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.
Results
Showing 1 to 20 of 26 for “"frequency mode"”.
-
Global stability and control of swirling jets and flames
… and the most unstable direct and adjoint global modes. These are combined, using a structural sensitivity framework, to identify the region of the flow and the feedback mechanisms that are responsible for causing the global instability. Using a Lagrangian framework, the direct and adjoint global …
-
Unsteady modes in the flowfield about an airfoil with a leading-edge horn-ice shape
An analysis of unsteady modes present in the flowfield of an airfoil with a leading-edge horn-ice shape was performed in the current study. An NACA 0012 airfoil was tested in a subsonic wind tunnel at Re = 1.8 × 106. In addition to the clean configuration, the airfoil model was also tested with a …
-
Nonlinear Vibrations of Cantilever Beams and Plates
… on the transfer of energy between widely spaced modes via modulation. This phenomenon is studied both in the presence and absence of a one-to-one internal resonance. Reduced-order models using Galerkin discretization are also developed to predict experimentally observed motions. A good …
-
Nonlinear dynamics of systems involving widely spaced frequencies
… The beam is excited near its fifth natural frequency but sustained large-amplitude oscillations of the first mode accompanied by modulated oscillations of the fifth mode occur. Thus, energy is transferred from the fifth to the first mode of the beam, whose natural frequencies are roughly in …
-
Nonlinear vibration of beam and multibeam systems
… we present experimental results regarding multimode behavior. The beam was tested in both a vertical and horizontal configuration. Our experiments show that. for a forcing frequency near the fourth natural frequency of the beam, a low-frequency mode can be activated through a nonlinear …
-
Active Control of Coherent Structures in an Axisymmetric Jet
… this work is to develop high-fidelity simulation model for jet noise control predictions and quantify the sound reduction when an external source frequency mode excitation is imposed on the jet flow. Whereas passive approaches using mixing devices, such as chevrons, have been shown to reduce …
-
Some design consideration of switching regulator using current-injected control
… regulator is performed using a small signal model containing a power stage, an error processor and a duty cycle pulse modulator. Two design constraints and the effects of various critical control circuit parameters are pinpointed and the analysis-based design guidelines are established in …
-
An investigation of the effect of a tangential gas velocity on combustion instability.
… counterclockwise at various angles or a straight mode of operation. Runs were made at various flow rates with the direction of swirl changed during the run. A first tangential high frequency mode of combustion instability was developed and a significant change in stability conditions was found …
-
Thermoacoustic Oscillations in Supercritical Fluid Flows
… by blowing 800-950F nitrogen over them. Acoustic-mode oscillations, typically ranging from 100-500 Hz, occurred only when a large temperature gradient was created inside the heated fuel tubes. Pressure oscillation amplitudes ranged from 0.1-1.0 psi. Oscillations at the inlet and outlet manifolds …
-
An acousto-ultrasonic system for the evaluation of composite materials
… plates, the identification of specific frequency peaks, and the relationships these may have to certain modes of vibration and material properties. For example, a low frequency mode was found to vary in a manner reminiscent of E<sub>x</sub> and to show characteristics of an extensional …
-
Optimizing feeder bus network based on access mode shifts
… user and supplier costs. Three major access modes (walk, feeder bus, and auto) for the rail station are considered and the cost for all modes makes up the user cost. The supplier cost comes from the operating cost of the feeder bus network. The decision variables include the structure of the …
-
Piezoelectric MEMS for Energy Conversion in Biomedical Devices
… source. The first half of this work introduces a frequency comb-vibrational energy harvester, designed and characterized to function under a broadband and random vibration source. The frequency comb phenomenon is traditionally studied in the optical domain for applications in timing and …
-
Dynamics and mechanism of spin-state interconversion in transition metal complexes. (Volumes I and II)
… reaction coordinate. The importance of torsional modes in controlling the kinetics of $\rm\sp5T\sb2$ $\to$ $\rm\sp1A\sb1$ relaxation is further supported by theoretical analyses. Fitting of variable-temperature kinetic data to classical, semi-classical, and quantum-mechanical theories of electron …
-
Online Electromagnetic Wave Monitoring System for Petroleum Industry Applications
… non intrusive sensor, the choice of resonance mode to achieve the best measurement accuracy, and the possibility of designing a new software application to allow online implementation of the sensors. The first principle is shown to allow sensorswith completely non intrusive structures to be …
-
Argon Bubble Behavior in Slide-Gate Tundish Nozzles During Continuous Casting of Steel Slabs
… and mold. The current work combines mathematical modeling and experiments to investigate the argon bubble behavior in slide-gate nozzles and to analyze phenomena related to product defects and operational problems during the continuous casting of steel slabs. Water model experiments are performed …
-
Spatially Resolved Analysis of Flame Dynamics for the Prediction of Thermoacoustic Combustion Instabilities
… flame behaves as a low-pass filter, with cutoff frequency on the order of hundreds of hertz. Nondimensionalization of the frequency by flame length scales has been observed to result in a convenient scaling for the flame transfer function, suggesting that the flame dynamics may be dominated by …
-
Improved Polyhydroxyalkanoate Production from Selected Volatile Fatty Acids using Cupriavidus necator
… PHA off-line measurements when operated in dual frequency mode and was able to establish the optimum PHA harvesting time, which would have resulted in improved process economics and environmental performance.<br/><br/>Shake flask experiments were conducted to investigate the addition of trace …
-
Probing Solvation Shell Dynamics of Organometallic Complexes via Two-Dimensional Infrared Spectroscopy
… spectroscopy shows the fundamental vibrational modes of a complex, yielding a spectrum that acts as a molecular fingerprint that allows for identification of chemical species and functional groups within a system. The one-dimensional nature of FTIR spectroscopy, however, occludes broadening …
-
Development of stainless cardiac histology of clinical biopsy samples with infrared spectroscopy
… by using quantum cascade laser-based discrete frequency infrared (DFIR) imaging instruments. In the second part of this work, we analyzed data collected on recently developed discrete frequency instruments and compared it to data collected on FT-IR imaging instruments. This was done by …
-
Problems in nonlinear dynamics
… approach to determine the nonlinear normal modes of weakly nonlinear discrete systems with one-to-one and three-to-one internal resonances. Cubic geometric nonlinearities are considered. The system under investigation possesses similar nonlinear normal modes for the case of One-to-one …
Page 1 of 2