A haute fréquence ultrasonore (HF), de 30 à 50 Mhz, la préparation de revêtements épais (20 à 40 um) offrant de bonnes propriétés piézoélectriques constitue un enjeu technologique majeur pour la réalisation de sondes echographiques performantes. Cette étude explore le procécé sol-gel composite pour l'élaboration de films piézoélectriques épais de PbZr0,52Ti0,48O3 (PZT). De la synthèse des solutions composites à l'intégration des films dans une sonde, chaque étape du procédé est étudiée pour répondre au cahier des charges : performance piézoélectrique, focalisation et haute fréquence ultrasonore. Ce travail a permis d'établir un protocole de préparation des films avec des coefficients ultramagnétiques (kt) supérieurs à 40%. Ces résultats prometteurs ont permis de réaliser deux prototypes de transducteurs mono et multiéléments (barrette). Ceux-ci présentent des performances électroaccoustiques élevées, et montrent la pertinence de ce procédé pour la fabrication de transducteurs ultrasonores HF. / At high ultrasonic frequency (HF), from 30 to 50 Mhz, good piezoelectric films in the 0-40 um thickness range have to be prepared to build high performing probes. This study explores the sol-gel composite process to develop piezoelectric thick films of PbZr0,52Ti0,48O3 (PZT). From solutions synthesis to film in probes integration, each step of the process is studied to respect specification : piezoelectric performance focusing and high frequency. Composites films with effective coupling coefficient (Kt) above 40% have been here obtained. These promising results allowed the fabrication two types of transducter : a single element and a 128 element linear array. These transducters working at 20 and 30 MHz have both high electro accoustical performances, and definitively show that this composite sol-gel process is of interest for the high frequency ultrasonic transducer fabrication.

Investigation of infiltration provides insights about the flow of water and transport of contaminants through the vadose zone. Infiltration is governed by prevailing environmental conditions like soil characteristics, plant cover and geologic settings. The main objective was to study preferential flow dominated infiltration at two contrasting hydrologic settings in Texas. For the first study, artificial rainfall was simulated within a plot covered with juniper trees at a karst region of the Edwards Plateau and sub-surface flow was monitored using TDR probes. Sub-surface flow was simulated using HYDRUS-2D. Results demonstrated that sub-surface flow occurred in a tri-modal manner, consisting of flow in karst conduits, planar fractures in the limestone, and soil matrix. Both fracture and matrix flow responses increased with increase in rainfall intensity. During large rainfall events, water exchange was observed between the fractures and matrix. Dye studies indicated that fractures and juniper roots were primary pathways for preferential flow occurring within the plot. The model simulated flow characteristics like exchange processes and differentiated between preferential and conduit flow besides determining approximate van Genuchten parameters for each geologic unit.For the second study, tension infiltrometers were used to conduct infiltration experiments at six soil water pressures (?? = -0.2 to 0 m) in an agricultural field near College Station over a 21 month period. The aim was to determine steady infiltration rate, if, saturated hydraulic conductivity, Ksat, unsaturated hydraulic conductivity, K(??) and unsaturated flux density ??(??). Moreover, the effect of varying disc diameters on steady state infiltration rates (if) was also studied. Results demonstrated that infiltration occurred in a bi-modal fashion consisting of preferential flow and matrix flow. Macropores and roots present in the soil resulted in gravity dominated flow at ?? = -0.05 to 0 m for all experiments. Statistical analysis suggested that the soil did not exhibit spatial variability within the plot and the five different disc diameters had no effect on if. Statistically significant differences in if were observed between 0.2 and 0.24 m disc diameters at saturation over the 21 month period. The if values illustrated strong temporal variations based on natural conditions over the 21 month period.

Investigation of infiltration provides insights about the flow of water and transport of contaminants through the vadose zone. Infiltration is governed by prevailing environmental conditions like soil characteristics, plant cover and geologic settings. The main objective was to study preferential flow dominated infiltration at two contrasting hydrologic settings in Texas. For the first study, artificial rainfall was simulated within a plot covered with juniper trees at a karst region of the Edwards Plateau and sub-surface flow was monitored using TDR probes. Sub-surface flow was simulated using HYDRUS-2D. Results demonstrated that sub-surface flow occurred in a tri-modal manner, consisting of flow in karst conduits, planar fractures in the limestone, and soil matrix. Both fracture and matrix flow responses increased with increase in rainfall intensity. During large rainfall events, water exchange was observed between the fractures and matrix. Dye studies indicated that fractures and juniper roots were primary pathways for preferential flow occurring within the plot. The model simulated flow characteristics like exchange processes and differentiated between preferential and conduit flow besides determining approximate van Genuchten parameters for each geologic unit.For the second study, tension infiltrometers were used to conduct infiltration experiments at six soil water pressures (?? = -0.2 to 0 m) in an agricultural field near College Station over a 21 month period. The aim was to determine steady infiltration rate, if, saturated hydraulic conductivity, Ksat, unsaturated hydraulic conductivity, K(??) and unsaturated flux density ??(??). Moreover, the effect of varying disc diameters on steady state infiltration rates (if) was also studied. Results demonstrated that infiltration occurred in a bi-modal fashion consisting of preferential flow and matrix flow. Macropores and roots present in the soil resulted in gravity dominated flow at ?? = -0.05 to 0 m for all experiments. Statistical analysis suggested that the soil did not exhibit spatial variability within the plot and the five different disc diameters had no effect on if. Statistically significant differences in if were observed between 0.2 and 0.24 m disc diameters at saturation over the 21 month period. The if values illustrated strong temporal variations based on natural conditions over the 21 month period.

[Abstract]: Infiltration variability is a major issue during the design phase and management for all types of irrigation systems. Infiltration is of particular significance for furrow irrigation and other forms of surface irrigation as the soil intake rate at any given position not only determines the depth applied but also governs the distribution of water to other locations in the field. Despite this, existing measurement and evaluationprocedures generally assume homogeneous soil infiltration rates across the field to simplify data collection and computational requirements. This study was conducted to(a) determine whether spatial and temporal variations in soil infiltration characteristics have a significant impact on the performance of surface irrigation and (b) identify more appropriate management strategies that account for this variability and substantially improve irrigation performance.The soil infiltration rate is typically expressed as an empirical function of opportunity time. The infiltration function parameters cannot be directly measured but are commonly estimated from field hydraulic measurements using an appropriate simulation model. The volume balance model as used in the inverse solution for infiltration (e.g. Two Point Method) was modified to enable runoff data collected during the inflow period to be used in the estimation of the infiltration parameters. The resulting model, IPARM also accommodates the full (variable) inflowhydrograph rather than relying on a constant inflow assumption. Inclusion of runoff data in the inverse solution improved the accuracy of the infiltration curve during the runoff phase and hence offered the greatest benefit where the irrigation time exceededthe completion of advance. Analysis of field data collected from multiple furrows at a single site indicated that accounting for the variable inflow in IPARM both reduced the variability (e.g. reduction in the coefficient of variance (CV) of cumulative infiltrated depths of 18.6% and 11.5% at opportunity times of 100 and 500 minutes,respectively) and standardised the shape of the estimated infiltration curves. Hence, a significant proportion of the apparent variability in soil infiltration rates was shown to be a consequence of the constant inflow assumption. Sensitivity analysis indicatedthat IPARM is highly sensitive to the runoff measurements but is not influenced by the relative numbers of advance and runoff data points. Validation of IPARM estimated infiltration parameters using the full hydrodynamic model SIRMOD showed that the inclusion of runoff data in the inverse procedure did not compromise the ability to predict the measured advance trajectory but significantly improved the fit to the measured runoff volumes (average decrease in absolute error of simulated runoff volumes of 84%). Whereas the use of runoff data enabled SIRMOD to estimate runoff volumes, accounting for variable inflow improved the fit of the predicted runoff rates to the shape of the measured outflow hydrograph.Field data collected from several sites across the Darling Downs, Queensland has shown that the infiltration rates vary significantly (e.g. by up to 65% at 500 minutes),both spatially between furrows and temporally over the season. For the sites studied, the spatial variance in infiltration was surpassed by the seasonal variance (e.g. average CV of infiltration of 33.1% compared to 12.5%) but no consistent trends were identified. It was found that the lognormal distribution provided the best fit for thevariance in the infiltration curves which was in turn strongly related to the statistical distribution of the infiltration term of the volume balance. From this research, a procedure was developed to predict the infiltration parameters using a single advancepoint and any number of “known” infiltration curves from the same field.The IrriProb model was developed to extend the process of simulation from a single furrow scale to the whole field scale. IrriProb performs the full hydrodynamicsimulation for multiple independent furrows which are combined to form a spatial representation of the water application. Each furrow can have a unique infiltrationrate, inflow rate (Q), time to cut off (TCO) and soil moisture deficit. Validation of IrriProb using multiple sets of field data demonstrated that the single furrowsimulations failed to predict the true whole field irrigation performance (e.g. furrow distribution uniformity (DU) between 72.2% and 86.2% compared to the whole field DU of 64.8%).An optimisation routine was developed within IrriProb to maximise irrigation performance through identification of optimal values of Q and TCO. The optimisation objective function is comprised of a Boolean combination of customisable performance criteria. The user selects the appropriate performance terms and the optimal management is determined through a graphical overlay of the complyingranges of Q and TCO. Hence, the objective function of IrriProb retains the importance of each individual performance term, an advantage over those based on numerical combinations of weighted terms. Simulation of the whole field application under practical ranges of Q and TCO demonstrated the complex interactions between theperformance indices (e.g. the trade off between requirement efficiency (RE) and application efficiency (AE)). In cases of low infiltration variability it was possible to optimise the whole field performance using a single value of Q and TCO. However, under increased infiltration variability it was more appropriate to manage the field using two or more different management strategies. Irrigation optimisation based onmeasurements from a single furrow or the average infiltration curve, cannot identify the optimal combination of Q and TCO for the whole field. Simulation of field management based on the optimisation strategy obtained from single furrow measurements results in lower whole field performance than estimated from simulation of the single furrow data (e.g. field RE, AE and distribution uniformity of the root zone up to 26%, 18% and 66% lower than predicted). Field trials were used to demonstrate the ability to estimate whole field infiltration variability, evaluate whole field irrigation performance and optimise whole field irrigation management while taking into account the influence of spatial variability.

Forest fires have an enormous impact on biotic and abiotic variables that control runoff and soil properties in watersheds. Because wildfires do not have a uniform effect on the burned area, significant variability occurs between areas of different burn severity and likely elicits different hydrologic responses within watersheds. Much of the control on this hydrologic response stems from the variability of soil between burned and unburned watersheds. Establishing a linkage between soil infiltration and burn severity may therefore, offer insight into the likelihood of elevated levels of runoff and the likelihood of floods. Although previous studies have sought to establish a quantitative relationship between runoff and burn severity, this relation has not been evaluated with respect to soil moisture and infiltration and varying degrees of burn severity. The Loretta-Linda Basin presents a unique opportunity to compare areas with different burn severities (with the right fork of the drainage experiencing a much higher burn severity than the left), while eliminating most other variables that may occur with greater spatial variability such as elevation, temperature, precipitation, underlying geology, and soil type. Rainfall, soil moisture, runoff, and infiltration data collected over a two-month period were used to evaluate the relationship between burn severity, runoff, and infiltration for the Loretta-Linda basin as a whole as well as for the individual forks of the basin. The impact of varying burn severity on the two sub drainages was further investigated by creating a dynamic simulation model in TopoFlow®. Comparative analysis between the two forks did not show a dramatic difference in the runoff and infiltration relationship between the two burn severities. Variability of field conditions, the presence of parameters affecting runoff not accounted for, and the limitations of point measurements, are reflected by the data analysis and lack of a strong correlation between burn severity, infiltration, and runoff. The use of spatial hydrologic modeling allowed for the investigation of the relative importance of the infiltration parameters as well as the impact of Manning’s n on the response of the basin to rainfall. The modeling results indicate a strong correlation between high burn severity, low infiltration capacity, and elevated discharge volumes.

Th. 3e cycle--Sc. nat.--Paris VII, 1981. / Bibliogr. p. 176-209 et p. 218-221. Résumé en français et en anglais.

Water resources development around the world has taken many different forms and directions since the dawn of civilization. Water shortage in arid and semiarid regions has encouraged the search for additional sources currently not exploited intensively. Hence, knowledge of the infiltration process is a requirement for understanding water management. The main aim here is to solve the one-dimensional nonlinear time-dependent Richard's equation for water flow in an unsaturated uniform soil. The main theory of soil infiltration is introduced using a mathematical-physical approach to describe water movement in unsaturated soils. This gives rise to Richard's flow equation; which is presented for both unsaturated and also saturated soil. Methods for solving Richard's equation by both analytical and numerical techniques are then introduced. This gives rise to a discussion of the similarity methods first used by Philip to determine analytical solutions of Richard's equation in an unsaturated soil. This is then generalised to determine a broader class of solutions using the Lie (classical) symmetry approach. The non-classical symmetries of Bluman and Cole are also determined. Although these group methods provide the most widely applicable technique to find solutions of ordinary and partial differential equations, a large number of tedious calculations are involved. With the help of computer algebra it is shown that the determining equations for the non-classical case lead to four new highly non-linear equations which are solved in five particular cases. Each case of classical and non-classical solutions is then reduced to an ordinary differential equation and explicit solutions are produced when possible. The potential classical and non-classical method, first suggested by Bluman, Reid and Kumei, is also discussed and presented. The potential non-classical method produced new results, which the potential classical method did not. The solution is useful as a tool by which to judge the quality of numerical methods. A practical solution of classical (Lie/ potential) and non-classical symmetry of Richard's equation is presented. Finally, conclusions and suggestions for further work are discussed.

As part of the effort to satisfy the ever increasing demand for a greater understanding of fluvial, hydrological, chemical, sedimentological and geomorphological processes operating on the floodplain, mathematical simulation models have come to play a significant role in the understanding, prediction and management of the floodplain environment. Underlying the accurate numerical representation of hydraulically driven processes is the provision of a suitable floodplain hydrology model which accounts for the interaction between surface hydraulics and subsurface hydrology. Such a numerical representation is currently not available at the spatial and temporal resolution required. It is the aim of this thesis to develop a novel conceptual approach to modelling floodplain hydrology in which the fundamental need to consider the interaction between surface and subsurface flow is the floodplain environment is addressed. This is achieved through the interactive coupling of a one-dimensional finite difference infiltration model with the state-of-the-art two-dimensional physically based finite element hydraulic model, TELEMAC2D. The coupled model provides an unparalleled spatial and temporal representation of surface and subsurface flow processes within the floodplain environment. The utility of this integrated approach is explored through an application of the model to two areas of contemporary floodplain research. In the first of these the model is run to assess the impact of infiltration on flood flow prediction for an llkm reach of the River Culm, UK, over a range of flood and soil conditions. In the second the model is run to investigate the nitrate buffering potential of floodplain riparian soils during flooding. For this investigation a model accounting for nitrate transport and denitrification is developed within the existing integrated hydraulic-infiltration model structure. An evaluation of the results from both of these investigations supports the need for a new approach to modelling fluvially driven floodplain processes which accounts for the spatially interactive nature of floodplain hydrology.

If an expensive part such a turbine blade or high quality tool needed to be refurbished instead of discarded, the part would have be coated in a way that would resemble or even exceed its previous surface properties. In this regard, this work studies a tungsten carbide-nickel braze alloy hardface composite prepared by liquid infiltration. A unique polymeric binder system was used to form the brazing cloth which formed the carrier for the tungsten carbide and nickel braze alloy particles. After thermal pyrolysis of the binder, the nickel braze alloy would infiltrate into a porous tungsten carbide layer becoming a hard surface coating or hardfacing. These brazing cloths were formulated to achieve a theoretical full density coating after the infiltration process. The hardface would also be brazed to its base substrate. In this study, infiltration of a porous material and brazing are mated in one continuous process. The goal of this research is the measure of hardfacing in relations to powder-polymer processing, infiltration of porous materials and brazing cycles to achieve superior hardness and braze interface quality.

L’endométriose est définie comme la présence de tissu endométrial et de stroma en dehors de la cavité utérine. Ses localisations les plus fréquentes sont le péritoine pelvien et les ovaires. L’endométriose infiltrante est classiquement décrite comme la présence de tissu endométriotique plus de cinq millimètres sous le péritoine pelvien ou la séreuse d’un organe. Histologiquement il s’agit d’une lésion endométriotique mais qui contrairement aux lésions ovariennes ou péritonéales contient significativement plus de muscle lisse et de fibrose et est davantage associée à la douleur. Les lésions infiltrantes peuvent être responsables de dysménorrhée, dyspareunie profonde et douleurs pelviennes chroniques sévères ayant un charactère hyperalgique tel qu’on peut le retrouver dans les douleurs neuropathiques. Ces douleurs nécessitent souvent la prise de quantités importantes d’antalgiques et ont des répercussions importantes sur la vie professionnelle, quotidienne et sexuelle des femmes atteintes. L’endométriose infiltrante présente un rapport histologique étroit avec les structures nerveuses du rétropéritoine ou les nerfs des organes atteints. Dans sa localisation rectovaginale il existe une relation histologique étroite entre les lésions d’endométriose et les nerfs ainsi qu’une correlation entre l’intensité de la douleur et le nombre de structures nerveuses envahies par l’endometriose ou engaînées dans la fibrose. Ces lésions infiltrantes expriment le «nerve growth factor» (NGF), une neurotrophine qui joue un rôle clé dans la genèse de l’hyperalgie et de la douleur. Les structures nerveuses du rétropéritoine pelvien expriment quant à elles le récepteur spécifique pour la neurotrophine NGF. Le système «NGF-récepteur spécifique» peut être responsable d’un chimiotactisme tissulaire entre les tissus sécrétant du NGF et les nerfs qui expriment le récepteur pour le NGF. Le système «NGF- récepteur spécifique» au sein de la relation endométriose-nerfs pourrait rendre compte du caractère hyperalgique des lésions endométriotiques infiltrantes ainsi, qu’expliquer pourquoi les lésions nodulaires n’apparaissent que dans les sites anatomiques richement innervés (ligaments utérosacrés, lame rectovaginale, paroi du rectum ou du côlon…) et pas ailleurs. Le traitement de première intention est chirurgical. Il convient d’être suffisamment agressif sur les lésions tout en engendrant le moins de séquelles postopératoires possibles sachant que nombre de ces femmes sont stériles. En cas d’atteinte digestive basse, les modalités de l’intervention sont dictées par l’extension et le degré d’infiltration de la paroi digestive. Dans le but de réaliser dans la majorité des cas une chirurgie minimalement invasive (laparoscopique) avec des cicatrices de petites tailles, nous avons développé une stratégie de traitement basée sur le degré d’infiltration de la paroi digestive. Dans ce cadre nous avons développé une technique laparo-assistée de résection colique segmentaire et de résection antérieure du rectum.