless connectivity, IrDA have produced a new standard (Advanced Infrared -AIr) to support multiple-device non-directed IR Wireless Local Area Networks (WLANs). AIr employs an enhanced physical layer and a CSMA/CA (Carrier Sense Multiple Access with Collision Avoidance) based MAC (Media Access Control) layer employing RTS/CTS (Request To Send / Clear To Send) media reservation. This thesis is concerned with the design of IrDA based IR wireless links at the datalink layer, media access sub-layer, and physical layer and presents protocol performance models with the aim of highlighting the critical factors affecting performance and providing recommendations to system designers for parameter settings and protocol enhancements to optimise performance. An analytical model of the IrDA 1.x data link layer (IrLAP Infrared Link Access -Protocol) using Markov analysis of the transmission window width providing saturation condition throughput in relation to the link bit-error-rate (BER), datarate andprotocol parameter settings is presented. Results are presented for simultaneous optimisation of the data packetsize and transmission window size. A simulation model of the IrDA l. x protocol, developed with OPNETTM Modeler, is used for validation of analytical results and to produce non-saturation throughput and delay performance results. An analytical model of the AIr MAC protocol providing saturation condition utilisation and delay results in relation to the number of contending devices and MAC protocol parametersis presented.Results indicate contention window size values for optimum utilisation. The effectiveness of the AIr contention window linear back-off process is examined through Markov analysis. An OPNET simulation model of the Alf protocol is used for validation of the analytical model results and provides non-reservation throughput and delay results. An analytical model of the IR link physical layer is presented and derives expressions for signal-to-noise ratio (SNR) and BER in relation to link transmitter and receiver characteristics, link geometry, noise levels and line encoding schemes. The effect of third user interference on BER and resulting link asymmetry is also examined, indicating the minimum separation distance for adjacent links. Expressions for BER are linked to the data link layer analysis to provide optimum throughput results in relation to physical layer propertiesandlink distance.
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Greco, Angelo. "Numerical and analytical modelling of battery thermal management using passive cooling systems." Thesis, Lancaster University, 2016. http://eprints.lancs.ac.uk/78600/.
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This thesis presents the battery thermal management systems (BTMS) modelling of Li-ions batteries and investigates the design and modelling of different passive cooling management solutions from single battery to module level. A simplified one-dimensional transient computational model of a prismatic lithium-ion battery cell is developed using thermal circuit approach in conjunction with the thermal model of the heat pipe. The proposed model is compared to an analytical solution based on variable separation as well as three-dimensional (3D) computational fluid dynamics (CFD) simulations. The three approaches, i.e. the 1D computational model, analytical solution, and 3D CFD simulations, yielded nearly identical results for the thermal behaviours. Therefore the 1D model is considered to be sufficient to predict the temperature distribution of lithium-ion battery thermal management using heat pipes. Moreover, a maximum temperature of 27.6ºC was predicted for the design of the heat pipe setup in a distributed configuration, while a maximum temperature of 51.5ºC was predicted when forced convection was applied to the same configuration. The higher surface contact of the heat pipes allows a better cooling management compared to forced convection cooling. Accordingly, heat pipes can be used to achieve effective thermal management of a battery pack with confined surface areas. In addition, the thermal management of a cylindrical battery cell by a phase change material (PCM) / compressed expanded natural graphite (CENG) is investigated. The transient thermal behaviour of both the battery and the PCM/CENG is described with a simplified onedimensional model taking into account the physical and phase change properties of the PCM/CENG composite. The 1D analytical/computational model predicted nearly identical results to the three-dimensional simulation results for various cooling strategies. Therefore, the 1D model is sufficient to describe the transient behaviour of the battery cooled by a PCM/CENG composite. Moreover, the maximum temperature reached by the PCM/CENG cooling strategy is much lower than that by the forced convection in the same configuration. In the test case studied, the PCM showed superior transient characteristics to forced convection cooling. The PCM cooling is able to maintain a lower maximum temperature during the melting process and to extend the transient time for temperature rise. Furthermore, the graphite-matrix bulk density is identified as an important parameter for optimising the PCM/CENG cooling strategy. Finally, the lithium-ion battery cooling using a passive cooling material (PCM) / compressed expanded natural graphite (CENG) composite is investigated for the battery module scale. An electrochemistry model (average model) is coupled to the thermal model, with the addition of a one-dimensional model for the solution and solid diffusion using the nodal network method. The analysis of the temperature distribution of the battery module scale has shown that a twodimensional model is sufficient to describe the transient temperature rise. In consequence, a two-dimensional cell-centred finite volume code for unstructured meshes is developed with additions of the electrochemistry and the phase change. This two-dimensional thermal model is used for investigating a new and usual battery module configurations cooled by PCM/CENG at different discharge rates. The comparison of both configurations with a constant source term and heat generation based on the electrochemistry model, showed the superiority of the new design. In this study, comparisons between the predictions from different analytical and computational tools as well as open-source packages were carried out, and close agreements have been observed.
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Brossier, Pierre. "Combined analytical and empirical modelling of power losses in rolling element bearings." Thesis, Lyon, 2020. http://www.theses.fr/2020LYSEI081.
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Le développement de l’industrie du transport conduit la conception de transmissions mécaniques de puissance toujours plus légères et efficientes. Les composants de ces transmissions doivent supporter des efforts transmis dans des environnements de plus en plus restreints. Du fait que les carters soient devenus de plus en plus compacts, les systèmes de refroidissement se sont aussi complexifiés. C’est dans ce contexte que les paliers à roulement, plus communément appelés roulements, doivent produire moins de chaleur, opérer dans des espaces plus proches des engrènements, tout en ayant des durées de vie plus grandes. Le calcul des pertes énergétiques des roulements est essentiel pour quantifier la quantité d’huile à injecter pour refroidir ces composants. L’objectif de cette étude est donc de fournir des outils pour modéliser les pertes dans les roulements et leur comportement thermique. Dans un premier temps, une analyse bibliographique a été menée sur les pertes de puissance dans les roulements, incluant des modèles locaux et globaux de pertes de puissance. Un banc d’essais dédié a été utilisé afin d’analyser les puissances dissipées et la thermique de roulements à billes à gorge profonde. Les influences de la vitesse de rotation, du chargement, de la température d’injection, du débit d’huile injecté, des techniques de lubrification ont été examinées. Les modèles globaux précédemment investigués ont été comparés aux données expérimentales. Enfin, un modèle thermique a été développé pour comprendre l’influence des transferts de chaleur dans les pertes de puissance générées par les roulements. Des comparaisons entre différentes lubrifications et différentes géométries ont été faites. Une nouvelle formule du couple résistif a été proposée pour mieux prendre en compte la géométrie du roulement considéréThe development of the transport industry has led to design lighter and more efficient transmission systems. The components within these transmissions have to withstand the transmitted loads in closer environments. As the housing has become more compact than ever, the cooling system has also become more complex. In that context, Rolling Element Bearings (REBs) are required to produce less heat, to work closer to the gear meshes while having higher life-expectancies. The calculation of REB power loss is essential to quantity the amount of injected oil to cool off these components. This study therefore aims at providing tools to model REB power loss and their thermal behaviour. As a first step, a bibliographical survey was conducted on REB power losses, including local and global models. A dedicated test rig has been used to analyse the power losses and the thermal behaviour of Deep Groove Ball Bearings. The influence of rotational speed, load, oil injection temperature, oil flow rate and lubrication design has been investigated. The above-mentioned global models have been compared to the experimental data. Finally, a REB thermal model has been developed in order to understand the influence of heat-transfer within REBs on power losses. Comparisons between different lubrication designs and between different geometries have been done. A new formulation to better take into account the REB geometry in the global models has been proposed
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Gervilla, Palomar Víctor. "Metal film growth on weakly-interacting substrates : Stochastic simulations and analytical modelling." Licentiate thesis, Linköpings universitet, Nanodesign, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-154428.
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Thin films are nanoscale layers of material, with exotic properties useful in diverse areas, ranging from biomedicine to nanoelectronics and surface protection. Film properties are not only determined by their chemical composition, but also by their microstructure and roughness, features that depend crucially on the growth process due to the inherent out-of equilibrium nature of the film deposition techniques. This fact suggest that it is possible to control film growth, and in turn film properties, in a knowledge-based manner by tuning the deposition conditions. This requires a good understanding of the elementary film-forming processes, and the way by which they are affected by atomic-scale kinetics. The kinetic Monte Carlo (kMC) method is a simulation tool that can model film evolution over extended time scales, of the order of microseconds, and beyond, and thus constitutes a powerful complement to experimental research aiming to obtain an universal understanding of thin film formation and morphological evolution. In this work, kMC simulations, coupled with analytical modelling, are used to investigate the early stages of formation of metal films and nanostructures supported on weakly-interacting substrates. This starts with the formation and growth of faceted 3D islands, that relies first on facile adatom ascent at single-layer island steps and subsequently on facile adatom upward diffusion from the base to the top of the island across its facets. Interlayer mass transport is limited by the rate at which adatoms cross from the sidewall facets to the island top, a process that determines the final height of the islands and leads non-trivial growth dynamics, as increasing temperatures favour 3D growth as a result of the upward transport. These findings explain the high roughness observed experimentally in metallic films grown on weakly-interacting substrates at high temperatures. The second part of the study focus on the next logical step of film formation, when 3D islands come into contact and fuse into a single one, or coalesce. The research reveals that the faceted island structure governs the macroscopic process of coalescence as well as its dynamics, and that morphological changes depend on 2D nucleation on the II facets. In addition, deposition during coalescence is found to accelerate the process and modify its dynamics, by contributing to the nucleation of new facets. This study provides useful knowledge concerning metal growth on weakly-interacting substrates, and, in particular, identifies the key atomistic processes controlling the early stages of formation of thin films, which can be used to tailor deposition conditions in order to achieve films with unique properties and applications.
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Montazemi, M. "Capacity planning of computer systems and packet switched networks using analytical modelling." Thesis, University of Sussex, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.374463.
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Graziani, Lorenzo. "Nano-engineered brick surfaces for biofouling prevention: experimental results and analytical modelling." Doctoral thesis, Università Politecnica delle Marche, 2015. http://hdl.handle.net/11566/242914.
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Le facciate degli edifici sono inevitabilmente soggette al deterioramento causato dalla colonizzazione di microorganismi quali batteri, alghe, cianobatteri, funghi, licheni, etc.
Oltre ai tradizionali metodi manutentivi, si stanno sviluppando rivestimenti innovativi con caratteristiche sfavorevoli allo sviluppo di macchie biologiche.
In questa direzione, si sta sviluppando l’applicazione di nanotecnologie, in particolare nano-rivestimenti fotocatalitici. Il materiale più diffuso in questo settore è il biossido di titanio (TiO2) grazie alla sua non-tossicità, stabilità foto-chimica e basso costo.
La ricerca ha l’obiettivo di studiare l’efficienza del TiO2 contro la bio-incrostazione algale su superfici in laterizio. La ricerca si concentra sull’abilità del TiO2 di limitare l’adesione delle cellule algali sotto l’azione dei raggi UV e in condizioni di luce visibile. Inoltre, vengono analizzate le relazioni tra il substrato e l’efficienza fotocatalitica, principalmente la rugosità e la porosità.
L’attività sperimentale consiste nel sottoporre campioni di laterizio a cicli di bagnatura/asciugatura con una sospensione algale, in condizioni climatiche controllate. La bio-incostrazione è stata valutata nel tempo attraverso l’analisi digitale dell’immagine e misure colorimetriche.
I risultati hanno evidenziato che il TiO2 ha l’abilità di inibire l’attecchimento delle cellule algali e in alcuni casi è in grado di arrestare del tutto la crescita dei microorganismi. L’efficienza è strettamente legata alla porosità e alla rugosità del substrato. Infine, l’addizione di nano-particelle di Ag e Cu alla soluzione di TiO2 non ha evidenziato miglioramenti significativi.
La ricerca, partendo dai dati sperimentali, ha sviluppato un modello analitico basato sulla legge di Avrami. Il modello ha dimostrato un’ottima accuratezza nel riprodurre i risultati sperimentali e può essere potenzialmente applicato per la predizione del processo di bio-incrostazione su reali facciate in laterizio.Building façades, including brick façades, are inevitably subjected to the deterioration caused by the colonization of microorganisms. These microorganisms may be bacteria, algae, cyanobacteria, fungi, lichens and other. Algae and cyanobacteria are the first colonizers, which pave the way for the implantation and growth of other microorganisms systems. Beyond traditional intervention methods, innovative coatings with unfavourable intrinsic parameters to the development of biological stains are now developing. In this direction, the use of nanotechnology, especially the use of photocatalytic nanocoating, has recently raised. The most diffuse material in nanocoating applications is titanium dioxide (TiO2) because of its non-toxicity, photochemical stability and low cost. This research aims to study the efficiency of TiO2 toward algal biofouling when it is applied on brick elements. The research focuses on the ability of TiO2 to limit the adhesion of algal cells under both UV and visible radiation. Moreover, it studies the effect of substrata properties, mainly roughness and porosity, on the biocide effect of TiO2. Experimental activity, at the base of this research, consists to subject brick specimens to wet&dry cycles with algae suspension, under monitored climatic conditions. Biofouling was measured through time by digital image analysis and colorimetric measurements. Results show that TiO2 was able to inhibit the algal adhesion, in some cases, it is able to completely stop the growth of microorganisms. The efficiency of TiO2 is strictly related to physical properties of substrata like porosity and roughness. The addition of other noble metal (Ag, Cu) to the TiO2 solution seems to produce no significant improvement. This research extends experimental results to numerical modelling by applying the Avrami's law. The model shown to be adequate to reproduce laboratory tests and it has the potential to be applied for biofouling prediction on real building façades.
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Tvinghagen, Adam. "Arching Stability in Shallow Tunnels : A comparison between analytical and numerous solutions." Thesis, KTH, Jord- och bergmekanik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-187031.
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Haldimann, Matthias. "Fracture strength of structural glass elements : analytical and numerical modelling, testing and design /." Lausanne : EPFL, 2006. http://library.epfl.ch/theses/?nr=3671.
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Thèse sciences, EPF Lausanne, no 3671 (2006), Faculté Environnement naturel, architectural et construit ENAC, Section de génie civil (Laboratoire de la construction métallique). Directeur: M.A. Hirt ; rapporteurs: M.H. Faber... et al.Register. Literaturverz.
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Rosario, Maria C. P. "Applications of population and other analytical approaches to pharmacokinetic and pharmacokinetic/pharmacodynamic modelling." Thesis, University of Glasgow, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.272881.
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Meredith, Jeffrey A. "Numerical and analytical modelling of downhole seismic sources--the near and far field." Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13755.
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Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1991.Includes bibliographical references (leaves 173-182).
by Jeffrey A. Meredith.
Sc.D.
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Mo, Pin-Qiang. "Centrifuge modelling and analytical solutions for the cone penetration test in layered soils." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14319/.
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The interpretation of measurements from the cone penetration test is still predominately based on empirical correlations, which can be attributed to the lack of understanding of penetration mechanisms, that involve severe stress-strain and shear dilatancy close to the probe. Even so, it remains one of the most widely used in-situ tools for site characterisation, and several methods for displacement pile design have been developed using CPT data. This research investigates the response of penetrometers and the behaviour of layered soils during installation of probes using geotechnical centrifuge modelling and cavity expansion analysis. Two series of centrifuge tests were performed in stratum configurations of silica sand in a half-cylindrical axisymmetric model, allowing the observation of the induced soil deformation through a Perspex window. The variations of penetration resistance and soil deformation with penetration depth, soil density, stress level and soil layering are examined from the results of the centrifuge tests. The quantified soil displacements and the resulting strains in the axisymmetric model have provided an effective approach for investigation of penetration mechanisms with soil element trajectories, strain paths and rotations of principal strain rate. The effects of layering on both resistance and soil deformation are shown with dependence of the relative soil properties and profiles. The results presented also serve as a base for applications of cavity expansion solutions, back analyses and further studies. Analytical solutions for cavity expansion in two concentrically arranged regions of soil are developed using a non-associated Mohr-Coulomb yield criterion for large strain analysis of both spherical and cylindrical cavities. The solutions are validated against finite element simulations and a detailed parametric study of the layered effects on the pressure-expansion curves is performed. To apply the proposed solutions to penetration problems, a simplified combination approach is suggested to eliminate the discrepancy between concentric layering and horizontal layering. The analytical study of penetration in two-layered and multi-layered soils is therefore achieved, with comparisons to elastic solutions and numerical simulations provided. The back analyses based on the resistance and soil deformation emphasise the influences of small-strain stiffness, soil-probe interface friction angle, and relative density/state parameter. The correlation between the cone tip resistance and the pile bearing capacity is also discussed, and the scale effects are examined through the ground surface effect and the layering effect by the developed cavity expansion solutions. The penetration mechanisms are summarised from the aspects of soil stress-strain history, particle breakage, soil patterns, and penetration in layered soils. The layered effects emphasised in this research indicate that the penetration resistance is strongly dependent on the soil properties within the influence zones above and below the probe tip, and also related to the in-situ stress gradient along the penetration path. It is also suggested that correlations from calibration chamber tests using uniform soil and a constant stress field may not be suitable for direct interpretation of CPT data. Finally, the averaging technique for pile design is suggested based on the transition curve of tip resistance in layered soils with consideration of the scale effects.
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Schwarzer, Norbert. "Modelling of the contact mechanics of thin films using analytical linear elastic approaches." Doctoral thesis, N. Schwarzer: Arbitrary load distribution on a layered half space, ASME Journal of Tribology, Vol. 122, No. 4, October 2000, 672-681, ISSN 0742-4787; N. Schwarzer, F. Richter, G. Hecht: ”Elastic Field in a Coated Half Space under Hertzian pressure distribution”, J. of Surface & Coatings Technology 114 (1999) 292-304, ISSN 0257-8972; N. Schwarzer, Th. Chudoba, D. Billep, F. Richter: ”Investigation of coating substrate compounds using inclined spherical indentation”, J. of Surface & Coatings Technology 116 – 119 (1999) 244-252, ISSN 0257-8972, 2003. https://monarch.qucosa.de/id/qucosa%3A18161.
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In this work the author presents simulation procedures (mathematical models) with the aim to help determining and analysing the mechanical properties of coating-substrate-systems and finding an optimal coating structure which should protect the compound from inelastic deformation under a given range of load conditions. Such procedures may be used as a tool to minimise the search field for experimental work. For this purpose one would need a mathematical model which allows one to calculate the complete elastic field with all its displacement and stress components within a multilayer film on a substrate under given mechanical loading and intrinsic stress conditions.
Due to copyright restrictions the author is not allowed to publish the Part II of his habilitation thesis at this place. It concerns the references in meta data.In der Arbeit werden mathematische Modelle zur Berechnung der mechanischen Eigenschaften geschichtet aufgebauter Materialien unter unterschiedlichsten Lastbedingungen (Kontakt- und intrinsische Beanspruchung) vorgestellt und diskutiert. Auf Grund von Schutzrechtsbestimmungen ist eine Veröffentlichung der in der Habilitation angegebenen Literatur im Teil II an dieser Stelle nicht möglich. Der interessierte Leser wird gebeten die Arbeiten in den entsprechenden Journalen einzusehen. Dies betrifft die in den Metadaten angegebenen Veröffentlichungen des Autors.
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Schwarzer, Norbert. "Modelling of the contact mechanics of thin films using analytical linear elastic approaches." Doctoral thesis, [S.l. : s.n.], 2004. http://www.bsz-bw.de/cgi-bin/xvms.cgi?SWB11244005.
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March, Nathan. "Analytical, numerical and macroscopic modelling approaches for diffusive transport processes in heterogenous media." Thesis, Queensland University of Technology, 2021. https://eprints.qut.edu.au/208260/1/Nathan_March_Thesis.pdf.
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This project used mathematical modelling to better understand diffusion in composite materials. It resulted in new analytical, numerical and macroscopic modelling techniques that can be applied to a greater variety of problems, are more efficient than existing methods and yield more accurate and efficient simulations of complex diffusion processes.
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Flint, Thomas. "Novel approaches for the modelling of heat flow in advanced welding processes." Thesis, University of Manchester, 2016. https://www.research.manchester.ac.uk/portal/en/theses/novel-approaches-for-the-modelling-of-heat-flow-in-advanced-welding-processes(fd47e4ea-95b2-447a-a9ad-79bf2c809978).html.
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The transient temperature fields induced by welding processes largely determine the size of the fusion and heat-affected zones, the microstructures, residual stresses and distortion both in the vicinity of the weld and in the final component as a whole. An accurate prediction of these fields relies heavily on the representation of the welding heat source, both in space and in time. The double-ellipsoidal heat source model proposed by Goldak and co-workers has been widely used to simulate the heat transferred from an electric arc to a component and to compute the induced transient temperature fields. This double-ellipsoidal distribution has worked well for many welding applications, but it is less appropriate when representing the heat transfer at the base of a groove whose width is narrow in relation to its depth. Similarly the conical heat source models used to represent the electron beam welding process, when applied in keyhole mode, are less appropriate when the keyhole terminates within the component, such as in the case of a partial penetration weld. In this work, the double-ellipsoidal heat source model is extended, and alternatives presented, to account for a wider set of welding scenarios, including narrow weld groove geometries and keyhole welding scenarios. A series of mathematically robust novel heat source models is presented and the models are validated against experimental data obtained during the application of various welding processes to an important grade of pressure vessel steel, namely SA508 Grade 3 class 1 steel. The calculation of the transient temperature fields during welding is extremely computationally expensive using numerical methods. Where available, and appropriate, analytical solutions are presented for these novel welding heat source models, coupled with analytical methods for accounting for time dependent heat input rates, to not only reduce computational cost but also to achieve precise predictions of the temperature fields. This, in turn, has the potential to contribute to improvements in safety assessments on critical welded infrastructure through improved predictions for the evolution of microstructure, mechanical properties and the levels of residual stress and distortion in welded joints.
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Schwarzer, Norbert, and Peggy Heuer-Schwarzer. "Qualitative failure analysis on laminate structures of windsurfing boards using analytical linear elastic modelling." Universitätsbibliothek Chemnitz, 2006. http://nbn-resolving.de/urn:nbn:de:swb:ch1-200600107.
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Recently developed mathematical tools for the modelling of contact problems on thin film structures are adapted to allow the investigation of arbitrarily mixed purely isotropic and transversally isotropic laminate structures. The new tool is applied to model a variety of load problems resulting in the failure of windsurfing boards consisting of a relatively thin laminate shell and a soft polymer foam core. It is shown that local impact and distributed bending loads due to “bad landing” after high jumps or contact with parts of the sailing gear (the so called rig) especially the front part of the boom are leading to the most critical stress distributions resulting in failure. So most of the investigated boards were damaged because the rider (windsurfer) landed flat and thus produced a sudden impact force under his feet (impact defect). Other overloading occurred due to overturning of so called loop movements or the landing of the board exactly on respectively between two waves and this way producing high bending moments. Some of those typical loads are analysed in detail and the stresses occurring in the complex structure of the windsurfing boards are evaluated.
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Mallett, Michael John Disney. "An analytical and computer modelling study of atomic motion in fluids constrained by barriers." Thesis, University of Kent, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358039.
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