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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
21

Sustainable drainage of sports pitches

Simpson, Murray R. January 2016 (has links)
The drainage behaviour of sports pitches is not well understood nor has performance been measured in the past. Within planning authorities there is a perceived contribution of pitch water discharge to local flood risk; whereby all the rainfall surface runoff is rapidly channelled through the drainage system to the pitch outfall. However, empirical evidence from industry suggested that this may not be a realistic assumption from observations of low drainage volumes yielded from pitch drainage systems. Furthermore, discharge constraints imposed have in many cases resulted in grossly over-designed off-line drainage attenuation systems for new sports developments through lack of understanding. In contrast, sports pitches indeed have the potential to enhance the attenuation performance of the subsoils and provide localised effective management of surface water runoff, and a significant storage volume if designed appropriately The findings in this thesis confirm that pitch bases demonstrate the key functions that are in fact reflected in the design requirements of Sustainable Urban Drainage Systems (SuDS). This PhD research project was conducted to investigate and document the performance of common pitch construction and drainage systems to better characterise the key drainage mechanisms that occur and control the flow of surface rain water through the pitch to the discharge outfall. The project developed a triangulated approach to the investigations, comprising: field measurements of climate and discharge behaviour at a range of artificial and natural turf pitches in England; laboratory physical model testing of pitch component hydraulics; and predictive mathematical modelling of how a pitch system may be expected to perform hydraulically based on key material and system drainage principles. The field monitoring systems were developed as part of the research, as was bespoke laboratory physical simulation of a pitch construction. It was found that very variable yields (% out versus % in) of water were detected from the monitored field sites. The values varied across a range of < 1 to 88%, with the natural turf providing higher yields in general. The antecedent weather patterns did not show a clear relationship with yield as might have been expected. However, it was not always possible to retrieve detailed information on the subsoil conditions or hydraulic capability reducing the conclusiveness of the discharge flow measurements. The scaled laboratory testing of pitch materials established the importance and magnitude of barriers to percolation of surface water through the layers of the pitch constructions, in particular artificial pitch profiles. It was found that a significant proportion of the total rainfall head was required to instigate percolation of surface water through the carpet and into the pitch i.e. breakthrough head. In addition, several constituent pitch materials exhibited water retention characteristics that reduced that rate of free percolation of surface water through the pitch profile. The net impact is to reduce the net available head of water to further drive flow through the layers to the pipe network drainage system. A conceptual hydraulic model, developed from the literature, was further developed into a simple numerical model. The model was informed by parameters determined from the laboratory measurements and key groundwater drainage flow theory to attempt to replicate a pitch drainage system. It was envisaged that the models would be validated by the field data, although this proved challenging as a result of the field data variability and the multivariate nature of the influences on flows measured. A key finding of the modelling was further establishing the likely head of water generated at the interfaces between the bottom of the granular sub-base and the pipe collection drainage system beneath. This resulted in limited pipe infiltration and low total flows to the outfall, further corroborating the project field results and the anecdotal observations from practitioners. The combined unique data sets provide a refined model for sports pitch drainage to both reinforce understanding and inform practical design and operation.
22

Couplages température-endommagement-perméabilité dans les sols et les roches argileux / Effect of temperature on damage and permeability of clayey soils and rocks

Monfared, Mohammad 01 April 2011 (has links)
Le stockage des déchets radioactifs dans les formations géologiques profondes peu perméables comme les argilites et les argiles plastiques est envisagée comme une solution possible et fait l'objet de nombreuses études depuis une trentaine d'années. Dans le cadre du projet européen TIMODAZ, l'accent a été mis sur l'étude des effets d'une augmentation de la température engendrée par les déchets exothermiques sur la zone endommagée autour d'une galerie souterraine de stockage. Dans le cadre de ce projet, une étude expérimentale sur le comportement thermique de l'argile de Boom et de l'argile à Opaline a été réalisée. Afin de surmonter les difficultés reliées à l'étude expérimentale des matériaux peu perméables en laboratoire, une nouvelle cellule triaxiale à court chemin de drainage a été mise en œuvre. Les essais ainsi qu'une modélisation numérique montrent que la re-saturation des échantillons désaturés par le processus d'excavation, transport, stockage et préparation peut être réalisée beaucoup plus rapidement par ce dispositif. Les essais de chargement mécanique et thermique en condition drainée (c'est-à-dire avec une surpression interstitielle engendrée négligeable) peuvent être réalisés également dans cette cellule avec des vitesses de chargement plus élevée comparée aux cellules triaxiales classiques. La possibilité de réactivation d'une bande de cisaillement par pressurisation thermique du fluide interstitiel dans un échantillon de l'argile de Boom est mise en évidence. On observe qu'un plan de rupture préexistant dans l'échantillon agit comme un plan de faiblesse pouvant être réactivé de façon préférentielle au moment de la rupture. La résistance au cisaillement obtenue sur le plan de rupture est inférieure à celle de matériau intact pour l'argile de Boom. Le comportement thermique de l'argile à Opaline a été étudié à partir d'essais de chauffage en condition drainée et non drainée sur des échantillons saturés. L'essai de chauffage drainé montre un comportement thermo-elasto-plastique avec limite expansion/contraction à 65°C. Ce comportement est similaire au comportement des argiles faiblement surconsolidées. L'analyse des résultats de l'essai de chauffage non drainé met en évidence que l'eau interstitielle dans l'argile à Opaline a un coefficient de dilation thermique plus important comparé à celui de l'eau libre. Dans la gamme de températures étudiées (25°C-80°C), les mesures de perméabilité sur les échantillons endommagés par un chargement déviatorique ne montrent aucun effet de l'endommagement sur la perméabilité, ce qui prouve la bonne capacité de scellement de l'argile de Boom et l'argile à Opaline saturées / Storage of exothermic radioactive waste in deep low permeability geological formations such as clayey rocks and plastic clays is a solution considered for long term repositories. However the excavation of underground galleries creates a damaged zone (EDZ). The effect of the damage zone on the transport properties of the geological barrier has been widely studied. Within the framework of the TIMODAZ European project, emphasis has been put on the effect of temperature. As a partner of this project, the current work is performed to investigate the coupling effect between temperature, damage and permeability on Boom clay and Opalinus clay through an experimental study. View to the experimental difficulties related to the low permeability materials, a new hollow cylinder triaxial cell with short drainage path specifically designed to study the thermo-hydro-mechanical behaviour of very low permeable materials is developed during this work. The tests and the numerical analysis show that the short sample drainage path reduces significantly the time needed to resaturate an initially unsaturated sample and it also permits to achieve drained conditions (i.e. negligible excess pore pressure during testing) with a higher loading rate. For Boom clay, the effect of the pore water thermal pressurisation on a sample with a pre-existing shear band is investigated. The undrained heating under shear stress decreases the effective stress on the sample which leads to its failure. An existing failure plane in the sample behaves like a preferential weakness plane which can be reactivated by pore water thermal pressurisation. The estimated shearing resistance along the sheared plane is smaller than that of the intact material. For the Opalinus claystone, drained heating on a saturated sample shows that this claystone behaves like a slightly overconsolidated material (thermo-elasto-plastic behaviour) with transition from expansion to contraction at 65°C. The decrease of the permeability of the sample before and after the heating-cooling cycles proves the irreversible volumetric compaction of the sample. The undrained heating test on the Opalinus claystone induces an excess pore pressure in the sample which cannot be explained by the difference between the free water thermal expansion coefficient and that of the solid matrix. The back analysis of the results shows a higher value for the water thermal expansion coefficient as compared to that of free water. Permeability measurements at 25°C and 80°C on samples previously damaged by deviatoric loading show no significant effect of damage on the permeability of the samples. These results confirm the good sealing capacity of both clays at various temperatures
23

Development of a finite element matrix (fem)three-phase three-limb transformer model for Geomagnetically Induced Currents (GIC) experiments

Mkhonta, Sizwe 10 February 2021 (has links)
Geomagnetically Induced Currents (GIC) have been a growing concern within power system operators and researchers as they have been widely reported to lead to power system related issues and material damage to system components like power transformers. In power transformers, GIC impacts are evidenced by part-wave saturation, resulting in transformers experiencing increased presence of odd and even harmonics. The three-phase three-limb (3p3L) transformer has been found to be the most tolerant to high dc values compared to other core types. The research was based on a hypothesis which reads “transformer laboratory testing results can be used as a guide towards developing suitable Finite Element Matrix (FEM) models to be used for conducting GIC/DC experiments”. This study thus investigates the response of a 15 kVA 3p3L laboratory transformer to dc current, emulating the effects of GICs. GIC and dc current are the same under steady state conditions, and hence mentioned interchangeably. Laboratory tests conducted identified two critical saturation points when the transformer is exposed to dc. The early saturation point was identified to be at around 1.8 A/phase of dc (18% of rated current), while the deep saturation point was at around 15 to 20 A/phase of dc (about 72% of rated current). Further analysis showed that holes drilled on the transformer can lower the transformer knee-point by about 26%, depending on the size and location of the holes. The holes hence end up affecting the operating point of the transformer due to losses occurring around the holes. A transformer FEM model was developed following the laboratory exercise, where it was concluded that a 2D model leads to grossly erroneous results, distorting the magnetizing current by about 60% compared to the laboratory results. A solid 3D model improved performance by about 30% as it took the transformer's topological structure into consideration. The 3D model was then refined further to include joints and laminations. It was discovered that laminations on the transformer need to be introduced as stacks of the core, with each core step split into two, allocating a 4% air gap space between stacks. Refinement of the T-joints proved that the joints have a relatively high influence on the transformer behaviour, with their detailed refinement improving the transformer behaviour by about 60%. The final FEM model was used for dc experiments. The results of such experiments showed close resemblance to the laboratory results, with saturation points identified in FEM lying within 10% of the laboratory identified saturation points. Overall, the various investigation methods explored showed that the hypothesis was satisfactorily proven true. Laboratory results functioned as a guide in developing the model, offering a reference case.
24

Iron Deficiency and Iron Deficiency Anemia: Implications and Impact in Pregnancy, Fetal Development, and Early Childhood Parameters

Means, Robert T. 01 February 2020 (has links)
A normal pregnancy consumes 500–800 mg of iron from the mother. Premenopausal women have a high incidence of marginal iron stores or iron deficiency (ID), with or without anemia, particularly in the less developed world. Although pregnancy is associated with a “physiologic” anemia largely related to maternal volume expansion; it is paradoxically associated with an increase in erythrocyte production and erythrocyte mass/kg. ID is a limiting factor for this erythrocyte mass expansion and can contribute to adverse pregnancy outcomes. This review summarizes erythrocyte and iron balance observed in pregnancy; its implications and impact on mother and child; and provides an overview of approaches to the recognition of ID in pregnancy and its management, including clinically relevant questions for further investigation.
25

Bestimmung bodenmechanischer Parameter nach fortgeschrittenen Methoden

Schwiteilo, Erik 13 June 2017 (has links)
Ziel der vorliegenden Arbeit ist es, eine weitestgehend allgemeine Beschreibung einer Herangehensweise für Auswertung und Interpretation von mechanischen Versuchen an Boden zu ermöglichen. Dafür werden Parameter eingeführt und vorgestellt, die das Verhalten des Bodens zustandsunabhängig beschreiben, wobei der Bodenzustand durch die Spannung und die Dichte (Porenzahl e) definiert ist. Zu Beginn wird das typische Bodenverhalten und die Standardauswertung in Kompressions- und Scherversuchen beleuchtet. Bei gezeigten Beispielauswertungen können die Scherparameter φ ‘ und c' nicht eindeutig bestimmt werden. Um eine Grundlage für die fortgeschrittene Auswertung zu schaffen, werden Referenzzustände eingeführt. Die Betrachtung der Referenzzustände bringt den Vorteil, dass die genutzten Bodenparameter unabhängig von Ausgangsspannung und -dichte der untersuchten Proben sind. Weiterhin wird das prinzipielle Bodenverhalten in Relation zu den Referenzzuständen beschrieben. Basierend auf den eingeführten Referenzzuständen wird ein Auswertekonzept vorgestellt. In diesem werden mit Hilfe von Spannungsnormierungen Einflüsse aus Spannung und Dichte auf die Versuchsergebnisse zusammengefasst. Die am Anfang beschriebenen Beispielauswertungen werden über das eingeführte Auswertekonzept näher betrachtet. Für eine Bewertung von Scherversuchen werden Vorschläge für Bewertungskriterien, basierend auf dem zuvor beschriebenen Konzept, gegeben. Mit Hilfe der vorgeschlagenen Kriterien können einzelne Teilversuche identifiziert werden, welche bei der Bestimmung der Scherparameter nicht mit berücksichtigt werden sollten. Dies wird an einem der Beispielböden verdeutlicht. Zuletzt sind mögliche Fehleinschätzungen des Bodenverhaltens bei der Auswertung von Laborversuchen beschrieben. Daraus abgeleitet ergeben sich Unterschiede in den abgeleiteten Spannungen.
26

Laboratory testing of shotcrete with fibres of steel, basalt or synthetic materials

Rengarajan, Muralidharan January 2020 (has links)
Shotcrete or sprayed concrete has become an inevitable material for stabilising and supporting hard rock tunnels. To prevent rock block fallouts in the excavated tunnel, shotcrete is pneumatically projected under high pressure on the rock surface. This method has proven to reduce the construction time drastically, and the addition of fibres in the shotcrete material results in Fibre Reinforced Shotcrete (FRS). The fibres increased the strength of the parent matrix and made the reinforcement bar (mesh) placing procedure with its heavy labour work unnecessary. Even though FRS have been in use for many years, to design FRS lining there are currently no complete, widely used guidelines. Traditionally, the most frequently used testing was a traditional beam testing method which helps to determine the FRS mechanical properties. Previous studies prove that the result from beams often show a high scatter in the results. Another proposed standard testing method is the Round Determinate Panel method to determine the energy absorption capacity. This method has the potential to be a reliable test procedure with a repeatable and predictable crack pattern.In this project, an experimental investigation was carried out to understand the behaviour of macro fibres of steel, basalt and synthetic materials in FRS. The specimens were sprayed in situ and cast in laboratory, of which the in situ samples were assigned to different curing conditions. The test standard ASTM C-1550 was used to design the round panels and SS-EN 14488-3 for the beams. Each type of FRS specimen’s compressive strength was tested, evaluated and compared. The single fibre pullout strength was tested to determine the bond strength between shotcrete and fibres.The calculated results showed the coefficient of variation (COV) of energy absorption capacity from panels varied within 3 % – 13 % and the residual strength of beams within 12 % – 35 %. Irrespective of testing method, the Dramix 3D steel fibre and Minibars basalt fibre for the tested cases showed the lowest dispersion of result. Minibars showed a significant increase in compressive strength compared to the other fibres. Single fibre pullout testing concluded that the steel fibre had superior load capacity at the first crack. Minibars showed a strength close to that of steel fibres and a failure mode similar to that with synthetic fibres.
27

Small-Volume Blood Collection Tubes to Reduce Anemia and Transfusion in Intensive Care Unit Patients / Reducing Blood Sampling Volumes in the Intensive Care Unit

Siegal, Deborah January 2018 (has links)
Blood sampling causes significant blood loss in intensive care unit (ICU) patients (up to 41 mL per day). Only 10% of the blood collected is used for testing suggesting that volumes can be reduced without compromising patient care or laboratory processes. Blood loss contributes to anemia which is highly prevalent in the ICU (>90% after 3 days) and is associated with major adverse cardiovascular outcomes and death. Diagnostic blood loss increases the likelihood of red blood cell (RBC) transfusion which is administered to about 40% of ICU patients (half are given in absence of hemorrhage) and has significant health risks. Small-volume blood collection tubes, which collect about 50% less blood, are available, but rarely used in adults. They have the same cost as standard-volume tubes and are compatible with laboratory equipment. The rationale for the continued use of standard-volume tubes is a theoretical concern about inadequate volume for testing, and the absence of data showing the benefit of small-volume tube use on an important clinical outcome. A study is needed to show that small-volume tubes reduce blood loss, anemia and RBC transfusion without harms or negative consequences on patient care and hospital procedures compared to standard-volume tubes. If this could be shown, it may lead to practice change regarding blood collection for laboratory testing. A stepped-wedge cluster randomized trial is the ideal study design for this low-risk intervention. By incorporating the small-volume tubes into routine clinical practice and using administrative and hospital electronic medical record data, this study would be a pragmatic, cost-effective way to evaluate effectiveness and implementation. However, prior to conducting a full-scale trial powered on clinical outcomes, a pilot study is needed to determine whether a larger study will be feasible. The goals of this thesis are to (i) summarize the existing evidence regarding small-volume tubes; (ii) discuss cluster randomized trial methodology;(iii) discuss the use of health care administrative data for research; (iv) discuss the role of pilot studies; and (v) present the design of a pilot stepped wedge randomized trial of small-volume versus standard-volume blood collection tubes to evaluate the feasibility of a full-scale trial. / Thesis / Master of Science (MSc) / Blood testing is a preventable cause of blood loss. Patients in the intensive care unit (ICU) have about 41 mL of blood taken per day for testing (like donating 1 unit of blood every 8 days). This contributes to anemia (low red blood cells) and transfusion, which are harmful. About 40% of ICU patients get at least one red blood cell transfusion which is a limited resource with health risks. Most of the blood sent to the laboratory is discarded (up to 90%) suggesting that volumes can be reduced without compromising care. The goals of this thesis are to (i) summarize the evidence for reducing blood loss for laboratory testing; (ii) discuss cluster randomized trials; (iii) discuss use of health care administrative data for research; (iv) discuss the role of pilot studies; and (v) present a pilot stepped wedge cluster randomized trial of small-volume versus standard-volume blood collection tubes in ICU patients.
28

Změny úrovně trénovanosti a kondičních parametrů vodních pólistů v RTC 2012/2013 / Changes in fitness levels and fitness parameters for water polo players during ATC 2012/2013

Krejčová, Eva January 2014 (has links)
Title: Changes in fitness levels and fitness parameters for water polo players during ATC 2012/2013 Objectives: The aim of the work determine the current performance through changes in competition and the transition period for players (n = 12, mean age 22.22 years + - 5, 6 years) water polo. Methods: To obtain a personal history of the probands was chosen method of qualitative structured interview with closed questions. From the basic anthropometrics values measured body height, weight and circuit parameters. Non-standard specific test for swimming biokinetic was at water polo players performed twice. The first test in the racing season (24th 3. 2013, 26th 3. 2013, 2nd 4. 2013), the second under the same conditions (10th 9. 2013), in a transitional period of annual training cycle (ATC) 2012/ 2013. The content of the selected non-standard specific test was compared test1 and test 2, which ran without the possibility of resting players were only interrupted by 40 seconds when tested probands carried leaps with throw up arms slightly bent at the elbows. This test was measured actual performance changes in ATC 2012/2013. Furthermore, fatigue was observed between test 1 and test 2 in the race and the transition period. During the trial, the parties all observed repeatedly drawn lactate. Results: All...
29

Numerical and experimental studies of shallow cone penetration in clay

Hazell, Edmund January 2008 (has links)
The fall-cone test is widely used in geotechnical practice to obtain rapid estimates of the undrained shear strength of cohesive soil, and as an index test to determine the liquid limit. This thesis is concerned with numerical modelling of the penetration of solids by conical indenters, and with interpretation of the numerical results in the context of the fall-cone test. Experimental studies of shallow cone penetration in clay are also reported, with the aim of verifying the numerical predictions. The practical significance of the results, in terms of the interpretation of fall-cone test results, is assessed. Results are reported from finite element analyses with the commercial codes ELFEN and Abaqus, in which an explicit dynamic approach was adopted for analysis of continuous cone indentation. Quasi-static analyses using an elastoplastic Tresca material model are used to obtain bearing capacity factors for shallow cone penetration, taking account of the material displaced, for various cone apex angles and adhesion factors. Further analyses are reported in which a simple extension of the Tresca material model, implemented as a user-defined material subroutine for Abaqus, is used to simulate viscous rate effects (known to be important in cohesive soils). Some analyses with the rate-dependent model are displacement-controlled, while others model the effect of rate-dependence on the dynamics of freefall cone indentation tests. Laboratory measurements of the forces required to indent clay samples in the laboratory are reported. Results from displacement-controlled tests with imposed step-changes in cone speed, and from freefall tests, confirm that the numerical rate-dependent strength model represents the observed behaviour well. Some results from experiments to observe plastic flow around conical indenters are also presented. Finally, additional numerical analyses are presented in which a critical state model of clay plasticity is used to study the variation of effective stress, strain and pore pressure around cones in indentation tests at various speeds.
30

Laboratory characterisation of pavement foundation materials

Edwards, Jonathan Paul January 2007 (has links)
Pavement foundations for major roads in the UK were historically designed on an empirical basis, related to a single design chart, restricting the incorporation of superior performing materials or materials for which the empirical data sets were not available. The adoption of performance based specifications was promoted as they are perceived to 'open up' the use of alternative materials (including 'local' sources of primary materials) or techniques, and allow for the incorporation of superior performance into the overall pavement design. Parallel developments to the performance based design of pavement foundations (allowing for superior performance) and in situ testing required the support of laboratory based performance tests. These laboratory based tests were required to determine material performance parameters (elastic modulus and resistance to permanent deformation) for both unbound and hydraulically bound pavement foundation materials. A review of the available laboratory apparatus indicated that they were either; unrealistic (and hence unable to provide the required material performance parameters), or overly complex and more suited to fundamental research. Therefore, the requirement for developmental research work was identified. The research reported herein details the development, manufacture and initial evaluation of simplified laboratory apparatus (the Springbox for unbound materials and static stiffness test for hydraulically bound mixtures) designed to produce the performance parameters of elastic modulus and relative resistance to permanent deformation for pavement foundation materials. The equipment and test procedure evaluation was undertaken across a range of materials, giving initial guidance on likely in situ performance. The innovative laboratory apparatus and materials guidance (including the potential to use recycled and secondary aggregates) was incorporated into key Highways Agency specification and guidance documents, which in turn influence construction practice outside of motorways and major trunk roads. This research concludes by outlining a number of recommendations for continued development and evaluation, including feeding back data sets from long term in situ performance testing for subsequent refinement of assumptions.

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