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Stanley, Ross James. "Quantum propagation and initial value problems in curved space." Thesis, Swansea University, 2012. https://cronfa.swan.ac.uk/Record/cronfa42356.
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Quantum field theory is studied within the semi-classical gravity approximation. The quantum correction to the propagation of both photons and gravitons in a general curved space background is calculated showing a non-trivial spacetime refractive index as well as a dynamical dressing (or undressing) of the particle state. The initial interacting particle's 'dressing', the cloud of virtual particles that surrounds it, may receive corrections from an infinite number of modes even for flat space. When gravitational tidal effects remove this dressing, squeezing it back into the bare particle, this leads to an amplification in a way consistent with unitarity. There is a possible shift discovered in the graviton wavefront velocity related to higher order curvature couplings, although in this calculation there is also a logarithmic divergence at high frequencies, leading to a breakdown of the perturbative approximation. Next we consider initial value problems and the stability of de Sitter space. Here the self decay of a massive scalar in de Sitter space is proposed to lead to a particle explosion where divergent growth of the field expectation value is observed. Directly investigating this divergent field expectation value a one loop calculation is completed for a massive scalar particle in 3-dimensional de Sitter space. This result has characteristic secular growth that can be summed into a rapidly decaying exponential by using the dynamical renormalisation group. Finally the evolution of two point functions is studied, by numerically solving their equations of motion using the Kaydanoff-Baym equations in 2-dimensional de Sitter space. Here we see a decay of the vacuum state due to the coupling. This appears to be related to the choice of initial conditions be chosen to match the free field vacuum plus non-interacting particles. This choice is made inappropriate by the dynamical dressing of the bare particle states.
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Singh, Shonal. "Spaces of initial values of differential equations with the Painlevé property." Thesis, The University of Sydney, 2018. http://hdl.handle.net/2123/18114.
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In this thesis, we study the spaces of initial values of some differential equations with the Painlevé property. The first part of our study begins by introducing the standard techniques associated with such spaces by discussing the well known example of the second Painlevé equation P_II. We then apply these techniques to the cases of linearisable second-order ordinary differential equations (ODEs) and a fourth-order analogue of P_II with particular emphasis on the solutions and structure of the singularities. We explicitly show that the initial value spaces of these ODEs can be regularised for family of general solutions while special family of solutions containing fewer free parameters than the equations’ orders require an infinite number of resolutions or blow ups. To complement our study, we also consider the spaces of initial values of partial differential equations (PDEs). Our examples are Burgers’ and the Korteweg-de Vries equations, whose movable singularities are described by Laurent expansions of the solutions around an arbitrary noncharacteristic manifold. We embed the initial values of these PDEs in complex projective spaces of the appropriate respective dimension and resolve base loci in the corresponding space. As in the ODE case, the initial value space is best understood as a foliation. It is interesting to observe that for both the PDEs, generic initial values are resolved by a finite number of blow ups, while certain initial values lead to an infinite number of blow ups. We provide evidence to show that the latter cases correspond to implicit special solutions. All of the resolutions are described explicitly. Our results suggest that the geometric framework of initial value spaces for the Painlevé equations extends to integrable PDEs. While not all the correspondences between the two frameworks are pursued in this thesis, they suggest tantalising rich directions for future research.
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Kinnersley, Mark Andrew. "The design, development and initial testing of a hypervelocity atomic oxygen source for space simulation." Thesis, University of Southampton, 1989. https://eprints.soton.ac.uk/52255/.
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Atomic Oxygen is the dominant atmospheric specie at low earth orbit altitudes for spacecraft orbiting the earth. This altitude range of atomic oxygen dominance extends from 120 km to 900 km. Other species such as helium, molecular oxygen and nitrogen make up the bulk of the rest with the densities corresponding to high to ultrahigh vacuum levels. Spacecraft orbiting at this altitude need to travel at a velocity of 8 km/sec to maintain orbit and therefore spacecraft encounter a high fluence of impinging rarefied atmosphere in a short time period. This gas-surface interaction has several effects which affect the space vehicle. They include aerodynamic drag, surface reaction and surface glow. The need to model these effects on spacecraft surfaces has resulted in the design, development and construction of an advanced facility to simulate these L.E.O. atmospheric effects. This facility utilizing an arc heated source can produce high energy species of the common atmospheric species at a velocity of up to 4.5 km/sec with fluxes comparable to orbit. This particular type of source is unique in Europe with two similar types reported in the U.S.A. Considerable effort was expended in optimizing the source for atomic oxygen production via beam characterization and stagnation condition measurement. This has enabled the radial and axial temperature profiles in the source to be deduced, thus providing a clearer idea of the processes in the source and therefore benefits future users of this technique. In addition, alternative routes of producing atomic oxygen were pursued via nitrous oxide and nitrous oxide/nitrogen seeding. Extensive work on developing reliable beam characterization equipment resulted in the comparison of two methods of beam analysis. This involved the development of a new method of beam mass/energy analysis, which has several advantages over current instruments. Conclusions are made on the suitability of mass spectroscopic detection of reactive specie beams. Finally, atomic oxygen degradation tests were pursued on a variety of surfaces including the polyimide Kapton-H. It was concluded from these tests that Kapton-H erosion has a form of energy dependence, with an energy threshold to erosion of approximately 0.5 eV. The erosion rate above this energy rises rapidly to rates comparable to those of orbit. The Southampton results agree reasonably with the very few results on Kapton-H in this energy range. This has important implications on spacecraft material design.
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Barnholdt, Jacob, and Filip Carlsson. "Convergence Properties for Different Null Space Bases When Solving the Initial Margin Optimization Problem Using CMA-ES." Thesis, KTH, Matematisk statistik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-273628.
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This thesis evaluates how the evolutionary algorithm CMA-ES (Covariance Matrix Adaption Evolution Strategy) can be used for optimizing the total initial margin for a network of banks trading bilateral OTC derivatives. The algorithm is a stochastic method for optimization of non-linear and, but not limited to, non-convex functions. The algorithm searches for an optimum by generating normally distributed samples and iteratively updating the mean and covariance matrix of the search distribution using the best candidate solutions in the sampled population. In this thesis, feasible solutions are represented by the null space obtained from the constraint of keeping all banks' market exposure unchanged throughout the optimization, and the generated samples for each iteration correspond to linear combinations of the base vectors spanning this null space. In particular, this thesis investigates how different representations of this null space affect the convergence speed of the algorithm. By applying the algorithm to problems of varying sizes, using several different null space representations coming from different matrix decomposition methods, it is found that as long as an orthonormal representation is used it does not matter which matrix decomposition method it comes from. This is found to be because, given any orthonormal null space representation, the algorithm will at start generate a rotationally invariant sample space in its search for the optimal solution, independent of the specific null space representation. If the representation is not orthogonal, the initial sample will in contrast be in the shape of an ellipsoid and thus biased in certain directions, which in general affects the performance negatively. A non-orthonormal representation can converge faster in specific optimization problems, if the direction of the solution is known in advance and the sample space is pointed towards that direction. However, the benefit of this aspect is limited in a realistic scenario and an orthonormal representation is recommended. Furthermore, as it is shown that different orthonormal representations perform equally, it is implied that other characteristics can be considered when deciding which matrix decomposition method to use; such as the importance of fast computation or desire for a sparse representation.<br>Denna avhandling utvärderar hur CMA-ES (Covariance Matrix Adaption Evolution Strategy) kan användas för att optimera en total "initial margin" för ett nätverk av banker som handlar bilaterala OTC derivat. Algoritmen är en stokastisk metod för optimering av icke-linjära och, men inte enbart, icke-konvexa funktioner. Algoritmen söker efter ett optimum genom att generera normalfördelade utfall och iterativt uppdatera medelvärdet och kovariansmatrisen för sök-fördelningen med hjälp av de bästa lösningarna i varje iteration. I detta arbete representeras tillåtna lösningar till problemet av nollrummet från bivillkoret att alla bankers marknadsexponering ska vara oförändrade genom optimeringen och de genererade utfallen består av slumpade linjärkombinationer av nollrummets basvektorer. I synnerhet undersöks hur olika representationer av nollrummet påverkar konvergenshastigheten för algoritmen. Algoritmen har applicerats med flera olika nollrumsrepresentationer, framtagna genom olika matrisfaktoriseringsmetoder, och det kan konstateras att så länge nollrummsrepresentationen är ortonormal är valet av faktoreringsmetod obetydlig. Detta då användande av orthornormala nollrumsrpresentationer i algoritmen leder till en initialt symmetrisk, rotationsmässigt invariant, sökning efter den optimala lösningen. Om representationen inte är ortogonal kommer det resulterande sökområdet i varje iteration att ha formen av en ellipsoid och sålunda viktas i vissa riktningar, vilket i allmänhet påverkar prestandan negativt. Emellertid kan en icke-ortonormal representation konvergera snabbare i specifika scenarier, givet att lösningens riktning är känd i förväg och sökområdet kan pekas mot den riktningen. Vidare, eftersom det har visats att olika ortonormala representationer konvergerar lika fort, innebär resultatet att andra egenskaper kan beaktas vid val av matrisfaktoriseringsmetod, såsom vikten av snabb beräkning eller önskan om en gles representation.
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Feng, Mi. "An Initial Exploration of a Multi-Sensory Design Space: Tactile Support for Walking in Immersive Virtual Environments." Digital WPI, 2016. https://digitalcommons.wpi.edu/etd-theses/141.
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Multi-sensory feedback can potentially improve user experience and performance in virtual environments. As it is complicated to study the effect of multi-sensory feedback as a single factor, we created a design space with these diverse cues, categorizing them into an appropriate granularity based on their origin and use cases. To examine the effects of tactile cues during non-fatiguing walking in immersive virtual environments, we selected certain tactile cues from the design space, movement wind, directional wind and footstep vibration, and another cue, footstep sounds, and investigated their influence and interaction with each other in more detail. We developed a virtual reality system with non-fatiguing walking interaction and low-latency, multi-sensory feedback, and then used it to conduct two successive experiments measuring user experience and performance through a triangle-completion task. We noticed some effects due to the addition of footstep vibration on task performance, and saw significant improvement due to the added tactile cues in reported user experience.
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Clements, Twyman Samuel. "INITIAL DESIGN, MANUFACTURE, AND TESTING OF A CUBELAB MODULE FRAME FOR BIOLOGICAL PAYLOADS ABOARD THE INTERNATIONAL SPACE STATION." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_theses/106.
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This thesis investigates the design of a CubeLab Module frame to facilitate biological research aboard the International Space Station (ISS). With the National Laboratory designation of the ISS by the United States Congress the barriers for use of the facility have been lowered for commercial and academic entities, allowing greater volume and diversity in the research that can be done. Researchers in biology and other areas could benefit from development and adoption of a plug-and-play payload containment system for use in the microgravity/space environment of the ISS. This research includes design and analysis of such a system. It also includes production and testing of a prototype. The relevant NASA requirements are documented, and they were considered during the design phase. Results from finite element analyses to predict performance of a proposed design under expected service conditions are reported. Results from functional testing of the prototype are also provided. A discussion of future work needed before the structure outlined in this thesis can become commercially viable is also presented.
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Alinder, Simon. "Space Situational Awareness with the Swedish Allsky Meteor Network." Thesis, Uppsala universitet, Observationell astrofysik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-390397.
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This thesis investigates the use of the Swedish Allsky Meteor Network (SAMN) for observing, identifying, and determining the orbits of satellites. The overall goal of this project is to determine the feasibility of using such a network for Space Situational Awareness (SSA) purposes, which requires identification and monitoring of objects in orbit. This thesis is a collaboration with the Swedish Defense Research Agency (FOI) to support their efforts in SSA. Within the frame of this project, the author developed software that can take data of observations of an object collected from the all-sky cameras of SAMN and do an Initial Orbit Determination (IOD) of the object. An algorithm that improves the results of the IOD was developed and integrated into the software. The software can also identify the object if it is in a database that the program has access to or, if it could not be identified, make an approximate prediction of when and where the object will be visible again the next time it flies over. A program that analyses the stability of the results of the IOD was also developed. This measures the spread in results of the IOD when a small amount of artificial noise is added to one or more of the observed coordinates in the sky. It was found that using multiple cameras at different locations greatly improves the stability of the solutions. Gauss' method was used for doing the IODs. The advantages and disadvantages of using this method are discussed, and ultimately other methods, such as the Gooding method or Double R iteration, are recommended for future works. This is mostly because Gauss' method has a singularity when all three lines of sight from observer to object lie in the same plane, which makes the results unreliable. The software was tested on a number of observations, both synthetic and real, and the results were compared against known data from public databases. It was found that these techniques can, with some changes, be used for doing IOD and satellite identification, but that doing very accurate position determination required for full orbit determination is not feasible.<br>Detta examensarbete undersöker möjligheterna att använda ett svenskt nätverk av allskykameror kallat SAMN (Swedish Allsky Meteor Network) för att observera, identifiera och banbestämma satelliter. Det övergripande målet med detta projekt är att bestämma hur användbart ett sådant nätverk skulle vara för att skapa en rymdlägesbild, vilken i sin tur kräver bevakning och identifikation av objekt som ligger i omloppsbana. Detta examensarbete är ett samarbete mellan Uppsala Universitet och FOI (Totalförsvarets Forskningsinstitut). Inom ramen för detta projekt har författaren utvecklat mjukvara som kan ta data från observationer av objekt utförda av SAMN och göra initiala banbestämningar av objekten. En algoritm som förbättrar resultaten av den initiala banbestämningen utvecklades och integrerades i programmen. Programmen kan också identifiera satelliter om de finns med i en databas som programmet har tillgång till eller förutsäga objektets nästa passage över observatören om det inte kunde identifieras. Ett annat program som analyserar känsligheten av resultaten av den initiala banbestämningen utvecklades också. Detta program mäter spridningen i resultat som orsakas av små störningar i de observerade koordinaterna på himlen. Det framkom att stabiliteten av resultaten kan förbättras avsevärt genom att använda flera observatörer på olika orter. I detta projekt användes Gauss metod för att göra banbestämningarna. Metodens för- och nackdelar diskuteras och i slutänden rekommenderas istället andra metoder, som Goodings metod eller Dubbel R-iteration, för framtida arbeten. Detta beror mest på att Gauss metod innehåller en singularitet när alla siktlinjer från observatören till objektet ligger i samma plan som varandra vilket gör resultaten opålitliga i de fallen. Programmen testkördes på ett antal olika observationer, både artificiella och verkliga, och resultaten jämfördes med kända positioner. Slutsatsen av arbetet är att de undersökta teknikerna kan, med vissa modifikationer, användas för att göra initiala banbestämningar och satellitidentifikationer, men att göra de väldigt precisa positionsbestämningarna som krävs för fullständig banbestämning är inte genomförbart.
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Montealegre, Scott Juan. "Initial value problem for a coupled system of Kadomtsev-Petviashvili II equations in Sobolev spaces of negative indices." Pontificia Universidad Católica del Perú, 2014. http://repositorio.pucp.edu.pe/index/handle/123456789/95255.
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John, Dominik [Verfasser]. "Uniqueness and Stability near Stationary Solutions for the Thin-Film Equation in Multiple Space Dimensions with Small Initial Lipschitz Perturbations / Dominik John." Bonn : Universitäts- und Landesbibliothek Bonn, 2013. http://d-nb.info/104527626X/34.
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Lundquist, Tomas. "High order summation-by-parts methods in time and space." Doctoral thesis, Linköpings universitet, Beräkningsmatematik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-126172.
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This thesis develops the methodology for solving initial boundary value problems with the use of summation-by-parts discretizations. The combination of high orders of accuracy and a systematic approach to construct provably stable boundary and interface procedures makes this methodology especially suitable for scientific computations with high demands on efficiency and robustness. Most classes of high order methods can be applied in a way that satisfies a summation-by-parts rule. These include, but are not limited to, finite difference, spectral and nodal discontinuous Galerkin methods. In the first part of this thesis, the summation-by-parts methodology is extended to the time domain, enabling fully discrete formulations with superior stability properties. The resulting time discretization technique is closely related to fully implicit Runge-Kutta methods, and may alternatively be formulated as either a global method or as a family of multi-stage methods. Both first and second order derivatives in time are considered. In the latter case also including mixed initial and boundary conditions (i.e. conditions involving derivatives in both space and time). The second part of the thesis deals with summation-by-parts discretizations on multi-block and hybrid meshes. A new formulation of general multi-block couplings in several dimensions is presented and analyzed. It collects all multi-block, multi-element and hybrid summation-by-parts schemes into a single compact framework. The new framework includes a generalized description of non-conforming interfaces based on so called summation-by-parts preserving interpolation operators, for which a new theoretical accuracy result is presented.
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Nwaogu, Eze. "The Effect of Aleks on Students' Mathematics Achievement in an Online Learning Environment and the Cognitive Complexity of the Initial and Final Assessments." Digital Archive @ GSU, 2012. http://digitalarchive.gsu.edu/msit_diss/94.
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For many courses, mathematics included, there is an associated interactive e-learning system that provides assessment and tutoring. Some of these systems are classified as Intelligent Tutoring Systems. MyMathLab, Mathzone, and Assessment of LEarning in Knowledge Space (ALEKS) are just a few of the interactive e-learning systems in mathematics. In ALEKS, assessment and tutoring are based on the Knowledge Space Theory. Previous studies in a traditional learning environment have shown ALEKS users to perform equally or better in mathematics achievement than the group who did not use ALEKS.
The purpose of this research was to investigate the effect of ALEKS on students’ achievement in mathematics in an online learning environment and to determine the cognitive complexity of mathematical tasks enacted by ALEKS’s initial (pretest) and final (posttest) assessments. The targeted population for this study was undergraduate students in College Mathematics I, in an online course at a private university in the southwestern United States. The study used a quasi-experimental One-Group non-randomized pretest and posttest design.
Five methods of analysis and one model were used in analyzing data: t-test, correctional analysis, simple and multiple regression analysis, Cronbach’s Alpha reliability test and Webb’s depth of knowledge model. A t-test showed a difference between the pretest and posttest reports, meaning ALEKS had a significant effect on students’ mathematics achievement. The correlation analysis showed a significant positive linear relationship between the concept mastery reports and the formative and summative assessments reports meaning there is a direct relationship between the ALEKS concept mastery and the assessments. The regression equation showed a better model for predicting mathematics achievement with ALEKS when the time spent learning in ALEKS and the concept mastery scores are used as part of the model.
According to Webb’s depth of knowledge model, the cognitive complexity of the pretest and posttest question items used by ALEKS were as follows: 50.5% required application of skills and concepts, 37.1% required recall of information, and 12.4% required strategic thinking: None of the questions items required extended thinking or complex reasoning, implying ALEKS is appropriate for skills and concepts building at this level of mathematics.
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Curiel, Luis R. III. "Investigation on the Use of Small Aperture Telescopes for LEO Satellite Orbit Determination." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2253.
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The following thesis regards the use of small aperture telescopes for space domain awareness efforts. The rapidly populating space domain was motivation for the development of a new operation scheme to conduct space domain awareness feasibility studies using small telescopes. Two 14-inch Schmidt-Cassegrain Telescopes at the California Polytechnic State University and the Air Force Research Lab in Kirtland AFB, NM, in conjunction with a dedicated CCD camera and a commercial DSLR camera, were utilized to conduct optical observations on satellites in Earth orbit.
Satellites were imaged during August 2019, and from January 2020 to March 2020, resulting in the collection of 77 valid images of 16 unique satellites. These images were used to obtain celestial spherical coordinates, which were used in Gauss and Double-R angles-only initial orbit determination methods. Initial orbit determination methods successfully produced valid results, reaffirming the feasibility of using small aperture telescopes for such methods. These orbit determinations were used to propagate orbit states forward in time to determine the feasibility of future imaging of the targets with the same apparatus. Propagation results demonstrated that initial orbit determinations rapidly decayed in accuracy over distant times and are most accurate for immediate satellite passes. In addition, an attempt to combine multiple initial orbit determinations using Lambert’s problem solutions was made. Combination of these multiple initial orbit determinations resulted in either no orbit state accuracy improvement compared to individual initial orbit determinations, or a decrease in accuracy compared to these methods. Ultimately, efforts demonstrated that small telescope usage is feasible for orbit determination operations, however there may be a need for hardware and operational revisions to improve the ability of the apparatus.
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Binjumah, Sami Mohammed. "Using activity theory to explore the perspectives of participants on an initial teacher education programme for science teachers in the Kingdom of Saudi Arabia." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/31032.
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This research discusses the issue of education reform in the Kingdom of Saudi Arabia (KSA) through an exploration of the perspectives of a range of participants involved in the preparation programme for science teachers which is run through an existing relationship between the University of Taibah and public schools in Medina city in the Kingdom of Saudi Arabia. The research examines the perspectives of participants in the university and the school (university supervisors, university coordinators, headteachers, collaborating teachers and science student teachers). It discusses teacher preparation issues in the multiple contexts reported in the literature. Teacher preparation in other contexts has revealed models which could be useful in the Saudi context. Activity Theory (AT) was used as the theoretical framework to achieve this study’s objective of exploring the academic systems of the university/school and the relationship between them in science teacher preparation, focussing on the contradictions that create conflicts for student teachers learning to teach the modern science curriculum. Activity Theory was a useful tool in organizing this research as it permitted the exploration of the relationships between systems, analysing the rich data collected on the relationship between university and school. Activity Theory acted as a link between the need for a more expansive unit of analysis in initial teacher education (ITE) studies and appropriate and effective research methods. This research is situated within the interpretative paradigm. It usescase study with mixed methods as an appropriate methodology, using multiple methods of data collection, namely semi-structured interviews as the main tool, questionnaires and documentary evidence. This research revealed the utilitarian nature of the relationship between the university and the school, which did not reach the level of a cooperative partnership, and which contained many contradictions that created conflicts for science teachers when learning the teaching skills required of modern science curricula.
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Öijerholm, Johan. "Ionic Transport in Metal Oxides Studied in situ by Impedance Spectroscopy and Cyclic Voltammetry." Doctoral thesis, KTH, Kemi, 2007. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4312.
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Ionic transport in metal oxides is crucial for the functioning of a broad range of different components, such as heat resistant alloys designed for high temperature applications and oxide electrolytes in solid oxide fuel cells. This thesis presents results from in situ electrochemical studies of properties related to ionic transport in metal oxides that are important for their applications as protective oxides and ionic conductors. Heat resistant alloys of alumina-former type are known to form an adherent, slowly growing and protective aluminium oxide (Al2O3) scale that protects metals from chemical degradation at high temperature. In situ impedance spectroscopy was used to study highly pure and dense samples of a-alumina in the temperature range 400 – 1000 °C. It was shown that surface conduction on the sample could severely distort the measurement below 700 °C. The magnitude of the distortions appeared to be sensitive to the type of electrodes used. The use of a so-called guard electrode was shown to effectively block the surface conduction in the measurements. By varying the grain size of the sintered alpha-alumina samples, the influence of grain size on the overall conductivity of the a-alumina was studied. It was shown that the activation energy for conductivity increased as the grain size decreased. Molecular dynamics calculations were performed in order to elucidate whether Al- or O ions are dominant in the ionic conductivity of the alpha-alumina. Comparing the calculation and experimental results, the dominating charge carrier was suggested to be oxygen ions. Moreover, the ionic transport in thermally grown alumina-like oxide scales formed on a FeCrAl alloy was studied in situ by impedance spectroscopy between 600 and 1000 °C. It was shown that the properties of these scales differ largely from those of pure and dense alpha-alumina. Furthermore, the conductivity is mainly electronic, due to the multiphase/multilayer microstructure and substantial incorporation of species from the base metal. However, the diffusivity obtained from the ionic conductivity was in line with diffusion data in literature obtained by other methods such as thermogravimetry. Besides, the initial stage of oxidation of a number of Fe-, Ni- and Co-based alloys at temperatures between 500 and 800 °C was studied in situ by high temperature cyclic voltammetry, in which the oxygen activity was changed over a wide range. From the resulting voltammograms the redox reactions occurring on the alloy surface could be identified. It was concluded that the base metal oxidized readily on these alloys before a protective chromia- or alumina-like scale is formed. The base metal oxide is most likely incorporated into the more protective oxide. Further, the oxygen ionic conductivity of highly pure and fully dense yttria-stabilized zirconia produced by spark plasma sintering was studied by impedance spectroscopy. The aim was to evaluate intrinsic blocking effects on the ionic conduction associated with the space charge layer in the grain boundary region. It was observed that the ionic conductivity of the spark plasma sintered oxides is equal or slightly higher than what has been achieved by conventional sintering methods. In addition, it was shown that the specific grain boundary conductivity increases with decreasing grain size, which can be explained by a decreasing Schottky barrier height (i.e., decreasing blocking effect). The quantitative results from this work verify the space charge model describing the influence of grain size on the ionic conductivity of yttria-stabilized zirconia through dopant segregation and oxygen vacancy depletion along the grain boundaries.<br>QC 20100825
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Gagliardi, James A. "An analysis of the initial planning process of new public horticulture institutions." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 157 p, 2009. http://proquest.umi.com/pqdweb?did=1694433141&sid=7&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Jakab, Tunde. "Parabolic layer potentials and initial boundary value problems in Lipschitz cylinders with data in Besov spaces." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4438.
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Thesis (Ph.D.)--University of Missouri-Columbia, 2006.<br>The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 27, 2007) Vita. Includes bibliographical references.
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Sebastianutti, Marco. "Geodesic motion and Raychaudhuri equations." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18755/.
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The work presented in this thesis is devoted to the study of geodesic motion in the context of General Relativity. The motion of a single test particle is governed by the geodesic equations of the given space-time, nevertheless one can be interested in the collective behavior of a family (congruence) of test particles, whose dynamics is controlled by the Raychaudhuri equations. In this thesis, both the aspects have been considered, with great interest in the latter issue. Geometric quantities appear in these evolution equations, therefore, it goes without saying that the features of a given space-time must necessarily arise. In this way, through the study of these quantities, one is able to analyze the given space-time. In the first part of this dissertation, we study the relation between geodesic motion and gravity. In fact, the geodesic equations are a useful tool for detecting a gravitational field. While, in the second part, after the derivation of Raychaudhuri equations, we focus on their applications to cosmology. Using these equations, as we mentioned above, one can show how geometric quantities linked to the given space-time, like expansion, shear and twist parameters govern the focusing or de-focusing of geodesic congruences. Physical requirements on matter stress-energy (i.e., positivity of energy density in any frame of reference), lead to the various energy conditions, which must hold, at least in a classical context. Therefore, under these suitable conditions, the focusing of a geodesics "bundle", in the FLRW metric, bring us to the idea of an initial (big bang) singularity in the model of a homogeneous isotropic universe. The geodesic focusing theorem derived from both, the Raychaudhuri equations and the energy conditions acts as an important tool in understanding the Hawking-Penrose singularity theorems.
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Kajerdt, Johan, and Andreas Rydberg. "Betting on the jockey rather than the horse : a study on the determinants of mergers of SPAC IPOs." Thesis, Uppsala universitet, Företagsekonomiska institutionen, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-433975.
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Special Purpose Acquisition Companies (SPACs) are public shell entities uniquely constructed to acquire one or more privately held businesses. The transaction's structural characteristics put significant pressure on the management team's capabilities to find a suitable company to acquire within the predetermined time frame. This thesis investigates whether management team characteristics, such as operating experience and gender diversity, increases the likelihood of success in identifying the target company and conducting the merger. Although not statistically significant, the results indicate that SPACs led by “C-suite” operators do not have a higher likelihood of successfully consummating a business combination. Furthermore, our data indicates gender diversity to have a positive impact on acquisition likelihood.<br>Special Purpose Acquisition Companies (SPACs) är publika skalbolag konstruerade enkom i syfte att förvärva ett eller flera privata bolag. Transaktionen lägger stor vikt på ledningens förmåga att identifiera och förvärva en eller flera verksamheter inom en förbestämd tidsram. Studien undersöker huruvida relevanta karaktärsdrag i ledningsgruppen, såsom operationell erfarenhet och skillnader i kön, ökar sannolikheten att identifiera och förvärva dessa bolag. Resultatet av studien påvisar inget samband mellan operationell erfarenhet och ökad sannolikhet för förvärv, men däremot visar sig skillnader i kön inom ledningsgruppen ha en positiv inverkan på sannolikheten för förvärv. Sammantaget är resultaten dock inte statistiskt signifikanta.
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Laino, Teodoro. "Multigrid QM/MM approaches in ab initio molecular dynamics." Doctoral thesis, Scuola Normale Superiore, 2006. http://hdl.handle.net/11384/85799.
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Pinkerton, Kim Gregory. "A comparison of alternative methods of obtaining Defense Logistics Agency (DLA) cognizance spare parts for Contractor Furnished Equipment (CFE) during initial outfitting of U.S. Navy ships." Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26416.
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Approved for public release; distribution is unlimited<br>This thesis is a limited determination of the most cost effective method of acquiring Defense Logistics Agency (DLA) cognizance initial outfitting material for new construction ships. The study is restricted to Contractor Furnished Material (CFM) required to support Contractor Furnished Equipment (CFE) contained in the Hull, Mechanical, Electrical, Ordnance and Electronics (HMEO&E) Coordinated Shipboard Allowance List (COSAL). Three alternative methods of procuring the material are analyzed for cost effectiveness: (1) the shipbuilder procures the material commercially, (2) the shipbuilder is allowed access to the Federal Supply System (FSS) and requisitions the material, (3) the Naval Supervising Agency (NSA) requisitions the material from the FSS in which case it becomes Government Furnished Material (GFM). Material availability using each of the alternatives is also examined.
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Kapfunde, Goodwell. "Near-capacity sphere decoder based detection schemes for MIMO wireless communication systems." Thesis, University of Hertfordshire, 2013. http://hdl.handle.net/2299/11350.
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The search for the closest lattice point arises in many communication problems, and is known to be NP-hard. The Maximum Likelihood (ML) Detector is the optimal detector which yields an optimal solution to this problem, but at the expense of high computational complexity. Existing near-optimal methods used to solve the problem are based on the Sphere Decoder (SD), which searches for lattice points confined in a hyper-sphere around the received point. The SD has emerged as a powerful means of finding the solution to the ML detection problem for MIMO systems. However the bottleneck lies in the determination of the initial radius. This thesis is concerned with the detection of transmitted wireless signals in Multiple-Input Multiple-Output (MIMO) digital communication systems as efficiently and effectively as possible. The main objective of this thesis is to design efficient ML detection algorithms for MIMO systems based on the depth-first search (DFS) algorithms whilst taking into account complexity and bit error rate performance requirements for advanced digital communication systems. The increased capacity and improved link reliability of MIMO systems without sacrificing bandwidth efficiency and transmit power will serve as the key motivation behind the study of MIMO detection schemes. The fundamental principles behind MIMO systems are explored in Chapter 2. A generic framework for linear and non-linear tree search based detection schemes is then presented Chapter 3. This paves way for different methods of improving the achievable performance-complexity trade-off for all SD-based detection algorithms. The suboptimal detection schemes, in particular the Minimum Mean Squared Error-Successive Interference Cancellation (MMSE-SIC), will also serve as pre-processing as well as comparison techniques whilst channel capacity approaching Low Density Parity Check (LDPC) codes will be employed to evaluate the performance of the proposed SD. Numerical and simulation results show that non-linear detection schemes yield better performance compared to linear detection schemes, however, at the expense of a slight increase in complexity. The first contribution in this thesis is the design of a near ML-achieving SD algorithm for MIMO digital communication systems that reduces the number of search operations within the sphere-constrained search space at reduced detection complexity in Chapter 4. In this design, the distance between the ML estimate and the received signal is used to control the lower and upper bound radii of the proposed SD to prevent NP-complete problems. The detection method is based on the DFS algorithm and the Successive Interference Cancellation (SIC). The SIC ensures that the effects of dominant signals are effectively removed. Simulation results presented in this thesis show that by employing pre-processing detection schemes, the complexity of the proposed SD can be significantly reduced, though at marginal performance penalty. The second contribution is the determination of the initial sphere radius in Chapter 5. The new initial radius proposed in this thesis is based on the variable parameter α which is commonly based on experience and is chosen to ensure that at least a lattice point exists inside the sphere with high probability. Using the variable parameter α, a new noise covariance matrix which incorporates the number of transmit antennas, the energy of the transmitted symbols and the channel matrix is defined. The new covariance matrix is then incorporated into the EMMSE model to generate an improved EMMSE estimate. The EMMSE radius is finally found by computing the distance between the sphere centre and the improved EMMSE estimate. This distance can be fine-tuned by varying the variable parameter α. The beauty of the proposed method is that it reduces the complexity of the preprocessing step of the EMMSE to that of the Zero-Forcing (ZF) detector without significant performance degradation of the SD, particularly at low Signal-to-Noise Ratios (SNR). More specifically, it will be shown through simulation results that using the EMMSE preprocessing step will substantially improve performance whenever the complexity of the tree search is fixed or upper bounded. The final contribution is the design of the LRAD-MMSE-SIC based SD detection scheme which introduces a trade-off between performance and increased computational complexity in Chapter 6. The Lenstra-Lenstra-Lovasz (LLL) algorithm will be utilised to orthogonalise the channel matrix H to a new near orthogonal channel matrix H ̅.The increased computational complexity introduced by the LLL algorithm will be significantly decreased by employing sorted QR decomposition of the transformed channel H ̅ into a unitary matrix and an upper triangular matrix which retains the property of the channel matrix. The SIC algorithm will ensure that the interference due to dominant signals will be minimised while the LDPC will effectively stop the propagation of errors within the entire system. Through simulations, it will be demonstrated that the proposed detector still approaches the ML performance while requiring much lower complexity compared to the conventional SD.
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Khlaief, Amor. "Contribution à la commande vectorielle sans capteur mécanique des machines synchrones à aimants permanents (MSAP)." Phd thesis, Aix-Marseille Université, 2012. http://tel.archives-ouvertes.fr/tel-00814276.
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Ce travail de recherche s'intéresse à la commande sans capteur mécanique du moteur synchrone à aimants permanents (MSAP) à pôles saillants, particulièrement en basse vitesse, avec détection de la position initiale du rotor. Après une présentation des techniques et approches qui ont initié nos travaux, en terme d'estimation de la vitesse et/ou de la position, nous avons choisi celles qui présentent plus d'intérêt de point de vue stabilité, robustesse, précision et simplicité d'implémentation. La première approche est basée sur le Système Adaptatif avec Modèle de Référence (MRAS). Quant à la deuxième, elle est réalisée autour d'un observateur non-linéaire pour l'estimation de la position et de la vitesse du MSAP à pôles saillants. Les deux techniques d'observation de la vitesse sont associées à une commande par orientation du flux rotorique avec la technique MLI vectorielle. Pour détecter la position initiale du rotor, nous avons utilisé une nouvelle approche qui permet d'estimer cette position avec une incertitude de 5° mécanique. Cette nouvelle approche est basée sur l'application de signaux tests aux bornes des phases statoriques du MSAP. Des résultats de simulation et expérimentaux sont présentés tout au long de ces travaux pour valider les études théoriques de la commande vectorielle sans capteur mécanique du MSAP. Enfin, nous avons étudié et analysé les performances de la commande tolérante aux défauts sans capteur mécanique du MSAP en présence de défaillances de types transistors à l'état-off. Les résultats expérimentaux obtenus avec les deux approches d'estimation de la vitesse en utilisant l'observateur MRAS et un observateur non linéaire ont permis d'améliorer la fiabilité du système de manière à rendre possible la commande vectorielle sans capteur mécanique en mode dégradé (alimentation avec deux bras de l'onduleur). En effet, les résultats de la commande sans capteur mécanique de la MSAP en mode dégradé montrent que l'observateur non linéaire est le mieux adapté pour ce type de fonctionnement car il présente de faible ondulation du couple et de vitesse. A l'aide d'un banc d'essais que nous avons développé au laboratoire LSIS-pôle Ecole Centrale de Marseille (ECM), nous avons pu valider expérimentalement les différentes approches proposées dans ce travail de recherche. Les résultats obtenus montrent l'efficacité des techniques mises en œuvre pour la commande vectorielle sans capteur mécanique du MSAP à pôle saillant en termes de robustesse, stabilité, précision et rapidité.
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Venturieri, Bianca. "A formação de professores dos anos iniciais do ensino fundamental em espaços não formais na Amazônia : investigando uma iniciativa no Centro de Ciências e Planetário do Pará /." Bauru, 2019. http://hdl.handle.net/11449/191046.
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Orientador: Renato Eugenio da Silva Diniz<br>Resumo: A educação em ciências é uma prática social que vem sendo cada vez mais ampliada e desenvolvida nos chamados espaços não formais de educação. Por apresentar estratégias de ensino atrativas e interativas, a utilização desses espaços pode contribuir para uma alfabetização científica mais efetiva tanto para os alunos como também para os professores. Partindo dessa perspectiva o objetivo geral desta pesquisa foi analisar as possibilidades e limites de uma proposta de formação continuada de professores dos anos iniciais do Ensino Fundamental, que busca uma ressignificação da relação entre o ensino de Ciências em espaços não formais e a prática docente escolar. Para atender tal objetivo a pesquisa foi desenvolvida, no período de janeiro de 2016 a março de 2018, no Centro de Ciências e Planetário do Pará – CCPP, localizado na cidade de Belém no estado do Pará. Os sujeitos foram professores de Ciências que atuavam em turmas dos anos iniciais do Ensino Fundamental e os dados qualitativos foram coletados por meio da observação participante, de questionários e entrevistas. A análise dos dados coletados utilizou-se o conjunto de técnicas da Análise de Conteúdo. Através dos resultados obtidos a partir do levantamento do perfil dos professores foram realizadas ações de formação onde a proposta levou em consideração a análise crítica da realidade docente. A formação foi desenvolvida no período de julho a novembro de 2017 e o último encontro ocorreu em maio de 2018. O processo formativo ocor... (Resumo completo, clicar acesso eletrônico abaixo)<br>Abstract: Education in science is a social practice that has been increasingly expanded and developed in the so-called non-formal spaces of education. By presenting attractive and interactive teaching strategies, the use of these spaces can contribute to a more effective scientific literacy for both students and teachers. From this perspective, the general objective of this research was to analyze the possibilities and limits of a proposal for the continuous training of teachers from the initial years of Elementary Education, which seeks a re - signification of the relationship between science teaching in non - formal spaces and school teaching practice. In order to meet this objective, the research was carried out from January 2016 to March 2018 at the Center of Sciences and Planetarium of Pará - CCPP, located in the city of Belém in the state of Pará. Subjects were science teachers who worked in classes from the initial years of elementary school and qualitative data were collected through participant observation, questionnaires and interviews. The analysis of the collected data was used the set of techniques of Content Analysis. Through the results obtained from the survey of the profile of the teachers were carried out training actions where the proposal took into account the critical analysis of the teaching reality. A was developed in the period from July to November 2017 and the last meeting took place in May 2018. The training process took place in 5 stages: 4 face-to-face stag... (Complete abstract click electronic access below)<br>Doutor
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CRUZ, Thamires Santos. "Uma teoria de regularidade para equações de volterra fracionárias com dados iniciais locais e não locais." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/18454.
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Previous issue date: 2016-02-26<br>CNPQ<br>Este trabalho trata da teoria de existência, unicidade, regularidade, continuação e alternativa de Blow-up de solução brandas para Equação de Volterra Fracionarias com condições iniciais locais cujo termo não linear satisfaz certas propriedades localmente Lipschitz. Analisamos também o caso de condições iniciais não locais e não linearidades verificando condições do tipo Caratheodory. Neste caso estudamos as propriedades topológicas do conjunto soluções de tais equações.<br>his work deals with existence, uniqueness, regularity, continuation and Blow up
Alternative of mild solutions for Fractional Volterra Equations with local initial conditions,
whose nonlinear terms satisfy some locally Lipschitz properties. Moreover we analyse thecase of nonlocal initial conditions and nonlinearities of Caratheodory type. In this case, we study topological properties of the solution set of such equations.
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Farhat, Ayman. "Calculs théoriques avec le couplage spin orbitales pour les molécules diatomiques YS, YN, ZrS, et ZrN." Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10078/document.
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Cette thèse est consacrée à l'étude ab initio des structures électroniques des molécules diatomiques polaires YN, YS, ZrN, et ZrS. Cette étude est motivé par le manque d’informations dans la littérature sur la structure électronique de ces molécules, alors qu’elles ont clairement été identifiées dans le spectre de certaines étoiles. Des calculs théoriques sont ainsi nécessaire puisqu’ils peuvent fournir d'importantes informations quant aux propriétés des états électroniques fondamentaux et excités qui ne sont pas accessibles expérimentalement. Dans ce travail les calculs ab initio ont été effectués par la méthode du champ auto-cohérent de l'espace actif complet (CASSCF), suivie par l'interaction de configuration multiréférence (MRSDCI). La correction de Davidson, notée (MRSDCI+ Q), a ensuite été appliquée pour rendre compte de clusters ou agrégats quadruples non liés. Les calculs ont été effectués selon deux schémas. Dans le premier les effets spin-orbite ont été négligés alors que dans le second les effets spin orbite ont été inclus par la méthode des potentiels de noyau efficaces. Tous les calculs ont été effectués en utilisant le programme de calcul de chimie physique MOLPRO et en tirant parti de l’interface graphique Gabedit. Les courbes d'énergie potentielle ont été construites et des constantes spectroscopiques calculées, ainsi que les moments dipolaires électriques permanent, les champs électriques moléculaires intenses et les structures énergétiques de vibration-rotation. Nous avons détecté dans la molécule ZrS plusieurs niveaux vibrationnels dégénérés ceux-ci peuvent être utilisés pour rechercher les variantes possibles de la constante de structure fine α etdu rapport de masse μ de l’electron par rapport au proton dans trois étoiles de type S, du nomde Rand, les RCas, et χCyg. La comparaison des données expérimentales et théoriques pour la plupart des constantes calculées a montré une bonne précision pour nos prédictions avec une différence relative (en pourcentage) qui varie entre 0,1% et 10%. Ces résultats devraient ainsi mener à des études expérimentales plus poussées pour ces molécules<br>This dissertation is dedicated to the ab initio study of the electronic structures of the polardiatomic molecules YN, YS, ZrN, and ZrS. The identification of these molecules in the spectraof stars as well as the lack in literature on the electronic structures of these molecules motivatedthe present study. Theoretical calculations are useful in this respect since they can provideimportant data for the properties of the ground and excited electronic states that are not availablefrom experimental means. In the present work the ab initio calculations were performed at thecomplete active space self-consistent field method (CASSCF) followed by multireference singleand double configuration interaction method (MRSDCI). The Davidson correction noted as(MRSDCI+Q) was then invoked in order to account for unlinked quadruple clusters. Thecalculations were performed on two stages in the first spin orbit effects were neglected while inthe second type of calculations spin orbit effects were included by the method of effective corepotentials. All of the calculations were done by using the computational physical chemistryprogram MOLPRO and by taking advantage of the graphical user interface Gabedit. In thepresent work potential energy curves were constructed and spectroscopic constants computed,along with permanent electric dipole moments, internal molecular electric fields, and vibrationalrotationalenergy structures. We detected in the ZrS molecule several degenerate vibrationalenergy levels which can be used to search for possible variations of the fine structure constant αand the electron to proton mass ratio μ in three S-type stars, named Rand, RCas, and χCyg. Acomparison with experimental and theoretical data for most of the calculated constantsdemonstrated a good accuracy for our predictions giving a percentage relative difference thatranged between 0.1% and 10%. Finally, we expect that the results of the present work shouldinvoke further experimental investigations for these molecules
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Cardoso, Luciana Cristina. "Aprendizagem e desenvolvimento profissional da docência em um espaço híbrido de formação : o terceiro espaço." Universidade Federal de São Carlos, 2016. https://repositorio.ufscar.br/handle/ufscar/7787.
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Previous issue date: 2016-02-26<br>Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)<br>This research aimed to analyze the limits and contributions of a hybrid space, the 3rd Space, understood as dialogue environment between students of Pedagogy - of distance learning programs -, experienced Elementary School teachers, mentors of the initial years of Middle School Education and University researchers / academic advisors, aiming at learning the teaching profession and the professional development of teachers. Specifically, the intent was to analyze construction processes of knowledge needed for the exercise of pedagogical practices in varied school contexts; to understand how knowledge and skills are integrated, providing the knowledge base for teaching; and to understand if a hybrid space supports the articulation of knowledge of various natures in favor of learning the teaching profession. The
theoretical framework comprised: initial and continuing teacher training; learning the teaching profession and professional development; knowledge base; university-school partnership; hybrid spaces of training and written narratives, their main authors being Veenman, Shulman, Cavaco, Garcia, Mizukami, Zeichner, Vaughan, Penã and Allegretti. A constructive-collaborative approach was used (COLE; KNOWLES, 2003) for research and intervention. The data collection instruments were written narratives (VAZ; MENDES; MAUÉS, 2001) prepared by the participants, and the analysis took place in a procedural manner, based on the knowledge model for teaching as a main reference (SHULMAN, 1987, 2005), and the profession and professional teaching as categories that are both complementary and revealing of the specifics of the teacher's work (NÓVOA, 1999; CONTRERAS, 2002; ROLDÃO, 2007). The in-depth analyses were made from the study of multiple cases (EZPELETA, 1984; LUDKE; ANDRÉ 1986; MAZZOTTI, 2006), arising from professional apprenticeships of teaching three dyads (mentor / undergraduate student), one of which is active in the Early Years of Middle School, and the other two in Elementary School. Analyses indicated that learning to teach and being a teacher are processes that are enhanced throughout life, highly influenced by previous experiences - be they formal or informal - related to the teaching profession and the specific contexts of action. It was suggested that the formative demand for the teaching practice for Elementary School and Early Years of Middle School focused on the process involving the mastery of general pedagogical knowledge. Additionally, little ability to plan educational interventions consistent with the needs of children was identified, even when dealing with experienced teachers. As a training space, the virtual learning environment (VLE) created with the development of research and called 3rd Space revealed itself as a viable tool for the articulation between the knowledge derived from their participants (mentors, undergraduate students and researchers / academic advisors) and for strengthening the links between the university and teachers' work reality. While articulating relations between theory and practice, the hybrid space potentiated the reflective exercise, especially in the case of undergraduate students; however, it faced some difficulties due to the exclusive use of written narratives, predominantly in the case of experienced teachers (mentors).<br>A pesquisa teve como propósito analisar limites e contribuições de um espaço híbrido, o 3o
Espaço, compreendido como ambiente de interlocução entre licenciandas em Pedagogia, na
modalidade a distância, professoras experientes da Educação Infantil e dos Anos Iniciais do
Ensino Fundamental (mentoras) e pesquisadoras-formadoras da universidade, visando à
aprendizagem da docência e ao desenvolvimento profissional de professores. Especificamente, pretendeu-se analisar processos de construção de conhecimentos necessários para o exercício de práticas pedagógicas em contextos escolares variados; compreender como
conhecimentos teóricos e práticos se integram, constituindo a base de conhecimento para o
ensino; e entender se um espaço híbrido sustenta a articulação de conhecimentos de naturezas
diversas em benefício da aprendizagem da docência. O referencial teórico englobou: formação inicial e continuada de professores; aprendizagem da docência e desenvolvimento profissional; base de conhecimento; parceria universidade-escola; espaços híbridos de formação e narrativas escritas, tendo como principais autores: Veenman, Shulman, Cavaco,
Garcia, Mizukami, Zeichner, Vaughan, Penã e Allegretti. Adotou-se uma abordagem
construtivo-colaborativa (COLE; KNOWLES, 2003) de pesquisa e intervenção. Os instrumentos de coleta de dados foram narrativas escritas (VAZ; MENDES; MAUÉS, 2001) elaboradas pelas participantes, e a análise se deu de modo processual, tendo o modelo de base de conhecimento para o ensino como referência principal (SHULMAN, 1987, 2005) e a
profissão e a profissionalidade docente como categorias complementares e reveladoras das
especificidades do trabalho do professor (NÓVOA, 1999; CONTRERAS, 2002; ROLDÃO, 2007). As análises em profundidade foram feitas a partir do estudo de casos múltiplos (EZPELETA, 1984; LUDKE; ANDRÉ 1986; MAZZOTTI, 2006), decorrentes das
aprendizagens profissionais da docência de três díades (mentora/licencianda), uma delas
atuante nos Anos Iniciais do Ensino Fundamental, e as outras duas na Educação Infantil. As análises indicaram que aprender a ensinar e ser professor são processos que se aprimoram ao longo da vida, altamente influenciados por experiências anteriores, formais ou informais, relativas ao exercício da docência e pelos contextos específicos de atuação. Sugeriram que a demanda formativa para a atuação docente na Educação Infantil e nos Anos Iniciais do Ensino Fundamental se centrou no processo que envolve o domínio do conhecimento pedagógico
geral. Adicionalmente, identificou-se pouca habilidade para planejar intervenções pedagógicas coerentes com as necessidades das crianças, mesmo se tratando de professoras experientes. Enquanto espaço formativo, o ambiente virtual de aprendizagem (AVA), criado em função do desenvolvimento da pesquisa e denominado 3o Espaço, revelou-se como
ferramenta viável para a articulação entre os conhecimentos advindos de suas participantes
(mentoras, licenciandas e pesquisadoras-formadoras) e para aproximações entre a universidade e a realidade de trabalho das professoras. Enquanto articulador de relações entre teoria e prática, o espaço híbrido potencializou o exercício reflexivo, principalmente no caso das licenciandas, mas enfrentou algumas dificuldades em razão do uso exclusivo de narrativas escritas, sobretudo no caso das professoras experientes (mentoras).<br>FAPESP no 2014/11263-5
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Chen, Shyuan-Jye, and 陳玄杰. "Hypersonic Flight Envelope of Winged Space Vehicles with Large Initial Heading." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/78659970223494823212.
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Chen, Yen-Hsun, and 陳彥勳. "Hypersonic Flight Envelope of Winged Space Vehicles with Small Initial Heading." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/23397431847430058197.
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碩士<br>國立中央大學<br>機械工程研究所<br>82<br>In this paper, the flight maneuvers of aero-interception and
aero-rendezvous in constant altitude with small initial heading
is main concern. We use the optimal trajectories of coasting
flight with hypersonic to construct the flight envelope of
lifting space vehicles. The different between aero-interception
and aero-rendezvous is final condition. Aero-interception only
satisfied the final point is prescribed final destination.
However, Aero-rendezvous must satisfy another condition :
velocity constraint. We used the coordinate rotaion technique
to help us saving numerical computed time. The final, we add G-
value and heating rate contraints in our coasting flight to
tally true flight conditon, and discuss these constraints have
some influence with flight envelope.
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Bai, Xiaoli. "Modified Chebyshev-Picard Iteration Methods for Solution of Initial Value and Boundary Value Problems." Thesis, 2010. http://hdl.handle.net/1969.1/ETD-TAMU-2010-08-8240.
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The solution of initial value problems (IVPs) provides the evolution of dynamic
system state history for given initial conditions. Solving boundary value problems
(BVPs) requires finding the system behavior where elements of the states are defined
at different times. This dissertation presents a unified framework that applies modified
Chebyshev-Picard iteration (MCPI) methods for solving both IVPs and BVPs.
Existing methods for solving IVPs and BVPs have not been very successful in
exploiting parallel computation architectures. One important reason is that most
of the integration methods implemented on parallel machines are only modified versions
of forward integration approaches, which are typically poorly suited for parallel
computation.
The proposed MCPI methods are inherently parallel algorithms. Using Chebyshev
polynomials, it is straightforward to distribute the computation of force functions
and polynomial coefficients to different processors. Combining Chebyshev polynomials
with Picard iteration, MCPI methods iteratively refine estimates of the solutions
until the iteration converges. The developed vector-matrix form makes MCPI methods
computationally efficient.
The power of MCPI methods for solving IVPs is illustrated through a small perturbation
from the sinusoid motion problem and satellite motion propagation problems.
Compared with a Runge-Kutta 4-5 forward integration method implemented in MATLAB, MCPI methods generate solutions with better accuracy as well as orders
of magnitude speedups, prior to parallel implementation. Modifying the algorithm
to do double integration for second order systems, and using orthogonal polynomials
to approximate position states lead to additional speedups. Finally, introducing
perturbation motions relative to a reference motion results in further speedups.
The advantages of using MCPI methods to solve BVPs are demonstrated by
addressing the classical Lambert’s problem and an optimal trajectory design problem.
MCPI methods generate solutions that satisfy both dynamic equation constraints and
boundary conditions with high accuracy. Although the convergence of MCPI methods
in solving BVPs is not guaranteed, using the proposed nonlinear transformations,
linearization approach, or correction control methods enlarge the convergence domain.
Parallel realization of MCPI methods is implemented using a graphics card that
provides a parallel computation architecture. The benefit from the parallel implementation
is demonstrated using several example problems. Larger speedups are achieved
when either force functions become more complicated or higher order polynomials are
used to approximate the solutions.
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Bradley, Nicholas Ethan. "Initial guess and optimization strategies for multi-body space trajectories with application to free return trajectories to near-Earth asteroids." Thesis, 2014. http://hdl.handle.net/2152/26858.
Full textAbstract:
This concept of calculating, optimizing, and utilizing a trajectory known as a ``Free Return Trajectory" to facilitate spacecraft rendezvous with Near-Earth Asteroids is presented in this dissertation. A Free Return Trajectory may be defined as a trajectory that begins and ends near the same point, relative to some central body, without performing any deterministic velocity maneuvers (i.e., no maneuvers are planned in a theoretical sense for the nominal mission to proceed). Free Return Trajectories have been utilized previously for other purposes in astrodynamics, but they have not been previously applied to the problem of Near-Earth Asteroid rendezvous. Presented here is a series of descriptions, algorithms, and results related to trajectory initial guess calculation and optimal trajectory convergence. First, Earth-centered Free Return Trajectories are described in a general manner, and these trajectories are classified into several families based on common characteristics. Next, these trajectories are used to automatically generate initial conditions in the three-body problem for the purpose of Near-Earth Asteroid rendezvous. For several bodies of interest, example initial conditions are automatically generated, and are subsequently converged, resulting in feasible, locally-optimal, round-trip trajectories to Near-Earth Asteroids utilizing Free Return Trajectories. Subsequently, a study is performed on using an unpowered flyby of the Moon to lower the overall DV cost for a nominal round-trip voyage to a Near-Earth Asteroid. Using the Moon is shown to appreciably decrease the overall mission cost. In creating the formulation and algorithms for the Lunar flyby problem, an initial guess routine for generic planetary and lunar flyby tours was developed. This continuation algorithm is presented next, and details a novel process by which ballistic trajectories in a simplistic two-body force model may be iteratively converged in progressively more realistic dynamical models until a final converged ballistic trajectory is found in a full-ephemeris, full-dynamics model. This procedure is useful for constructing interplanetary transfers and moon tours in a realistic dynamical framework; an interplanetary and an inter-moon example are both shown. To summarize, the material in this dissertation consists of: novel algorithms to compute Free Return Trajectories, and application of the concept to Near-Earth Asteroid rendezvous; demonstration of cost-savings by using a Lunar flyby; and a novel routine to transfer trajectories from a simplistic model to a more realistic dynamical representation.<br>text
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Lee, Hanku. "The existence and uniqueness of solutions in a weighted Sobolov space for an initial-boundary problem of a degenerate parabolic equation with principal part in divergence form." Thesis, 2000. http://hdl.handle.net/1957/16962.
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Allen, Melissa Ree. "The Effects of Varying Physical Parameterizations and Initial Conditions on Tracer Transport in the National Aeronautics and Space Administration’s Goddard Earth Observation System Model, Version 5." 2011. http://trace.tennessee.edu/utk_gradthes/946.
Full textAbstract:
The evolution of General Circulation Models (GCM) for climate study has led to more accurate predictions for atmospheric transport, yet precision in predictions remains in need of improvement. The National Aeronautics and Space Administration Goddard Earth Observation System model, Version 5 (GEOS-5) represents a state of the art climate model capable of simulating a wide variety of atmospheric processes informed continuously by satellite observations. This thesis examines some of the physical parameterizations employed by GEOS-5 and their effect on the transport of two greenhouse gasses: ozone and carbon dioxide.
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Cleary, Erin. "The Scientific Way to Simulate Pattern Formation in Reaction-Diffusion Equations." Thesis, 2013. http://hdl.handle.net/10214/6659.
Full textAbstract:
For a uniquely defined subset of phase space, solutions of non-linear, coupled reaction-diffusion equations may converge to heterogeneous steady states, organic in appearance. Hence, many theoretical models for pattern formation, as in the theory of morphogenesis, include the mechanics of reaction-diffusion equations. The standard method of simulation for such pattern formation models does not facilitate reproducibility of results, or the verification of convergence to a solution of the problem via the method of mesh refinement. In this thesis we explore a new methodology circumventing the aforementioned issues, which is independent of the choice of programming language. While the new method allows more control over solutions, the user is required to make more choices, which may or may not have a determining effect on the nature of resulting patterns. In an attempt to quantify the extent of the possible effects, we study heterogeneous steady states for two well known reaction-diffusion models, the Gierer-Meinhardt model and the Schnakenberg model.<br>Alexander Graham Bell Canada Graduate Scholarship provides financial support to high calibre scholars who are engaged in master's or doctoral programs in the natural sciences or engineering.<br>Natural Sciences and Engineering Research Council of Canada
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Chung-Wei, Du, and 杜中偉. "A Research of Weapon System Initial Spare Parts Evaluation in Criticality and cost- efficiency." Thesis, 2002. http://ndltd.ncl.edu.tw/handle/20230966914536501087.
Full textAbstract:
碩士<br>國防大學中正理工學院<br>兵器系統工程研究所<br>90<br>Based on the actual operational experience, the demands for spare/repair parts are usually erratic. The provisioning of spare/repair parts frequently experiences variation over time. The provisioning of too little critical items results in causing the system to be inoperative due to stock-out. However, the excess of items in the inventory can also be costly. The purpose of this research is to develop an effective and efficient method and strategy for the initial provisioning and acquisition of the appropriate critical spare/repair parts which have a significant impact on the system operational availability and total life-cycle cost.
The criticality of spare/repair parts is utilized to estimate the proper quantity of items for the initial provisioning so that the best plan will arrive at an optimum balance between a stock-out situation and the level of inventory to reflect a least-cost inventory profile. In this research, a developing weapon system is selected as a case to demonstrate the applicability of the developed method. The effects of turn-around-time are discussed and used in the calculation and evaluation of spare/repair parts criticality. Traditionally, turn-around-time is identified as repair time of the upper replacement level. In this research, the repair rates of critical items are analyzed and applied to accurately calculate turn-around-time.
In addition to failure rates, the determination of spare/repair parts requirements will be affected by many other factors such as criticality, turn-around-time, unit cost, etc. To evaluate criticality, the Failure Modes, Effects and Criticality Analysis (FMECA) is developed to calculate the risk priority number (RPN), grey relation analysis (GRA), and turn-around-time. Criticality is applicable to the determination of weightiness for each end-item in order to accurately derive the initial spare/repair parts lists.
Finally, the results indicate that both the criticality of items and the turn-around-times of maintenance levels have significant influence on the cost-effectiveness curves. An efficient procedure for the initial spare/repair parts provisioning is also presented which can be used to reengineer the maintenance flow.
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Cheng, Mei-Feng, and 鄭梅峰. "A Study of Initial Spare Parts Inventory Strategies Based on Availability－ A Simulation Analysis of X Weapon System." Thesis, 2003. http://ndltd.ncl.edu.tw/handle/70655661355312390328.
Full textAbstract:
碩士<br>國防管理學院<br>資源管理研究所<br>91<br>Spare parts management is one of most important duties for military logistic departments who charge the availability of weapon systems. Because of the insufficiency of spare parts could result in failed equipment and fighting, but excessive stock of spare parts may lead to the high holding cost. So the difficulty of the job is that the manager must provide sufficient spare parts to ensure the availability of weapon systems under restricted budget.
This paper is based on operational availability and has been considered Major levels of Maintenance, Reliability, Failure rate and Multi-indenture. We construct a simplified model by simulation approach with SIMSCRIPT II.5 and figure out the mean logistics delay time (MLDT), mean time to repair (MTTR) and mean time between failure (MTBF) by sensitivity analysis of inventory strategies, lead time and maintenance resources variation under the case of X weapon system.
Finally, we get some conclusions as following：（1）(S-1, S) inventory strategy is more suitable than (s, S) strategy for advancing the availability of weapon system.（2）It is little effect if you want to enhance availability only by increasing the stock of spare parts and not adjusting the inventory strategy, lead time or maintenance mechanism.
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Dolanský, Jindřich. "Stroj času jako kulečník." Doctoral thesis, 2011. http://www.nusl.cz/ntk/nusl-299133.
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Title: Billiard time machine Author: Jindřich Dolanský Department: Institute of Theoretical Physics Supervisor: doc. RNDr. Jiří Langer, CSc. Supervisor's e-mail address: Jiri.Langer@mff.cuni.cz Abstract: In this work we investigate a simple interacting system of an elastic particle in the non-relativistic spacetime with a nontrivial causal structure realized by a worm- hole with a time shift. We require that standard local physical laws hold, and search for their globally consistent solutions, i.e, we assume the validity of the principle of self-consistency. If there were nontrivial set of initial conditions which would violate this principle, the system would be logically inconsistent. We show that the investigated system is not inconsistent in this sense, i.e., that all standard initial conditions have a globally consistent evolution. Even for the so called dangerous initial conditions which threaten to result into the paradoxical situation a consistent solution exists. In this case, the paradoxical collision-free trajectory is superseded by a special consistent self-colliding trajectory. Moreover, we demonstrate that more than one globally consistent evolution exists for a wide class of initial conditions. Thus, the evolution of the described system is not unique due to the nontrivial causal structure...
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Rodenkirchen, Jürgen. "On optimum convergence rates of the Crank-Nicholson scheme to the stokes initial value problem in higher order function spaces using realistic data /." 1995. http://bvbr.bib-bvb.de:8991/F?func=service&doc_library=BVB01&doc_number=007126411&line_number=0001&func_code=DB_RECORDS&service_type=MEDIA.
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Lind, Crystal. "The gravitational Vlasov-Poisson system on the unit 2-sphere with initial data along a great circle." Thesis, 2014. http://hdl.handle.net/1828/5613.
Full textAbstract:
The Vlasov-Poisson system is most commonly used to model the movement of charged
particles in a plasma or of stars in a galaxy. It consists of a kinetic equation known
as the Vlasov equation coupled with a force determined by the Poisson equation.
The system in Euclidean space is well-known and has been extensively studied under
various assumptions. In this paper, we derive the Vlasov-Poisson equations assuming
the particles exist only on the 2-sphere, then take an in-depth look at particles which
initially lie along a great circle of the sphere. We show that any great circle is an
invariant set of the equations of motion and prove that the total energy, number of
particles, and entropy of the system are conserved for circular initial distributions.<br>Graduate
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Takeya, Satoshi, Konstantin A. Udachin, and John A. Ripmeester. "AB INITIO STRUCTURE DETERMINATION OF GAS HYDRATES AND REFINEMENT OF GUEST MOLECULE POSITIONS BY POWDER X-RAY DIFFRACTION." 2008. http://hdl.handle.net/2429/1092.
Full textAbstract:
Structure determination of powdered crystals is still not a trivial task. For gas hydrates, the difficulty lies in how to determine the rotational disorder and cage occupancies of the guest molecules without other supporting information or constraints because the complexity of the problem for the powder diffraction technique generally depends on the number of atoms to be located in the asymmetric unit. Here, the crystal structures of gas hydrates of CO2, C2H6, C3H8, and Methylcyclohexane/CH4, as determined by the direct-space and Rietveld techniques are reported. The resultant structures and cage occupancies were consistent with results found from conventional experimental methods using single crystal x-ray diffraction or solid-state 13C-NMR. It was shown that the procedures reported in this study make it possible to determine guest disorder and absolute cage occupancy of gas hydrates even from powder crystal.
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Kim, Minjung active 21st century. "Ab initio simulation methods for the electronic and structural properties of materials applied to molecules, clusters, nanocrystals, and liquids." Thesis, 2014. http://hdl.handle.net/2152/25099.
Full textAbstract:
Computational approaches play an important role in today's materials science owing to the remarkable advances in modern supercomputing architecture and algorithms. Ab initio simulations solely based on a quantum description of matter are now very able to tackle materials problems in which the system contains up to a few thousands atoms. This dissertation aims to address the modern electronic structure calculation methods applied to a range of various materials such as liquid and amorphous phase materials, nanostructures, and small organic molecules. Our simulations were performed within the density functional theory framework, emphasizing the use of real-space ab initio pseudopotentials. On the first part of our study, we performed liquid and amorphous phase simulations by employing a molecular dynamics technique accelerated by a Chebyshev-subspace filtering algorithm. We applied this technique to find l- and a- SiO₂ structural properties that were in a good agreement with experiments. On the second part, we studied nanostructured semiconducting oxide materials, i.e., SnO₂ and TiO₂, focusing on the electronic structures and optical properties. Lastly, we developed an efficient simulation method for non-contact atomic force microscopy. This fast and simple method was found to be a very powerful tool for predicting AFM images for many surface and molecular systems.<br>text