Thèses sur le sujet « Environmental geometry »
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1
Yu, Xiaomeng. « Stochastic modeling of rock fracture geometry ». Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12176.
Texte intégralRésumé :
Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993.Includes bibliographical references (second sequence, leaves 1-3).
by Xiaomeng Yu.
M.S.
2
Lee, Jun-Suk. « Stochastic and topological fracture geometry model ». Thesis, Massachusetts Institute of Technology, 1990. http://hdl.handle.net/1721.1/13598.
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Chatzipoulka, Christodouli. « Urban geometry and environmental performance in real urban forms ». Thesis, University of Kent, 2017. https://kar.kent.ac.uk/64332/.
Texte intégralRésumé :
Solar radiation is energy, a natural and inexhaustible source of heat and light, and as such a major factor to be considered for enhancing urban environmental sustainability. Solar availability on buildings determines to a large degree their active and passive solar potential; whereas, the insolation of open spaces affects their microclimate and in turn, their use and liveability. Solar objectives are thus multiple and may also be conflicting in time and space, especially in temperate climates, where thermal comfort needs vary in seasons. The subject of the thesis is the relationship between urban geometry and environmental performance of urban forms, explored at the neighbourhood scale and in real urban areas. Specifically, the research investigates statistically casual relationships of urban geometry with environmental phenomena related, directly or indirectly, to the availability of solar radiation. Full consideration is given to the varying solar geometry as a major parameter affecting the interaction between urban geometry and solar radiation, lending it a temporal and geographical -related to latitude- character. The research subject is explored through three distinct studies, which share the same methodology investigating particular topics under the same thematic umbrella. The first and the third study, in the order of these being presented, investigate phenomena occurring in open spaces, namely insolation and thermal diversity; whereas, the second study examines solar availability in open spaces and on building façades. In the methodology, urban geometry is distinguished into built density, which is associated negatively with solar availability but positively with sustainability at the city-scale, and urban layout. The former expresses total built volume in a site, and the latter is represented by a set of quantified geometric parameters which characterise the way in which the built volume is allocated and distributed within the site. This distinction aims to provide evidence for the significance of urban layout in modifying the solar urban environment as well as addressing conflicting solar design objectives. The performance of the urban forms is examined through a series of performance indicators, namely sky view factor, insolation, solar irradiance and thermal diversity values. Both urban geometry variables and performance indicators are calculated on average in each urban form. The great size of the sample analysed allows their relationships to be investigated in statistical means. The research belongs to the new era of urban environmental studies which make use of digital 3D models of cities to study spatially expressed phenomena in the built environment. It is based entirely on the analysis of existing urban forms, of 500x500m area, found in two European cities, London and Paris. London constitutes the main case study city, whereas Paris is examined for comparison purposes. The two cities are located at similar geographical latitudes and within the same climatic context, but their urban fabrics exemplify very different geometries. The geometric and environmental analysis of the urban forms as well as the elaboration and processing of the output data are performed using computer-based tools and methods, such as MATLAB software and image processing techniques applied in urban digital elevation models (DEMs) and, SOLWEIG and the RADIANCE-based software, PPF, for SVF and solar simulations. The research findings contribute to the field of urban environmental studies and design at multiple levels, presenting a significant theoretical, practical, and methodological value. First, they produce a critical insight about the factors affecting the relationship of urban geometry and sun-related phenomena occurring in the urban environment and lending it a dynamic character. In addition, they provide solid evidence about the enormous potential of urban geometry for promoting multiple -and sometimes conflicting- solar and urban design objectives, informing the relevant on-going discourse. Third, having as case studies real forms in London and Paris, a part of the findings is interpreted into urban design guidelines for enhancing the environmental performance of new and existing areas in the two cities. Last, as the research employs new methods and techniques to explore diverse topics, some of which are relatively new in the literature, it constitutes an important, methodological precedent for future research works.
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Heckel, Ayse Y. « Spider web geometry inspires long span roof trusses ». Thesis, Massachusetts Institute of Technology, 2020. https://hdl.handle.net/1721.1/127288.
Texte intégralRésumé :
Thesis: M. Eng., Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, May, 2020Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 16-18).
This research explores the methods and results used to learn from spider web geometries and implement them into a practical long span roof truss structure. Specifically, utilizing data and properties of spider webs found in research from Su et al. (Su I. a., 2016). The research uses and implements spider's web design blueprints in present day structural systems. Initially, the size of long span roof truss is determined by the finding the gravity and lateral loads applied an ordinary building structure based on the current building code. Then, the web geometry of a Crytophora citricola's, or tent web spider's web is analyzed and optimized for structural efficiency under loading. The performance of this spider-inspired truss geometry is then compared to a typical truss seen in construction today. This research demonstrates that many web geometries are optimal, or close to it, and are comparable in structural efficiency to the trusses currently used in structures. Therefore, architects and structural engineers can use building code to design irregular spider web-shaped trusses in many instances, for example, in architecturally aesthetic purposes or in reusing old structural materials.
by Ayse Y. Heckel.
M. Eng.
M.Eng. Massachusetts Institute of Technology, Department of Civil and Environmental Engineering
5
Wathugala, Deepa Nelumkanthi. « Stochastic three dimensional joint geometry : Modeling and verification ». Diss., The University of Arizona, 1991. http://hdl.handle.net/10150/185485.
Texte intégralRésumé :
Eight 3D (three dimensional) rock joint geometry modeling schemes which investigate statistical homogeneity, and incorporate corrections for sampling biases and applications of stereology are presented. A procedure for verification of the developed models also is presented. In this study, shape of the joints was assumed as circular. The models provide the number of joint sets, and for each joint set, the intensity, orientation, spacing, location and diameter distributions. Miller's method (1983) with new interpretations (Kulatilake et al., 1990b) and equal area polar plots were used together to identify the largest statistically homogenous region around the ventilation drift, Stripa mine, data of which were used for both modeling and verification. Four joint sets were found in this region. A general vector approach to correct sampling bias on joint orientation is presented. Corrected data as well as raw data were subjected to chi-square goodness-of-fit tests to check the suitability of hemispherical normal and Bingham distributions in representing orientation of joint sets. Only raw data of joint set 4 followed Bingham distribution. Therefore, joint set orientations were best represented as empirical distributions. Two methods are presented for the modeling of joint spacing, linear intensity and location. In each method, spacing distributions of joint sets were best represented by exponential distributions. Then, joint intensity and location distributions are represented by Poisson and uniform distributions respectively. Correction of sampling bias on joint spacing also is presented. Joint size modeling was carried out using two methods: area sampling survey method and scanline sampling survey method. In these two methods, corrections of sampling biases associated with joint size modeling are presented. 3D joint sizes were inferred from 2D trace length measurements using geometrical probability and conditional probability concepts. In both methods diameter distributions are represented by gamma distributions. For verification, joints were generated in a volume according to the statistical models, using Monte-Carlo simulation. This volume was intersected by planes to obtain joint traces on exposures of size and shape similar to the ones used to obtain field data. Characteristics of these predicted joint traces were compared with the field data in a statistical sense. For the rock mass under this study, the modeling scheme 3 was found to be the most suitable scheme.
6
He, Li-Xing. « A non-manifold geometry modeler : an object oriented approach ». Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/88810.
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Malek, Samar R. (Samar Rula). « The effect of geometry and topology on the mechanics of grid shells ». Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/74425.
Texte intégralRésumé :
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 128-131).
The use of grid shell structures in architecture and structural engineering has risen in the past decade, yet fundamental research on the mechanics of such structures is lacking. Grid shells are long span structures comprised of a lattice of single layer members forming a curved surface. Grid shells can be made of a wide range of materials from steel to wood. They have potential to be used in readapting existing spaces or in new aesthetically pleasing structures. By studying their mechanics, engineers can be more effective at the schematic phase of design so that the potential of grid shells can be maximized. This research conducts a parametric study that varies the topology and topography of grid shells. The parametric space is framed around real-world design constraints including the grid spacing, panel shape, span-to-height ratio and the use of double curvature. In this thesis, the buckling capacity is evaluated using finite element analysis for two typical grid shell geometries: the spherical cap and the corrugated vault. First, a spherical cap is considered for which an analytical solution exists and therefore the accuracy of the numerical procedure is validated. Simple closed-form solutions are derived using the concept of the equivalent continuum and compared to the numerical models. Then, the parametric study of the spherical cap is performed including variations of the grid spacing, the span to height ratio and the panel shape (triangles and quadrilaterals). Having determined the efficiency of the computational tool the study is extended to the barrel vault. Here the new features of the analysis are the use of double curvature by introducing corrugation along the edge and the crown. By understanding the fundamental mechanical behavior of grid shells, design guidelines aimed to maximize their capacity and efficiency and intended to facilitate the discussion between architect and engineer are proposed.
by Samar Rula Malek.
Ph.D.
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Parry, Scott R. « Free-Form Deformations in a Constructive Solid Geometry Modeling System ». BYU ScholarsArchive, 1986. https://scholarsarchive.byu.edu/etd/4255.
Texte intégralRésumé :
No one will question that computers are revolutionizing the design industry. It is pointed out in [Bezier84] that before CAD/CAM, a surface was defined by tracing cross sections on a drawing and then carving these sections in wood, plastic or metal. The final model was determined by someone interpolating between the sections. This labor intensive art is being replaced by techniques of computer aided geometric design.
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Schwarz, Brandon A. (Brandon Alexander). « Evaluation of a methodology for detecting railroad track geometry anomalies and determining rail vehicle fatigue loads ». Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12401.
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Baratti, Greta. « ENVIRONMENTAL GEOMETRY IN FISHES AND TORTOISES : EFFECT OF LANDMARKS, BEHAVIOURAL METHODOLOGIES, AND SENSORY CHANNELS ON SPATIAL REORIENTATION ». Doctoral thesis, Università degli studi di Trento, 2022. https://hdl.handle.net/11572/356341.
Texte intégralRésumé :
The present Thesis explored spatial reorientation behaviour of three species of fish (the zebrafish Danio rerio, the redtail splitfin fish Xenotoca eiseni, the goldfish Carassius auratus) and one species of reptiles (the Hermann tortoise Testudo hermanni) to widely assess three issues: 1) the use of environmental geometry with and without landmarks; 2) the role of two geometric tasks, one driven by spontaneous behaviour (“social-cued memory task”) and the other by learning processes (“rewarded exit task”); 3) the involvement of extra-visual sensory channels in visual transparency conditions, and motion patterns. The present Thesis applied behavioural assessments and analyses to pursue a line of comparison, across species, methodologies, and sensory systems. As regards environmental geometry and landmarks in fish and tortoises (Chapter 2), the studies were carried out within several apparatuses, that is, a rectangular opaque arena or two different sized square opaque arenas or a transparent square arena, with conspicuous or local landmarks: Study 1, Conspicuous landmark (blue wall) in zebrafish; Study 2: Local landmarks (corner panels) in zebrafish; Study 3, Environmental geometry in tortoises; Study 4, Conspicuous landmark (blue wall) in tortoises. As regards spontaneous vs. acquired geometric spatial reorientation in fishes (Chapter 3), the studies were carried out within a rectangular or square transparent arena, with or without geometric cues or a 3D landmark: Study 5, Nonvisual environmental geometry in zebrafish, redtail splitfin fish, and goldfish; Study 6, Isolated environmental geometric cues in zebrafish; Study 7, 3D outside landmark (blue cylinder) in zebrafish. As regards extra-visual sensory systems and motion patterns in fish (Chapter 4), one study was carried out within a rectangular transparent arena: Study 8, Lateral line pharmacological ablation in zebrafish. In respect of comparisons among species, overall results suggested that zebrafish, redtail splitfin fish, and goldfish reoriented similarly through transparent surfaces, which defined a distinctive global shape, supporting spatial reorientation under undefined situations (e.g., seek out food within a visually lacking and unenriched environment) as a shared skill among teleosts, despite ecological specificities. Likewise, the Hermann tortoise reoriented within a geometric environment with precision to meet a survival need, suggesting that even non-nomadic species that hibernate for long can benefit from orientation by extended terrain surfaces. In respect of memory tests (“working” vs. “reference”, spontaneous vs. acquired), overall results indicated that the rewarded exit task designed to train fish and tortoise to reorient required learning processes allowing them to overcome natural predispositions to improve other related abilities, such as landmark-use. The dissociation between working and reference memory in spatial domain must be considered highly dependent on task’s demands where attentional factors determine short-term memories and motivational states long-term ones. In respect of sensory channels and motion patterns, overall results revealed that fish and tortoises used modalities driven by touch, in synch with sight, to determine geometric parameters during spatial reorientation. Therefore, a promising link between other vertebrates and humans takes place, in consideration of orientation mechanisms used to face situations of visual deprivation or impairments. The present Thesis may even contribute to a general understanding of reorientation behaviour in phylogenetically remote vertebrate species, thus supporting the widespread use of geometry-grounded tools in everyday activities. This also provides comparative support among species that inhabit on Earth and share cognitive adaptations to deal with similar requests.
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Ouedraogo, Faissal Romaric. « Impact of Sludge Layer Geometry on the Hydraulic Performance of a Waste Stabilization Pond ». Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6344.
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Improving the hydraulic performance of waste stabilization ponds (WSPs) is an important management strategy to not only ensure protection of public health and the environment, but also to maximize the potential reuse of valuable resources found in the treated effluent. To reuse effluent from WSPs, a better understanding of the factors that impact the hydraulic performance of the system is needed. One major factor determining the hydraulic performance of a WSP is sludge accumulation, which alters the volume of the pond.
In this study, computational fluid dynamics (CFD) analysis was applied to investigate the impact of sludge layer geometry on hydraulic performance of a facultative pond, typically used in many small communities throughout the developing world. Four waste stabilization pond cases with different sludge volumes and distributions were investigated.
Results indicate that sludge distribution and volume have a significant impact on wastewater treatment efficiency and capacity. Although treatment capacity is reduced with accumulation of sludge, the latter may induce a baffling effect which causes the flow to behave closer to that of plug flow reactor and thus increase treatment efficiency. In addition to sludge accumulation and distribution, the impact of water surface level is also investigated through two additional cases. Findings show that an increase in water level while keeping a constant flow rate can result in a significant decrease in the hydraulic performance by reducing the sludge baffling effect, suggesting a careful monitoring of sludge accumulation and water surface level in WSP systems.
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McCune-Sanders, William J. « An Autothermal, Representative Scale Test Of Compost Heat Potential Using Geostatistical Analysis ». ScholarWorks @ UVM, 2018. https://scholarworks.uvm.edu/graddis/841.
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Composting has been practiced for thousands of years as a way of stabilizing and recycling organic matter into useful soil amendments. Thermophilic compost releases significant amounts of heat at temperatures (~140 °F) that are useful for environmental heating or process water. This heat has been taken advantage of in various ways throughout history, but development of a widely adopted technology remains elusive.
The biggest barrier to adoption of compost heat recovery (CHR) systems is projecting accurate, attractive economic returns. The cost of transfer equipment is significant, and with variability in composting substrates and methods, it is difficult to predict the power and quality of heat a proposed system would produce. While the ultimate heat release may be calculated with standard techniques, the dynamics of compost temperature and thermal power are less understood. As heat yield is one of many goals, better understanding of compost’s thermal dynamics is important for CHR optimization. This research addresses the issue by developing a field test that measures heat release and temperature across a representative-scale compost volume.
The compost test vessel was built from common construction materials and insulated enough to be self-heating in cold weather. A 4’ x 4’ x 4’ cube of 2” foam insulation panels held 1.812 cubic yards of active compost, intermittently aerated at ~35 CFM. Data from 84 temperature sensors, and one pressure sensor at the blower, was logged at 1-minute intervals for a period of 35 days. Spatial temperature fields were estimated by Kriging, and used to calculate conductive heat loss and compost volume temperature over time. Enthalpy loss was calculated using the blower pressure curve, temperature data and humidity assumptions.
The compost exhibited wide variation in temperature and heat flow over time, and less horizontal symmetry than expected. The results are dynamic and best viewed graphically. Enthalpy loss varied with adjustments to the aeration cycle, ranging from 100 to 550 W (60-minute average rates), while conductive losses were in the range of 75 W. Peak sustained thermal output was around 600 W (500 W by aeration) from days 11-13 with about 0.6 yd3 of compost in the thermophilic zone; however, this cooled the compost significantly. Aeration was then reduced, and the compost temperature recovered, with 50% - 90% of the compost volume above 130 °F from days 14-23; during this period, total heat loss was around 150 - 200 W with aeration loss around 60-100 W.
The test was successful in producing hot compost and building temperature field and heat loss models. However representative aeration rates cooled a large amount of the compost volume as cool air was drawn into the vessel. Aeration rate reduction accomplished desired compost temperatures, but resulted in low enthalpy extraction rate and temperature. Future work will address this issue with the ability to recirculate air through the compost.
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Ghanbarian-Alavijeh, Behzad. « Modeling Physical and Hydraulic Properties of Disordered Porous Media : Applications from Percolation Theory and Fractal Geometry ». Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1401380554.
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Barr, Jared Wendell. « A multiscale investigation of the role of variability in cross-sectional properties and side tributaries on flood routing ». Thesis, University of Iowa, 2012. https://ir.uiowa.edu/etd/3256.
Texte intégralRésumé :
A multi-scale Monte Carlo simulation was performed on nine streams of increasing Horton order to investigate the role that variability in hydraulic geometry and resistance play in modifying a flood hydrograph. This study attempts to determine the potential to replace actual cross-sections along a stream reach with a prismatic channel that has mean cross-sectional properties. The primary finding of this work is that the flood routing model is less sensitive to variability in the channel geometry as the Horton order of the stream increases. It was also established that even though smaller streams are more sensitive to variability in hydraulic geometry and resistance, replacing cross-sections along the channel with a characteristic reach wise average cross-section, is still a suitable approximation. Finally a case study of applying this methodology to a natural river is performed with promising results.
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Huber, Markus B. [Verfasser], et Gregor [Akademischer Betreuer] Morfill. « The relation between physical properties of galaxies and their environmental geometry in the Sloan Digital Sky Survey / Markus B. Huber. Betreuer : Gregor Morfill ». München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2015. http://d-nb.info/1081628898/34.
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Osta, Iman M. « From Physical Model To Proof For Understanding Via DGS : Interplay Among Environments ». Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-80806.
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The widespread use of Dynamic Geometry Software (DGS) is raising many interesting questions and discussions as to the necessity, usefulness and meaning of proof in school mathematics. With these questions in mind, a didactical sequence on the topic “Conics” was developed in a teacher education course tailored for pre-service secondary math methods course. The idea of the didactical sequence is to introduce “Conics” using a concrete manipulative approach (paper folding) then an explorative DGS-based construction activity embedding the need for a proof. For that purpose, the DGS software serves as an intermediary tool, used to bridge the gap between the
physical model and the formal symbolic system of proof. The paper will present an analysis of participants’ geometric thinking strategies, featuring proof as an embedded process in geometric construction situations.
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Osta, Iman M. « From Physical Model To Proof For Understanding Via DGS:Interplay Among Environments ». Proceedings of the tenth International Conference Models in Developing Mathematics Education. - Dresden : Hochschule für Technik und Wirtschaft, 2009. - S. 464 - 468, 2012. https://slub.qucosa.de/id/qucosa%3A1798.
Texte intégralRésumé :
The widespread use of Dynamic Geometry Software (DGS) is raising many interesting questions and discussions as to the necessity, usefulness and meaning of proof in school mathematics. With these questions in mind, a didactical sequence on the topic “Conics” was developed in a teacher education course tailored for pre-service secondary math methods course. The idea of the didactical sequence is to introduce “Conics” using a concrete manipulative approach (paper folding) then an explorative DGS-based construction activity embedding the need for a proof. For that purpose, the DGS software serves as an intermediary tool, used to bridge the gap between the
physical model and the formal symbolic system of proof. The paper will present an analysis of participants’ geometric thinking strategies, featuring proof as an embedded process in geometric construction situations.
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Paudel, Gaurab. « Hexahedral Mesh Refinement Using an Error Sizing Function ». BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/3447.
Texte intégralRésumé :
The ability to effectively adapt a mesh is a very important feature of high fidelity finite element modeling. In a finite element analysis, a relatively high node density is desired in areas of the model where there are high error estimates from an initial analysis. Providing a higher node density in such areas improves the accuracy of the model and reduces the computational time compared to having a high node density over the entire model. Node densities can be determined for any model using the sizing functions based on the geometry of the model or the error estimates from the finite element analysis. Robust methods for mesh adaptation using sizing functions are available for refining triangular, tetrahedral, and quadrilateral elements. However, little work has been published for adaptively refining all hexahedral meshes using sizing functions. This thesis describes a new approach to drive hexahedral refinement based upon an error sizing function and a mechanism to compare the sizes of the node after refinement.
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Medeiros, Margarete Farias. « Geometria dinâmica no ensino de transformações no plano : uma experiência com professores da educação básica ». reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/54888.
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Nesta dissertação apresentamos a concepção, implementação e validação de uma proposta para o ensino de transformações geométricas no plano usando o ambiente de geometria dinâmica GeoGebra. A proposta integra Geometria e Arte através da construção de pavimentações do plano e de mosaicos de Escher e foi dirigida para professores do ensino fundamental, tendo como objetivo apresentar uma nova alternativa de trabalho na Geometria escolar e também capacitá-los para o uso de mídias digitais nas suas salas de aula. O trabalho foi desenvolvido dentro dos princípios da Engenharia Didática. Na análise e validação da implementação da proposta tomamos como base a teoria Sócio-Histórica, cuja referência principal é a obra de Vygotsky; também utilizamos o trabalho de Duval sobre registros de representação semiótica no processo de aprendizagem da Matemática. A partir das análises a priori e a posteriori observamos que os professores participantes da oficina, através do uso do GeoGebra, se apropriaram dos princípios da geometria dinâmica e dos conceitos da geometria das transformações.This work presents the conception, implementation and validation of an experiment to teach geometric transformations in the plane using the dynamic geometry environment GeoGebra. The proposal integrates geometry and art through the construction of tessellations of the plane, including Escher's mosaics, and it was directed to elementary school teachers, aiming to present a new alternative to work with geometry using digital media. The work used the principles of Didactic Engineering and the analysis of the experiment was based on the Socio-Historical theory, whose main reference is the work of Vygotsky and on the work of Duval about registers of semiotic representation in the process of mathematics learning. The analysis a priori and a posteriori showed that the teachers, through the use of GeoGebra, learned the principles of dynamic geometry and the concepts of geometry transformations.
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Chan, Yip-cheung. « Experimental-theoretical interplay in dynamic geometry environments ». Click to view the E-thesis via HKUTO, 2009. http://sunzi.lib.hku.hk/hkuto/record/B41633921.
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Pandey, Sudip. « Assessment of forest community response to environmental variability by using an integrated approach from tree-ring anatomy to allometry of tree structures ». Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3426839.
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Climate change is the biggest challenge of this century and is exerting pressure on high altitude forests. Increase in global temperature along with the rise in CO2 in the atmosphere may change the structure and function of treeline species. Several studies showed the range shifts of trees towards higher altitude affecting growth, mortality, and composition of the forest. There are few studies carried out in Nepalese Himalaya at tree ring level but still miss the inter and intra annual information. To enhance our knowledge, the main objectives of the thesis is to understand the response of treeline species to climate change. This study provides knowledge on the competition between trees for the resources used in the natural forest which alters the structure and pattern of the forest ecosystem. The target species for wood anatomical and isotopic study were Abies spectabilis D. Don Mirb. and Betula utilis D. Don which is dominating in upper treeline of Himalayas.
I used the dendro-anatomy to assess the growth responses of xylem anatomical traits to climatic constraints. This allowed retrieving the information at a cellular level with longer time resolution. Further, the results were complemented by isotopic measurements that were inscribed in wood cellulose during their formation. Moreover, dendrometric data (DBH, crown radius, tree height) were collected from forest permanent plots located from different geographic locations (Nepal, Italy, and Romania). The data were used to test the crown allometries and their effects on natural forest structure and dynamics using crown area and crown volume models.
Wood anatomical studies of B. utilis showed mean ring width, mean vessel area, and ring specific hydraulic conductivity to positively correlated with summer temperatures. However, fibers were negatively correlated with same season temperature suggesting that fiber get narrower when the vessel is wider to maintain the xylem hydraulic system. Another, study based on dual isotope (carbon and oxygen) showed growing season water availability could be a supplementary limiting factor for this treeline species though high altitude species are mainly limited by low temperature. In such a condition, A. spectabilis, a high altitude conifer could benefit from its higher water use efficiency during the drier period taking the competitive advantage to gas exchange compare to B. utilis. The last part of a study on the crown geometry of natural forest showed trees are site-specific determining the structure of forest ecosystem through growth, mortality, and recruitment. The predicted number of trees calculated based on crown area/volume models suggested that natural forest is oriented towards a condition of space equivalence between tree-size classes, showing in parallel that the use of soil resources increment in higher tree classes.
In conclusion, this thesis provides information on wood anatomy and physiology of treeline species in response to global warming. Integration of crown models opens the idea how crown allometries contribute to a better understanding of forest communities and dynamics.
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Hsu, Ssuta S. « Automatic Meshing of Free-Form Deformation Solids ». BYU ScholarsArchive, 1989. https://scholarsarchive.byu.edu/etd/3453.
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Development of computer models and subsequent finite element analysis, are important aspects of modern engineering design. In this process, the geometry creation and finite element analysis software are well developed; however, the process of discretizing a geometry into a proper finite element model is time consuming and tedious. The work presented here uses the free-form deformation method to create smooth solid models, and invokes a solid subdivision and transition method to generate the hexahedron finite elements. The combination of these two techniques provides an automatic mesh generator that is easy to use, creates acceptable hexahedron elements for finite element analysis, and can model basically any complex shape.
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Frazee, Leah M. « The Interaction of Geometric and Spatial Reasoning : Student Learning of 2D Isometries in a Special Dynamic Geometry Environment ». The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1531862080144028.
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Or, Chi-ming. « Experimentation, construction, conjecturing and explanation in a dynamic geometry environment ». Click to view the E-thesis via HKUTO, 2005. http://sunzi.lib.hku.hk/hkuto/record/B35675007.
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Chan, Yip-cheung, et 陳葉祥. « Experimental-theoretical interplay in dynamic geometry environments ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2009. http://hub.hku.hk/bib/B41633921.
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HENRIQUE, Marcos Paulo. « GeoGebra no clique e na palma das m?os : contribui??es de uma din?mica de aula para constru??o de conceitos geom?tricos com alunos do ensino fundamental ». Universidade Federal Rural do Rio de Janeiro, 2017. https://tede.ufrrj.br/jspui/handle/jspui/2322.
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This investigation is focused on the development of activities, implementation (in the computer lab and in the classroom) and the analysis of learning of students in the 8th and 9th year of a public school in the city of Rio Claro (RJ). Specifically, the research considered the conceptual development in a teaching practice that values the dialogue, debate and writing, among other ways of registration, in a reflection with activities from the use of traditional GeoGebra (desktop) and GeoGebra application (version for smartphones). This analysis was not done to compare the two environments used, but identify contributions and challenges linked to the implementation of these resources for appropriation of knowledge. The concepts were polygons, regular polygons and parallel lines with a transverse. Data collection was carried out as follows: (a) audio recording, activities, geometric constructions files, photographic records and researcher's journal (implementation in the lab) and (b) audio and video recording, smartphones? screen capture used by students, and daily activities sheet of researcher (implementation in the classroom). In implementations of activities with computers, are highlighted the various forms of visualization and construction around the geometric object provided by dynamic geometry environment and mediation, as a tool of teaching work, as some contributions to the construction and development of the concept of regular polygon. It was observed during the implementation of the survey, some difficulties presented by the students related to handling of GeoGebra on a computer, as well as challenges to implementation of pedagogical practices in the computer lab, where multiple computers were defective. As contributions in the implementation of activities, stands out the motivator appeal, particularly, in working with parallel lines cut by transversal, using GeoGebra application. The experience showed and proved exciting, allowing the students to conclude that there are a set of elements (angles, straight position etc.), variants and invariants, along with the use and exploration of forms handled. As challenges, you can point out the difficulty of viewing properties in a building for cases where smartphone screen is small.
A presente investiga??o centrou-se na elabora??o de atividades, na implementa??o (no laborat?rio de inform?tica e em sala de aula) e na an?lise do aprendizado de alunos do 8? e 9? ano do Ensino Fundamental de uma escola p?blica de Rio Claro (RJ). Especificamente, a pesquisa analisou o desenvolvimento conceitual em uma pr?tica docente que valoriza o di?logo, a argumenta??o e a escrita, entre outras formas de registro em uma reflex?o com atividades a partir da utiliza??o do GeoGebra convencional (desktop) e o GeoGebra aplicativo (vers?o para smartphones). A an?lise n?o consiste em comparar os dois ambientes utilizados, mas identificar contribui??es e desafios atrelados ? implementa??o destes recursos para apropria??o do conhecimento. Os conceitos foram pol?gonos, pol?gonos regulares e retas paralelas com uma transversal. A coleta de dados foi realizada da seguinte maneira: (a) grava??o em ?udio, folha de atividades, os arquivos referentes ?s constru??es geom?tricas, registros fotogr?ficos e di?rio do pesquisador (implementa??o no laborat?rio) e (b) grava??o em ?udio e v?deo, captura da tela dos smartphones utilizados pelos estudantes, folha de atividades e di?rio do pesquisador (implementa??o em sala de aula). Em rela??o ?s implementa??es de atividades com computadores, destacamos as v?rias formas de visualiza??o e constru??o de um objeto geom?trico proporcionado pelo ambiente de geometria din?mica e a media??o, como ferramenta do trabalho docente, como algumas contribui??es para a constru??o e desenvolvimento do conceito de pol?gono regular. Observamos dificuldades apresentadas pelos estudantes no que se refere ao manuseio do GeoGebra em um computador, assim como desafios para implementa??o de pr?ticas pedag?gicas no laborat?rio de inform?tica, como v?rios computadores com defeito. Como contribui??es do smartphone na implementa??o de atividades, destacamos o apelo motivador que este recurso traz ?s aulas. Particularmente, no trabalho com retas paralelas cortadas por transversais, o uso GeoGebra aplicativo mostrou-se instigante por permitir aos alunos a observa??o de um conjunto de elementos (?ngulos, posi??o de retas etc.) variantes ou invariantes e, juntamente com o manuseio e explora??o das formas manuseadas. Como desafios ? poss?vel apontar a dificuldade de visualiza??o de propriedades em um constructo para casos em que a tela do smartphone ? pequena.
27
Gillis, John M. Martin W. Gary. « An investigation of student conjectures in static and dynamic geometry environments ». Auburn, Ala., 2005. http://repo.lib.auburn.edu/EtdRoot/2005/SPRING/Curriculum_and_Teaching/Dissertation/GILLIS_JOHN_2.pdf.
Texte intégral
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Olivero, Federica. « The proving process within a dynamic geometry environment ». Thesis, University of Bristol, 2003. http://hdl.handle.net/1983/ed52d690-e35f-4bd8-8a3a-74a8b7de5f7c.
Texte intégral
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Lee, Man-sang Arthur. « Impact of exploration in a dynamic geometry environment on students' concept of proof ». Hong Kong : University of Hong Kong, 1996. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18034019.
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Yu, Paul W. Presmeg Norma C. Barrett Jeffrey Edward. « Prototype development and discourse among middle school students in a dynamic geometric environment ». Normal, Ill. Illinois State University, 2004. http://wwwlib.umi.com/cr/ilstu/fullcit?p3172886.
Texte intégralRésumé :
Thesis (Ph. D.)--Illinois State University, 2004.Title from title page screen, viewed November 22, 2005. Dissertation Committee: Norma C. Presmeg, Jeffrey E. Barrett (co-chairs), Sherry L. Meier. Includes bibliographical references (leaves 186-194) and abstract. Also available in print.
31
Husain, Syed Farzad. « Perceiving dynamic environments : from surface geometry to semantic representation ». Doctoral thesis, Universitat Politècnica de Catalunya, 2016. http://hdl.handle.net/10803/403959.
Texte intégralRésumé :
Perceiving human environments is becoming increasingly fundamental with the gradual adaptation of robots for domestic use. High-level tasks such as the recognition of objects and actions need to be performed far the active engagement of the robot with its surroundings. Nowadays, the environment is primarily captured using visual information in the form of color and depth images.
Visual cues obtained from these images serve as a base upan which perception-related applications are developed. Far example, using appearance models far detecting objects and extracting motion infarmation far recognizing actions. However, given the complex variations of naturally occurring scenes, extracting a set of robust visual cues becomes harder here than in other contexts.
In this thesis, we develop a hierarchy of tools to improve the different aspects of robot perception in human-centered, possibly dynamic, environments. We start with the segmentation of single images and extend it to videos. Afterwards, we develop a surface tracking approach along with the incorporation of our video segmentation method. We then investigate the higher-level tasks of semantic segmentation and recognition. Finally, we focus on recognizing actions in videos. The introduction of Kinectstyle depth sensors is relatively new and its usage in the field of robotics cannot be found befare half a decade ago. Such sensors enable the acquisition of high-resolution color and depth images at a low cost. Given this opportunity, we dedícate a bulk of our work to the exploitation of the depth infarmation obtained using such sensors, thereby pushing forward the state-of-the-art in perception problems.
The thesis is conceptually grouped into two parts. In the first part, we address the low-level tasks of segmentation and tracking with depth images. In many cases, depth data gives a better disambiguation of surface boundaries of different objects in a scene when compared to their color counterpart. We exploit this information in a novel depth segmentation scheme that fits quadratic surface models on different surfaces in a competing fashion . We further extend the method to the video domain by initializing the segmentation results and surface model parameters from the previous trame for the next trame. In this way, we successfully create a video segmentation algorithm, in which the segment label belonging to each surface becomes coherent over time. We also devise a particle-filter-based tracker that uses depth data to track a surface. The tracker is made more robust by combining it with our video segmentation approach.
The segmentation results serve as a useful prior for high-level tasks. In the second part we deal with such tasks which include (i) object recognition, (ii) pixelwise object class segmentation, and (iii) action recognition . We propase (i) to address object recognition by creating context-aware conditional random field models. We show the importance of the context in object recognition by modeling geometrical relations between different objects in a scene. We perform (ii) object class segmentation using a convolutional neural network. We introduce a novel distance-from-wall feature and demonstrate its effectiveness in generating better class proposals for objects that are clase to the walls. The final part of the thesis deals with (iii) action recognition. We propase a 2D convolutional neural network extended to a concatenated 3D network that learns to extrae! features
from the spatio-temporal domain of raw video data. The network is trained to predict an action label for each video.
In summary, several perception aspects are addressed with the utilization of depth infarmation where available. Our main contributions are (a) the introduction of a depth video segmentation scheme, (b) a graphical model far object recognition, and our proposals of the deep learning models for (e) object class segmentation and (d) action recognition.Los sistemas de percepción en entornos humanos son cada vez más importantes para la adaptación gradual de los robots a tareas domésticas. Tareas de alto nivel, tales como el reconocimiento de objetos y acciones, son necesarias para conseguir la participación activa del robot en dichas tareas. Hoy en día el entorno del robot es capturado principalmente usando información visual en forma de imágenes de color y profundidad. Las características visuales obtenidas a partir de estas imágenes sirven como base para el desarrollo de aplicaciones relacionadas con la percepción del robot. Por ejemplo, el uso de modelos de apariencia para la detección de objetos y la extracción de información del movimiento para el reconocimiento de acciones. Sin embargo, dado que las escenas pueden contener variaciones complejas, la extracción de un conjunto de características visuales puede convertirse en una tarea muy difícil. En la presente tesis hemos desarrollado una jerarquía de herramientas para mejorar diferentes aspectos de la percepción del robot en entornos humanos, posiblemente dinámicos. Esta tesis comienza con la segmentación de imágenes individuales, que luego se extiende a vídeos. Posteriormente, diseñamos un enfoque de seguimiento de superficies que incorpora nuestro método de segmentación de vídeos. A continuación, investigamos tareas de alto nivel para la segmentación semántica y el reconocimiento. Finalmente, nos centramos en el reconocimiento de acciones en vídeos. La introducción de sensores de profundidad tipo Kinect es relativamente nueva y su uso en el campo de la robótica empezó hace tan solo media década. Tales sensores permiten la adquisición de color y profundidad de imágenes de alta resolución a bajo coste. Dada esta oportunidad, dedicamos una buena parte de nuestro trabajo a la explotación de la información de profundidad obtenida a través de dichos sensores, mejorando el estado del arte en problemas de percepción. La tesis está conceptualmente dividida en dos partes. En primer lugar, abordamos las tareas de bajo nivel de segmentación y seguimiento con imágenes de profundidad. En muchos casos, los datos de profundidad permite una mejor desambiguación de los límites de las superficies de diferentes objetos de una escena en comparación con los datos de color. Explotamos esta información en un nuevo esquema de segmentación de profundidad que ajusta modelos cuadráticos de superficies de forma competitiva. Extendemos el método a vídeos de modo que la etiquetación de superficies resulte coherente en el tiempo. También proponemos un rastreador basado en un filtro de partículas que utiliza los datos de profundidad para realizar el seguimiento de una superficie. El seguimiento se hace más robusto al combinarlo con nuestro enfoque de segmentación en vídeo. Los resultados de la segmentación son usados como información a priori para tareas de alto nivel. En la segunda parte nos ocupamos de este tipo de tareas que incluyen el (i) reconocimiento de objetos, (ii) la segmentación de clases de objetos a nivel de píxeles, y (iii) el reconocimiento de acciones. Proponemos (i) abordar el reconocimiento de objetos mediante la creación de modelos de campos aleatorios condicionales sensibles al contexto. Realizamos (ii) la segmentación de la clase del objeto utilizando una red neuronal de convolución. Se introduce una nueva característica de distancia-a-paredes y demostramos su eficacia en la mejora de la clasificación de objetos que están cerca de las paredes. La parte final de la tesis se ocupa del (iii) reconocimiento de acciones. Proponemos una red neuronal de convolución 2D extendida a una red 3D concatenada, que aprende a extraer las características del dominio espacio-temporal de los datos de vídeo. La red está capacitada para predecir la etiqueta de acción para cada vídeo.
32
Simsim, Mohammed Talal Electrical Engineering & Telecommunications Faculty of Engineering UNSW. « Geometry-based stochastic physical channel modeling for cellular environments ». Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2006. http://handle.unsw.edu.au/1959.4/26281.
Texte intégralRésumé :
Telecommunication has experienced significant changes over the past few years and its paradigm has moved from wired to wireless communications. The wireless channel constitutes the basic physical link between the transmitter and the receiver antennas. Therefore, complete knowledge of the wireless channel and radio propagation environment is necessary in order to design efficient wireless communication systems. This PhD thesis is devoted to studying the spatial and temporal statistics of the wireless channel in cellular environments based on a geometry-based stochastic physical channel modeling approach. Contributions in this thesis report include the following: ??? A new physical channel model called the eccentro-scattering model is proposed to study the spatial and temporal statistics of the multipath signals in cellular environments. ??? Generic closed-form formulas for the probability density function (pdf) of angle of arrival (AoA) and time of arrival (ToA) of the multipath signals in each cellular environment are derived. These formulas can be helpful for the design and evaluation of modern communication systems. ??? A new Gaussian scattering model is proposed, which consists of two Gaussian functions for the distribution of scatterers around base station (BS) and mobile station (MS) and confines these scatterers within a scattering disc. ??? The effect of mobile motion on the spatial and temporal statistics of the multipath signals in cellular environments is discussed. Three motion scenarios are considered for the possible trajectory of the mobile unit. Furthermore, two different cases are identified when the terrain and clutter of mobile surrounding have additional effect on the temporal spread of the multipath signals during motion. ??? The physical channel model is employed to assess the performance of a RAKE receiver in cellular environments. ??? Comparisons between uniform scattering and Gaussian scattering, which are the two assumptions for the distribution of scatterers usually used in the derivation of the pdf of AoA, are also presented. ??? An overview of earlier physical channel models and comparisons between these models and with the proposed model are presented.
33
Maiduang, Alongkot. « Dynamic geometry environment and its relation to thai students' higher-order thinking : reasoning in Euclidean geometry ». Thesis, King's College London (University of London), 2013. https://kclpure.kcl.ac.uk/portal/en/theses/dynamic-geometry-environment-and-its-relation-to-thai-students-higherorder-thinking(f3395341-41de-4cb5-9a0b-0c2834f681b7).html.
Texte intégralRésumé :
Since its introduction in the late 1980s, Dynamic Geometry Software (DGS) has become one of the most innovative tools in mathematics education. It is defined as graphical software, where geometric figures can be constructed with pre-defined relationships, which will retain when the figures are dynamically manipulated. This digital tool provides a new geometry learning environment inherently different from the traditional paper-and-pencil mode. This research investigates the situation where learners interact directly with this dynamic geometry environment. It examines how learners interpret DGS key features; such as drag-mode and parent-and-child relationship, and how such interpretations relate to their higher-order thinking of reasoning in geometric tasks. Three types of reasoning strategies are pursued in this research. These are: inductive reasoning, deductive reasoning and abductive reasoning. How and to what extent the DGS environment plays a role in the learner's reasoning strategies and arguments is the question at the focus of this research. Vygotsky's model of tool used as mediated activity and Verillon & Rabardel's Instrumented Activity Situation (IAS) model are used as a framework for this research. These models help to distinguish the independent roles of the learner, the DGS tool, the designed tasks and Euclidean geometry in the overall setting. They also help to clarify the influences that each of these entities may have on each other. The research is conducted in Thailand with a Thai version of The Geometer's Sketchpad to a group of 14-15 year-old lower secondary students. The research method used is a task-based interview, where pairs of students perform geometric construction and exploration tasks with Geometer's Sketchpad while the researcher challenges their reasoning. This research finds the tension between the deductive reasoning nature in Euclidean geometry, the inductive nature of visual presentation in the dynamic geometry environment, and the influence of students' experience in the paper-and-pencil environment on their interpretation of dynamic geometry. Abductive reasoning is found to be students' main reasoning strategy, with a combination of inductive and deductive reasoning to support their verification of the hypothesis.
34
Smith, Jaycee Cornwall. « Evaluation of Passive Force Behavior for Bridge Abutments Using Large-Scale Tests with Various Backfill Geometries ». BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/4107.
Texte intégralRésumé :
Bridge abutments are designed to withstand lateral pressures from thermal expansion and seismic forces. Current design curves have been seen to dangerously over- and under-estimate the peak passive resistance and corresponding deflection of abutment backfills. Similar studies on passive pressure have shown that passive resistance changes with different types of constructed backfills. The effects of changing the length to width ratio, or including MSE wingwalls determine passive force-deflection relationships. The purpose of this study is to determine the effects of the wall heights and of the MSE support on passive pressure and backfill failure, and to compare the field results with various predictive methods. To compare the effects of backfill geometries, three large-scale tests with dense compact sand were performed with abutment backfill heights of 3 ft (0.91 m), 5.5 ft (1.68 m), and 5.5 ft (1.68 m) confined with MSE wingwalls. Using an existing pile cap 11 ft (3.35 m) wide and 5.5 ft (1.68 m) high, width to height ratios for the abutment backfills were 3.7 for the 3ft test, and 2.0 for the 5.5ft and MSE tests. The failure surface for the unconfined backfills exhibited a 3D geometry with failure surfaces extending beyond the edge of the cap, increasing the "effective width", and producing a failure "bulb". In contrast, the constraint provided by the MSE wingwalls produced a more 2D failure geometry. The "effective width" of the failure surface increased as the width to height ratio decreased. In terms of total passive force, the unconfined 5.5ft wall provided about 6% more resistance than the 5.5ft MSE wall. However, in terms of passive force/width the MSE wall provided about 70% more resistance than the unconfined wall, which is more consistent with a plane strain, or 2D, failure geometry. In comparison with predicted forces, the MSE curve never seemed to fit, while the 3ft and 5.5ft curves were better represented with different methods. Even with optimizing between both the unconfined curves, the predicted Log Spiral peak passive forces were most accurate, within 12% of the measured peak resistances. The components of passive force between the unconfined tests suggest the passive force is influenced more by frictional resistance and less by the cohesion as the height of the backwall increases.
35
Or, Chi-ming, et 柯志明. « Experimentation, construction, conjecturing and explanation in a dynamic geometry environment ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2005. http://hub.hku.hk/bib/B35675007.
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Marlow, Kelsey A. « Clinical Interviews of Shape Understanding in a Dynamic Geometry Environment ». The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1492506014768381.
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Margelowsky, Gary R. « Characterization of seabed geometry in a free surface wave environment ». Connect to resource, 2008. http://hdl.handle.net/1811/35767.
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Morkel, Chantelle. « Non-interactive modeling tools and support environment for procedural geometry generation ». Thesis, Rhodes University, 2006. http://eprints.ru.ac.za/242/.
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Ustun, Isil. « Developing The Understanding Of Geometry Through A Computer-based Learning Environment ». Master's thesis, METU, 2003. http://etd.lib.metu.edu.tr/upload/4/1206523/index.pdf.
Texte intégralRésumé :
The main purpose of the study was to investigate the effects of
a dynamic instructional environment (based on use of Geometer&rsquos Sketchpad) on 7th grade students&rsquo
understandings of lines, angles, and polygons and their retention. Besides that, the students&rsquo
attitudes towards computer instruction and its relation with students&rsquo
performance on geometry and retention were investigated. The study was carried out with 63 7th grade students from two classes taught by the same teacher in a state elementary school. One class was assigned as the experimental group (EG), the other as the control group (CG). Students in CG received the instruction on lines, angles, and polygons by the regular traditional method used at the school. In the EG, students worked on the computer activities named as &ldquo
Sketchsheets&rdquo
, prepared by the researcher, with computers provided at the computer-lab. The usage of GSP with Sketchsheets enabled students to create the shapes first and after they explored and discovered the properties of shapes and make generalisations for the development of conjectures. Geometry Performance Test (GPT) and Computer Attitude Scale (CAS) were used in this study. The GPT was administered to both groups of students as a pre-test, post-test, and a delayed post-test. CAS was administered only to the EG students as a post-test. Furthermore, interviews were carried out with three students from EG in order to get their feelings about the dynamic instructional environment. Besides that, both of these classroom and computer sessions were observed and recorded with camera. The results of t-test suggest that GPT mean scores in EG and CG did not significantly differ in pre-test, but EG achieved significantly better than the CG in post and delay-post tests. CAS mean scores and interviews showed that students had positive feelings and decisions towards computer instruction and they preferred computer instruction to traditional instruction. Furthermore, Pearson product-moment correlation coefficient was performed in order to investigate the relationship between GPT scores and CAS scores. From this analysis, a significant correlation was observed between the GPT scores and CAS scores. This means that the students who had positive attitudes towards computer instruction, achieved significantly better at GPT. The results of this study revealed that Geometer&rsquo
s Sketchpad for learning and teaching geometry in elementary school level is an effective tool.
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Gunhan, Ali Can. « Environmental Effects On Quantum Geometric Phase And Quantum Entanglement ». Phd thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/3/12609450/index.pdf.
Texte intégralRésumé :
We investigate the geometric phase (GP) acquired by the states of a spin-1/2 nucleus which is subject to a static magnetic field. This nucleus as the carrier system of GP,
is taken as coupled to a dissipative environment, so that it evolves non-unitarily. We study the effects of different characteristics of different environments on GP as nucleus
evolves in time. We showed that magnetic field strength is the primary physical parameter that determines the stability of GPits stability decreases as the magnetic field strength increases. (By decrease in stability what we mean is the increase in the time rate of change of GP.) We showed that this decrease can be very rapid, and so it could be impossible to make use of it as a quantum logic gate in quantum information theory (QIT). To see if these behaviors differ in different environments, we analyze the same system for a fixed temperature environment which is under the influence of an electromagnetic field in a squeezed state. We find that the general dependence of GP on magnetic field does not change, but this time the effects are smoother. Namely, increase in magnetic field decreases the stability of GP also for in this environment
but this decrease is slower in comparison with the former case, and furthermore it occurs gradually. As a second problem we examine the entanglement of two atoms, which can be used as a two-qubit system in QIT. The entanglement is induced by an external quantum system. Both two-level atoms are coupled to a third two-level system by dipole-dipole interaction. The two atoms are assumed to be in ordinary vacuum and the third system is taken as influenced by a certain environment. We examined different types of environments. We show that the steady-state bipartite entanglement can be achieved in case the environment is a strongly fluctuating, that is a squeezed-vacuum, while it is not possible for a thermalized environment.
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Bustamante, Guillermo. « Influence of Pile Shape on Resistance to Lateral Loading ». BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5630.
Texte intégralRésumé :
The lateral resistance of pile foundations has typically been based on the resistance of circular pipe piles. In addition, most instrumented lateral load tests and cases history have involved circular piles. However, piles used in engineering practice may also be non-circular cross-section piles such as square and H piles. Some researchers have theorized that the lateral resistance of square piles will be higher than that of circular piles (Reese and Van Impe, 2001; Briaud et al, 1983; Smith, 1987) for various reasons, but there is not test data to support this claims. To provide basic comparative performance data, lateral load tests were performed on piles with circular, square and H sections. To facilitate comparisons, all the tests piles were approximately 12 inches in width or diameter and were made of steel. The square and circular pipe sections had comparable moments of inertia; however, the H pile was loaded about the weak axis, as is often the case of piles supporting integral abutments, and had a much lower moment of inertia. The granular fill around the pile was compacted to approximately 95% of the standard Proctor maximum density and would be typical of fill for a bridge abutment. Lateral load was applied with a free-head condition at a height of 1 ft above the ground surface. To define the load-deflection response, load was applied incrementally to produce deflection increments of about 0.25 inches up to a maximum deflection of about 3 inches. Although the square and pipe pile sections had nearly the same moment of inertia, the square pile provided lateral resistance that was 20 to 30% higher for a given deflection. The lateral resistance of the H pile was smaller than the other two pile shapes but higher than what it is expected based on the moment of inertia. Back analysis with the computer program LPILE indicates that the pile shape was influencing the lateral resistance. Increasing the effective width to account for the shape effect as suggested by Reese and Van Impe (2001) was insufficient to account for the increased resistance. To provide agreement with the measured response, p-multipliers of 1.2 and 1.35 were required for the square pile and H piles, respectively. The analyses suggest that the increased resistance for the square and H pile sections was a result of increases in both the side shear and normal stress components of resistance. Using the back-calculated p-multipliers provided very good agreement between the measured and computed load-deflection curves and the bending moment versus depth curves.
42
Archibald, Sally. « The adaptive geometrey {i.e. geometry} of savanna trees : a comparative study of the architecture and life history of Acacia karroo Hayne. in savanna, forest, and arid karoo shrubland environments ». Bachelor's thesis, University of Cape Town, 1998. http://hdl.handle.net/11427/24400.
Texte intégralRésumé :
Various morphological and life history attributes of Acacia karroo Hayne. were investigated in five populations from three environments in South Africa: forest (Cape Vidal, Natal), arid shrubland (Prince Albert, karoo) and savanna (Hluhluwe-Umfolozi Game reserve and ltala Game reserve, Natal). I aimed to elucidate on the distinctive characteristics required for trees to survive in savannas. The combination of frequent fires and intense herbivory in savanna environments creates a disturbance regime not encountered by trees in other situations and it was expected that A.karroo would display specific adaptations of growth form, life history, and reproductive ecology - adaptations which would reflect the strong selective pressure imposed by fire and herbivory on juvenile savanna trees to grow above flame height and browse limit in order to recruit into the mature canopy. A. karroo in savannas was found to have an unbranched, vertical growth form, and is thus maximising height gain. Reproduction was delayed until the trees were above the reach of flames and herbivores. Savanna A.karroo trees had fewer, smaller spines than trees in the other two environments, even though spines are generally considered to be effective in defense against mammalian herbivores. It is therefore suggested that a combination of low 'apparency' to browsers and rapid growth rate is an effective herbivore avoidance strategy in conditions where the need to escape from the fire trap makes a trade-off of growth rate for defensive structures unacceptable. The architecture of mature savanna trees reflects their history of rapid growth in earlier stages and they have smaller canopies, and thus lower reproductive capabilities, than equivalently sized trees in other environments.
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Lee, Man-sang Arthur, et 李文生. « Impact of exploration in a dynamic geometry environment on students' concept of proof ». Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1996. http://hub.hku.hk/bib/B3195876X.
Texte intégral
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Aguilar, Quiñones Valeria. « Impact of Viral Geometry and Cellular Lipid Environment on Virus-Endosome Fusion Kinetics ». Thesis, Uppsala universitet, Institutionen för medicinsk biokemi och mikrobiologi, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-446545.
Texte intégral
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Margelis, Georgios A. « Geometric abstractions for conceptual design support ». Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36487.
Texte intégralRésumé :
Thesis (Ocean. E.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994, and Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1994.Includes bibliographical references (leaves 151-154).
by Georgios A. Margelis.
M.S.
Ocean.E.
46
Sabaou, Nordine. « Sedimentology, geometry and depositional environments of the Triassic reservoirs of the Saharan Platform, Algeria ». Thesis, University of Birmingham, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431557.
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Gomes, Renata. « Uso de recursos tecnológicos para o ensino de matemática nos ensinos fundamental e médio ». Universidade Federal de Juiz de Fora, 2015. https://repositorio.ufjf.br/jspui/handle/ufjf/1440.
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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Este trabalho tem como objetivo central o uso de recursos tecnológicos para a implementação das aulas de matemática e também realizar atividades de cunho investigativo, onde haja uma maior interação do aluno com a ferramenta matemática a ser estudada. O software GeoGebra foi escolhido para a realização das tarefas propostas ao longo do texto por ser uma ferramenta dinâmica e acessível. Mais duas plataformas tecnológicas são usadas: o Google Sites e o Google Docs, sendo que ambas foram escolhidas por serem também gratuitas e de manuseio simples. Os recursos tecnológicos apresentados visam atender a realidade escolar por serem gratuitos e proporcionarem a realização das atividades de forma individual e/ou conjunta. As atividades elaboradas buscam dar subsídio aos professores da educação básica para a inserção da tecnologia em suas aulas. São tarefas, às vezes, muito simples mas com grande potencial didático-matemático. Muitas das vezes a geometria é colocada em segundo plano nas aulas de matemática e assim grande parte das atividades propostas aqui giram em torno de conceitos geométricos estudados ao longo das séries finais do Ensino Fundamental e de todo o Ensino Médio.
This work has as main objective the use of technological resources for the implementation of math classes and also perform activities with investigative purpose, in which has a greater interaction of students with the mathematical tool to be studied. GeoGebra software was chosen to carry out the tasks proposed in the text because it is a dynamic, accessible and friendly tool. Two more technology platforms are used: Google Sites and Google Docs, and both were chosen because they are also free and simple to handle. The presented technological resources aim to meet all kinds of school reality because they are free and provide the achievement of individual and/or group activities. The developed activities seek to give allowance to teachers of basic education to insert technology in their classes. Those tasks are, sometimes, very simple but with great didactic and mathematical potential. Very often the geometry is placed in the background in math classes, and therefore much of the activity proposed here surround geometric concepts studied during the final years of primary school and throughout high school.
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Gnanavelu, Abinesh Balasubramaniam. « A geometry independent integrated method to predict erosion wear rates in a slurry environment ». Thesis, University of Leeds, 2010. http://etheses.whiterose.ac.uk/4398/.
Texte intégralRésumé :
Material wear due to erosion-corrosion in slurry transport equipment is prevalent in process industries such as the oilsands industry. Damage to equipment can cost a typical oilsands industry nearly £200 million annually, along with an associated health and safety risk to man and environment [6]. New materials are continuously developed in order to endure wear under adverse erosion-corrosion conditions better and laboratory testing offers a good option to test new materials prior to commission. Traditionally the performance of a set of new materials are assessed based on their overall wear behavior in a laboratory test and is ranked accordingly, with the best performing material generally used for application. However, due to differences in prevailing conditions on the material surface and geometrical variations between actual and test geometry, accurately correlating data from a laboratory test to field scenario can be highly complex. Also the ranking system is not capable of predicting wear profiles for specific conditions and hence a new wear prediction method was developed and is presented in this thesis. This method has been developed, using a combination of standard laboratory based experiments and Computational Fluid Dynamic (CFD) simulations. As a starting point only wear due to erosion is considered and this thesis provides validation of such an approach. The method involves two stages in which (i) a universal wear map is generated for the material and abrasive combination in question using a standard laboratory test Uet impingement test) to generate a wear scar on a simple geometry. The local wear rate from this is interpreted using a CFD simulation of the test to generate a map giving local wear as a function of particle impact velocity and angle; (ii) a CFD solution is calculated for a series of different erosion configurations giving the particle impact data at each point on the surface. The wear map from the first stage is then used to give the local wear rate. The power of this method is that once a material-specific map has been generated then wear on any geometry can be calculated through the simulation of flow using CFD. As validation of this, wear on a typical plant geometry (1.50 90 0 elbow bend) is undertaken and the general applicability of this method is demonstrated.
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Joubert, Retief. « Influence of geometric and environmental parameters on air-cooled steam condenser performance ». Thesis, Stellenbosch : University of Stellenbosch, 2010. http://hdl.handle.net/10019.1/4153.
Texte intégralRésumé :
Thesis (MScEng (Mechanical and Mechatronic Engineering))--University of Stellenbosch, 2010.ENGLISH ABSTRACT: Air-cooled steam condensers (ACSCs) are used in the power generation industry to directly condense turbine exhaust steam in areas where cooling water is expensive or unavailable. Large axial flow fans force ambient air through A-frame heat exchanger bundles made up of a number of rows of finned tubes through which the steam is ducted and consequently condensed during the heat transfer process to the air. The heat rejection rate or performance of an ACSC is proportional to the air mass flow rate, determined by fan volumetric performance, and the temperature difference between the finned tubes and the air. The air flow through a 30 fan ACSC (termed the generic ACSC) operating under windy conditions is solved using the commercial computational fluid dynamics (CFD) code FLUENT and the required data is extracted from the solution to calculate performance trends. It is found that fan performance is reduced due to a combination of factors. The first is additional upstream flow losses caused by separated flow occurring primarily at the leading edge of the ACSC and secondarily at the fan bellmouth inlets. The second factor leading to reduced fan performance is the presence of distorted flow conditions at the fan inlets. Hot plume air recirculation is responsible for decreased ACSC thermal performance due to increased fan inlet air temperatures. It is found that reduced fan performance is the greater contributor to reduced ACSC performance. The performance effects of varying two geometrical parameters of the generic ACSC, namely the fan platform height and the windwall height, are investigated under windy conditions. It is found that each parameter is linked to a specific mechanism of performance reduction with the fan platform height affecting fan performance and the windwall height affecting recirculation. The respective platform and windwall heights specified for the generic ACSC are found to provide acceptable performance results. To mitigate wind induced performance reductions a number of modification and additions to the ACSC are investigated. These primarily aim at improving fan performance and included the addition of walkways or skirts, the addition of wind screens beneath the fan platform, removing the bellmouth fan inlets, using different types of fans and increasing fan power. The addition of a periphery walkway and windscreens is considered to be the most practical methods of improving ACSC performance under windy conditions. The generic ACSC is modified to include both modifications and under high wind conditions the performance is found to increase measurably. The modifications also resulted in the ACSC performance being less sensitive to wind direction effects.
AFRIKAANSE OPSOMMING: Lugverkoelde kondensators word in die kragopwekkings industrie gebruik om turbine uitlaatstoom te kondenseer, veral in gebiede waar verkoelingwater duur of onbeskikbaar is. Aksiaalvloei-waaiers forseer omgewingslug deur A-raam warmteuitruiler bondels wat bestaan uit verskeie rye vinbuise. Die uitlaatstoom vloei in die vinbuise en kondenseer as gevolg van die warmteoordrag na die lug. Die warmteoordragkapasiteit van die lugverkoelde stoom kondensator is eweredig aan die massavloei-tempo van die lug, wat bepaal word deur die waaierwerkverigting, en die temperatuur verskil tussen die vinbuise en die lug. Die lugvloei deur 'n 30 waaier lugverkoelde stoom kondensator (genoem die generiese lugverkoelde stoom kondensator) onderworpe aan winderige toestande word opgelos deur die gebruik van die kommersiële vloeidinamika-pakket, FLUENT. Die nodige data is onttrek uit die oplossing en werkverrigting neigings is bereken. Dit is gevind dat waaierwerkverigting verminder as gevolg van 'n kombinasie van faktore. Die eerste is bykomende vloeiverliese wat veroorsaak word deur vloeiwegbreking wat plaasvind primêr by die voorste rand van die lugverkoelde stoom kondensator asook by die klokvormige waaier-inlate. 'n Tweede faktor wat lei tot vermindere waaierwerkverigting is die teenwoordigheid van lugvloeiversteurings by die waaier-inlate. Hersirkulering van warm pluim lug is ook verantwoordelik vir verminderde lugverkoelde stoom kondensator werkverrigting. Daar word bevind dat die vermindering in waaierwerkverrigting die grootste bydraende faktor tot vermindere lugverkoelde stoom kondensator werkverrigting is. Die effek van verandering van twee geometriese lugverkoelde stoom kondensator parameters, naamlik die waaierplatformhoogte en die windwandhoogte is ondersoek onder winderige toestande. Daar word bevind dat elk van die parameters gekoppel is aan 'n spesifieke meganisme van vermindere lugverkoelde stoom kondensator verrigting: Die waaierplatformhoogte beïnvloed waaierverrigting terwyl die windwandhoogte hersirkulering beinvloed. Daar word ook bevind dat die onderskeie waaierplatform- and windwandhoogtes van die generiese lugverkoelde stoom kondensator, van so 'n aard is dat dit aanvaarbare werkverrigting tot gevolg het. Om verlaging in werksverrigting in winderige toestande te verminder is verskeie modifikasies en byvoegings tot die lugverkoelde stoom kondensator ondersoek wat primêr gemik is op verbetering in waaierwerkverigting. Die ondersoek dek die byvoeging van 'n loopvlak, die byvoeging van windskerms onder die waaierplatform, verwydering van die klokvormige waaier-inlate, die gebruik van verskillende waaiers en die verhoging van waaierdrywing. Daar was besluit dat die byvoeging van 'n loopvlak rondom die rand van die lugverkoelde stoom kondensator en die byvoeging van windskerms die mees praktiese manier was om die lugverkoelde stoom kondensator verigting te verbeter. Die generiese lugverkoelde stoom kondensator was aangepas om beide veranderings in te sluit en meetbare verbetering in werkrigting was verkry. Die veranderings het ook meegebring dat die lugverkoelde stoom kondensator minder sensitief is vir windrigting effekte.
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Yu, Jingjing. « MICROPHONE ARRAY OPTIMIZATION IN IMMERSIVE ENVIRONMENTS ». UKnowledge, 2013. http://uknowledge.uky.edu/ece_etds/19.
Texte intégralRésumé :
The complex relationship between array gain patterns and microphone distributions limits the application of traditional optimization algorithms on irregular arrays, which show enhanced beamforming performance for human speech capture in immersive environments. This work analyzes the relationship between irregular microphone geometries and spatial filtering performance with statistical methods. Novel geometry descriptors are developed to capture the properties of irregular microphone distributions showing their impact on array performance. General guidelines and optimization methods for regular and irregular array design are proposed in immersive (near-field) environments to obtain superior beamforming ability for speech applications. Optimization times are greatly reduced through the objective function rules using performance-based geometric descriptions of microphone distributions that circumvent direct array gain computations over the space of interest. In addition, probabilistic descriptions of acoustic scenes are introduced to incorporate various levels of prior knowledge for the source distribution. To verify the effectiveness of the proposed optimization methods, simulated gain patterns and real SNR results of the optimized arrays are compared to corresponding traditional regular arrays and arrays obtained from direct exhaustive searching methods. Results show large SNR enhancements for the optimized arrays over arbitrary randomly generated arrays and regular arrays, especially at low microphone densities. The rapid convergence and acceptable processing times observed during the experiments establish the feasibility of proposed optimization methods for array geometry design in immersive environments where rapid deployment is required with limited knowledge of the acoustic scene, such as in mobile platforms and audio surveillance applications.