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Zirbel, Shannon Alisa. "Compliant Mechanisms for Deployable Space Systems." BYU ScholarsArchive, 2014. https://scholarsarchive.byu.edu/etd/5612.
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The purpose of this research is to develop fundamentals of compliant mechanisms in deployable space systems. The scope was limited to creating methods for thick origami, developing compliant deployable solar arrays, and developing methods for stowing and deploying the arrays. The research on actuation methods was focused on a one-time deployment of the array. Concepts for both passive and active actuation were considered. The primary objective of this work was to develop approaches to accommodate thickness in origami-based deployable arrays with a high ratio of deployed-to-stowed diameter. The HanaFlex design was derived from the origami flasher model and is developed as a deployable solar array for large arrays (150 kW or greater) and CubeSat arrays (60 W). The origami folding concept enables compact stowage of the array, which would be deployed from a hexagonal prism into a flat array with about a 10-times increase in deployed diameter as compared to stowed diameter. The work on the origami pattern for the solar array was also applied to the folding of 80-100 m2 solar sails for two NASA CubeSat missions, NEA-Scout and Lunar Flashlight. The CubeSat program is a promising avenue to put the solar array or solar sails into space for testing and proving their functionality. The deployable array concept is easily scalable, although application to CubeSats changes some of the design constraints. The thickness-to-diameter ratio is larger, making the issues of thickness more pronounced. Methods of actuation are also limited on CubeSats because of the rigorous size and weight constraints. This dissertation also includes the development of a compact, self-deploying array based on a tapered map fold design. The tapered map fold was modified by applying an elastic membrane to one side of the array and adequately spacing the panels adjacent to valley folds. Through this approach, the array can be folded into a fully dense stowed volume. Potential applications for the array include a collapsible solar array for military or backpacking applications. Additional compliant mechanism design was done in support of the HanaFlex array. This included a serpentine flexure to attach the array to the perimeter truss for deployment, and a bistable mechanism that may be used in the deployment of the array or sail.
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Merriam, Ezekiel G. "Fully Compliant Mechanisms for Bearing Subtraction in Robotics and Space Applications." BYU ScholarsArchive, 2013. https://scholarsarchive.byu.edu/etd/3564.
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Robotics and space applications represent areas where compliant mechanisms can continue to make a significant impact by reducing costs and weight while improving performance. Because of the nature of these applications, a common need is for bearing replacement mechanisms, or mechanisms that perform the function of a bearing without the complexity and failure modes associated with bearings. Static balancing is a design strategy that attempts to reduce the actuation effort of a mechanism, and has been applied to compliant mechanisms in some applications. Monolithic construction, especially by means of 3D printing technology, is a strategy whereby the mechanism links and joints are built as a single "chunk" of material. This eliminates assembly and failure modes associated with wear and friction in traditional joints. In this work we examine these design strategies in the context of robotics and space applications. Matlab and Ansys batch files can be found in Appendix A. A fully compliant zero-torque, statically balanced mechanism is described that can undergo greater than 100 of motion. Because compliant mechanisms achieve their motion from the deflection of their constituent members, there is some strain energy associated with actuated positions. By introducing an appropriate pre-load, strain energy can be held constant. This can reduce or nearly eliminate the input force required from the actuating device. This paper describes the statically balanced rotary joint concept, and demonstrates its optimization, testing, and implementation for a haptic pantograph mechanism. The statically balanced properties of the constituent joints result in a mechanism with two balanced degrees of freedom. Matlab and Ansys batch files can be found in Appendix B. The conception, modeling, and development of a fully compliant two-degree-of-freedom pointing mechanism for application in spacecraft thruster, antenna, or solar array systems is described. The design objectives and the advantages of a compliant solution are briefly discussed. A single design concept is selected for final development from a field of generated concepts. Analytical and numerical models are accompanied by prototype testing and measurements in several iterations. A final design is described in detail, a fully compliant prototype is fabricated in titanium, and its performance is measured.
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Manganas, Phanee. "Oxidative regulation mechanisms in the mitochondrial intermembrane space." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8568/.
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Oxidative stress occurs when cells are unable to cope with the levels of various reactive oxygen species (ROS) that arise as part of regular cellular metabolism or in response to ionising radiation (H2O2, O2-, OH-). The most well studied ROS is H2O2, due to its dual role as a mediator of oxidative stress and a signalling molecule for many cellular pathways. Cells possess a number of different mechanisms to combat ROS, in order to prevent their levels from becoming toxic. In this thesis, we studied three different aspects of the antioxidant defence in Saccharomyces cerevisiae. In the first part, we explored the role of erythroascorbic acid – the yeast analogue of ascorbic acid (vitamin C) – and attempted to determine its role as an antioxidant in yeast. Our results were inconclusive, though there were indications that the presence of erythroascorbic acid may have a protective effect on the mitochondrial inner membrane potential (ΔΨ), protecting it from depolarisation. The second part focused on elucidating the mitochondrial targeting of the main H2O2 sensor Gpx3 and, more specifically, whether the Yap1-binding proteins, Ybp1 and Ybp2, have an effect on the import of Gpx3 in yeast mitochondria. Our results show a slight effect of Ybp1 (but not Ybp2) on the import of Gpx3, indicating that Ybp1 may act as a chaperone for the more efficient targeting of Gpx3 from the cytosol to the outer mitochondrial membrane and, as a result, its eventual translocation into the IMS. The final part of this thesis focused on elucidating the import of Trx1 and Trr1 in the mitochondrial IMS, as well as their function in this particular subcompartment. The discovery of two members of the thioredoxin system in the IMS is important, due to the absence of a known reducing mechanism in this oxidising compartment. Our results determined that several well-known import factors are dispensable for the import of either Trx1 or Trr1, indicating that they follow a yet unknown pathway for their translocation into the IMS. Importantly, we showed that Trx1 is reduced (and thus, active) in the IMS and that it can interact in vitro with both components of the MIA machinery (Mia40 and Erv1), while in organello experiments showed that Trx1 most probably interacts with a large number of Mia40 substrates.
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Regueiro, Richard Anderson. "Modeling passing damping mechanisms of large space structures." Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/49912.
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Fried, Limor. "Social defense mechanisms : tools for reclaiming our personal space." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33151.
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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2005.Includes bibliographical references (leaf 67).
In contemporary Western society, electronic devices are becoming so prevalent that many people find themselves surrounded by technologies they find frustrating or annoying. The electronics industry has little incentive to address this complaint; I designed two counter-technologies to help people defend their personal space from unwanted electronic intrusion. Both devices were designed and prototyped with reference to the culture-jamming "Design Noir" philosophy. The first is a pair of glasses that darken whenever a television is in view. The second is low- power RF jammer capable of preventing cell phones or similarly intrusive wireless devices from operating within a user's personal space. By building functional prototypes that reflect equal consideration of technical and social issues, I identify three attributes of Noir products: Personal empowerment, participation in a critical discourse, and subversion.
by Limor Fried.
M.Eng.
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Takaya, Yuri. "Space security and international law : verification and monitoring mechanisms." Paris 11, 2009. http://www.theses.fr/2009PA111020.
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Godsall, Ben. "Mechanisms of space use in the wood mouse, Apodemus sylvaticus." Thesis, Imperial College London, 2015. http://hdl.handle.net/10044/1/25280.
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"Space use" describes a wide set of movement behaviours that animals display to acquire the resources necessary for their survival and reproductive success. Studies across taxa commonly focus on the relationships between space use and individual-, habitat- and population-level factors. There is growing evidence, however, that variation in space use between individuals can also occur due to differences in 'personalities' and genetic variation between individuals. Using a wild population of the European wood mouse, Apodemus sylvaticus, this thesis aims to: i) investigate the roles of individual-level (body mass, body fat reserves and testosterone), habitat-level (Rhododendron and logs) and population-level (population density, sex ratio and season) factors as drivers of individual variation in the emergent space use patterns of individual home range size and home range overlap, estimated using spatial data collected in a mixed-deciduous woodland over three years. ii) Establish a link between genes and space use through the heritability and response to selection of phenotypic traits linked to individual variation in space use. A pedigree of the population is reconstructed from microsatellite data. Individual reproductive success is estimated from it and used to estimate selection gradients for three phenotypic traits. Heritability estimates are calculated using the animal model and together with selection gradients are used to predict the generational change in the population mean of traits using the Breeders equation. The results of this thesis suggest that the mechanism behind space use in this population of A. sylvaticus involves interactions between season, habitat, sex and the three individual-level factors (body mass, body fat and testosterone). The heritability of traits linked to emergent space use patterns suggests indirect effects of genes on individual variation in space use. Small responses to selection for traits suggests that gene-driven changes to space use patterns will most likely be indistinguishable between generations.
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Sonner, Sarah. "Black Boxes : Airport Space, Liminal Mechanisms, and Systems of Autobiography." Thesis, Goldsmiths College (University of London), 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499155.
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Treating the first-person experience of airport space as an ethnographic tool, this thesis examines spatial perception and its breakdown in multiple examples of imagined and real twentiethcentury spatial constructs. First, it considers examples of failed or redundant mechanisms which function as liminal constructs, either through their presence as physical objects or through use as tools with which to perceive liminal spaces. It emphasizes their function as points of access for narrative and delineates their status as examples of failure in relation to Bruno Latour's use of the term "black box," appropriated from the world of air crash investigation, and to Walter Benjamin's collection and juxtaposition of research in Tbe Arcades Project. Second, it explores the type and sequence of spaces encountered by a traveller in a large contemporary international airport, and those behaviours that are inscribed and prescribed upon people and mechanisms therein. It critiques Marc Auge' s ideas of the "non-place" through explorations of a distinctly airport-specific culture and possible deconstructions of airport space by passenger use and mechanical and architectural functions. Finally, it relates these to narrative space through an examination and practice of systemic approaches to autobiography in works by Georges Perec, Michel Leiris, and Raymond Queneau. It uses the first-person construction of a narrative of airport space-a first-person "silent reading" of public space-to construct a system of research through which twentieth-century liminal space may be inhabited and critiqued from within and on its own terms. Thus the constraint and potential offered by these diverse liminal spaces are deconstructed in terms of the personal narrative, and through use of airport space demonstrate an inhabiting of research through an innovative and revealing method
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Burton, Pamela Ann. "Physiological evidence of interactive object-based and space-based attention mechanisms." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file 50.79Mb,139 p, 2005. http://wwwlib.umi.com/dissertations/fullcit/3157279.
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Fowler, Robert McIntyre. "Investigation of Compliant Space Mechanisms with Application to the Design of a Large-Displacement Monolithic Compliant Rotational Hinge." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3305.
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The purpose of this research is to investigate the use of compliant mechanisms in space applications and design, analyze, and test a compliant space mechanism. Current space mechanisms are already highly refined and it is unclear if significant improvements in performance can be made by continuing to refine current designs. Compliant mechanisms offer a promising opportunity to change the fundamental approach to achieving controlled motion in space systems and have potential for dramatic increases in mechanism performance given the constraints of the space environment. A compliant deployment hinge was selected for development after industry input was gathered. Concepts for large-displacement compliant hinges are investigated. A design process was developed that links the performance requirements of deployment to the design parameters of a deployment hinge. A large-displacement monolithic compliant rotational hinge, the Flex-16, is designed, analyzed, and tested. It was developed for possible application as a spacecraft deployment hinge and designs were developed using three different materials (polypropylene, titanium, and carbon nanotubes) and manufacturing processes (CNC milling, electron beam manufacturing metal rapid prototyping, and a carbon nanotube framework) on two size scales (macro and micro). A parametric finite element model allowed for prediction of prototype behavior before fabrication. The Flex-16 hinge is capable of 90 degrees of deflection without failure or contact and can be designed to meet industry requirements for space.
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Björnström, Karlsson Karin. "Cellular mechanisms of anaesthetic agents /." Linköping : Univ, 2003. http://www.bibl.liu.se/liupubl/disp/disp2003/med777s.pdf.
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Shah, Dignesh. "Novel expansion mechanisms for space creation and organ retraction during laparoscopic surgery." Thesis, Sheffield Hallam University, 2018. http://shura.shu.ac.uk/21653/.
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Seitz, Amee. "Mechanisms of Rotator Cuff Disease: Alterations of Scapular Kinematics on Subacromial Space." VCU Scholars Compass, 2010. http://scholarscompass.vcu.edu/etd/2271.
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Rotator cuff disease is multi-factored and has been attributed to both intrinsic and extrinsic factors. Extrinsic factors contribute to compression of the rotator cuff tendons. Intrinsic factors that contribute to rotator cuff tendon degradation with tensile/shear overload include alterations in biology, mechanical properties, morphology, and vascularity. Subacromial impingement is related to factors that encroach upon the subacromial space, while internal impingement affects the articular side of the tendons adjacent to glenoid. While the mechanisms of impingement are varied, further research is necessary to improve treatment and patient outcomes. Chapter 2 is a thorough review of literature on the mechanisms of rotator cuff disease. Alterations in scapular kinematics may influence subacromial space and either contribute to the etiology of subacromial impingement with rotator cuff tendon compression or serve as a compensation to alleviate compression. Furthermore alterations in scapular position may directly influence rotator cuff muscle strength. Chapter 3 compares the influence of the scapular assistance test on scapular upward rotation, posterior tilt, subacromial space, and shoulder strength between healthy individuals and subjects with subacromial impingement syndrome. Scapular upward rotation and posterior tilt induced with scapular assistance test appears to influence subacromial space, but not shoulder muscle strength; however, the influence of these scapular rotations do not differ between asymptomatic individuals and those with subacromial impingement. Furthermore scapular posterior tilt appears to have a greater influence on increasing subacromial space and should be emphasized in the treatment of individuals with subacromial impingement. In chapter 4, we examine the influence that obvious scapular dyskinesis and passive scapular correction with the scapular assistance test have on 3D scapular kinematics and subacromial space. Scapular dyskinesis did not alter scapular kinematics or acromiohumeral distance during active elevation in static positions, in the scapular plane, and without a load when compared to those without scapular dyskinesis. This suggests other contributing factors, such as pain, increased load, or fatigue is requisite to alterations in scapular kinematics or AHD. Passive correction with the scapular assistance test increased scapular upward rotation, posterior tilt, and subacromial space in individuals with and without dyskinesis. In patients with obvious dyskinesis, there was a greater increase in scapular upward rotation with passive scapular assistance. This increased scapular upward rotation had a negative relationship with change in the acromiohumeral distance. The scapular dyskinesis test increased acromiohumeral distance and therefore may be helpful identifying individuals where subacromial compression is producing symptoms, regardless of dyskinesis. The results of this research suggest scapular kinematics and subacromial space are altered with the passive maneuver of the scapular assistance test in all individuals, regardless of subacromial impingement syndrome or scapular dyskinesis. Scapular dyskinesis alone may not be detrimental to scapular position and subacromial space when evaluated in static positions of active arm elevation. Other potential factors may be required to alter scapular kinematics to reduce subacromial space including pain, dynamic movement, load or fatigue. Further study is necessary to determine the influence of the combination of these factors in individuals with scapular dyskinesis.
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Rainville, Stéphane Jean Michel. "The spatial mechanisms mediating the perception of mirror symmetry in human vision /." Thesis, McGill University, 1999. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=36688.
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The present thesis reports psychophysical and modeling studies on the spatial properties of visual mechanisms mediating the perception of mirror symmetry in human vision. In a first set of experiments, patterns were filtered for power spectra that decayed with spatial frequency according to variable slopes. Results revealed that symmetry detection is optimal if contrast energy is roughly equated across log-frequency bands (i.e. 1/f2) and that, under such conditions, spatial scales contribute equally and independently to symmetry perception. In a second study, random-noise patterns were filtered for various orientation bands. Results showed that symmetry perception is possible at all orientations, is mediated by oriented mechanisms, and is computed independently in different orientation channels. Data also revealed that the dimensions of the spatial integration region (IR) for symmetry vary with orientation in a way that approximately matches the spatial distribution of information in the stimulus. Finally, symmetry detection was measured for bandpass textures of variable spatial density and variable contrast polarity. For such patterns, it was found that symmetry is computed at a spatial scale proportional to stimulus density and that mechanisms insensitive to contrast polarity (i.e. second-order) are involved in the scale-selection process.Overall, results from empirical and modeling work revealed an intimate link between symmetry perception and the properties of spatial filters. In particular, I argue that the size of the IR tends to vary such that a fixed amount of information is integrated irrespective of the spatial properties of the stimulus. Implications for the functional architecture of symmetry perception are discussed, and a paradigm for future research in symmetry perception is proposed in which spatial filtering is extended to higher orders of spatial complexity.
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Gonon, Géraldine. "Space radiation-induced bystander effect : kinetics of biologic responses, mechanisms, and significance of secondary radiations." Phd thesis, Université de Franche-Comté, 2011. http://tel.archives-ouvertes.fr/tel-00987717.
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Widespread evidence indicates that exposure of cell cultures to α particles results in significant biological changes in both the irradiated and non-irradiated bystander cells in the population. The induction of non-targeted biological responses in cell cultures exposed to low fluences of high charge (Z) and high energy (E) particles is relevant to estimates of the health risks of space radiation and to radiotherapy. Here, we investigated the mechanisms underlying the induction of stressful effects in confluent normal human fibroblast cultures exposed to low fluences of 1000 MeV/u iron ions (linear energy transfer (LET) ~151 keV/µm), 600 MeV/u silicon ions (LET ~50 keV/µm) or 290 MeV/u carbon ions (LET ~13 keV/µm). We compared the results with those obtained in cell cultures exposed, in parallel, to low fluences of 0.92 MeV/u α particles (LET ~109 keV/µm).Induction of DNA damage, changes in gene expression, protein carbonylation and lipid peroxidation during 24 h after exposure of confluent cultures to mean doses as low as 0.2 cGy of iron or silicon ions strongly supported the propagation of stressful effects from irradiated to bystander cells. At a mean dose of 0.2 cGy, only ~1 and 3 % of the cells would be targeted through the nucleus by an iron or silicon ion, respectively. Within 24 h post-irradiation, immunoblot analyses revealed significant increases in the levels of phospho-TP53 (serine 15), p21Waf1 (also known as CDKN1A), HDM2, phospho-ERK1/2, protein carbonylation and lipid peroxidation. The magnitude of the responses suggested participation of non-targeted cells in the response. Furthermore, when the irradiated cell populations were subcultured in fresh medium shortly after irradiation, greater than expected increases in the levels of these markers were also observed during 24 h. Together, the results imply a rapidly propagated and persistent bystander effect. In situ analyses in confluent cultures showed 53BP1 foci formation, a marker of DNA damage, in more cells than expected based on the fraction of cells traversed through the nucleus by an iron or silicon ion. The effect was expressed as early as 15 min after exposure, peaked at 1 h and decreased by 24 h. A similar tendency occurred after exposure to a mean absorbed dose of 0.2 cGy of 3.7 MeV α particles, but not after 0.2 cGy of 290 MeV/u carbon ions.Analyses in dishes that incorporate a CR-39 solid state nuclear track detector bottom identified the cells irradiated with iron or silicon ions and further supported the participation of bystander cells in the stress response. Mechanistic studies indicated that gap junction intercellular communication, DNA repair, and oxidative metabolism participate in the propagation of the induced effects.We also considered the possible contribution of secondary particles produced along the primary particle tracks to the biological responses. Simulations with the FLUKA multi-particle transport code revealed that fragmentation products, other than electrons, in cells cultures exposed to HZE particles comprise <1 % of the absorbed dose. Further, the radial spread of dose due to secondary heavy ion fragments is confined to approximately 10-20 µm Thus, the latter are unlikely to significantly contribute to the stressful effects in cells not targeted by primary HZE particles.
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Lusk, Craig P. "Ortho-Planar Mechanisms for Microelectromechanical Systems." Diss., CLICK HERE for online access, 2005. http://contentdm.lib.byu.edu/ETD/image/etd902.pdf.
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Chattopadhyay, Sutapa. "INVOLUNTARY MIGRATION AND THE MECHANISMS OF REHABILITATION: THE DISCOURSES OF DEVELOPMENT IN SARDAR SAROVAR, INDIA." [Kent, Ohio] : Kent State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=kent1154376293.
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Thesis (Ph.D.)--Kent State University, 2006.Available online via OhioLINK's ETD Center. Title from PDF t.p. (viewed June 19, 2007). Advisor: James A Tyner. Keywords: involuntary migration, space, gender, discourse analysis, Sardar Sarovar project, tribals. Includes bibliographical references (p. 157-171).
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Purschke, Ralf [Verfasser], Ulrich [Akademischer Betreuer] Walter, and Enrico [Akademischer Betreuer] Stoll. "Synthetic Gear Wheels for Space Mechanisms / Ralf Purschke. Betreuer: Ulrich Walter. Gutachter: Ulrich Walter ; Enrico Stoll." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1088724876/34.
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Abraham, Douglas Scott. "Imposing management control mechanisms on public programs : a comparison of the Polaris and space station programs." Thesis, Georgia Institute of Technology, 1990. http://hdl.handle.net/1853/28949.
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Purschke, Ralf Verfasser], Ulrich [Akademischer Betreuer] [Walter, and Enrico [Akademischer Betreuer] Stoll. "Synthetic Gear Wheels for Space Mechanisms / Ralf Purschke. Betreuer: Ulrich Walter. Gutachter: Ulrich Walter ; Enrico Stoll." München : Universitätsbibliothek der TU München, 2015. http://nbn-resolving.de/urn:nbn:de:bvb:91-diss-20151201-1250675-1-1.
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Rathod, Chirag. "Examining Plasma Instabilities as Ionospheric Turbulence Generation Mechanisms Using Pseudo-Spectral Methods." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/102892.
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Turbulence in the ionosphere is important to understand because it can negatively affect communication signals. This work examines different scenarios in the ionosphere in which turbulence may develop. The two main causes of turbulence considered in this work are the gradient drift instability (GDI) and the Kelvin-Helmholtz instability (KHI).
The likelihood of the development of the GDI during the August 17, 2017 total solar eclipse is studied numerically. This analysis uses the ``Sami3 is Also a Model of the Ionosphere" (SAMI3) model to study the effect of the eclipse on the plasma density. The calculated GDI growth rates are small compared to how quickly the eclipse moves over the Earth. Therefore, the GDI is not expected to occur during the solar eclipse.
A novel 2D electrostatic pseudo-spectral fluid model is developed to study the growth of these two instabilities and the problem of ionospheric turbulence in general. To focus on the ionospheric turbulence, a set of perturbed governing equations are derived. The model accurately captures the GDI growth rate in different limits; it is also benchmarked to the evolution of instability development in different collisional regimes of a plasma cloud.
The newly developed model is used to study if the GDI is the cause of density irregularities observed in subauroral polarization streams (SAPS). Data from Global Positioning System (GPS) scintillations and the Super Dual Auroral Radar Network (SuperDARN) are used to examine the latitudinal density and velocity profiles of SAPS. It is found that the GDI is stabilized by velocity shear and therefore will only generate density irregularities in regions of low velocity shear. Furthermore, the density irregularities cannot extend through regions of large velocity shear. In certain cases, the turbulence cascade power laws match observation and theory.
The transition between the KHI and the GDI is studied by understanding the effect of collisions. In low collisionality regimes, the KHI is the dominant instability. In high collisionality regimes, the GDI is the dominant instability. Using nominal ionospheric parameters, a prediction is provided that suggests that there exists an altitude in the upper textit{F} region ionosphere above which the turbulence is dominated by the KHI.Doctor of Philosophy
In the modern day, all wireless communication signals use electromagnetic waves that propagate through the atmosphere. In the upper atmosphere, there exists a region called the ionosphere, which consists of plasma (a mixture of ions, electrons, and neutral particles). Because ions and electrons are charged particles, they interact with the electromagnetic communication signals. A better understanding of ionospheric turbulence will allow for aid in forecasting space weather as well as improve future communication equipment. Communication signals become distorted as they pass through turbulent regions of the ionosphere, which negatively affects the signal quality at the receiving end. For a tangible example, when Global Positioning System (GPS) signals pass through turbulent regions of the ionosphere, the resulting position estimate becomes worse. This work looks at two specific causes of ionospheric turbulence: the gradient drift instability (GDI) and the Kelvin-Helmholtz instability (KHI). Under the correct background conditions, these instabilities have the ability to generate ionospheric turbulence. To learn more about the GDI and the KHI, a novel simulation model is developed. The model uses a method of splitting the equations such that the focus is on just the development of the turbulence while considering spatially constant realistic background conditions. The model is shown to accurately represent results from previously studied problems in the ionosphere. This model is applied to an ionospheric phenomenon known as subauroral polarization streams (SAPS) to study the development of the GDI and the KHI. SAPS are regions of the ionosphere with large westward velocity that changes with latitude. The shape of the latitudinal velocity profile depends on many other factors in the ionosphere such as the geomagnetic conditions. It is found that for certain profiles, the GDI will form in SAPS with some of these examples matching observational data. At higher altitudes, the model predicts that the KHI will form instead. While the model is applied to just the development of the GDI and the KHI in this work, it is written in a general manner such that other causes of ionospheric turbulence can be easily studied in the future.
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Omiciuolo, Manolo [Verfasser]. "Generic Purpose Modelling and Domain Specific Simulation: a Framework for Conceptual Design of Space Mechanisms / Manolo Omiciuolo." München : Verlag Dr. Hut, 2018. http://d-nb.info/1164293680/34.
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Callaghan, Eleanor. "Attentional refocusing between time and space in older adults : investigation of neural mechanisms and relation to driving." Thesis, Aston University, 2018. http://publications.aston.ac.uk/37530/.
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Older adults have a disproportionately high risk of causing collisions at intersections and causing collisions by failing to notice surrounding road signs or signals. Collisions caused by older drivers seem to result from attentional failures. There is limited research exploring the ability to refocus from orienting attention to events changing in time (i.e. temporal attention) to distributing attention spatially (i.e. spatial attention), a process that is particularly important while driving and, if impaired,could cause collisions. The aims of the project were firstly to assess whether the ability to refocus attention from time to space changes throughout the adult lifespan when assessed with a computer based task and in an ecologically valid scenario during simulated driving, secondly, to use magnetoencephalography (MEG) to identify changes to neural mechanism that might explain difficulties in attentional refocusing, and finally, use mobile electroencephalography to explore the neural mechanisms involved in attentional refocusing while driving. Results demonstrated age related declines in the ability to refocus attention from time to space both in a computer-based task and during simulated driving. MEG recorded in a computer-based attention refocusing task revealed that, compared to younger adults, older and middle-aged adults displayed task-related theta deficits in lower level visual processing areas, and instead, displayed compensatory increases in theta power and phase-related connectivity across frontal regions. Increased frontal lobe recruitment likely reflects enhanced top-down attention to cope with impaired lower level attention mechanisms,supporting compensatory recruitment models of ageing. During simulated driving, older participants displayed slower driving speeds and weaker beta desynchronization in preparation to read a road sign, instead displaying a stronger theta power increase in response to the road sign, further demonstrating neural and behavioural compensatory strategies that are only partially successful. Findings warrant the development of a training programme to improve attentional refocusing between time and space while driving.
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Warwick, Elanor Joan Petra. "Defensible space as a mobile concept : the role of transfer mechanisms and evidence in housing research, policy and practice." Thesis, King's College London (University of London), 2015. http://kclpure.kcl.ac.uk/portal/en/theses/defensible-space-as-a-mobile-concept(78c8a507-a372-4ad0-8450-7aef9c47ba7a).html.
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Defensible space is a contested yet influential approach to designing-out-crime on social housing estates. This thesis uses defensible space as the vehicle to explore how movement changes concepts; to extend the learning on policy mobility mechanisms; to investigate the varied cross-disciplinary nature of evidence use; and to explore the interaction of policy, the housing sector and the state. Deepening the international policy mobilities narrative, the study traces the dispersal/embedding of the concept in Britain since the 1980s by revisiting the operational and theoretical account of defensible space proposed by Alice Coleman in the Design Improvement Controlled Experiment (DICE). Drawing on interviews with planning and architecture practitioners, housing managers and elite policymakers, the thesis explores the multiple ways the concept was interpreted and implemented as it circulated from national to local level and within three London housing estates, illustrating how the transfer mechanisms worked at both a policy and practical level. Despite being a concept whose principles continue to underpin design guidance (such as Secured by Design), defensible space failed to coalesce into a single formal policy, remaining a cluster of associated disputed elements. How these conceptual elements aided or hindered transfer and take up is noted by tracking routes to acceptance, the roles of formal transfer mechanisms, informal information sharing by transfer agents traversing networks, or practitionersʼ local contextualization of generic guidance. The research demonstrates the ongoing resilience and acceptance of defensible space, despite biased evaluation, the mismatch of DICE to the politics of the time and the uncertain nature of the concept. By questioning whether positivist scientific theoretical unity is achievable in practice, it argues for greater trust in practitioner experience, and proposes a looser middle-range approach to theory building for ambiguous concepts such as defensible space.
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Akalin, Gokcan. "Simulation Of Biped Locomotion Of Humanoid Robots In 3d Space." Master's thesis, METU, 2010. http://etd.lib.metu.edu.tr/upload/12612470/index.pdf.
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The main goal of this thesis is to simulate the response of a humanoid robot using a specified control algorithm which can achieve a sustainable biped locomotion with 4 basic locomotion phases. Basic parts for the body of the humanoid robot model are shaped according to the specified basic physical parameters and assumed kinematic model.
The kinematic model, which does not change according to locomotion phases and consists of 27 segments including 14 virtual segments, provides a humanoid robot model with 26 degrees of freedom (DOF). Corresponding kinematic relations for the robot model are obtained by recursive formulations. Derivation of dynamic equations is carried out by the Newton-Euler formulation. A trajectory definition algorithm which defines positions, orientations, translational and angular velocities for the hip and its mass center, toe part of the foot and its toe point is created. A control strategy based on predictive optimum command acceleration calculations and computed torque control method is implemented.
The simulation is executed in Simulink and the visualization of the simulation is established in a virtual environment by Virtual Reality Toolbox of MATLAB. The simulation results and the user defined reference input are displayed simultaneously in the virtual environment.
In this study, a simulation environment for the biped locomotion of humanoid robots is created. By the help of this thesis, the user can test various control strategies by modifying the modular structure of the simulation and acquire necessary information for the preliminary design study of a humanoid robot construction.
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Sankeralli, Marcel John. "Investigation of the chromatic postreceptoral detection mechanisms of human colour vision using noise masking in cone contrast space." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape11/PQDD_0020/NQ44571.pdf.
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Pehrson, Nathan Alan. "Developing Origami-Based Approaches to Realize Novel Architectures and Behaviors for Deployable Space Arrays." BYU ScholarsArchive, 2019. https://scholarsarchive.byu.edu/etd/7762.
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Origami-based approaches for the folding of thick materials for specific application to large deployable space arrays is explored in this work. The folding approaches presented utilize strain energy, spatial kinematics, membranes, compliant mechanisms, and or in combination together to fold finite-thickness materials viewed through the lens of origami-based engineering. Novel architectures and behaviors of mechanisms are developed to achieve packaging efficiency, deployment, and self-stiffening. A method for the folding of monolithic thick-sheet materials is developed by incorporating compliant mechanisms into the material itself to strategically add degrees of freedom. The design and characterization of the compliant mechanisms with consideration to stress, material selection, and stiffness is given. Other folding approaches developed include a bistable vertex and a double-membrane method.The folding approaches derived are applied to larger tessellations and folding patterns. The fold patterns developed and used lend themselves well to large reconfiguration and the combination of the folding approaches with the patterns create opportunities to fabricate products out of thick, functional materials. Of specific interest is the application of these approaches and patterns to the field of deployable space arrays. Spatial kinematics, computational dynamics, physical tests, and systems engineering are used to develop an array architecture that is self-deployable, self-stiffening, and retractable. This architecture is shown to open the design space of large deployable arrays by increasing packaging efficiency and mass.The method, approaches, and architectures developed by this dissertation contribute to the fields origami-based engineering and deployable space arrays. While a focus of this work is the advancement of space technologies, the depth of the analyses provided are transferable to other origami-based and compliant-mechanism disciplines.
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Kang, Yuhong. "Mechanisms, Conditions and Applications of Filament Formation and Rupture in Resistive Memories." Diss., Virginia Tech, 2015. http://hdl.handle.net/10919/77593.
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Resistive random access memory (RRAM), based on a two-terminal resistive switching device with a switching element sandwiched between two electrodes, has been an attractive candidate to replace flash memory owing to its simple structure, excellent scaling potential, low power consumption, high switching speed, and good retention and endurance properties. However, due to the current limited understanding of the device mechanism, RRAMs research are still facing several issues and challenges including instability of operation parameters, the relatively high reset current, the limited retention and the unsatisfactory endurance.
In this study, we investigated the switching mechanisms, conditions and applications of oxygen vacancy (Vo) filament formation in resistive memories. By studying the behavior of conductive Vo nanofilaments in several metal/oxide/metal resistive devices of various thicknesses of oxides, a resulting model supported by the data postulates that there are two distinct modes of creating oxygen vacancies: i) a conventional bulk mode creation, and ii) surface mode of creating oxygen vacancies at the active metal-dielectric interface. A further investigation of conduction mechanism for the Vo CF only based memories is conducted through insertion of a thin layer of titanium into a Pt/ Ta2O5/Pt structure to form a Pt/Ti/ Ta2O5/Pt device. A space charge limited (SCL) conduction model is used to explain the experimental data regarding SET process at low voltage ranges. The evidence for existence of composite copper/oxygen vacancy nanofilaments is presented. The innovative use of hybrid Vo/Cu nanofilament will potentially overcome high forming voltage and gas accumulation issues. A resistive floating electrode device (RFED) is designed to allow the generation of current/voltage pulses that can be controlled by three independent technology parameters. Our recent research has demonstrated that in a Cu/TaOx/Pt resistive device multiple Cu conductive nanofilaments can be formed and ruptured successively. Near the end of the study, quantized and partial quantized conductance is observed at room temperature in metal-insulator-metal structures with graphene submicron-sized nanoplatelets embedded in a 3-hexylthiophene (P3HT) polymer layer. As an organic memory, the device exhibits reliable memory operation with an ON/OFF ratio of more than 10.Ph. D.
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Svidró, Péter. "Study of solidification and volume change in lamellar cast iron with respect to defect formation mechanisms." Licentiate thesis, KTH, Tillämpad processmetallurgi, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-136985.
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Lamellar cast iron is a very important technical alloy and the most used material in the casting production, and especially in the automotive industry which is the major consumer. Beside the many great properties, it is inclined to form casting defects of which some can be prevented, and some may be repaired subsequently. Shrinkage porosity is a randomly returning problem, which is difficult to understand and to avoid. This defect is a volumetric deficiency which appear as cavities inside the casting in connection to the casting surface. Another frequent defect is the metal expansion penetration. This defect is a material surplus squeezed to the casting surface containing sand inclusion from the mold material. Shrinkage porosity is usually mentioned together with metal expansion penetration as the formation mechanism of both defects have common roots. It is also generally agreed, that these type of defects are related to the volumetric changes occurring during solidification. Additionally, the formation of these defects are in connection with the coherency of the primary austenite dendrites. The purpose of this work was to develop knowledge on factors affecting a volume-change related casting defect formation in order to minimize the presence of these defects in engine component production. This was done by extending the existing solidification investigation methods with novel solutions. Introduction of expansion force measurement in the determination of dendrite coherency combined with multi axial volume change measurement refine the interpretation of the solidification. Comparison of registered axial and radial linear deformation in cylindrical samples indicated an anisotropic volume change. Different methods for dendrite coherency determination have been compared. It was shown that the coherency develops over an interval. Dependent on the added inoculant the coherency is reached at different levels of fractions of a solidified primary phase. It is also shown, that inoculation has an effect on the nucleation and growth of the primary phase. Quantitative image analysis has been performed on the primary phase in special designed samples designed to provoke shrinkage porosity and metal expansion penetration. It was found, that the inter-dendritic space varies within a casting. This was explained by the coarsening of the primary dendrites which originates from differences in the local time of solidification.QC 20131210
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Arvidsson, Viktor. "Coordination from an Awareness perspective : Mechanisms and techniques for Awareness based Coordination support." Thesis, Umeå University, Department of Informatics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-25364.
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When a task becomes shared the need for coordination arises. One fundamental factor for coordination is awareness. This study aimed to answer the question of how awareness-based coordination support systems could increase the efficiency in the processing of tasks generated by the Customer Support Unit in Skellefteå municipality, ultimately creating a better work situation for the officers responsible for the handling of tasks and increasing the service level for the customers of their services. This question was answered by conducting interviews, observing system usage and through analysis of pre-existing interviews from earlier studies of the municipality’s CSU project. This study shows that there are aspects in the task management that are in need of coordination support and presents a task classification system based on the logistic nature of the task. Furthermore this paper identifies the main problems related to the current task management and from an awareness perspective discusses and outlines various mechanisms and techniques to address these problems. Alongside these problems the general lack of coordination support in the current Document and Workflow System (FlexiteBPMS) is approached. Furthermore all outlined proposals share the common aspiration of lessening the burden for the officers without simply shifting the workload onto other units in the workflow chain.
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Dunroy, Helen Mary Agnes. "CO2 retention in respiratory disease : Investigations into potential pre-existing mechanisms in healthy yang subjects using added external dead-space." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.497523.
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Scharlemann, Carsten A. "Investigation of thrust mechanisms in a water fed pulsed plasma thruster." The Ohio State University, 2003. http://rave.ohiolink.edu/etdc/view?acc_num=osu1070354149.
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Monti, Enrico. "Repetitive and adaptive feedforward schemes for high performance control of automatic machines mechanisms." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019.
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In this thesis different high performance controls of non-linear mechanisms are presented and evaluated. The key idea of the proposed schemes consists in modifying the periodic reference trajectory provided to the plant in order to reduce as much as possible the tracking error by compensating unmodelled dynamics and periodic disturbances that cyclically affect it. Starting from the study of the standard Repetitive Control structure, the purpose was to design a new and more flexible control algorithm that could avoid the several problems presented by the standard RC technique. According to this aim two modified versions of the repetitive control and an adaptive feedforward approach are developed and their simulation results are discussed. Moreover, this work was done in collaboration with the Line Control & Technology office of the G.D S.p.A. company and the experimental results obtained with an industrial setup composed by a Beckhoff PLC, a Bosch drive and Kollmorgen motor, are reported only for the adaptive feedforward approach, showing the real effectiveness of the proposed method.
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Williams, Robert Earl Jr. "Simulation and Characterization of Cathode Reactions in Solid Oxide Fuel Cells." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16309.
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In this study, we have developed a dense La0.85Sr0.15MnO3-δ (LSM) Ce0.9Gd0.1O1.95 (GDC) composite electrode system for studying the surface modification of cathodes. The LSM and GDC grains in the composite were well defined and distinguished using energy dispersive x-ray (EDX) analysis. The specific three-phase boundary (TPB) length per unit electrode surface area was systematically controlled by adjusting the LSM to GDC volume ratio of the composite from 40% up to 70%. The TPB length for each tested sample was determined through stereological techniques and used to correlate the cell performance and degradation with the specific TPB length per unit surface area.
An overlapping spheres percolation model was developed to estimate the activity of the TPB lines on the surface of the dense composite electrodes developed. The model suggested that the majority of the TPB lines would be active and the length of those lines maximized if the volume percent of the electrolyte material was kept in the range of 47 57%. Additionally, other insights into the processing conditions to maximize the amount of active TPB length were garnered from both the stereology calculations and the percolation simulations.
Steady-state current voltage measurements as well as electrochemical impedance measurements on numerous samples under various environmental conditions were completed. The apparent activation energy for the reduction reaction was found to lie somewhere between 31 kJ/mol and 41 kJ/mol depending upon the experimental conditions. The exchange current density was found to vary with the partial pressure of oxygen differently over two separate regions. At relatively low partial pressures, i0 had an approximately dependence and at relatively high partial pressures, i0 had an approximately dependence. This led to the conclusion that a change in the rate limiting step occurs over this range.
A method for deriving the electrochemical properties from proposed reaction mechanisms was also presented. State-space modeling was used as it is a robust approach to addressing these particular types of problems due to its relative ease of implementation and ability to efficiently handle large systems of differential algebraic equations. This method combined theoretical development with experimental results obtained previously to predict the electrochemical performance data. The simulations agreed well the experimental data and allowed for testing of operating conditions not easily reproducible in the lab (e.g. precise control and differentiation of low oxygen partial pressures).
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Gupta, Viyas. "Analysis of single event radiation effects and fault mechanisms in SRAM, FRAM and NAND Flash : application to the MTCube nanosatellite project." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS087/document.
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L’environnement radiatif spatial est un environnement sévère qui agit sur tout composants électroniques embarqués sur des engins spatiaux, y compris sous le bouclier naturel que nous procure le champ magnétique terrestre en orbite basse. Bien qu’il soit possible, en particulier à ces orbites, de se protéger efficacement contre les particules créant de la dose totale ionisante, cela pose plus de difficultés pour les particules générant des effets singuliers. Cela est d’autant plus un problème que l’utilisation des composants commerciaux (dits « COTS »), non conçus pour de telles applications, sont de plus en plus utilisés. Dans le cadre de cette thèse, les effets singuliers sur trois types de mémoires sont étudiés: SRAM, FRAM et NAND Flash. En se basant sur l’analyse des résultats de tests, les mécanismes d’erreurs induits par des particules générant des effets singuliers sont analysés. Avec pour objectif d’étudier et comparer la sensibilité de ces mémoires directement en orbite, l’expérience RES (Radiation Effect Study) a été développée et est présentée dans ce manuscrit. Cette expérience scientifique constituera la charge utile du nanosatellite de type CubeSat nommé MTCube (Memory Test CubeSat) developpé à l’Université de Montpellier en collaboration entre le Centre Spatial Universitaire Montpellier-Nîmes, et les laboratoires LIRMM et IES. Ce nanosatellite est financé par l’ESA (Agence Spatial Européenne)Space radiation is a harsh environment affecting all electronic devices used on spacecraft, despite the presence of Earth’s protective magnetic field in Low Earth Orbit (LEO). Although particles inducing total ionizing dose (TID) can be effectively shielded against in LEO, particles responsible for Single Event Effects (SEEs) remain an issue for the reliability of electronics. This is particularly of concern considering the increasing use of Commercial-Off-The-Shelf (COTS) components, not designed for space applications. In the frame of this thesis, the SEE response of three commercial memory types are explored: SRAM, FRAM and NAND Flash. Based on SEE test results, the possible fault mechanisms induced by SEE particles on those devices are analysed. In order to study and compare the devices’ response with actual in-orbit measurements, the RES (Radiation Effect Study) science experiment was developed and is presented. The RES experiment will be the payload of the MTCube (Memory Test CubeSat) nanosatellite, which is being developed at the University of Montpellier as a joint project between the University Space Center (CSU Montpellier-Nîmes), as well as the LIRMM and IES laboratories. MTCube is financed by the European Space Agency (ESA)
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Logan, Philip James. "A Planar Pseudo-Rigid-Body Model for Cantilevers Experiencing Combined Endpoint Forces and Uniformly Distributed Loads Acting in Parallel." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5730.
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This dissertation describes the development and effectiveness of a mathematical model used to predict the behavior of cantilever beams whose loading conditions include parallel combinations of evenly distributed loads and endpoint forces. The large deflection of cantilever beams has been widely studied. A number of models and mathematical techniques have been utilized in predicting the endpoint path coordinates and load-deflection relationships of such beams. The Pseudo-Rigid-Body Model (PRBM) is one such method which replaces the elastic beam with rigid links of a parameterized pivot location and torsional spring stiffness. In this paper, the PRBM method is extended to include cases of a constant distributed load combined with a parallel endpoint force. The phase space of the governing differential equations is used to store information relevant to the characterization of the PRBM parameters. Correction factors are also given to decrease the error in the load-deflection relationship and extend the angular range of the model, thereby further aiding compliant mechanism design. The calculations suggest a simple way of representing the effective torque caused by a distributed load in a PRBM as a function of easily calculated model parameters.
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O'Grady, Rebecca Bridget. "Object-based, space-based and domain-based mechanisms of selection : an investigation of the Duncan (1984), Baylis and Driver (1993), and Egly and Homa (1984) paradigms." Thesis, Birkbeck (University of London), 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.267614.
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Daigo, Schulte Maria Joy [Verfasser], Rainer [Akademischer Betreuer] [Gutachter] Matyssek, Wolfram [Gutachter] Beyschlag, and Johannes [Gutachter] Schnyder. "Space- and resource-related decomposition of growth for understanding mechanisms of competitive success / Maria Joy Daigo Schulte. Betreuer: Rainer Matyssek. Gutachter: Wolfram Beyschlag ; Johannes Schnyder ; Rainer Matyssek." München : Universitätsbibliothek der TU München, 2016. http://d-nb.info/1107543444/34.
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Bonato, Michela [Verfasser], and Hans [Akademischer Betreuer] Gebhardt. "Spatialization of Happiness in Chongqing Watershed. A critical analysis of the mechanisms of urban space production in relation to the current local management of the waterscape / Michela Bonato ; Betreuer: Hans Gebhardt." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1241250820/34.
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Law, Po-lun. "Model-based variable-structure control of robot manipulators in joint space and in Cartesian space /." Hong Kong : University of Hong Kong, 1995. http://sunzi.lib.hku.hk/hkuto/record.jsp?B18973097.
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Thesis (M. Phil.)--University of Hong Kong, 1995.Cover title: Model-based variable-structure control of robot maniqulators in joint space and in Cartesian space. Includes bibliographical references (leaf 161-175).
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羅普倫 and Po-lun Law. "Model-based variable-structure control of robot manipulators in joint space and in Cartesian space." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1995. http://hub.hku.hk/bib/B31212463.
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Pan, Ya-Dung 1960. "Teleoperation of mechanical manipulators aboard the US space station." Thesis, The University of Arizona, 1987. http://hdl.handle.net/10150/276611.
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This study presents a new analytical controller design strategy for the teleoperation of mechanical manipulators aboard the U.S. space station. This controller design strategy emphasizes on the stability of a closed-loop control system involving time delay. Simplified dynamic equations of the Stanford arm are considered as the manipulator model. A local linearizing and decoupling control algorithm is applied to linearize and decouple the dynamic equations. Once the linear form of the manipulator is obtained, a model prediction control loop is constructed and implemented as a digital controller to provide the predictive states information, and a particular model reduction method is applied to yield a reduced-order digital controller. This reduced-order digital controller is a highly self-tuned controller which can control the closed-loop system with time delay by following a specified performance.
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Liu, Ming. "Multidimensional damage state identification using phase space warping /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3188065.
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Kabir, Saqib. "Designing of a solar panel deployment mechanism for small satellite." Master's thesis, Faculty of Engineering and the Built Environment, 2021. http://hdl.handle.net/11427/33822.
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In the last few years, there has been a considerable increase of low cost space mission. Almost every small satellite has appendages like Solar Panels OR Antennas. These appendages have large inertial forces with low structural rigidity and mass to size ratio. These appendages are in stowed position in launcher to accommodate the whole satellite in the Launcher. However after launching these appendages are deployed to obtain the required power and the pointing of antennas. Their power producing capability is directly related to their area of exposure to sun, that is why these panels are available in different sizes and configurations. The requirement for the deployment mechanism for these appendages need to be cost effective, compact, lighter in weight and simple. It is entirely dependent on the structural designer to create such a robust mechanism that conforms to the requirements of the mission. In order to deploy the solar panels, it is mandatory that some sort of actuating system is employed. In this regard, we are aiming to use the torsional spring to induce the required torque for the deployment. There has been a considerable amount of research work [1-4] for a robust deployment mechanism to deploy the solar panel reliably without compromising on the overall cost and strength of the system. To realize the practical utility of Torsion Springs [5] for solar panel deployment, with the deficiency of locking after deployment and hold down mechanism when stowed. We propose a simple actuation scheme of designing the mechanism using Spiral Torsional spring for small satellite with its Zero 'g' testing and mitigation of expected Risks.
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Misra, Anuj. "Towards a holographic description of pulsar glitch mechanism." Master's thesis, University of Cape Town, 2015. http://hdl.handle.net/11427/15589.
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This work aims to review the progress in understanding the underlining physics of pulsar glitches: beginning from the pedagogical development of the subject to eventually motivating the use of AdS/CFT techniques in studying a certain class of condensed matter systems. The foundation of this work is built upon the Gross Pitaevskii (GP) model of super-fluidity applied to the interior matter of neutron stars, where the condensate wave function acts as the order parameter of the macroscopic coherence theory. The excitation modes of the field equations are found to be solitonic vortices, which then go on to present a theoretical basis to the plausible theories of pulsar glitches involving vortex dynamics. The second major thrust of this thesis is in reviewing the application of AdS/CFT in study of strongly-coupled condensed matter systems, with special attention to the models of holographic superfluidity that admit vortex-like solutions. The basic identification of the characteristic free energy configuration of global vortices in the AdS/CFT prescription enables to motivate its use in studying the pulsar glitch mechanism. The last part of this work traces the conclusions of this review and attempts to present the current state-of-progress of the field with its extensive domain of purview and open lines of inquiry.
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Barlas, Fırat Alizade Rasim. "Design Of A Mars Rover Suspension Mechanism /." [S.l. : s.n.], 2004. http://library.iyte.edu.tr/tezler/master/makinamuh/T000341.pdf.
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Shafie, H. Khalil. "The geometry of Gaussian rotation space random fields /." Thesis, McGill University, 1998. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=35614.
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In recent years, very detailed images of the brain, produced by modern sensor technologies, have given the neuroscientist the opportunity to study the functional activation of the brain under different conditions. The main statistical problem is to locate the isolated regions of the brain where activation has occurred (the signal), and separate them from the rest of the brain where no activation can be detected (the noise). To do this the images are often spatially smoothed before analysis by convolution with a filter f (t) to enhance the signal to noise ratio, where t is a location vector in N dimensional space. The motivation for this comes from the Matched Filter Theorem of signal processing, which states that signal added to white noise is best detected by smoothing with a filter whose shape matches that of the signal. The problem is that the scale of the signal is usually unknown. It is natural to consider searching over filter scale as well as location, that is, to use a filter s-N/2ft/s with scale s varying over a predetermined interval [ s1,s2 ]. This adds an extra dimension to the search space, called scale space (see Poline and Mazoyer, 1994). Siegmund and Worsley (1995) establish the relation between searching over scale space with the problem of testing for a signal with unknown location and scale and find the approximate P-value of the maximum of the scale-space filtered image using the expected Euler characteristic of the excursion set. In this thesis we study the extension of the scale space result to rotating filters of the form | S|--1/4f (S --1/2t), where S is now an N x N positive definite symmetric matrix that rotates and scales the axes of the filter.
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Zambotti, Andrea. "Ground Testing and In-Flight Performance of a Space Mechanism." Doctoral thesis, Università degli studi di Trento, 2019. http://hdl.handle.net/11572/242871.
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LISA Pathfinder is a mission designed for testing the key technologies of the future LISA mission, whose goal is the detection of gravitational waves through the measurement of the relative motion of dedicated proof masses.
In LISA Pathfinder, a critical task is the release of two Test Masses (TMs); each TM has to be injected into free fall by a dedicated Grabbing Positioning and Release Mechanism (GPRM). Despite the symmetrical design of the GPRM, during the release, as an effect of asymmetric impulses exchanged by the TM and the release tips of the GPRM, the TM can acquire a residual momentum. The release is successful if the residual momentum of the TM can be compensated by the force authority of the capacity control, which allows to centre the TM in its housing; as a consequence, a residual momentum of the TM higher than a maximum requirement can be critical for the mission.
In the nominal release configuration, which assumes a monodimensional dynamics of the mechanism along the axis of the release tips, the residual momentum can be produced by the asymmetry of pushing forces (due to relative time delays between the two tips) or by two unbalanced adhesive pulls on the two sides. In particular, the low repeatability of the adhesive pulls suggests their characterization through a dedicated on-ground experimental campaign.
The characterization of the adhesive pulls exchanged by the TM and the GPRM has been the focus of the on-ground experimental campaigns performed by the University of Trento since the early 2000s. The Transferred Momentum Measurement Facility (TMMF) has been developed: a mock-up of the TM release, which allows a high measurability of the adhesive pulls and guarantees the representativeness of the experiment, has been tested in order to estimate the properties of the adhesive force at the contact between the two bodies. The estimated parameters, applied to a model of the in-flight release, allowed to predict that the effect of the asymmetric adhesive pulls applied by the GPRM to the TM should not be critical for the residual momentum.
In this thesis we report the completion of the research on the effect of adhesion in the TM release of LISA Pathfinder, by means of additional on-ground experimental campaigns, and by comparing the predictions with the actual behaviour of the GPRM in the releases performed during the early stages of the LISA Pathfinder mission (2016).
Prior to the launch of the mission, the on-ground TMMF facility has been modified in 2015 in order to host a copy of the GPRM, thus increasing the representativeness of the experiment w.r.t. the nominal release. The on-ground test campaign, consisting in several release tests, allowed to obtain a new (conservative) estimation of the effect of adhesion in the TM release of LISA Pathfinder.
The estimation of the adhesive effect, which yielded first a conservative prediction, has been then improved by investigating in detail the release dynamics of the TMMF. Thanks to a vibration mode-based model of the TMMF, the effect of the adhesive pull on the measured dynamics has been estimated with its uncertainty, thus yielding a more precise prediction for the in-flight case.
The launch of the LISA Pathfinder mission occurred on December 3, 2015, and prior to the beginning of the scientific operations the two TMs have been injected into free fall. Due to the criticalities observed in the releases, an additional in-flight release test campaign has been planned during the end-of-life activities (June 2017), by alternating several times grab and release of each TM. The in-flight release campaign yielded a statistical distribution of the residual momentum of the TM at the release, which we analysed in detail in order to characterize the actual in-flight GPRM performance. In particular, we focused on the deviation of the predictions (based on the assumption of nominal release) w.r.t. the in-flight observations, by looking for the motivations of the residual momentum measured in the in-flight case.
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Hu, Jun An 1968. "FE dynamic analysis of an umbrella frame for space applications." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=98969.
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Deformation will occur for the flexible structures undergoing large rigid-body motion such as the opening of an umbrella, which poses a problem falling into the category of dynamics of deformable bodies, an intersected area between structural dynamics and rigid-body dynamics. Based on the Euler-Bernoulli beam theory, an FE model is developed to simulate the process of deployment of an umbrella under a zero gravity circumstance in which the structural FEA is adopted to define the displacement field of beam elements. The position of an arbitrary point on a body is located by a set of generalized coordinates of the system, including rigid and elastic sets characterizing rigid-body motion and deformation for the components, respectively. After formulating the kinetic energy, potential energy and generalized forces of the system, the governing equations of motion with different holonomic constraint conditions corresponding to the stages of the deployment are then derived by invoking Lagrange's equations with multipliers. As for the validation of this model, a rigid FE model and a continuum rigid-body model are also derived. The numeric process reveals that significant periodic vibration is induced on the leaf at full deployment if an initial velocity is applied on the sleeve of the modeled umbrella and the deformation of the members causes the retard of the deployment. Comparison of the results shows good agreement between 3-element and 6-element models, and the deformable models are validated by the rigid-body ones. Although the formulation is based on the holonomic 2-body model, it is also applicable to a more complicated nonholonomic system.
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De, Luca Alexander. "Designing Usable and Secure Authentication Mechanisms for Public Spaces." Diss., lmu, 2011. http://nbn-resolving.de/urn:nbn:de:bvb:19-131551.
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