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1
Cotela, Dalmau Jordi. "Applications of turbulence modeling in civil engineering." Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/383754.
Full textAbstract:
This thesis explores the use of stabilized finite element formulations for the incompressible Navier-Stokes equations to simulate turbulent flow problems. Turbulence is a challenging problem due to its complex and dynamic nature and its simulation if further complicated by the fact that it involves fluid motions at vastly different length and time scales, requiring fine meshes and long simulation times. A solution to this issue is turbulence modeling, in which only the large scale part of the solution is retained and the effect of smaller turbulent motions is represented by a model, which is generally dissipative in nature.
In the context of finite element simulations for fluids, a second problem is the apparition of numerical instabilities. These can be avoided by the use of stabilized formulations, in which the problem is modified to ensure that it has a stable solution. Since stabilization methods typically introduce numerical dissipation, the relation between numerical and physical dissipation plays a crucial role in the accuracy of turbulent flow simulations. We investigate this issue by studying the behavior of stabilized finite element formulations based on the Variational Multiscale framework and on Finite Calculus, analyzing the results they provide for well-known reference problems, with the final goal of obtaining a method that both ensures numerical stability and introduces physically correct turbulent dissipation.
Given that, even with the use of turbulence models, turbulent flow problems require significant computational resources, we also focused on programming and implementation aspects of finite element codes, specially in ensuring that our solver can perform efficiently on distributed memory architectures and high-performance computing clusters.
Finally, we have developed an adaptive mesh refinement technique to improve and optimize unstructured tetrahedral meshes, again with the goal of enabling the simulation of large turbulent flow problems. This technique combines an error estimator based on Variational Multiscale principles with a simple refinement procedure designed to work in a distributed memory context and we have applied it to the simulation of both turbulent and non-Newtonian flow problems.Aquesta tesi estudia la possibilitat d'utilitzar formulacions estabilitzades d'elements finits de les equacions de Navier-Stokes incompressibles per a la simulació de problemes de flux turbulent. La descripció de la turbulència és un repte, ja que es tracta d'un problema altament dinàmic i complex i la seva simulació numèrica es veu complicada pel fet que hi intervenen moviments de masses fluides amb dimensions i temps característics molt diferents i per tant requereix malles de càlcul molt fines i temps de simulació llargs. Això s'ha provat de resoldre mitjançant l'ús de models de turbulència, mantenint únicament la part de la solució de més gran escala i introduint un model de l'efecte dels moviments de petita escala, que acostuma a tenir un efecte dissipatiu. En el context de la simulació de fluids amb elements finits es planteja un segon problema amb l'aparició d'inestabilitats numèriques. Aquestes es poden evitar amb l'ús de formulacions estabilitzades, en les quals el problema es modifica per assegurar que tingui una solució estable. Ja que els mètodes d'estabilització típicament introdueixen dissipació addicional, la relació entre la dissipació numèrica i la dissipació física té un paper fonamental en la qualitat de la solució. Per investigar aquest fenomen hem estudiat el comportament de diferents formulacions d'elements finits basades en mètodes variacionals de subescala (VMS) i en el càlcul finit (FIC) en termes del seu comportament en la simulació de problemes turbulents de referència, amb l'objectiu final de trobar un mètode que a la vegada garanteixi l'estabilitat de la solució i introdueixi la dissipació turbulenta físicament necessària. Tenint en compte que, fins i tot quan s'utilitzen models de turbulència, la simulació de problemes de flux turbulent requereix molts recursos de càlcul, també hem estudiat aspectes de la implementació paral·lela de programes d'elements finits per tal de garantir que el nostre codi pot treure partit d'arquitectures de memòria distribuïda i servidors de càlcul d'alt rendiment. Finalment, hem desenvolupat una tècnica de refinament adaptatiu de malla que permeti millorar la qualitat de malles de càlcul tetraèdriques, novament amb la intenció de facilitar la simulació de grans problemes de flux turbulent. Aquesta tècnica combina un estimador d'error basat en els principis de la formulació variacional de subescala amb un procediment de refinament dissenyat per funcionar fàcilment en un context de memòria distribuïda i s'ha utilitzat per simular problemes de flux turbulent i no-Newtonià.
2
Gray, Derrick. "Applications of radiation physics in civil engineering." Thesis, University of Surrey, 1999. http://epubs.surrey.ac.uk/842854/.
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This thesis presents two separate applications of ionising radiation in Civil Engineering. The first is an investigation to determine the cement content of concrete using gamma-rays from the naturally occurring isotopes 238U, 232Th and their decay chains as well as 40K. Two sets of equations are derived and discussed. Spectra from cement, aggregate and concrete samples were made and the useful full energy peaks from the above sources identified. Two concrete samples were prepared using the same cement, but, containing two different aggregates: a granite based aggregate and a flint based aggregate. A third concrete sample was then prepared where the cement content was not initially known. Data from the first two tests was then used to determine the mass of cement used in the blind test. A great deal of valuable information has also been accrued concerning the interaction of statistical errors in the equations for the prediction of cement content. Spectra from four different cements were collected at regular intervals over a 24 month period and the variation in the activity of each cement over this period is discussed. The second section of this work presents an imaging technique that uses pair production annihilation photons to examine the state of steel reinforcement in concrete structures. Computer simulations along with experimental work have been used. The experimental work used a 226Ra needle as a photon source as it provided a range of gamma-rays with energies over the pair production threshold of 1022keV. A 31mm rebar with 30mm of concrete cover was successfully located during the experimental work. The data collected from the computer simulations has shown that the geometry and the material between the photon source, rebar and detector is of great importance.
3
Hope, Victoria. "Applications of seismic transmission tomography in civil engineering." Thesis, University of Surrey, 1993. http://epubs.surrey.ac.uk/842729/.
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The principles of tomography are well-established, and geotomography has been in use for several decades. Seismic tomography has previously been used principally in the oil and nuclear industries, but it has occasionally been applied in civil engineering site investigation (SI). The technique can provide a qualitative or a quantitative representation of the distribution of the seismic velocity properties within a surveyed region. Seismic tomography has been successfully used to image, for example, zones of fracturing. The technique has been less successful when used to detect cavities. This thesis presents a theoretical and experimental examination of the usefulness - or otherwise - of seismic tomography in SI. It is found that geotomography has a role to play when one is interested in, for example, general subsurface variability. An explanation is offered for the low success rate of cavity detection surveys utilizing seismic velocity tomography. It is shown that, of the numerous and diverse fields of application of the tomographic method, geotomography offers what is, perhaps, the most inherently ill-posed form of the reconstruction problem. Significant difficulties are encountered because, in general, measurements can be acquired from only a restricted set of positions. Additional problems are introduced through the use of seismic wave energy, which follows hard-to-predict routes across the surveyed zone. Observational errors lead to inconsistencies within a tomographic system. In consequence, the geotomographic reconstruction problem is typically under-determined, inconsistent and non-linear. An heuristic method of reconstructing seismic velocity tomograms from typical field data is developed and presented.
4
Zorrilla, Martínez Rubén. "Towards the virtual wind tunnel for civil engineering applications." Doctoral thesis, Universitat Politècnica de Catalunya, 2020. http://hdl.handle.net/10803/671768.
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This thesis develops a numerical tool (the Virtual Wind Tunnel, VWT) for the resolution of problems involving fluid flow around structures. Due to the limitations that traditional methods may have in this context, the VWT is based on the use of fixed mesh technologies (CutFEM-type) combined with an implicit representation of the embedded bodies.
One of the main contributions of the thesis is the use of such fixed mesh methods to solve lightweight thin-walled structures problems. Hence, two embedded formulations capable of representing the flow around bodies with and without internal volume are proposed. The first one results in a simpler implementation and lower computational effort but can only represent a slip behavior of the wall. The second one gets rid of such limitation by including a Nitsche imposition of the Navier-slip condition, thus allowing modelling any wall behavior as a wall law would do.
The applicability range of the VWT includes the fluid–structure interaction problem (FSI). To that purpose an improvement for the boundary condition imposition of the FM-ALE algorithm mesh motion problem is also proposed. Moreover, the implementation, which has been conceived to be easily extended to any other coupled problem, is also treated.
The validation of the technologies within the VWT includes multiple theoretical test cases as well as feasible industrial applications. Among these, the FSI analysis of a 4-point tent during a strong wind episode deserves to be highlighted as it showcases the achievement of the initial objective of the thesis.En esta tesis se desarrolla una herramienta numérica (el Virtual Wind Tunnel, VWT) para la resolución de problemas que involucran el flujo de un fluido alrededor de una estructura. Debido a las limitaciones que los métodos tradicionales pueden tener en este contexto, el VWT se basa en el empleo de técnicas de malla fija (tipo CutFEM) combinadas con una descripción implícita de los cuerpos embebidos. Una de las principales contribuciones de la tesis es el empleo de dichos métodos de malla fija para resolver problemas de estructuras ligeras de pared delgada. Así pues, se proponen dos formulaciones embebidas capaces de representar el flujo alrededor de un cuerpo con o sin volumen interno. La primera de ellas resulta en una implementación más sencilla así como en un menor coste computacional pero únicamente puede reprentar un comportamiento deslizante de la pared. La segunda elimina esta limitación incluyendo una imposición mediante el método de Nitsche de la condición de Navier-slip, permitiendo así modelar cualquier comportamiento del mismo modo que lo haría una ley de pared. El rango de aplicabilidad del VWT incluye el problema de interacción fluido¿estructura (FSI). A tal propósito se plantea una mejora para la imposición de las condiciones de contorno del problema de movimiento de la malla del algoritmo FM-ALE. Asimismo, también se hace especial hincapié en la implementación, que ha sido concebida para ser fácilmente extensible a cualquier otro problema acoplado. La validación de las tecnologías implementadas en el VWT incluyen múltiples casos teóricos así como posibles aplicaciones industriales. Entre éstas se destaca el análisis FSI de una 4-point tent durante un episodio de viento severo ya que demuestra la consecución del objetivo inicial de la tesis.
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Stone, Gregory M. "Beneficial Reuse of Corrugated Paperboard in Civil Engineering Applications." DigitalCommons@CalPoly, 2012. https://digitalcommons.calpoly.edu/theses/691.
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Abstract
Beneficial Reuse of Corrugated Paperboard in Civil Engineering Applications
Gregory Michael Stone
An investigation was conducted to explore the potential for reuse of corrugated paperboard. Corrugated paperboard represents a large fraction of the municipal solid waste generated and discarded in the United States. Alternative applications for reuse can provide a significant benefit by reducing the volume of waste being disposed and by reducing the use of raw materials. Four civil engineering applications were examined for potential beneficial reuse of corrugated paperboard: slurry trench construction, vertical drilling, directional drilling, and controlled low strength materials (CLSM).
For the purpose of this project, corrugated paperboard was pulped and added to bentonite slurry or CLSM mixtures. Bentonite slurry mixtures were tested for viscosity, density, filtrate loss, and permeability. The behavior of the bentonite slurries was greatly influenced by interaction and interlocking of corrugate fibers; in general resulting in increased viscosity, filtrate loss, and permeability and decreased density. CLSM mixtures were tested for flow consistency, unit weight, air content, and compressive strength. CLSM mixtures prepared with corrugated paperboard showed an increased water demand due to high absorption of the corrugate. The higher water content was a significant factor contributing to decreased unit weight and compressive strength. CLSM mixtures containing corrugated paperboard also exhibited increased air contents, possibly due to entrapment of air within the corrugate pulp.
Corrugated paperboard was used to successfully replace up to 27% of bentonite for slurry trench applications, 60% of bentonite for vertical drilling applications, and 59% of bentonite for directional drilling applications while maintaining acceptable engineering properties. For CLSM mixtures up to 1% of fine aggregate was replaced with corrugated paperboard while maintaining satisfactory engineering properties.
Incorporation of corrugated paper board into bentonite slurry, CLSM, and drilling fluid applications provides a viable option for beneficial reuse.
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Ledoux, Antoine M. Eng Massachusetts Institute of Technology. "Theory of piezoelectric materials and their applications in civil engineering." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/66839.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 39).
The goal of this thesis is to explore ways of harvesting energy from a building. To be more specific, the conversion of mechanical energy into electrical energy using piezoelectric materials is studied. Applications of piezoelectric materials as actuators are also explored, with particular interest in the question: what is the maximum moment that an actuator, whose energy comes from piezoelectricity, can develop when attached to a beam. As a piezoelectric material cannot generate much energy, and often requires amplification, the goal is to optimize the circuit linked to the piezoelectric material to obtain as much power as possible.
by Antoine Ledoux.
M.Eng.
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Winistoerfer, Andreas Urs. "Development of non-laminated advanced composite straps for civil engineering applications." Thesis, University of Warwick, 1999. http://wrap.warwick.ac.uk/109734/.
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The focus of this thesis has been the feasibility of a novel load transfer concept for a carbon fibre reinforced plastic (CFRP) tendon system using non-laminated pin-loaded straps. The principle of these straps is that, as the tensile load increases, the relative slip between the layers produces a more uniform strain distribution in the layers leading to a higher load carrying capacity than when the laminate is fully consolidated (i.e. a laminated strap). This principle has been shown to occur by observing relative displacement between individual layers and strain measurements. Such components could be used for post strengthening purposes of existing structures. They have the potential to alleviate the current problems associated with the corrosion of externally applied steel reinforcement. Furthermore, the low density of CFRP’s in combination with appropriate design procedures can provide a cost competitive solution. This advantage of choosing a non-metallic material is strengthened when whole life cycle costs are considered since composites are expected to outlive the conventional repair materials. One objective of the project was to develop a tape material with continuous parallel fibres at low cost. At the start of the project no material available was suitable in terms of cost or quality. To drive the cost of the material down, thin lamina tapes with a thermoplastic matrix were considered. The various manufacturing processes for thermoplastic prepreg tape were reviewed and the powder impregnation process was found to meet the project's specifications. This method can produce high quality prepreg at a higher production rate compared to pultrusion with a thermosetting matrix. Sulzer Innotec Ltd. had an existing aqueous powder impregnation facility for research and development purposes. The author collaborated with the company to make specific modifications to the facility with the objective of improving material quality. This was achieved towards the end of the project, and in the thesis this material is referred to as Tape IV. Preliminary development work was carried out throughout the duration of the project to characterise five thermoplastic materials. Two practical connection methods where developed to anchor the final outer layer in the non-laminated strap option. It was found that the clamping method was superior to the fusion bonding method; both methods will, however, find applications. A new manufacturing process for laminated pin-loaded straps was developed and is reported. The author used MARC K6.2, a commercial finite element software, to predict the stress concentrations in the region where the strap makes contact with the steel pin. The difficulties associated with the advanced numerical modelling included contact and friction. The required results from MARC K6.2 were highly dependent on a sliding velocity parameter for which no accurate value was known. Because of the lack of rigor in the formulation of the finite element model, the stress concentrations predicted could not be used to optimise strap detailing. For completeness the MARC K6.2 modelling is described and the results reported. To exploit the technology, research and development work will be needed, and the thesis shows where there are gaps in our knowledge and understanding.
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Dong, Biqin. "Cement-based piezoelectric ceramic composites for sensor applications in civil engineering /." View abstract or full-text, 2005. http://library.ust.hk/cgi/db/thesis.pl?CIVL%202005%20DONG.
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Davey, Scott W. "A foundational investigation of vinyl ester / cenosphere composite materials for civil and structural engineering." University of Southern Queensland, Faculty of Engineering and Surveying, 2004. http://eprints.usq.edu.au/archive/00003180/.
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[Abstract]: With the increasing use of fibre reinforced polymer (FRP) composites in civil engineering structures, there is a growing realisation of the need to develop newstructural systems which can utilise the unique characteristics of these materials in a more efficient and economical manner. In many instances this will require thedevelopment of new materials tailored to address the unique performance and economic parameters of mainstream construction. Over recent years, researchers at the University of Southern Queensland have pioneeredthe use of a new type of particulate filled polymer core material which greatly improves the robustness and cost effectiveness of FRP structural systems. These compositematerials are composed of small hollow spherical fillers (microspheres) in a thermosetting polymer matrix. Initial research into these materials, including theirfeasibility in prototype structural elements, have shown these materials to have major potential for widespread application in structural composite systems.One of the most promising classes of these materials investigated to date are vinyl ester / cenosphere composites, which utilise cenospheres derived from fly ash in a vinyl ester matrix. Previously reported studies into these materials have been restricted to initialsurveys of material behaviour which sought to identify key parameters in achieving desired performance outcomes in the composite. This dissertation presents the first in-depth investigation of these materials specifically as a core material option for civil infrastructure applications. The particular focus of this work is on the relationship of the vinyl ester matrix to the characteristics of the resultingcomposite. Several key matrix parameters were identified and assessed as to their influence on cure characteristics, fabrication operations, mechanical properties and theretention of such properties under elevated service temperatures. The outcomes of this work have significantly improved the understanding of matrix influences on the behaviour of these composite systems and have been drawn together to provide a number of recommendations on the application of this new technology to new structural systems.
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Edeskär, Tommy. "Use of tyre shreds in civil engineering applications : technical and environmental properties." Doctoral thesis, Luleå tekniska universitet, Geoteknologi, 2006. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16907.
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End-of-life tyres are a disposal problem regarding the large volumes produced every year. Tyre shreds are primarily produced to reduce the transportation volumes of end-of-life tyres after collection. Within the European Union, there is a ban for landfilling tyre material in order to reduce the total landfilling volumes and to encourage recycling measures. Until recently the main disposal option has been energy recovery in industrial processes. However, legislation acts has recently been taken in the European Union to encourage recycling and recovery of end-of-life-tyres and re-use of tyre materials in construction works is listed as one disposal option.Tyre shreds possess interesting technical properties that could be beneficially used in civil engineering applications. Some characteristic properties of tyre shred materials are the low density, high elasticity, low stiffness, high drainage capacity and high thermal insulation capacity. These properties open up possibilities for utilisation of the material in an innovative manner.The overall aim of this thesis work has been to describe and evaluate tyre shreds as a civil engineering construction material from environmental and technical point of view. The thesis work has included laboratory tests and full scale field tests to investigate technical and environmental properties of tyre shreds and to investigate the tyre shred material behaviour in a real road construction. Furthermore, the state-of-the-art knowledge in the area has also been analysed and presented.In the laboratory studies technical properties focused on compaction and compression behaviour of tyre shreds have been investigated. In a field study of a built road, tyre shreds has been tested and evaluated, during four years, as lightweight fill and frost insulation material. Environmental properties of tyre shreds, mainly leaching characteristics, have been studied in laboratory tests and monitored in two full scale field tests.Based on the results in the laboratory studies a model is proposed for evaluation of stressstrain properties and prediction of compression behaviour. Recommendations for construction works and pavement design are suggested based on the road construction field study results.Conclusions regarding the studied leaching properties of tyre shreds, based on the laboratory tests and the field monitoring, are that zinc and iron are the metals mainly released and that the release of the studied organic compounds, i.e. PAH and phenols, are low. From an environmental point-of-view focus should be moved from PAH-compounds towards other compounds that are more interesting from mobility perspective and lack of knowledge. It is concluded from this thesis work that PAH is not a pollution problem in the area of use of tyre material covered by this work.Applications where tyre shreds have been successfully utilised as construction material, are e.g. as draining layers in landfills and as material in trotting tracks and paddocks. The utilisation of the material in trotting tracks and paddocks is especially interesting since the unique elasticity of the material is utilised. The potential of utilising tyre shreds in civil engineering construction is big. Since the available amounts of material is limited there is a possibility to direct the use of tyre shreds to the most favourable applications of tyre shreds and still solve the disposal problem of end-of-life tyres.Uttjänta däck är ett avsättningsproblem avseende de stora volymerna som produceras varje år. Däckklipp produceras främst med avseende på att reducera transportvolymen av insamlade däck. Inom EU har det införts ett förbud mot att deponera däck och däckklipp för att dels reducera den totala volymen avfall som deponeras och dels för att uppmuntra återvinning av däckmaterial. Den huvudsakliga avsättningen för uttjänta däck har fram tills nu varit energiåtervinning, främst inom cementindustrin.Däckklipp har intressanta tekniska egenskaper som fördelaktigt kan utnyttjas i anläggningstekniska tillämpningar. Karakteristiska egenskaper för däckklipp är låg densitet, hög elasticitet, låg styvhet, hög dränerande och hög värmeisolerande förmåga. Kombinationen av dessa egenskaper möjliggör tekniskt innovativa lösningar inom anläggningsbyggande.Det övergripande syftet med avhandlingen har varit att beskriva och utvärdera däckklipp som ett anläggningsmaterial ur både teknisk och miljömässig synvinkel. Arbetet har inkluderat både laboratorie- och fullskaleförsök för att utreda tekniska, miljö- och anläggningstekniska egenskaper. Vidare har det aktuella kunskapsläget om däckklipp som anläggningsmaterial utvärderats och presenterats.I laboratorieförsök har tekniska egenskaper med fokus mot packnings- och kompressionsegenskaper för däckklipp undersökts. I ett fältförsök har en vägkonstruktion med däckklipp som lättfyllnads- och tjälisoleringsmaterial byggts och utvärderats under fyra år. I laboratorieförsök har lakningsegenskaper för däckmaterial och miljöövervakningsprogram för tre olika konstruktioner utvärderats.Baserat på laboratoriestudier har en utvärderingsmodell för spännings-töjningsegenskaper och beräkning av kompression föreslagits. Rekommendationer för anläggningsteknik och vägdimensionering presenteras baserat på utvärderingen av vägkonstruktionen.Slutsatser baserat på lakningsstudierna i laboratoriemiljö och utvärderingen av miljöövervakningsprogrammen för fältkonstruktionerna är att de metaller som främst lakar ut är zink och järn och att lakningen av de studerade organiska föreningarna, d.v.s. PAH och fenoler, är låg. Från ett miljöperspektiv bör fokus flyttas från PAH mot organiska föreningar som har hög mobilitet och där kunskapsläget är lågt. Slutsatsen i detta arbete är att PAH-föreningar inte utgör ett föroreningsspridningsproblem för konstruktioner med däckklipp.Tillämpningar där däckklipp framgångsrikt har använts som konstruktionsmaterial är t.ex. i dräneringslager i deponier, i travbanor, och i paddockar. Användningen av däckklipp i travbanor och paddockar är särskilt intressant eftersom belastningen på hästarnas ligament kan minskas.Potentialen att använda däckklipp som ett anläggningsmaterial är stor. Eftersom tillgången är begränsad finns det en möjlighet att styra användningen till de lösningar där materialet används optimalt, både tekniskt och miljömässigt, och ändå avsätta all tillgänglig volym uttjänta däck.
Godkänd; 2006; 20070108 (mlk)
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Wodzicki, Christopher Peter 1979. "Applications of CAD/CAM technology to avant-garde structural engineering." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29419.
Full textAbstract:
Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.Leaf 46 blank.
Includes bibliographical references (leaves 44-45).
Over the last decade improvements in design technology has taken grand steps in changing the way we build the structures of tomorrow. Conventional drafting software like AutoCAD and Microstation are being challenged by tools that go beyond the two dimensional representational abilities of paper documentation and replacing it with complex three dimensional virtual construction files that are more comprehensible and offer more flexibility with respect to design and also in terms of inter-professional communication. My interest's lie in the new dialectic emerging between architects and fabricators, who ironically sit at opposite ends of the construction spectrum yet are now collaborating with the help of modern-day software. I envision these new tools as being pivotal in both reassigning the roles of design and creating a more seamless construction process. It is this modified construction process that I intend to explore through this thesis.
by Christopher Peter Wodzicki.
M.Eng.
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Luo, Wuben. "A comparative assessment of Dempster-Shafer and Bayesian belief in civil engineering applications." Thesis, University of British Columbia, 1988. http://hdl.handle.net/2429/28500.
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The Bayesian theory has long been the predominate method in dealing with uncertainties in civil engineering practice including water resources engineering. However, it imposes unnecessary restrictive requirements on inferential problems. Concerns thus arise about the effectiveness of using Bayesian theory in dealing with more general inferential problems. The recently developed Dempster-Shafer theory appears to be able to surmount the limitations of Bayesian theory. The new theory was originally proposed as a pure mathematical theory. A reasonable amount of work has been done in trying to adopt this new theory in practice, most of this work being related to inexact inference in expert systems and all of the work still remaining in the fundamental stage. The purpose of this research is first to compare the two theories and second to try to apply Dempster-Shafer theory in solving real problems in water resources engineering.
In comparing Bayesian and Dempster-Shafer theory, the equivalent situation between these two theories under a special situation is discussed first. The divergence of results from Dempster-Shafer and Bayesian approaches under more general situations where Bayesian theory is unsatisfactory is then examined. Following this, the conceptual difference between the two theories is argued. Also discussed in the first part of this research is the issue of dealing with evidence including classifying sources of evidence and expressing them through belief functions.
In attempting to adopt Dempster-Shafer theory in engineering practice, the Dempster-Shafer decision theory, i.e. the application of Dempster-Shafer theory within the framework of conventional decision theory, is introduced. The application of this new decision theory is demonstrated through a water resources engineering design example.Applied Science, Faculty of
Civil Engineering, Department of
Graduate
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Dang, Hoang Kien. "The development of a combined finite-discrete element model for quasistatic geotechnical engineering applications." Thesis, McGill University, 2011. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=103642.
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The mechanics of soil erosion around buried structures is a challenging soil-structure interaction problem. It involves progressive particle movement and interaction with an existing subsurface structure. Using standard finite element method (FEM) and continuum mechanics to simulate the soil erosion process (that involves large soil displacement and discontinuities in the soil matrix) has proven to be inefficient. Continuum methods do not allow for the realistic simulation of the gradual soil loss into the structure. Discrete element method (DEM), on the other hand, has proven to be suitable for such analysis, however, it involves large amount of calculation to simulate a real problem. This thesis is devoted to develop an efficient method that allows the analysis of the above problem considering both the micro and macro scale features of the problem. The research results have been published in refereed journals and conference proceedings amounting to 4 journal papers and 2 conference papers. These papers are compiled to produce 7 chapters and 2 appendices in this manuscript-based thesis. The investigation of the effects of erosion voids around existing tunnels is first conducted using conventional finite element method (FEM) to illustrate the limitation of the FEM in modelling problems involving large deformation and discontinuities. The rest of the thesis is devoted to describe the development of the combined finite-discrete element method. A simple and effective algorithm to generate realistic initial soil conditions required for the discrete element method has been developed. Using the developed algorithm, the calibration procedure needed to determine the properties of the discrete elements is only necessary for a small initial sample (e.g. grain size distribution, internal friction angle). The final packing is then generated based on the initial sample exhibiting the same macro behaviour. In the combined method, the soil in the area experiencing large displacements or discontinuities is modelled using discrete elements whereas the rest is modelled using finite elements. The integration scheme used in the FEM has been investigated and modified to suit the combined finite-discrete element. Dynamic relaxation technique with automatic time step control has been developed to optimize the performance of the scheme. Finally, interface has been introduced to bridge the finite and discrete element domains. By adopting a suitable damping scheme for each domain, the numerical stability of the combined method has been maintained. The developed method has been calibrated using benchmark problems and used to investigate the effects of particle loss induced around an existing tunnel lining on the stress distribution in the lining structure. Conclusions and recommendations are made regarding the three dimensional effect of soil deterioration on the structural integrity of existing tunnels in soft ground.La mécanique de l'érosion aux alentours de structures enfouies est un problème compliqué d'interaction sol-structure. Elle implique le mouvement progressif de particules et l'interaction avec la structure souterraine existante. L'utilisation de la méthode des éléments finis standard (EMF) et de la mécanique continue pour stimuler le processus d'érosion du sol (qu'implique des larges déplacements et discontinuités dans la matrice du sol) ont été démontré être inefficientes. La méthode continue ne permette pas des simulations réalistes des pertes graduelles vers la structure. Par contre, la méthode des éléments discrets (MED) a été démontré être adéquate pour ces analyses, c, pour évaluer un problème réel elle implique une grande quantité de calculs. Cette thèse est consacrée à développer une méthode qui permette l'analyse du problème précédent en considérant les aspects du problème à micro et à macro échelle. Les résultats on était publiés dans des journaux et actes de conférence totalisant 4 articles de journaux et deux articles de conférence. Ces articles sont compilés dans les 7 chapitres et 2 annexes de cette thèse manuscript-based. L'étude des effets des vides d'érosion autour de tunnels existants a été premièrement réalisée en utilisant la méthode des éléments finis conventionnelle (MEF) pour illustrer sa limitation à modéliser des problèmes impliquant des larges déformations et discontinuités. En suite, la thèse est dédiée à décrire le développement de la méthode des éléments finis-discrets combinée. Un algorithme simple et effectif pour générer des conditions initiales de sol réalistes a été développé pour la méthode des éléments discrets. En utilisant l'algorithme développé, la procédure de calibration nécessaire pour déterminer les propriétés des éléments discrets, tels que la distribution de la taille du grain ou l'angle interne de friction, est seulement nécessaire pour un petit échantillon initial. Le paquet final est alors généré en se basant sur l'échantillon initial qui manifeste le même macro-comportement. Dans la méthode combinée le sol de la zone qui expérimente des larges déplacements ou discontinuités est modélisé en utilisant des éléments discrets, tandis que le restant est modélisé en utilisant des éléments finis. Le schéma utilisé dans la MEF a été étudié et modifié pour convenir à l'élément fini-discret. Finalement, l'interface a été présenté pour connecter les domaines fini et discret. En adoptant un schéma d'amortissement convenable pour chaque domaine, la stabilité numérique de la méthode combinée a été préservée. La méthode développée a été calibrée en utilisant des problèmes modèles et utilisée pour étudier l'effet des pertes de particules causée autour d'un tunnel existant. Des conclusions et recommandations sont faites concernant les effets tridimensionnels de la détérioration du sol sur l'intégrité structurelle des tunnels existants dans le sol meuble.
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Elbadrawi, Hesham R. "Temporal gis applications in public transit planning and management." FIU Digital Commons, 1996. http://digitalcommons.fiu.edu/etd/3130.
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Geographic Information Systems (GISs) provide a powerful framework for various tasks of transit management such as planning, performance evaluation, and marketing. GIS may be used to solve complex planning problems, assist in operations planning, and meet other management and operational needs. However, due to the changing nature of transit planning and operational data, transit planners and operators need to analyze the data over time, which requires a temporal GIS that is capable of storing, manipulating, and analyzing changes with respect to both time and space.
Temporal GIS will allow planners and transit operators to analyze data within a certain time frame defined by the user and compare it to those in another time frame or to the current available data. This ability will improve prediction of future transit demand, evaluation of past operations, and analysis of day-to-day operations and management.
This research entails the study of the applications of temporal GIS in transit planning and management. Transit management tasks are examined to identify those that may potentially benefit from temporal GIS. Their process, data needed, and possible applications are investigated. Examples of temporal GIS applications have been developed.
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Carlson, Randi A. (Randi Aileen) 1971. "Triblock polyampholyte solutions for environmental applications." Thesis, Massachusetts Institute of Technology, 1998. http://hdl.handle.net/1721.1/47597.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Chemical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998.Includes bibliographical references (leaves 55-60).
by Randi A. Carlson.
S.M.
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Eckstein, Jonathan. "Splitting methods for monotone operators with applications to parallel optimization." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/14356.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1989.Archives copy bound in 1 v.
Includes bibliographical references (leaves 308-323).
by Jonathan Eckstein.
Ph.D.
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Leitch, Katherine K. (Katherine Kristen). "Structure glass technology : systems and applications." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/31200.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.Includes bibliographical references (leaves 70-73).
Glass cannot compete with steel in terms of strength or durability, but it is the only structural material that offers the highly sought after qualities of translucency and transparency. The use of glass has evolved from purely decorative or architectural to structural, encouraging glass technologies to advance concurrently with increased demand. As a result, contemporary methods used to produce structural glass provide excellent strength characteristics, particularly after treatments including annealing, tempering, and heat-strengthening, which reduce its vulnerability to cracking and sudden brittle failure. Its modulus of elasticity is roughly equal to that of aluminum-greater than both wood and concrete-but doesn't allow any plastic deformation. Lamination dramatically improves both the strength and durability of glass by joining strengthened layers of glass using resin or a polyvinyl butyral foil. No comprehensive design code is currently available to aid in the design of structural glass members. The behavior of glass is examined through a variety of structural applications including beams, columns, walls, roofs and floors, and domes. Case studies are explored to underscore the technical principles discussed for each structural glass element utilized in place of more traditional building materials.
by Katherine K. Leitch.
M.Eng.
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Miller, S. T. "Remote sensing applications to flood hydrology in Belize." Thesis, Aston University, 1986. http://publications.aston.ac.uk/14242/.
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The research compares the usefullness of four remote sensing information sources, these being LANDSAT photographic prints, LANDSAT computer compatible tapes, Metric Camera and SIR-A photographic prints. These sources provide evaluations of the catchment characteristics of the Belize and Sibun river basins in Central America. Map evaluations at 1:250,000 scale are compared to the results of the same scale, remotely sensed information sources. The values of catchment characteristics for both maps and LANDSAT prints are used in multiple regression analysis, providing flood flow formulae, after investigations to provide a suitable dependent variable discharge series are made for short term records. The use of all remotely sensed information sources in providing evaluations of catchment characteristics IS discussed. LANDSAT prints and computer compatible tapes of a post flood scene are used to estimate flood distributions and volumes. These are compared to values obtained from unit hydrograph analysis, using the dependent discharge series and evaluate the probable losses from the Belize river to the floodplain, thereby assessing the accuracy of LANDSAT estimates. Information relating to flood behaviour is discussed in terms of basic image presentation as well as image processing. A cost analysis of the purchase and use of all materials is provided. Conclusions of the research indicate that LANDSAT print material may provide information suitable for regression analysis at levels of accuracy as great as those of topographic maps, that the differing information sources are uniquely applicable and that accurate estimates of flood volumes may be determined even by post flood imagery.
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Kimura, Kichiro. "Flat plate buffeting in yawed wind with possible applications to bridges." Thesis, University of Ottawa (Canada), 1992. http://hdl.handle.net/10393/7792.
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The wind resistant design of bridges becomes more realistic if the directionality of wind is incorporated into the analysis. However, the necessary information about the bridge response under wind with yaw angle, namely, under a wind not perpendicular to the bridge longitudinal axis, has not been obtained to this date. This thesis is concerned with the buffeting response of cantilever models under yawed turbulent wind. The employed cantilever models can be thought as a simple version of a cable-stayed bridge under construction which is known to be extremely vulnerable to the wind action. It has been also indicated that these structures reveal relatively large response under yawed wind. Models with various cross-sections were tested under different flow conditions and the buffeting response was measured taking the yaw angle as a parameter. The response was mostly in the first vertical bending mode. For the flat plate cross-section models, the effect of the model width was found to be most significant. The wider the model was, the larger the response was found to be under the wind from the free end direction. Even the largest response was sometimes observed under the wind parallel to the model axis from free end direction. A simple response prediction by taking the cosine component of the wind velocity, which has been used from time to time, was found to give generally smaller values than the actual model response. The conventional buffeting analysis was modified so that the response of the cantilever structure under yawed wind can be predicted. Wind velocity components normal to the side and the end of the model were taken as the effective wind velocities, and the response was calculated separately corresponding to each effective wind velocity. The modified buffeting analysis was applied to the flat plate cross-section models. The analytical results generally explained the experimental findings regarding the effect of the wind yaw angle.
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QUAN, GAO. "An Innovative Sensing Technology to Measure Thin Interfaces for Geotechnical Applications." Case Western Reserve University School of Graduate Studies / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=case1457987819.
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Song, Xiaodong. "Titanium vaulted structures for orthopaedic applications." Thesis, University of Liverpool, 2013. http://livrepository.liverpool.ac.uk/13335/.
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Medical devices are used to recreate damaged or diseased joints and also to restore pain reduced mobility to patients. Devices such as hip and knee implants are fixed to the host bone by use of acrylic bone cement or by a press-fit interference technique. The surface of the press fit implants may be roughened, but non-porous, which allows new bone to form on the surface, or they may be porous to encourage bone growth into the structure. Traditionally implants are produced by machining, casting or forging, before applying any coatings that are required. More recently Additive Manufacturing (AM) techniques such as Electron Beam Manufacturing (EBM) and Selective Laser Melting (SLM) have attracted interest as they may be able to create the whole device in one operation. This thesis describes the research carried out to produce “Vaulted Structure (VS)” as a method for creating specific porosity with increased strength in porous medical devices. Unit cell structures (Wire frames) are inherently weak because of the struts. It was proposed that VSs, constructed of platelets, would have a higher specific strength and therefore extend the range of available properties while still maintaining a structure that resembles cancellous bone, a structure preferred by surgeons. The creation of a VS begins with a computer model of the object to be created. This is then surrounded by an axis aligned bounding box, a box that has edges parallel to the x, y and z directions and just encloses the object. The bounding box is then voxelised, so it consists of many smaller cubic boxes, these boxes being the size of the required structure. The VS is then constructed by creating holed platelets on some of the surfaces of the smaller boxes, with these platelets being randomly deformed if required. The structure within the bounding box is then trimmed to the boundary of the required structure, this being accomplished using a rapid technique developed during this project. To allow manufacture of the components, the structure is sliced to create a suitable format for the SLM. By using SLM in combination with these new novel structures, a wide range of possible properties and morphologies can be generated, these being controlled by the cell size, hole size, thickness of the platelet and the level of randomisation. ii A range of structures with different morphologies were produced and mechanically tested in compression. It was found that a percentage randomisation of more than 60% and a cell aspect ratio of 1:1:2, produced isotropic mechanical behaviour, while other structures produced very different behaviour. It was also observed that the failure mode in compression could be controlled by the degree of randomisation and this is discussed in the thesis. A property that is important in the medical device industry is the look of the component as this affects up take by surgeons. The preferred structures are ones that look like cancellous bone and the new structures created here match both the look and mechanical properties of this material, but with the added advantage that it is possible, by modifying the control variables, to match the structure to cancellous bone from different aged patients. The research presented in this thesis considers the inter-relationship between the process parameters, architecture, properties of the structures and why these inter relationships occur. The research presented here extends knowledge of how to create these novel material/structure combinations, how to tailor them to a given purpose and by predicting behaviour in software produce the most suitable properties for a given medical device without extensive testing.
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Ahmed, Shamim. "Transaction and version management in object-oriented database management systems for collaborative engineering applications." Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13854.
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Levante, Riccardo. "Data Management and Virtual Reality Applications of BIM models." Thesis, KTH, Byggnadsteknik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-233189.
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Nowadays new digital technologies play an important role in the AEC sector, which are goingthrough a significantly changing period. In this process BIM represent the main character,revolutionizing the traditional way of working in the main operative phases: Design,Construction and Maintenance. However, having all these aspects under a uniquemethodology can brings several problems without a strong framework to regulate the wholeprocedure. The huge quantity of information, as well as the high number of involved people,are the main weak points, that can become the main strong points when Facility Managementis involved in the process. In this scenario this work will analyse a real project located inGenova (Italy), seeing as a complex structure as an hospital can be regulated through the BIMmethodology.The thesis will focus on two fundamental aspects of the new construction methodology: DataManagement and Virtual Reality. The first part aims to analyse correlation between BIM andits information, focusing also on the study case, proposing operative solution through the BIMsoftware Revit and the visual programming toll Dynamo. The second part will showadvantage integrating virtual reality technologies in the AEC sector, showing how build aninteractive virtual simulation using the game engine software Unity based on our study case.Through this work we have seen the importance of new technologies for the future ofConstruction Industry, showing how important is the sharing information involving alwaysmore people into the process, particularly for complex structures.
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Lam, Carlos. "Properties and applications of polymer support fluids in geotechnical engineering." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:ba0867c6-eb42-4b9a-a400-b464749855c5.
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Synthetic polymer fluids have been used as an alternative to conventional bentonite slurries for the excavation of foundation elements over the last two decades. Thus far their use has excited polarised views in the industry – some construction professionals avoid using them after hearing ‘horror stories’ about past failures whereas others believe that they are the future of support fluids because of the many benefits that they can offer. This situation has been found to be mainly due to a lack of understanding of what polymers really are and their properties. To address this issue, the various polymer products currently available in the market have been categorised based on their intended functions, and the fundamental properties of some of them have been characterised. The research showed that significant difference exists between polymers even of the same chemical family. Based on a series of rheological experiments, it was found that the properties of polymer fluids are highly dependent on the governing shear rate, time, and a range of site dependent factors. The research also showed that the current procedure for the interpretation of viscosity data is incorrect. After an analysis of the properties of currently available polymers, the latter part of the thesis describes a field trial carried out at a site in Stratford, East London. The aims of the trial were twofold: to compare the performance between piles constructed using bentonite and polymer fluids, and to assess the effect of extended pile bore open time for pile bores supported by polymers. From the results, it was found that the polymer piles showed much stiffer load–settlement response than the bentonite pile, and that a pile bore open time of up to 26 h had no adverse effect on the pile performance. The load test results have been carefully back-analysed using a range of methods. It was found that, compared to their bentonite counterparts, polymer fluids can improve the interface shearing resistance with Thanet Sand and the shear modulus of the Lambeth clay.
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Borsari, Claudio. "Microsimulation of transportation systems - theory and applications." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/3711/.
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Rahbee, Adam B. "Rail transit operations analysis : framework and applications." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84305.
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Farkas, András 1965. "Dynamic shortest path algorithms for IVHS applications." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12400.
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Choi, Chi Chi. "Coupled Hydrologic And Hydraulic Models And Applications." Thesis, University of Iowa, 2013. https://ir.uiowa.edu/etd/4955.
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Tayebi, Alireza [Verfasser]. "Development of a new method for aggregate quality control in civil engineering applications / Alireza Tayebi." Clausthal-Zellerfeld : Universitätsbibliothek Clausthal, 2015. http://d-nb.info/1080270302/34.
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Ureel, Scott Daniel. "Concepts Used to Analyze and Determine Rock Slope Stability for Mining & Civil Engineering Applications." Diss., The University of Arizona, 2014. http://hdl.handle.net/10150/325211.
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Slope stability plays an important role in rock engineering. During the design, construction and post design phases of rock slope stability, engineers and geologists need to pay close attention to the rock conditions within the rock slope to prevent slope failures, protect employees and maintain economic profit. This dissertation is based on a general four step procedure to construct and maintain rock slope stability with confidence. These four steps include field investigations, material testing and rock strength database, slope modelling and slope monitoring. The author provides past, present and alternatives methods for each step for the introduced slope stability procedure. Specific topics within each step are investigated displaying results, recommendations and conclusions. Step one involves data collection during field investigations for rock slope design. Orientation of rock core during drilling programs has become extremely pertinent and important for slope stability and underground mining operations. Orientation is needed to provide essential data to describe the structure and properties of discontinuities encountered during the design process to understand favourable and unfavourable conditions within a rock slope and underground openings. This chapter examines and discusses the limitations and benefits of four methods of obtaining borehole discontinuity orientations from drilling programs including clay-imprint, ACT I, II, III Reflex, EZY-MARK, and OBI/ABI Televiewer systems. Results, recommendations and conclusions are provided in this study. During step two to maintain rock slope stability, a rock strength database was created and used to correlate and compare RQD values to rock abrasion, shear strength and other rock characterization methods. Rock abrasion plays a significant role in geotechnical design, tunneling operations and the safety of foundations from scour; however, rock abrasion can be used to develop higher confidence in important parameters such as RQD and hardness. More rock abrasivity research is needed to provide a more accurate and compatible method for all subsurface material properties used in mining and civil engineering projects. This report will provide simple correlations relating abrasion resistance to RQD, UCS, Geological Strength Index (GSI) and Rock Mass Rating (RMR) of metamorphic rock. Results, discussions and conclusions are provided. Step 3 to determine rock slope stability entails utilizing computer modeling to predict failure conditions and wear rock mass properties. Computer modeling and slope monitoring for rock slopes have become essential to assess factor of safety (FOS) values to predict slope instability and estimate potential failure. When utilizing computer models, the limit equilibrium method (LEM) provides FOS values according to force and moment equilibrium; the shear strength reduction (SSR) technique calculates FOS using stress- and deformation-based analyses. Currently, both methods are prevalent in the engineering industry and applied by geotechnical engineers to analyze and determine stability in rock slopes for mining and civil engineering projects. Slope modeling techniques are then used to observe slope conditions and predict when slope failure may occur (FOS = 1.0). Comparison, results and conclusions are presented. Lastly, the dissertation (step 4: slope monitoring) will investigate past studies of FOS comparisons, review calculation methods and provide procedures and results using remote sensing data. The main objective of the dissertation is to provide engineers with essential information needed to ensure high confidence in factor of safety predictions and how alternative methods can be utilized. Recommendations, future research and conclusions regarding FOS and slope monitoring are provided within the dissertation.
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Tong, Qi. "A Multiscale Micromophic Molecular Dynamics| Theory and Applications." Thesis, University of California, Berkeley, 2016. http://pqdtopen.proquest.com/#viewpdf?dispub=10150814.
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Multiscale simulation is a long standing dream in computational physics and materials. The motivation is natural: each single-scale model has its deficiencies. For example, microscale models such as Molecular Dynamics are limited to size in space and time; macroscale models such as Finite Element Method find difficulty recovering some fundamental physical phenomena such as materials defects. Simulations across scales are challenging because quantities in different scales have distinct properties. Mechanism needs to be harnessed to translate the information. Cross-scale communication is a typical two-way message passing: bottom-up and top down. Bottom-up approach is relatively straightforward, where statistical theory or homogenization is used to collect lower-scale information and interpret it in higher levels. On the other hand, top-down approach requires physical insights. Specifically, in a mechanical system, top-down message passing can be the response of the molecular system when macroscale boundary conditions such as distributed load are enforced.
In this work, we reveal an intrinsic multiscale structure in solid materials. A “supercell” is introduced as a cluster of particles. Compare with “material point” in continuum mechanics, the “supercell” has internal degrees of freedom, which makes it equivalent to molecular systems. By introducing different force fields, we derive the dynamical equations for the different scales in the structure. The systematic multiscale framework solves the issue of top-down message passing by including quantities from different scales and connecting them in a uniform dynamical framework. We discuss the technical aspects in implementing the theory, i.e. constraints of the variables, integrators and temperature control. Numerical example of phase transition are presented to validate the theory, including bulk Nickel lattice under displacement and traction boundary conditions and Nickel nanowire with traction. Furthermore, based on the developed multiscale theory, we establish a computational model to achieve efficiency in realistic multiscale simulations. The model includes three parts: atomistic region, macro region and transition zone. Atomistic region is where physical details are desired and is simulated by Molecular Dynamics. Macro region only concerns macroscale deformable behaviors of solid materials, which can be calculated by various models depending on the problem of interests. We choose state-based peridynamics in this work as a demonstration. The essential part is the transition zone which is responsible for translating messages across different domains. The “supercell” developed in the previous theory is employed as a transition element to carry those different messages. With solid theoretic foundation, the cross-scale message translation is clearly characterized. We also construct a filter to solve the issue of high-frequency wave reflection. Examples of 1-D and 2-D wave propagations are presented to demonstrate the procedure of cross-scale transition and the effect of the filter.
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Al-Malack, Muhammad Hassan. "Applications of dynamic membranes to crossflow microfiltration of secondary effluent." Thesis, University of Newcastle Upon Tyne, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.335944.
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Harper, Lee Thomas. "Discontinuous carbon fibre composites for automotive applications." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10246/.
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Increasingly stringent emissions targets are encouraging vehicle manufacturers to prioritise reduction of vehicle mass. The falling cost of carbon fibre is increasing the viability of lightweight carbon-based body panel systems across a broad range of production volumes. In the present work an automated process has been developed for the manufacture of random fibre preforms at medium volume production levels (30-50,000ppa). This thesis seeks to understand the influence of key microstructural parameters on the mechanical and physical properties of carbon fibre laminates produced by directed fibre preforming. The principal parameters studied are fibre length, tow filament count and laminate thickness. A statistical process simulation has been developed to predict preform density variation and the results are compared with experimental tensile properties. Experimental studies have shown that there is a notable reduction in areal density variation and consequently an increase in tensile properties with shorter fibres (115mm to 6mm) and thicker laminates (1.5mm to 4mm for a constant volume fraction). Shorter lengths improved preform coverage and gave higher tensile strength, whilst thicker laminates reduced the presence of unreinforced areas which cause stress concentrations. Tow filamentisation has been induced by pneumatic means to reduce the mean filament count and maximise the mechanical performance when using inexpensive, 24K bundles. By maximising the level of filamentisation both stiffness and strength can be increased by 20% and 45% respectively. An analytical stiffness model is presented to predict the effect of tow filament count on the in-plane elastic constants. Filament count and out-of-plane fibre orientation distributions are determined from optical microscopy and are incorporated into a multi-level Mori-Tanaka based model. Predictions are within 8% of the experimental data for laminates containing large fibre bundles and 10% for laminates with highly filamentised bundles. An expression for critical bundle length has been developed for more accurate strength prediction, based on the number of filaments within the bundle. Experimental results confirm that the critical tow length is proportional to the tow filament count. Directed fibre preforming has been benchmarked against other competing processes in respect of mechanical properties, weight saving potential and cost. A full-scale demonstrator component has been manufactured using a variety of carbon composite solutions, which can all provide 40 to 50% weight saving for an equivalent bending stiffness to steel and greatly improved dent resistance. Directed fibre preforming has shown great promise for both semi-structural and structural components for medium volume applications, particularly when aligned fibres are introduced. The results from this work can be directly scaled for industrial application to provide a cost effective, lightweight alternative to steel.
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Burling, Luke Donald. "Novel phosphate glasses for bone regeneration applications." Thesis, University of Nottingham, 2006. http://eprints.nottingham.ac.uk/10161/.
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Phosphate glass with additions of sodium, magnesium and/or calcium were investigated for their potential to be used as the reinforcing phase in a completely degradable long fibre composite. Glasses were prepared from phosphate salts as opposed to oxides and melted under air in platinum/gold crucibles. The effect of cation addition on the material properties and biocompatibility was investigated. Glasses were characterised using a number of complimentary techniques, including: XRD, XPS, DSC, IR and EDX. The findings from these techniques were used to explain the observed thermal and dissolution properties. The thermal and dissolution properties were found to be dependant on both the thermal history and composition of the phosphate glass. For a phosphate glass with low cation content, the temperature and length of time held at that temperature increased the Tg by 10 C for sodium phosphate glass and slightly improved the durability of sodium phosphate glass containing 10 mol.% MgHPO4, as phosphate chain growth was greater under those conditions. Addition of divalent cations increased the Tg of phosphate glasses from 295 C for sodium phosphate glass by up to 150 C with the addition of 50 mol.% MgHPO4. The dissolution rate was decreased exponentially with the addition of calcium phosphate or magnesium phosphate to sodium phosphate glass. Rates as low as 1x10-7 g/(cm2.h) were achieved with the addition of 50 mol.% divalent cation phosphates. The divalent cations inhibited phosphate chain growth but formed a new network based upon divalent cation/non bridging oxygen cross-links. These cross-links were found to exert greater influence over the material properties then the phosphate chain length. Cell culture assays were used to establish the biocompatibility of phosphate glasses with different compositions. Preliminary tests were conducted with craniofacial derived osteoblast like cells cultured on glass surfaces. Initial assays performed showed that the most durable glasses sustained the greatest amount of proliferation and differentiation over a seven day period. The most promising glass compositions, 40 Ca, 40 Mg, 30 Mg/20 Ca and 20 Mg/30 Ca, and were selected for longer term osteoblast culture and short term macrophage culture. Long term osteoblast culture showed that cells were able to attach, spread and proliferate throughout the 28 day duration of the study. Assays performed on the culture showed that cells were differentiating, producing specific osteoblast markers for each of the three differentiation phases of proliferation, matrix maturation and mineralisation. ECM production and mineralisation was confirmed on all surfaces tested via type I collagen staining and alizarin red staining respectively. Over the 28 day period, it was found that the composition did not have a significant effect on the production of the osteoblast markers, namely alkaline phosphatase, collagen, osteocalcin and mineral deposition. Immunological studies show that macrophages are not activated by the presence of phosphate glass. This demonstrated that phosphate glass has shown potential for use a biomaterial.
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Carugo, Dario. "Development of microfluidic systems for therapeutic applications." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/348835/.
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The development of a microfluidic-based strategy is presented for investigating the functional behaviour of hydrogel spherical beads which are employed in the clinic as embolic agents and drug delivery systems for the treatment of hypervascularised tumours and arteriovenous malformations. For this purpose, biomimetic microchannel networks were designed and fabricated by micromilling technology. Microdevices architecture reproduced characteristic features of microcirculatory arteriolar systems. The miniaturisation allowed for coupling with microscope-based technology and in situ visualisation of particles/cells behaviour. The flow dynamics of red blood cells (RBCs) suspensions within the aforementioned biomimetic microfluidic devices was investigated, by using in-house developed micro-Particle Image Velocimetry (μ-PIV) methods and image analysis techniques to quantify fluid velocity fields, cell-free layer width and RBCs spatial distribution. Results demonstrated the potential of the developed microfluidic devices for reliably reproducing peculiar properties of RBCs flow behaviour within human microcirculatory systems, including the relationship between cell-depletion layer width and microvessel diameter, and the dependence of RBCs distribution on the local Reynolds number. These findings opened the way for the application of the developed microfluidic devices as a biomimetic platform for investigating the performance of embolic beads. The flow behaviour of hydrogel beads within biomimetic microfluidic environments was investigated by adopting a two-steps approach, in which beads hydrodynamics was firstly studied within straight microchannels (Step I) and subsequently within network-like microchannel constructs (Step II). For this purpose, microscopy-based analysis techniques were developed in order to quantify bead radial position and axial velocity. Results demonstrated that bead flow behaviour depended on a complex interplay between the governing physical parameters, which included fluid rheology, fluid inertia (i.e., Reynolds number) and particle relative dimension (i.e., degree of confinement). Notably, it has been demonstrated that for a given combination of such parameters beads underwent oscillatory dynamics which have been thoroughly characterised experimentally. Further, beads partitioning at bifurcations, penetration efficacy and spatial location of the embolic events within biomimetic microchannel networks were investigated. The experimental observations presented here can provide relevant insight into the mechanisms governing the spatial distribution of embolic beads within tumour vascular systems. Finally, the spatiotemporal dynamics of drug elution from hydrogel embolic beads was investigated within the aforementioned biomimetic microchannel networks. Both on-chip analysis and off-chip analysis techniques were developed for quantifying the kinetics of drug elution and the amount of eluted drug from single embolic beads. Results revealed that drug elution from hydrogel embolic beads depended on the local hydrodynamics at the embolic site and on the location of the embolic event within the vascular network (i.e., proximal or distal embolisation). A numerical model was developed in order to better understand the role played by flow dynamics environment on the spatial distribution of the eluted drug at biomimetic bifurcations. In conclusion, the results of this study have established that microfluidics could be potentially employed as an alternative to animal models for investigating the performance and functional behaviour of hydrogel beads used in cancer therapy and targeted drug delivery.
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Imtiaz, Azeem. "Solid-state microwave heating for biomedical applications." Thesis, Cardiff University, 2015. http://orca.cf.ac.uk/73775/.
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The research conducted in this thesis aims to develop an efficient microwave delivery system employing miniature resonant microwave cavities, targeted at compact, flexible and ideally field-deployable microwave-assisted diagnostic healthcare applications. The system comprises a power amplifier as a solid-state microwave source and a load - as a single mode cavity resonator to hold the sample. The compactness of the practical microwave delivery system relies on the direct integration of the sample-holding cavity resonator to the power amplifier and inclusion of the built-in directional coupler for power measurements. The solid state power transistors used in this research (10W-LDMOS, 10W-GaN) were provided by the sponsoring company NXP Inc. In practical microwave delivery applications, the impedance environment of the cavity resonators change significantly, and this thesis shows how this can be systematically utilized to present the optimal loading conditions to the transistor by simply designing the series delay lines. This load transfer technique, which critically can be achieved without employing bulky, lossy and physically larger output matching networks, allows high performance of the power amplifier to be achieved through waveform engineering at the intrinsic plane of the transistor. Starting with the impedance observation of a rectangular cavity, using only series delay lines allowed the practical demonstration of the high power and high efficiency fully integrated inverse class-F (F-1) power amplifier. Temperature is an important factor in a microwave heating and delivery system as it changes the impedance environment of the cavity resonator. This natural change in both cavity and sample temperature can be accommodated through simplified series matching lines and the microwave heating system capable of working over substantial bandwidth was again practically demonstrated. The inclusion of the coupler maintained the compactness of the system. In the practical situations envisaged, the microwave delivery system needs to accommodate natural variation between sample volumes and consistencies for heating. The experimental work considered the heating of different sample volumes ii of water, and characterizing the change in the natural impedance environment of the cavity as a result. It was shown how the natural impedance variation can not only be accommodated, but also exploited, allowing ‘continuous’, high-efficiency performance to be achieved while processing a wide range of sample volumes. Specifically, using only transistor package parasitic, the impedance of the cavity itself together with a single series microstrip transmission line allows a continuous class-F-1 mode loading condition to be identified. Through different experiments, the microwave delivery systems with high-performance are demonstrated which are compact, flexible and efficient over operational bandwidth of the cavity resonators.
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Zhu, Jian. "SPIHT image coding : analysis, improvements and applications." Thesis, University of Warwick, 2002. http://wrap.warwick.ac.uk/88817/.
Full textAbstract:
Image compression plays an important role in image storage and transmission. In the popular Internet applications and mobile communications, image coding is required to be not only efficient but also scalable. Recent wavelet techniques provide a way for efficient and scalable image coding. SPIHT (set partitioning in hierarchical trees) is such an algorithm based on wavelet transform. This thesis analyses and improves the SPIHT algorithm. The preliminary part of the thesis investigates two-dimensional multi-resolution decomposition for image coding using the wavelet transform, which is reviewed and analysed systematically. The wavelet transform is implemented using filter banks, and the z-domain proofs are given for the key implementation steps. A scheme of wavelet transform for arbitrarily sized images is proposed. The statistical properties of the wavelet coefficients (being the output of the wavelet transform) are explored for natural images. The energy in the transform domain is localised and highly concentrated on the low-resolution subband. The wavelet coefficients are DC-biased, and the gravity centre of most octave-segmented value sections (which are relevant to the binary bit-planes) is offset by approximately one eighth of the section range from the geometrical centre. The intra-subband correlation coefficients are the largest, followed by the inter-level correlation coefficients in the middle then the trivial inter-subband correlation coefficients on the same resolution level. The statistical properties reveal the success of the SPIHT algorithm, and lead to further improvements. The subsequent parts of the thesis examine the SPIHT algorithm. The concepts of successive approximation quantisation and ordered bit-plane coding are highlighted. The procedure of SPIHT image coding is demonstrated with a simple example. A solution for arbitrarily sized images is proposed. Seven measures are proposed to improve the SPIHT algorithm. Three DC-level shifting schemes are discussed, and the one subtracting the geometrical centre in the image domain is selected in the thesis. The virtual trees are introduced to hold more wavelet coefficients in each of the initial sets. A scheme is proposed to reduce the redundancy in the coding bit-stream by omitting the predictable symbols. The quantisation of wavelet coefficients is offset by one eighth from the geometrical centre. A pre-processing technique is proposed to speed up the judgement of the significance of trees, and a smoothing is imposed on the magnitude of the wavelet coefficients during the pre-processing for lossy image coding. The optimisation of arithmetic coding is also discussed. Experimental results show that these improvements to SPIHT get a significant performance gain. The running time is reduced by up to a half. The PSNR (peak signal to noise ratio) is improved a lot at very low bit rates, up to 12 dB in the extreme case. Moderate improvements are also made at high bit rates. The SPIHT algorithm is applied to loss less image coding. Various wavelet transforms are evaluated for lossless SPIHT image coding. Experimental results show that the interpolating transform (4, 4) and the S+P transform (2+2, 2) are the best for natural images among the transforms used, the interpolating transform (4, 2) is the best for CT images, and the bi-orthogonal transform (9, 7) is always the worst. Content-based lossless coding of a CT head image is presented in the thesis, using segmentation and SPIHT. Although the performance gain is limited in the experiments, it shows the potential advantage of content-based image coding.
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Morshed, Md Abu. "Early carbonation curing of fresh concrete and its applications in precast concrete production." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=117115.
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Carbonation curing of fresh concrete at early age and the feasibility to integrate the technology into precast concrete production were investigated. It was found that equilibrium of relative humidity between ambient environment and interior concretes was not possible to achieve in early carbonation of fresh concrete even with preconditioning. Instead, the degree of carbonation was dominated more by the water content in the concrete than by its internal humidity. A fan-drying precondition seemed to be necessary and practically feasible to justify the water content in industry scale application. The process was applied to the production of precast lightweight concrete panels and normal weight hollow core concrete slabs. The lightweight aggregates were utilized as internal water reservoirs to balance the moisture equilibrium during preconditioning, carbonation reaction and subsequent hydration. Water movement from the internal reservoirs was postulated by resistivity measurements; and was further verified in terms of CO2 uptake, strength development, plastic shrinkage compensation and alkalinity regain. A near-surface diffusion carbonation curing was developed to partially replace the heat curing in hollow-core concrete slab production. The hollow core slab so produced had shown much better strength than the hydration reference or by the heat curing alone, with reduced porosity and less vulnerability to delayed ettringite formation. Besides the technical benefits, CO2 sequestration potential is an added value to the process. An average 15% CO2 uptake could lead to sequestration of approximately 10,000 tonnes of CO2 per year by precast hollow-core concrete plants in Canada alone.La carbonatation du béton frais effectuée à son plus jeune âge, ainsi que la possibilité de potentiellement intégrer cette technologie dans la production du béton préfabriqué a été analysé dans cette étude. Il a été constaté que l'équilibre de l'humidité relative entre l'intérieur du béton et le milieu ambiant dans lequel il se trouve n'était pas possible à établir au début du processus préalable de la cure du béton frais par carbonatation. De plus, la quantité d'eau présente affecte le degré de carbonatation bien plus que l'humidité relative interne. Le séchage préalable du béton par ventilateurs d'es trouvé nécessaire et pratique afin de justifier la présence d'eau à l'échelle industrielle. Le processus a été utilisé pour la production des panneaux de béton préfabriqué de poids léger, ainsi que pour les dalles de béton alvéolées de poids ordinaire. L'utilisation des granulats légers en tant que réservoirs d'eau internes a servi à balancer l'humidité d'équilibre durant le déroulement de tout le processus, voir du début de l'étape préalable, durant la période de carbonatation jusqu'à l'hydratation postérieure. La circulation d'eau des réservoirs internes est due aux mesures de résistivité; ceci a été validé en termes de l'étendu de carbonatation, du développement de la résistance mécanique, par la compensation du rétrécissement plastique, et par le regain de l'alcalinité. De plus, la carbonatation dynamique près de la surface du béton a été conçue afin de partiellement remplacer le procédé d'étuvage compris dans la production de dalles de bétons alvéolées. Ce type de dalles a démontré un bien meilleur niveau de résistance mécanique que celui atteint par les dalles ordinairement hydratées ou par les dalles étuvées. En plus d'avoir une meilleure résistance, ces dalles possèdent moins de porosité et sont moins vulnérables au développement tardif d'ettringite. Outre les avantages techniques, la possibilité de séquestration du CO2 est un gain ajouté au procédé. En moyenne, un contenu de 15% de CO2 dans la production Canadienne des dalles de bétons alvéolées pourrait séquestrer 10,000 tonnes de CO2 chaque année.
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Guergachi, Abdelaziz. "Uncertainty management in the activated sludge process, innovative applications of computational learning theory." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0016/NQ58278.pdf.
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Shen, Su 1973. "Logistics service network design : models, algorithms, and applications." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/29424.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.Includes bibliographical references (leaves 177-186).
Service network design is critical to the profitability of express shipment carriers. In this thesis, we consider two challenging problems associated with designing networks for express shipment service. The first problem is to design an integrated network for premium and deferred services simultaneously. Related existing models adapted to this problem are intractable for realistic instances of this problem: computer memory requirements and solution times are excessive. We introduce a disaggregate information-enhanced column generation approach for this problem that reduces the number of variables to be considered in the integer program from hundreds of thousands to only thousands, allowing us to solve previously unsolvable problem instances. The second problem is to determine the express package service network design in its entirety, including aircraft routings, fleet assignments, and package flow routings, including hub assignments. Existing models applied to this problem have weak associated linear programming bounds and hence, fail to produce quality feasible solutions. For example, for a small network design problem instance it takes days to produce a feasible solution that is provably near- optimal using the best performing existing model. To overcome these tractability challenges, we introduce a new model, referred to as the gateway cover and flow formulation. Applying our new formulation to the same network design instance, it takes only minutes to find an optimal solution.
(cont.) Applying our disaggregate information-enhanced column generation approach and gateway cover and flow formulation and solution approach to the network design problems of a large express package service provider, we demonstrate tens of millions of dollars in potential annual operating cost savings and reductions in the numbers of aircraft needed to perform the service. Moreover, we illustrate that, though designed for tactical planning, our new model and solution approach can provide insights for strategic decision-making, such as hub opening/closure, hub capacity expansion, and fleet composition and size.
by Su Shen.
Ph.D.
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Doyle, Timothy Patton. "Multicriteria multistakeholder decision analysis : applications to transportation planning." Thesis, Massachusetts Institute of Technology, 2016. http://hdl.handle.net/1721.1/104116.
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Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2016.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 227-231).
Due to their magnitude and longevity, transportation investments can determine the long term success or failure of a transportation system. Thus, it is vital for decision-makers to have deep understanding of the alternatives available before they chose to invest. In this thesis, we examine the current state of the practice for transportation investment decisions. We draw upon the literature and this existing state of the practice to develop a new decision aid which we believe is an improvement over existing aids. We then apply this new decision aid to a transportation investment decision facing the East Japan Railway Company (JR East) and draw conclusions about the usefulness of our new tool. Our decision aid, the CLIOSjre Process, is designed to help decision-makers compare multiple alternatives and make an informed transportation investment decision. The process examines the decision from multiple perspectives where each of these perspectives represents one of the priorities of the decision-maker. By considering each priority separately, the CLIOSjre Process provides a detailed understanding of each alternative. The CLIOSjre Process also combines these individual evaluations into a single overall evaluation of each alternative. This overall evaluation provides the decision-maker with an actionable ranking of the alternatives. In combination, these perspective-specific and overall evaluations of each alternative provide a detailed and holistic understanding of the decision facing the decision-maker. Unlike many other decision aids, the CLIOSjre Process accounts for both the multistakeholder nature of transportation investments and the uncertainty inherent to these decisions. The multifaceted nature of the CLIOSjre Process examines each alternative from multiple perspectives. This approach better facilitates negotiation between stakeholders. In addition, the CLIOSjre Process formally identifies and addresses uncertainty in the analysis - the primary source of risk in transportation investment decisions. Thus, the CLIOSjre Process is a unique multicriteria, multistakeholder decision aid which addresses uncertainty. We hope that this thesis provides the reader with a better understanding of the application, challenges, and opportunities of multicriteria multistakeholder decision aids.
by Timothy Patton Doyle.
S.M. in Transportation
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Lochan, Rajiv Chellappa. "Long haul fleet assignment : models, methods and applications." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36616.
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Chon, Sok-Hyon 1974. "Structural applications and feasibility of prestressed steel members." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/84296.
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Thesis (M.Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.Includes bibliographical references (leaves 46-47).
by Sok-Hyon Chon (a.k.a. Ken Tuttle)
M.Eng.
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Yang, Qi 1963. "A microscopic traffic simulation model for IVHS applications." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12177.
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Danaf, Mazen(Mazen Salah). "Online discrete choice models : applications in smart mobility." Thesis, Massachusetts Institute of Technology, 2019. https://hdl.handle.net/1721.1/123227.
Full textAbstract:
Thesis: Ph. D. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2019Cataloged from PDF version of thesis.
Includes bibliographical references (pages 100-108).
Discrete choice models have been widely applied in different fields to better understand behavior and forecast market shares. Because of their ability to capture taste heterogeneity, logit mixture models have gained increasing interest among researchers and practitioners. However, since the estimation of these models is computationally expensive, their applications have been limited to offline contexts. On the other hand, online applications (such as recommender systems) require users' preferences to be updated frequently and dynamically. The objective of this dissertation is to develop a methodology for estimating discrete choice models online, while accounting for inter- and intra-consumer heterogeneity. An offline-online framework is proposed to update individual-specific parameters after each choice using Bayesian estimation.
The online estimator is computationally efficient, as it uses the data of the individual making the choice only in updating his/her individual preferences. Periodically, data from multiple individuals are pooled, and population parameters are updated offline. Online estimation allows for new and innovative applications of discrete choice models such as personalized recommendations, dynamic personalized pricing, and real-time individual forecasting. This methodology subsumes the utility-based advantages of discrete choice models and the personalization capabilities of common recommendation techniques by making use of all the available data including user-specific, item specific, and contextual variables. In order to enhance online learning, two extensions are proposed to the logit mixture model with inter- and intra-consumer heterogeneity.
In the first extension, socio-demographic variables and contextual variables are used to model systematic inter- and intra-consumer taste heterogeneity respectively. In the second extension, a latent class model is used to allow for more flexibility in modeling the inter- and intra-consumer mixing distributions. Finally, the online estimation methodology is applied to Tripod, an app-based travel advisor that aims to incentivize and shift travelers' behavior towards more sustainable alternatives. Stated preferences data are collected in the Greater Boston Area and used to estimate the population parameters, which are then used by the app in online estimation. Using the collected data, a large number of synthetic users is simulated, and the recommendation system is tested over several days, and under different scenarios. The results show that the average hit-rate generally increases over time as we learn individual preferences and population parameters.
"funding from the Advanced Research Projects Agency-Energy (ARPA-E), Ford, the Civil and Environmental Engineering Department at MIT, and the MIT-Singapore Alliance for Research and Technology (SMART)"--Page 5
by Mazen Danaf.
Ph. D. in Transportation
Ph.D.inTransportation Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
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Hou, Xianxu. "An investigation of deep learning for image processing applications." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/52056/.
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Significant strides have been made in computer vision over the past few years due to the recent development in deep learning, especially deep convolutional neural networks (CNNs). Based on the advances in GPU computing, innovative model architectures and large-scale dataset, CNNs have become the workhorse behind the state of the art performance for most computer vision tasks. For instance, the most advanced deep CNNs are able to achieve and even surpass human-level performance in image classification tasks. Deep CNNs have demonstrated the ability to learn very powerful image features or representations in a supervised manner. However, in spite of the impressive performance, it is still very difficult to interpret and understand the learned deep features when compared to traditional human-crafted ones. It is not very clear what has been learned in the deep features and how to apply them to other tasks like traditional image processing problems. In this thesis, we focus on exploring deep features extracted from pretrained deep convolutional neural networks, based on which we develop new techniques to tackle different traditional image processing problems. First we consider the task to quickly filter out irrelevant information in an image. In particular, we develop a method for exploiting object specific channel (OSC) from pretrained deep CNNs in which neurons are activated by the presence of specific objects in the input image. Building on the basic OSC features and use face detection as a specific example, we introduce a multi-scale approach to constructing robust face heatmaps for rapidly filtering out non-face regions thus significantly improving search efficiency for potential face candidates. Finally we develop a simple and compact face detectors in unconstrained settings with state of the art performance. Second we turn to the task to produce visually pleasing images. We investigate two generative models, variational autoencoder (VAE) and generative adversarial network (GAN), and propose to construct objective functions to train generative models by incorporating pretrained deep CNNs. As a result, high quality face images can be generated with realistic facial parts like clear nose, mouth as well as the tiny texture of hair. Moreover, the learned latent vectors demonstrate the capability of capturing conceptual and semantic information of facial images, which can be used to achieve state of the art performance in facial attribute prediction. Third we consider image information augmentation and reduction tasks. We propose a deep feature consistent principle to measure the similarity between two images in feature space. Based on this principle, we investigate several traditional image processing problems for both image information augmentation (companding and inverse halftoning) and reduction (downscaling, decolorization and HDR tone mapping). The experiments demonstrate the effectiveness of deep learning based solutions to solve these traditional low-level image processing problems. These approaches enjoy many advantages of neural network models such as easy to use and deploy, end-to-end training as a single learning problem without hand-crafted features. Last we investigate objective methods for measuring perceptual image quality and propose a new deep feature based image quality assessment (DFB-IQA) index by measuring the inconsistency between the distorted image and the reference image in feature space. The proposed DFB-IQA index performs very well and behave consistently with subjective mean opinion scores when applied to distorted images created from a variety of different types of distortions. Our works contribute to a growing literature that demonstrates the power of deep learning in solving traditional signal processing problems and advance the state of the art on different tasks.
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Sharp, Zachary B. "Applications of Computational Fluid Dynamics in Flow Measurement and Meter Design." DigitalCommons@USU, 2016. https://digitalcommons.usu.edu/etd/4887.
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Computational Fluid Dynamics is a very effective tool for understanding fluid flow and predicting how flow will respond to different boundary conditions. With this knowledge, the focus of this research is applying computational fluid dynamics to problems dealing with flow measurement in closed conduits using differential producing flow meters like Venturis. After discussion with many meter manufactures and a thorough literature review, specific areas of research were determined which will contribute to better understanding of differential producers and will add to the limited literature available on such meters. This research will present the findings of computational fluid dynamics coupled with laboratory data in the following areas:
1. Determine the effects of sudden pipe wall offsets on Venturi flow meters. This research includes both the effects of the pipe wall offset on the meter discharge coefficient as well as determining the minimum distance between the offset and the Venturi so that there is no longer any effect on meter performance. It also shows how well computational fluid dynamics can predict Venturi discharge coefficients via comparison to laboratory data.
2. Investigate the design of pressure recovery cones on different Venturi flow meter designs including determining the optimal angle of recover cone required to minimize permanent pressure loss.
3. Investigate truncated recovery cones such that a meter can be manufactured using a shorter length. This research also includes determining the best way to truncate the meter to minimize head loss while not changing the flow metering capability of the flow meter.
This research will be CFD based with laboratory data used to calibrate and validate the CFD results.
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Zhao, Weizhong. "Optical fibre high temperature sensors and their applications." Thesis, City University London, 2011. http://openaccess.city.ac.uk/1190/.
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Tam, Heng-Kong. "Some applications of Cam-clay in numerical analysis." Thesis, City University London, 1992. http://openaccess.city.ac.uk/7885/.
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The research described in this thesis investigated some applications of Cam-clay in numerical analyses. Single element analysis using the program CASIS was conducted to model undrained and drained triaxial compression tests to investigate the relative importance of the critical state soil parameters and streis history on the calculated soil behaviour. The values of these parameters covered the range of most commonly occurring natural soils. The investigation was extended to finite element modelling of plate loading tests using the computer program CRISP to examine the relative importance of the critical state soil parameters and stress history on the calculated undrained plate-soil behaviour. The capability of finite element coupled consolidation analysis of boundary value problems was demonstrated by the simulation of laboratory hydraulic fracturing experiments. The effects of rate of cavity water pressure increase, bore size, confining pressure and overconsolidation ratio on fracturing pressures were examined. The results of the parametric study of triaxial compression tests and plate loading tests were quantified in terms of stiffness (or tangent modulus), strength (or bearing pressure) and strain (or settlement) at the initial, yield, peak and ultimate states in the stress-strain (or pressure-settlement) response and allowed the comparison of these quantities for changing values of the soil model parameters. The studies revealed that the parameter x/A was the most influential because the initial states of soil were dependent on the values of ic and A and this dependence affected the subsequent stress-strain behaviour. In the prediction of movements of soil structures, the parameters x, A and a' are the most influential and their values should be critically evaluated for input in numerical analyses. In prediction of stability, the values of x, A and M are the most important ones. The work showed that the hydraulic fracturing phenomenon can be modelled by finite element coupled consolidation analysis. The computer program CRISP was validated against closed-form solutions and was found to predict the hydraulic fracturing phenomenon with a reasonable. degree of accuracy when the results were compared with the experimental data obtained by Mhach (1991). It was found that the rate of cavity water pressure increase had a significant influence in the prediction of fracturing pressure. The confining pressure was an important factor whereas the effects of bore size and overconsolidation ratio had some effects but were not as significant as the first two.
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Becerra, Victor Manuel. "Development and applications of novel optimal control algorithms." Thesis, City University London, 1994. http://openaccess.city.ac.uk/8377/.
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The main concern of this thesis is to advance and improve the existing knowledge of a dynamic optimal control technique known as DISOPE. so as to make it attractive on one hand for its implementation in the process industry and, on the other hand, as a novel nonlinear optimal control algorithm. The main feature of the technique is that it has been designed so as to achieve the correct optimum of the process in spite of inaccuracies in the mathematical model employed in the computations. Several extensions of the basic continuous time DIS OPE technique are proposed in this work. For the development of the algorithms, emphasis is placed on making the techniques implementable in digital computer based industrial process control problems. These extensions include discrete-time. and set-point tracking versions, extensions for handling control and state dependent inequality constraints. and a hierarchical version. Applications of DISOPE are proposed in the following areas: nonlinear predictive control, predictive optimising control based on adaptive state-space linear dynamic models, and batch process optimisation. All the algorithms and techniques proposed in this thesis have been implemented in software and tested with relevant simulations. These studies include dynamic simulations of low order chemical reaction systems and studies on the dynamic optimisation of an industrial-scale multicomponent distillation column using a rigorous process simulator. Comparisons with existing techniques are provided and suggestions are made for future research in the area treated in this thesis.