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Mackay, Paul. "Low energy quantum gravity." Thesis, University of Newcastle Upon Tyne, 2012. http://hdl.handle.net/10443/1752.
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This thesis investigates two very different aspects of quantum gravity. In the first - and main - section, we examine the question of quantum gravitational contributions to the running of a coupling parameter alongside the various problems and issues that this raises. We treat quantum gravity as an e ective eld theory and use perturbative methods to address issues. Speci cally, we look at a '4-type scalar coupling. In a gauge-invariant way, we consider a non-minimally coupled, massive scalar eld, with non-constant background, in the presence of a cosmological constant and contrary to most of the literature, we also calculate all derivative terms. An e ective action is constructed, renormalization counterterms calculated, and we nd that, within certain bounds, gravity leads to asymptotic freedom of scalar eld theory. Furthermore, we investigate whether considering quadratic divergences in gravitational calculations can tell us anything useful. In this case we nd non-vanishing quadratic divergences. However, we also recognise the possibility that quadratic divergences are somewhat of a red herring and that by suitable eld rede nitions, we can eliminate these from our calculations. The second section of the thesis addresses the possibility of super uidity in a quark gluon plasma. We use the framework of AdS/CFT, with knowledge of black hole thermodynamics, to consider the duality between a black hole in anti-de Sitter space and a uid existing on the boundary. Initially, we look at a simple case of a black hole possessing only mass and charge in AdS spacetime and calculate such properties as the entropy, temperature and speci c heat capacity, identifying a telltale sign of a phase change (speci c heat capacity tending to in nity) and of points of vanishing viscosity (corresponding with a zero entropy). After con rming that such a boundary exists, we take a di erent approach where we calculate and interpret the solutions to a relativistic Gross-Pitaevskii equation on a sphere. On projection back to R3, the solutions are seen to be tori, which we choose to interpret as vortex rings in analogy to the expected feature of those which are known to appear in a real super uids.
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Schmidt, Erin Stivers. "Electro-Drop Bouncing in Low-Gravity." PDXScholar, 2018. https://pdxscholar.library.pdx.edu/open_access_etds/4441.
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We investigate the dynamics of spontaneous jumps of water drops from electrically charged superhydrophobic dielectric substrates during a sudden step reduction in gravity level. In the brief free-fall environment of a drop tower, with a non-homogeneous external electric field arising due to dielectric surface charges (with surface potentials 0.4-1.8 kV), body forces acting on the jumped drops are primarily supplied by polarization stress and Coulombic attraction instead of gravity. This electric body force leads to a drop bouncing behavior similar to well-known phenomena in 1-g0, though occurring for much larger drops (~0.5 mL). We show a simple model for the phenomenon, its scaling, and asymptotic estimates for drop time of flight in two regimes: at short-times close to the substrate when drop inertia balances Coulombic force due to net free charge and image charges in the dielectric substrate and at long-times far from the substrate when drop inertia balances free charge Coulombic force and drag. The drop trajectories are controlled primarily by the dimensionless electrostatic Euler number Eu, which is a ratio of inertial to electrostatic forces. To experimentally determine values of Eu we conduct a series of drop tower experiments where we observe the effects of drop volume, net free charge, and static surface potential of the superhydrophobic substrate on drop trajectories. We use a direct search optimization to obtain a Maximum Likelihood Estimate for drop net charge, as we do not measure it directly in experiment. For φEu/8π > 1 drops escape the electric field, where φ is a drop to substrate aspect ratio. However, we do not observe any escapes in our dataset. With an eye towards engineering applications we consider the results in light of the so-called low-gravity phase separation problem with a worked example.
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Dando, Owen Robert. "Topological defects in low-energy string gravity." Thesis, Durham University, 1999. http://etheses.dur.ac.uk/4496/.
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Cosmologists are interested in topological defects as a possible source for the primordial density perturbations which seeded structure formation through gravitational instability. In this thesis, the gravitational properties of various topological defects are studied in the context of low-energy string theory, a likely modification of Einstein gravity at the high energy scales prevalent in the early universe. We consider in turn global monopole, local monopole, global cosmic string and global texture defects, allowing for an arbitrary coupling of defects to the string theory dilaton. For global defects we find the following behaviour. If the dilaton is massless, this modification to general relativity generically destroys the global good behaviour of the monopole and cosmic string, making their spacetimes singular. For the texture non-singular spacetimes exist, but only for certain values of the matter-dilaton coupling, dependent on the gravitational strength of the defect; in addition, this non-singular behaviour exists only in a certain frame. In the case of a massive dilaton, the metric behaviour of these defects is similar to that found in Einstein gravity, though we find they generically induce a long-range dilaton cloud. For the local monopole, which we study only in the presence of a massless dilaton, a rich variety of behaviour is found. For particular parameter values the local monopole spacetime approximates that of an extremal dilaton black hole.
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Tomi, Leena Maija. "Studies of otolith-spinal adaptation to altered gravity performed in man." Thesis, McGill University, 1986. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=65511.
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Korsakova, Natalia [Verfasser]. "Probing low gravity gradient with LISA pathfinder / Natalia Korsakova." Hannover : Technische Informationsbibliothek (TIB), 2016. http://d-nb.info/1118740912/34.
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Wichiencharoen, Chugiat. "Recovery of 1⁰-mean anomalies in a local region from a low-low satellite to satellite tracking mission /." The Ohio State University, 1985. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487262825074523.
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Veilleux, Douglas L. "Melting in a low gravity environment with applied electromagnetic fields /." View online ; access limited to URI, 2005. http://0-wwwlib.umi.com.helin.uri.edu/dissertations/dlnow/3186925.
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Bokhour, Edward Bijan. "Energy absorption methods for fluid quantity gauging in low gravity." Thesis, Massachusetts Institute of Technology, 1988. http://hdl.handle.net/1721.1/35942.
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Le, Nguyen Lan Phuong. "Effect of gravity on convective condensation at low mass velocity." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30280/document.
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Les écoulements diphasiques sont couramment utilisés dans de nombreux domaines dont, en particulier, le domaine spatial. La performance de ces systèmes est entièrement régie par les couplages se produisant entre les écoulements et les transferts de chaleur. Cette particularité a conduit, depuis les dernières décennies, au développement de nombreuses études sur les écoulements diphasiques en microgravité. Afin d'accroître la connaissance sur le comportement thermo-hydraulique de ces systèmes thermiques, la présente étude se focalise sur l'étude de la condensation dans un mini-tube en présence ou non de la force gravitationnelle. Pour étudier l'effet de la gravité sur cette configuration, un premier modèle instationnaire d'écoulement diphasique a été développé. Parallèlement, une analyse des effets de la gravité sur l'hydrodynamique et les transferts thermique a été menée dans deux sections d'essai possédant un diamètre interne commun de 3,4 mm et des vitesses massiques faibles à modérées. La première étude a été réalisée au cours de la 62e campagne de vols paraboliques de l'ESA. Elle a été dédiée à la détermination des coefficients de transfert de chaleur quasi-locaux se produisant à l'intérieur d'un tube de cuivre. Afin de visualiser également les régimes d'écoulement présents, un tube en verre a été inséré au sein de cet échangeur. L'effet de la gravité sur les écoulements et les transferts a ainsi été déterminé. La seconde expérience, menée au sol, a porté sur l'étude d'un écoulement de vapeur descendant au sein d'un tube en saphir placé verticalement. Un protocole de mesure permettant d'obtenir simultanément l'épaisseur du film de liquide ruisselant et le coefficient d'échange local associé a été développéLiquid-vapor two-phase flows have common applications in many fields including space thermal management systems. The performances of such systems are entirely associated to the coupling between thermal and hydrodynamic phenomena. Therefore, two-phase flows in microgravity condition have emerged as an active research area in the last decades. In order to complete the state of the art and to contribute to the increase in the knowledge of hydrothermal behavior of two-phase thermal management systems, the present study was conducted on convective condensation inside a mini tube, both in normal and micro gravity conditions. To analyze the effect of gravity on such flows, a preliminary transient modeling of the two-phase flow has been established. Simultaneously, an experimental investigation was carried out on the hydrodynamic and thermal behaviors of condensation flows in two test sections of 3.4 mm inner diameter at low and intermediate mass velocities. The first experiment was conducted during the 62nd ESA parabolic flights campaign. The test section was made with copper and allowed measurements of the quasi-local heat transfer coefficient. A glass tube was also inserted in the middle of the test section for the visualization of the two-phase flow regime. From this study, the changes in heat transfer coefficient and flow regime according to gravity variations were determined. The second experiment was carried out on ground in a sapphire tube installed vertically considering downward flow. The set-up was designed in order to measure simultaneously the local heat transfer coefficient and the thickness of the liquid film falling down along the tube wall
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Kaspi, Y., T. Guillot, E. Galanti, Y. Miguel, R. Helled, W. B. Hubbard, B. Militzer, et al. "The effect of differential rotation on Jupiter's low-degree even gravity moments." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/625195.
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The close-by orbits of the ongoing Juno mission allow measuring with unprecedented accuracy Jupiter's low-degree even gravity moments J(2), J(4), J(6), and J(8). These can be used to better determine Jupiter's internal density profile and constrain its core mass. Yet the largest unknown on these gravity moments comes from the effect of differential rotation, which gives a degree of freedom unaccounted for by internal structure models. Here considering a wide range of possible internal flow structures and dynamical considerations, we provide upper bounds to the effect of dynamics (differential rotation) on the low-degree gravity moments. In light of the recent Juno gravity measurements and their small uncertainties, this allows differentiating between the various models suggested for Jupiter's internal structure.
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Peterson, Lee DeWitt. "The nonlinear coupled dynamics of fluids and spacecraft in low gravity." Thesis, Massachusetts Institute of Technology, 1987. http://hdl.handle.net/1721.1/14648.
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MacKenzie, Ruaraidh A. "Gravity field recovery using two low satellites in different orbital planes." Thesis, Aston University, 1995. http://publications.aston.ac.uk/14314/.
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This study is concerned with gravity field recovery from low-low satellite to satellite range rate data. An improvement over a coplanar mission is predicted in the errors associated with certain parts of the geopotential by the separation of the orbital planes of the two satellites. Using Hill's equations an analytical scheme to model the range rate residuals is developed. It is flexible enough to model equally well the residuals between pairs of satellites in the same orbital plane or whose planes are separated in right ascension. The possible benefits of such an orientation to gravity field recovery from range rate data can therefore be analysed, and this is done by means of an extensive error analysis. The results of this analysis show that for an optimal planar mission improvements can be made by separating the satellites in right ascension. Gravity field recoveries are performed in order to verify and gauge the limitations of the analytical model, and to support the results of the error analysis. Finally the possible problem of the differential decay rates of two satellites due to the diurnal bulge are evaluated.
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Hodgart, M. S. "Gravity gradient and magnetorquing attitude control for low-cost low earth orbit satellites : the UOSAT experience." Thesis, University of Surrey, 1989. http://epubs.surrey.ac.uk/844220/.
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An important concern in spacecraft engineering is attitude determination control and stabilisation (ADCS) - the combination of applied mathematics, classical physics and modern technology which maintains the pointing direction of one or more axes of an Earth-orbiting satellite. This thesis is a detailed study of a particular type of ADCS which exploits the gravity-gradient effect, which is just the weak tendency for an appropriately shaped body to point naturally in preferred directions; reinforced by magnetorquing, which is the active interaction of the geomagnetic field with a switched current passing through coils in the spacecraft body. The advantages of this technology is that it is low-cost, non-consumable and has no moving parts - so constituting no limitation to the satellite's life. The thesis is a detailed study of this form of ADCS with specific application to low Earth polar-orbiting (LEO) satellites, for which it is particularly suitable. The work is also a study in attitude determination based solely on a 3-axis magneometer measurement of the geomagnetic field, which is in principle a simple way, in terms of technology, of determining the attitude of the spacecraft, and from this controlling the attitude, if mediated by an on-board computer implementing appropriate algorithms. The results are for the most part practically based on the author's involvement with two satellites over a six year period with the satellites UOSAT-1 and UOSAT-2, which were designed, built, and continue to be controlled from the University of Surrey. A practical innovation in 2-axis attitude control is described: the active 'delibration' by active damping of a gravity-gradient controlled LEO satellite in an attitude-stabilised state, using a threshold comparison algorithm. A new theory and algorithms are then developed for 3-axis attitude control, based on a complementary use of magnetorquing and gravity gradient. Subject to further development these could alter the general perception of the most effective way of controlling low Earth orbiting satellites.
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Chen, Yiqun. "Recovery of terrestrial water storage change from low-low satellite-to-satellite tracking." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1196098152.
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Matson, Gary Paul. "Low Reynolds number, gravity currents : Newtonian exchange and viscoplastic dam break flows." Thesis, University of Bristol, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437303.
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Rye, Maria del Carmen. "Dynamics and Control of a Tensegrity System in Low-Earth Orbit." Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/77584.
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Tensegrity is the name given to a system of interconnected bars and tendons that can form a flexible self-standing structure. Its flexibility is due to the ability of the bars to move near-independent to each other, movement that can be caused by controlled tension forces in the tendons or external forces such as gravity. However, a balance of sorts must be maintained - if a tendon were to go slack, the entire structure could become unstable and collapse on itself.
This thesis looks at placing a tensegrity structure in orbit around the Earth. As a spacecraft's orbit is moved further away from the Earth, the strength of the Earth's gravity field lessens. Ideally, such a flexible structure would be placed far enough away from the Earth so that the gravity field would have too weak an impact on its individual elements to cause major distortions. However, the author recognizes that altitudes below 2,000 km, where the Earth's gravity field is still very prevalent, are the most common altitudes used by orbiting spacecraft today. The goal of this thesis is to analyze the distortions of the tensegrity structure at these lower altitudes, and also look at methods for controlling these distortions.Ph. D.
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Pritchard, David Thomas. "Some problems in two-phase flow : intertidal mudflats and low Reynolds number gravity currents." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.391189.
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Cannella, Giuseppe. "Design and analysis of a gravity balanced low-cost hybrid arm support for stroke rehabilitation." Thesis, University of Southampton, 2015. https://eprints.soton.ac.uk/393558/.
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Worldwide 12.6 million people live with moderate to severe disability following a stroke, and the number is increasing. Associated personal and societal care costs strongly motivate the development of effective low-cost technology for upper limb stroke rehabilitation. In order to be therapeutically effective, rehabilitation devices must assist repeated performance of a range of functional tasks whilst promoting voluntary effort, thereby enabling motor re-learning. This specification encourages subjects to use their residual muscle strength to perform rehabilitation tasks, hence exploiting the neuroplasticity of the brain, which plays a key role for the relearning of motion skills in impaired subjects. An approach to provide therapy is using mechanical systems. However, non-conventional rehabilitation devices currently lack automatic adaptive mechanisms within low-cost designs. Hence improvements are needed, which should incorporate the assistance around individual joints that is provided by robotic exoskeletal designs and the lowcost design features of non-powered orthoses. Another affordable technology is Functional Electrical Stimulation (FES), which helps patients perform rehabilitation tasks by stimulating specific muscles through electrical pulses. Whilst FES has been shown to be clinically effective, it must ideally be combined with a support device in order to provide support to all relevant joints. Combining the advantages of both mechanical and FES based modalities within a single affordable device would optimize the effectiveness of the rehabilitation therapy. Hence, in this thesis an innovative assistive device has been developed for upper limb stroke rehabilitation. It comprises a low-cost passive adaptive arm support that combines with FES under a hybrid control scheme. The innovative design of the orthosis is based on the gravity balancing theory which allows the design of mechanical systems within an intrinsically affordable solution. A 3D CAD model has been designed and structural analyses have been performed in order to assess its suitability to interact with impaired subjects. The implementation of the automatic adjustable system is explained in detail. The dynamic model of the orthosis, which plays a key role in the design of the controller, have been derived and the gravity balancing behaviour under dynamic effects have been tested in order to demonstrate its suitability for upper limb stroke rehabilitation. Then the general design framework to combine both FES and orthosis under a hybrid control scheme have been developed and specific cases have been simulated in order to assess its functionality and feasibility. The novelty of the device presented and analysed in this PhD thesis is based on the design of a new rehabilitation system which combines the advantages of more expensive robotic systems with those of non-powered orthoses. This device is the first in the field of non-conventional rehabilitation to combine a passive orthosis with FES under a hybrid control scheme, within a low-cost design in which the ease of use for end-users has been taken into account. Moreover, the rehabilitation system designed and analysed in this thesis represents a substantial foundation for further development, combining different areas of engineering and health science, such as: robotics, mechanical design, control systems and physiotherapy.
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Cornuelle, Christopher Steven. "The detection of low-degree solar gravity mode oscillations by differential radius observations, 1986-1987." Diss., The University of Arizona, 1992. http://hdl.handle.net/10150/186017.
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Solar oscillations are observed by examination of time-varying properties of the photosphere. Over 800 hours of solar limb intensity profile observations in the equatorial region were collected during 1986 and 1987 at the SCLERA Mt. Bigelow site and an analysis using the FFTD was performed in an effort to detect low-degree g-mode oscillation signals in the solar photosphere. Fourier analysis of the data yielded power spectra whose peak frequencies and overall power were tested for the presence of g-mode signals at 245 classified low-degree g-mode eigenfrequencies of Hill and Gu (1990). Significant results arose from comparison of the detected eigenmode power in the 1979 data to the power density at those same classified eigenfrequencies in spectra from 1986-87 data. Also, significant correlation was found between the earlier and later mode power distributions using several different methods. Use of the parameter D(i,j) to characterize the horizontal spatial behavior of eigenfunctions yielded significant results consistent with its known solar properties. Also, the observed relative signal power densities at those classified eigenfrequencies were found to be consistent with the theoretical development of Berthomieu and Provost (1990), and with previous SCLERA observations. It was noted that overall detected oscillation amplitudes in the photosphere are on average 4.0 $\times$ 0.6 times those observed in 1979, and the signal-to-noise ratio is substantially worse. The effects of instrumental defects, solar active regions, and terrestrial atmospheric noise were found to be minimal. Substantial agreement with the results of analysis of 1979 SCLERA data provides strong evidence of the correctness of the low-order g-mode classifications. The increase in g-mode signal power implied by these data, together with the other results, suggests that the photospheric behavior of these modes is variable, and perhaps solar-cycle dependent.
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Bong, Kui-fhui. "Housing provision : a study of housing problems of "cage man" /." Hong Kong : University of Hong Kong, 2000. http://sunzi.lib.hku.hk/hkuto/record.jsp?B2236027X.
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Foster, Michael Robert Pearlman Howard. "Low-temperature reactions and cool flames in an unstirred, static reactor at terrestrial and reduced-gravity /." Philadelphia, Pa. : Drexel University, 2007. http://hdl.handle.net/1860/1898.
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Wohlwend, Christian Stephen. "Modeling the Electrodynamics of the Low-Latitude Ionosphere." DigitalCommons@USU, 2008. https://digitalcommons.usu.edu/etd/11.
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The electrodynamics of the Earth's low-latitude ionosphere is dependent on the ionospheric conductivity and the thermospheric neutral density, temperature, and winds present. This two-part study focused on the gravity wave seeding mechanism of equatorial plasma depletions in the ionosphere and the associated equatorial spread F, as well as the differences between a two-dimensional flux tube integrated electrodynamics model and a three-dimensional model for the same time period. The gravity wave seeding study was based on a parameterization of a gravity wave perturbation using a background empirical thermosphere and a physics-based ionosphere for the case of 12 UT on 26 September 2002. The electrodynamics study utilized a two-dimensional flux tube integrated model in center dipole coordinates, which is derived in this work. This case study examined the relative influence of the zonal wind, meridional wind, vertical wind, temperature, and density perturbations of the gravity wave. It further looked at the angle of the wave front to the field line flux tube, the most influential height of the perturbation, and the difference between planar and thunderstorm source gravity waves with cylindrical symmetry. The results indicate that, of the five perturbation components studied, the zonal wind is the most important mechanism to seed the Rayleigh-Taylor instability needed to develop plasma plumes. It also shows that the bottomside of the F-region is the most important region to perturb, but a substantial E-region influence is also seen. Furthermore, a wave front with a small angle from the field line is necessary, but the shape of the wave front is not critical in the gravity wave is well developed before nightfall. Preliminary results from the three-dimensional model indicate that the equipotential field line assumption of the two-dimensional model is not valid below 100 km and possibly higher. Future work with this model should attempt to examine more of the differences with the two-dimensional model in the electric fields and currents produced as well as with the plasma drifts that lead to plume development.
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Alrasheedi, Mohammad H. "A low-cost man-portable free-space optics communication device for ethernet applications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2005. http://library.nps.navy.mil/uhtbin/hyperion/05Dec%5FAlrasheedi.pdf.
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Ferry, Todd W. "The NPS Small Robotic Technology Initiative, man-portable robots for low intensity conflict." Thesis, Monterey, California : Naval Postgraduate School, 2001. http://hdl.handle.net/10945/34057.
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The Naval Postgraduate School's Small Robotic Technology (SMART) Initiative is an ongoing research effort within the Combat Systems Science and Technology Curriculum that engages in forward-looking applications of small robotic technology for military employment. The immediate goal of which is to develop a multipurpose robotic platform that is capable of hosting varied sensor packages for military research. This thesis successfully accomplished initial background research and integration of a low cost, lightweight, all-terrain, robotic vehicle to fulfill this requirement. The areas of robotic investigation included: research and procurement of a Foster Miller Lemming tracked vehicle; the selection of a robust, network enabled, real-time microcontroller called the ipEngine; selection of Differential GPS as a highly accurate autonomous vehicle positioning technique; and the development of the ipEngine software environment for integration and testing of the microcontroller's wireless interfacing. Wireless communication tests using TCP/IP sockets, serial communication, telnet and a common Internet Web Browser validated the ability to remotely 6perate the vehicle under both direct and autonomous rtontrol. Ultimately, this thesis laid the foundation for follow-on NPS students to research and integrate varied robotic sensing techniques, including synthetic array seismic sonar's and chemical detection devices, and to participate in cooperative research with other military laboratories.
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Perera, Janaka P. "A low-cost man-portable free-space optics communication device for Ethernet applications." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Dec%5FPerera.pdf.
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Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, December 2004.Thesis advisor(s): Gamani Karunasiri, Xiaoping Yun. Includes bibliographical references (p. 47-50). Also available online.
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Farrokhpanah, Sonia. "Design of heat integrated low temperature distillation systems." Thesis, University of Manchester, 2009. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:228854.
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This work addresses the challenges in design of heat integrated low-temperature separation processes. A novel, systematic and robust methodology is developed, which contributes to the design practice of heat-integrated separation sequence and the refrigeration system in the context of low-temperature separation processes. Moreover, the methodology exploits the interactions between the separation and refrigeration systems systematically in an integrated design context. The synthesis and optimisation of heat-integrated separation processes is complex due to the large number of design options. In this thesis, task representation is applied to the separation system to accommodate both simple and complex distillation columns. The stream conditioning processes are simulated and their associated costs are included in the overall cost of the process. Important design variables in separation systems, such as the separation sequence, type and operating conditions of the separation units (e.g. the operating pressure, feed quality and condenser type) are optimised. Various refrigeration provision strategies, such as expansion of a process stream, pure and mixed multistage refrigeration systems and cascades of multistage refrigeration cycles, are considered in the present work. A novel approach based on refrigeration system database is proposed, which overcomes the complexities and challenges of synthesis and optimisation of refrigeration systems in the context of low-temperature separation processes. The methodology optimises the key design variables in the refrigeration system, including the refrigerant composition, the number of compression stages, the refrigeration and rejection temperature levels, cascading strategy and the partition temperature in multistage cascaded refrigeration systems. The present approach has selected a matrix based approach for assessing the heat integration potentials of separation and refrigeration systems in the screening procedure. Non-isothermal streams are not considered isothermal and stream splitting and heat exchangers in series are taken into account. Moreover, heat integration of reboiler and condenser of a distillation column through an open loop heat pump system can be considered in this work. This work combines an enhanced simulated annealing algorithm with MILP optimisation method and develops a framework for simultaneously optimising different degrees of freedom in the heat integrated separation and refrigeration processes. Case studies extend the approach to the design of heat integrated separation sequences in above ambient temperature processes. The robustness of the developed framework is further demonstrated when it is utilised to design the LNG and ethylene plant fractionation trains.
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Vakili-Amini, Babak. "A Mixed-Signal Low-Noise Sigma-Delta Interface IC for Integrated Sub-Micro-Gravity Capacitive SOI Accelerometers." Diss., Georgia Institute of Technology, 2006. http://hdl.handle.net/1853/10437.
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This dissertation presents the design and development of a mixed-signal low noise second-order integrated circuit (IC) for the open-loop and closed-loop operation of integrated capacitive micro- and nano-gravity accelerometers. The micromechanical accelerometers are fabricated in thick (less than 100 m) silicon-on-insulator (SOI) substrates. The IC provides the 1-bit digital output stream and has the versatility of interfacing sensors with different sensitivities while maintaining minimum power consumption (less than 5 mW) and maximum dynamic range (90 dB). A fully-differential sampled-data scheme is deployed with the ability of low-frequency noise reduction through the use of correlated double sampling (CDS) scheme. In this work, the measured resolution of the closed-loop CMOS-SOI accelerometer system, in the presence of high background accelerations, is in the micro-g (g: gravity) range. In this design, a second-order SC modulator is cascaded with the accelerometer and the front-end amplifier. The accelerometer operates in air and is designed for non-peaking response with a BW-3dB of 500 Hz. A 22 dB improvement in noise and hence dynamic range is achieved with a sampling clock of 40 kHz corresponding to a low oversampling ratio (OSR) of 40. The interface IC consumed a current of 1.5 mA from a supply of 3 V.
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Gala, Kaci Jo. "Design of a new narrow channel apparatus that simulates low gravity conditions for producing near limit flames." Diss., Connect to online resource - MSU authorized users, 2007.
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Schultz, Karl Ulrich. "Etiology of perceived strength changes in the muscles of the legs following locomotion under simulated low gravity." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/49946.
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Carroll, D. "The recovery of very low amplitude cardiac potentials from the chest surface in man." Thesis, University of Sussex, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.373144.
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Ciobanescu, Husanu Irina N. Choi Mun Young Ruff Gary A. "Droplet interactions during combustion of unsupported droplet clusters in microgravity : numerical study of droplet interactions at low reynolds number /." Philadelphia, Pa. : Drexel University, 2005. http://dspace.library.drexel.edu/handle/1860/729.
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Malloy, Michael G. "Spacecraft Trajectory Optimization Suite (STOpS): Design and Optimization of Multiple Gravity-Assist Low-Thrust (MGALT) Trajectories Using Modern Optimization Techniques." DigitalCommons@CalPoly, 2020. https://digitalcommons.calpoly.edu/theses/2247.
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The information presented in the thesis is a continuation of the Spacecraft Trajectory Optimization Suite (STOpS). This suite was originally designed and developed by Timothy Fitzgerald and further developed by Shane Sheehan, both graduate students at California Polytechnic State University, San Luis Obispo. Spacecraft utilizing low-thrust transfers are becoming more and more common due to their efficiency on interplanetary trajectories, and as such, finding the most optimal trajectory between two planets is something of interest. The version of STOpS presented in this thesis uses Multiple Gravity-Assist Low-Thrust (MGALT) trajectories paired with the island model paradigm to accomplish this goal. The island model utilizes four different global search algorithms: a Genetic Algorithm, Differential Evolution, Particle Swarm Optimization, and Monotonic Basin Hopping. The first three algorithms were featured in the initial version of STOpS written by Fitzgerald [1], and were subsequently modified by Sheehan [2] to work with a low-thrust adaptation of STOpS. For this work, Monotonic Basin Hopping was added to aid the suite with the MGALT trajectory search.
Monotonic Basin Hopping was successfully validated against four different test functions which had been used to validate the other three algorithms. The purpose of this validation was to ensure Monotonic Basin Hopping would work as intended, ensuring it would work in cooperation with the other three algorithms to produce a near optimal solution. After verifying the addition of Monotonic Basin Hopping, all four algorithms were used in the island model paradigm to verify MGALT STOpS’ ability to solve two known orbital transfer problem. The first verification case involved an Earth to Mars transfer with fixed thruster parameters and a predetermined time of flight. The second verification case involved a transfer from Earth to Jupiter via a Mars gravity assist; two different versions of the verification case were solved against trajectories produced by industry optimization software, the Satellite Tour Design Program Low-Thrust Gravity Assist and the Gravity Assisted Low-thrust Local Optimization Program. In the first verification case, MGALT STOpS successfully validated the Earth to Mars trajectory problem and found results agreeable to literature. In the second verification case, MGALT STOpS was partially successful in validating the Earth to Mars to Jupiter trajectory problems, and found results similar to literature. The final software produced for this work is a trajectory optimization suite implemented in MATLAB, which can solve interplanetary low-thrust trajectories with or without the inclusion of gravity assists.
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Phillips, Zachary Rockford. "Holocene Postglacial Fluvial Processes and Landforms in Low Relief Landscapes." Diss., North Dakota State University, 2020. https://hdl.handle.net/10365/32036.
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Postglacial rivers are part of the relatively young low-relief landscape system left behind by glaciers. Over time, postglacial rivers are susceptible to both minor and major channel planform changes as the Earth and its newly exposed rivers adjust to new isostatic and geomorphic equilibriums. Those planform changes result in topographic features that are well preserved among the largely unaltered landscape and offer opportunities to learn about the processes that create them. This work focuses on those minor and major planform changes and the resulting landforms, with a focus on processes effecting the glaciolacustrine Red River Valley. Here, three studies were conducted, two regarding minor planform changes and one focusing on major planform changes. Studies included in this work regard 1) the spatial distribution of meander cutoffs and meander cutoff relief on the Red River, 2), avulsion timing and length resulting from isostatic tilting and 3) mobile river ice and bank interaction frequency, locations, and erosion in meandering rivers. Results show that rivers develop meander cutoffs that faster in areas where geologic materials are more easily eroded and their relief shows a positive relationship with the rate of river incision. Major channel path changes (avulsions) in the presence of isostatic tilting were found to be most frequent soon after river establishment while rates of isostatic rebound are high enough to outpace channel incision. River ice was found to most frequently interact with the outer banks of channels with long, tight bends and high sinuosity, potentially contributing to the meandering process. From these results it can be interpreted that postglacial rivers were highly dynamic early in their history and have stabilized over time, with most of the changes occurring in areas with more erodible alluvium. Presently, rivers undergo most of their changes during the spring thaw when mobile river ice is impacting the banks, with sinuous river reaches impacted most frequently by mobile river ice.North Dakota Water Recourses Research Institute (ND WRRI) Fellowship Program
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Webster, Bruce Naakaii Ts'oh. "Low magnitude high frequency vibrations applied to the foot through the pedal of a human powered artificial gravity (HPAG) cycle." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/34165.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, February 2006."February 2006."
Includes bibliographical references (p. 87-88).
Astronauts are exposed to hazards unique to space travel. These hazards include radiation exposure and adaptation of the human body to the microgravity environment. For lunar and low earth orbital missions, the exposure period is typically less than six months and return to Earth is less than two weeks away. For travel beyond the Earth's moon, the microgravity exposure time will increase from months to years and return time will increase from weeks to months. Current countermeasures employ impact and high force loading to maintain bone health. An astronaut runs on a treadmill to impact load the weight bearing components of the musculoskeletal system. Elastic bands provide the "down" force for the astronaut while running. For high force loading, the astronaut performs a specified regimen of weight lifting exercises using resistive devices. The resistive devices provide a load in microgravity similar to that of free weights on Earth. These countermeasures have been beneficial in slowing bone adaptation, but have not stopped it. The imperceptible muscle contractions required for posture maintenance may be the absent load that the skeletal system requires to maintain bone health. Unlike the muscles that are required for impact and high force loading, the postural muscles work continuously to keep humans balanced and upright in a gravity environment.
(cont.) Jumping, running and even sitting require posture maintenance. Studies have shown that low magnitude loads applied at a high frequency to the weight bearing bones have not only maintained the bone mineral density, but also more importantly, maintained the structure of the bones. This thesis demonstrates the design of a vibrating pedal that delivers a perceptible, low magnitude load at a high frequency ([approx.]30 Hz) to the foot. This design required no external power and was implemented on a Human Powered Artificial Gravity (HPAG) cycle. A device similar to the vibrating pedal device created for this research could benefit society by providing an effective therapy against the disease of osteoporosis. A vibrating pedal could easily be mounted on a stationary cycle, possibly even standard bicycle, and provide a beneficial therapy to the user.
by Bruce Naakaii Ts'oh Webster.
S.M.
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Friedli, André. "Effects of acute, low-dose UVB radiation on the induction of contact hypersensitivity to diphenylcyclopropenon in man /." [S.l.] : [s.n.], 1993. http://www.ub.unibe.ch/content/bibliotheken_sammlungen/sondersammlungen/dissen_bestellformular/index_ger.html.
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Bong, Kui-fhui, and 黃貴慧. "Housing provision: a study of housing problems of "cage man"." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B31968521.
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Meunier, Arthur. "Asteroids deflection using state of the art European technologies." Thesis, KTH, Rymd- och plasmafysik, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-160713.
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In public opinion, protection against asteroids impact has always been on the agenda of space engineering. Actually it started from 1994 when Shoemaker Levy stroke Jupiter. This protection works in two steps: detection of threat and deflection. Some space agencies and foundations monitor the sky and set up scenario. Although the sky is nowadays well monitored and mapped, there is no global plan nowadays against this threat. This paper focuses on the deflection step, and aims at forecasting which variables are involved and their consequences on the deflection mission. In fact the result depends on several factors, like the time before hazardous moment, the accuracy of detection tools, the choice of deflection method, but the most unpredictable are human factors. This study shows a strategy and so tries to give some new response parts to the global deflection problem.
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Funcke, Lena [Verfasser], and Georgi [Akademischer Betreuer] Dvali. "How gravity shapes the low-energy frontier of particle physics : neutrino masses and the domestic axion / Lena Funcke ; Betreuer: Georgi Dvali." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2018. http://d-nb.info/1196008752/34.
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Cooper-Evans, Mia Samantha. "Where are the men? : low-income women's experience of heterosexual relationships." Thesis, Stellenbosch : Stellenbosch University, 2001. http://hdl.handle.net/10019.1/52611.
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Thesis (MA)--Stellenbosch University, 2001.ENGLISH ABSTRACT: The purpose of this paper was to review the available literature concerning how low-income women experience their heterosexual relationships. Particular attention was paid to the constructs of social support and intimacy which have both been cited as important variables for coping with stress. It was found that, despite there being more stressors associated with poverty, very little research has been conducted on lowincome women. However, when comparing the available literature, there seem to be important differences between low-income and middle-class women's expectations regarding heterosexual relationships. The literature suggests that for low-income women, heterosexual relationships can often be experienced as an additional source of stress, particularly as traditional gender roles playa greater role in expectations regarding the provision of social support. It therefore seems as though some low-income women, in a bid not to submit to traditional role expectations, choose to stay single and strive for financial independence in order to retain power within heterosexual relationships. The need for intimacy was not clearly articulated by low-income women but a desire for a sexually faithful partner was expressed. Although it seemed as though low-income women did not expect social support or intimacy from their male partners, they did articulate other specific expectations. The literature suggested that low-income women could reliably expect sex and the conception of children. from their heterosexual relationships but that their other expectations were often disappointed. However, heterosexual relationships are considered an important means for low-income women to gain status within the community. Finally, the current review of the literature highlighted the considerable overlap between the constructs of social support and intimacy. In conclusion, further research needs to be conducted (particularly in South Africa) in order to determine how low-income women experience their heterosexual relationships.
AFRIKAANSE OPSOMMING: Die doel van hierdie studie was om 'n oorsig te kry van die beskikbare literatuur oor laeinkomstevroue se ervaring van hulle heteroseksuele verhoudings. Aandag is in die besonder gegee aan die konstrukte van sosiale ondersteuning en intimiteit, wat albei as belangrike veranderlikes tydens die hantering van stres aangedui is. Daar is bevind dat, ondanks die feit dat daar meer stressore is wat met armoede in verband gebring word, baie min navorsing nog oor lae-inkomstevrouegedoen is. Wanneer die beskikbare literatuur egter vergelyk word, lyk dit asof daar belangrike verskille is tussen die verwagtinge wat onderskeidelik laeinkomstevroue en vroue uit die middelklas het ten opsigte van heteroseksuele verhoudinge. Die literatuur voer aan dat lae-inkomstevroue heteroseksuele verhoudings dikwels as 'n addisionele bron van stres beleef, veral aangesien tradisionele geslagsrolle 'n groter rol speel in verwagtinge rondom die verskaffing van sosiale ondersteuning. Dit lyk dus asof sommige lae-inkomstevrouein 'n poging om hulle nie aan tradisionele rolverwagtinge te onderwerp nie, verkies om nie te trou nie, maar om eerder na finansiële onafhanklikheid te streef in 'n poging om die mag in heteroseksueleverhoudings te behou. Die behoefte aan intimiteit is nie duidelik deur lae-inkomstevroue aangedui nie, maar wel 'n behoefte aan 'n enkelvoudige heteroseksuele verhouding. Alhoewel dlt gelyk het asof lae-lokomstevroue nie sosiale ondersteuning of intimiteit van hulle mansvriende verwag het nie, het hulle ander spesifieke verwagtinge genoem. Uit die literatuur wil dit lyk of lae-inkomstevroue met redelike sekerheid seks en die verwekking van kinders van hulle heteroseksuele verhoudings kon verwag, maar dat hulle ander verwagtinge dikwels teleurgestel word. Nogtans word heteroseksuele verhoudings as 'n belangrike manier gesien waarop lae-inkomstevroue status in die gemeenskap kan verkry. Die huidige literatuurstudie belig ook die aansienlike oorvleueling tussen die konstrukte van sosiale ondersteuning en intimiteit. Ten slotte is dit duidelik dat verdere navorsing gedoen moet word (veral in Suid-Afrika) om te bepaal hoe laeinkomstevrouehulle heteroseksueleverhoudings beleef.
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Bellamy, John Paul. "Language attitudes in England and Austria : comparing reactions towards high and low prestige varieties in Manchester and Vienna." Thesis, University of Manchester, 2011. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:119017.
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This thesis presents results obtained during 2007/08 in the course of doctoral research into attitudes towards linguistic variation in England and Austria and is based in part on a study by Lees (2000). In this project attitudes amongst British and Austrian informants towards low-prestige ('dialect') and high-prestige varieties are investigated on the basis of assumptions made about speakers of these varieties. The data are collected by means of the 'matched-guise technique', whereby informants listen to a number of recordings of low and high-prestige varieties and note their reactions on the basis of a selection of traits using a semantic differential. In this way the research aims to ascertain whether a pattern emerges, where the informants' perception of the guises is influenced by the prestige of the spoken variety. The results in England and in Austria are compared in order to determine similarities and differences in language attitudes towards low and high-prestige varieties in the two countries. Some results presented here correspond to certain social expectations, with high-prestige speakers being associated with better-paid employment and a better education. Other results, though, are less predictable, as where, for example, the female informants in England and in Austria judge the speakers more positively than the male informants, regardless of the prestige of the speaker's variety. In any case, there is evidence from both countries of the informants' evaluations of the speaker being influenced by their associations of the speaker's variety with that speaker's social status. The data also indicate that the social status of speakers in England is judged to a greater extent on the basis of their spoken variety than is the case in Austria, where speakers are more used to switching freely between points on the standard-dialect continuum and are consequently less judgemental in their perception of a speaker based purely on the evidence of their spoken variety.
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Gourmelen, Noel. "Measuring Low Fault Strain Rate with Synthetic Aperture Radar: Application to the Pacific-North America Plate Boundary." Scholarly Repository, 2009. http://scholarlyrepository.miami.edu/oa_dissertations/306.
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I use Synthetic Aperture Radar Interferometry (InSAR) to study the present deformation in the Western Basin and Range and Basin and Range - Sierra Nevada transition. I process 350 SAR data over 190·103 km2 for the period 1992 to 2002. Both stacking and time series processing were applied to produce precise (mm/yr) and high-resolution velocity map for the area. Two new processing techniques have been developed. The first technique solves for the long wavelength ambiguities of the InSAR derived velocity map that arise due to uncertainty in the orbital parameter of the satellite. The technique assimilates continuous GPS data into the InSAR time-series processing. The second technique extracts the horizontal and vertical components of the deformation field from two adjacent radar tracks. I applied stacking to study the transient deformation across the Central Nevada Seismic Belt and interseismic strain accumulation across the Eastern California Shear Zone. I show that the current deformation across the Central Nevada Seismic Belt can be explained by a combination of inter-seismic, post-seismic and anthropogenic deformation. The Post-Seismic deformation is associated with visco-elastic relaxation of the Earth's mantle in response to a centennial earthquake sequence of five ~M7 earthquakes along the Central Nevada Seismic Belt. The anthropogenic deformation is a response of the bedrock to water withdrawal in support of mining activity. A more evolved time-series approach that solves for orbital errors is applied across the Eastern California Shear Zone. The study shows that the Hunter Mountain - Panamint Valley fault system accommodates ~5 mm/yr, a faster rate than geological averages. The region of strain accumulation is a narrow band of ~10 km centered on the Hunter mountain fault, and indicates a very shallow locking depth in agreement with an active low angle normal fault system.
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Calvo, García-Maroto Marta. "Analysis of long-term gravity records in europe : consequences for the retrieval of small amplitude and low frequency signals including the core resonance effects." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAH003/document.
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L’étude des variations temporelles de gravité ont une longue tradition en Europe Centrale. Dans la station, J9, située à Strasbourg depuis les années 1970, les trois principaux types de gravimètre (ressort, supraconducteur (SG), absolu) ont été utilisés. Ces séries permettent l’examen des améliorations instrumentales à partir de la stabilité à long terme et de la dérive instrumentale. Nous montrons que le SG est l’instrument le plus performant pour l’étude des marées de longues périodes et de faibles amplitudes. Nous montrons les résultats obtenus par analyse de marée de ces petites ondes. Nous estimons la période de la Free Core Nutation et nous recherchons celle de la Free Inner Core Nutation (FICN), qui n'a pas encore été observée. Pour cela nous faisons une étude précise, afin de séparer les ondes de faible amplitude, au voisinage de périodes possibles de la FICNThe study of temporal variations of gravity has a long tradition in Central Europe. Since the 1970s three main gravimeter types (spring, superconducting (SG) and absolute) have been set up at the J9 gravity station located in Strasbourg. These series allow us to review the instrumental improvements from the analyses of long term stability and instrumental drift. We show that the SG is the most powerful tool for thestudy of the low frequency and small amplitudes tides. We show the tidal analysis results for these tidal waves. We estimate the period of the Free Core Nutation and we seek the one of the Free Inner Core Nutation (FICN), which has not yet been observed. For this we make a careful study, in order to separate the low-amplitude waves in the vicinity of possible periods of FICN
La deformación elasto-gravitacional de la Tierra y las correspondientes variaciones temporales de la gravedad asociadas, registradas en la superficie terrestre mediante los gravímetros, son debidas a distintos fenómenos geofísicos con diferentes períodos y amplitudes, incluyendo entre otros a las denominadas mareas terrestres, que son el fenómeno que genera los efectos más fuertes (dichas mareas terrestres son los movimientos inducidos en la Tierra sólida y los cambios en su potencial gravitatorio derivados de las fuerzas de marea generadas por los cuerpos celestes).El objetivo principal de este trabajo consiste en mostrar la importancia tanto de la longitud de las series de datos de gravedad, como de la calidad de dichas series para mejorar nuestro conocimiento sobre la dinámica de la Tierra a través de los análisis de las mareas terrestres. [...]
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Patel, Mamta Jashvantlal. "Suppression of osteoblast activity by disuse is prevented by low magnitude mechanical loading through a bone morphogenic protein-dependent Mechanism." Diss., Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22663.
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Musculoskeletal pathologies associated with decreased bone mass, including osteoporosis and disuse-induced bone loss, affect millions of Americans annually. Many pharmaceutical treatments have slowed osteoporosis, but there is still no countermeasure for bone loss observed in astronauts. Additionally, high magnitude and low frequency impact has been recognized to increase bone and muscle mass under normal but not microgravity conditions. However, a low magnitude and high frequency (LMHF) mechanical load experienced in activities such as postural control has also been shown to be anabolic to bone. While several clinical trials have demonstrated that the LMHF mechanical loading normalizes bone loss in vivo, the target tissues and cells of the mechanical load and underlying mechanisms mediating the responses are unknown. As such, the objectives of this project are to analyze cellular and molecular changes induced in osteoblasts by LMHF loading and to investigate the utility of a LMHF mechanical load in mitigating microgravity-induced bone loss. The central hypothesis of the project is that simulated microgravity or disuse conditions induce bone loss by inhibiting expression of genes critical in regulating bone formation, osteoblast differentiation, and subsequent mineralization while a LMHF mechanical load prevents these effects. To test this hypothesis, we developed an in vitro disuse system using the Random Positioning Machine (RPM). For the first time, we reported systemic gene expression studies in 2T3 preosteoblasts using the RPM disuse system showing that 140 genes were altered by RPM exposure with over two-fold statistically significant changes. Moreover, we also utilized an independent simulator called the Rotating Wall Vessel (RWV) to partially validate the in vitro disuse systems and to confine the list of genes to those most critical in regulating bone formation. After comparative studies, we constricted the list to 15 commonly changed genes, three of which were not only decreased with disuse but also increased with mechanical loading in vivo. Furthermore, we employed the RPM disuse system to evaluate the mechanism by which a LMHF load mitigates bone loss. Exposure of osteoblasts to the RPM decreased both ALP activity and mineralization even in the presence of bone morphogenic protein 4 (BMP4), and the LMHF mechanical loading prevented the RPM-induced decrease in both markers. Mineralization induced by LMHF mechanical loading was enhanced by treatment with BMP4 and blocked by the BMP antagonist noggin, suggesting a role for BMPs in this response. In addition, LMHF mechanical loading rescued the RPM-induced decrease in gene expression of ALP, runx2, osteomodulin, parathyroid hormone receptor 1, and osteoglycin. These findings show that osteoblasts directly respond to LMHF mechanical loading, potentially leading to normalization or prevention of bone loss caused by disuse or microgravity conditions. The mechanosensitive genes identified here provide potential targets for pharmaceutical treatments that may be used in combination with LMHF mechanical loading to better treat osteoporosis, disuse-induced bone loss, or microgravity-induced bone loss.
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Brogno, Luigi. "Nocturnal low-level jets over complex terrain: driving mechanisms and analytical modeling." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2020. http://amslaurea.unibo.it/20539/.
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Several studies in the Atmospheric Physics have focused on the analysis of the atmospheric circulation phenomena at the small scale and turbulent processes within the planetary boundary layer (PBL), whose formation and evolution is complicated by the topography.
The Low-Level Jet (LLJ) is one of the most studied phenomena and it is not yet completely understood. It consists in the occurrence of strong winds within a thin layer of the PBL.
A particular case is the formation of double-nose LLJs (or multiple LLJs), i.e. the simultaneous occurrence of two (or multiple) noses within the PBL.
Analysing data retrieved in complex terrain during the MATERHORN field campaigns, the objectives of this thesis are to understand the mechanisms which drive the formation of the double-nose LLJs identified using a newly-proposed criterion that upgrade the already existing ones.
The new identification criterion is used to analyse quiescent Intensive Observing Periods (IOPs), in which nocturnal stable boundary-layer conditions and local thermal circulation are not altered or driven by synoptic forcing.
During these IOPs, the formation of a LLJ due to inertial oscillations is typical few hours after the sunset.
However, the LLJ structure can be temporary perturbed generating a double-nose LLJ.
Two double-nose LLJ driving mechanisms are identified.
The wind-driven mechanism is when the two noses are associated with different air masses flowing one on top of the other.
The wave-driven mechanism is when a surface perturbation generates an inertial-gravity wave which transports momentum during its propagation.
Momentum is lost by the LLJ nose and transported upward where a second one is generated.
Furthermore, the evolution of the LLJs driven by the inertial oscillations is investigated by means of two models retrieved from the literature.
The models provides similar representation of the observed LLJs, concluding that the LLJs are well simulated when they are fully developed.
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Parmhed, Oskar. "Near surface atmospheric flow over high latitude glaciers." Doctoral thesis, Stockholm University, Department of Meteorology, 2004. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-197.
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In this thesis various descriptions of the near surface atmospheric flow over a high latitude glacier is used in an effort to increase our understanding of the basic flow dynamics there.
Through their contribution to sea-level change, mountain glaciers play a significant role in Earth’s climate system. Properties of the near surface atmospheric flow are important for understanding glacier response to climate change.
Here, the near surface atmospheric flow is studied from several perspectives including the effects of both rotation and slope. Rotation is an important aspect of most atmospheric flows and its significance for mesoscale flows have gained recognition over the last years. Similarly, the very stable boundary layer (VSBL) has lately gained interest. Within a VSBL over sloping terrain katabatic flow is known to be usual and persistent. For the present thesis a combination of numerical and simple analytical models as well as observations from the Vatnajökull glacier on Iceland have been used. The models have continuously been compared to available observations. Three different approaches have been used: linear wave modeling, analytic modeling of katabatic flow and of the Ekman layer, and numerical simulations of the katabatic flow using a state of the art mesoscale model. The analytic models for the katabatic flow and the Ekman layer used in this thesis both utilizes the WKB method to allow the eddy diffusivity to vary with height. This considerably improves the results of the models. Among other findings it is concluded that: a large part of the flow can be explained by linear theory, that good results can be obtained for surface energy flux using simple models, and that the very simple analytic models for the katabatic flow and the Ekman layer can perform adequately if the restraint of constant eddy diffusivity is relieved.
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Booth, Alastair Murray. "Detection and characterisation of low-concentration components in drugs and drug formulations : exploring the value of soft X-ray synchrotron radiation techniques for the pharmaceutical industry." Thesis, University of Manchester, 2008. http://www.manchester.ac.uk/escholar/uk-ac-man-scw:190668.
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Surface properties affect pharmaceuticals by influencing physical behaviour, which can cause problems for both formulation and medication. Poorly water soluble compounds are often modified with polymer surfactants. The presence of amorphous material, due to its effect on dissolution rate, can modify the bioavailability of a compound. This thesis reports the novel application of X-ray Absorption Spectroscopy (XAS) and X- ray Photoelectron Spectroscopy (XPS) to surface related pharmaceutical problems. XAS is sensitive to bond angles, local symmetry and oxidation states and XPS provides information on local chemical environment. Both have a probing depth <10 nm in the soft X-ray range. It is shown that XAS and XPS are capable of determining the physicalcoverage of ultra-thin polymer coatings. In situ XAS confirmed they formraft-like structures on the drug surface. Adsorbed water could also be de-tected on the surface and this corresponds to improvement in dissolutionrate, which implies an improvement in bioavailability. XAS was capableof distinguishing between amorphous and crystalline batches of two drugsat the surface. It was also able to detect a nanoscale amorphous overlayerin predominantly crystalline micronised batches of the drug. High relativehumidity was shown to recrystallise both the amorphous and micronisedbatches. X-ray PhotoElectron Emission Microscopy (XPEEM) of pharma-ceutical compounds was attempted but, due to the higher beamflux required,sample damage and charging effects were too great to draw any meaningfulconclusions at this time.
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Nakanishi, Kunihito. "A study on magnetic fluctuations over the ionospheric E-region driven by the lower atmospheric phenomena." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215320.
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Gandikota, Vs Gurunath. "Instabilités d'interfaces fluides en apesanteur spatiale lors d'un changement brutal ou périodique d'accélération." Thesis, Grenoble, 2013. http://www.theses.fr/2013GRENY036/document.
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L'étude du comportement d'un fluide proche de son point critique et soumis à des vibrations ou une variation rapide de gravité/acceleration est un sujet extrêmement intéressant. Les phénomènes physiques impliqués sont d'un grand intérêt non seulement pour la physique fondamentale mais aussi pour l'industrie spatiale. Dans cette thèse, trois problèmes sont principalement trait&s: (i) Etude de l'interaction de vibrations harmoniques avec une couche limite thermique dans un fluide supercritique en absence de gravité, (ii) Etude de l'interaction de vibrations avec une interface liquide/vapeur d'un fluide sous−critique sous plusieurs niveaux de gravité (les instabilités de Faraday et d'onde gelée, l'équilibre dynamique d'une interface) et (iii) Etude du phénomène de geyser à l'intérieur d'un réservoir partiellement rempli d'oxygène lorsqu'il est soumis à une variation rapide de la gravité (ou accélération). La thèse comporte une partie expérimentale et une partie numérique. Des expériences ont été réalisées sur les installations HYLDE et OLGA du CEA Grenoble utilisant respectivement les fluides H2 et O2 dans la zone sous−critique. Des simulations numériques sont réalisées pour étudier la stabilité d'une couche limite thermique et la dynamique d'une interface fluide soumise à une variation rapide de la gravité en utilisant des codes numériques basées sur le méthode volumes finis utilisant les algorithmes SIMPLER et VOF−PLIC respectivement. Plusieurs résultats intéressants ont été obtenus. Différents phénomènes ont été étudiés et quantifiés, comme l'instabilité de Faraday et l'instabilité d'onde gelée dans le domaine sous−critique et l'instabilité parametrique et l'instabilité Rayleigh−vibrationnelle dans le domaine supercritique. Les expériences ont permis de bien comprendre les raisons de la transition de l'instabilité de Faraday vers une structuration en bandes verticales très près du point critique. Les expériences et les simulations numériques sur le phénomène de geyser ont aidé à développer des corrélations empiriques pour les vitesses de la bulle et du geyser en prenant en compte les effets des paroisThe behavior of a near-critical fluid subjected to vibration or a rapid variation of acceleration is an extremely interesting topic of research. The resulting physical phenomena are of great interest in view of the fundamental physics involved and have great relevance to the space industry. The thesis addresses mainly three problems: (i) study of the interaction of harmonic vibration with a thermal boundary layer of a supercritical fluid under the absence of gravity, (ii) study of the inter- action of vibration with the liquid−vapor interface of a near−critical fluid under various gravity levels (Faraday and frozen wave instabili- ties, dynamic equilibrium of the interface) (iii) study of the geysering phenomenon inside a reservoir partially filled with a liquid when it is subjected to a rapid variation of gravity. Experiments are conducted onboard the zero−g installations HYLDE and OLGA developed by CEA Grenoble using H2 and O2 as the work- ing fluids. Numerical simulations are carried out using finite volume codes based on SIMPLER (for the problem involving the supercriti- cal fluid) and VOF−PLIC (for the interface dynamics problem under rapid variation of gravity). New and interesting results have been obtained. Various phenom- ena like the Faraday instability and the frozen wave instability in the sub−critical region and the parametric instability and the Rayleigh−vibrational instability in the supercritical region have been quantified. The experiments have successfully explained the reason behind the transition of the Faraday instability into vertical band pattern very close to the critical point. Experiments and numerical simulation of the geysering phenomenon have helped to evolve empir- ical correlations for the bubble rise and geyser edge velocities taking into account the effect of walls on these velocities
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Braglia, Matteo. "Initial conditions for cosmological perturbations in scalar-tensor dark-energy models." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/13860/.
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We discuss the evolution and imprints of isocurvature initial conditions for the scalar field in scalar tensor extensions of Einstein gravity. We consider the simplest models of scalar tensor theories, as Induced gravity (IG, which can be recasted in form of Jordan-Brans-Dicke theory by a redefinition of the scalar field) or non-minimally coupled (NMC) scalar fields in which the acceleration of the Universe is connected to a variation of the effective Planck mass. After introducing the fundamental ideas of cosmological perturbation theory and scalar tensor theories of gravity, we give the evolution equations for matter, metric and scalar field fluctuations in synchronous gauge. We use this set of equations for both the IG and the NMC models to find a new isocurvature solution in which the scalar field fluctuations compensate for the relativistic components respectively. We also show how we can generalize the well known isocurvature modes in Einstein GR to these models. We show the different evolution of cosmological fluctuations for these isocurvature initial conditions compared to the standard adiabatic one. After that, we compute the CMB angular power spectrum for these solutions in the IG model, with the help of a modified Einstein-Boltzmann CLASS code. In particular the CMB power spectrum is computed separately for adiabatic and isocurvature initial conditions, i.e. for totally uncorrelated modes, and with arbitrary correlations leading to an interesting explanation of the lack of power in the low multipoles region of the CMB temperature power spectrum. Finally we show how a simple model of double inflation in IG could explain the generation of the new isocurvature mode.
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Riess, Julien. "Intensification de la brique « fermentation alcoolique » de substrats betteraviers (et autres substrats) pour la production d’éthanol." Phd thesis, Toulouse, INPT, 2012. http://oatao.univ-toulouse.fr/8513/1/riess.pdf.
Full textAbstract:
L’éthanol est un composé à usages très variés allant de la chimie à l’agroalimentaire. Cependant, la croissance actuelle du marché se fait essentiellement autour de l’utilisation de l’éthanol en tant que carburant. L’objectif de ce projet est d’intensifier la production d’éthanol à partir du sirop basse pureté, produit de la seconde cristallisation des jus d’extraction de betterave, afin de diminuer les consommations en énergie et en eau pour la production d’éthanol. Pour ce faire, en partenariat avec l’UNGDA et l’ADEME, nous avons mené des travaux de recherche sur les fermentations à haute densité afin d’obtenir des vins à teneur plus élevée en éthanol. A l’issu d’un état de l’art et de quatre visites dans des ateliers de production, une stratégie de recherche en trois points a été établie. Le premier point a consisté en la recherche d’une composition de milieu de fermentation permettant d’augmenter la concentration finale en éthanol. Le second point a eu pour but de déterminer si les besoins en nutriments se limitaient uniquement à la phase de croissance ou au contraire si l’apport de ces nutriments était bénéfique tout au long de la fermentation. Le dernier point a quant à lui utilisé l’ensemble des résultats obtenus pour définir une conduite de procédé, permettant d’obtenir la concentration finale en éthanol la plus élevée possible. Ces résultats montrent qu’il est possible de réaliser des fermentations haute densité à partir de sirop basse pureté et d’obtenir 15,2 % (v/v) d’éthanol en fin de fermentation. L’application de ces travaux dans les ateliers de production permettrait d’économiser par litre d’éthanol pur, entre 20 et 30 % d’énergie pour la distillation, entre 35 et 49 % d’eau pour la réalisation des milieux de fermentation à partir de SBP et de diminuer de 23 à 38 % le volume de déchet produit après distillation. Ethanol is a compound with a wide usage range from chemistry to food. However, the current market growth mainly concerns the use of ethanol as fuel. The objective of this project was to intensify ethanol production from low purity syrup 2, which is a substrate from sugar beet, in order to reduce the consumptions of energy and water for its production. To do this, in partnership with UNGDA and ADEME, we have conducted research on high-gravity fermentations in order to increase the ethanol concentration at the end of the fermentation. With the coming of a state of the art and four visits in production facilities, a three points research strategy has been established. The first point consisted of fermentation medium composition finding in order to increase the final ethanol concentration at the end of the fermentation. The second point was to determine if the nutrients requirements were limited only during the growth phase or, on the contrary, if nutriments were beneficial throughout the fermentation. The latter point was to use the overall results to define a fermentation process, to obtain a final ethanol concentration as high as possible. These results show that it is possible to achieve high gravity fermentation from low purity syrup and reach a final ethanol concentration of 15.2 % (v/v). The application of this work in production facilities could save per liter of pure ethanol between 20 and 30% energy for distillation, between 35 and 49 % water for the production of fermentation media from SBP and decrease from 23 to 38 % of the volume of waste produced after distillation.