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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.
211

Modelação das deformações por colapso devidas à ascensão de lençol freático / Modeling of the collapse deformations due to rise of groundwater table

Roger Augusto Rodrigues 07 December 2007 (has links)
Esta tese apresenta um estudo de caso de colapso dos solos que ocorreu durante e após o enchimento do reservatório da UHE Três Irmãos. A construção desta barragem e o subseqüente enchimento do reservatório elevaram significativamente o lençol freático, causando colapso do solo em algumas áreas. Muitos trabalhos de campo e de laboratório foram realizados para determinar o potencial de risco associado às edificações existentes no local. A elevação do lençol freático foi monitorada especialmente para o estudo de recalques de edificações. Esta pesquisa trata do estudo deste caso histórico, recuperando informações existentes e executando ensaios adicionais com sucção controlada para caracterizar o comportamento não saturado do solo. O conjunto de dados obtidos foi usado para modelar recalques reais de edificações monitoradas, considerando o Modelo Básico de Barcelona, BBM, (Alonso et al., 1990) como o modelo constitutivo mecânico do solo e o programa de elementos finitos Code_Bright. A tese apresenta a definição dos parâmetros constitutivos do solo, a calibração dos modelos, análises de sensibilidade do modelo adotado, mostrando que os resultados modelados se ajustaram satisfatoriamente aos valores de recalques medidos no campo. A partir dos resultados obtidos numericamente, constatou-se que as deformações por colapso aumentam com a redução da sucção sem saturar o solo e que os maiores colapsos são observados quando o solo é gradualmente submergido. Como a profundidade de influência da carga de fundação é muito baixa comparada à espessura da camada colapsível, muitas das deformações por colapso são resultados do peso-próprio do solo, durante o equilíbrio sob as condições hidrodinâmicas transiente e final. / This thesis presents a case history of soil collapse that took place during and after reservoir filling of Três Irmãos dam in Brazil. The construction of this dam and subsequent reservoir filling has raised the local groundwater table up to 20 m, causing soil collapse that affected many buildings. Many field and laboratory tests were conducted to determine potential risk and damage of existing buildings. The groundwater rise was monitored in some points of the region and the most susceptible buildings were also monitored specially for settlements. This work deals with the study of this case history of soil collapse, recovering existing information and performing additional suction controlled soil tests to characterize the non saturated soil behavior. This set of data was used to model the collapse settlement, considering the Barcelona Basic Model, BBM, (Alonso et al. 1990) as the soil constitutive model and the Code_Bright finite element program and, finally numerical results were compared with field ones. The thesis addresses soil parameters definition from laboratory and field tests, model calibration, sensibility analysis of the adopted model and it shows that the modeled results nicely fitted the measured values of collapse settlements. Amongst the many qualitative and quantitative findings, it is shown that collapse deformation arises from suction variation without saturating the soil and that the largest collapse rate is observed when the soil is gradually submerged. As the depth of influence of foundation load is very low compared to collapsible layer thickness, much of collapse deformation is the result of soil self weight, during equilibrium under the transient and final hydrodynamics condition.
212

Análise paramétrica da infiltração e sua influência na estabilidade de taludes em solo não saturado / Parametric analysis of infiltration and its influence on unsaturated soil slope stability

Cláudio Rodrigues dos Santos 24 March 2004 (has links)
Apresenta-se um estudo paramétrico acerca da infiltração de água e sua repercussão no Fator de Segurança de talude em solos não saturados. Na análise adota-se um talude de referência com geometria fixada conforme a inclinação típica para taludes em areia argilo siltosa, característica do Centro-Oeste do estado de São Paulo. A análise paramétrica foi desenvolvida a partir de uma simulação de fluxo em regime transiente utilizando o programa SEEP/W, que utiliza o método de elementos finitos, e posteriormente uma análise de estabilidade do talude de referência utilizando o método de Bishop simplificado conforme apresentado no programa SLOPE/W. Foram analisados taludes homogêneos compostos por três diferentes tipos de solo, uma areia, um silte argiloso e uma areia argilo siltosa. Os parâmetros analisados compreendem a curva de retenção de água, a função condutividade hidráulica do solo e a intensidade de precipitação. Verificou-se que a função condutividade hidráulica e a pressão de entrada de ar são os principais determinantes do comportamento da infiltração e conseqüentemente da estabilidade do talude. As simulações de fluxo evidenciaram que os taludes em solos mais arenosos apresentam taxas de infiltração maiores que as apresentadas pelos taludes compostos por solos siltosos. Consequentemente, os escorregamentos ocasionados pela perda da contribuição da sucção para a resistência ao cisalhamento ocorrem primeiramente nos taludes compostos por solos arenosos e posteriormente naqueles compostos por solos siltosos, fato este que pôde ser confirmado pelas análises de estabilidade do talude de referência. / A parametric study is presented about water infiltration and its repercussion in the safety factor of unsaturated soil slopes. In the analysis it is adopted a reference slope with determined geometry according to the typical inclination for slopes in silty clayey sand, characteristic of the mid-western region of São Paulo State, in Brazil. The parametric analysis was developed from a flux simulation in transient regime using the SEEP/W software, which uses the finite elements method, and thereafter, a stability analysis of the reference slope using simplified Bishop method, as presented in the SLOPE/W software. Homogeneous slopes composed by three different types of soil (sand, clayey silt and silty clayey sand) were considered. The analyzed parameters include the water retention curve, the hydraulic conductivity function and the precipitation intensity. It was verified that the hydraulic conductivity function and the air entry value are the main determinants of the infiltration behavior and, subsequently, of the slope stability. The flux simulations have evidenced that coarser soils slopes show higher infiltration rates than the ones presented in finer soil slopes. Consequently, the slides caused by the loss of the suction\'s contribution to shear strength occur primarily in coarser soil slopes than in fine soil slopes, what could be verified in the stability analysis of the reference slope.
213

Comportement hydro-mécanique des sols fins compactés au voisinage de la saturation. : application aux remblais routiers / Hydromechanical behaviour of non-standard compacted fine soils : application to road embankments

Andrianatrehina, Soanarivo Rinah 11 April 2016 (has links)
La thèse présente un ensemble de résultats expérimentaux sur des sols fins très plastiques compactés au voisinage de l’optimum Proctor normal (OPN). Elle est réalisée dans le cadre du projet ANR TerreDurable qui traite de la conception des ouvrages en terre en sols fins. Après l’étude de l’effet de compactage sur des chemins de drainage-humidification, la fissuration induite par la dessiccation est mise en évidence et analysée. Par ailleurs, des relations entre différents paramètres mécaniques (module, IPI, Résistance à la compression) et hydriques (succion, perméabilité, ..) en fonction de l’énergie de compactage et du mode de préparation sont présentées. Le comportement mécanique des sols fins compactés est étudié sur des chemins œdométriques et triaxiaux saturés et non saturés, drainés et non drainés. Dans ce dernier cas, l’évolution des paramètres de pression interstitielle de Skempton est analysée sur des chemins isotropes et déviatoires. Ceci a nécessité la mise au point d’une cellule triaxiale équipée de psychromètres à effet Peltier, de tensiomètre et de jauges de déformations. / The thesis presents an experimental study on very high plasticity soils compacted near of the standard Proctor optimum (SPO). It is performed as part of the ANR TerreDurable project which is devoted on the design of earthworks with fine soils. After the study of the effect of compaction on drying-wetting paths, induced cracking of drying is highlighted and analyzed. Furthermore, relationships between different mechanical parameters (modulus, IPI, compressive strength) and water (suction, permeability) according to the energy of compaction and method of preparation are shown. The mechanical behavior of soils compacted fine soils is studied on saturated and unsaturated, drained and undrained oedometer and triaxial. For the unsaturated undrained triaxial, the change in Skempton parameters pore pressure is analyzed on isotropic and deviatoric paths. This required the development of a triaxial cell equipped with psychrometers, tensiometer and strain gauges.
214

Wound healing and skin in severe sepsis

Koskela, M. (Marjo) 29 November 2016 (has links)
Abstract It is a generally accepted dogma that sepsis disturbs skin function and wound healing, but surprisingly there is only remote pathophysiological evidence available behind that presumption. As the skin is the largest defensive barrier, the skin dysfunction in severe sepsis deserves more attention. In this study, the suction blister model was used to create experimental wounds. The study population included 44 patients with severe sepsis and 15 controls. The blister fluid was collected to analyse cytokine profile of the skin. The transepidermal water loss and blood flow from the wound were measured. A 4mm biopsy was taken under local anaesthesia on the first and the eighth day of the study from the healthy looking skin. Then 15 healing suction blisters were excised. Serum samples were also collected on the first day of the study. The barrier restoration was diminished, and the inflammation in the wound was more intense in severe sepsis than in the controls. The expression of the basement membrane components Laminin-332 and type IV collagen decreased during the septic disease, but increased over the next 3 months without achieving the level oft he controls. The expression of tight junction proteins remained nearly intact in the healing wound in severe sepsis compared to the controls. The expression of occludin on the leading edge of the migrating keratinocytes was more restricted and late in severe sepsis compared to the controls. The levels of the tumour necrosis factor (TNF), interleukin-10 (IL-10) and IL-6 in skin blister fluid were higher in the sepsis compared to controls. The blister fluid and serum cytokine response in the sepsis differed since the levels of epidermal growth factor, vascular endothelial growth factor, TNF and basic fibroblastic growth factor (bFGF) in the blister fluid did not correlate with the levels of serum. The septic patients with multiple organ failure had higher levels of several cytokines than patients without organ failure. Survivors had lower levels of IL-10 and bFGF in blister fluid than the non-survivors. This study offers novel findings for skin and wound healing in sepsis. Together, all the findings suggest that skin dysfunction in severe sepsis exists even when the most profound structures remain intact. Understanding these mechanisms of impaired wound healing can improve future treatments, such as the timing of surgery. / Tiivistelmä Sepsiksen ajatellaan heikentävän haavanparanemista, mutta tieteellistä näyttöä on niukasti. Iholla on keskeinen osa elimistön puolustuksessa ja tasapainon ylläpidossa, joten sen toiminnan häiriintyminen systeemisessä tulehduksessa ansaitsee suuremman huomion. Imurakkulahaavat tehtiin 44 septiselle potilaalle ja 15 kontrollille. Haavoista mitattiin veden haihtumista ja veren virtausta sekä otettiin imurakkulaneste näytteeksi sytokiinimäärityksiä varten. Tutkimuksen ensimmäisenä ja kahdeksantena päivänä otettiin 4mm biopsiat terveeltä iholta ja 15 potilaalta poistettiin näytteeksi paraneva imurakkulahaava. Seeruminäytteet otettiin tutkimuksen ensimmäisenä päivänä. Veden haihtuminen haavalta oli voimakkaampaa eli ihon barrierin palautuminen oli hidastunut septisillä potilailla verrattuna kontrolleihin. Haavassa havaittu tulehdus oli sepsiksessä voimakkaampi. Tyvikalvon komponenttien Laminiini-332:n ja tyypin IV kollageenin ilmentyminen oli vähäisempää sepsiksen aikana ja lisääntyi 3kk kohdalla, mutta ei kuitenkaan saavuttanut kontrollien tasoa. Tiivisliitosproteiinien ilmentyminen oli lähes muuttumatonta sepsiksessä kontrolleihin verrattuna. Okludiinin ilmentyminen sen sijaan paranevassa haavassa vaeltavien keratinosyyttien etureunassa oli rajoittuneempaa ja myöhäisempää sepsiksessä kuin kontrolleilla. Sytokiineistä tuumorinekroositekijä (TNF), interleukiini-10 (IL-10) ja IL-6 olivat koholla imurakkulanesteessä verrattuna kontrolleihin. Epidermaalinen kasvutekijä, verisuonten endoteelikasvutekijä, TNF ja perusfibroplastinen kasvutekijä (bFGF) pitoisuudet rakkulanesteessä erosivat seerumin pitoisuuksista eli ihon sytokiiniprofiili erosi systeemisestä sytokiiniprofiilista. Potilailla, joilla oli monielinvaurio, todettiin korkeampia sytokiinipitoisuuksia. Potilailla, jotka menehtyivät 30 vrk kuluessa, oli korkeammat pitoisuudet IL-10 ja bFGF rakkulanesteessä. Tämä tutkimus tarjoaa uutta tietoa ihosta ja haavanparanemisesta sepiksessä. Tulosten perusteella voidaan todeta, että ihon toimintahäiriö on sepsiksessä todellinen, vaikka kaikkein perustavimmat rakenteet säilyvät muuttumattomina. Toimintahäiriön mekanismien ymmärtäminen voisi auttaa septisen potilaan hoidossa, kuten kirurgisten toimenpiteiden ajoittamisessa paranemisen kannalta mahdollisimman otolliseen aikaan.
215

Settlement Behavior of a Sandy Loam Due to Suction Changes Associated with Simulated Artificial Tree Roots

Areghan, Joseph I January 2012 (has links)
Shallow foundations rested on Leda clay that are widely distributed in Eastern Canada exhibit shrinkage characteristics and are prone to differential settlements. Due to this reason, significant repairs are necessary to the foundations and basements of residential structures constructed in Leda clay deposits. Differential settlements are commonly attributed to the changes in the natural water content of soils associated with water infiltration, evaporation or plant transpiration (i.e., tree-roots-suction). Various research studies have been undertaken to estimate the possible settlements of shallow foundations associated with the water infiltration or evaporation. Several thumb rules have been proposed through research studies, providing recommendations with respect to the distance at which trees must be planted as a function of their heights at maturity such that differential settlements can be avoided. However, limited studies have been carried out to estimate or model the settlements of shallow foundations taking into account the influence of tree-roots-suction. In the present research program, a comprehensive experimental study regarding the deformation characteristics of a sandy loam soil from Ottawa due to tree-root-suction is undertaken, using specially designed equipment. The study has been undertaken using a sandy loam soil so that the testing program can be conducted in a shorter period of time. An artificial rooting system (ARS) was designed and placed in a specially designed tank at the University of Ottawa to simulate tree-roots-suction and measure soil surface settlements associated with a decrease in natural water content (or increase in soil suction) using particle image velocimetry (PIV) technique. The ARS consists of an artificial root, suction generator, matric suction and volumetric water content monitoring devices. The variation of matric suction and volumetric water content are monitored at various depths using the instrumentation of the ARS. Based on the results of the experimental studies, a methodology is proposed to model the settlement behaviour of sandy loam soils due to suction from ARS, using commercial finite element software, SEEP/W and SIGMA/W (i.e. software package of GeoStudio 2007). The study offers a reasonably good comparison between the measured surface settlements and those estimated using the finite element modelling analysis. The modelling methodology presented in this thesis is promising and may be extended for estimating the settlement behaviour associated with the tree roots suction of Leda clay deposits and to other soils.
216

Bearing Capacity and Settlement Behaviour of Footings Subjected to Static and Seismic Loading Conditions in Unsaturated Sandy Soils

Mohamed, Fathi Mohamed Omar January 2014 (has links)
Several studies were undertaken by various investigators during the last five decades to better understand the engineering behaviour of unsaturated soils. These studies are justified as more than 33% of soils worldwide are found in either arid or semi-arid regions with evaporation losses exceeding water infiltration. Due to this reason, the natural ground water table in these regions is typically at a greater depth and the soil above it is in a state of unsaturated conditions. Foundations of structures such as the housing subdivisions, multi-storey buildings, bridges, retaining walls, silos, and other infrastructure constructed in these regions in sandy soils are usually built within the unsaturated zone (i.e., vadose zone). Limited studies are reported in the literature to understand the influence of capillary stresses (i.e., matric suction) on the bearing capacity, settlement and liquefaction potential of unsaturated sands. The influence of matric suction in the unsaturated zone of the sandy soils is ignored while estimating or evaluating bearing capacity, settlement and liquefaction resistance in conventional engineering practice. The focus of the research presented in the thesis has been directed towards better understanding of these aspects and providing rational and yet simple tools for the design of shallow foundations (i.e., footings) in sands under both static and dynamic loading conditions. Terzaghi (1943) or Meyerhof (1951) equations for bearing capacity and Schmertmann et al. (1978) equation for settlement are routinely used by practicing engineers for sandy soils based on saturated soil properties. The assumption of saturated conditions leads to conservative estimates for bearing capacity; however, neglecting the influence of capillary stresses contributes to unreliable estimates of settlement or differential settlement of footings in unsaturated sands. There are no studies reported in the literature on how capillary stresses influence liquefaction, bearing capacity and settlement behavior in earthquake prone regions under dynamic loading conditions. An extensive experimental program has been undertaken to study these parameters using several specially designed and constructed equipment at the University of Ottawa. The influence of matric suction, confinement and dilation on the bearing capacity of model footings in unsaturated sand was determined using the University of Ottawa Bearing Capacity Equipment (UOBCE-2011). Several series of plate load tests (PLTs) were carried out on a sandy soil both under saturated and unsaturated conditions. Based on these studies, a semi-empirical equation has been proposed for estimating the variation of bearing capacity with respect to matric suction. The saturated shear strength parameters and the soil water characteristic curve (SWCC) are required for using the proposed equation. This equation is consistent with the bearing capacity equation originally proposed by Terzaghi (1943) and later extended by Meyerhof (1951) for saturated soils. Chapter 2 provides the details of these studies. The cone penetration test (CPT) is conventionally used for estimating the bearing capacity of foundations because it is simple and quick, while providing continuous records with depth. In this research program, a cone penetrometer was specially designed to investigate the influence of matric suction on the cone resistance in a controlled laboratory environment. Several series of CPTs were conducted in sand under both saturated and unsaturated conditions. Simple correlations were proposed from CPTs data to relate the bearing capacity of shallow foundations to cone resistance in saturated and unsaturated sands. The details of these studies are presented and summarized in Chapter 3. Standard penetration tests (SPTs) and PLTs were conducted in-situ sand deposit at Carp region in Ottawa under both saturated and unsaturated conditions. The test results from the SPTs and PLTs at Carp were used along with other data from the literature for developing correlations for estimating the bearing capacity of both saturated and unsaturated sands. The proposed SPT-CPT-based technique is simple and reliable for estimation of the bearing capacity of footings in sands. Chapter 4 summarizes the details of these investigations. Empirical relationships were proposed using the CPTs data to estimate the modulus of elasticity of sands for settlement estimation of footings in both saturated and unsaturated sands. This was achieved by modifying the Schmertmann et al. (1978) equation, which is conventionally used for settlement estimations in practice. Comparisons are provided between the three CPT-based methods that are commonly used for settlement estimations in practice and the proposed method for seven large scale footings in sandy soils. The results of the comparisons show that the proposed method provides better estimations for both saturated and unsaturated sands. Chapter 5 summarizes the details of these studies. A Flexible Laminar Shear Box (FLSB of 800-mm3 in size) was specially designed and constructed to simulate and better understand the behaviour of model surface footing under seismic loads taking account of the influence of matric suction in an unsaturated sandy soil. The main purpose of using the FLSB is to simulate realistic in-situ soils behaviour during earthquake ground shaking. The FLSB test setup with model footing was placed on unidirectional 1-g shake table (aluminum platform of 1000-mm2 in size) during testing. The resistance of unsaturated sand to deformations and liquefaction under seismic loads was investigated. The results of the study show that matric suction offers significant resistance to liquefaction and settlement of footings in sand. Details of the equipment setup, test procedure and results of this study are presented in Chapter 6. Simple techniques are provided in this thesis for estimating the bearing capacity and settlement behaviour of sandy soils taking account of the influence of capillary stresses (i.e., matric suction). These techniques are consistent with the methods used in conventional geotechnical engineering practice. The studies show that even low values of capillary stresses (i.e., 0 to 5 kPa) increases the bearing capacity by two to four folds, and the settlement of footings not only decreases significantly but also offers resistance to liquefaction in sands. These studies are promising and encouraging to use ground improvement techniques; such as capillary barrier techniques to maintain capillary stresses within the zone of influence below shallow foundations. Such techniques, not only contribute to the increase of bearing capacity, they reduce settlement and alleviate problems associated with earthquake effects in sandy soils.
217

Univerzální stroj pro odstraňování volných nečistot na montážních linkách světlometů / Universal machine for removing loose dirt on headlamp assembly lines

Chylík, Michal January 2019 (has links)
This diploma thesis deals with the construction design of a non-autonomous universal machine used for suction of free dirt on assembly lines for headlights according to customer requirements. This diploma thesis also focuses on safety analyses, a draft of development diagram for a control logic machine, and on a scheme of pneumatic mechanism. The thesis contains an illustration of design documentation.
218

Přisávání plynů do proudící kapaliny. / Induced siphonage of air into the flowing fluid.

Matlák, Jiří January 2014 (has links)
The aim of this diploma thesis is to deepen the knowledge in the field of drain liquid from vessel with free surface due to the effluent jet with defined profile. Formation of complete suction vortex is taken place gradually depending on the starting conditions. In the diploma thesis basic relations in liquids considering whirl are described and the types of vortex are divided on the bases of circulation intensity. In the experimental part of diploma thesis the possibilities of liquid level prediction are searched for, where the whirl is formed depending on the size of effluent jet.
219

Obrábění kompozitních materiálů pomocí robotů / Robotic machining of composite materials

Rubišar, Václav January 2014 (has links)
This thesis deals with the robotic machining of composite materials. It is divided into two main parts - theoretical and practical part. The theoretical part is focused on detailed introduction of the term “an industrial robot” and a description of its controls, types of the robots, types of their propulsion and programming methods. Furthermore, there is a list of CAM softwares with its specification designed for both conventional machining and machining by using a robot. It also includes the introduction of composite materials and specification of their machining. The practical part deals with selection of appropriate type of bracket spindle by using a simulation software, suction design and economic evaluation of two types of machining in manufacture.
220

Aerodynamická analýza a optimalizace konfigurace letounu ARES / Aerodynamic analysis and shape optimization of ARES aircraft

Foltýn, Pavel January 2015 (has links)
This thesis deals with the aerodynamic analysis and shape modifications of the ARES aircraft. The analysis focuses on the evaluation lift, drag, and pitching moment coefficient, and further to identify the locations of stripping stream which is characterized by high drag. Before the analysis calibration of the CFD solver is done with the model, which has been measured in the wind tunnel. The aim of calibration is to verify the accuracy and veracity of the methodology used in mesh creation and calculated values. Calculated values are compared with measured data. The shape modifications of the aircraft are focused on conceptual design of the suction inlets for cooling radiators and engine aircraft. Aerodynamic analysis is performed with the modified model in order to determine the variation of lift, drag and pitching moment coefficient from its original configuration.

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