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Qin, Jianjun. "Dynamic behaviour of flexible marine risers." Thesis, Heriot-Watt University, 1987. http://hdl.handle.net/10399/990.
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Williams, Jonathan Mark. "Mechanical behaviour of flexible polyurethane foams." Thesis, University of Leicester, 1995. http://hdl.handle.net/2381/34725.
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Dunlop Suspensions and Components manufacture microvon, a flexible polyurethane foam, which is used extensively in the automotive industry as spring aids for car suspension systems. The material is used because of its desirable non-linear elastic stress/stain characteristics, its quick recovery behaviour, and because it tends to produce little lateral expansion during compression. The design of such spring aid components, however, remains something of a black art, since the behaviour of the material is not fully understood. Complications arise because the mechanical properties of the material are controlled by a large number of physical, chemical and processing effects. The aim of the research has been to gain further understanding of the material, and its response under load, in order to be able to predict the compressive behaviour of the material. This has been achieved by combining microstructural observations of the deforming material with information obtained from detailed mechanical tests. There have been many attempts by researchers to describe the behaviour of cellular materials. This has been done in a variety of ways, and approaches have included developing complicated strain energy functions or utilising simple models based on repeating cell units. However, a number of difficulties are encountered when applying these material models to microvon. The microstructural observations and mechanical tests undertaken in this research have led to the development of new material models for cellular materials. Two types of model have been developed; a physical model and a series of phenomenological models. The physical model is a bi-linear relationship between stress, strain and density, in which the mechanisms of deformation are described. The phenomenological models have been developed using curve- fitting, to accurately predict the axial stress/strain and lateral/axial strain behaviour of microvon over a wide range of strain, density, temperature and strain rate.
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Andrews, David University of Ballarat. "Program behaviour modelling with flexible logical entity abstraction." University of Ballarat, 2006. http://archimedes.ballarat.edu.au:8080/vital/access/HandleResolver/1959.17/12730.
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"This study extends the use of abstration in program behaviour modelling, and provides a flexible abstraction technique that allows modelling in terms of the logical abstract concepts with which a program operates. This technique is called a Logical Entity Abstracted Program Behaviour Modelling (LEAPBM)."--leaf [ii]<br>Doctor of Philosophy
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Andrews, David. "Program behaviour modelling with flexible logical entity abstraction." University of Ballarat, 2006. http://archimedes.ballarat.edu.au:8080/vital/access/HandleResolver/1959.17/14617.
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"This study extends the use of abstration in program behaviour modelling, and provides a flexible abstraction technique that allows modelling in terms of the logical abstract concepts with which a program operates. This technique is called a Logical Entity Abstracted Program Behaviour Modelling (LEAPBM)."--leaf [ii]<br>Doctor of Philosophy
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Bourke, John David. "Behaviour and analysis of a flexible concrete arch." Thesis, Queen's University Belfast, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.600123.
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The development of steel reinforced concrete in the early 20th century led to a decline in masonry arch bridge building. Traditional masonry arch construction is time consuming and involves considerable form work usually in the form of timber centring, as well as traditional skills. As a result, reinforced concrete arches and slab and beam bridges became common. However, durability issues associated with corrosion of steel have become a major and costly problem and design can now favour steel-free structures. The FlexiArch bridge system is a sustainable alternative for short span crossings and contains no steel reinforcement or mortar joints. This thesis presents detailed research into the behaviour and analysis of FlexiArch systems through laboratory models and non-linear finite element analysis. The arches were monitored through lifting, arch ring tests, backfilling, and under full test loading. The variables in the eight arches were the backfill type, arch ring thickness, solid and hollowcore voussoir design, and span to rise ratio. The experimental investigation demonstrated that higher peaks loads were achieved in the arches of higher arch ring thickness; the rings with so lid voussoirs sustained higher loads than rings with hollowcore voussoirs, and doubling the arch span (shallower profile) typically halved the peak load. The importance of accurate material properties for use in numerical prediction was highlighted in the literature and control tests were carried out to determine the material properties. The nonlinear finite element analysis investigated three areas. Firstly, models were constructed to replicate those tested in the laboratory and to further compare key variables. Secondly. a detailed parametric study in material properties demonstrated that many of the parameters had a linear relationship with the arch predicted peak load. Finally the NLFEA model was validated through modelling four arch bridges presented in the literature and predicted accurate behaviour when compared to tests.
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Kamal, Mumtaz Ahmed. "Behaviour of granular materials used in flexible pavements." Thesis, Queen's University Belfast, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.333824.
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Chen, Zhenxin. "The mechanical behaviour and fatigue analysis of flexible pipes." Thesis, Heriot-Watt University, 1990. http://hdl.handle.net/10399/1292.
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Smit, Gerrit. "The behaviour of modern flexible framed structures undergoing differential settlement." Thesis, University of Southampton, 2010. https://eprints.soton.ac.uk/196447/.
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Modern office buildings are often open plan buildings with a frame consisting of flat RC slabs, RC columns and non-load bearing internal and external partitions and facades. These modern framed structures are more flexible than older conventional buildings with load bearing walls and are less susceptible to differential settlement damage. The use of conventional guidelines for differential settlement on modern flexible framed structures may therefore be over-conservative. The literature review of the study highlights the factors producing differential settlement, the types of damage caused by differential settlement and conventional guidelines for limiting differential settlement damage. Conventional guidelines focusing on 2D structures lack provision for the 3D deformation of a structure. To determine the behaviour of a modern flexible framed structure a numerical experiment was performed, which consisted of the design according to British Standards and Eurocodes of a 3D, 5-bay by 5-bay, 6 storey flat slab RC frame with pad foundations on clay. The behaviour of the designed structure undergoing differential settlement was then analysed by means of linear-elastic finite element analyses. The results show firstly that it is possible to normalise structural behaviour to the soilstructure stiffness ratio, secondly the importance of 3D deformation of the structure and thirdly that stiffer load-displacement responses of foundations may also affect the behaviour of the structure. A stiffer load-displacement response may occur with the reuse of foundations
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Manterola, Najera Julen. "Development of advanced methods to characterise the fracture behaviour of flexible bonded joints." Doctoral thesis, Universitat de Girona, 2020. http://hdl.handle.net/10803/672807.
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Advanced joining technologies such as bonded joints play an important role to develop more efficient and durable structures. The present Thesis gives a step forward and proposes different solutions to characterise the fracture behaviour of flexible bonded joints for laboratory and industrial activities. Unlike in laboratory practices, thick and tough adhesives are applied in industrial activities. Moreover, bonded joints have multiple geometries and non-visible cracks may appear, while bonded joints are subjected to service environment. Four different subjects have been addressed to bring both fields closer: the effect of interface dimensions on the fracture behaviour, the effect of sustained loads on durability studies, the development of a new durability test for bonded joints, and the application of acoustic emissions technique for crack growth monitoring. Experimental and numerical works converge in different methods showing a great potential to be used in future projects with an industrial application.<br>Las tecnologías de unión avanzadas como las uniones adhesivas tienen un papel relevante en el desarrollo de estructuras eficientes y duraderas. La presente Tesis propone diferentes soluciones para caracterizar el comportamiento a fractura de uniones adhesivas flexibles para actividades de laboratorio e industriales. A diferencia del laboratorio, los adhesivos que se aplican en la industria son tenaces y de gran espesor. Además, tienen múltiples geometrías, están expuestas a condiciones de servicio y se agrietan tras procesos no visibles. Se han abordado los siguientes temas para acercar la actividad de laboratorio al industrial: el efecto de la geometría de la interfaz en el comportamiento a fractura, el efecto de cargas sostenidas en estudios de durabilidad, el desarrollo de un nuevo ensayo de durabilidad y la aplicación de emisiones acústicas como técnica no destructiva para monitorizar grietas. El trabajo experimental y numérico desarrolla diferentes métodos con potencial para utilizarse en proyectos industriales.<br>Programa de Doctorat en Tecnologia
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Karakerezis, Angelos Panagiotis. "Discrete modelling of flexible objects with viscoelastic behaviour for robotic grasping." Thesis, University of Bristol, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.295653.
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McNulty, Paul. "Behaviour and analysis of a novel skew flexible concrete arch bridge." Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.679480.
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Masonry arch bridge building declined considerably in· the twentieth century due to the development of faster methods of construction, such as reinforced concrete. However, in recent years, the repair and maintenance of bridge structures has become a major concern. The lower maintenance costs and longer 'design life of arch bridges over alternative bridge designs were key reasons in the selection of several arch bridges built towards the end of the twentieth century and the beginning of the twenty first century. The FlexiArch design allows a masonry arch system to be cost competitive with other forms of bridge systems while offering superior durability and lower long term maintenance. The aim of this research was to extend the knowledge of the FlexiArch bridge system into the behaviour of FlexiArch bridge systems with skew and to address the shortfalls found in the literature review. The literature review demonstrated that skew arches are complex 3D structures, and that the assumptions used in current 2D analysis methods to define the effects in the transverse direction often incorrectly predict the behaviour of the skew arch. This research investigated the behaviour of the skew FlexiArch bridge system through a detailed experimental test programme. The experimental test programme involved the design, construction and testing of five third scale skew FlexiArch bridge systems with varying angles of skew. As the skew angle was increased, and the square span and square width were kept constant, the peak load decreased. The skew arch systems transferred the load along the shortest load path; namely the square span direction where possible, or the shortest distance in the highly skewed arch systems. The experimental test data was compared against an analytical model and a 3D NLFEA model, which were found to accurately predict the behaviour of the skew arch.
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Don, Rasika Perera Solangarachchige. "Investigation of fretting behaviour in pressure armour layers of flexible pipes." Thesis, Sheffield Hallam University, 2007. http://shura.shu.ac.uk/20219/.
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The incidence of fretting damage in the pressure armour wires of flexible pipes used in offshore oil explorations has been investigated. A novel experimental facility which is capable of simulating nub and valley contact conditions of interlocking wire winding with dynamic slip, representative of actual pipe loading, has been developed. The test set-up is equipped with a state of the art data acquisition system and a controller with transducers to measure and control the normal load, slip amplitude and friction force at the contact, in addition to the hoop stress in the wire. Tests were performed with selected loading and the fretted regions were examined using optical microscopy techniques. Results show that the magnitude of contact loading and the slip amplitude have a distinct influence on surface damage. Surface cracks originated from a fretting scar were observed at high contact loads in mixed slip sliding while surface damage predominantly due to wear was observed under gross slip. The position of surface cracks and the wear profile have been related to the contact pressure distribution. The evolution of friction force and surface damage under different slip and normal pressure conditions has been analysed. A fracture mechanics based numerical procedure has been developed to analyse the fretting damage behaviour. A severity parameter is proposed in order to ascertain whether the crack growth is in mode I or mode II cracking. The analysis show the influence of mode II cracking in the early stages of crack growth following which the crack deviates in the mode I direction making mode I the dominant crack propagation mechanism. The crack path determined by the numerical procedure correlates well with the experimental results. A numerical analysis was carried out for the fretting fatigue condition where a cyclic bulk stress superimposes with the friction force. The analysis correlates well with short crack growth behaviour. The analysis confirms that fretting is a significant factor that should be taken into account in design and operation of the pressure armour wires of flexible pipes at high contact pressure if the bulk cyclic load superimposes with the friction force. As predicted by the numerical procedure and further by experimental investigations, the surface cracks initiating on the wire in this condition are self arresting after propagating into a certain depth.
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Donadon, Mauricio Vicente. "The structural behaviour of composite laminates manufactured using resin infusion under flexible tooling." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425334.
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Mirzabaigi, H. "An investigation related to the behaviour of flexible landing mats on granular soils." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.372945.
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Potoczny, Grzegorz A. "Electro-mechanical behaviour of indium tin oxide coated polymer substrates for flexible electronics." Thesis, University of Birmingham, 2012. http://etheses.bham.ac.uk//id/eprint/3475/.
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Highly conductive (3.0 - 5.0 x 10 \(^{-4}\) \( \Omega\) cm) and transparent (80 – 85% ) ITO films were successfully fabricated on glass and polymer substrates (PET, PEN and PC) by pulsed laser deposition at low temperatures (24 – 150 °C). The influence of deposition conditions on the structural and physical properties of ITO-coated glass substrates was studied. The samples were investigated using Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), X-Ray Diffraction (XRD), the fourpoint probe and a spectrophotometer. Sol-gel derived ITO films dip-coated on glass substrates were also studied. The optimum film obtained at a firing temperature of 600 °C had a resistivity of 1.8 x 10 \(^{-2}\) \( \Omega\) cm, and optical transmittance of 80%. The electro-mechanical behaviour of ITO/polymer systems was investigated under uniaxial tension and controlled buckling in tension and compression. The resistance changes were monitored in situ. Cracking and buckling delamination failure modes were observed for all samples investigated at critical strains raging from 2.8 to 3.4%, and from 7.0 to 8.0%, respectively. The results showed that the dominant critical failure mode depends on the applied stress conditions. The ITO/PEN samples showed high flexibility; the samples were buckled in tension down to a 2.6 mm radius of curvature before cracks start to occur.
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Lai, Lawrence Shien Hui. "A Numerical Study of the Behaviour of Flexible Inserts in Laminar Channel Flow." Thesis, Curtin University, 2017. http://hdl.handle.net/20.500.11937/52985.
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The fluid-structure interactions between laminar channel-flow and pressure-loaded compliant-wall can lead to channel collapse and structural vibrations. Two-dimensional numerical simulations of fluid-conveying channels with flexible sections are conducted to investigate the steady-state and transient system behaviours. A non-dimensional scheme is developed to characterise and predict the maximum static wall deflection and the onset of self-excited oscillations. This work has applications in industrial and biomechanical engineering.
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Marzinotto, Alejandro. "Flexible Robot to Object Interactions Through Rigid and Deformable Cages." Doctoral thesis, KTH, Robotik, perception och lärande, RPL, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203994.
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In this thesis we study the problem of robotic interaction with objects from a flexible perspective that complements the rigid force-closure approach. In a flexible interaction the object is not firmly bound to the robot (immobilized), which leads to many interesting scenarios. We focus on the secure kind of flexible interactions, commonly referred to as caging grasps. In this context, the adjective secure implies that the object is not able to escape arbitrarily far away from the robot which is caging it. A cage is a secure flexible interaction because it does not immobilize the object, but restricts its motion to a finite set of possible configurations. We study cages in two novel scenarios for objects with holes: caging through multi-agent cooperation and through dual-arm knotting with a rope. From these two case studies, we were able to analyze the caging problem in a broader perspective leading to the definition of a hierarchical classification of flexible interactions and cages. In parallel to the geometric and physical problem of flexible interactions with objects, we study also the problem of discrete action scheduling through a novel control architecture called Behavior Trees (BTs). In this thesis we propose a formulation that unifies the competing BT philosophies into a single framework. We analyze how the mainstream BT formulations differ from each other, as well as their benefits and limitations. We also compare the plan representation capabilities of BTs with respect to the traditional approach of Controlled Hybrid Dynamical Systems (CHDSs). In this regard, we present bidirectional translation algorithms between such representations as well as the necessary and sufficient conditions for translation convergence. Lastly, we demonstrate our action scheduling BT architecture showcasing the aforementioned caging scenarios, as well as other examples that show how BTs can be interfaced with other high level planners.<br><p>QC 20170322</p>
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Rudman, Chantal. "Investigation into the structural behaviour of portal frames." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/1853.
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Martindale, Hugh Gustav Aelred. "The behaviour of flexible riser tensile armour in the region of an end fitting." Thesis, University College London (University of London), 2006. http://discovery.ucl.ac.uk/1445688/.
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This is a study of axial and transverse slip in helically wound armour wires on flexible pipe under the influence of end restraint. Analysis of steel strip layers in order to find the effect of end restraint prompted the development of a new model to describe their behaviour. This avoids the shortfalls of adapting previous models designed either for similar but different structures or for application away from any end fitting restraint. Previous analytical solutions concerning flexible pipe tensile armour have concentrated on pre-defined paths on the supporting surfaces, these being strained helices or geodesic curves, and have avoided any consideration of end effects. The work presented here is aimed at finding the path adopted by armour wires approaching end fittings, and the resultant stresses and slip. A model is developed which uses small changes in helical angle along the strip to describe tensile armour configuration as a flexible pipe is bent and stretched. The problem is characterized by a strip on a cylinder at a variable angle to its axis which itself has a variable curvature applied to it. A solution is found by minimizing total strain energy to find stress concentrations and slip characteristics. The simplest case of a straight pipe under tension is solved first, followed by a more typical flexible riser configuration involving bending under tension. The results show that under frictionless conditions tensile armour wire slips to reduce tension and that near the end fitting this slip leads to increased bending stresses in some or all of the wires. The model is applied to typical riser designs for the transport of oil and gas to find the location and level of the greatest increases in stress. Their sensitivity to pipe design parameters is also assessed.
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Lee, Sang Hoon. "Study of construction methodology and structural behaviour of fabric-formed form-efficient reinforced concrete beam." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5935.
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The nature of this research is in advancing conventional structures and their methods of construction by exploring new technology. The formwork construction of the modern concrete structure involves the use of rigid materials such as steel and timber. This type of formwork often produces structures of forms with limited flexibility which would also hinder the even distribution of the induced stresses. To construct concrete structures with more organic forms; ones that responds to a more natural flow of the induced stresses, it is thought to be more logical to use flexible mould such as the fabric formwork. In such form-active shape the materials’ utilization can be maximized and the degree of material waste can be reduced. For example, when the form responds to the externally applied loads in the way that the internally incurred stresses at any point of the body closely match the capacity of the material, then the form is material-efficient and said to be in its optimal form. The use of fabric formwork, due to its permeability can also improve the quality of concrete by eliminating any air holes on the surface, and also there are reports showing the increase in concrete’s compression strength due to the reduction in water-cement ratio when cast in a fabric mould. This research concentrates on finding such material-efficient form (thus more sustainable) for reinforced concrete beam of improved material quality, through the development of the more efficient construction system of flexible fabric formwork. For this research 11 different types of beams have been built and tested in total, and their construction methods are illustrated and discussed also (Chapter 7 and Chapter 4 respectively). The designs of the beams are developed through consecutive experiment, analysis, evaluation, and modification process (Chapter 6). For the structural analysis of the beams, the most widely accepted analysis methods are reviewed and adapted (Chapter 8). Based on the evaluations of the analytical results the following variables of the beams are modified through the development of the beam designs: The effect of Compression Steel Mesh in Flange Stress Distribution Around Anchorage; Vertical and Horizontal Web Geometry Varying Depth of Flange Steel Content Also it is a part of the current research’s aim to look at the possible application of the current design methods for the design of the fabric formed beams that are discussed in this research. Thus the experimental results are compared with the results which are calculated from the standard design methods suggested by the British Standard Code of Practice (BS8110) (Chapter 9). Computational finite element (FE) analysis is carried out where more intensive analysis is required (Chapter 10). The results of the FE analysis are also compared with the theoretical and experimental results for the verification purpose. The material efficiency of the beam in its final form is assessed through the embodied energy analysis, which compares the total embodied energy consumed through the construction of the beam with a virtual beam that is designed in accordance with the BS8110 (Chapter 11). The analysis indicates that the total embodied energy of the fabric formed beam is about 20~40% less in comparison with the beam designed in accordance with the BS8110. This thesis has the purpose to illustrate and provide the practical information on the design and the construction process of the fabric formed beams, which can be used as a reference to the future research and construction.
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Barnes, Peter Edward. "An investigation into the corrosion fatigue behaviour of high strength carbon steel tensile armour wires." Thesis, University of Manchester, 2015. https://www.research.manchester.ac.uk/portal/en/theses/an-investigation-into-the-corrosion-fatigue-behaviour-of-high-strength-carbon-steel-tensile-armour-wires(1fdde868-c9b9-424f-a472-5b9c0ae5273e).html.
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The corrosion fatigue behaviour of high strength carbon steel tensile armour wires that are used in flexible risers has been explored. An investigation of the corrosion fatigue failure mechanisms for two different sets of corrosion fatigue tested high strength steel wires has been carried out. The two different tensile armour wires were 12 mm x 4 mm and 12 mm x 7 mm. The wires had been corrosion fatigue tested in up to three different seawater environments, namely aerated, CO2 saturated to 1 bar absolute and 100 mbar absolute H2S-CO2 balance to 1 bar absolute. The corrosion fatigue failure investigation included undertaking statistical analysis of fatigue crack and corrosion pit data to establish the effects of environment, applied stress, R-ratio and microstructure due to degree of cold drawing on the corrosion fatigue behaviour. The 12 mm x 4 mm has fine grain martensite-pearlite structure with anisotropic microstructure in the transverse plane. The 12 mm x 7 mm has larger grain martensite-pearlite structure with equiaxed microstructure in the transverse plane. The corrosion fatigue crack path for the two tensile armour wires exhibits transgranular and intergranular cracking due to variations in R-ratio and microstructure. The analysis identified that a significant amount of localised corrosion pitting was present on the surface of both the 12 mm x 4 mm and 12 mm x 7 mm high strength carbon steel tensile armour wires and that many corrosion fatigue cracks had initiated from these geometric discontinuities. A method was developed in order to apply an optical image correlation technique to a sample immersed in seawater. The research has shown that digital image correlation may be applied for in-situ imaging of a corroding and dynamically deforming surface within a seawater environment. The technique demonstrated the establishment of localised surface strain around the corrosion pits during mechanical loading. The results of the surface strain mapping show that the interaction between multiple corrosion pits is consistent with a significant increase in surface strain when compared to a single surface pit acting alone. The results also show that a small single stress raiser can exhibit a high surface stress concentration when compared to a larger one as the strain is dependent upon the geometry of the pit. The highest strain concentration is at the edge of the pit, parallel to the loading direction. The results show the interaction that multiple pits have with each other, the effect they have on surface strains and how they and other types of stress raiser lead to premature failure of components. Further to this the effects of residual stress on crack nucleation were considered. Fatigue cracks initiate at the surface of the high strength carbon steel tensile armour wire therefore surface measurements were carried out to establish the effects of environment and applied load on the development of residual stress fields. The 12 mm x 4 mm wire shows some correlation between applied stress range and surface residual stress measurements with. For the 12 mm x 4 mm wire corrosion fatigue tested in aerated seawater the surface residual stress becomes increasing compressive with an increase in applied stress. For the 12 mm x 4 mm wire corrosion fatigue tested in CO2 saturated seawater the surface residual stress appears to be independent of applied stress. However for the 12 mm x 7 mm carbon steel tensile armour wire there is no correlation between the applied stress range and the surface residual stress. The differences in surface residual stress may be due to the differences in R-ratio, microstructure and level of cold drawing due to the Bauschinger effect. Surface residual stress measurements have been used to explore the effects of the shakedown process on the high strength carbon steel tensile armour wires prior to corrosion fatigue testing. They show that at a high applied stress range the shakedown process readily develops a compressive residual stress on the surface of the carbon steel wire. This is mostly the case for the low applied stress range; however care should be taken when considering the effects of shakedown on a lower stress range in so far as it may not completely remove the tensile residual stress. Through thickness residual stress measurements show a similar distribution of residual stress fields throughout the high strength carbon steel tensile armour wires independent of the applied stress range and environment.
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Burgess, Matthew. "Measuring and modelling patterns of behaviour in datasets of individual investor trading records using flexible methods." Thesis, University of Warwick, 2017. http://wrap.warwick.ac.uk/101984/.
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Datasets of individual investor trading records have been an important source of empirical evidence in the field of behavioural finance. This thesis contributes to two topics within this empirical literature using a dataset of trading records from a discount brokerage. The first topic is the disposition effect (DE), the tendency for investors to sell winning positions at a faster rate than losing positions. A version of the aggregate DE score introduced by Odean (1998) is analysed, as a time series and at the level of individual stocks. The influence of each stock on the aggregate DE score is calculated, and the characteristics of high and low influence stocks compared. A formal relationship is derived between this DE score and the hazard ratio estimated in a proportional hazards (PH) model. PH models have been used in the literature to measure the effect of covariates on the DE at the investor level. Past approaches have used a marginal model to address the problem of correlation between positions at the investor-level, which involves computing robust standard errors after estimation of the model. A shared frailty model is tested as a more flexible alternative, where unobserved heterogeneity is modelled through the use of latent variables. It provides a significantly improved fit relative to the corresponding marginal model, and adheres more closely to the PH assumption. The second topic is the preference of investors for lottery stocks. These are stocks that are low in price and high in volatility and skewness, a scheme of stock categorisation suggested by Kumar (2009a). The theme of using more flexible models to accommodate investor-level correlation is continued, with a mixed-effects logistic regression being used to study the factors affecting the decision to purchase a lottery stock. This allows the comparison of both time-varying and static factors.
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Bircan, Mehmet. "A Study On The Effect Of Pipe - Soil Relative Stiffness On The Behaviour Of Buried Flexible Pipes." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/2/12611562/index.pdf.
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In this study, the effect of pipe-soil relative stiffness on the behaviour of buried flexible pipes was investigated considering the pipe size, material type, stiffness, pipe-soil and natural soil-backfill interfaces and geometry of the trench using the finite element method. For this purpose, a parametric study was conducted to examine the effect of different variables on the resulting earth loads and deformations imposed on the buried pipes. Various types of trench pipe-soil cases were analysed for a certain natural ground and backfill material by the PLAXIS finite element code which allows simulating non-linear soil behaviour, the stages of construction as well as the pipe-soil interaction aspects of the problem. Loads and deformations obtained by the finite element method were compared with those calculated by the conventional approaches for different pipe-soil stiffness ratios. The finite element results obtained for the deformation of typically flexible Polyethylene pipes were then used to back-calculate the range of modulus of soil reaction, E'<br>, values for various pipe-soil relative stiffness and they were compared with the suggested value proposed by Howard (1977).
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Queiroz, José Aparecido Silva de [UNESP]. "Análise de estruturas flexíveis com aplicação de materiais viscoelásticos." Universidade Estadual Paulista (UNESP), 2008. http://hdl.handle.net/11449/90829.
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queiroz_jas_me_bauru.pdf: 1085643 bytes, checksum: eec6371aa0008c040f50ab54f81f875a (MD5)<br>Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)<br>Os materiais viscoelásticos têm sido muito utilizados para atenuar vibração e ruído em estruturas, devido a sua capacidade inerente de absorver uma porcentagem de energia vibratória dos sistemas mecânicos e de dissipá-la sob a forma de calor. Esse tipo de amortecimento tem sido utilizado em muitas aplicações nas indústrias automotiva e aeroespacial, porém as propriedades dinâmicas das estruturas viscoelásticas não são fáceis de serem determinadas, pois suas respostas dependem de muitos fatores externos, tais como a geometria da estrutura, a freqüência de excitação a qual a estrutura está submetida, entre outros. Neste trabalho foi implementado um aparato experimental composto por um motor de corrente contínua, controlado por Modulação por Largura de Pulso (PWM), ao qual se engastou uma estrutura flexível de aço inox (escalímetro), com e sem revestimento viscoelástico. O objetivo foi analisar tal estrutura quando excitada em movimento livre e forçado. Ao oscilar a estrutura, os extensômetros, devidamente acoplados em sua superfície, faziam a leitura dos dados (deformação) e os enviavam a um instrumento de aquisição de dados analógicos, os quais, após a conversão para digital, foram enviados a um PC para análises necessárias ao experimento. Para avaliar as características das estruturas e estimar as taxas de amortecimento, foram aplicados técnicas de decremento logarítmico nas análises em movimento livre e o método da banda de meia potência nas análises em movimento forçado. Foram utilizados dois modelos de materiais viscoelásticos (fitas VHB da 3M). Os métodos de revestimentos foram: “Configuração de Camada Livre” e “Estrutura Sanduíche”. Este último permitiu aumentar as deformações cisalhantes na camada viscoelástica e, conseqüentemente, aumentou a dissipação de energia vibratória. Essas análises permitiram...<br>The viscoelastic materials have been widely used to reduce noise and vibration on structures, because of its inherent ability to absorb a percentage of vibrating energy in mechanical systems and dissipate it as heat. This type of damping has been used in many applications in the automotive and aerospacial industries, but the dynamic properties of viscoelastic structures are not easy to be determined, because their answers depend on many external factors, such as the geometry of the structure, the frequency of excitation that the structure is exposed, among others. In this work a prototype composed of a DC engine, controlled by the Pulse Width Modulator by (PWM), which is setting up a flexible stainless steel (scale ruler), with and without coating viscoelastic has been implemented. The objective was analyze the structure when excited in free and forced movement. When the structure swings, the strain Gages properly attached to its surface, made the reading of data (deformation), and sent it to an analog data acquisition instrument, which after that converts analogical data to digital and they were sent to a PC for experiment analysis. To evaluate the structure characteristics, and estimate the damping rates were applied techniques of analysis in logarithmic decrement in free movement, and the method of half-band power in the forced movement analysis. We used two models of viscoelastic materials (tapes of 3M HBV). The methods of coating were: Setting Free Layer and structure Sandwich. The last one enabled the increase the cut deformations in viscoelastic layer and consequently increased the dissipation of vibrating energy. These tests have allowed a better understanding of the influence of viscoelastic material in the vibration behavior of these structures.
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Steenkamer, Nikki Lee. "The intentions of working fathers to use flexible workplace arrangements : an application of the theory of planned behaviour." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/13794.
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This study utilised the theory of planned behaviour (TPB) to investigate the intentions of South African working fathers to use flexible workplace arrangements (FWAs). The study aimed to broaden the limited knowledge of the experiences of working fathers in a South African context. Usable responses to an electronic questionnaire were received from white collar male employees across a variety of industries (N = 371). Exploratory Factor Analyses and reliability analyses showed strong support for the use of TPB scales in future behavioural research. Hierarchical binary logistic regression analyses showed that attitudes, subjective norms and perceived behavioural control help to predict working fathers intentions to use FWAs. Attitudes was the strongest predictor and subjective norms was the weakest. It was also found that intentions do not significantly predict actual behaviour for most of the FWAs assessed, however actual behavioural control helps predict actual use of FWAs. Support was found for using perceived behavioural control as a proxy measure for actual behavioural control. Theoretical and management implications of the present findings are discussed.
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Bähr, Sebastian [Verfasser]. "Regional mobility of unemployed workers : Experimental evidence on decision-making and behaviour in flexible labour markets / Sebastian Bähr." Bielefeld : W. Bertelsmann Verlag, 2017. http://d-nb.info/1147813256/34.
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Bowman, April Joy. "Performance of silty sands and their use in flexible airfield pavement design." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/287462.
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Traditionally, flexible pavement design relies on past experience and semi-empirical methods developed through a combination of element testing and modelling. Element testing in this area especially, has centred on the performance of clean sands. This is in conflict with actual practice where a wide range of fines and soil gradations could be present in a real-world project. This research investigates the characteristics of natural sands and examines the influence of these marginal materials in pavement design using element testing and controlled modelling of an actual flexible pavement system. The element tests concentrated on separate, natural soils sourced from Kazakhstan which had similar mineralogy, but varying amounts of fines. One of the key parameters examined was equivalent void ratio and its efficiency to account for the behaviour change in granular materials which comes from increased fines content. Starting with monotonic triaxial results combined with strength-dilatancy methods it was shown that prediction of shear strength in a silty-sand could be improved by 13%. Incorporating this finding into repeat load triaxial tests, the transitions between elastic, plastic, and ratcheting failure behaviours (i.e. shakedown boundaries), commonly used to help predict the lifespan of a flexible pavement, were examined. It was seen that cycling a silty-sand, the stress path and yield surface could change depending on the fines content. The Cambridge Airfield Pavement Tester (APT) was designed and constructed to measure permanent subgrade deformation resulting from various surface loads. The number of input variables required to design flexible pavements is one of the most frequently stated problems in the field; variation of aircraft types, environmental conditions, and materials makes mechanistic design of the soil foundation problematic. Accordingly physical pavement modelling continues to be the only experimental method that allows input parameters and material characteristics to be examined simultaneously. Digital image correlation (DIC) was incorporated into the system; the first time this technology has been used in flexible pavement research. A Null Pressure System was also installed to measure soil stress distributions. It was observed that the critical failure mechanisms for thin and thick surficial layers are different, resulting in changes in the rates of surface rutting. Finally, by combining element and APT results, knowledge of the causal relationships between subsurface deformation and failure mechanisms in flexible pavement were advanced. In-situ soils, which are frequently incorporated into subgrade designs, were found to have a substantial role in the serviceability of the pavement. Correlations between element tests and APT results highlighted the complicated loading and boundary conditions present in a pavement.
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de, Zylva Geoffrey Anthony. "Does behavioural plasticity contribute to differences in population genetic structure in wild rabbit populations in arid and semi-arid Australia?" Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16437/1/Geoffrey_de_Zylva_Thesis.pdf.
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The European rabbit, Oryctolagus cuniculus, was introduced to Australia in 1859 and quickly became a significant vertebrate pest species in the country across a wide distribution. In arid and semi-arid environments, rabbit populations exist as metapopulations - undergoing frequent extinction recolonisation cycles. Previous studies identified population genetic structuring at the regional level between arid and semi-arid environments, and habitat heterogeneity was suggested as a possible causal factor. For the most part, rabbit behaviour has been overlooked as a factor that could contribute to explaining population genetic structure in arid and semi-arid environments.
This study utilised a combination of genetic sampling techniques and a simulated territorial intrusion approach to observing wild rabbit behaviour in arid and semi-arid environments. The genetic component of the study compared population samples from each region using four polymorphic microsatellite loci. The behavioural component examined variation in the level of territoriality exhibited by three study populations in the arid region towards rabbits of known versus unknown origins (resident vs transgressor (simulating dispersal)).
A difference was observed in population genetic structure determined from nuclear markers between arid and semi-arid regions, which supports findings of previous research using mitochondrial DNA data in the same area. Additionally, differences in aggressive response to known vs unknown rabbits were identified in parts of the arid region, which together with the effects of habitat heterogeneity and connectivity may explain the observed differences in population genetic structure.
Knowledge of behavioural plasticity and its effect on relative dispersal success and population genetic structure may contribute to improved management and control of feral rabbit populations at the regional level within Australia; and may assist with conservation efforts in the species' natural range in Europe.
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de, Zylva Geoffrey Anthony. "Does behavioural plasticity contribute to differences in population genetic structure in wild rabbit populations in arid and semi-arid Australia?" Queensland University of Technology, 2007. http://eprints.qut.edu.au/16437/.
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The European rabbit, Oryctolagus cuniculus, was introduced to Australia in 1859 and quickly became a significant vertebrate pest species in the country across a wide distribution. In arid and semi-arid environments, rabbit populations exist as metapopulations - undergoing frequent extinction recolonisation cycles. Previous studies identified population genetic structuring at the regional level between arid and semi-arid environments, and habitat heterogeneity was suggested as a possible causal factor. For the most part, rabbit behaviour has been overlooked as a factor that could contribute to explaining population genetic structure in arid and semi-arid environments. This study utilised a combination of genetic sampling techniques and a simulated territorial intrusion approach to observing wild rabbit behaviour in arid and semi-arid environments. The genetic component of the study compared population samples from each region using four polymorphic microsatellite loci. The behavioural component examined variation in the level of territoriality exhibited by three study populations in the arid region towards rabbits of known versus unknown origins (resident vs transgressor (simulating dispersal)). A difference was observed in population genetic structure determined from nuclear markers between arid and semi-arid regions, which supports findings of previous research using mitochondrial DNA data in the same area. Additionally, differences in aggressive response to known vs unknown rabbits were identified in parts of the arid region, which together with the effects of habitat heterogeneity and connectivity may explain the observed differences in population genetic structure. Knowledge of behavioural plasticity and its effect on relative dispersal success and population genetic structure may contribute to improved management and control of feral rabbit populations at the regional level within Australia; and may assist with conservation efforts in the species' natural range in Europe.
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Queiroz, José Aparecido Silva de 1975. "Análise de estruturas flexíveis com aplicação de materiais viscoelásticos /." Bauru : [s.n.], 2008. http://hdl.handle.net/11449/90829.
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Orientador: Edson Antônio Capello Sousa<br>Banca: Mauro Hugo Mathias<br>Banca: Paulo Roberto de Aguiar<br>Resumo: Os materiais viscoelásticos têm sido muito utilizados para atenuar vibração e ruído em estruturas, devido a sua capacidade inerente de absorver uma porcentagem de energia vibratória dos sistemas mecânicos e de dissipá-la sob a forma de calor. Esse tipo de amortecimento tem sido utilizado em muitas aplicações nas indústrias automotiva e aeroespacial, porém as propriedades dinâmicas das estruturas viscoelásticas não são fáceis de serem determinadas, pois suas respostas dependem de muitos fatores externos, tais como a geometria da estrutura, a freqüência de excitação a qual a estrutura está submetida, entre outros. Neste trabalho foi implementado um aparato experimental composto por um motor de corrente contínua, controlado por Modulação por Largura de Pulso (PWM), ao qual se engastou uma estrutura flexível de aço inox (escalímetro), com e sem revestimento viscoelástico. O objetivo foi analisar tal estrutura quando excitada em movimento livre e forçado. Ao oscilar a estrutura, os extensômetros, devidamente acoplados em sua superfície, faziam a leitura dos dados (deformação) e os enviavam a um instrumento de aquisição de dados analógicos, os quais, após a conversão para digital, foram enviados a um PC para análises necessárias ao experimento. Para avaliar as características das estruturas e estimar as taxas de amortecimento, foram aplicados técnicas de decremento logarítmico nas análises em movimento livre e o método da banda de meia potência nas análises em movimento forçado. Foram utilizados dois modelos de materiais viscoelásticos (fitas VHB da 3M). Os métodos de revestimentos foram: "Configuração de Camada Livre" e "Estrutura Sanduíche". Este último permitiu aumentar as deformações cisalhantes na camada viscoelástica e, conseqüentemente, aumentou a dissipação de energia vibratória. Essas análises permitiram... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: The viscoelastic materials have been widely used to reduce noise and vibration on structures, because of its inherent ability to absorb a percentage of vibrating energy in mechanical systems and dissipate it as heat. This type of damping has been used in many applications in the automotive and aerospacial industries, but the dynamic properties of viscoelastic structures are not easy to be determined, because their answers depend on many external factors, such as the geometry of the structure, the frequency of excitation that the structure is exposed, among others. In this work a prototype composed of a DC engine, controlled by the Pulse Width Modulator by (PWM), which is setting up a flexible stainless steel (scale ruler), with and without coating viscoelastic has been implemented. The objective was analyze the structure when excited in free and forced movement. When the structure swings, the strain Gages properly attached to its surface, made the reading of data (deformation), and sent it to an analog data acquisition instrument, which after that converts analogical data to digital and they were sent to a PC for experiment analysis. To evaluate the structure characteristics, and estimate the damping rates were applied techniques of analysis in logarithmic decrement in free movement, and the method of half-band power in the forced movement analysis. We used two models of viscoelastic materials (tapes of 3M HBV). The methods of coating were: "Setting Free Layer" and " structure Sandwich." The last one enabled the increase the cut deformations in viscoelastic layer and consequently increased the dissipation of vibrating energy. These tests have allowed a better understanding of the influence of viscoelastic material in the vibration behavior of these structures.<br>Mestre
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Wrzesien, Andrzej M. "Effect of stressed skin action on the behaviour of cold-formed steel portal frames with non-linear flexible joints and top-hat purlins." Thesis, University of Strathclyde, 2016. http://digitool.lib.strath.ac.uk:80/R/?func=dbin-jump-full&object_id=27491.
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Tsioki, Anita, and Karolina Borg. "Engaging, Inhibitive or an Organizational Chaos? : A Phenomenological Study on Employees’ Perception of the Activity-based Flexible Office." Thesis, Södertörns högskola, Institutionen för samhällsvetenskaper, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-39397.
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This study discusses employees’ perception of a rather new and progressive office type, namely the Activity-based Flexible Office, the A-FO. Within this office type, the employee does not have a personal desk, but instead changes workspace depending on the task at hand. The aim of the study was to examine how employees perceive this type of office and their experiences of working within it. In previous research, a model has been created within this field as an attempt towards a theoretical framework, the A-FO-M. Whereas studying this model, we saw some notions not being thoroughly explored, although mentioned in other preceding research. Thus, the need of exploring these aspects further felt vital and therefore, we combined the A-FO-M with other preceding research and created a synthesis with a set off our themes. A qualitative method was chosen and furthermore, a phenomenological approach. This approach suggests examining a certain phenomena, the A-FO in this case, based on the experiences and perceptions of an individual, the employee. Interviews were implemented on a specific company to succeed in reaching our aim. The six interviews completed gave us the empirical results we needed to attain an analysis and thereafter, conclusions. Overall, our findings correspond with the presumptions of the A-FO-M. However, due to Klarna having a certain structure, somewhat differing from the traditional A-FO, the results were contradicting in some cases. The majority of the respondents felt they were able to perform their task without major problems. Some respondents felt that the office made them more open, while others did not feel any impact on their persona in relation to the A-FOs features. Our findings support that the A-FO is a very sociable office type, whereas you constantly meet and interact with people, both known and unknown to you. The respondents appreciate that there is little distance between them and their managers. Additionally, it is found that managers within A-FOs need to have high trust in their employees. Conclusively, some results may be somewhat dependent on the individual and their preferences.
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Enoksson, Louise, and Elin Larsson. "The Role of A Flexible Brand Identity in A Dynamic Market : A Multiple-Case Study on Swedish Coffee Brands." Thesis, Karlstads universitet, Handelshögskolan (from 2013), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-82639.
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Conducting successful business requires a clear and steady brand identity, which is a part of brand management (Aaker, 1996; Kapferer, 1992, de Chernatony, 1999). Sticking to the core values and the traditions of the brand is beneficial. However, it seems advantageous to possess a flexible brand identity for the brand to be able to adapt to market trends and development. This could be of even more importance if the brand is existing in a dynamic market (Eisenhardt & Martin, 2000). This study aims to understand and further describe the role of flexible brand identity in a dynamic market, from a corporate point of view. The study was made according to an inductive approach of qualitative research, which enabled data collection from two case companies. The Swedish coffee market was chosen as the case market. Hence, five in-depth interviews were conducted with people working for two established coffee brands in Sweden. The empirical findings showed the importance of working on the brand identity to stay relevant in the Swedish coffee market. Factors and stakeholders such as consumers, retail, shops, origin of the coffee, changes in consumer interests, and market trends were mentioned. Communication, and brand transformation, also appeared to be important factors within the study. The empirical findings have been analysed in comparison to the previous research on brand identity and dynamic markets, as well as further developed and discussed. Altogether, the study aimed to discuss concepts and the empirical findings, and by the inclusion of the research questions: 1) How do companies work on transforming their brand identity? 2) How can a flexible brand identity be favourable when existing in a dynamic market? In conclusion, the Swedish coffee market appears to be moderately dynamic, and the benefits of a flexible brand identity is the ability to adapt and adjust for market trends, as long as the core values are taken into account during the changes.<br>Att driva framgångsrik business innebär ett behov av en tydlig och stabil varumärkesidentitet, vilken är en del inom varumärkeshanteringen (Aaker, 1996; Kapferer, 1992, de Chernatony, 1999). Det är föredömligt att hålla sig till varumärkets grundvärderingar och traditioner, men kan även vara fördelaktigt att bedriva en mer flexibel varumärkesidentitet för att kunna anpassa den till marknadstrender- och utveckling. Det kan vara om än mer viktigt om varumärket verkar på en dynamisk marknad (da Silveira, 2013; Eisenhardt & Martin, 2000). Den här studien syftar till att förstå och vidare beskriva innebörden av en flexibel varumärkesidentitet på en dynamisk marknad, och detta utifrån ett företagsperspektiv. Den kvalitativa studien utfördes genom en induktiv ansats, med datainsamling från två olika företag på den svenska kaffemarknaden. Sammanlagt har fem anställda inom två svenska kaffevarumärken har intervjuats. Den empiriska datan visade på att det är viktigt att jobba med varumärkesidentiteten för att vara relevant på den svenska kaffemarknaden. Faktorer och intressenter, såsom konsumenter, dagligvaruhandeln, kaffebutiker och kaffets ursprung, nämndes upprepat. Trender och svängande kaffeintresse samt kommunikation och varumärkestransformation var också centrala aspekter. Den empiriska datan har analyserats och jämförts med tidigare forskning men har också utvecklats och vidare diskuterats. Sammantaget syftar studien till att diskutera koncepten och den empiriska datan och syftet har brutits ned i två forskningsfrågor: 1) Hur kan företag arbeta med att transformera sin varumärkesidentitet? 2) Hur kan en flexibel varumärkesidentitet vara fördelaktig på en dynamisk marknad? Utifrån analysen drogs slutsatsen att den svenska kaffemarknaden är “moderately dynamic” och fördelarna med en flexibel varumärkesidentitet är att den kan anpassas efter marknaden och dess trender, så länge grundvärderingarna tas i beaktning genom förändringarna.
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Nugent, Rebecca. "Physical Activity, Sedentary Behaviour, and Musculoskeletal Pain and/or Discomfort in Teleworking Office Workers : A quantitative cross-sectional study performed in Sweden." Thesis, Mittuniversitetet, Institutionen för hälsovetenskap, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:miun:diva-42464.
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Background: Telework has become a frequent form of work for a large part of the workforce. However, research regarding public health aspects is lacking in this area. The purpose of this study was to examine how physical active teleworkers are and if they achieve WHO guidelines. A second aim of the study was to investigate relationships between telework and physical activity, sedentary behaviour, and musculoskeletal pain/discomfort. Method: A cross-sectional survey was performed in Sweden. In total 375 individuals were included in the sample. Logistic regressions were performed to determine association between telework and physical activity, sedentary behaviour, and musculoskeletal pain/discomfort (current and during the last 12 months). Results: 83 % of teleworkers reported physical activity levels that met the WHO guidelines. The results showed no significant relationships between telework and physical activity, sedentary behaviour, or musculoskeletal pain/discomfort. Conclusion: A large part of the studied sample of teleworkers reported achieving the WHO recommendation for physical activity. As no associations could be found between telework, and physical activity, sedentary behaviour, and musculoskeletal issues, telework could be deemed to be as safe as any other work form. However, as this was not a prospective study, with a random sample, further studies are required to investigate whether teleworking has an impact on public health.<br><p>Betyg i Ladok 210603.</p>
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Ghasemi, Negareh. "Improving ultrasound excitation systems using a flexible power supply with adjustable voltage and frequency to drive piezoelectric transducers." Thesis, Queensland University of Technology, 2012. https://eprints.qut.edu.au/61091/1/Negareh_Ghasemi_Thesis.pdf.
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The ability of a piezoelectric transducer in energy conversion is rapidly expanding in several applications. Some of the industrial applications for which a high power ultrasound transducer can be used are surface cleaning, water treatment, plastic welding and food sterilization. Also, a high power ultrasound transducer plays a great role in biomedical applications such as diagnostic and therapeutic applications. An ultrasound transducer is usually applied to convert electrical energy to mechanical energy and vice versa. In some high power ultrasound system, ultrasound transducers are applied as a transmitter, as a receiver or both. As a transmitter, it converts electrical energy to mechanical energy while a receiver converts mechanical energy to electrical energy as a sensor for control system. Once a piezoelectric transducer is excited by electrical signal, piezoelectric material starts to vibrate and generates ultrasound waves. A portion of the ultrasound waves which passes through the medium will be sensed by the receiver and converted to electrical energy. To drive an ultrasound transducer, an excitation signal should be properly designed otherwise undesired signal (low quality) can deteriorate the performance of the transducer (energy conversion) and increase power consumption in the system. For instance, some portion of generated power may be delivered in unwanted frequency which is not acceptable for some applications especially for biomedical applications.
To achieve better performance of the transducer, along with the quality of the excitation signal, the characteristics of the high power ultrasound transducer should be taken into consideration as well. In this regard, several simulation and experimental tests are carried out in this research to model high power ultrasound transducers and systems. During these experiments, high power ultrasound transducers are excited by several excitation signals with different amplitudes and frequencies, using a network analyser, a signal generator, a high power amplifier and a multilevel converter. Also, to analyse the behaviour of the ultrasound system, the voltage ratio of the system is measured in different tests. The voltage across transmitter is measured as an input voltage then divided by the output voltage which is measured across receiver. The results of the transducer characteristics and the ultrasound system behaviour are discussed in chapter 4 and 5 of this thesis.
Each piezoelectric transducer has several resonance frequencies in which its impedance has lower magnitude as compared to non-resonance frequencies. Among these resonance frequencies, just at one of those frequencies, the magnitude of the impedance is minimum. This resonance frequency is known as the main resonance frequency of the transducer. To attain higher efficiency and deliver more power to the ultrasound system, the transducer is usually excited at the main resonance frequency. Therefore, it is important to find out this frequency and other resonance frequencies. Hereof, a frequency detection method is proposed in this research which is discussed in chapter 2.
An extended electrical model of the ultrasound transducer with multiple resonance frequencies consists of several RLC legs in parallel with a capacitor. Each RLC leg represents one of the resonance frequencies of the ultrasound transducer. At resonance frequency the inductor reactance and capacitor reactance cancel out each other and the resistor of this leg represents power conversion of the system at that frequency. This concept is shown in simulation and test results presented in chapter 4.
To excite a high power ultrasound transducer, a high power signal is required. Multilevel converters are usually applied to generate a high power signal but the drawback of this signal is low quality in comparison with a sinusoidal signal. In some applications like ultrasound, it is extensively important to generate a high quality signal. Several control and modulation techniques are introduced in different papers to control the output voltage of the multilevel converters. One of those techniques is harmonic elimination technique. In this technique, switching angles are chosen in such way to reduce harmonic contents in the output side. It is undeniable that increasing the number of the switching angles results in more harmonic reduction. But to have more switching angles, more output voltage levels are required which increase the number of components and cost of the converter. To improve the quality of the output voltage signal with no more components, a new harmonic elimination technique is proposed in this research. Based on this new technique, more variables (DC voltage levels and switching angles) are chosen to eliminate more low order harmonics compared to conventional harmonic elimination techniques. In conventional harmonic elimination method, DC voltage levels are same and only switching angles are calculated to eliminate harmonics. Therefore, the number of eliminated harmonic is limited by the number of switching cycles. In the proposed modulation technique, the switching angles and the DC voltage levels are calculated off-line to eliminate more harmonics. Therefore, the DC voltage levels are not equal and should be regulated. To achieve this aim, a DC/DC converter is applied to adjust the DC link voltages with several capacitors. The effect of the new harmonic elimination technique on the output quality of several single phase multilevel converters is explained in chapter 3 and 6 of this thesis.
According to the electrical model of high power ultrasound transducer, this device can be modelled as parallel combinations of RLC legs with a main capacitor. The impedance diagram of the transducer in frequency domain shows it has capacitive characteristics in almost all frequencies. Therefore, using a voltage source converter to drive a high power ultrasound transducer can create significant leakage current through the transducer. It happens due to significant voltage stress (dv/dt) across the transducer. To remedy this problem, LC filters are applied in some applications. For some applications such as ultrasound, using a LC filter can deteriorate the performance of the transducer by changing its characteristics and displacing the resonance frequency of the transducer. For such a case a current source converter could be a suitable choice to overcome this problem. In this regard, a current source converter is implemented and applied to excite the high power ultrasound transducer. To control the output current and voltage, a hysteresis control and unipolar modulation are used respectively. The results of this test are explained in chapter 7.
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Gharabaghi, Bahram. "Hydraulic behavior of flexible channel lining systems." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0003/NQ40371.pdf.
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Ybañez, y. Valeros Numer. "The crack bridging behavior of flexible fibers." Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11817.
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Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995.<br>Includes bibliographical references (leaves 162-165).<br>by Numer Ybañez y Valeros.<br>M.S.
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Cameron, Jessica Schwartz. "Flexible ethics : loss frames and unethical behavior /." May be available electronically:, 2009. http://proquest.umi.com/login?COPT=REJTPTU1MTUmSU5UPTAmVkVSPTI=&clientId=12498.
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Moreland, John C. "Viscoelastic behavior of water-blown flexible polyurethane foams." Diss., This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-08062007-094406/.
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Tutumluer, Erol. "Predicting behavior of flexible pavements with granular bases." Diss., Georgia Institute of Technology, 1995. http://hdl.handle.net/1853/19254.
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Appea, Alexander Kwasi. "In-Situ Behavior of Geosynthetically Stabilized Flexible Pavement." Thesis, Virginia Tech, 1997. http://hdl.handle.net/10919/9570.
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The purpose of a geotextile separator beneath a granular base, or subbase in a flexible pavement system is to prevent the road aggregate and the underlying subgrade from intermixing. It has been hypothesized that in the absence of a geotextile, intermixing between base course aggregate and soft subgrade occurs. Nine heavily instrumented flexible pavement test sections were built in Bedford County Virginia to investigate the benefits of geosynthetic stabilization in flexible pavements. Three groups of different base course thicknesses (100, 150 and 200mm) test sections were constructed with either geotextile or geogrid stabilization or no stabilization. Woven geotextile was used in sections 2, 5 and 8. Geogrids were used in sections 3, 6 and 9, and sections 1, 4 and 7 were controls. Six Falling weight deflectometer (FWD) tests were performed on all the nine sections over 30 months. The nine sections were subjected to at least 5 load drops with wide loading range each time. The measured deflections were analyzed using the MODULUS back-calculation program to determine layer moduli. The measured deflections were used together with elastic, viscoelastic and the MODULUS program to determine the extent of intermixing at base-subgrade interface. The study concluded that a transition layer would develop when a separator is absent, especially in the weak sections (designed to fail in three years). Other measurements such as in-situ stresses, rut depth, and subsurface profiling (using ground penetrating radar) support the conclusion of the development of a transition layer.<br>Master of Science
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Algin, Halil Murat. "The behaviour of flexibly bedded concrete paver pavements." Thesis, University of Newcastle Upon Tyne, 1996. http://hdl.handle.net/10443/904.
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The growth in the international usage of flexibly bedded pavers since World War II has brought about the need fully to understand how pavers bedded in sand function. The design methods are based upon the concept of making pavers and their bedding sand equivalent to conventional pavement construction materials. Experience has shown that pavers do not behave as a collection of individual units but rather interlock so that they behave in a manner close to that of flexible materials. The nature of a pavement surfaced with pavers is therefore depending on the pavers, the joints, and the way in which the two relate as well as the foundation on which the pavers rest. In this Thesis, a way in which pavers distribute stresses resulting from rolling loads has been investigated and an understanding of the interlocking process thereby developed. This Thesis explains the theoretical analysis and demonstrates how it can be used to establish the nature and value of interlock. Chapter 1 concentrates on this process by starting to introduce concrete paver pavements and goes on outlining the principles upon which the remainder of this Thesis is based. The achievement of full interlock in the surface level of a paver pavement is an essential part of any successful paver pavement. It is important to understand the principles and specifications for the materials and construction process in order to satisfy the requirements of paver pavement components. Because of this reason, Chapter 2 outlines the major contents of UK specifications for the materials and construction methods likely to be used for the construction of paver pavements. Chapter 3 is concerned with the existing structural design of concrete paver pavements carrying vehicular traffic ranging from trucks to heavy industrial vehicles and aircrafts. Design criteria for such pavements are established and a range of methods for their analysis and design are reviewed. Chapters 4 and 5 show how the variations of patch loading on the surface of pavers can be calculated. Chapter 6 presents the bedding sand stress calculation method which can be used to determine the patterns of stress within the bedding material and it shows how these patterns develop as a patch loading rolls across pavers. All possible eccentric load patches on the surface and their all vertical compressive stress distributions in bedding sand were calculated for chamfered rectangular pavers (with and without interlock), non-chamfered rectangular and nine proprietory shaped pavers. The nine proprietory shaped pavers analysed in this Thesis are commercially important on a worldwide basis. Chapters 7,8 and 9 explains how the bedding sand stress calculation method can be applied to proprietory shaped pavers. A common proprietory shaped paver has been selected as an example in Chapter 7 to show how all possible vertical compressive stress regimes of proprietory shaped pavers can be calculated for all realistically possible load patches. The remaining proprietory shaped pavers are analysed in Chapter 8. The results of the analyses presented in Chapters 5,7 and 8 are shown in Chapter 9. The results are being used in the development of paver jointing systems and it is now possible to assess more effectively the tolerances required in paver installation. Although paver pavements appear to be very simple structures they are in reality very complicated, possibly one of the most complicated of all civil engineering structures. In order to predict the future performance of paver pavements, a vast number off simplifications must therefore be made. One of the most promising approaches to this is to apply accurate modelled Finite Element Analysis obtaining the data related with systematic behaviour of paver pavements on the surface level from the results of this Thesis.
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Herbert, D. M. "The behaviour of a flexibly mounted cylinder in waves." Thesis, University of Salford, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.234627.
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Khattari, Ziad Yousef. "Behavior of diblock-copolymers and semi-flexible polymers at interfaces." [S.l. : s.n.], 1999. http://deposit.ddb.de/cgi-bin/dokserv?idn=961385057.
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ALBINO, JUAN CARLOS ROMERO. "FUNCTIONALLY GRADED MATERIALS ON THE DYNAMIC BEHAVIOR OF FLEXIBLE RISERS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2011. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=19447@1.
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CONSELHO NACIONAL DE DESENVOLVIMENTO CIENTÍFICO E TECNOLÓGICO<br>Neste trabalho um novo elemento de viga co-rotacionado é apresentado para
a análise não-linear geométrica tridimensional, estática e dinâmica, de linhas
marítimas de Materiais com Gradação Funcional (MGF). Assume-se que o
módulo de elasticidade e a massa específica do material da viga variam ao longo
da espessura da seção transversal tubular de acordo com uma lei de potência. Na
discretização espacial das equações de equilíbrio, a linha marítima é representada
por um elemento de viga de dois nós, com base nas hipóteses do modelo para
vigas de Euler-Bernoulli, em que polinômios cúbicos de Hermite são utilizados na
interpolação dos deslocamentos nodais e a cinemática do movimento é descrita
através de grandezas referidas a um sistema coordenado local co-rotacionado.
Consideram-se não linearidades geométricas envolvendo grandes deslocamentos e
rotações, mas com pequenas deformações. Nas equações de movimento da linha
marítima, são consideradas as seguintes influencias: do peso próprio, do empuxo,
dos carregamentos hidrodinâmicos (devidos às ações de ondas, correntes e forças
de massa adicional), dos deslocamentos prescritos (junto à fixação da
embarcação), da ação de flutuadores e das forças de interação solo-estrutura. A
integração temporal das equações de equilíbrio é realizada utilizando-se o
algoritmo de discretização HHT (Hilbert-Hughes-Taylor) e a solução numérica
obtida com a técnica iterativa de Newton Raphson. A metodologia numérica foi
implementada e diversos exemplos são apresentados e discutidos enfatizando-se
as diferenças de comportamento estrutural entre os modelos de viga com MGF e
com material homogêneo. Resultados referentes a situações práticas da engenharia
offshore são também tratados nos exemplos.<br>This work presents a new co-rotational beam element formulation to model
the geometric three-dimensional static and dynamic nonlinear analysis of risers of
Functionally Graded Materials (FGM). The material modulus of elasticity and
density of the beam are assumed to vary through the pipe cross-section thickness
following a power law function. In the spatial discretization of the riser
equilibrium equations, a two node beam element based on Euler-Bernoulli theory
is considered, with cubic Hermitian interpolation functions used for nodal
displacement interpolations and element kinematics, all referred to a co-rotation
coordinate system attached to the element local frame. In the element model,
geometric non-linear effects are considered, involving large displacements and
rotations but small strains. The motion of the riser results from the following
applied forces: self weight, buoyancy, hydrodynamic (due to maritime waves,
currents and added mass inertia), prescribed displacements (at the floating
platform), action of floaters and seabed-structure interactions. Step-by-step time
integration of the equilibrium equations is performed with HHT (Hilbert-Hughes-
Taylor) algorithm and the numerical solution is obtained using the Newton-
Raphson iterative technique. The methodology has been implemented and various
sample results presented, that highlight the behavior of functionally graded
material beams as compared to homogeneous beams. Applications related to
practical offshore engineering situations are also considered.
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Badre, David. "Controlling memory and resolving interference : prefrontal contributions to flexible behavior." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/32518.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Brain and Cognitive Sciences, 2005.<br>Includes bibliographical references.<br>Flow does the brain meet shifting task demands? The experiments and formal theoretical framework presented in this dissertation characterize the cognitive and neural processes by which flexible performance is enabled during task switching. Chapter 1 reviews major findings and controversies in the task switching literature, highlighting (1) evidence that behavioral switch costs may derive from proactive interference due to the facilitated retrieval of irrelevant competitors from long-term memory and (2) the consistent finding of activation in ventrolateral prefrontal cortex (VLPFC) during task switching. These observations motivate the hypothesis that left VLPFC may resolve proactive interference arising from long-term memory during a task switch. Chapters 2 and 3 describe three fMRI experiments conducted in experimental contexts independent of task switching that directly link left mid-VLPFC (Brodmann's Area 45; inferior frontal gyrus pars triangularis) to a post-retrieval selection process that resolves proactive interference from irrelevant representations retrieved from long-term memory. Chapter 4 introduces a computational model that derives its task switch cost from interference due to performance-dependent changes in its associative structure, and that resolves this interference through a control process that biases retrieved conceptual representations. Critically, a conflict signal, derived from retrieved conceptual representations in the model, is shown to be characteristic of the pattern of response in left mid-VLPFC during an fMRI experiment that manipulates preparation and interference in task switching. Furthermore, this pattern dissociates left mid-VLPFC from other regions active during a task switch.<br>(cont.) These data strongly support the hypothesis that task switch costs derive from proactive interference due to facilitated retrieval of irrelevant representations and left mid-VLPFC serves to overcome this proactive interference. Chapter 5 provides further details of the model, demonstrates its power to explain a number of common task switching phenomena, and explores its relationship with three other prominent formal models of task switching. The experiments and associated theory presented in this thesis provide evidence that instances of flexible behavior, like task switching, may be understood as acts of memory, and are enabled by prefrontal cortex mechanisms that control memory to overcome interference.<br>by David Badre.<br>Ph.D.
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Higginson, Sarah L. "The rhythm of life is a powerful beat : demand response opportunities for time-shifting domestic electricity practices." Thesis, Loughborough University, 2014. https://dspace.lboro.ac.uk/2134/16018.
Full textAbstract:
The 2008 Climate Change Act set legally-binding carbon reduction targets. Demand side management (DSM) includes energy use reduction and peak shaving and offers significant potential to reduce the amount of carbon used by the electricity grid. The demand side management (DSM) schemes that have tried to meet this challenge have been dominated by engineering-based approaches and so favour tools like automation (which aims to make shifting invisible) and pricing (which requires customer response) to shift demand. These approaches tend to focus on the tools for change and take little account of people and energy-use practices. This thesis argues that these approaches are limited and therefore unlikely to produce the level of response that will be needed in future. The thesis therefore investigates the potential for time-shifting domestic energy demand but takes a different angle by trying to understand how people use energy in their daily lives, whether this use can be shifted and some of the implications of shifting it. The centrepiece of the work is an empirical study of eleven households energy-use practices. The interdisciplinary methodology involved in-house observations, interviews, photographs, metered energy data and disruptive interventions. The data was collected in two phases. Initially, a twenty-four hour observation was carried out in each household to find out how energy was implicated in everyday practices. Next, a series of three challenges were carried out, aimed at assessing the implications of disrupting practices by time-shifting food preparation, laundry and work/ leisure. A practice theory approach is used to shift the focus of attention from appliances, tools for change, behaviour or even people, to practices. The central finding of this work is that practices were flexible. This finding is nuanced, in the light of the empirical research, by an extended discussion on the nature of practices; in particular, the relationship between practices and agency and the temporal-spatial locatedness of practices. The findings demonstrate that, in this study at least, expanding the range of demand response options was possible. The research suggests numerous possibilities for extending the potential of practices to shift in time and space, shift the energy used in practices or substitute practices for other non-energy-using practices, though there are no simple technological or behavioural fixes . More profoundly, however, the thesis concludes that infrastructures of provision , such as the electricity grid and the companies that run it, underpin and facilitate energy-use practices irrespective of the time of day and year. In this context technology-led demand response schemes may ultimately contribute to the problem they purport to solve. A more fundamental interrogation of demand and the infrastructures that serve it is therefore necessary and is almost entirely absent from the demand response debate.
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Sprinkle, Therese A. "Beyond a Need-Based Fairness Perspective: Coworkers’ Perceptions of Justice in Flexible Work Arrangements." University of Cincinnati / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1336413179.
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BASTOS, GERSON ALVES. "MECHANICAL BEHAVIOR OF ASPHALT MIXTURES REINFORCED WITH GEOGRID FOR FLEXIBLE PAVEMENTS." PONTIFÍCIA UNIVERSIDADE CATÓLICA DO RIO DE JANEIRO, 2010. http://www.maxwell.vrac.puc-rio.br/Busca_etds.php?strSecao=resultado&nrSeq=16585@1.
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COORDENAÇÃO DE APERFEIÇOAMENTO DO PESSOAL DE ENSINO SUPERIOR<br>O principal objetivo deste trabalho foi avaliar o comportamento mecânico de
misturas asfálticas reforçadas com geogrelhas. Inicialmente foram previstos ensaios a
serem executados em um modelo físico de verdadeira grandeza. Entretanto, devido a um
comprometimento estrutural localizado num dos componentes deste modelo físico
durante a realização dos ensaios, optou-se por interromper a execução destes e então,
elaborar um programa experimental de laboratório, que consistia da extração de amostras
deste modelo físico de verdadeira grandeza e moldagem de corpos de prova por
amassamento através de compactador giratório. Cada conjunto de amostras (extraídas e
moldadas) possuía corpos de prova sem ou com reforço, onde foram estudados dois tipos
de geogrelha (de fibra de vidro e poliéster). Foram realizados os ensaios de Resistência à
Tração por Compressão Diametral, Módulo de Resiliência, Fadiga por compressão
diametral sob carga controlada e Tração em Disco Circular com Fenda. Os resultados dos
ensaios mostraram que a presença do reforço de geogrelha melhorou o comportamento
mecânico das misturas asfálticas, com a tendência de maior resistência à fratura, fato este
evidenciado principalmente pelo ensaio de Tração em Disco Circular com Fenda, onde
tais corpos de prova não atingiram o critério de finalização do ensaio (redução da carga
aplicada a 0,10 kN). Nos ensaios de fadiga constatou-se que a melhor influência das
geogrelhas ocorre para os menores níveis de tensão aplicada, sendo que nesta condição é
permitido um maior período para as geogrelhas se deformarem, condição essencial para
sua atuação como elemento com a função de atrasar a propagação de trincas. Constatouse
uma melhoria significativa nos resultados obtidos com as amostras reforçadas com as
grelhas, tendo as amostras com camada de geogrelha de poliéster apresentado os
melhores resultados.<br>The objective of this study was to evaluate the mechanical behavior of geogrid
reinforced asphalt mixtures. Initially tests were planned to be executed on a physical
model, however, this tests had to be stopped due to structural problems. Samples were
extracted from the physical model and samples were shaped through gyratory
compaction, both for analyze the mechanical laboratory tests. Tensile Resistance
(Brazilian Test), Resilient Modulus, Fatigue (controlled load) and Disk-Shaped Compact
Tension Geometry Tests were carried out in extracted and shaped samples, without
reinforcement and with the reinforcement of two geogrid types (fiberglass and polyester).
The reinforcement improved the mechanical behavior of asphalt mixtures, with the trend
of greater resistance to fracture, and this was evidenced by Disk-Shaped Compact
Tension Geometry Tests, where the final criterion of the test was not reached (reduction
of the applied load of 0.10 kN). The influence of geogrid is better for lower applied stress
levels according with the Fatigue Tests. This condition allows the geogrid to deform for a
long period, witch is essential for the performance as an element for delay crack
propagation. There was a significant improvement in the results obtained with the
reinforced samples, for both geogrids studied, but the polyester geogrid reached better
results when compared to fiberglass geogrid.
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Moreland, John C. "Molecular orientation and relaxation behavior in flexible water- blown polyurethane foams." Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/42850.
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