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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.
401

Reduction of oil pump losses in automatic transmissions

Larsson, Camilla January 2014 (has links)
In the vehicle industry it is of great interest to reduce the emissions and lower the fuel consumption.Up to now a lot of effort has been put into increasing the efficiency of the engine,but it starts to get expensive to keep improving the engine. In this master thesis the transmissionand especially the oil supply to the transmission is investigated. An example of how the requirements of an oil pump can be decided is described. Knowingthe requirements different pumps may be adapted to meet the demands. The gear pumpused today is compared with a variable displacement pump and an electric pump. The gearpump is not possible to control, but the other two are. A few simple control strategies areintroduced. The strategies are implemented and the three pumps are used in the same drivecycle. It is shown that it is possible to reduce the energy that the pump requires if it isreplaced by a variable vane pump or an electric pump.
402

Radiation Induced Effects in Electronic Devices and Radiation Hardening By Design Techniques

Walldén, Johan January 2014 (has links)
The aim with this thesis has been to make a survey of radiation hardened electronics, explaining why and how radiation affects electronics and what can be done to harden it. The effects radiation have on electronics in general and in specific commonly used devices are explained qualitatively. The effects are divided into Displacement Damage (DD), Total Ionizing Dose (TID) and Single Event Effects (SEEs). The devices explained are MOSFETs, Silicon On Insulator (SOI) transistors, 3D-transistors, Power transistors, Optocouplers, Field Programmable Gate Arrays (FPGAs), three dimensional circuits (3D-ICs) and Flash memories. Different radiation hardening by design (RHBD) techniques used to reduce or to remove the negative effects radiation induces in electronics are also explained. The techniques are Annular transistors, Enclosed source/drain transistors, Guard rings, Triple Modular Redundancy (TMR), Dual Interlocked Storage Cells (DICE), Guard gates, Temporal filtering,Multiple drive, Charge dissipation, Differential Charge Cancellation (DCC), Scrubbing, Lockstep, EDAC codes and Watchdog timers.
403

Thermo-Hydro-Mechanical Behavior of Conductive Fractures using a Hybrid Finite Difference – Displacement Discontinuity Method

Jalali, Mohammadreza January 2013 (has links)
Large amounts of hydrocarbon reserves are trapped in fractured reservoirs where fluid flux is far more rapid along fractures than through the porous matrix, even though the volume of the pore space may be a hundred times greater than the volume of the fractures. These are considered extremely challenging in terms of accurate recovery prediction because of their complexity and heterogeneity. Conventional reservoir simulators are generally not suited to naturally fractured reservoirs’ production history simulation, especially when production processes are associated with large pressure and temperature changes that lead to large redistribution of effective stresses, causing natural fracture aperture alterations. In this case, all the effective processes, i.e. hydraulic, thermal and geomechanical, should be considered simultaneously to explain and evaluate the behavior of stress-sensitive reservoirs over the production period. This is called thermo-hydro-mechanical (THM) coupling. In this study, a fully coupled thermo-hydro-mechanical approach is developed to simulate the physical behavior of fractures in a plane strain thermo-poroelastic medium. A hybrid numerical method, which implements both the finite difference method (FDM) and the displacement discontinuity method (DDM), is established to study the pressure, temperature, deformation and stress variations of fractures and surrounding rocks during production processes. This method is straightforward and can be implemented in conventional reservoir simulators to update fracture conductivity as it uses the same grid block as the reservoir grids and requires only discretization of fractures. The hybrid model is then verified with couple of analytical solutions for the fracture aperture variation under different conditions. This model is implemented for some examples to present the behavior of fracture network as well as its surrounding rock under thermal injection and production. The results of this work clearly show the importance of rate, aspect ratio (i.e. geometry) and the coupling effects among fracture flow rate and aperture changes arising from coupled stress, pressure and temperature changes. The outcomes of this approach can be used to study the behavior of hydraulic injection for induced fracturing and promoting of shearing such as hydraulic fracturing of shale gas or shale oil reservoirs as well as massive waste disposal in the porous carbonate rocks. Furthermore, implementation of this technique should be able to lead to a better understanding of induced seismicity in injection projects of all kinds, whether it is for waste water disposal, or for the extraction of geothermal energy.
404

Nutzungsdauer von Kühen nach Labmagenverlagerung und Begleitkrankheiten in Abhängigkeit vom Schweregrad der Erkrankungen

Müller, Matthias 05 June 2014 (has links) (PDF)
Die chirurgische Labmagenreposition ist ökonomisch sinnvoll. Bei älteren Kühen (>5 Jahre) mit hoher Milchleistung und gleichzeitig schweren Begleiterkrankungen (Risikopatienten) ist eine kritische Prognose der Nutzungsdauer angezeigt. Bei Kühen mit einer Nutzungsdauer <1 Monat sind die Laborparameter Protein, Albumin, Beta-Hydroxybutyrat und Cholesterol für die Prognose der Nutzungsdauer nutzbar.
405

Untersuchungen zum Verhalten der Serum-Kalium-Konzentration bei Kühen mit Labmagenverlagerung und ihre Beziehung zum Krankheitsverlauf

Meyer-Müller, Alexandra 05 June 2014 (has links) (PDF)
Hypokaliämie ist bei Kühen mit Labmagenverlagerung und zusätzlichen Komplikationen eines der klinischen Probleme. Besonders bei Kühen mit rechtsseitiger Labmagenverlagerung werden Beziehungen des Kaliums zum Krankheitsverlauf deutlich. Serum-Kalium-Konzentrationen < 2 mmol/l sind prognostisch infaust. Durch Begleiterkrankungen werden bei Kühen mit Labmagenverlagerung Kalium sowie Cholesterol, Protein, Albumin, Bilirubin und Beta-Hydroxybutyrat zusätzlich negativ beeinfllusst.
406

Landslide kinematics and interactions studied in central Georgia by using synthetic aperture radar interferometry, optical imagery and inverse modeling

Nikolaeva, Elena January 2014 (has links)
Landslides are one of the biggest natural hazards in Georgia, a mountainous country in the Caucasus. So far, no systematic monitoring and analysis of the dynamics of landslides in Georgia has been made. Especially as landslides are triggered by extrinsic processes, the analysis of landslides together with precipitation and earthquakes is challenging. In this thesis I describe the advantages and limits of remote sensing to detect and better understand the nature of landslide in Georgia. The thesis is written in a cumulative form, composing a general introduction, three manuscripts and a summary and outlook chapter. In the present work, I measure the surface displacement due to active landslides with different interferometric synthetic aperture radar (InSAR) methods. The slow landslides (several cm per year) are well detectable with two-pass interferometry. In same time, the extremely slow landslides (several mm per year) could be detected only with time series InSAR techniques. I exemplify the success of InSAR techniques by showing hitherto unknown landslides, located in the central part of Georgia. Both, the landslide extent and displacement rate is quantified. Further, to determine a possible depth and position of potential sliding planes, inverse models were developed. Inverse modeling searches for parameters of source which can create observed displacement distribution. I also empirically estimate the volume of the investigated landslide using displacement distributions as derived from InSAR combined with morphology from an aerial photography. I adapted a volume formula for our case, and also combined available seismicity and precipitation data to analyze potential triggering factors. A governing question was: What causes landslide acceleration as observed in the InSAR data? The investigated area (central Georgia) is seismically highly active. As an additional product of the InSAR data analysis, a deformation area associated with the 7th September Mw=6.0 earthquake was found. Evidences of surface ruptures directly associated with the earthquake could not be found in the field, however, during and after the earthquake new landslides were observed. The thesis highlights that deformation from InSAR may help to map area prone landslides triggering by earthquake, potentially providing a technique that is of relevance for country wide landslide monitoring, especially as new satellite sensors will emerge in the coming years. / Erdrutsche zählen zu den größten Naturgefahren in Georgien, ein gebirgiges Land im Kaukasus. Eine systematische Überwachung und Analyse der Dynamik von Erdrutschen in Georgien ist bisher nicht vorhanden. Da Erdrutsche durch extrinsische Prozesse ausgelöst werden, wird ihre Analyse zusammen mit Niederschlag und Erdbeben zu einer besonderen Herausforderung. In dieser Dissertation beschreibe ich die Potenziale und Limitierungen der Fernerkundung für die Detektion und das Verständnis von Erdrutschen in Georgien. Die Arbeit ist in einer kumulativen Form geschrieben, und besteht aus einer allgemeinen Einführung, drei Manuskripten sowie einer Zusammenfassung und einem Ausblick. In der vorliegenden Arbeit, Gestimme ich die Oberflächenverschiebung von aktiven Erdrutschen mit Methoden der Radarinterferometrie (InSAR). Die langsamen Erdrutsche (cm pro Jahr) konnten im einfachen Vergleich zeitlich unterschiedlicher Radaraufnahmen (two-pass InSAR), gut nachgewiesen werden. Die extrem langsamen Erdrutsche (mm pro Jahr) konnten hingegen nur mit InSAR Zeitreihentechniken nachgewiesen werden. Der Erfolg der angewandten InSAR Techniken wird durch die erfolgreiche Identifikation von bisher unbekannten Erdrutschen in Zentral Georgien veranschaulicht. Sowohl das Ausmaß als auch die Verschiebungsrate der Erdrutsche wurden quantifiziert. Ferner, um die mögliche Tiefe und Lage von potentiellen Gleitflächen zu bestimmen, wurden inverse Modelle entwickelt. Inverse Modellierung sucht nach Parametern der Quelle, welche die beobachtete Verschiebungsverteilung reproduzieren können. Ferner habe ich anhand der ermittelten Verschiebungsverteilung aus InSAR in Verbindung mit der Morphologie aus Luftaufnahmen das Volumen der untersuchten Erdrutsche empirisch abgeleitet. Ich habe eine Volumenformel für unseren Fall angepasst, und die verfügbaren Datensätze bezüglich Seismizität und Niederschlag kombiniert, um potenzielle auslösende Faktoren zu analysieren. Eine leitende Frage hierbei war: Was sind die Ursachen für die Beschleunigung von Erdrutschen, wie sie in den InSAR Daten beobachtet werden konnte? Das Untersuchungsgebiet in Zentral Georgien ist seismisch sehr aktiv. Als zusätzlichen Produkt der InSAR Datenanalyse wurde ein Deformationsgebiet gefunden, welches im Zusammenhang mit dem Mw=6.0 Erdbeben vom 7. September 2009 zusammenhängt. Beweise für Oberflächenbrüche, die direkt mit dem Erdbeben zusammenhängen, konnten in dem Gebiet nicht gefunden werden, jedoch konnten während und nach dem Erdbeben neue Erdrutsche beobachtet werden. Die Dissertation unterstreicht, dass Verformungsinformationen aus InSAR Analysen helfen können ein Gebiet, welches von Erdbebeninduzierten Erdrutschen gefährdet ist, zu kartieren. Potenziell stellt InSAR eine Technik dar, die von Bedeutung für die landesweite Überwachung von Erdrutschen sein kann, insbesondere im Hinblick auf die neuen Satellitensensoren, die in den kommenden Jahren verfügbar sein werden.
407

Non-linear finite element analysis of reinforced concrete panels and infilled frames under monotonic and cyclic loading : structures under plane stress loading are analysed up to and beyond the peak load : non-linear material properties including cracking, crushing and the non-linear behaviour at the interface of members are considered

Naji, Jamal Hadi January 1989 (has links)
A non-linear finite element program to simulate the behaviour of infilled frames and plane stress reinforced concrete members under the action of monotonic and cyclic loading has been developed. Steel is modelled as a strain hardening plastic material, and in the concrete model cracking, yielding and crushing are considered. The separation, sliding, and opening and closing of initial gaps at the interfaces between the frame and the infill panels are accounted for by adjusting the properties of interface elements. The non-linear equations of equilibrium are solved using an incremental-iterative technique performed under load or displacement control. The iterative techniques use the standard and modified Newton-Raphson method or the secant Newton method. An automatic load incrementation scheme, line searches, and restart facilities are included. The capabilities of the program have been examined and demonstrated by analysing five reinforced concrete panels, a deep beam, a shear wall, and eight infilled frames. The accuracy of the analytical results was assessed by comparing them with the experimental results and those obtained analytically by other workers and shown to be good. A study of the effects of some material and numerical parameters on the results of analyses of reinforced concrete deep beam has been carried out. Two techniques have been proposed and used to overcome numerical problems associated with local strain concentrations which occur with the displacement control, when path dependent incremental iterative procedures are used for inelastic materials. The displacement control provided with these modifications has been shown to be more efficient than the load control.
408

Post-disaster Transitional Housing for Displaced People

Guo, Yuqiao 01 January 2015 (has links)
Post-disaster displacement, with the increasing frequency and intensity of natural disasters, is quickly arising to become one of the most serious humanitarian challenges in the 21st century. As post-disaster housing spans several phases, the transitional housing phase is equally crucial as emergency sheltering and permanent housing: as dwellers remain in transitional housing projects up to years, their physical and emotional wellbeing is directly influenced by their surrounding built environment. Existing literature and practice have not paid enough attention to the built structures of post-disaster transitional housing. This thesis revisits past practices world-wide and architectural theory in the 20th century. Arguing that current transitional-housing design methodology is still deeply rooted in early 20th century Modernist ideologies, this thesis ties the missing link between architectural theory and humanitarian built environment design. Through examining theories and case studies, this thesis stresses the importance of approaching post-disaster transitional housing through the lens of architectural design, and makes suggestions for future improvements.
409

Rotordynamics of Twin-Screw Pumps

Aboel Hassan Muhammed, Ameen 02 October 2013 (has links)
Twin-screw pumps are positive displacement machines. Two meshing screws connected by timing gears convey the fluid trapped in the screw chambers axially from suction to discharge and force it out against the back pressure. Because of the screw geometry, the circumferential pressure field around the screws is not balanced, resulting in net dynamic and static pressures applied on the rotors. The research work presented here aims at building and verifying a model to predict both: (1) the exciting lateral hydrodynamic forces produced by the unbalanced pressure field, and (2) the rotor response due to those forces. The model rests on the screw pump hydraulic models for predicting the pressure in the screw chambers as a function of the discharge pressure. These models are extended to predict the steady state dynamic pressure field as a function of the rotational angle of the rotor. The dynamic force resulting from the dynamic pressure field is calculated and applied to the rotor as a set of super-synchronous periodic forces. The structural model of the screw, although nonsymmetrical, was found to be accurately represented by an axisymmetric equivalent structure. The rotor response to the dynamic super-synchronous forces is calculated to predict the pump rotordynamic behavior. The work in this dissertation presents: (1) the axisymmetric structural model of the rotors (2) the proposed dynamic pressure model, (3) the screw pump rotor response, (4) the experimental validation of the dynamic pressure model and rotor response. The topic of twin-screw pump rotordynamics is absent from the literature. The original contribution of the work presented in this dissertation to the field of rotordynamics includes: (1) demonstrating the adequacy of an axisymmetric model for modeling the screw section, (2) developing a model for predicting the dynamic pressure field around the screws, (3) characterization of the dynamic forces (synchronous and its harmonics) applied at the screw pump rotors, (4) predicting the dynamic response of twin-screw pump rotors due to hydrodynamic forces, (5) measuring the axial dynamic pressure in two circumferential planes around the screws to verify pressure predictions, (6) measuring the dynamic response of twin-screw pump rotor.
410

De-regulatory Urban Redevelopment Policies In Gecekondu Areas In Turkey: The Case Of Dikmen Valley

Muhurdaroglu, Anil 01 December 2005 (has links) (PDF)
Urban renewal policies in welfare state period are usually associated with the paradigm of social engineering that was dominant between 1940s and 1970s. However, in the wake of the fiscal crisis of the state in 1970s, and the following hegemony of the new right, urban policies including the renewal schemes have been ever-increasingly dominated by the deregulatory market oriented policies and rent seeking concerns. De-regulatory urban renewal policies focusing mainly in squatter areas have also dominated the urban policies and political discourse in Turkey since the mid-1980s and little attention has been paid to the negative consequences of these policies. Today, more than ever, residential redevelopment presents cities with a fundamental dilemma. In order to change the social and spatial condition of disstressed areas, alternative policies are implemented through either market or state-led redevelopment schemes. However, very same renewal schemes directly or indirectly leads to displacement of lower-income population, raising concerns over political equity. Likewise, overall success of these schemes often complicated by their impact on the macro-form of the cities. The main objective of this study is to discuss the impacts of de-regulatory urban renewal policies on the socio-spatial structure of contemporary Turkish cities in which, social exclusion and spatial segregation are becoming increasingly widespread. The case of Dikmen Valley Redevelopment Project provides us with the opportunities to conduct this discussion since it is one of the most significant urban renewal projects in Turkey and it is regarded as a model for the forthcoming gecekondu transformation projects. The thesis argues that although the scheme has been led by the local authority, the logic of market which revolves around the rent-seeking activities has dominated the redevelopment process in the area and main losers are the tenants who live in the squatters subjected to redevelopment.

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