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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.
271

Effektivisering av stålbalkar i en takkonstruktion med avseende på utsläpp av växthusgaser / Steel beam effectivization in a roof construction, Considering greenhouse gas emissions

Fasihikoli, Dorsa, Filippa, Kjellander January 2024 (has links)
Introduktion (och mål) – Jordens medeltemperatur har ökat exponentiellt sedan industrialismen i slutet av 1800-talet. En ökad medeltemperatur leder till klimatförändringar som värmeböljor, översvämningar, smältande polarisar och stigande havsnivåer. För att motverka den globala uppvärmningen krävs det att Sverige och alla andra länder minskar sina utsläpp av växthusgaser. Bygg- och fastighetssektorn står för en femtedel av Sveriges totala utsläpp av växthusgaser, därmed är det viktigt att minska utsläppen från sektorn. Stål är ett vanligt material som används inom byggsektorn. Produktionen av stål är energikrävande och leder till stora utsläpp av CO2. Det är utmanande att helt undvika användningen av stål inom byggsektorn, men det finns möjligheter att minska mängden stål i konstruktioner och därmed minska klimatpåverkan. Ett sätt att reducera materialåtgången och minska klimatpåverkan i en stålkonstruktion är att effektivisera konstruktionen och undvika överdimensionering. Målet med studien är att undersöka om det är möjligt att ändra de befintliga takbalkarna av HEB-profiler i ett reningsverk till IPE-profiler, med hänsyn till vippning, buckling och nedböjning. Målet är även att beräkna klimatrelaterade skillnader mellan de befintliga takbalkar av HEB-profilerna och de IPE-profiler som kan ersätta dem.  Metod – Forskningsstrategin för studien tillämpas i form av en fallstudie, då studien syftar till att få en djupare förståelse kring undersökningsobjektet som är ett reningsverk. Datainsamlingsmetoden är en dokumentstudie där dokument används som sekundärdata för att sedan analyseras. Därefter används den analyserade datan för att besvara frågeställningarna i studien. Resultat – Resultaten av studien visar att genom att undvika överdimensionering kan mängden stål minskas för de befintliga takbalkarna i reningsverket, vilket också resulterade i minskade utsläpp av kg CO2eq. Analys – Analysen av studien visar att de befintliga takbalkar av HEB-profiler i takkonstruktionen i reningsverket kan effektiviseras genom att ersätta de med IPE-profiler. Det är gynnsamt att ändra de befintliga takbalkarna av HEB-profiler mot IPE-profiler för att minska mängden av stål och därmed utsläppen av koldioxidekvivalenter. Diskussion – Studien visar att kritiska faktorer som vippning, buckling och nedböjning är avgörande vid dimensionering av takbalkar. Vippning och nedböjning var mer avgörande än buckling vid dimensioneringen av takbalkarna i studien. Studien påvisar att de befintliga balkar av HEB-profiler i takkonstruktionen kunde ersättas med IPE-profiler både med och utan trapetsprofilerad plåt för sidostagning. Genom att införa sidostagning med trapetsprofilerad plåt minskades risken för vippning, vilket möjliggjorde en ytterligare minskning av dimensionerna på IPE-profiler och därmed minskning av stålanvändningen i takkonstruktionen. / Introduction (and aim) – The earth's middle temperature has risen exponentially since the industrialization in end of the 19th century. A rising middle temperature leads to climate changes such as heatwaves, floods, melting of the polar ice and rising of the see levels. It depends on Sweden and other countries to reduce the emissions from greenhouse gases. The construction and real estate industry causes one fifth of Sweden´s total emissions of greenhouse gases. Steel is a common construction material but the production of steel results in large emissions of CO2 and demands a lot of energy. It is challenging to cancel out steel from the construction sector, but possibilities exist to decrease the amount of steel which benefits the environment. One way to reduce the amount of steel is to optimize the construction and to avoid over dimensioning. The aim of this thesis is to research if it is possible to change HEB-roofbeams to IPE-roofbeams in a sewage plant, considering tilting, buckling and deflection. The aim is also to research the environmental impact between HEB 220 and the IPE-roofbeams whom can replace it.  Method – The research strategy for this study is a case study which refers to a deeper understanding of an object. In this case the object is the sewage plant. The data collection method is a document study where documents are used as secondary data to be analyzed. The analyzed data is then used to answer the research questions of the study.  Results – The results show that it is possible to avoid oversizing beams and that effectivization leads to a reduction of CO2eq emissions. Analysis – The analysis of the study indicates that the existing roof beams, composed of HEB profiles in the building's roof structure, can be effectives by replacing them with IPE beams. It is beneficial to change the existing roof beams from HEB profiles to IPE profiles in order to reduce the amount of steel and thus the emissions of CO2 equivalents. Discussion – The study shows dimensioning factors such as tilting, buckling and deflection determine the dimensions of the beams. Tilting and deflection were more critical than buckling in the dimensioning of the roof beams in the study. The study demonstrates that the existing beams made of HEB profiles in the roof structure could be replaced with IPE profiles, both with and without trapezoidal sheet metal for lateral bracing. By introducing lateral bracing with trapezoidal sheet metal, the risk of tipping was reduced, which enabled a further reduction in the dimensions of the IPE profiles and thus a reduction in steel usage in the roof structure.
272

The implementation of humour as deflective technique in contact boundary disturbance

Jacobs, Susanne 30 November 2007 (has links)
One potent, yet little recognized tool in therapy is humour. As the desire to be entertained through humour is near universal the establishment and return of a positive sense of humour may be considered a goal of therapy. The goal of Gestalt exploration is awareness. From its origin Gestalt theory includes addressing body experiences such as laughter and emotional expression through humour. In Gestalt Theory a contact boundary disturbance such as deflection refers to the ways in which individuals may refuse contact with their environment in order to avoid aware¬ness. The goal of this study was to explore the implementation of humour as a deflective technique where contact boundary disturbances occur, to bring about change. Aspects of humour, namely the ability to perceive the comic as well as the ability to produce it, aid therapy and relationship building, and help the client to deflect in a way that enhances emotional well-being. / Humor, geringskat in terapie, is 'n uiters sterk hulpmiddel. Aangesien die behoefte om vermaak te word deur humor universeel is, is die terugkeer van 'n positiewe sin vir humor 'n deurdagte doel vir terapie. Die doel van die Gestalt eksplorasie is bewuswording. Van die begin af sluit Gestalt teorie liggaamservaringe soos lag en emosioneie uitdrukking deur humor in. In Gestalt Teorie verwys 'n kontakgrens versteuring soos defleksie, na die wyse waarop individue kontak met die omgewing vermy, om sodoende bewuswording te vermy. Die doel van die studie was om die implementering van humor as deflektiewe tegniek, waar kontak grens versteuringe en weerstande voorkom, as verandering teweeg kan bring. Aspekte van humor, naamlik die moontlikheid om die komiese waar te neem, sowel as om dit te produseer, versterk terapie and vehoudingsbou, beide aspekte help die klient om te deflekteer op so 'n wyse dat emosioneie goedvoel bevorder word. / Social Work / M. Diac. (Play Therapy)
273

Real-time Structural Health Monitoring of Nonlinear Hysteretic Structures

Nayyerloo, Mostafa January 2011 (has links)
The great social and economic impact of earthquakes has made necessary the development of novel structural health monitoring (SHM) solutions for increasing the level of structural safety and assessment. SHM is the process of comparing the current state of a structure’s condition relative to a healthy baseline state to detect the existence, location, and degree of likely damage during or after a damaging input, such as an earthquake. Many SHM algorithms have been proposed in the literature. However, a large majority of these algorithms cannot be implemented in real time. Therefore, their results would not be available during or immediately after a major event for urgent post-event response and decision making. Further, these off-line techniques are not capable of providing the input information required for structural control systems for damage mitigation. The small number of real-time SHM (RT-SHM) methods proposed in the past, resolve these issues. However, these approaches have significant computational complexity and typically do not manage nonlinear cases directly associated with relevant damage metrics. Finally, many available SHM methods require full structural response measurement, including velocities and displacements, which are typically difficult to measure. All these issues make implementation of many existing SHM algorithms very difficult if not impossible. This thesis proposes simpler, more suitable algorithms utilising a nonlinear Bouc-Wen hysteretic baseline model for RT-SHM of a large class of nonlinear hysteretic structures. The RT-SHM algorithms are devised so that they can accommodate different levels of the availability of design data or measured structural responses, and therefore, are applicable to both existing and new structures. The second focus of the thesis is on developing a high-speed, high-resolution, seismic structural displacement measurement sensor to enable these methods and many other SHM approaches by using line-scan cameras as a low-cost and powerful means of measuring structural displacements at high sampling rates and high resolution. Overall, the results presented are thus significant steps towards developing smart, damage-free structures and providing more reliable information for post-event decision making.
274

Interfaces dans les matériaux céramiques multicouches

Thibaud, Simon 22 December 2010 (has links)
L’augmentation du nombre d’interfaces dans une matrice céramique permet d’améliorer sa ténacité. L’étude de la structure feuilletée de la nacre a démontré que cette ténacité pouvait être accrue par la présence de pontages entre les couches. Dans la première partie, le modèle de décohésion proposé par Pompidou et al. a été utilisé pour choisir un bicouche dont l’interface est naturellement favorable aux décohésions. Compte tenu du contexte de l’étude, cette analyse a permis de choisir le couple SiC/pyC comme bi-couche de base pour l’étude des interfaces. Par la suite, des matrices multicouches modèles (SiC/pyC)n (SiC, carbure de silicium issu du mélange CH3SiCl3/H2 – pyC, pyrocarbone à partir du propane) ont été élaborées par dépôt chimique en phase vapeur (CVD). Deux voies de pontage ont été abordées. La première met en œuvre une discontinuité entre les couches : les conditions d’élaboration ont été optimisées de façon à contrôler la croissance de couches minces massives et le développement de particules de surface (submicroniques) faisant office de pontage. La deuxième est basée sur un gradient de composition entre les couches de SiC grâce au développement d’une couche de SiC riche en co-dépôt de carbone, une interphase mixte est créée. Le pontage est assuré par la présence simultanée dans les couches à gradient de composition de grains de SiC et d’une phase carbonée. Les propriétés physico-chimiques et structurales des différents éléments des matrices ont été analysées et les différents comportements des fissures dans chacune des matrices ont été observés à la suite d’essais mécaniques. / The improvement of ceramic matrix toughness may be achieved through the presence of interfaces. Moreover, studies on a mother of pearl structure have shown the usefulness of mineral bridges between the layers. On the first part of this work, the Pompidou model was used for the selection of a bi-layered ceramic with an interface which is naturally favorable to crack deflection. SiC/pyC was taken as basic material for the interfaces study. Then, multilayered ceramic matrices (SiC/pyC)n (silicon carbide from CH3SiCl3/H2 mixture – pyC from propane) were fabricated using chemical vapor deposition (CVD). In the study, two bypass ways were proposed. On the one hand, a physical discontinuity exists between the different layers: elaboration parameters were optimized in order to develop both bulk layers and submicronic surface particles, acting as ceramic bypass. On the other hand, composition gradient films were developed between each SiC layers: by realizing carbon rich SiC layers, a mixed interphase was created. The presence of both SiC grains and carbon phases ensures the bypass structure. Physico-chemical and structural properties of multilayered ceramic matrices were analyzed and the crack propagation in each of them was observed following mechanical tests.
275

Ocular biomechanics of the anterior segment

Oehring, Daniela January 2018 (has links)
The thesis investigates methods of examining corneal biomechanics using non-contact tonometry and introduces novel techniques to investigate corneal material properties in vivo. A comprehensive systems analysis of the CorvisST (CST) and Ocular Response Analyser (ORA) was performed. Pressure sensors were used to characterisation the airflow produced by the CST and the ORA. Distinct differences were observed between the central airflow pressures between the two devices: the CST pressure was higher and of shorter duration. Scheimpflug high-speed imaging via the CST allowed components of the corneal deformation to be investigated and the development of a 3D deformation matrix (time, depth and spatial resolution) through tracing of the anterior and posterior corneal surface. Measures of whole eye movement (WEM) with CST were found to be robust. WEM demonstrated an asymmetric profile and a correction method was developed to address the corneal deformation matrix for this asymmetry. Novel methods for characterisation of intrinsic material characteristics of the cornea were developed using numerical and graphical analytical procedures. Application of these parameters was tested on enucleated porcine eyes across a wide range of manometry internal ocular pressure (MIOP). The dynamic E-Modulus was found to be most affected by MIOP change. To investigate the in vivo distribution and heterogeneity of the corneal biomechanics, a novel set-up allowed the mapping of corneal biomechanics across the cornea using the CST (central, paracentral, peripheral) and ORA (central, peripheral). Biometric and demographic grouping of subjects allowed detection of discriminating factors between individuals. The results suggest that the in vivo cornea of healthy human adults can be characterised as a viscoelastic, damped system for longitudinal strain and a highly oscillating system for lateral strain. The cornea is approximately homogenous for measures of rigidity and dynamic E-Modulus but other corneal material characteristics (longitudinal and lateral strain, hysteresis, damping and compressibility) demonstrated regional differences. The experimental design employed allowed for strict control of biometric and biomechanical intersubject variables, based on gold-standard techniques as well as newly-developed methods, thereby creating a normative database for future use.
276

Medidas de seção de choque de fusão para os sistemas ANTPOT. 12 C + ANTPOT. 63, 65 CU. / Section Measurements of shock melting for systems. 12 C + 63, 65 CU

Rocha, Carlos Antonio da 14 December 1987 (has links)
No presente trabalho é apresentado um conjunto de medidas de seção de choque do processo de fusão nuclear nos sistemas ANTPOT. 12 C + ANTPOT. 63, 65 CU, em um intervalo de energia correspondente à 0.91.8 vezes a barreira coulombiana. O método experimental utilizado foi a detecção dos resíduos de evaporação através da técnica de tempo de vôo, acoplado à um defletor eletrostático para separar as partículas provenientes do espalhamento elástico dos produtos de fusão. As vantagens e limitações do método são discutidas em detalhes. As funções de excitação de fusão dos sistemas citados foram analisadas via modelo de penetração de barreira unidimensional , utilizando vários potenciais nucleares. Dessa análise comprovou-se que a secção de choque de fusão é subestimada em energias em torno e abaixo da barreira coulombiana. Nesse sentido foi feito um cálculo, utilizando o código computacional CCFUS, que simula o acoplamento de canais, com a finalidade de descobrir quais canais contribuem para o processo de fusão nuclear em baixas energias. As seções de choque de fusão obtidas foram comparadas com outros sistemas - ANTPOT. 12 C + ANTPOT. 63, 65 CU.- que utilizam os mesmos núcleos-alvo. A comparação revelou que os sistemas ANTPOT. 12 C + ANTPOT. 63, 65 CU possuem o maior aumento de seção de choque de fusão subcoulombiana e esse fato pode estar relacionado à deformação estática do projétil. A comparação das distribuições da velocidade dos resíduos de evaporação para os dois de sistemas revelou um canal intenso para o sistema ANTPOT. 12 C + ANTPOT. 63 CU que não está presente para o outro sistema. / In this work we present cross-section measurements for nuclear fusion in the 12C+ 63,65 Cu system, at 12C energy range from 0.9 to 1.8 times the Coulomb barrier. In order to detect and to obtain the mass identification of the evaporation residues following the fusion process, the time of flight method was adopted in conjunction with an eletrostatic deflector capable of separating the evaporation residues from the beam particles. The limitation and advantadges of this method of measurement are discussed. The excitation functions for the above systems were analysed using the unidimensional barrier penetration model with different nuclear potentials. Theoretical fusion cross-section values obtained from this analysis were systematically smaller than our measured values, in the energy region below the Coulomb barrier. In order to discover which channel enhances the fusion cross-section in this region, a coupled channel calculation was performed, with the aid of CCFUS code. The experimental data for the above reactions were compared with the systems 12C+ 63,65 Cu, measured by our group. In this comparison, It was noted that the systems 12C+ 63,65 Cu have greater fusion cross section below the Coulomb barrier. This fact can be related to the static deformation of 12C. The comparison of velocity spectra of the evaporated residues for the two systems shows that 12C+63Cu has a strong reaction channel that was not present in the 12C+ 65Cu system.
277

Medidas de seção de choque de fusão para os sistemas ANTPOT. 12 C + ANTPOT. 63, 65 CU. / Section Measurements of shock melting for systems. 12 C + 63, 65 CU

Carlos Antonio da Rocha 14 December 1987 (has links)
No presente trabalho é apresentado um conjunto de medidas de seção de choque do processo de fusão nuclear nos sistemas ANTPOT. 12 C + ANTPOT. 63, 65 CU, em um intervalo de energia correspondente à 0.91.8 vezes a barreira coulombiana. O método experimental utilizado foi a detecção dos resíduos de evaporação através da técnica de tempo de vôo, acoplado à um defletor eletrostático para separar as partículas provenientes do espalhamento elástico dos produtos de fusão. As vantagens e limitações do método são discutidas em detalhes. As funções de excitação de fusão dos sistemas citados foram analisadas via modelo de penetração de barreira unidimensional , utilizando vários potenciais nucleares. Dessa análise comprovou-se que a secção de choque de fusão é subestimada em energias em torno e abaixo da barreira coulombiana. Nesse sentido foi feito um cálculo, utilizando o código computacional CCFUS, que simula o acoplamento de canais, com a finalidade de descobrir quais canais contribuem para o processo de fusão nuclear em baixas energias. As seções de choque de fusão obtidas foram comparadas com outros sistemas - ANTPOT. 12 C + ANTPOT. 63, 65 CU.- que utilizam os mesmos núcleos-alvo. A comparação revelou que os sistemas ANTPOT. 12 C + ANTPOT. 63, 65 CU possuem o maior aumento de seção de choque de fusão subcoulombiana e esse fato pode estar relacionado à deformação estática do projétil. A comparação das distribuições da velocidade dos resíduos de evaporação para os dois de sistemas revelou um canal intenso para o sistema ANTPOT. 12 C + ANTPOT. 63 CU que não está presente para o outro sistema. / In this work we present cross-section measurements for nuclear fusion in the 12C+ 63,65 Cu system, at 12C energy range from 0.9 to 1.8 times the Coulomb barrier. In order to detect and to obtain the mass identification of the evaporation residues following the fusion process, the time of flight method was adopted in conjunction with an eletrostatic deflector capable of separating the evaporation residues from the beam particles. The limitation and advantadges of this method of measurement are discussed. The excitation functions for the above systems were analysed using the unidimensional barrier penetration model with different nuclear potentials. Theoretical fusion cross-section values obtained from this analysis were systematically smaller than our measured values, in the energy region below the Coulomb barrier. In order to discover which channel enhances the fusion cross-section in this region, a coupled channel calculation was performed, with the aid of CCFUS code. The experimental data for the above reactions were compared with the systems 12C+ 63,65 Cu, measured by our group. In this comparison, It was noted that the systems 12C+ 63,65 Cu have greater fusion cross section below the Coulomb barrier. This fact can be related to the static deformation of 12C. The comparison of velocity spectra of the evaporated residues for the two systems shows that 12C+63Cu has a strong reaction channel that was not present in the 12C+ 65Cu system.
278

A study of swept and unswept normal shock wave/turbulent boundary layer interaction and control by piezoelectric flap actuation

Couldrick, Jonathan Stuart, Aerospace, Civil & Mechanical Engineering, Australian Defence Force Academy, UNSW January 2006 (has links)
The interaction of a shock wave with a boundary layer is a classic viscous/inviscid interaction problem that occurs over a wide range of high speed aerodynamic flows. For example, on transonic wings, in supersonic air intakes, in propelling nozzles at offdesign conditions and on deflected controls at supersonic/transonic speeds, to name a few. The transonic interaction takes place at Mach numbers typically between 1.1 and 1.5. On an aerofoil, its existence can cause problems that range from a mild increase in section drag to flow separation and buffeting. In the absence of separation the drag increase is predominantly due to wave drag, caused by a rise in entropy through the interaction. The control of the turbulent interaction as applied to a transonic aerofoil is addressed in this thesis. However, the work can equally be applied to the control of interaction for numerous other occurrences where a shock meets a turbulent boundary layer. It is assumed that, for both swept normal shock and unswept normal shock interactions, as long as the Mach number normal to the shock is the same, then the interaction, and therefore its control, should be the same. Numerous schemes have been suggested to control such interaction. However, they have generally been marred by the drag reduction obtained being negated by the additional drag due to the power requirements, for example the pumping power in the case of mass transfer and the drag of the devices in the case of vortex generators. A system of piezoelectrically controlled flaps is presented for the control of the interaction. The flaps would aeroelastically deflect due to the pressure difference created by the pressure rise across the shock and by piezoelectrically induced strains. The amount of deflection, and hence the mass flow through the plenum chamber, would control the interaction. It is proposed that the flaps will delay separation of the boundary layer whilst reducing wave drag and overcome the disadvantages of previous control methods. Active control can be utilised to optimise the effects of the boundary layer shock wave interaction as it would allow the ability to control the position of the control region around the original shock position, mass transfer rate and distribution. A number of design options were considered for the integration of the piezoelectric ceramic into the flap structure. These included the use of unimorphs, bimorphs and polymorphs, with the latter capable of being directly employed as the flap. Unimorphs, with an aluminium substrate, produce less deflection than bimorphs and multimorphs. However, they can withstand and overcome the pressure loads associated with SBLI control. For the current experiments, it was found that near optimal control of the swept and unswept shock wave boundary layer interactions was attained with flap deflections between 1mm and 3mm. However, to obtain the deflection required for optimal performance in a full scale situation, a more powerful piezoelectric actuator material is required than currently available. A theoretical model is developed to predict the effect of unimorph flap deflection on the displacement thickness growth angles, the leading shock angle and the triple point height. It is shown that optimal deflection for SBLI control is a trade-off between reducing the total pressure losses, which is implied with increasing the triple point height, and minimising the frictional losses.
279

Modeling Behaviour of Damaged Turbine Blades for Engine Health Diagnostics and Prognostics

Van Dyke, Jason 12 October 2011 (has links)
The reliability of modern gas turbine engines is largely due to careful damage tolerant design a method of structural design based on the assumption that flaws (cracks) exist in any structure and will continue to grow with usage. With proper monitoring, largely in the form of periodic inspections at conservative intervals reliability and safety is maintained. These methods while reliable can lead to the early retirement of some components and unforeseen failure if design assumptions fail to reflect reality. With improvements to sensor and computing technology there is a growing interest in a system that could continuously monitor the health of structural aircraft as well as forecast future damage accumulation in real-time. Through the use of two-dimensional and three-dimensional numerical modeling the initial goals and findings for this continued work include: (a) establishing measurable parameters directly linked to the health of the blade and (b) the feasibility of detecting accumulated damage to the structural material and thermal barrier coating as well as the onset of damage causing structural failure.
280

Modeling Behaviour of Damaged Turbine Blades for Engine Health Diagnostics and Prognostics

Van Dyke, Jason 12 October 2011 (has links)
The reliability of modern gas turbine engines is largely due to careful damage tolerant design a method of structural design based on the assumption that flaws (cracks) exist in any structure and will continue to grow with usage. With proper monitoring, largely in the form of periodic inspections at conservative intervals reliability and safety is maintained. These methods while reliable can lead to the early retirement of some components and unforeseen failure if design assumptions fail to reflect reality. With improvements to sensor and computing technology there is a growing interest in a system that could continuously monitor the health of structural aircraft as well as forecast future damage accumulation in real-time. Through the use of two-dimensional and three-dimensional numerical modeling the initial goals and findings for this continued work include: (a) establishing measurable parameters directly linked to the health of the blade and (b) the feasibility of detecting accumulated damage to the structural material and thermal barrier coating as well as the onset of damage causing structural failure.

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