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 24 for “"low frequency range"”.
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Acoustical characteristics of oil palm mesocarp fibres
… absorption coefficient (SAC), especially at low frequency range. The oil palm Mesocarp fibres were mixed with four different percentages of PU, namely 10%, 20%, 30% and 40%. The measurement of SAC was done using an impedance tube method (ITM). Moreover, there were two analytical models which …
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Modelling of low frequency muffler based on acoustic black hole effect
… termination ducts and mufflers working within low frequency range. The functioning of such linings has been associated to the Acoustic Black Hole effect. These structures work on the principle of impedance matching, and in theory, have been realized to achieve total absorption of sound in …
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Development and Comparison of Highly Directional Loudspeakers
… professionals in the audio industry. They allow sound engineers to more easily manipulate the radiation pattern of their loudspeakers to accommodate the purpose of the venue. Many commercially available products, while exhibiting good directivity at mid and high frequencies, generally lack …
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Multiple Wave Scattering and Calculated Effective Stiffness and Wave Properties in Unidirectional Fiber-Reinforced Composites
… and interfacial crack cases are analyzed in the low frequency range. The analytic results show that waves in both cases are attenuated and non-dispersive in the low frequency range. The composites with interfacial layers are transversely isotropic, while composites with interfacial cracks are …
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IMAGING INTERFEROMETRIC MICROSCOPY TO THE LIMITS OF AVAILABLE FREQUENCY SPACE
… systems limit of optics (~lambda/4n). IIM allows one to resolve structures not accessible in a conventional illumination setup, while using a low NA microscope objective and thus keeping the large working distance, depth of focus and field of view associated with the lower NA. The goal of …
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Sonic Crystal Noise Barriers
… noise barrier using an array of periodically arranged vertical cylinders known as a Sonic Crystal (SC) is investigated. As a result of multiple (Bragg) scattering, SCs exhibit a selective sound attenuation in frequency bands called band gaps or stop bands related to the spacing and size of the …
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Acoustical characterization and parameter optimization of polymeric noise control materials
… matrix and by integrating design solution in the low frequency range. A suggested numerical approach is described for STL evaluation of simple and complex geometries. In practice, validation on actual vehicle systems proved the adequacy of the acoustical characterization process.
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Structure-acoustic analysis; finite element modelling and reduction methods
… This type of analysis is applicable to a wide range of engineering problems, for example, studying the interior noise in a vehicle or the sound transmission loss in a wall between two dwellings. The geometrical properties of the studied system and the frequency limit of interest for the …
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INFORMATION TRANSFER EFFICIENCY OF X-RAY IMAGE INTENSIFIER-BASED IMAGING SYSTEMS.
… is a function of the statistically independent frequency channels. The DQE(f) is a combined descriptor which takes into account the signal transfer as well as noise transfer properties of a complete system. For a complicated multistage imaging system, each system component contributes noise. In …
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Feedforward control of binary distillation
… control for binary distillation columns in the low frequency range (below a frequency of 1.6 radians per dimensionless time -- dimensionless time is defined to be the tray holdup divided by the stripping section liquid rate). The experimental data were determined for the benzene-n-heptane system …
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Finite element modeling of a refrigeration compressor for noise prediction applications
… are found for the compressor housing in the low frequency range (below 2000 Hz) of analysis. Forced response calculations are also used to correlate the analytical model and test data, with a maximum of 5% disagreement for the 14 natural frequencies that could be correlated. Compressor …
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Single wall carbon nanotubes as viscosity modifiers in polypropylene matrix nanocomposites
… wall carbon nanotubes (SWNTs) were studied as low shear rate viscosity modifiers in the polypropylene matrix of nanocomposites. To create nanocomposites which did not demonstrate increased low shear rate viscosity when nanotubes were added into the polymer melt, this work focused on modifying …
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Extraction methods for multidirectional driving point accelerance and transfer point accelerance matrices
… The noise error appears to be most severe in the low frequency range. The exciter rocking motion leads to incorrect bare vehicle transmissibility matrix and incorrect global transmissibility matrix. The driving point difference error increases quickly as the distance between the impact and …
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MEG coherence imaging in dyslexia: Activation of working memory pathways
… temporal gyrus). Further, dyslexics showed lower normalized amplitudes of activation in the right superior temporal gyrus and right middle temporal gyrus than controls during a spatial working memory (SWM) task. In contrast, during a verbal working memory (VWM) task, dyslexics showed lower …
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Low frequency ac transmission for power systems
… not flexible for multi-terminal connection. The low frequency ac (LFAC) transmission system, first introduced in 2000, is another solution for bulk power transmission that inherits advantages from both high voltage ac and high voltage dc systems. The primary advantage of LFAC transmission is that …
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Development of polymer based nanocomposite using electrospinning for sound absorption and isolation
… the solution concentration, the solution flow rate, the high voltage used for generating an electric field, the distance over which the fibers were collected, and the speed of the rotating drum on which the fibers were collected. Statistical analysis and multiple regression techniques were …
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The Design and Analysis of Bluff Body Dynamic Distortion Generators
… in aircraft comes an increase in secondary flows and large pressure gradients which decrease engine efficiency. Therefore, in order to assess new engine technology, a way to generate these unsteady flows in ground test facilities needs to be developed. StreamVanes and ScreenVanes were …
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The complex interplay between AGN jet feedback and galaxy evolution
… of SMBH jet feedback at earlier times, lower luminosities and with higher spatial and spectral resolution. Additionally, the LISA mission will expand the field of multimessenger astronomy to the low-frequency range, detecting gravitational waves from the coalescence of SMBHs all the way …
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Fabrication of reliable, self-biased and nonlinear magnetoelectric composites and their applications
… consisted of a Metglas/PMN-PT laminate and a low noise charge amplifier, had a magnetic field sensitivity of 10 pT/Hz0.5 in a well-shielded environment. Stacking four of these ME laminates could further increase the signal-to-noise (SNR) ratio. I studied the optimized distance between a pair …
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Numerical modeling of cortical bone adaptation due to mechanical loading using the finite element method
… mechanical loading parameters such as magnitude, frequency, number of bouts etc. of applied loading through experimental studies. We propose to develop a numerical framework, which can simulate and predict cortical bone adaptation due to diff erent parameters of loading. In pursuit of the …
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