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1
Fallatah, Gasem M. "Long-term behaviour of aramid fibre." Thesis, University of Newcastle Upon Tyne, 2006. http://hdl.handle.net/10443/958.
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An investigation of the creep rupture of Kevlar@ 29, Twaron@ 1000, and Technora T2000 aramid fibre yams was carried out in the temperature range 25-120T in air and three other environments (Saudi/Iranian crude oil, pure water, and low pH water) at 65T with the objective of characterising the long term failure behaviour of these fibres and determine if they can be used to replace the stress rupture test conducted on RTP for qualification purposes. The standard loglo-loglo ISO 9080 extrapolation procedure, the modified lin-logio ISO 9080 extrapolation procedure and the time temperature superposition method were used to model and interpret the results. When tested in air, the different yams showed similar but not identical regression parameters. The results of the standard logio-logio ISO 9080 and the modified lin-logio methods correlated well. The standard logio-logio form, however, gave slightly higher values for the 20 year mean stress and LPL. Its use is recommended because it is consistent with the model assumed in the regression of RTP. There was no evidence of any 'knee' in the relationships after long periods or at high temperatures. This suggests that there is no change in failure mechanism, and lends confidence to both the long term use of aramid fibre in air and the recommended qualification procedures. RTP regression curve constants and those of tested aramid fibre were similar indicating the validity of aramid fibre stress rupture tests as a replacement for RTP tests. Crude oil immersion produced a small but significant reduction in behaviour. At 650C a suitable crude oil reduction factor applied to the long ten-n LPL would be 0.9. Pure water produces a marked reduction in strength after short periods, at 65C. Finally, water of low pH resulted in a large reduction in performance and considerable scatter with one fibre type. With the other, the effect appeared to be similar to that of pure water. Based on the understanding of the failure mechanism and the creep process in aramid fibres, a creep strain model is proposed for estimating the strain to failure based on the material's properties.
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Katsaros, Konstantinos Ioannou. "The long-term stress-strain behaviour of chalk." Thesis, University of Brighton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.491094.
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Chalk is a weakly bonded calcareous rock primarily composed of skeletons of microscopic planktonic organisms. Its sedimentary highly anisotropic nature is reflected in its significant range of porosity, bonding strength and textural variation. These intrinsic properties trigger a complex short-term engineering response that has been the subject of numerous studies, whilst its long-term response has attracted lesser attention. A long-term laboratory test programme of conventional compression and extension tests was carried out (duration: 8 to 22-months) in a purpose built environmentally controlled facility, with specially designed loading frames and modified triaxial cells. Furthermore, index as well as triaxial and unconfined tests were also conducted in order to establish the short-term mechanical response. The results were compared and complimented with those of similar studies. In addition, Scanning Electron Microscope (SEM) techniques were employed in an effort to investigate the micro-mechanical response. This led to the formulation of a conceptual micromechanical model associated with the short and long-term deformation of chalk. It was concluded that each variety of chalk has a differing short-term failure envelope controlled by factors such as grain bonding, mineralogy and fabric texture. It was also demonstrated that chalk is not an ideal elastic material and its pseudo-elastic response was associated with the onset of creep. Creep strains appeared to trigger an ageing process that produces elevated post-creep strength and stiffness irrespective of the applied stress path. This was associated to an increase in the frictional interlock of the material. The SEM study revealed a pervasive fabric evolution throughout the post creep/aged samples. This suggested a more uniform stress distribution within the longterm tested samples, than that occurring in the short-term tested samples. The only .discernable effect that could be attributed to the applied stress paths during creep testing was related to the magnitude of the creep rates.
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Ryan, David Alexander. "The long term behaviour of the geomagnetic field." Thesis, University of Newcastle upon Tyne, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.519467.
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Yeates, Martin Paul. "Understanding the relationships between short-term feeding behaviour and long-term intake." Thesis, University of Edinburgh, 2003. http://hdl.handle.net/1842/27727.
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The prediction of animal performance under a variety of conditions has long been a goal within animal science. Because animal performance is a function of food intake this has to be predicted if performance is to be effectively modelled. Analysis of short-term feeding behaviour may give insight into the regulation of feed intake allowing better models of intake to be constructed. This thesis examines in detail the short-term feeding behaviour of dairy cows to better understand food intake regulation. Feeding behaviour consists of feeding events separated by non-feeding intervals. Feeding events are generally clustered into meals. Chapter 2 describes a methodology that utilises a combination of Gaussian and Weibull distributions to describe the length of intervals between feeding events. This method estimates a meal criterion, which allowes the clustering of feeding events into meals in a biologically acceptable way. In subsequent chapters short-term feeding behaviour is assessed largely in terms of meals. Changes in the probability of animals starting a meal with time since the last meal is thought to give insight into the mechanisms underlying intake regulation. Starting probabilities are often calculated with data pooled across individuals or day and night. The extent to which pooling affects conclusions was assessed by analysing experimental data from cows. Results were used to parameterise simulation models, where the consequences of data pooling were systematically investigated. This showed that as variability in pooled data increases so did the likelihood of misinterpreting results. When offered a choice of foods, animals are able to select a consistent combination of these foods in the long-term. Analysis of how a consistent diet is achieved may give insights into the mechanisms regulating intake. The hypothesis that consistent long-term diet choice may be a consequence of diet selection within meals was tested using probability theory. This showed that cows did not have more meals with a composition that was similar to the long-term average diet choice than expected by chance. Therefore, no evidence was found to support such short-term regulation of diet choice. Analysis in previous chapters suggested methods for exploring short-term feeding behaviour, which had yet to be attempted. These included calculation of changes in the probability of animals ending a meal with time since the start of the meal, diurnal patterns of diet choice and prandial correlations. The hypothesis that such analyses could give insights into mechanisms controlling feeding behaviour was tested. No evidence of food intake or diet choice regulation in the very short-term was found. The final chapter examined previously published theories of intake regulation. Predictions from these theories were contrasted with the findings presented in this thesis and in the literature. Theories that advocate regulation in the short-term, and other theories, are identified and discussed in light of current findings. The direction of future work, to enable successful prediction of intake, is discussed.
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Laycock, Silas. "Long term behaviour of high mass X ray binaries." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.268630.
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Laver, Richard George. "Long-term behaviour of twin tunnels in London clay." Thesis, University of Cambridge, 2011. https://www.repository.cam.ac.uk/handle/1810/237245.
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The assessment of ageing tunnels requires a deeper understanding of the long-term behaviour of twin tunnels, whilst lack of permeability data limits the accuracy of long-term predictions. This thesis therefore investigates long-term twin-tunnel behaviour through finite-element parametric analyses, and provides additional pereability data through laboratory studies. Permeability tests are performed on fissured London Clay, exploring the effect of isotropic stress cycles on the permeability of fissures. A model explaining the permeability-stress relationship is proposed to explain irrecoverable changes observed in fissure permeability, and is formulated mathematically for numerical implementation. Laboratory investigations are performed on grout from the London Underground tunnels, investigating permeability, porosity, microstructure and composition. A deterioration process is proposed to explain observations, consisting of acid attack and leaching. The deterioration had appeared to transform the grout from impermeable to permeable relative to the soil. The change in grout permeability with time would strongly influence long-term movements. The long-term behaviour of single tunnels is investigated in a finite-element parametric study. A new method is formulated to predict long-term horizontal and vertical surface displacements after excavation of a single tunnel, and incorporates an improved measure of relative soil-lining permeability. The study also predicts significant surface movements during the consolidation period, contradicting the lack of further building damage observed in the field. A further parametric study also investigates the long-term behaviour of twin tunnels. Key interaction mechanisms are identified, leading to the postulation of the long-term interaction behaviour under different tunnelling conditions. Long-term interaction is found to be complex and significant, and should be accounted for in numerical simulations.
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Kürschner, Dierk, and Christoph Jacobi. "Long-term behaviour of E-region nighttime LF reflection heights: long-term trend, solar cycle, and the QBO." Wissenschaftliche Mitteilungen des Leipziger Instituts für Meteorologie ; 30 = Meteorologische Arbeiten aus Leipzig ; 8 (2003), S. 127-135, 2003. https://ul.qucosa.de/id/qucosa%3A15242.
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The nighttime reflection height of low-frequency (LF) radio waves at oblique incidence is measured at Collm Observatory using 1.8 kHz sideband phase comparisons between the sky wave and the ground wave of a commercial 177 kHz LF transmitter. The measurements have
been carried out continuously since September 1982, now allowing the analysis of trends and regular variations of the reflection height. In the time series is found a) a long-term negative trend and b) a solar cycle dependence, both confirming earlier measurements and theoretical estimations. Moreover, a significant oscillation of quasi-biennial period is visible in LF reflection heights, indicating a reaction of the midlatitude mesosphere/lower thermosphere region on the equatorial quasi biennial oscillation.Am Observatorium Collm der Universität Leipzig werden die nächtlichen Reflexionshöhen von Langwellen auf 177 kHz unter Verwendung von Seitenbandinformationen in einem kleinen Bereich um 1.8 kHz gemessen. Die Messungen werden seit September 1982 durchgeführt und erlauben nunmehr Analysen von Langzeittrends und regulären Variationen der unteren Ionosphäre. Bei der Untersuchung der Zeitreihen fallen die folgenden Zusammenhänge auf: a)es existiert ein negativer Trend, welcher mit der Abkühlung der Stratosphäre in Zusammenhang steht, b) die Reflexionshöhe weist eine Modulation mit dem 11-Jährigen Sonnenfleckenzyklus auf und c) es ist eine deutliche quasi-zweijährige Schwingung sichtbar, die auf eine Kopplung der Mesosphäre und unteren Thermosphäre mit der äquatorialen Stratosphäre hinweist.
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Clark, Simon Daniel. "Long term behaviour of FRP structural foam cored sandwich beams." Thesis, University of Southampton, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.242619.
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Kürschner, Dierk, and Christoph Jacobi. "Long-term behaviour of E-region nighttime LF reflection heights." Universitätsbibliothek Leipzig, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-217519.
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The nighttime reflection height of low-frequency (LF) radio waves at oblique incidence is measured at Collm Observatory using 1.8 kHz sideband phase comparisons between the sky wave and the ground wave of a commercial 177 kHz LF transmitter. The measurements have been carried out continuously since September 1982, now allowing the analysis of trends and regular variations of the reflection height. In the time series is found a) a long-term negative trend and b) a solar cycle dependence, both confirming earlier measurements and theoretical estimations. Moreover, a significant oscillation of quasi-biennial period is visible in LF reflection heights, indicating a reaction of the midlatitude mesosphere/lower thermosphere region on the equatorial quasi biennial oscillationAm Observatorium Collm der Universität Leipzig werden die nächtlichen Reflexionshöhen von Langwellen auf 177 kHz unter Verwendung von Seitenbandinformationen in einem kleinen Bereich um 1.8 kHz gemessen. Die Messungen werden seit September 1982 durchgeführt und erlauben nunmehr Analysen von Langzeittrends und regulären Variationen der unteren Ionosphäre. Bei der Untersuchung der Zeitreihen fallen die folgenden Zusammenhänge auf: a)es existiert ein negativer Trend, welcher mit der Abkühlung der Stratosphäre in Zusammenhang steht, b) die Reflexionshöhe weist eine Modulation mit dem 11-Jährigen Sonnenfleckenzyklus auf und c) es ist eine deutliche quasi-zweijährige Schwingung sichtbar, die auf eine Kopplung der Mesosphäre und unteren Thermosphäre mit der äquatorialen Stratosphäre hinweist
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Boukendakdji, Mustapha. "Mechanical properties and long-term deformation of slag cement concrete." Thesis, University of Leeds, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236998.
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Simpson, Edmon Willoughby. "Long term behaviour of compost-like-output and its associated soils." Thesis, Durham University, 2008. http://etheses.dur.ac.uk/2545/.
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In 2000, the re-interpretation of the Waste Strategy (WS2000) for England and Wales was published. This document clearly laid out the Government's new strategy for managing waste and resources more efficiently, and detailed the transformations required to deliver more sustainable human development. Compost-like-output (CLO), a material derived from optimally composting municipal solid waste (MSW), is one potential avenue through which these targets may be achieved. When applied to agricultural land, or, as it is currently used, as a topsoil cover for landfill and reclaimed Brownfield sites, the adsorption of inorganic metal ions can involve several processes. The extent to which these processes occur in a soil is difficult to predict, but it is these processes that govern the concentrations of metal ions and complexes in soil solution and therefore ultimately determine the availability to plant root systems, access to groundwaters and thus the success of this waste management practice. To authenticate and potentially improve this procedure, a comprehensive Environmental Impact Assessment (EIA) is needed. The aim of this study was to identify, quantify and characterise, under specific conditions, the release behaviour of a number of leachate components emanating from CLO and its associated soils, and to compare this performance against those of other waste materials and an agricultural soil. It was found that, although leachates from all treatments were weakly alkaline, substantial metal dissolution had occurred. Numerous heavy metals, nutrients and water-soluble metal salts were identified as being in major breach of landfill and drinking and surface water directives, as well as being significantly higher in concentration than a typical agricultural soil for the Durham region. In particular, extremely high conductivities (> 20mS m(^-1)) were recorded in undiluted and mixed CLO treatment leachates. Poor aesthetic quality and an extremely heterogeneous nature were also highlighted as major detrimental properties. In view of this, a simple pre-washing procedure using tap-water was devised which showed that significant remediation value would be gained from this economical pre-treatment technique. However, for the most part, active remediation was found to be insignificant, and mixing significantly reduced the favourable high organic matter (OM) content characteristic of CLO. This suggests that the amending materials chosen offer little more amelioration than that achieved by passive dilution. Further sequential extraction experiments and principal component analyses revealed that prevailing environmental conditions are of central consequence to the levels of contamination incurred. For the CLO-containing treatments, major releases were found to occur under field conditions experienced during the lysimeter trials - an oxic environment. The potential for further substantial contamination has, however, been shown to be immanent if an anaerobic environmental setting prevails. These anoxic releases are also true for sewage sludge, but additionally this material has been shown to intermittently leach components, under the same field conditions and to a significantly greater degree, that are characteristic of acidic, reducing and oxidising environments. It is imperative, therefore, that if CLO or sewage sludge is to be used in agriculture, either as a basis for bio-fuel production or as a soil amendment, the prevailing conditions should be continuously monitored and any necessary action swiftly taken.
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Johnston, D. A. "The avian neural crest : behaviour and long-term survival in culture." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.376464.
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Alwis, Kapugama Geeganage Nadun Chaminda. "Accelerated testing for long-term stress-rupture behaviour of aramid fibres." Thesis, University of Cambridge, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.619983.
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Cox, James A. "Long-term serviceability behaviour of suction caisson supported offshore wind turbines." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.680352.
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Suction caissons have recently been considered as an alternative to monopile foundations for offshore wind turbines and met masts. By their nature, such structures have stringent limit states imposed on their design dictating the first modal frequency and the allowable structural rotations. The aim of this thesis is to assess how cyclic loading will affect the long-term serviceability behaviour of such an offshore structure. The behaviour of such a representative caisson system was assessed through the use of a series of scale model tests conducted in dry sand, replicating a fully drained prototype condition. These tests were designed to record the foundation stiffness, its evolution under cyclic loading, how the system accumulates rotation with loading cycles and the dynamic properties of a caisson system. This was conducted at a number of scales under single-g and multi-g conditions. Considering all of the experimentally obtained data it was possible to analyse and provide a prediction as to the long-term behaviour of such an offshore structure. It was discovered that the foundation stiffness was highly dependent on the strain level and under the application of cyclic loading the stiffness would tend to increase in a logarithmic manner. In addition it was found that when subjected to a cyclic load a caisson system will accumulate rotation in accordance with a power relationship. Finally the dynamic properties were found to closely match pre-existing formulations describing a simple dynamic system. Considering these results it was possible to produce an analytical model to describe the evolution of serviceability of a caisson founded offshore structure. Latterly this model was applied to a series of representative cyclic loading test to examine the validity of the complete model.
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Khodarinova, L. A. "Game-theoretic analysis of behaviour in the context of long-term relationships." Thesis, Nottingham Trent University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.247024.
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Cooke, K. R. "Determinants of the labour supply behaviour of families in long-term unemployment." Thesis, University of York, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.233200.
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Li, Zili. "Long-term behaviour of cast-iron tunnel cross passage in London clay." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.708631.
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Napiah, Madzlan B. "Fatigue and long term deformation behaviour of polymer modified hot rolled asphalt." Thesis, University of Leeds, 1993. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.712012.
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Menzio, Davide. "Long term chaotic attitude behaviour on highly eccentric orbits : INTEGRAL Case Study." Thesis, KTH, Farkost och flyg, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-203809.
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The main issues discussed in this paper are related to the refinement of the on-ground casualty risk computation for the specific case of INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL). The current approach, unable to predict the spacecraft attitude motion, assumes random tumbling motion as initial condition to simulate the fragmentation process. The wide experience in break-up analysis, acquired after years of practice with simulation, identified attitude to be one of the major drivers of uncertainty. The Space Debris Office (SDO) demanded a specific research in the field of the long-term propagation applied to the attitude motion and INTEGRAL offered the perfect test bench to conduct a preliminary study in this direction. In particular, observing whether environmental torques were able to trigger stable attitude motion, maintainable till re-entry, was considered to be the major challenge. The propagation of coupled orbitalattitude motion for a random attitude configuration represents only one side of the coin. Indeed, chaos theory analysis constituted the other. The use of the Poincaré map in a non-canonical way managed to bring evidence for constrained motion in the angular rate motion of INTEGRAL, under gravity perturbations. Such results allowed to conduct further investigation on the overall attitude motion and estimate that the attitude configuration at the re-entry appears as precession about the maximum axis of inertia, in the majority of the cases.De aspekter som behandlas i detta examensarbete är relaterade till skaderisken när rymdskrot som passerar atmosfären och landar på marken. Detta illustreras för en specifik satellit: INTEGRAL. Den nuvarande strategin som används i rymdindustrin är oförmögen att tillräckligt noggrant prediktera satellitens at-titydförändring vid atmosfärsinträdet och antar därför en stokastisk tumlande rörelse som initialvillkor för en analys av sönderdelningen av farkosten när den passerar atmosfären. Den erfarenhet som finns i rymdindustrin kring sönderdelningssimuleringar har identifierat att attityden är den faktor som genererar störst osäkerhet i resultaten. För att bättre förstå attitydens betydelse användes INTEGRAL i den fallstudie som presenteras i denna rapport. Specifikt studerades hur externa kraftmoment från rymdmiljön kan skapa en stabil attitydrörelse, som behålls ända till farkostens inträde i atmosfären. Propageringen av den kopplade rörelsen bana-attityd för en stokastisk attitydkonfiguration representerar endast en del av denna analys, där kaosteori representerar den andra delen. Med hjälp av Poincaré-mappning har simuleringar som indikerar en begränsad vinkelhastighet för INTEGRAL-satelliten när den utsätts för gravitationsstörning. I majoriteten av de analyserade fallen representerades attityden av en precession kring den största huvudtröghetsaxeln.
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Parmar, Ravindra. "The long-term behaviour of butt fusion welds in polyethylene pipeline systems." Thesis, Brunel University, 1986. http://bura.brunel.ac.uk/handle/2438/6631.
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The objective of the study was to examine factors that influence the strength of butt welds and gain an understanding of the process of failure. The study was divided into several sectors. The first and primary part of the programme was to determine the extent to which the pipe system's long-term strength under both internal fluctuating and constant pressure is reduced by the presence of axially misaligned butt welds. The second objective was to examine fracture initiation sites and crack propagation paths of the failed aligned and misaligned butt welded samples in relation to the melt flow zone and the weld bead in order to establish the cause of failure. Finally the project considered the influence of selected welding parameters on the fatigue performance of aligned butt fusion welds and an investigation into the influence of elevated temperature (79°C) testing technique on the basic material's properties. Fatigue and stress-rupture lifetimes were found to decrease significantly with increasing axial misalignment at the butt fusion weld in 63,90 and 125mm MDPE pipe systems at 79°C in a water environment. In the butt fusion weld having axial misalignment of 20 per cent of the wall thickness and above, the reduction in the fatigue and stress-rupture lifetime was greater than 50 per cent compared to the aligned weld. It was not clear whether there is a pipe size effect or not; there was no marked change in the fatigue performance of misaligned butt welds for the three pipe diameters examined. However, the fatigue performance of the aligned butt welds in 90 and 125mm was noticeably better compared to 63mm pipe systems. The stress rupture performance of misaligned butt welds in 90 and 125mm MDPE pipes was more than halved compared to those in 63mm pipe systems. Both the fatigue and stress rupture performance of misaligned butt welds could be explained in terms of amplified axial stress and in general, the Ory expression for evaluating the increase in axial stress due to misalignment appears to be valid. The temperature dependence of the fatigue performance of aligned and misaligned butt fusion welds in 63 and 90mm MDPE pipe systems suggests that if continuous internal fluctuating pressure under the conditions examined is maintained, then the butt fusion welds with axial misalignment of below 10 per cent of the wall thickness may well meet the design lifetime of 50 years at the service termperature. Under stress-rupture conditions, all the misaligned butt welds considered in the three pipe diameters surpassed the minimum specified requirement of 170 hours at 79°C. The fatigue was the most aggresive condition of the two for minor misalignment. Examination of the circumferential butt weld failures revealed that the crack invariably initiated from the notch located at the inner weld bead and no preferred crack propagation path was taken in relation to the melt flow zone. It was proved that the notch was responsible for the observed circumferential failure of aligned butt welds in 63mm MDPE pipes by testing these butt fusion welds where the internal weld bead was machined off. The failure site for the internal weld bead machined off sample was in the pipe remote from the weld inferring that the material in the melt flow zone does not constitute any weakness. The effect of elevated temperature (79°C) testing in 63mm HDPE pipe was found to increase the density (and crystallinity) signifying a slow annealing process in the material. However, the changes in these parameters were not of sufficient scale to strongly influence the performance. The main effect of elevated temperature testing in water environment appears to be the extraction of stabiliser from the base polymer as was indicated by the rapid decrease in oxidation induction time with the ageing times.
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Asbia, Salim Badre. "Short and long-term behaviour of dental cast restorations under compressive stresses." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/24720.
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This study examined indirectly the behaviour of zinc phosphate cement used to lute cast gold crowns. In order to standardise an in vitro method, cast nickel chrome dies were to represent natural molar teeth prepared to receive full gold crowns whilst the cast gold crowns were produced using standardised laboratory techniques. Initial work was undertaken to develop methods to control the distribution and film thickness of the cement beneath the crown. These were investigated together with the effects of preparations geometry and casting rigidity. Cement coverage had a strong influence on strain distribution. Increasing the cement film thickness led to an increase in compressive microstrain in the walls of the crowns, whilst both increasing the convergence angle and reducing the axial wall height of the preparation increased the axial compressive microstrain. However, the influence of axial wall height was greater than that of convergence angle. The influence of the casting rigidity showed an interesting finding. Heat treatment of the crown did not show differences in microstrain compared with the as cast control group, but increasing the occlusal surface thickness by a factor of three doubled the compressive axial microstrain recorded. The strain response curves for uncemented, partially cemented and fully cemented gold crowns to increasing static loads were recorded: these data were used to characterise the microstrain measurements from the later series of dynamic loading experiments. In the dynamic loading series, the crowns were partially cemented on their dies and axial loading was applies between 0-450N for approximately 300,000 cycles with a frequency of about 2Hz. In a series of four experiments, pairs of crowns were tested dry, immersed in water, in water and acid, and in acid alone (pH 2.74). The results were plotted as microstrain against a number of cycles. These showed that the hydration had a strong effect on the strain recorded on the axial surfaces of the cemented crowns compared with the dry samples. Whilst the presence of pure water decreased the microstrain, the presence of acid increased it. The pronounced effects were recorded in the presence of acidic media. Microscopic investigation showed damage to the luting cement was increased by the presence of moisture and further increased by the presence of acid. The conclusions drawn from this study were that the use of axially-placed strain gauges provided a method for monitoring the strain in the axial walls of cast gold crowns cemented with zinc phosphate cement. The strains were indicative of the condition of the bond between the die and crown provided by the cement. This method has further application in the non-destructive monitoring of the bond provided by luting cements between an indirect restoration and the underlying preparation.
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Murray, Susan. "The role of mood in long-term weight maintenance and behaviour change." Thesis, University of Aberdeen, 2014. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=230024.
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This thesis explores the role of mood in adherence to changes in behaviour required for weight maintenance following weight loss in an obese sample. Significant increases in physical activity are necessary for successful weight maintenance, yet this change in lifestyle remains challenging for many. Anecdotally, the importance of being in the 'right mood' to make lifestyle changes is frequently reported. A systematic review of the weight maintenance literature revealed that a number of behaviour change techniques were associated with effective weight maintenance interventions. Therefore, the current randomised control study employed relevant behaviour change techniques within two goal setting interventions to improve either daily steps walked or mood compared to a control group in a weight loss programme cohort. The number of daily steps walked and mood were evaluated and the following questions were addressed: 1) In an obese population enrolled in a weight loss programme, do goal-setting interventions increase the number of steps walked compared to those in a control group? 2) Does the mood score differ for those participants in the mood improvement intervention group compared to those in the steps-walked intervention or control groups? 3) Does weight change differ for those individuals who have shown mood improvement compared to those whose mood is unchanged/worsened? The primary outcomes of steps walked, mood and weight were recorded immediately after intervention and again after unsupervised follow up 6-months later. The results showed that all groups increased the number of steps walked but not significantly so. This increase was greatest for the steps-walked group during the active intervention period but greatest for the mood intervention group during the unsupervised follow-up period. Mood improved significantly for all groups and was associated with significantly increased weight loss at follow-up. A trend for increased steps walked being associated with improved mood was observed in the 6-month follow up period. These findings highlight the links between mood and continued participation in lifestyle behaviour changes required for weight maintenance. Future research priorities are outlined for this field.
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Braimah, Abass. "Long-term and fatigue behaviour of carbon fibre reinforced polymer prestressed concrete beams." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape3/PQDD_0018/NQ54403.pdf.
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Carnerero, M. I., C. M. Raiteri, M. Villata, J. A. Acosta-Pulido, V. M. Larionov, P. S. Smith, F. D'Ammando, et al. "Dissecting the long-term emission behaviour of the BL Lac object Mrk 421." OXFORD UNIV PRESS, 2017. http://hdl.handle.net/10150/626278.
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We report on long-term multiwavelength monitoring of blazar Mrk 421 by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope (GASP-WEBT) collaboration and Steward Observatory, and by the Swift and Fermi satellites. We study the source behaviour in the period 2007-2015, characterized by several extreme flares. The ratio between the optical, X-ray and gamma-ray fluxes is very variable. The gamma-ray flux variations show a fair correlation with the optical ones starting from 2012. We analyse spectropolarimetric data and find wavelength-dependence of the polarization degree (P), which is compatible with the presence of the host galaxy, and no wavelength dependence of the electric vector polarization angle (EVPA). Optical polarimetry shows a lack of simple correlation between P and flux and wide rotations of the EVPA. We build broad-band spectral energy distributions with simultaneous near-infrared and optical data from the GASP-WEBT and ultraviolet and X-ray data from the Swift satellite. They show strong variability in both flux and X-ray spectral shape and suggest a shift of the synchrotron peak up to a factor of similar to 50 in frequency. The interpretation of the flux and spectral variability is compatible with jet models including at least two emitting regions that can change their orientation with respect to the line of sight.
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Martin, Neil. "Behavioural effects of long-term multi-sensory stimulation : the benefits of the #Snoezelen' experience." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389642.
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Smed, Sinne. "Empirial studies on "Health, Information and Consumer Behaviour" : long-term unemployment, wages and enrolment /." Kbh. : Department of Economics, University of Copenhagen, 2008. http://curis.ku.dk/ws/fbspretrieve/11506187/PDF.
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Abbasi, Vahid. "Short and long term behaviour of assemblages of crushed rock particles in oedometer compression." Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/27288.
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Au cours des dernières décennies, un noyau plutôt mince supporté par des épaulements en enrochement a été le modèle le plus économique et sans danger pour les barrages. Plusieurs rapports d'inspection de tassement et de déformation des barrages en enrochement au cours de la mise en eau et le fonctionnement de ces structures. Les tassements rapides ont été associés à la mise en eau. Cependant, la pression hydrostatique peut également contribuer à des changements considérables dans les déformations volumétriques au début de fonctionnement de barrages en amont. Le premier objectif de cette thèse est de montrer expérimentalement l'influence de la pression hydrostatique sur les matériaux concassés d’enrochement. Les essais de compression unidimensionnelle ont été menés par un grand oedomètre. L'équipement est conçu de manière à modifier la pression hydrostatique lors de l'essai, sans aucune influence sur les contraintes effectives. Premièrement, une étude approfondie est réalisée sur l’influence des dimensions de cellule et aussi l’influence de système de transfert de la charge à l’échantillon. Il a été établi que la hauteur de la cellule a de grandes influences sur la réponse de ces roches concassées en compression. La force de frottement entre la cellule et l'échantillon est la source de comportement varié de l’échantillon avec des hauteurs différentes. Une méthode simple, basée sur un double essai oedométrique peut être utilisée afin de définir la force de frottement dans les échantillons. Trois systèmes sont utilisés pour étudier l'influence de différents systèmes de chargement des échantillons. Ces systèmes transfèrent la charge à l’aide d’une plaque fixe, semi-fixe et rotulé. La plaque fixe transfère la charge d’une manière nonuniforme à l'échantillon, contrairement à d’autres systèmes étudiés. Donc, les résultats obtenus avec la plaque fixe de chargement doivent être utilisés avec une prudence particulière. Le comportement des matériaux d’enrochement dépend de plusieurs paramètres. Basés sur l’utilité de ces matériaux dans le barrage, quatre paramètres sont choisis pour cette étude. Ces paramètres sont la densité, le type de roches concassées, le niveau de contrainte et la taille des roches concassées. L'influence de ces paramètres sur le comportement à court terme de ces matériaux a été définie avec les essais expérimentaux. L’essai de compression unidimensionnelle a été choisi pour les études sur les enrochements avec des roches concassées. Les conditions de matériau ont été à sec, saturé sous la pression atmosphérique ou la pression hydrostatique. Le module oedométrique est utilisé pour représenter l'état de matériau dans l’essai de compression unidimensionnel. Un essai de fluage a été réalisé pour montrer le comportement à long-terme des matériaux granulaires grossiers saturés. L’essai a été réalisé sur les roches concassées de granite en plusieurs niveaux de charge et sous une pression hydrostatique constante. Les résultats de l’essai montrent une relation linéaire entre la contrainte et le temps dans une échelle logarithmique. La thèse présente également des informations sur le modèle phénoménologique à trois paramètres de Zhang et al. (Zhang et al.), développé pour simuler le comportement du fluage à plusieurs niveaux du sable saturé en compression. Le même modèle a été utilisé pour décrire pertinemment les résultats de l'essai sur des matériaux granulaires grossiers. Le comportement semblable de matériaux granulaires à particules fines et grossiers confirme l’existence de mécanismes identiques dans la structure des matériaux granulaires sous effet de fluage. Le deuxième essai de fluage a été réalisé sous différents niveaux de pression hydrostatique. Les résultats de l’essai montrent une relation linéaire entre la pression hydrostatique et le temps dans une échelle logarithmique. La thèse présente également un modèle de fluage qui prendre en compte l’effet de la pression hydrostatique sur des matériaux granulaires grossiers.During the past decades, a rather thin core supported by rockfill shoulders was the most economical and safe design for dams. There are different reports of settlement and deformation inspection of rockfill dams during impounding and operation of these structures. The rapid collapse settlements have been associated with water impoundment. However, hydrostatic pressure may also contribute to significant change in volumetric deformations during the life of dams in upstream. The first aim of this thesis is to show experimentally the influence of hydrostatic pressure on crushed rockfill materials. In this way, the one-dimensional compression tests were conducted using the large oedometer equipment. The equipment is conceived in a manner to change the hydrostatic pressure during the test without any influences on the effective stresses. A comprehensive study is primarily carried out on the equipment effects on the test results. This study provides the impact of cell dimensions, and also the system influences on the loading transfer to sample. It was established that the height of the cell has great influences on the response of the crushed rock in compression. The frictional force between cell and sample is the source of dissimilarity in behaviour of the sample with different heights. A sample method, based on a double oedometer test, can be used to define the frictional force in the samples. Three systems are used to investigate the influence of different techniques of loading the samples. These systems transfer the loading using the fixed, the semi-fixed and the rotational platen. The fixed platen system transfers the loading in a non-uniform manner to the sample in contrast to other studied systems. Thus, the results obtained with the fixed platen of loading, must be used with a special caution. The behaviour of rockfill materials depends on several parameters. Based on the materials utility in dam, four parameters are chosen for this study. These parameters were the bulk density, the rock mineral type, the stress state and the particle size. The influence of these parameters on the short-term mechanical behaviour is defined with the experimental tests. The tests consisted of the one-dimensional compression tests on the uniform crushed rock particles. The materials are tested in the similar conditions which they are in rockfill dams means the air-dry condition, the flooded under atmospheric or hydrostatic pressure. The oedometric modulus is used to represent the mechanical state of materials under one-dimensional compression test. The one-dimensional creep test is also carried out to show the long-term behaviour of saturated coarse granular materials. The test was realised on the granitic crushed rock particles in multiple stage of stress under a constant hydrostatic pressure. The test results show a linear relationship between stress-strain and strain-time in a log-log scale. The thesis also presents the information on the three-parameter phenomenological model of Zhang et al.(2006) developed to reproduce the multiple stage creep behaviour of saturated sand in compression. The same model is used to describe accurately the results of test on coarse crushed rock particles. The similar behaviour of coarse and fine granular materials confirms the occurring of identical mechanisms in the structure of granular materials under creep effect. The second creep test was conducted under different levels of hydrostatic pressure. The test results show a linear relationship between the hydrostatic pressure and time in a logarithmic scale. The thesis also presents a creep model that takes into account the hydrostatic pressure effect in coarse granular materials.
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Ferreira, José Nuno Varandas da Silva. "Long-term behaviour of railway transitions under dynamic loading application to soft soil sites." Doctoral thesis, Faculdade de Ciências e Tecnologia, 2013. http://hdl.handle.net/10362/10145.
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Dissertação para obtenção do Grau de Doutor em
Engenharia CivilTransition zones in railway tracks are built to mitigate damage and wear to tracks and trains, and discomfort to passengers, caused by structural and foundation discontinuities, such as those introduced by bridge approaches or culverts. However, additional strains are still generated that cause changes of track geometry, that lead to more frequent maintenance operations and sometimes speed restrictions, that raise costs, and need to be minimized. This thesis addresses those questions and describes research undertaken to model the dynamic response of the railway tracks, taking into account the behaviour of ballast at the aforementioned railway transition zones, where the long-term settlements are amplified by dynamical loading on the ballast due to the discontinuities. Novel numerical models for the simulation of the dynamic response of the system soilballast-track-vehicle and accounting for those phenomena are presented. The models are validated by field measurements performed at a passage over a culvert, located in a soft soil site. The models include the unloaded level of the track, the possibility of voids under the sleepers, and the non-linear constitutive behaviour of the ballast, as well as representation, albeit simplified, of the vehicles. The forces transmitted to the ballast at transition areas vary considerably, both in time and space: loading of ballast reaches higher values than in regular tracks, and the additional vibrations cause larger differences between loads transmitted to consecutive sleepers. This causes higher densification of ballast at transition zones. Transition zones solely composed of approach slabs are not effective in soft soil sites. The soil and ballast at approach regions settle more than the segment on top of the much stiffer structure, leading to the appearance of hanging sleepers. The subsequent combined effect of lower load on part of the ballast and motion of the approach slabs results on increased settlement of the ballast and sub-ballast, increasing the voids under the sleepers, and causing more severe actions on the track. Possible improvement measures were modeled and tested computationally at the later stages of the thesis. The numerical simulations showed that the use of soft railpads on the stiff side of the transition is beneficial, provided the problem is mostly caused by stiffness variation of the track support. Slab track solution was also tested and showed advantages over the ballasted track by showing much smaller differential rail displacements,for identical change of the track support stiffness.
Fundação para a Ciência e Tecnologia - Ph.D grant (SFRH/BD/25297/2005), through the project “Interacção solo-via férrea para comboios de alta velocidade” (POCI/ECM/61114/2004), and through the project SMARTRACK (PTDC/EME-PME/101419/2008)
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Karlsson, Anton. "Population Models with Age and Space Structure." Thesis, Linköpings universitet, Matematik och tillämpad matematik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-134926.
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In this thesis, basic concepts of populational models are studied from a theoretical point of view, especially the long term behaviours. All models are at least time dependent with additional age structure, spatial structure. The last model which is an extension of the von Foerster equation, is dependent on all o f these structures and have a long-term solution for large values of time. Modeling population is a frequent subject in modern biology. It is hard to create a model that appears as realistic as possible. First one might consider that a population size is governed by the current size of the population, along with rates of how each individual contributes (give birth), so that the population increases. and how frequent an individual dies, causing the population to decrease in size. However these sort of models can only describe the size of population in a shorter span of time.
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Bull, Eleanor. "The long-term effects of MDMA on behaviour and serotonergic receptor function in the rat." Thesis, University of Nottingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403384.
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Jarbin, Håkan. "Long-term Outcome, Suicidal behaviour, Quality of Life and Expressed Emotion in Adolescent Onset Psychotic Disorders." Doctoral thesis, Uppsala University, Department of Neuroscience, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3341.
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This study investigated a consecutive cohort of 88 youngsters with onset of a psychotic disorder at age 15.7 (sd 1.5) years and followed-up 10.6 (sd 3.6) years after first admission at the age of 26.5 (sd 3.7) years. A subsample of 15 subjects were assessed with the Five Minute Speech Sample for measuring Expressed Emotion and subsequent recording of relapses during a two year period.
A diagnostic split between schizophrenia spectrum psychosis and affective psychotic disorder was usually stable over time. The main diagnostic shift was an influx to schizophrenia spectrum disorder of subjects with a better premorbid function and less insidious onset as compared to those with a stable schizophrenia diagnosis.
Early onset schizophrenia spectrum disorder usually had a poor functional outcome. Most subjects needed support in the form of a disability pension. Early onset affective psychotic disorder usually had a good functional outcome. Most subjects worked and enjoyed regular friendships. The functional level before onset of illness was the best predictor of future functional level in psychotic disorders. A family history of non-affective psychosis predicted a worse function in schizophrenia. Frequent episodes and low intelligence predicted a worse function in affective disorders.
Four men (4.5% of the sample) committed suicide. The risk of suicide was increased about 30 times. Almost a third of subjects attempted suicide. Females made more attempts. Suicide attempts were related to more depressive symptoms but less negative symptoms at first episode, to readmissions and to dependence on nicotine.
Subjects with schizophrenia spectrum psychoses were less satisfied with life than those with affective psychotic disorder. Subjective satisfaction in schizophrenia was strongly associated to depressive mood while in affective disorders it was associated to degree of employment.
Adolescents with psychosis in families rated high or borderline high in Expressed Emotion either during first episode or after discharge had an increased risk of relapse.
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de, Medeiros Cynthia. "Acute and long-term effects of early life inflammatory pain on brain morphometry and adult behaviour." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=97245.
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Premature infants receive numerous painful procedures while in the neonatal intensive care unit (NICU). Pain may lead to long-term negative consequences that include cognitive, social, and learning deficits and a higher incidence of depression. The mechanisms by which pain can exert these effects are currently unclear. To examine more precisely the effect of neonatal pain on brain morphology and adult behaviour, a rat model of acute neonatal inflammatory pain was used to mimic pain experienced by preterm infants in the NICU. Male rat pups were injected with either a low formalin dose (0.75%-1.5%), saline (0.9%), or remained uninjected during the first 2 weeks of life. First, we performed magnetic resonance imaging (MRI) on postnatal days (PND) 15 and 35 to identify potential changes in brain volume in response to pain. In a second study, we examined cellular proliferation (using Ki67, an endogenous marker of cell proliferation) and neurogenesis (using survival of BrdU-labelled cells) in response to pain in regions identified from our MRI analysis. Neurons were also counted using NeuN (a marker of mature neurons). Our final study investigated changes in anxiety and fear related behaviours in adult offspring subjected to pain as neonates. We consistently found that neonatal pain causes moderate hypertrophy in the basolateral amygdala (BLA) in PND 15 pups. These volumetric changes were not observed on PND 35. Similarly, neuronal counts (NeuN) showed a moderate increase in the BLA of PND 15 pain-exposed pups compared to controls (p=0.062), however, this effect was not seen on PND 35. However, there was no significant treatment effect of pain on Ki67-positive cells on PND 15, suggesting that neuronal proliferation induced by early pain occurred prior to PND 15. In addition, pain had no effect on the number of NeuN and BrdU positive cells on PND 35, suggesting that pain has transient effects. In adulthood, rats that were exposed to pain as neonates did not differ from controls (either saline injected or uninjected) in behavioural tests measuring anxiety (social interaction and elevated plus maze) and fear (fear conditioning). Overall, these results show that repeated exposure to mild inflammatory pain during the neonatal period produces transient changes in BLA morphology, the consequences of which do not affect adult behaviours mediated by this structure. The early transient hypertrophic response to pain in the BLA may trigger plastic changes sufficient to protect the animal from any potentially negative functional consequences. Keywords: pain, neonate, amygdala, anxiety, fear, proliferation, survival, neuronLors de leur séjour dans l'unité des soins intensifs, les bébés prématurés sont soumis a de nombreuses procédures douloureuses qui ne sont pas toujours bien contrôlées et qui ont des conséquences a long terme sur les fonctions cognitives, l'apprentissage et les interactions sociales. Les mécanismes qui sont impliqués sont encore peu connus. Au cours de ce travail, nous avons utilisé un modèle animal de douleur inflammatoire répétée au cours de la période néonatale chez le rat pour comprendre les effets à long terme sur la morphologie du cerveau et le comportement relié à l'anxiété à l'âge adulte. Nous avons injecté les pattes arrières des ratons entre le jour 3 et 14 de la vie postnatale avec soit de la saline (0.9%) ou de la formaline (0.75-1.5%) une fois par jour. Un groupe contrôle n'a pas été injecté. Dans une première étude, nous avons mesure les changements de volume du cerveau induits par la douleur au jour 15 et 35 de vie postnatale. À l'aide de la résonance magnétique (scanner de 7T), nous avons pu démontrer une augmentation presque significative du volume de l'amygdale basolatérale (BLA) chez les ratons de 15 jours soumis à la douleur compares aux contrôles injectes à la saline. Par contre, cette hypertrophie amygdalienne n'était que transitoire car les différences de volume avaient disparu au jour 35. En quantifiant le nombre de neurones matures (en immunohistochimie avec NeuN) dans la BLA à ces mêmes âges, nous avons pu confirmer que le l'exposition à la douleur durant le 2 premières semaines de vie produit une hypertrophie neuronale dans la BLA au jour 15 mais que celle-ci n'est plus observée après le sevrage au jour 35. Nous avons également déterminé que l'hypertrophie au jour 15 était probablement due a une prolifération cellulaire qui avait eu lieu avant cette période car le nombre de cellules avec un marquage positif pour le Ki-67 (un marqueur endogène de prolifération) était semblable entre les groupes douleur et contrôles au jour 15. De même, le nombre de cellules ayant incorpore le BrdU au jour 15 n'était pas différent au jour 35 selon les traitements. Ceci suggère également que l'effet de la douleur sur la morphologie de la BLA se limite à la période pendant laquelle les ratons sont soumis à la douleur. Finalement, à l'âge adulte, nous n'avons pas observé de différence significative entre les groupes contrôles et douleur en ce qui a trait à l'anxiété (par le test de interaction sociale et « elevated plus maze ») ou par rapport au conditionnement à l'anxiété (par le test de « fear conditioning »). Ces résultats nous permettent de conclure qu'une douleur de type inflammatoire modeste au cours des deux premières semaines de vie chez les ratons produit une hypertrophie neuronale transitoire de la BLA, une structure impliquée dans les émotions et les comportements relatifs à l'anxiété. Nous n'avons pas détecté de conséquences à long terme sur le morphologie neuronale ou les comportements d'anxiété suite a cette expérience néonatale.
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Jarbin, Håkan. "Long-term outcome, suicidal behaviour, quality of life and expressed emotion in adolescent onset psychotic disorders /." Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-3341.
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Nicholls, Briony Rachel. "An investigation into the long-term effects of experimental limbic epilepsy of exploratory behaviour of rats." Thesis, University of Oxford, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240652.
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Molinari, Claire Marcella. "The environment, intergenerational equity & long-term investment." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:30dd270b-3f0f-4b8b-979e-904af5cb597b.
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This thesis brings together two responses to the question ‘how can the law extend the timeframe for environmentally relevant decision-making?’ The first response is drawn from the context of institutional investment, and addresses the timeframe and breadth of environmental considerations in pension fund investment decision-making. The second response is related to the context of public environmental decision-making by legislators, the judiciary, and administrators. Three themes underlie and bind the thesis: the challenges to decision-making posed by the particular temporal and spatial characteristics of environmental problems, the existence and effects of short-termism in a variety of contexts, and the legal notion of the trust as a means for analysing and addressing problems of a long-term or intergenerational nature. These themes are borne out in each of the four substantive chapters. Chapter III sets out to demonstrate the theoretical potential of pension funds to drive the reduction of firms’ environmental impact, and, focusing particularly on the notion of fiduciary duty, explores the barriers that stand in their way. Chapter IV provides a practical application of the theoretical recommendations outlined in its predecessor. It provides a framework outlining how pension funds might implement a longer term, more sustainable approach to investing. The second half of the thesis, operating in the context of public environmental decision-making, is centred upon a particularly poignant legal notion with respect to the environment and time: the concept of intergenerational equity. Just as the first half of the thesis deals with the timeframes relevant to investment decision-making by pension funds within the bounds of fiduciary duty, largely a private law affair with public implications, the second half of the thesis is concerned with the principle of intergenerational equity as a means for extending the decision-making timeframe of legislative, judicial and administrative decision-makers. As previous analyses of the concept of intergenerational equity provide little insight into its practical implications when applied to particular factual situation, Chapter V sets out the structure of the principle of intergenerational equity as revealed by case law. Chapter VI brings together the issues from the first three papers by conceptualising intergenerational equity in resource management as an issue of long-term investment. Long-term environmental decision-making faces many obstacles. Individual behavioural biases, short-term financial incentive structures, the myopic pressures of the electoral cycle and the tendency of the common law to reinforce the (often shorttermist) status quo all present significant barriers to the capacity of both private and public decision-makers to act in ways that favour the longer term interests of the environment. Nonetheless, this thesis argues that there is reason for hope: drawing upon the three themes that underlie all of the substantive Chapters, it articulates potential legislative changes and recommends the adoption of particular governance structures to overcome barriers to long-term environmental decision-making.
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Daugevičius, Mykolas. "Influence of long-term load on the behaviour of reinforced concrete beams strengthened with carbon fibre composite." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2011. http://vddb.laba.lt/obj/LT-eLABa-0001:E.02~2011~D_20110210_102023-13761.
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The influence of long-term load on the reinforced concrete beams strength-ened with a carbon fiber composite layer in the tensioned zone is considered in this dissertation. The evolution of deformations in the layers of the beams and the evolution of beam deflection is analyzed. The load carrying capacities after a long-term load action are also determined herein. The built-up-bars theory for calculation of deflections and the load carrying capacity after a long-term load action is presented in this dissertation. The thesis consists of an introduction, four main chapters, the results and conclusions and a list of used literature. The introduction describes the major objectives of the dissertation. It pre-sents the aims, the methods of research, the scientific novelty and defended pro-positions. The first chapter reviews application of carbon fiber composite polymer in strengthening structures. The influence of a long term load on concrete, polymer matrix, carbon fiber reinforced composite, strengthened concrete beams is also considered. In addition, it considers the calculation methods that evaluate the long term load influence. The second chapter is dedicated to applying of the built-up-bars theory in calculation of deflections and the load carrying capacity, including long term load action. Also, variation of concrete and carbon fiber composite contact stiff-ness is presented in this chapter. Chapter three presents the carried out experiments. It describes the experi-mental... [to full text]Disertacijoje nagrinėjama lenkiamųjų gelžbetoninių sijų, tempiamojoje zo-noje sustiprintų anglies pluošto kompozitu, elgsena esant ilgalaikiam statinės apkrovos poveikiui. Disertacinio darbo tikslas – atlikti eksperimentinius tyrimus ir nustatyti ilgalaikės apkrovos poveikį sijos laikomajai galiai bei įlinkių vysty-muisi; apskaičiuoti sijos įlinkį pagal sudėtinių strypų teoriją įvertinant ilgalaikės statinės apkrovos poveikį bei betono ir anglies pluošto kompozito jungties stan-dumo pokytį dėl šlyties valkšnumo deformacijų prieaugio. Disertaciją sudaro: įvadas, keturi pagrindiniai skyriai, rezultatų apibendri-nimas ir išvados, naudotos literatūros sąrašas, autoriaus publikacijų disertacijos tema sąrašas. Įvadiniame skyriuje nagrinėjama tiriamoji problema ir darbo aktualumas, nurodytas tyrimų objektas, suformuluoti darbo tikslai ir uždaviniai, pateikta ty-rimų metodika, aptarta darbo svarba ir praktinė rezultatų reikšmė, pristatyti gi-namieji teiginiai. Pirmajame skyriuje atlikta literatūros apžvalga. Čia nagrinėjamas ilgalaikės apkrovos ir aplinkos poveikis anglies pluošto kompozitui, kompozito ir betono jungčiai bei gelžbetoninių sijų elgsenai. Pateikiami sustiprintų sijų elgsenos eks-perimentinių tyrimų, veikiant trumpalaike ir ilgalaike apkrova, rezultatai. Apta-riamos skaičiavimo metodikos, vertinančios ilgalaikį apkrovos poveikį. Antrajame skyriuje pateikiama skaičiavimo metodika, grindžiama sudėtinių strypų teorija. Skaičiavimo metodika skirta sijų, sustiprintų anglies... [toliau žr. visą tekstą]
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Causey, Michael J. "Delineating pastoralist behaviour and long-term environmental change : a GIS landscape approach on the Laikipia Plateau, Kenya." Thesis, University of Oxford, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.496430.
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Lehocky, Milan. "The stochastic behaviour of crude oil futures prices and the valuation of long term oil-linked assets." Thesis, University of Manchester, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.633024.
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This study proposes a theoretically consistent approach to the valuation of long-term oil and gas linked natural resources. We develop a model for the arbitrage-free valuation of future cash-flows from oil and gas reserves, arguing that oil and gas reserves themselves can be viewed as contingent claims. Our valuation framework is based on the two-factor stochastic convenience yield model which was first presented in Gibson and Schwartz (1990 a,b ). We also compare the theoretical properties of the Brennan and Schwartz (1985) one-factor model to the two-factor stochastic model of the term structure of crude oil futures prices and their implication with respect to the valuation of oil and gas reserves. The analysis reveals strong mean reversion in the short term convenience yield process suggesting that the constant convenience yield assumption made in the Brennan and Schwartz (1985) one-factor model is unjustified. Additionally, the analysis provides evidence of a term structure of convenience yields which levels off as time to maturity increases. From a theoretical point of view we conclude that the two-factor Gibson and Schwartz (1990 a,b) model performs better in capturing the real life behaviour of crude oil futures prices. The greater flexibility of the two-factor model proves pivotal in modelling the observed term structure smiles observed on the NYMEX WTI market. However, the analysis also highlights potential shortcomings of the two-factor model with respect to the implicit assumptions made in modelling the stochastic variables, and we present findings which are in contrast to the original Gibson and Schwartz (1990 b) study. In particular, our empirical analysis of the time series behaviour of the two stochastic variables casts doubt on the appropriateness of the Brownian motion and simple mean-reversion assumption made for the spot price of oil and convenience yield respectively. Moreover, we also find evidence of time-varying stochastic parameters. Most importantly however, our analysis suggests contrary to Gibson and Schwartz (1990 a,b) that the market price of convenience yield risk is larger and tends to be positive when far out contracts are included in the term structure fits. This finding is in line with Schwartz (1997). Contrary to prior findings, our results suggest that a unit convenience yield is less rewarded in the long-run and the present value of one barrel of crude oil deliverable in ten years loses only about 50% of its value. We also provide evidence that the market price of convenience yield risk is varying both with time and time to maturity and show the average term structure of market prices of convenience yield risk. Moreover, we hypothesise that the market price of convenience yield risk might be inversely related to the level of the convenience yield. This findings might be investigated by future research. Relating alternative economic and accounting based reserve value measures to market prices showed weak evidence that the Gibson and Schwartz (1990 a,b) reserve value estimates dominate other reserve values. In line with previous research, the Rotelling reserve value estimate was found to be insignificant in regressions which contained other reserve value estimates. In general, our results suggest that on average stock market investors tend to be more risk averse than derivatives market investors. However, it should be borne in mind that the discrimination among the reserve value measures were based on ad hoc stepped up regressions using simple F-tests to determine the relative explanatory power among the reserve variables. Each reserve value estimate alone explained variation in market prices well. We also present simple trading strategies in the attempt to profit from apparent deviations of market prices and underlying net asset values. However, none of the trading strategies was successful in creating consistent profits. As the valuation results which are suggesting significant per company over- and under valuations imply that the market for oil and gas reserves is inefficient, future research should relax some of the simplifying assumptions made in the company valuation framework such as the omission of tax issues, the simple 1:6 conversion of gas into oil reserves and omission of potential option values arising from unproven reserves, and address the requirement for further compulsory disclosure of reserve and price data as outlined in the text. The variance analysis of market prices and underlying net asset values along the lines of Pontiff (1997) also suggests considerable inefficiency in the market for oil and gas firms.
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Watson, Paula. "Feasibility evaluation and long-term follow up of a family-based behaviour change intervention for overweight children (GOALS)." Thesis, Liverpool John Moores University, 2012. http://researchonline.ljmu.ac.uk/6116/.
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Childhood obesity is the most serious public health challenge of the 21st century. Whilst evidence supports a family-based lifestyle approach to childhood obesity treatment, research is needed to understand how interventions work and how practitioners can effectively support families to sustain behavioural changes in the long-term. This thesis evaluated the feasibility of a family-based behaviour change intervention for overweight children (GOALS) and explored the psychosocial process of long-term behavioural change in families with overweight children. Study 1 measured the impact of GOALS on the body composition, lifestyle behaviours and self-perceptions of children and parents who completed the intervention. A complete case analysis (n=70) showed a significant 6-month reduction in child BMI SOS (-0.07, p < 0.001) that was maintained at 12-month follow up. There was a significant year-on-year increase in the proportion of children reducing BMI SOS (42.9% year 1, 62.5% year 2, 80% year 3, p < 0.05) and a strong positive relationship between parent and child BMI change (r = .479, p < 0.001). Parents reported positive changes to their own and their children's physical activity and diet. BMI SOS reduction during the intervention was associated with improved global self-esteem and perceived physical appearance at 12 months. Study 2 explored the experiences of families six weeks into the 18-session intervention through focus groups with parents and children. Motivators to attend GOALS included the non-judgemental approach, being in the same boat as others and child enjoyment. The whole family approach was perceived positively and families used BCTs both as a core component of GOALS and to facilitate their behaviour change at home. As well as the challenges of living with childhood overweight, families described a lack of support from extended family members and a perceived need for on-going professional support. Study 3 followed up 15 families 3-5 years after they attended GOALS. Child and parent BMI was collected and parents took part in a semi-structured interview to explore their perceptions of "success" and their experiences of changing physical activity and eating behaviours. Mean child BMI SOS change from baseline was -0.47 for the 14 families who had completed GOALS. The majority of families perceived positive long-term outcomes, but these were not always aligned with actual child weight change. The most "successful" families placed a priority on changing child weight-related behaviours and parents took responsibility for these changes. While weight-control was a conscious process for these families, it was not necessarily made a "big issue" and parents used practices of an authoritative nature to facilitate change. Physical activity had become a way of life for the children, and mothers had reached a stage of feeling in control of their own weight. This is the first UK childhood obesity treatment study to follow children up beyond 12 months, and the first known study worldwide to employ qualitative methods to explore parental perceptions of long-term success. Findings provided a unique insight into the process of long-term behavioural change for overweight children and raised questions about the way "success" is defined following participation in childhood obesity treatment. Recommendations are made to enhance the delivery of family-based childhood obesity treatment and policy-makers are urged to adopt a multilevel approach to tackling childhood obesity, with child weight management care pathways that recognise the heterogeneity of familial needs. Further research is required to substantiate the impact of GOALS, and to prospectively explore the process of behavioural change in overweight children and the familial factors that serve as moderators in this process.
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Brändström, Magnus, and Tejero Albert Dueso. "How to encourage stretching and breaks at work : Understanding long term usage of a behaviour change support system." Thesis, Umeå universitet, Institutionen för informatik, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-89949.
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We are spending more and more time seated at work, which increases the risk for health problems. Behaviour change support systems that encourage breaks and stretching at work have been used as interventions to try to reduce these problems. No previous studies had looked at how these systems were used for long periods of time. In this qualitative study based on ten interviews, we aimed for expanding our understanding of long-term usage of such systems by studying one called ‘Efons’. The results indicate that the main factors influencing long-term usage are timely reminders, the impact that the stretching exercises has on the users’ health and the education of the user about health recommendations. We also found elements we argue have the ability to influence long-term usage and currently do not exist in the system studied or its context of use, such as adapt the system to the needs of the user or provide education about why these systems are useful.
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Dawes, Les A. "Role of soil physical and chemical characteristics and landscape factors in defining soil behaviour under long term wastewater dispersal." Queensland University of Technology, 2006. http://eprints.qut.edu.au/16297/.
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The use of on-site wastewater treatment systems for the treatment and dispersal of domestic effluent is common in urban fringe areas which are not serviced by centralised wastewater collection systems. However, due to inappropriate siting and inadequate evaluation of soil characteristics, the failure of these systems has become a common scenario. The current standards and guidelines adopted by many local authorities for assessing suitable site and soil conditions for on-site dispersal areas are coming under increasing scrutiny due to the public health and environmental impacts caused by poorly performing systems, in particular septic tank-soil adsorption systems. In order to achieve sustainable on-site wastewater treatment with minimal impacts on the environment and public health, more appropriate means of assessment of long term performance of on-site dispersal areas are required.
The research described in the thesis details the investigations undertaken for the development of robust assessment criteria for on-site dispersal area siting and design and assessment of the long term performance of soil dispersal areas. The research undertaken focused on three key research areas; (i) assessment of site and soil suitability for providing adequate treatment and dispersal of domestic wastewater; (ii) understanding sorption, purification and transport processes influencing retention and release of pollutants and the natural controls governing these processes and (iii) the development of assessment criteria for long term behaviour of soils under effluent dispersal.
The research conducted was multidisciplinary in nature, with detailed investigations of the physical and chemical processes involved in on-site wastewater treatment and dispersal. This involved extensive field investigations, sampling and monitoring, laboratory and soil column testing and detailed data analysis across the fields of soil science, groundwater quality, subsurface hydrology, chemical contamination, and contaminant fate and transport processes. The interactions between these different disciplines can be complex which resulted in substantial amounts of data being generated from the numerous field and laboratory investigations and sampling undertaken. In order to understand the complex relationships that can occur, multivariate statistical techniques were utilised. The use of these techniques was extremely beneficial. These techniques not only allowed not only the respective relationships between investigated parameters to be identified, but also adequate decisions based on the correlations were able to be formulated. This allowed a more appropriate assessment of the influential factors, and the prediction of ongoing changes to soil properties due to effluent disposal.
The primary outcomes for this research were disseminated through a series of peer reviewed scientific papers centred on these key disciplines. The assessment of site and soil suitability was achieved through extensive soil sampling throughout the study areas and detailed laboratory testing and data analysis. The study identified and investigated the role of influential site and soil characteristics in the treatment performance of subsurface effluent dispersal areas. The extent of effluent travel and the ability of the soil to remove pollutants contained in the effluent by adsorption and/or nutrient uptake were investigated. A framework for assessing the renovation ability of the major soil groups located throughout Southeast Queensland was also developed. The outcomes provide a more rigorous scientific basis for assessing the ability of soil and evaluating site factors to develop more reliable methods for siting effluent dispersal areas. The resulting assessment criteria developed was compared with soil column studies to determine the robustness and validity of the outcomes. This allowed refinement of the assessment criteria in developing a more reliable approach to predicting long term behaviour of soils under sewage effluent dispersal. Multivariate techniques assisted in characterising appropriate soils and to determine their long-term suitability for effluent treatment and dispersal.
The assessment criteria developed included physical, chemical and sub-surface hydrological properties of a site and soil which can be used to predict suitability for long term effluent treatment and dispersal. These include:
Moderate to slow drainage (permeability) to assist the movement of effluent (percolation) through the soil profile and allow adequate time for treatment and dispersal to occur. With longer percolation times, the opportunity for exchange and transport processes increase.
Significant soil cation exchange capacity and dominance of exchangeable Ca2+ or exchangeable Mg2+ over exchangeable Na+. Although a soil dominated by Mg2+ is found to promote dispersion of soil particles to some extent, its impact is far less than that of Na+. A stable soil would have a Ca: Mg ratio > 0.5.
Low exchangeable Na+ content to maintain soil stability.
Minimum depth of 400mm of potentially unsaturated soil before encountering a restrictive horizon, to permit adequate purification to take place.
Clay type with Illite and mixed mineralogy soils being the most sensitive to Na+. In general, significant increases in ESP occur in soils with 30 to 40% clay and in the presence of illite clay. Small amounts of smectite clays enhance treatment potential of a soil.
The research outcomes have significantly contributed to the knowledge base on best practice in on-site dispersal area siting and design. The developed predictive site and soil suitability assessment criteria allows more appropriate evaluation of site and soil characteristics for providing long term effluent renovation. This is generally not done in the current assessment techniques for on-site dispersal areas. The processes and techniques used in the site and soil suitability assessment, although based on the common soil types typical of South East Queensland, can be implemented in other regions, provided appropriate soil information is collected or available.
The predictive assessment criteria have been developed at a generic level, allowing easy implementation into most assessment processes. This gives the framework the flexibility to be developed for other areas specifically targeting the most influential on-site dispersal area siting and design factors, and assessment of long term performance under wastewater application.
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Sanders, Gordon. "Long-term temporal trends of PCBs and PAHs in the environment and their fate and behaviour in lacustrine systems." Thesis, Lancaster University, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.385671.
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Yeoh, David Eng Chuan. "Behaviour and Design of Timber-Concrete Composite Floor System." Thesis, University of Canterbury. Department of Civil and Natural Resources, 2010. http://hdl.handle.net/10092/4428.
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This Ph.D. thesis represents a summative report detailing research processes and outcomes from investigating the ultimate and serviceability limit state short- and long-term behaviour and design of timber-concrete composite floors. The project enables the realization of a semi-prefabricated LVL-concrete composite floor system of up to 15 m long using 3 types of connection. Design span tables which satisfy the ultimate and serviceability limit state short- and long-term verifications for this system form the novel contribution of this thesis.
In quantifying the behaviour of timber-concrete composite floors, 5 different experimental phases have been carried. 9 major achievements in meeting 9 sub-objectives have been concluded:
1) Three best types of connection system for timber-concrete composite floors have been identified;
2) The characteristic strength and secant slip moduli for these connections have been determined;
3) The short-term behaviour of the selected connections defined by their pre- and post-peak responses under collapse load has been established;
4) An analytical model for the strength evaluation of the selected connections based on the different possible modes of failure has been derived;
5) Easy and fast erected semi-prefabricated timber-concrete composite floor has been proposed;
6) The short-term ultimate and serviceability limit state behaviour of timber-concrete composite floor beams under collapse load has been investigated;
7) The long-term behaviour of chosen connections defined by their creep coefficient has been determined;
8) The long-term behaviour of timber-concrete composite floor beams under sustained load at serviceability limit state condition has been investigated; and
9) Design example and span tables for semi-prefabricated timber-concrete composite floors that satisfy both the ultimate and serviceability limit state in the short- and long-term using the gamma-method have been developed.
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Cuéllar, Pablo [Verfasser], and Stavros [Akademischer Betreuer] Savidis. "Pile foundations for offshore wind turbines: Numerical and experimental investigations on the behaviour under short-term and long-term cyclic loading / Pablo Cuéllar. Betreuer: Stavros Savidis." Berlin : Universitätsbibliothek der Technischen Universität Berlin, 2011. http://d-nb.info/1014619521/34.
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Johansson, Sara, and Victoria Jörheim. "Långtidsbeteende hos förband i KL-trä." Thesis, Linnéuniversitetet, Institutionen för byggteknik (BY), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-97125.
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Intresset för användning av KL-trä som byggnadsmaterial har ökat kraftigt sedan tekniken introducerades i Sverige under 1990-talet. Med ökande användning av KL-trä i konstruktioner finns behov av att undersöka hur materialet beter sig under längre tid. Förband är generellt sett en svag punkt i en konstruktion, och det är därför viktigt att närmare undersöka långtidsbeteendet hos förband i KL-trä. Syftet med arbetet är att utveckla metoder som kan användas för att ge större insikt i hur effekterna av belastning under lång tid påverkar konstruktioner i KL-trä. I den här studien undersöks vilka tidigare utförda studier som behandlat långtidsbeteende hos trä i allmänhet och hos KL-trä i synnerhet. Utifrån dessa studier har två förslag på testmetoder tagits fram: ett test för förband utsatt i skjuvning, och ett utdragstest.The interest for the use of CLT as a building material has increased dramatically since the technology was first introduced in Sweden during the 1990s. With increasing use of CLT in constructions there is a need to investigate the material’s long-term behaviour. Connections are generally a weak point in a construction, and it is therefore important to investigate the long-term behaviour of connections in CLT. The purpose of this project is to develop methods that can be used to provide greater insight into how the effects of long-term loading affect the behaviour of CLT designs. This study examines previously conducted studies involving long-term behaviour of wood in general and CLT in particular. Following this investigation, two proposals of test set-ups have been developed: one test for joints subjected to loading in shear, and one withdrawal test.
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Williams, J. H. "An investigation of long-term pro-active non-associative mechanisms by which theta-driving sepatal stimulation alters behaviour in rats." Thesis, University of Oxford, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.382700.
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Wang, Qiong. "Hydro-mechanical behaviour of bentonite-based materials used for high-level radioactive waste disposal." Phd thesis, Université Paris-Est, 2012. http://pastel.archives-ouvertes.fr/pastel-00806392.
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This study deals with the hydro-mechanical behaviour of compacted bentonite-based materials used as sealing materials in high-level radioactive waste repositories. The pure MX80 bentontie, mixtures of MX80/crushed claystone and MX80/sand were used in the investigation. An experimental study on the swelling pressure of the bentonite-based materials was first performed. The results evidenced the effects of water chemistry, hydration procedure and duration, pre-existing technological void and experimental methods. Emphasis was put on the relationship between the swelling pressure and the final dry density of bentonite. Afterwards, the water retention test, hydration test and suction controlled oedometer test were conducted on samples with different voids including the technological void and the void inside the soil. By introducing the parameters as bentonite void ratio and water volume ratio, an overall analysis of the effects of voids on the hydro-mechanical response of the compacted material was performed. To get better insight into the seal evolution in case of technological void, the effects of final dry density and hydration time on the microstructure features were also characterized. Then, the hydraulic properties under unsaturated state were investigated by carrying out water retention test and infiltration test as well as the microstructure observation. The results obtained allowed relating the variation of hydraulic conductivity to the microstructure changes. A small scale (1/10) mock up test of the SEALEX in situ experiment was also performed to study the recovery capacity of bentonite-based material with consideration of a technological void. The results were used for interpreting the in-situ observations. With a reduced time scale, it provides useful information for estimating the saturation duration and sealing effectiveness of the field design. Finally, the experimental data obtained in the laboratory on bentonite/sand mixture were interpreted in the framework of the Barcelona Expansive Model (BExM). By comparing the model with the experimental results, the performance and limitation of the model were analyzed
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Brännlund, Annica. "Non-market outcomes of education : the long-term impact of education on individuals' social participation and health in Sweden." Doctoral thesis, Umeå universitet, Sociologiska institutionen, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-88369.
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In research, it is typical to analyse and discuss the utility of education in economic terms—specifically the market value of a particular degree or the financial returns associated with additional years in higher education. However, education may also generate outcomes that belong to the non-market sphere, such as open-mindedness, societal cohesion, community involvement, better health, and gender equality; yet these outcomes have received little scholarly attention. The main objective of this thesis, therefore, is to investigate the relationship between education and four non-market outcomes: agency, voice, health behaviour and psychological distress. By utilizing two longitudinal data sets, the Swedish Survey of Living Conditions and the Northern Swedish Cohort, it is possible to assess the long-term effects of education on each of these four non-market outcomes. Results clearly demonstrate that education has a critical impact on each of the outcomes of interest. Having a higher education—and in particular a university degree–enhances individuals’ agency and voice, reduces psychological distress, and improves individuals’ health behaviour. Further, results show that different academic subjects generate field-specific resources. In contrast to a market perspective, where the value of the specific field of study is assessed only in economic terms, results indicate that fields that are commonly viewed as having low market value may actually yield non-economic rewards that benefit individuals in critically important ways. Analyses also show that individual and social factors shape the extent to which education leads to positive outcomes. In terms of agency and voice, results indicate that education can compensate for social differences. Among those with a working class background, earning a university degree contributes to increasing levels of agency and voice, while no significant effects of education exist for those with a white-collar background. Results also demonstrate that the impact of education on psychological well-being differs for men and women. For men, labour market resources (i.e., being employed) was important for reducing psychological distress, while for women social resources (i.e., having a partner) was more important. Due to its use of high quality, longitudinal data, this thesis makes a significant contribution to the scholarly literature and to what we know about the impact of education attainment. A limitation of cross-sectional analyses is that it is difficult to separate causal effects from selection effects. By adopting a longitudinal approach, it is possible to control for earlier (baseline) circumstances and therefore assess the causal impact of education on individual outcomes. This strategy yields robust results that make clear the long-term effects of educational attainment on individuals.
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Saiedi, Mohammad Reza. "Behaviour of CFRP-Prestressed Concrete Beams under Sustained Loading and High-Cycle Fatigue at Low Temperature." Thesis, Kingston, Ont. : [s.n.], 2009. http://hdl.handle.net/1974/5365.
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Christ, Kaaren R. "Children with problematic sexual behaviour in long term foster care : a review of attachment difficulties within care giving relationships and placement instability." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=99560.
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The purpose of this theoretical study was to examine factors associated with the development of attachment relationships for children in long term foster care who Overt demonstrating problematic sexual behaviour. Due to the dearth in available research on this topic, it was necessary to draw from studies in three distinct areas (1) Attachment, (2) Childhood Sexuality, and (3) Placement Stability. In total, the present study examines 13 studies drawn from these three areas, and includes 11 quantitative and 2 mixed method studies.These studies were chosen for their attention to the middle age child in foster care who was demonstrating problematic sexual behaviour. Due to the lack of attachment studies on fostered middle age children, two infant studies were included with the rationale that middle age children and foster parents engage in a similar attachment process and infant studies would provide direction and context for future studies with older children. In the area of childhood sexuality, clinical samples were also included as they contained large numbers of children who had experienced sexual abuse or who had contact with child protection agencies even if they did not reside in foster care.
Studies were examined along dimensions of sample, methods and findings. The results of this inquiry are then discussed, weaving together the three areas of study to answer two research questions: Is there a relationship between problematic childhood sexual behaviour and the development of a successful attachment relationship with a foster parent? And secondly, is there a particular foster parent attachment profile that promotes attachment security with children who are in care?
Studies reviewed support the hypothesis that problematic childhood sexual behaviour presents challenges to foster parents significant enough to seriously impair the development of a secure attachment and that the foster parent's attachment state of mind will be an important factor in success. Results of the analysis of these questions contribute to an emerging hypothesis that the human sexual system may be intricately woven together with the attachment system, making an attachment analysis of problematic sexual behaviour in children particular relevant. A concluding discussion examines clinical issues which may be targets of intervention and the necessity of future research in this area is proposed.