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 49 for “"higher-order modes"”.
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Higher Order Trapped Lee Waves in the Stratosphere
… Wallington (1956) have posited the existence of higher-order trapped wave modes. Although the higher-order modes in these studies were confined to the troposphere due to the studies’ theoretical setup, Corby and Wallington (1956) demonstrate that the level of maximum amplitude for higher-order …
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Application of the Herschel-Quincke Tube Concept to Higher-Order Acoustic Modes in Two-Dimensional Ducts
… the potential of the HQ tube concept to control higher-order duct modes. This analytical method involves modeling the tube-duct interfaces as finite piston sources, which couple the acoustic field inside the main duct with the acoustic field within the HQ tube(s). The acoustic field within the HQ …
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Miter bend loss and higher order mode content measurements in overmoded millimeter-wave transmission lines
… lines have not considered beam polarization or higher order mode effects. This thesis will develop a theory of transmission that includes the effect of linearly polarized higher order modes on power loss in overmoded corrugated transmission line systems. This thesis derives the linearly …
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An optimized dual-polarized quad-ridges horn antenna with pyramidal sidewalls
… is severely restricted due to the excitation of higher order modes in the co-axial to waveguide transition of the antenna. The higher order modes cause a break-up in the radiation pattern of the antenna and large dips in the boresight gain. The performance of the quad-ridged horn antenna with …
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Optofluidic Microreactors for Advanced Photocatalysis
… are applied to excite a wide variety of higher-order modes with well-defined cross-sectional intensity distributions inside the HC-PCF’s core. An automated fast-switching between inverted higher-order modes can in the future be exploited to enable pump-probe and diffusion/ adhesion …
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Conductive cylindrical surface waveguides
… surface waveguides guide a pure low-order mode with no cutoff frequency and low distortion, while higher-order modes are quickly attenuated. In this work, we develop simulations and conduct experiments to design a large-radius surface waveguide which can be measured with existing lab …
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High power high efficiency multiple-beam klystron design
… Existing methods of calculating dipole and higher order modes proved time consuming thus impeded a fully investigation of stability issues. An extended method of moments model allows efficient calculation of monopole and higher order modes. The model’s basis functions are altered to …
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Investigation of the Herschel-Quincke tube concept in a rectangular lined duct
In this research an innovative combination of the Herschel-Quincke tubes and traditional liners is proposed for application in noise reduction of aircraft engines. The approach consists of installing Herschel-Quincke (HQ) tubes on lined rectangular ducts. An analytical model was developed to …
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Experimental studies of multipass beam breakup and energy recovery using the CEBAF injector linac
… due to the potentially high Q of the cavity higher-order modes (HOMs). The CEBAF accelerator, which employs five pass recirculation through two superconducting linacs to accelerate high CW current (up to 200 $\mu$A), poses unique instability problems. An experimental investigation of …
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Analysis of Side-Polished Few-Mode Optical Fiber
… of fiber optic devices. To do this, specific modes are excited in the polished fiber using a phase-only spatial light modulator to determine spatial mode distribution. Each mode is excited and compared to the expected field distribution and to confirm that higher order modes can propagate …
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Investigation of the Herschel-Quincke Tube Concept as a Noise Control Device for Turbofan Engines
… that some energy is also scattered into other higher-order modes. Thus, the suppression of a particular mode is due to the combination of the scattered contributions from the various incident modes. The effects of the system parameters were analyzed and parametric studies were conducted. …
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Triple band dipole antenna with harmonic suppression capability
… easy to be designed and fabricated. However, higher order modes (HOM) in these multiband antennas gives problems when designing such type of antennas. The proposed antenna consists of two designs; the first design is triple band dipole antenna with harmonic suppression capability which …
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Designing the four rod crab cavity for the high-luminosity LHC upgrade
… were performed to ensure that multipacting and higher order modes were at tolerable levels. Design considerations were made to ensure a niobium prototype could be constructed for cold testing, the results of which are presented along with discussion of future plans for continuing to further the …
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Symmetry Breaking and the Inverse Energy Cascade in a Plasma
… a new equilibrium characterized by amplified low order modes and diminished amplitude of higher order modes. Although the turbulent spectrum changes, the RMS fluctuation level is unchanged by the bias. Bias also causes the turbulent electrostatic fluctuations to coalesce into a quasi-coherent mode …
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Fundamental Studies of the Herschel-Quinke Tube Concept with Mode Measurements
… HQ-waveguides in a duct in the presence of higher order modes. However, the practical nature of these engine facilities results in limitations with regard to the fundamental research knowledge that could be gained from testing in a more controlled laboratory environment. A series of …
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Development of harmonic suppressed reconfigurable fractal dipole antenna
… Nevertheless, it can potentially have higher gain and higher efficiency with the use of a low loss Rogers RT/Duroid material. Thus, the study on the reduction of the tapered balun size is worthwhile. Four sets of wideband tapered baluns with reduced sizes have been designed and tested …
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Dual band dipole antenna with harmonic suppression capability
… easy to be designed and fabricated. However, higher order modes (HOM) in these multiband antennas gives problems when designing such type of antennas. The proposed antenna consists of two designs; first design is building single parasitic element which generates 0.8 GHz, 2.4 GHz and 4 GHz; …
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Mode conversation losses in overmolded millimeter wave transmission lines
… in the gap. We also considered the problem of higher order modes (HOMs) mixed with an HE11 input entering the miter bend. Using a numerical technique, we found that the loss through the miter bend is dependent on both the amplitude of the HOM content as well as its phase relative to the phase …
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Body and surface wave ambient noise seismic interferometry across the Salton Sea Geothermal Field, California
… contained strong surface waves at 0.4-2.5 Hz, an order of magnitude below the corner frequency of the geophones, and modest body waves at 22-30 Hz, which are generally more difficult to obtain due to the need for many large, well-distributed subsurface sources. The virtual source gathers compare …
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Microwave Properties of Helical Resonators
… particular emphasis on the relatively unexplored higher-order modes. By systematically varying geometric parameters, especially pitch, this study reveals unique properties that emerge at many modes, as well as showing transition toward axial field characteristics as mode number is increased. The …
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