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 39 for “"Gaussian approximation"”.
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Global Structure Search of Nickel Clusters Using Basin Hopping and Gaussian Approximation Potential
… using a machine learning potential called the Gaussian Approximation Potential (GAP), employed in conjunction with the Basin Hopping (BH) structure search optimization technique. The investigations are conducted over sizes ranging from 2 to 150 atoms, showcasing the robustness and accuracy of …
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On The Use Of Gaussian Filter Functions For Adaptive Optics
… to integrate and must be done numerically. The Gaussian method can be used in place of the conventional method for calculating the aperture filter functions. Evaluation of the Gaussian approximation for modeling a finite receiver aperture can be made by comparison of reduction in phase variance …
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Heat capacity measurements of yttrium barium(2)copper(3)oxygen(7-delta) near T(c): Fluctuation effects in a bulk superconductor
… correction to mean-field BCS theory (the Gaussian approximation) and in terms of true critical behavior. The analysis shows that the data are best described within the Gaussian approximation as three-dimensional fluctuations of a two-component order parameter, but the results do not rule …
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The application of multiuser detection to cellular CDMA
… of this receiver is analyzed using a standard Gaussian Approximation and an Improved Gaussian Approximation for AWGN and fading environments. Additionally, the resistance of the receiver to interference energy levels is explored. Parameter estimation is an important issue for interference …
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Simulation and analysis of a time hopping spread spectrum communication system
… led to an estimate of the performance using a Gaussian approximation similar to that used for direct sequence systems. Through the use of a fast simulation technique, it will be shown that in certain situations, the Gaussian approximation fails to accurately predict the performance. A numerical …
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'Variational' optimization in quantum field theory
… of the effective potential that go beyond the Gaussian approximation. Trial wavefunctionals are constructed by applying a unitary operator $U = e\sp{-is\pi\sb{R}\phi\sbsp{T}{2}}$ to a Gaussian state. We calculate the expectation value of the Hamiltonian using the non-Gaussian trial states …
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Linearly repeatered communication systems using optical amplifiers
… modulation. Our results, obtained by using the Gaussian approximation, are compared to those obtained by an 'exact' analysis. The results are also generalized for N-ary modulation schemes and systems having optical amplifiers as linear repeaters. Simple analytic formulae are derived for the …
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Performance analysis of CDMA systems in multipath channels
… the average probability of error without using a Gaussian approximation. The second objective is to model imperfect power control. The third objective is to incorporate multipath effects into this model using a discrete number of multipath components with some known probability distribution. This …
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Essays on Algorithmic Learning and Uncertainty Quantification
… for deriving sharp, non-asymptotic, uniform Gaussian approximation for partial sums in a reproducing kernel Hilbert space, which is then applied to construct uniform confidence bands for the widely-used kernel ridge regression algorithm. The third and final essay, titled “Frank-Wolfe Meets …
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Code-division multiplexing
… than the single-carrier format, even in an ideal Gaussian channel model. Each pulse is shaped via a prototype baseband filter such that when the demodulated signal is detected through a baseband matched filter, the resulting output samples satisfy the Generalized Nyquist criterion. Specifically, …
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Robust and scalable unsupervised learning via landmark diffusion, from theory to medical application
… high dimensional noise analysis with the help of Gaussian approximation, and show that Roseland is robust to noise. </p>
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Characterization and nonlinear cleanup of noise in optical communication systems
… mechanical approach with the semiclassical Gaussian approximation in terms of evaluating the bit-error rate and the optimal decision threshold. I will then describe a nonlinear pulse filter that transmits incident pulses while rejecting cw background as well as ASE noise. The filter is …
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An adaptive multistage interference cancellation receiver for CDMA
… cancellation receiver is derived, using a Gaussian approximation for Multiple Access Interference (MAI). The Bit Error Rate (BER) after any stage of interference cancellation can be computed from the signal to noise ratio, number of users and processing gain of the CDMA system. The BER …
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Semi-empirical and machine learned interatomic interaction potentials for zirconium: training, validation and application
… field were tracked. Furthermore, 2 tabulated Gaussian approximation potentials were constructed and calculated. Fourth, we utilized 4 embedded atom method force fields as well as 3 of our developed machine-learning force fields to validate threshold displacement energies in hcp Zr. Finally, we …
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Modeling and Analysis of the Effects of Impairments in Fiber Optic Links
… and intersymbol interference (ISI). By using a Gaussian approximation, effects of the first three impairments are analyzed. It is shown that signal-dependent noise introduces an error floor to the system and the bit-error-rate is considerably degraded if a nonzero-extinction ratio is applied to …
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Quantile Inference and Change Point Test under Time Series Non-stationarity
… series. New uniform Bahadur representations and Gaussian approximation schemes are established for a wide class of non-stationary and long memory linear processes. Furthermore, an asymptotic distributional theory is developed for the maxima of a class of non-stationary long memory Gaussian …
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Data-driven models of water and methane
… data. The fitting methods used are the Gaussian Approximation Potentials (GAP) [1, 2] and the permutationally invariant polynomials (PIP) [3] methods, the latter applied in collaboration. The long-range electrostatic interactions are calculated using a classical force field, the modified …
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Scalable Full Posterior Inference for Uncertainty-Aware Robot Perception
… We investigate scalable and expressive approximations for posterior distributions in SLAM, overcoming the limited expressivity of Gaussian approximations for representing commonly encountered non-Gaussian posteriors. We harness the sparsity in factor graphs for scalability and utilize …
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Selective cancellation of interference for CDMA
… is modeled using both the simple and an improved Gaussian approximation. This thesis also investigates the use of selective cancellation with bit averaging. Amplitude estimates over several consecutive symbols can be averaged to improve the accuracy of the estimate. An expression for the BER of …
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Coherence and synchronization of noisy-driven oscillators
… of this effect, considering noisy systems in the Gaussian approximation. Possible applications of the effect for the synchronization control are also discussed. Second, we consider synchrony of limit cycle systems (in other words, self-sustained oscillators) driven by identical noise. For weak …
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