Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"oscillation amplitude"”.
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On fuel selection in controlled auto-ignition engines : the link between intake conditions, chemical kinetics, and stratification
… that is used to approximate the pressure oscillation amplitude is not accurate in the presence of sequential ignition. A modified correlation for the pressure oscillation amplitude has been presented. It was found that the pressure oscillation amplitude can be reduced, at a given pressure …
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Characterization of Onset and Transition to Instability in Supersonic Retropropulsion
… Mach of 3. Shock standoff distance and oscillation amplitude was increased with increasing forebody diameter and increasing freestream Mach number. Carbon Dioxide-Helium cases also exhibited both higher oscillation amplitude and shock standoff distance than corresponding …
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Analysis of inductance-capacitance voltage-controlled oscillators
… oscillators. Fundamentals on LC VCOs, like oscillation conditions, classical LC VCO architectures, inductor and capacitor choices, and phase noise calculations are described. A detailed analysis of the phase noise and oscillation amplitude of double switch cross-coupled oscillators follows. …
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The rotor-oscillator flow : searching for coherence amidst chaos
… For some couplings of the rotor motion with its oscillation, this flow has been shown to have coherent islands of fluid parcels surrounded by a sea of chaos. Through finite-time Lyapunov exponent (FTLE) analysis, a roughly optimal coupling was found. The parameters that describe this coupling are …
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The instability of axial-symmetric gravity-capillary waves generated by a vertically-oscillating sphere
… experiments, however, show that when the oscillation amplitude of the sphere exceeds a threshold value, the axial-symmetric waves abruptly transfigure into asymmetric waves. This problem is related to interfacial instability phenomena widely seen in lab model tests such as sloshing, ship …
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Nonlinear oscillation and control in the BZ chemical reaction.
… model was proposed to study the nonlinear oscillation of the Belousov-Zhabotinsky(BZ) reaction in a closed isothermal chemical system. The reaction zone can be divided into two zones, oscillation zone and transition zone, where the oscillation time and the transition time and the number of …
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Modeling and design of digital current-mode constant on-time control
… regulator module. One issue is the limit cycle oscillation problem caused by the quantization effect from the ADC and DPWM of the digital control chip. Another issue is the delay problem coming from the sample-hold effect. In this thesis, the modeling, analysis and design methodology for the …
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Experimental studies of flapping foils for energy extraction
… of the foil, the non-dimensional excursion amplitude of the foil, and the profile of the foil path during a typical energy extraction cycle. The heave and pitch of the fin was approximated by a NACA 0012 foil heaving and pitching sinusoidially 90° out of phase at a Reynolds number of 13,800. …
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Ultra-low frequency wireless transmitter design using resonant oscillating permanent magnets
… First, I analytically show that the physical oscillation of a permanent magnet creates a time-varying magnetic field that can be used for communication. Using this principle, I present a ULF magneto-mechanical transmitter design that uses an electrically-driven torsional resonator. In the …
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The Structural Response of a Frame-Membrane Lunar Habitat Subjected to Impact and Thermal Loads
… extreme lunar temperatures reduces the dynamic amplitude (compared to cases where the outside temperature is the same as the inside temperature). The internal pressurization is seen to have little effect on the dynamic amplitude and oscillation. The added mass due to the regolith is seen to …
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Marginal oscillator sensitivity enhancement using full-state nonlinear feedback
… feedback applied to maximize the change in amplitude with respect to the circuit's internal resistance. Although used in many applications, the marginal oscillator is most commonly used in continuous wave magnetic resonance (CW-MR). Continuous-wave is useful under two circumstances. The …
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Numerical study of the nonlinear dynamics of the acoustic drops and bubbles
… motions. It is found that the stability of shape oscillations imposes an upper limit on the acoustic bond number that can be used, while the lower limit is set by the stability of translational motion. The static equilibrium shapes can be obtained by incorporating the artificial damping into the …
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Fundamentals of heat transfer and thermal-mechanical control for improved atomic force microscopy
… up to 7X larger Lorentz force and 2X larger oscillation amplitude compared to the state-of-art heated cantilevers. When used for thermal topography imaging, the Lorentz-thermal cantilevers can measure topography with vertical resolution of 0.2 nm.
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Mesoscopic quantum interference experiments in InGaAs and GaAs two-dimensional systems
… yields pronounced Aharonov-Bohm (AB) oscillations with magnetic flux periodicity of h/e over a wide range of magnetic field. The periodicity was confirmed by Fourier transformation of the oscillations. The AB oscillation amplitude shows a quasi-periodic modulation over applied magnetic …
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High magnetic field quantum oscillation study of Fermi surfaces in bulk unconventional insulators
… have been found to display insulating quantum oscillations: YbB12 and FeSb2. YbB12 is an f-electron Kondo insulator, much like SmB6, and exhibits similar electrical and thermal properties to SmB6. On the other hand, FeSb2 is a d-electron insulator that had previously attracted attention for its …
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An Analytical Model for Oscillating Heat Pipe Performance and Experimental Testing of a Novel Helix-Shaped Design
… are difficult to model analytically, such as oscillation amplitude in designs with flooded condensers. Experimental validation of the novel helix-shaped OHP demonstrated that the design generally improved the effective thermal conductivity and maximum heat transport capacity relative to a …
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The two-dimensional vibrating reed technique: a study of anisotropic pinning in high-temperature superconductors
… reed with two degrees of freedom of the oscillation was constructed. The pinning forces were examined in single crystals of YBa2Cu3O7 and Bi2Sr2CaCu2O8. Because of the d waves symmetry of the order parameter is expected four-fold anisotropy of the pinning potential. The reed consists of a …
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Shock oscillation mechanisms of highly separated transitional shock-wave/boundary-layer interactions
… These conditions combined induce a shock oscillation with frequencies approximately matching the blade's natural structural frequencies. This resonance causes excitation and vibrations, which, if not mitigated, can lead to fatigue and potential structural failure. This dissertation …
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Modelling and analysis of vibrations in flexible cylinders subjected to internal multiphase and external single-phase flows.
… of coupled out-of-plane, in-plane and axial oscillations combined with equations involving centrifugal and Coriolis forces for the analysis and prediction of SIV. New dimensionless equations are derived from the dimensional model to analyse key flow features and improve overall understanding …
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An exploration of prominent cusped-field thruster phenomena : the hollow conical plume and anode current bifurcation
… by a steep jump in anode current and current oscillation amplitude, and, somewhat separately, the coalescence of the ion plume into a hollow cone-like structure with peak fluxes around 30 degrees from the thruster axis. This thesis describes the experimental and numerical work undertaken in an …
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