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1
Noll, Scott Allen. „Residual stress fields due to laser-pulse-generated shock waves“. The Ohio State University, 1999. http://rave.ohiolink.edu/etdc/view?acc_num=osu1407411599.
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2
Elfadel, Ibrahim Mohammad. „From random fields to networks“. Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/12616.
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3
Salerno, Grazia. „Artificial gauge fields in photonics and mechanical systems“. Doctoral thesis, Università degli studi di Trento, 2016. https://hdl.handle.net/11572/368464.
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Recent technological advances in quantum simulators have proven that synthetic materials are very well suited to study and realise many condensed matter models.
However, many of these synthetic systems are characterized by neutral particles that do not couple to real gauge fields. In order to simulate interesting electromagnetic phenomena, such as the topological insulators, or the Landau levels, there is the need for the implementation of artificial gauge fields. In particular, the topological insulators are very interesting both from the point of view of fundamental physics and concrete applications. They are bulk insulating materials that carry a certain number of edge states which are topologically protected against small perturbations of the system. An example of a topological insulator is the integer quantum Hall effect.
While there have been many works studying topological physics with quantum artificial systems, little attention was dedicated to the interplay of topology and the purely classical world. Only in the last couple of years, pioneering efforts to encode a non-trivial topology in the dynamical matrix or into the Hamiltonian of a system have proven that the hallmarks of a topological insulator are not the prerogative of quantum mechanics, but can be also observed with a classical system governed by Newton’s equations. The first part of this thesis is therefore based on our studies dedicated to the implementation of a classical analogue of the integer quantum Hall system, by realizing the Harper-Hofstadter model for classical frequency-modulated coupled harmonic oscillators.
The achievement of an artificial gauge field allows also for the deeper study of magnetic effects such as Landau levels.
In graphene, an inhomogeneous strain of the lattice is equivalent to an artificial pseudo-magnetic field, and the low-energy spectrum shows the formation of relativistic pseudo-Landau levels. The second part of the thesis is therefore focussed on the photonics honeycomb lattice geometry and our theoretical proposal for a configuration based on an intrinsically driven-dissipative system in which to probe the physics of the Landau levels, and especially the spatial structure of their wavefunctions.
Finally, we have also studied spin-orbit coupling in a mechanical system of masses and springs induced by pre-tensioned springs that split the longitudinal and transverse couplings in the honeycomb geometry. We have presented the experimental results of a simple mechanical benzene composed of six pendula connected with pre-tensioned springs, to verify that the eigenmodes of this system are well described by our theory in the presence of spin-orbit coupling.
4
Salerno, Grazia. „Artificial gauge fields in photonics and mechanical systems“. Doctoral thesis, University of Trento, 2016. http://eprints-phd.biblio.unitn.it/1722/1/SalernoG_PhD.pdf.
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Recent technological advances in quantum simulators have proven that synthetic materials are very well suited to study and realise many condensed matter models.
However, many of these synthetic systems are characterized by neutral particles that do not couple to real gauge fields. In order to simulate interesting electromagnetic phenomena, such as the topological insulators, or the Landau levels, there is the need for the implementation of artificial gauge fields. In particular, the topological insulators are very interesting both from the point of view of fundamental physics and concrete applications. They are bulk insulating materials that carry a certain number of edge states which are topologically protected against small perturbations of the system. An example of a topological insulator is the integer quantum Hall effect.
While there have been many works studying topological physics with quantum artificial systems, little attention was dedicated to the interplay of topology and the purely classical world. Only in the last couple of years, pioneering efforts to encode a non-trivial topology in the dynamical matrix or into the Hamiltonian of a system have proven that the hallmarks of a topological insulator are not the prerogative of quantum mechanics, but can be also observed with a classical system governed by Newton’s equations. The first part of this thesis is therefore based on our studies dedicated to the implementation of a classical analogue of the integer quantum Hall system, by realizing the Harper-Hofstadter model for classical frequency-modulated coupled harmonic oscillators.
The achievement of an artificial gauge field allows also for the deeper study of magnetic effects such as Landau levels.
In graphene, an inhomogeneous strain of the lattice is equivalent to an artificial pseudo-magnetic field, and the low-energy spectrum shows the formation of relativistic pseudo-Landau levels. The second part of the thesis is therefore focussed on the photonics honeycomb lattice geometry and our theoretical proposal for a configuration based on an intrinsically driven-dissipative system in which to probe the physics of the Landau levels, and especially the spatial structure of their wavefunctions.
Finally, we have also studied spin-orbit coupling in a mechanical system of masses and springs induced by pre-tensioned springs that split the longitudinal and transverse couplings in the honeycomb geometry. We have presented the experimental results of a simple mechanical benzene composed of six pendula connected with pre-tensioned springs, to verify that the eigenmodes of this system are well described by our theory in the presence of spin-orbit coupling.
5
Krasnodebski, Jan K. (Jan Kazimierz). „Numerical simulations of lobed mixer flow fields“. Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/37793.
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6
Miao, Sha Ph D. Massachusetts Institute of Technology. „Design of miniature floating platform for marginal fields“. Thesis, Massachusetts Institute of Technology, 2013. http://hdl.handle.net/1721.1/81611.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 133-136).
This thesis presents the design of a novel type of miniature floating offshore platforms with a heave plate attached at the keel, suitable for developing deep-water marginal fields. This design features a small displacement, easy fabrication, reduced cost and a favourable motion performance in waves. The design process includes the preliminary estimation, hydrodynamic analysis and hull optimization. A self-developed model "Discrete Vortex Ring Model" (DVRM) to efficiently estimate the viscous drag due to the vortex shedding of the oscillatory heave plate is presented in details. This new model DVRM combined with the standard radiation/diffraction code WAMIT is used to analyse the effect of different geometric parameters on the motion behaviour of the platform. Finally, these two models are integrated into a genetic optimization algorithm to obtain a final optimal design.
by Sha Miao.
S.M.
7
Narayanan, Subramani Deepak. „Probabilistic regional ocean predictions : stochastic fields and optimal planning“. Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/115733.
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Thesis: Ph. D. in Mechanical Engineering and Computation, Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Cataloged from PDF version of thesis. "Submitted to the Department of Mechanical Engineering and Center for Computational Engineering."
Includes bibliographical references (pages 253-268).
The coastal ocean is a prime example of multiscale nonlinear fluid dynamics. Ocean fields in such regions are complex, with multiple spatial and temporal scales and nonstationary heterogeneous statistics. Due to the limited measurements, there are multiple sources of uncertainties, including the initial conditions, boundary conditions, forcing, parameters, and even the model parameterizations and equations themselves. To reduce uncertainties and allow long-duration measurements, the energy consumption of ocean observing platforms need to be optimized. Predicting the distributions of reachable regions, time-optimal paths, and risk-optimal paths in uncertain, strong and dynamic flows is also essential for their optimal and safe operations. Motivated by the above needs, the objectives of this thesis are to develop and apply the theory, schemes, and computational systems for: (i) Dynamically Orthogonal ocean primitive-equations with a nonlinear free-surface, in order to quantify uncertainties and predict probabilities for four-dimensional (time and 3-d in space) coastal ocean states, respecting their nonlinear governing equations and non-Gaussian statistics; (ii) Stochastic Dynamically Orthogonal level-set optimization to rigorously incorporate realistic ocean flow forecasts and plan energy-optimal paths of autonomous agents in coastal regions; (iii) Probabilistic predictions of reachability, time-optimal paths and risk-optimal paths in uncertain, strong and dynamic flows. For the first objective, we further develop and implement our Dynamically Orthogonal (DO) numerical schemes for idealized and realistic ocean primitive equations with a nonlinear free-surface. The theoretical extensions necessary for the free-surface are completed. DO schemes are researched and DO terms, functions, and operations are implemented, focusing on: state variable choices; DO norms; DO condition for flows with a dynamic free-surface; diagnostic DO equations for pressure, barotropic velocities and density terms; non-polynomial nonlinearities; semi-implicit time-stepping schemes; and re-orthonormalization consistent with leap-frog time marching. We apply the new DO schemes, as well as their theoretical extensions and efficient serial implementation to forecast idealized-to-realistic stochastic coastal ocean dynamics. For the realistic simulations, probabilistic predictions for the Middle Atlantic Bight region, Northwest Atlantic, and northern Indian ocean are showcased. For the second objective, we integrate data-driven ocean modeling with our stochastic DO level-set optimization to compute and study energy-optimal paths, speeds, and headings for ocean vehicles in the Middle Atlantic Bight region. We compute the energy-optimal paths from among exact time-optimal paths. For ocean currents, we utilize a data-assimilative multiscale re-analysis, combining observations with implicit two-way nested multi-resolution primitive-equation simulations of the tidal-to-mesoscale dynamics in the region. We solve the reduced-order stochastic DO level-set partial differential equations (PDEs) to compute the joint probability of minimum arrival-time, vehicle-speed time-series, and total energy utilized. For each arrival time, we then select the vehicle-speed time-series that minimize the total energy utilization from the marginal probability of vehicle-speed and total energy. The corresponding energy-optimal path and headings be obtained through a particle backtracking equation. For the missions considered, we analyze the effects of the regional tidal currents, strong wind events, coastal jets, shelfbreak front, and other local circulations on the energy-optimal paths. For the third objective, we develop and apply stochastic level-set PDEs that govern the stochastic time-optimal reachability fronts and paths for vehicles in uncertain, strong, and dynamic flow fields. To solve these equations efficiently, we again employ their dynamically orthogonal reduced-order projections. We develop the theory and schemes for risk-optimal planning by combining decision theory with our stochastic time-optimal planning equations. The risk-optimal planning proceeds in three steps: (i) obtain predictions of the probability distribution of environmental flows, (ii) obtain predictions of the distribution of exact time-optimal paths for the forecast flow distribution, and (iii) compute and minimize the risk of following these uncertain time-optimal paths. We utilize the new equations to complete stochastic reachability, time-optimal and risk-optimal path planning in varied stochastic quasi-geostrophic flows. The effects of the flow uncertainty on the reachability fronts and time-optimal paths is explained. The risks of following each exact time-optimal path is evaluated and risk-optimal paths are computed for different risk tolerance measures. Key properties of the risk-optimal planning are finally discussed. Theoretically, the present methodologies are PDE-based and compute stochastic ocean fields, and optimal path predictions without heuristics. Computationally, they are several orders of magnitude faster than direct Monte Carlo. Such technologies have several commercial and societal applications. Specifically, the probabilistic ocean predictions can be input to a technical decision aide for a sustainable fisheries co-management program in India, which has the potential to provide environment friendly livelihoods to millions of marginal fishermen. The risk-optimal path planning equations can be employed in real-time for efficient ship routing to reduce greenhouse gas emissions and save operational costs.
by Deepak Narayanan Subramani.
Ph. D. in Mechanical Engineering and Computation
8
Saidi, Sasan John. „Experimental investigation of 2D and 3D internal wave fields“. Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/67799.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 113-116).
The generation of 2D and 3D internal wave fields is extensively studied via planarand stereo- Particle Image Velocimetry (PIV) flow field measurement techniques. A benchmark was provided by an experiment involving tidal flow over a 2D Gaussian ridge; this study providing a counterpart with which studies of a 3D incised Gaussian ridge could be compared with. To further benchmark the 3D wave field studies an experiment involving the canonical setup of a vertically oscillating sphere was performed and the results compared with the latest theory; the excellent agreement obtained provided confidence in the stereo-PIV method for studying fully three-dimensional internal waves. The 3D incised Gaussian ridge generates a wave field characterized by noticeable, though weak, out-of-plane forcing that evolves from a relatively strong to a weakly localized quantity as the wave field transitions from super- to subcritical, while the in-plane velocity field appears nearly identical to its 2D counterpart.
by Sasan John Saidi.
S.M.
9
Hauf, Dagmar E. (Dagmar Elisabeth). „Two-parameter characterization of crack-tip fields during thermal transients“. Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/36473.
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10
Wong, Joseph S. H. (Joseph Sze Hsuan). „EDTA-enhanced metal contaminant removal from soils by electric fields“. Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/36053.
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11
Ferris, David S. M. (David Lee) Massachusetts Institute of Technology. „Time-optimal multi-waypoint mission planning in dynamic flow fields“. Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/118662.
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Thesis: Nav. E., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.
This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 43-49).
This thesis demonstrates the use of exact equations to predict time-optimal mission plans for a marine vehicle that visits a number of locations in a given dynamic ocean current field. The missions demonstrated begin and end in the same location and visit a finite number of locations or waypoints in the minimal time; this problem bears close resemblance to that of the classic "traveling salesman," albeit with the added complexity of a continuously changing flow field. The paths, or "legs," between all goal waypoints are generated by numerically solving exact time-optimal path planning level-set differential equations. The equations grow a reachability front from the starting location in all directions. Whenever the front reaches a waypoint, a new reachability front is immediately started from that location. This process continues until one set of reachability fronts has reached all goal waypoints and has returned to the original location. The time-optimal path for the entire mission is then obtained by trajectory backtracking, going through the optimal set of reachability fields in reverse order. Due to the spatial and temporal dynamics, a varying start time results in different paths and durations for each leg and requires all permutations of travel to be calculated. Even though the method is very efficient and the optimal path can be computed serially in real-time for common naval operations, for additional computational speed, a high-performance computing cluster was used to solve the level set calculations in parallel. This method is first applied to several hypothetical missions. The method and distributed computational solver are then validated for naval applications using an operational multi-resolution ocean modeling system of real-world current fields for the complex Philippines Archipelago region. Because the method calculates the global optimum, it serves two purposes. It can be used in its present form to plan multi-waypoint missions offline in conjunction with a predictive ocean current modeling system, or it can be used as a litmus test for approximate future solutions to the traveling salesman problem in dynamic flow fields.
by David Ferris.
Nav. E.
S.M.
12
Aldebs, Alyaa I. „Coupling of Mechanical and Electromagnetic Fields Stimulation for Bone Tissue Engineering“. Wright State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=wright1527185662564699.
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13
Hagg, Alexandre F. (Alexandre Frédèric) 1975. „Contracting force fields in robot navigation and extension to other problems“. Thesis, Massachusetts Institute of Technology, 2000. http://hdl.handle.net/1721.1/89286.
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14
Watring, Dale A. (Dale Allen). „Effects of static axial magnetic fields on directional solidification of HgCdTe“. Thesis, Massachusetts Institute of Technology, 1997. http://hdl.handle.net/1721.1/33820.
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15
Mizerak, Jordan (Jordan P. ). „Experimental analysis of boiling enhancement from surfactant addition with electric fields“. Thesis, Massachusetts Institute of Technology, 2014. http://hdl.handle.net/1721.1/92201.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2014.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 36-37).
This thesis consists of an experimental investigation of the effect of surfactants on the boiling curve of water. Via adsorbtion to the boiling surface, surfactants alter the surface energy interaction during bubble formation at nucleation sites. The surfactants initially enhance the heat transfer coefficient at the onset of nucleate boiling due to higher nucleation density and higher bubble departure frequency. The critical heat flux, on the other hand, generally dropped by nearly 50% in the presence of surfactants. As these surfactants are charged molecules, the application of an electric field was used to increase or decrease adsorption of surfactants on the boiling surface, thereby tuning the level of boiling enhancement during the onset of nucleate boiling and further illustrating the role of surfactants in the boiling process.
by Jordan Mizerak.
S.B.
16
Barakati, Amir. „Dynamic interactions of electromagnetic and mechanical fields in electrically conductive anisotropic composites“. Diss., University of Iowa, 2012. https://ir.uiowa.edu/etd/3562.
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Recent advances in manufacturing of multifunctional materials have provided opportunities to develop structures that possess superior mechanical properties with other concurrent capabilities such as sensing, self-healing, electromagnetic and heat functionality. The idea is to fabricate components that can integrate multiple capabilities in order to develop lighter and more efficient structures. In this regard, due to their combined structural and electrical functionalities, electrically conductive carbon fiber reinforced polymer (CFRP) matrix composites have been used in a wide variety of applications in most of which they are exposed to unwanted impact-like mechanical loads. Experimental data have suggested that the application of an electromagnetic field at the moment of the impact can significantly reduce the damage in CFRP composites. However, the observations still need to be investigated carefully for practical applications. Furthermore, as the nature of the interactions between the electro-magneto-thermo-mechanical fields is very complicated, no analytical solutions can be found in the literature for the problem.
In the present thesis, the effects of coupling between the electromagnetic and mechanical fields in electrically conductive anisotropic composite plates are studied. In particular, carbon fiber polymer matrix (CFRP) composites subjected to an impact-like mechanical load, pulsed electric current, and immersed in the magnetic field of constant magnitude are considered. The analysis is based on simultaneous solving of the system of nonlinear partial differential equations, including equations of motion and Maxwell's equations. Physics-based hypotheses for electro-magneto-mechanical coupling in transversely isotropic composite plates and dimension reduction solution procedures for the nonlinear system of the governing equations have been used to reduce the three-dimensional system to a two-dimensional (2D) form. A numerical solution procedure for the resulting 2D nonlinear mixed system of hyperbolic and parabolic partial differential equations has been developed, which consists of a sequential application of time and spatial integrations and quasilinearization. Extensive computational analysis of the response of the CFRP composite plates subjected to concurrent applications of different electromagnetic and mechanical loads has been conducted. The results of this work verify the results of the previous experimental studies on the subject and yield some suggestions for the characteristics of the electromagnetic load to create an optimum impact response of the composite.
17
Wang, Xianghong. „Semiconductor Crystal Growth by Vertical Bridgman and Gradient Freezing Processes with Applied Fields“. NCSU, 2006. http://www.lib.ncsu.edu/theses/available/etd-04252006-141628/.
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Integrated circuits and optoelectronic devices are produced on surfaces of thin wafers sliced from a semiconductor crystal. The performance of the semiconductor is directly related to the uniformity of its composition. The crystal?s composition generally changes due to a changing melt composition with segregation coefficient not equal to unity. Therefore, a major objective during the growth of any semiconductor crystal is to minimize the variations of the crystal?s dopant or alloy composition. Externally-applied fields such as magnetic and electric fields can be used to provide electromagnetic damping or stirring of the melt motion in order to minimize the dopant or alloy segregation in the melt and thus in the crystal. This research focuses on investigations of various semiconductor crystal growth processes from the melt in the presence of externally-applied fields. These processes are (1) the Bridgman-Stockbarger process in steady magnetic fields, (2) the vertical gradient freezing process using submerged heater growth in steady magnetic and electric fields, (3) the Bridgman process using submerged heater growth in a rotating magnetic field, and (4) the Bridgman process using submerged heater growth in a combination of steady and rotating magnetic fields. Numerical models are developed using a Chebyshev spectral method with Gauss-Lobatto collocation points. These models provide predictions of the temperature, velocity and concentration fields in the melt as well as the dopant or alloy concentration in the entire crystal.
18
Rouse, Jerry Wayne. „Energy-Based Boundary Element Method for High-Frequency Broadband Sound Fields in Enclosures“. NCSU, 2000. http://www.lib.ncsu.edu/theses/available/etd-20000911-161316.
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This work sets forth a new method for predicting the spatialvariation of mean square pressure within two-dimensionalenclosures containing high-frequency broadband sound fieldsand light to moderate absorption. In the new method, theenclosure boundaries are replaced by a continuousdistribution of broadband uncorrelated sources, each ofwhich provides a constituent field expressed in terms ofmean square pressure and time average intensity variables.Superposition of these fields leads to the overall meansquare pressure and time average intensity as a function ofposition. Boundary conditions for radiating and absorbingsurfaces are recast in terms of energy and intensityvariables. The approach is implemented as a boundaryelement formulation for efficient evaluation of the pressureand intensity fields in enclosures. In contrast totraditional boundary element methods, the new method isindependent of frequency. A two-dimensional model problemenclosure is investigated to verify the new method. The exact analytical solution for the mean square pressuredistribution within the model problem enclosure is obtainedand compared to the results predicted by the new method.The comparisons indicate that the new method is asignificant improvement upon classical diffuse field theoryand computationally efficient relative to traditional boundary element methods and ray tracing techniques.
19
Buckley, Patrick Regan 1981. „Actuation of shape memory polymer using magnetic fields for applications in medical devices“. Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/17927.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004."June 2004."
Includes bibliographical references (leaves 102-105).
A novel approach to the heating and actuation of shape memory polymer using dispersed Curie temperature thermo-regulated particles is proposed. Such a material has potential applications in medical devices which are delivered via catheters. A variety of tests were performed to determine the feasibility of this new approach to shape memory polymer actuation. Calorimetry tests were performed to quantify heat generation of various Nickel Zinc Ferrite particles. Dynamic Mechanical Thermal Analysis (DMTA), tensile strain recovery tests, and Differential Scanning Calorimetry (DSC) were used to measure the mechanical effects of various particle volume contents and sizes on shape memory polymer. These tests suggest that the proposed method of actuation is very feasible, rapid heating can be achieved and the addition of particles up to 10% volume content has a minimal effect on the mechanical properties of the shape memory polymer.
by Patrick Regan Buckley.
S.M.
20
Jacobs, Richard A. (Richard Alberto). „Two-dimensional modeling of the removal of contaminants from soils by electric fields“. Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11494.
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21
Belden, Jesse (Jesse Levi). „Quantitative imaging of the air-water flow fields formed by unsteady breaking waves“. Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/47893.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (p. 97-101).
An experimental method for simultaneously measuring the velocity fields on the air and water side of unsteady breaking waves is presented. The method is applied to breaking waves to investigate the physics of the air and water flow fields to further our knowledge of the impact of wave breaking on air-sea interaction. The method includes a novel technique for seeding the air flow such that the air velocity can be resolved in the absence of wind. Low density particles which have large Stokes drag and ability to respond to high frequency flow fluctuations are used to seed the air flow. Multi-camera, multi-laser particle image velocimetry (PIV) setups are applied to small-scale shoaling breaking waves, yielding fully time-resolved velocity fields. The surface tension of the fluid is altered and controlled to form both spilling and plunging breaking waves. Application of the developed experimental method to these breaking waves reveals interesting flow physics in the air and water. Results for the velocity and vorticity fields on the water side show qualitative agreement to published data, and comparisons are drawn where applicable. Quantitative experimental data for the air flow induced by wave breaking in the absence of wind has not previously been observed, to the author's knowledge. Revealing physical insights and observations are drawn from this novel data.
by Jesse Belden.
S.M.
22
Dzenitis, John M. „Soil chemistry effects and flow prediction in remediation of soils by electric fields“. Thesis, Massachusetts Institute of Technology, 1996. http://hdl.handle.net/1721.1/10973.
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23
Karabanova, Anastasiya. „The Effectiveness of Small-scale GTL Technologyin Remote Small Fields of Russia“. Thesis, KTH, Energiteknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-210216.
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In the Thesis, the problem of associated petroleum gas flaring both in Russia and in the world is revealed. The analysis of associated petroleum gas utilization methods in respect to the small remote oil fields is carried out. The Thesis shows the perspective of creating low and medium power autonomous installations for energy supply to the oil facilities in the remote areas with poorly developed energy infrastructure by processing associated petroleum gas in small-scale GTL technology unit. Taking into account specifics of small remote oil fields, GTL technology scheme was chosen among existing types and its material balance wascalculated. The schemes of both associated petroleum gas utilization and power production on site in the small remote fields were suggested and compared to each other from economical and environmental perspectives. Furthermore, the economic effect from themini-GTL technology introduction into the schemes was defined.I avhandlingen uppenbaras problemet med tillhörande petroleumsgaser både i Ryssland och i världen. Analysen av tillhörande oljeutnyttjande metoder för de små avlägsna oljefälten utförs. Avhandlingen visar perspektivet på att skapa låga och medelkraftiga autonoma installationer för energiförsörjning till oljeanläggningarna i de avlägsna områdena med dåligt utvecklad energiinfrastruktur genom att bearbeta tillhörande oljegas i småskaliga GTL-teknologienheten. Med tanke på särdrag hos små avlägsna oljefält valdes GTLteknikprogrammet bland befintliga typer och dess materialbalans beräknades. Systemen för både tillhörande oljeutnyttjande och kraftproduktion på plats i de små avlägsna fälten föreslogs och jämfördes med varandra från ekonomiska och miljömässiga perspektiv. Vidare definierades den ekonomiska effekten från mini-GTLteknikintroduktionen i systemen.
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Zhu, Haibin. „A novel methodology for high strain rate testing using full-field measurements and the virtual fields methods“. Thesis, Troyes, 2015. http://www.theses.fr/2015TROY0007/document.
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Ce travail se concentre sur le développement d'une procédure expérimentale d’essai mécanique à haute vitesse de déformation de matériaux. La nouveauté de ce travail est l'utilisation de champs d’accélération mesurés comme cellule de force, évitant la nécessité des mesures des forces externes. Pour identifier les paramètres constitutifs des matériaux testés à partir des mesures de champs, la méthode champs virtuels (MCV) basé sur le principe des puissances virtuelles (PPV) est utilisée. En dynamique, avec la MCV, il est possible de définir des champs virtuels qui mettent à zéro les puissances virtuelles des forces externes. Au lieu de cela, l'accélération obtenue grâce à une double dérivation temporelle des déplacements peut être utilisée comme une cellule de force. Enfin, les paramètres élastiques peuvent être identifiés directement à partir d’un système linéaire qui se construit en réécrivant le PPV avec autant de champs virtuels indépendants que d’inconnues à identifier. Cette procédure est d'abord validée numériquement par des simulations éléments finis puis mise en œuvre expérimentalement en utilisant deux configurations d’impact différentes. Les résultats confirment que effets inertiels peuvent être utilisés pour identifier les paramètres des matériaux sans la nécessité de mesurer la force d’impact, et sans exigence de déformations uniformes comme dans les procédures actuelles basées sur le montage de barres d’Hopkinson. Ces nouveaux développement ont le potentiel de mener à de nouveaux essais standards en dynamique rapideThis work focuses on the development of a novel experimental procedure for high strain rate testing of materials. The underpinning novelty of this work is the use of the full-field acceleration maps as a volume distributed load cell, avoiding the need for impact force measurement. To identify the constitutive parameters of materials from the full-field data, the Virtual Fields Method (VFM) based on the principle of virtual work is used here. In dynamics, using the VFM, it is possible to define particular virtual fields which can zero out the virtual work of the external forces. Instead, the acceleration obtained through second order temporal differentiation from displacement can be used as a load cell. Finally, the elastic parameters can be identified directly from a linear system which is built up through rewriting the principle of virtual work with as many independent virtual fields as unknowns. Thus, external force measurement is avoided, which is highly beneficial as it is difficult to measure in dynamics. This procedure is first numerically validated through finite element simulations and then experimentally implemented using different impact setups. Both results confirm that inertial effects can be used to identify the material parameters without the need for impact force measurements, also relieving the usual requirements for uniform/uniaxial stress in SHPB like test configurations. This exciting development has the potential to lead to new standard testing techniques at high strain rates
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Hotchkiss, Paul. „Development of a rotor model for the numerical simulation of helicopter exterior flow-fields“. Thesis, University of Cape Town, 2004. http://hdl.handle.net/11427/6774.
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Includes bibliographical references (leaves 84-85).A numerical methodology is developed to model the effect of a rotor on the surrounding flow-field. The model calculates the time-averaged aerodynamic forces exerted on the air by the fan blades within the blade-swept region, and permits the user to specify blade properties such as cross-sectional profile and orientation at a particular radial and azimuthal location. The calculated forces are included as source terms within the Reynolds-averaged Navier-Stokes equations for an incompressible fluid, which are solved by the commercial CFD solver, FLUENT. The effects of turbulence are incorporated through the use of Launder and Spalding's k-g turbulence model. This method is selected as being the most efficient use of the resources available, giving the economic advantages of a steady simulation, while allowing radial and azimuthal variations of rotor characteristics. In order to validate the accuracy of the numerical model for both aligned and non-aligned inflow conditions, results are compared with experimental data reported for an axial flow fan. Agreement between experimental and numerical results is excellent to good. Fan static pressure rise is closely predicted by the numerical solution, while fan power consumption and fan static efficiency are under and over-predicted respectively. This error may be attributed to frictional losses not accounted for in the numerical model. These include physical rotational instabilities, leading to increased mechanical losses, and tip effects due to the clearance between the fan blade tips and the fan casing. Trends are nevertheless consistently predicted by the numerical model for inflow angles up to 45°, and for the range of blade pitch settings used. The adverse effect of off-axis inflow on the fan static pressure rise is numerically predicted, while fan power consumption is found to remain independent of inflow angle, as had been experimentally observed. The rotor model is finally integrated with the fuselage of the CIRSTEL (Combined Infra-Red Suppression and Tail rotor Elimination) prototype in an analysis of the helicopter exterior flow-field. No experimental data for this configuration was available for validation purposes. However, the model is used in the simulation of several common helicopter flight conditions. Results are presented graphically, and generally indicate good agreement with physically observed phenomena.
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Clayton, John D. „Homogenization and incompatibility fields in finite strain elastoplasticity“. Diss., Georgia Institute of Technology, 2002. http://hdl.handle.net/1853/17666.
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Agwai, Abigail G. „A Peridynamic Approach for Coupled Fields“. Diss., The University of Arizona, 2011. http://hdl.handle.net/10150/204892.
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Peridynamics is an emerging nonlocal continuum theory which allows governing field equations to be applicable at discontinuities. This applicability at discontinuities is achieved by replacing the spatial derivatives, which lose meaning at discontinuities, with integrals that are valid regardless of the existence of a discontinuity. Within the realm of solid mechanics, the peridynamic theory is one of the techniques that has been employed to model material fracture. In this work, the peridynamic theory is used to investigate different fracture problems in order to establish its fidelity for predicting crack growth. Various fracture experiments are modeled and analyzed. The peridynamic predictions are made and compared against experimental findings along with predictions from other commonly used numerical fracture techniques. Additionally, this work applies the peridynamic framework to model heat transfer. Generalized peridynamic heat transfer equation is formulated using the Lagrangian formalism. Peridynamic heat conduction quantites are related to quanties from the classical theory. A numerical procedure based on an explicit time stepping scheme is adopted to solve the peridynamic heat transfer equation and various benchmark problems are considered for verification of the model. This paves the way for the coupling of thermal and structural fields within the framework of peridynamics. The fully coupled peridynamic thermomechanical equations are derived based on thermodynamic considerations, and a nondimensional form of the coupled thermomechanical peridynamic equations is also presented. An explicit staggered algorithm is implemented in order to numerically approximate the solution to these coupled equations. The coupled thermal and structural responses of a thermoelastic semi-infinite bar and a thermoelastic vibrating bar are subsequently investigated.
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Wang, Yongyi. „A two-parameter characterization of elastic-plastic crack tip fields and applications to cleavage fracture“. Thesis, Massachusetts Institute of Technology, 1991. http://hdl.handle.net/1721.1/13461.
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Wei, Quantum Jichi. „Time-optimal path planning in uncertain flow fields using stochastic dynamically orthogonal level set equations“. Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98749.
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Thesis: S.B., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2015.Cataloged from PDF version of thesis.
Includes bibliographical references (pages 53-54).
Path-planning has many applications, ranging from self-driving cars to flying drones, and to our daily commute to work. Path-planning for autonomous underwater vehicles presents an interesting problem: the ocean flow is dynamic and unsteady. Additionally, we may not have perfect knowledge of the ocean flow. Our goal is to develop a rigorous and computationally efficient methodology to perform path-planning in uncertain flow fields. We obtain new stochastic Dynamically Orthogonal (DO) Level Set equations to account for uncertainty in the flow field. We first review existing path-planning work: time-optimal path planning using the level set method, and energy-optimal path planning using stochastic DO level set equations. We build on these methods by treating the velocity field as a stochastic variable and deriving new stochastic DO level set equations. We use the new DO equations to simulate a simple canonical flow, the stochastic highway. We verify that our results are correct by comparing to corresponding Monte Carlo results. We explore novel methods of visualizing the results of the equations. Finally we apply our methodology to an idealized ocean simulation using Double-Gyre flows.
by Quantum Jichi Wei.
S.B.
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Mane, Prashant V. „Computational Study of Poppet Valves on Flow Fields“. Youngstown State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1391608907.
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Yalavarthi, Krishna Kumari. „Interplay of Electrical, Mechanical and Thermal Fields in III-N Nanostructures for LED Applications“. OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/708.
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This work aims at exploring the competing effects of various internal/built-in fields on the electronic structure and optical properties of III-N nanostructured (Quantum Dots and disk-in-a-wire) LEDs using a multiscale modeling approach. The objective is three-fold: (1) calculate the strain distribution, optical transition rates and one-particle electronic states using a 10-band sp3s* tight-binding framework; (2) to compute the effects of piezoelectric and pyroelectric polarization on the optical transition rates; (3) to model piezoelectricity in the wurtzite lattice, we have considered four different polarization models (based on the experimental /bulk and ab initio coefficients) in increased order of accuracy; (4) to study the origin and effects of these four competing internal fields on the electronic structure of self-assembled InN/GaN quantum dots having three different geometries, namely, box, dome, and pyramid; (5) integrating the NEMO3-D with commercial TCAD tool Synopsys to determine the terminal electrical and optical characteristics of InGaN/GaN disk-in-a-wire LEDs; and (6) finally to propose optimum device specifications for InGaN/GaN disk-in-a-wire LEDs to achieve maximum Internal Quantum Efficiency (IQE).
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Edalatpour, Mojtaba. „FERROFLUID DROPLET BEHAVIOR ON PATTERNED AND NON-PATTERNED SURFACES IN THE PRESENCE OF EXTERNAL UNIFORM MAGNETIC FIELDS“. Miami University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=miami1543455437727546.
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Naidoo, Vaneshen. „Implementation of a trim routine in a rotor model for the numerical simulation of helicopter flow-fields“. Master's thesis, University of Cape Town, 2006. http://hdl.handle.net/11427/8911.
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Includes bibliographical references (p. 82-83)The aim of the current project is to develop, validate and implement a trim routine for a numerical rotor model, developed for the use in simulations of a helicopter exterior flow-field. In this investigation a ROBIN fuselage geometry was utilised. Simulations of the fuselage without the rotor were carried out initially so that investigations into the computational grids and turbulence models could be done. The computational simulations were performed in the commercially available CFD solver, FLUENT® Computational grids were created for the near wall modelling approach and wall function approach. Some of the more applicable turbulence models available in the solver were compared. For the wall function approach grids the k - ε, and its variants, the RNG and realizable models were found to be suitable choices. For the near wall modelling approach grids used, the SST models performed the best. The rotor model used during this investigation utilised a combination of blade element and actuator disk theory. Forces exerted by the rotor are calculated with the use of blade characteristics and flow properties. These forces were applied to the domain as momentum sources terms. The rotor model was incorporated with the CFD solver, through the use of a User Defined Function (UDF). The method used to trim the rotor was the Newton-Raphson Iterative method. This trim routine was incorporated in the UDF used for the rotor model. Tests were conducted, on a 'rotor-alone' model, as well as the rotor and fuselage model. The trim routine was found to be rigorous and managed to trim the rotor in each of the tests conducted. Good agreement between experimental and numerical collective pitch angle and cyclic pitch coefficients were found. Also the effect of the fuselage on the trim conditions proved to be minimal.
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Yoon, Sung-ho. „Applications of the virtual fields method to the mechanical behaviour of rubbers under dynamic loading“. Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:1a1294b8-8759-41bc-bb53-fc0abbf69f2f.
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Experimental techniques for measuring the mechanical response of rubbers under dynamic loading are developed utilising the virtual fields method (VFM), to inversely identify constitutive behaviour from experimental observations. Rubbers and other 'soft' materials are difficult to characterize using traditional dynamic techniques such as the split Hopkinson bar: the low sound speed makes it difficult to achieve static equilibrium and the small supported forces give low signal-to-noise ratios in the experimental data. In this research, the dynamic VFM with the aid of high-speed imaging is applied to dynamic tensile experiments to resolve these difficulties. The VFM is a mathematical technique that makes use of the principle of virtual work. Manipulation of this equation enables us to remove the need for traditional force measurement, instead exploiting acceleration full-field data as a virtual load cell. Thus, the aforementioned difficulties are no longer of concern: the technique requires that the specimen is not in static equilibrium and that inertial forces are significant compared to material forces. Two dynamic tests and dynamic VFMs are developed and applied to tensile drop-weight and gas-gun driven experiments. The first uses small amplitude dynamic deformation superposed on static pre-stretching. Dynamic identifications at a number of pre-strains are collated to identify the complete nonlinear behaviour. The second utilizes a large strain amplitude of dynamic loading: one experiment characterizes the full response. Further applications of the dynamic VFM are explored in order to improve the first method and to extend the identification capability, and experiments performed at non-ambient temperatures allow a preliminary exploration of time-temperature superposition.
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Shtogun, Yaroslav. „Properties of Carbon Nanotubes Under External Factors: Adsorption, Mechanical Deformations, Defects, and External Electric Fields“. Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1771.
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Carbon nanotubes have unique electronic, optical, mechanical, and transport properties which make them an important element of nanoscience and nanotechnology. However, successful application and integration of carbon nanotubes into new nanodevices requires fundamental understanding of their property changes under the influence of many external factors. This dissertation presents qualitative and quantitative theoretical understanding of property changes, while carbon nanotubes are exposed to the deformations, defects, external electric fields, and adsorption. Adsorption mechanisms due to Van der Waals dispersion forces are analyzed first for the interactions of graphitic materials and biological molecules with carbon nanotubes. In particular, the calculations are performed for the carbon nanotubes and graphene nanoribbons, DNA bases, and their radicals on the surface of carbon nanotubes in terms of binding energies, structural changes, and electronic properties alterations. The results have shown the importance of many-body effects and discrete nature of system, which are commonly neglected in many calculations for Van der Waals forces in the nanotube interactions with other materials at nanoscale.
Then, the effect of the simultaneous application of two external factors, such as radial deformation and different defects (a Stone Wales, nitrogen impurity, and mono-vacancy) on properties of carbon nanotubes is studied. The results reveal significant changes in mechanical, electrical, and magnetic characteristics of nanotubes. The complicated interplay between radial deformation and different kinds of defects leads to the appearance of magnetism in carbon nanotubes which does not exist in perfect ones. Moreover, the combined effect of radial deformation and external electric fields on their electronic properties is shown for the first time. As a result, metal-semiconductor or semiconductor-metal transitions occur and are strongly correlated with the strength and direction of external electric field and the degree of radial deformations.
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Lawler, Clinton T. (Clinton Thomas). „A two-phase spherical electric machine for generating rotating uniform magnetic fields“. Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/39839.
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Thesis (Nav. E.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering; and, (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Includes bibliographical references (p. 133-138).
This thesis describes the design and construction of a novel two-phase spherical electric machine that generates rotating uniform magnetic fields, known as a fluxball machine. Alternative methods for producing uniform magnetic fields with air-cored solenoidal magnets are discussed and evaluated. Analytical and numerical models of these alternatives are described and compared. The design details of material selection, slot geometry, and mechanical connections are described for the fluxball machine. The electrical properties of the machine are predicted and measured. Based on these properties, two modes of operation for the fluxball machine, normal and resonant, are described, and reference tables of important operating parameters are given. The drive and measurement circuitry for the fluxball machine are described. The magnetic properties of the fluxball machine are measured using Hall effect sensors. The calibration of two different Hall effect sensors is performed, providing the ability to measure the magnetic fields accurately to ±1%. Measurements of the magnetic field in the uniform field region are taken and compared with predicted values. The attenuation and distortion of the magnetic fields due to diffusion through the inner fluxball winding is measured as a function of operating frequency.
(cont.) Finally, future uses of this machine for various applications are discussed. The fluxball machine provides uniform fields in the inner volume and point magnetic dipole fields in the exterior volume. Both regions are extremely useful for conducting controlled magnetic fields experiments. The fact that the machine can produce rotating fields of these types makes it particularly useful for applications in ferrofluid research and in experimental research related to large rotating machinery.
by Clinton T. Lawler.
S.M.
Nav.E.
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Wanklyn, Kevin Michael. „Experiments involving second order effects in high-intensity, high-frequency acoustic fields“. Diss., Kansas State University, 2008. http://hdl.handle.net/2097/12200.
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Doctor of PhilosophyDepartment of Mechanical and Nuclear Engineering
Sameer I. Madanshetty
Cavitation is a long studied phenomenon, fascinating and varied. Observed cavitation thresholds vary, typically ranging from the vapor pressure of the liquid to several atmospheres. Recent studies in cavitation involving very clean liquids give rise to thresholds that surpass 100 atmospheres. Calibrating such high intensity, high frequency, focused acoustic fields presents a significant challenge. The present investigation describes how it is possible to exploit the second order acoustic effect of radiation pressure to seek reliable calibration of the high intensity acoustic fields. Experiments describe how to account for the attendant second order effect of acoustic streaming in the evaluation of the radiation force to accomplish meaningful calibration. Beyond the measurement of the second order quantities associated with cavitation, the work also presents a first investigation of a direct estimation of implosion energies of collapsing bubbles near well-characterized surfaces.
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Chuah, Meng Yee (Meng Yee Michael). „Design principles of multi-axis, large magnitude force sensors based on stress fields for use in human and robotic locomotion“. Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/119276.
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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (pages 151-163).
Our ability to purposefully move across varied terrain requires us to have knowledge of the interactions our feet have with the external environment. However, existing sensing methods are inadequate to address the many unique demands of legged locomotion (i.e. fragile structures, incapable of handling large impact forces and noise caused by inertial loads during stride). This research is a study of how best to replicate the role of skin mechanoreceptors that enable our biological counterparts to perform dynamic maneuvers, and to develop innovative sensors that would empower the next generation of agile robots and smart shoes. The thesis introduces new design principles and methodologies for developing multi-axis, large magnitude force sensors based on stress fields to achieve these goals. Fabrication methods are presented for a monolithic elastomeric footpad that is biologically inspired, allowing it to measure large magnitude forces in both normal and shear axes while being compact, lightweight, impact robust, dust tight, and waterproof. The key principle that enables this is termed Stress Field (SF) based force sensing. Instead of funneling the load path directly through a few sensors in traditional force sensing methods, SF based force sensing allows the sampling of the stress distribution over the entire footpad surface through an array of piezoresistive sensor elements. The force estimator is constructed in two steps. First, linear regression fits the sensor readings to normal and shear forces. Then, machine learning is used as a nonlinear function approximator on the residual to further refine the force estimator to achieve greater accuracy. To enable these SF force sensor to be reproduced or customized for different needs, guidelines are provided in the form of simple design principles based on biological receptive fields, as well as an analytical model for cylindrical sensor types. For more complex sensor geometries, a material model of the elastomer is experimentally characterized, and Finite Element Analysis (FEA) can be used to determine the optimal configurations of these sensor arrays for different sensing needs. To show the feasibility of these SF force sensors, they have been validated for both robotic and human locomotion. For robotic locomotion, a hemispherical design was developed and implemented on the MIT Cheetah, a quadrupedal running robot, as well as on Little HERMES, a bipedal robot. For human locomotion, two prototypes of force sensing shoes have been fabricated based on cylindrical SF force sensors as a proof of concept. In the future, these lightweight, low-cost, multi-axis force sensors can be customized for different applications and fully integrated into smart shoes, prosthetic devices, and robotic exoskeletons to provide the real-time ground reaction force data. This data would enable new capabilities in various fields such as healthcare, sports analytics, virtual reality, and robotics.
by Meng Yee (Michael) Chuah.
Ph. D.
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Moutassem, Zaki M. Moutassem. „A Theoretical and Experimental Analysis of the Density Separation of Non-magnetic Materials with the Use of Imposed Magnetic Fields“. University of Toledo / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1461975382.
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Patranobis, Ranes. „Mathematical investigation of the elastic deformation in dielectric and piezoeletric bodies under the influence of electrical and mechanical fields“. Thesis, University of North Bengal, 1999. http://ir.nbu.ac.in/handle/123456789/1029.
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Vu, My (My H. ). „Peluchi : product development of a programmable robotic toy to stimulate interest in the fields of science and technology amongst young girls“. Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/68863.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2011.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 45).
Statistically speaking, science, technology, and engineering are male dominated fields. Peluchi is a second-generation prototype of a programmable robotic toy targeted towards young girls in hope of promoting more interest in these areas. Peluchi is an educational toy designed to both appeal to girls aesthetically and stimulate them creatively and intellectually. The toy began as a group project for a class called SP. 779: Advance Toy Product Design in the fall of 2009. It existed as a much simpler prototype with a limited set of programmable actions. Since then, the group has continued to develop beta prototype within the course of a semester under the class 2.752: Design of Mechanical Products. Additional work has been done to add complexity and allow more user customization. This is achieved through the addition of modular accessories disguising different servos and sensors that can be plugged into the base unit. The prototype itself was also refined to be more seamless and robust. Analysis and extensive design work were concentrated on the custom ports for the accessories. Finally, manufacturability and marketing strategies were then explored and future plans were considered for the toy.
by My Vu.
S.B.
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Mok, Jin Hong. „Nonthermal Inactivation of Bacteria in Liquids Using a Combination of Mechanical Shear and Moderate Electric Fields“. The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1555609969589384.
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43
Torabi, Soroosh. „TORQUE RESPONSE OF THIN-FILM FERROMAGNETIC PRISMS IN UNIFORM MAGNETIC FIELDS AT MACRO AND MICRO SCALES“. UKnowledge, 2017. http://uknowledge.uky.edu/me_etds/95.
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The non-contact nature of magnetic actuation makes it useful in a variety of microscale applications, from microfluidics and lab-on-a-chip devices to classical MEMS or even microrobotics. Ferromagnetic materials like nickel are particularly attractive, because they can be easily deposited and patterned using traditional lithography-based microscale fabrication methods. However, the response of ferromagnetic materials in a magnetic field can be difficult to predict. When placed in a magnetic field, high magnetization is induced in these ferromagnetic materials, which in turn generates force and/or torque on the ferromagnetic bodies. The magnitude and direction of these forces are highly dependent on the type of material used, the volume and aspect ratio of the ferromagnetic material, as well as the spatial distribution and magnitude of the magnetic field. It is important to understand these complex interactions in order to optimize force and torque generated, particularly given common limitations found in microfabrication, where it is often challenging to deposit large volumes of ferromagnetic material using conventional microdeposition methods, and power availability is also often limited, which in turn limits the ability to generate strong electromagnetic fields for actuation.
This work represents a theoretical analysis and experimental validation in macro scale to determine best practices when designing ferromagnetic actuators for microscale applications. Specifically, the use of nickel thin film prisms actuated in spatially uniform electromagnetic fields. These constraints were chosen because uniform magnetic fields can be readily generated with a simple and inexpensive Helmholtz coil design, and the uniformity makes actuation force independent of location, minimizing the need for spatial precision in devices. Nickel can also be easily deposited using evaporation or sputtering, generally in forms of thin-films.
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Simon, Hélène A. „Influence of the implant location on the hinge and leakage flow fields through bileaflet mechanical heart valves“. Available online, Georgia Institute of Technology, 2004:, 2003. http://etd.gatech.edu/theses/available/etd-04012004-192539/unrestricted/helene%5Fsimon%5Fa%5F200405%5Fmast.pdf.
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Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2003.Sambanis Athanassios, Committee Member ; Sotiropoulos Fotis, Committee Member ; Yoganathan Ajit, Committee Chair. Includes bibliographical references (leaves 239-243).
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Simon, Helene A. „Influence of the implant location on the hinge and leakage flow fields through bileaflet mechanical heart valves“. Thesis, Available online, Georgia Institute of Technology, 2004:, 2004. http://etd.gatech.edu/theses/available/etd-04012004-192539/.
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Thesis (M.S.)--Chemical Engineering, Georgia Institute of Technology, 2004.Sambanis Athanassios, Committee Member ; Sotiropoulos Fotis, Committee Member ; Yoganathan Ajit, Committee Chair. Includes bibliographical references (leaves 239-243).
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Williams, Justin A. „Analytical and Experimental Investigation of Time-Variant Acceleration Fields“. Wright State University / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=wright1567258549794284.
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Ayhan, Aytunc. „Online Critical Game Flow And Role Assignment Based On Potential Fields“. Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605708/index.pdf.
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This thesis describes the critical game flow and dynamic role assignment based on potential fields in robot soccer game and actions taken depending on role assignment. Role assignment is a standard problem of multi-agent game system like robot soccer and it can be realized by many techniques. In this thesis, game flow is described dynamically in terms of critical zones which is formed by potential fields based on the field environment as hills and valleys.
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Colombano, Sosa Martin F. „High precision measurements of magnetic fields and synchronization in optomechanical cavities“. Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670454.
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Els dispositius basats en ressonadors mecànics són un dels més fonamentals i omnipresents sistemes físics a totes les escales. Juguen un paper fonamental en el processament de senyals de ràdio i en sensors de magnituds físiques. En les últimes dècades, s'han realitzat esforços en investigar diferents possibles maneres de manipular, acoblar i llegir el moviment del ressonador. A escala micro i nanomètrica, el primer intent tecnològic va ser acoblar els ressonadors mecànics amb circuits elèctrics. Recentment, s'ha investigat l'ús de radiació electromagnètica per controlar la mecànica. Aquest camp, anomenat Optomecànica, ha estat útil per investigar problemes com el comportament quàntic d'objectes massius o experiments relacionats amb informació quàntica. Molts d'aquests experiments requereixen que el ressonador mecànic es trobi en el seu estat de més baixa energia, conegut com a estat fonamental. Aquest estat només accessible a temperatures criogèniques, i suposen un esforç extra en l'àmbit tecnològic i dificultat. L'objectiu de la meva tesi és desvetllar altres aspectes importants que sorgeixen a conseqüència d'acoblar llum a objectes mecànics sense necessitar que el ressonador operi a l'estat fonamental. En particular, discutiré dos experiments realitzats a temperatura ambient i enfocats a aplicar l'optomecànica a desafiaments tecnològics. El primer experiment està relacionat amb l'habilitat dels sistemes optomecànics per detectar petites forces aplicades sobre ressonadors mecànics. En l'experiment, fem servir una esfera optomecànica de mida micromètrica com a sensor de forces induïdes per camps magnètics ultrabaixos. La força és produïda per un fenomen ressonant que involucra magnons i fonons en un material ferromagnètic. El mínim camp magnètic capaç de ser detectat és de 850 picoTesla amb una amplada de banda de 100 kHz. A més, la capacitat de sintonitzar la resposta en freqüència del magnetòmetre ofereix la possibilitat de detectar camps magnètics en un rang dinàmic de fins a 1.1 GHz. Aquest dispositiu suposa una prova de concepte que obre un nou ventall de possibilitats de desenvolupar magnetòmetres optomecànics d'ultra alta sensibilitat, la qual cosa és crucial en múltiples àrees com la geologia, sistemes d'imatges mèdica, o defensa. El segon experiment que es discuteix en aquesta tesi descriu un desafiament fonamental en la física de nanoescala, com ho és la sincronització de vidres optomecànicas connectades per un acoblament feble de tipus mecànic. Vam demostrar que explotant la interacció mecànica i les propietats no lineals de la llum, podem modificar estratègicament l'estat dinàmic dels oscil·ladors. Observem que els vidres optomecànics acaben oscil·lant individualment en un estat coherent, d'alta amplitud i autosostinguda. També vam demostrar experimentalment que el sistema evoluciona a un règim on els dos oscil·ladors acaben sincronitzats en oposició de fase. Els resultats d'aquests experiments podrien crear un precedent per establir un sistema de comunicacions de poc soroll entre sistemes optomecànics.Los dispositivos basados en resonadores mecánicos son uno de los más fundamentales e omnipresentes sistemas físicos a todas las escalas. Juegan un papel fundamental en el procesamiento de señales de radio y en sensores de magnitudes físicas. En las últimas décadas, se han realizado esfuerzos en investigar distintas posibles maneras de manipular, acoplar y leer el movimiento del resonador. A escala micro y nanométrica, la primera intento tecnológico fue acoplar las resonadores mecánicos con circuitos eléctricos. Recientemente, se ha investigado el uso de radiación electromagnética para controlar la mecánica. Este campo, llamado Optomecánica, ha sido útil para investigar problemas como el comportamiento cuántico de objetos masivos o experimentos relacionados con información cuántica. Muchos de estos experimentos requieren que el resonador mecánico se encuentre en su estado de más baja energía, conocido como estado fundamental. Este estado solo es accesible a temperaturas criogénicas, y suponen un esfuerzo extra a nivel tecnológico y dificultad. El objetivo de mi tesis es desvelar otros aspectos importantes que surgen a consecuencia de acoplar luz a objetos mecánicos sin necesitar que el resonador opere en el estado fundamental. En particular, discutiré dos experimentos realizados a temperatura ambiente y enfocados en aplicar la optomecánica a desafíos tecnológicos. El primer experimento está relacionado con la habilidad de los sistemas optomecánicos para detectar pequeñas fuerzas aplicadas sobre resonadores mecánicos. En el experimento, usamos una esfera optomecánica de tamaño micrométrico como sensor de fuerzas inducidas por campos magnéticos ultra-bajos. La fuerza es producida por un fenómeno resonante que involucra magnones y fonones en un material ferromagnético. El mínimo campo magnético capaz de ser detectado es de 850 pico-Tesla con un ancho de banda de 100 kHz. Además, la capacidad de sintonizar la respuesta en frecuencia del magnetómetro ofrece la posibilidad de detectar campos magnéticos en un rango dinámico de hasta 1.1 GHz. Este dispositivo supone una prueba de concepto que abre un nuevo abanico de posibilidades de desarrollar magnetómetros optomecánicos de ultra alta sensibilidad, lo cual es crucial en múltiples áreas como la geología, sistemas de imágenes médica, o defensa. El segundo experimento que se discute en esta tesis describe un desafío fundamental en la física de nanoescala, como lo es la sincronización de cristales optomecánicas conectadas por un acoplamiento débil de tipo mecánico. Demostramos que explotando la interacción mecánica y las propiedades no lineales de la luz, podemos modificar estratégicamente el estado dinámico de los osciladores. Observamos que los cristales optomecánicos terminan oscilando individualmente en un estado coherente, de alta amplitud y auto-sostenida. También demostramos experimentalmente que el sistema evoluciona a un régimen donde los dos osciladores terminan sincronizados en oposición de fase. Los resultados de estos experimentos podrían sentar un precedente para establecer un sistema de comunicaciones de poco ruido entre sistemas optomecánicos.
Mechanical resonators are one of the most fundamental and omnipresent physical systems at all scales. They play a substantial role in radio-signal processing and sensing. In the last decades, efforts have been made toward the investigation of different approaches to control, to couple, and to read out their motion. At the micrometre- and nanometre-scale, the first approach that emerged was to couple mechanical structures to electrical circuits. More recently, researchers have investigated the use of electromagnetic radiation to control and probe mechanical elements. This field, called Optomechanics, has been used to explore fundamental physics problems like testing quantum mechanics on heavy mass structures or for quantum information processing. Many of these experiments require the mechanical resonator at the ground state of motion, but this can only happen at extremely low temperatures and under very specific conditions. My thesis aim is to unravel other important aspects of coupling light to mechanical objects that do not require to operate at the ground state. In particular, I will discuss two experiments performed at room temperature focused on applying optomechanics to technological challenges. The first experiment is related to the ability of optomechanical systems to detect small forces applied to a mechanical resonator. We employ a microsphere optomechanical sensor to detect the force induced by an extremely small magnetic field. The force is produced by a resonant phenomena that involve magnons and phonons on ferromagnetic material. The magnetic field sensor is characterized by a pico-Tesla peak sensitivity with a bandwidth of 100 kHz. Also, the tunability of the frequency response rises the device frequency operation up to a dynamical range of 1.1 GHz. This device is a proof of concept that opens a window to develop ultra-high sensitive optomechanical magnetometers, which is crucial in many areas covering geology, medical imaging systems, or defense. The second experiment of this thesis describes a fundamental challenge of nanoscale physics that is the synchronization of two optomechanical cavities connected by a weak coupling. We show that exploiting the interaction between the mechanical elements and the nonlinearity of the light field, we can strategically modify the dynamical state of the oscillators. We show that the nanobeams are individually oscillating in a coherent, high amplitude and sustained state. We also experimentally demonstrate that the system evolves to a regime where the two oscillators are fully synchronized in anti-phase. The results of this experiment could be setting a base for low-noise communications between optomechanical devices.
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Green, Adam. „Structure and Dynamics of Two Flow Fields Used for Particle Deposition onto and Removal from a Substrate“. ScholarWorks @ UVM, 2016. http://scholarworks.uvm.edu/graddis/554.
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A series of experimental studies was performed to investigate two separate fluid impingement flow systems intended for removal of particles from a surface or deposition of particles onto a surface. One of these flow systems is generated using a nozzle that incorporates both tilted jets and suction to create what we call a "bounded vortex flow", consisting of an annular swirling jet and a wall-normal vortex with axial upflow into a suction outlet. The other flow system is generated by a combination of acoustic streaming and substrate heating from an ultrasonic source. The primary methods used in the study for flow field measurements included laser-induced fluorescence (LIF) and particle-image velocimetry (PIV). Thermocouples are utilized for gathering temperature information from the ultrasonic induced flow. For the bounded vortex flow, different jet/suction flow rates and different nozzle-substrate separation distances were examined. In the acoustic-generated flow system, different acoustic intensities and transducer-substrate separation distances and different choices of substrate material were examined. Both flow systems achieve high levels of shear stress on the impingement surface via a combination of flow oriented toward and/or away from the surface and via formation of vortex structures near the impingement surface. In the bounded flow configuration, the vortex flow is oriented with axis normal to the impingement surface, whereas in the acoustic-generated flow a series of vortex rings form with axes parallel to the impingement surface. For both flow fields, conditions are observed with high impingement surface shear stress that are well suited to particle removal from the impingement surface. However, as the variables controlling the flows are varied, other conditions are observed in which the flow fields become unstable, leading to oscillatory flows that generally have much smaller shear stress values on the impingement surface. The rate of fluid mixing, as characterized by upward and downward flows normal to the impingement surface, is also generally decreased after these flow transitions have occurred, implying that the unstable flows will be less suited for both particle deposition on and particle removal from the impingement surface.
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Sequin, Emily Katherine. „Effects of Induced Electric Fields on Tissues and Cells“. The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1403869854.
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