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 20 for “"Bragg scattering"”.
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Effects of interaction in Bose-Einstein condensates
… effects of interaction - essentially the s-wave scattering - in the various properties of Bose-Einstein condensates (BEC). The phonon wavefunction in a BEC was measured using Bragg spectroscopy and compared with the well-known Bogoliubov theory. Phonons were first excited in a BEC of 3 x 107 …
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A revised conceptual model of the tropical marine boundary layer
… and validation of a new radar product based on Bragg scattering retrievals from clear air S-band radar returns, a re-conceptualization of the tropical marine boundary layer based on this new radar product, and supplemental analysis of other data from this environment. The running theme …
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Diffuse X-ray scattering from tropomyosin crystals
… in the crystal which profoundly affect the X-ray scattering are important. All motions in the crystal affect the Bragg scattering and also give rise to diffuse scattering between and surrounding the Bragg spots. The diffuse X-ray scattering may comprise a large part of the total scattering from …
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Multimode Microresonator Optical Frequency Combs
… with multiple independent lasers to observe the scattering of a probe field from a soliton frequency comb, as well as study the excitation and control of multiple soliton combs in a single resonator. First, we consider the co-propagation of two driving lasers in the same spatial mode of a Kerr …
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Determination of Bragg Scatter in an Aircraft Generated Wake Vortex System for Radar Detection
… that yields this radar cross section is Bragg scattering from the index of refraction variations due to the atmospheric water vapor and potential temperature fields being mixed by the wake vortex system. Refractive index variations of the size that correspond to half the operating radar …
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Generation of sand ripples and sand bars by surface waves
… mutual influence of the waves and bars through Bragg resonance. In Chapter 2, we first give an analysis of the effects of shoreline reflection on Bragg resonance by considering rigid bars, aiming at acquiring a deeper understanding of the physical processes of the Bragg resonance mechanism. We …
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Acoustic Metamaterials at the Microscale
… at these scales. Dispersion resulting from Bragg scattering occurs at wavelengths which are dictated by the characteristic dimensions of the metamaterials, while local resonance remains wavelength-independent. Therefore, micro-architected materials have the potential to allow control of …
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Spin-orbit coupled Bose-Einstein condensates with observation of a stripe phase
… of a lattice supersolid which we detected with Bragg scattering. Finally, the density modulation of the stripe phase is measured with a Bragg reflected beam and a camera setup to resolve the angular spread of the beam. An angle resolved, coherent Bragg beam is direct evidence of the stripe phase …
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Manipulating Bose-Einstein condensates with laser light
… Spontaneous and stimulated off-resonant light scatterings were studied experimentally. Stimulated, two-photon Bragg scattering was used for spectroscopic measurement of the mean-field energy and of the intrinsic momentum uncertainty of the condensate. The high momentum and energy resolution of …
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Probing and preparing novel states of quantum degenerate rubidium atoms in optical lattices
… systems. I first describe our work on realizing Bragg scattering of infrared light from ultracold atoms in optical lattices. This is a detection technique which probes the spatial ordering of a crystalline system, and has led to our observation of Heisenberg limited wavefunction dynamics. …
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Mean-field theory for the dynamics of superfluid fermions in the BCS-BEC crossover
… and the excitations of the system by two-photon Bragg scattering experiments.
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Sonic Crystal Noise Barriers
… (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 cylinders. Theoretical studies using Plane Wave Expansion (PWE), Multiple Scattering Theory (MST) …
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Spin-obit coupling in optical superlattices
… experimental detection of the stripe phase via Bragg scattering. This pseudospin-1/2 system could also be used for simulating quantum magnetism,and potentially novel models with topological properties and Majorana excitations.
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Fingerprinting analysis of non-crystalline pharmaceutical compounds using high energy X-rays and the total scattering pair distribution function
… the use of high energy X-rays coupled with total scattering pair distribution function (TSPDF) and fingerprinting analysis to investigate the local structures of non-crystalline pharmaceutical compounds. The high energy X-rays allow us to experimentally collect diffuse scattering intensities, …
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Strain in Halide Perovskites: Characterisation, Crystallography, Consequences
… diffraction techniques, for example using Bragg coherent diffraction imaging in Chapter 4 to image internal strain distributions in halide perovskite devices with nanoscale resolution. In so doing, I find intra-grain and grain-to-grain strain distributions to be remarkably heterogeneous, …
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Directional wavenumber characteristics of short sea waves
… important role in surface electromagnetic (e.m.) scattering. Currently radars and scatterometers which use e.m. scattering to remotely examine the ocean can produce estimates of the surface wind field, surface currents, and other scientifically important ocean processes. These estimates are based …
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Electron tomography of defects
… inner angle ( in) that included the rst order Bragg spots (in other series in had been 4-6 B). Extinctions occurred which were dependent on tilt; this produced only weak lines in the reconstruction. Bragg scattering in the ADF STEM image was estimated by summing simulated dark- eld dislocation …
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Organic semiconductor lasers with two-dimensional distributed feedback
… substrate. In periodically modulated waveguides Bragg scattering gives rise to distributed feedback. Utilizing UV-embossed plastic substrates with an appropriate onedimensional surface corrugation, edge- and surface-emitting lasers were fabricated. Excellent agreement is found between the …
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YSCAT Backscatter Distributions
<p>YSCAT is a unique ultrawideband microwave scatterometer developed to investigate the sea surface under a variety of environmental and radar parameters. The YSCAT94 experiment consisted of a six month deployment on the WAVES research tower operated by the Canada Center for inland Waters (CCIW). …
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Momentum-space lattices for ultracold atoms
… of the condensate atoms through a two-photon Bragg diffraction process. Neighboring states in the free-particle dispersion relation are characterized by a unique momenta and energy spacing such that we can independently control every aspect of their coupling. In this thesis, we report on the …