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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 29 for “"farfield"”.
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Development and Initial Evaluation of an Acoustic Apparatus Used For Testing of Farfield Noise Emitted by a Propeller in a Short Duct
<p>The purpose of this thesis was to design, construct and evaluate an apparatus which was used for testing of acoustic emissions by a propeller in a short duct. An apparatus was designed based on a combination of acoustic principles and a desire to be able apply the knowledge gained to a practical …
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Directive antenna using metamaterial substrates
… waveguide, and the other is parallel plate slab farfield radiation. The S-parameters are obtained from the wave-guide simulation and are used to retrieve the effective permittivity and permeability with which we can estimate the farfield radiation using analytic method. Thus, by comparing the …
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Acoustical behavior of a turbulent, ducted, premixed, hydrogen- flame burner
The acoustic source structure, acoustic farfield, and duct terminating impedances fully describe the acoustics of a source within a duct. A main goal in the study of noise generated by turbulent combustion is to characterize the structure of the flame as an acoustic source. Data describing the …
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Analysis and Measurement of Horn Antennas for CMB Experiments
… using mode matching techniques to model their farfield beam patterns. To undertake this analysis the existing in-house software was upgraded to address issues associated with the stability of the simulations and to introduce additional functionality through the application of Single Value …
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Numerical Simulation of Injection and Mixing in Supersonic Flow
… solution was significantly under-resolved in the farfield, though the quality was better in the vicinity of the injector itself. The ramp-injector solution, while not perfectly grid-resolved, showed much better grid convergence in both the nearfield and farfield. Accordingly, comparison with …
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Unsteady aerodynamics using high-order methods
… relation of the L/D to the radiated sound in the farfield is sought. It is found that the nature of the flow interaction with the downstream corner, which changes with L/D, dictates the directivity and amplitude of the sound field observed at a far distance from the source. To gain more insight …
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Comparison of the aeroacoustics of two small-scale supersonic inlets
… of the aerodynamic flowfield and acoustic farfield were made in order to evaluate the aeroacoustic performance of the inlets. The aerodynamic results show the total pressure recovery of the two inlets to be nearly identical, 99% at the approach condition and 98% at the takeoff condition. At …
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Exploring Passive Flow Control Techniques Applied to a Supersonic Multistream Rectangular Nozzle
… pressure and velocity in conjunction with farfield acoustics. Farfield acoustic measurements have confirmed the diminishment of the tone for the wavy SPTE. PIV and velocity profiles for mean fields revealed higher plume vectoring for the nominal aft-deck. The shear layers and the region …
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An Investigation of Active Tonal Spectrum Control as Applied to the Modern Trumpet
… of controllers are designed and realized. The farfield spectrum of the trumpet's response to a single note is analyzed for each controller and the resulting attenuations compared. The model of the trumpet system is then used to demonstrate the coupling of the trumpet and the player and to show …
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Nodal photolithography : lithography via far-field optical nodes in the resist
… of optical lithography. This approach uses farfield optical nodes to orchestrate reversible, saturable optical transitions in certain photoresist compounds. After addressing prior work in resolution enhancement via optical nodes (for metastable atom localization, reversible absorbance …
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Sound scattering by cylinders of noncircular cross section
… investigates a new method for predicting the farfield scattered pressure of a plane wave due to an infinite cylinder of noncircular cross section. Both impenetrable and penetrable :fluid boundary condi tions will be treated for several types of cross sections and for a large frequency range. …
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An Analysis of Using CFD in Conceptual Aircraft Design
… to use in the conceptual design stage. A farfield method was derived and used in this analysis to calculate the lift and drag coefficients. The CFD solutions were also compared with two methods currently used in conceptual design - the vortex lattice based program Vorview and ACSYNT. The …
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Projection of acoustic fields using the Fourier transform
… These are circumvented by observing that the farfield pressure pattern can be found by simply taking the Fourier transform of the nearfield pressure distribution. A rectangular source is simulated on the computer; the Fourier transform technique of projecting fields is compared to a direct …
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Harnessing Solid-State Ionic Transport for Nanomanufacturing and Nanodevices
… of an adsorbate. New insight into whether farfield scattering of such structures or the nearfield EM-field is more important to the enhancement to Raman scattering was gained from comparing the experimental results with the numerical one. A systematic way of characterizing the …
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Neural network estimation of disturbance growth and flow field structure of spatially excited jets
… of identifying both nearfield and quasi-farfield flow structures of a jet undergoing spatial mode excitation. The evolution of disturbances introduced by a spatially excited jet spans a linear and nonlinear regime in the downstream flow field. For the linear portion, the neural network …
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Periodic subwavelength photonic structures
… the mid-field light pattern as opposed to the farfield, the entire spectrometer can fit within a 10 mm by 10 mm by 5 mm volume. The second application are barcodes based on the wavelength-dependent back-scattering off of a photonic crystal resonant cavity. The challenge is that we want to …
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Computational analysis of planar wings designed for optimum span-load
… close to the wing surface and pyramids in the farfield region. Simulations were carried out in both steady state and semi-transient states to predict ow transition. A comparative study of different turbulence models revealed k-omega-SST and k - kL-omega to be the most suitable turbulence models …
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Unstructured grid technologies for hydrodynamic applications with bodies in relative motion and mesh deformation
… no relative motion between the cylinder and the farfield), and the solutions agree with each other very well. Then interaction between two oscillating cylinders with same amplitude and frequency but 180-degree phase difference is studied. It is found that significant low pressure is generated …
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Das Intrathorakale EKG im implantierbaren Cardioverter/Defibrillator : Erweiterung der EKG-Diagnostik in implantierbaren Systemen
… wurden während ICD-Implantation die sechs farfield-Elektrogramme des IEKG von den Defibrillationselektroden eines ICD abgeleitet und mit dem Oberflächen-EKG und den lokalen Elektrogrammen verglichen. <br>Das IEKG bildet den Erregungsablauf, im Gegensatz zu den lokalen Elektrogrammen, …
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Active control of sound radiation due to subsonic wave scattering from discontinuities on thin elastic beams
… The effect of the control actuators on the farfield radiated pressure, the wavenumber spectrum, the flexural displacement and the near-field time averaged intensity and pressure distributions are studied in order to further understand the control mechanisms. The influence of the near-field …
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