Physics, Astrophysics and Cosmology with Gravitational Waves

Gravitational wave detectors are already operating at interesting sensitivity levels, and they have an upgrade path that should result in secure detections by 2014. We review the physics of gravitational waves, how they interact with detectors (bars and interferometers), and how these detectors operate. We study the most likely sources of gravitational waves and review the data analysis methods that are used to extract their signals from detector noise. Then we consider the consequences of gravitational wave detections and observations for physics, astrophysics, and cosmology.Comment: 137 pages, 16 figures, Published version <http://www.livingreviews.org/lrr-2009-2

Underwater Source Localization based on Modal Propagation and Acoustic Signal Processing

Acoustic localization plays a pivotal role in underwater vehicle systems and marine mammal detection. Previous efforts adopt synchronized arrays of sensors to extract some features like direction of arrival (DOA) or time of flight (TOF) from the received signal. However, installing and synchronizing several hydrophones over a large area is costly and challenging. To tackle this problem, we use a single-hydrophone localization system which relies on acoustic signal processing methods rather than multiple hydrophones. This system takes modal dispersion into consideration and estimates the distance between sound source and receiver (range) based on dispersion curves. It is shown that the larger the range is, the more separable the modes are. To make the modes more distinguishable, a non-linear signal processing technique, called warping, is utilized. Propagation model of low-frequency signals, such as dolphin sound, is well-studied in shallow water environment (depth D\u3c200 m), and it was demonstrated that at large ranges (range r\u3e1 km), modal dispersion is utterly visible at time frequency (TF) domain. We used Peker is model for the aforementioned situation to localize both synthetic and real underwater acoustic signals. The accuracy of the localization system is examined with various sounds, including impulsive signal, sounds with known Fourier transform, and signals with estimated source phase. Experimental results show that the warping technique can considerably lessen the localization error, especially when prior knowledge about the source signal and waveguide are available

Interferometric Imaging of Lightning Initiation through LOFAR: Uncovering the Spontaneous and Not-So-Spontaneous Nature of Lightning Initiation in 3D

With recent advances in instrumentation and the continued development and refinement of analytical methods, the hindrances that previously existed in uncovering the physical processes governing the behavior of lightning are diminishing. The focus of this dissertation research, interferometric imaging of lightning initiation through beamforming via the Low Frequency Array (LOFAR), will describe in detail how both the instrumentation and methods cooperate to enable the detection of lightning processes in which are below the level of the galactic and thermal very high frequency (VHF) background on individual antennas within the array. These conditions have proven to be integral in uncovering of two novel methods of lightning initiation. For one event, a broad discharge is observed propagate with a velocity of 4.8 +/- 0.1 x 10^6 m/s while increasing in intensity from below the LOFAR noise level. For the second mode of initiation, a negative discharge was observed to propagate with a velocity of 1.5 x 10^3 m/s, which is three orders of magnitude slower than normal negative leaders. The first shares features with previously conceptualized ideas of how lightning initiates. This is supported by other researchers, but the findings have unique features that are not explained by the current theories how lightning initiates. Furthermore, the second initiation method is new and unlike any other known lightning process. Lastly, it should be noted that the results we present these use true 3D interferometric imaging techniques. Without the development and implementation of these methods the results reported within this work would not be possible. This thesis will briefly discuss the current understanding of lightning and related phenomena to give an overview the topic and context for why the study of lightning is important. This will the be followed by current theories of how lightning initiates, and then by discussion of the development of the 3D interferometric techniques and their implementation. Next, the thesis will present two recently observed processes by which lightning leaders form, after which is a discussion of the implications of these findings and how they are distinct from known lightning processes. Additionally, we will discuss results from the possible detection of gamma ray glows from the thunderstorm balloon campaign. These findings are the result of the updated methodology and instrumentation when this project was transferred to the University of New Hampshire from the Florida Institute of Technology. Lastly, the thesis concludes with a review of the implications of these discoveries and a discussion of future investigations, as well as, propose methods to further uncover additional details of the physical processes behind lightning initiation and where the results of the observations reported in this thesis fit within the current understanding of how lightning initiates

Flight Mechanics/Estimation Theory Symposium, 1990

This conference publication includes 32 papers and abstracts presented at the Flight Mechanics/Estimation Theory Symposium on May 22-25, 1990. Sponsored by the Flight Dynamics Division of Goddard Space Flight Center, this symposium features technical papers on a wide range of issues related to orbit-attitude prediction, determination and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

Nonlinear Dynamics

This volume covers a diverse collection of topics dealing with some of the fundamental concepts and applications embodied in the study of nonlinear dynamics. Each of the 15 chapters contained in this compendium generally fit into one of five topical areas: physics applications, nonlinear oscillators, electrical and mechanical systems, biological and behavioral applications or random processes. The authors of these chapters have contributed a stimulating cross section of new results, which provide a fertile spectrum of ideas that will inspire both seasoned researches and students

Flight Mechanics/Estimation Theory Symposium 1995

This conference publication includes 41 papers and abstracts presented at the Flight Mechanics/ Estimation Theory Symposium on May 16-18, 1995. Sponsored by the Flight Dynamics Division of Goddard Space Flight Center, this symposium featured technical papers on a wide range of issues related to orbit-attitude prediction, determination, and control; attitude sensor calibration; attitude determination error analysis; attitude dynamics; and orbit decay and maneuver strategy. Government, industry, and the academic community participated in the preparation and presentation of these papers

Spatial and Content-based Audio Processing using Stochastic Optimization Methods

Stochastic optimization (SO) represents a category of numerical optimization approaches, in which the search for the optimal solution involves randomness in a constructive manner. As shown also in this thesis, the stochastic optimization techniques and models have become an important and notable paradigm in a wide range of application areas, including transportation models, financial instruments, and network design. Stochastic optimization is especially developed for solving the problems that are either too difficult or impossible to solve analytically by deterministic optimization approaches. In this thesis, the focus is put on applying several stochastic optimization algorithms to two audio-specific application areas, namely sniper positioning and content-based audio classification and retrieval. In short, the first application belongs to an area of spatial audio, whereas the latter is a topic of machine learning and, more specifically, multimedia information retrieval. The SO algorithms considered in the thesis are particle filtering (PF), particle swarm optimization (PSO), and simulated annealing (SA), which are extended, combined and applied to the specified problems in a novel manner. Based on their iterative and evolving nature, especially the PSO algorithms are often included to the category of evolutionary algorithms. Considering the sniper positioning application, in this thesis the PF and SA algorithms are employed to optimize the parameters of a mathematical shock wave model based on observed firing event wavefronts. Such an inverse problem is suitable for Bayesian approach, which is the main motivation for including the PF approach among the considered optimization methods. It is shown – also with SA – that by applying the stated shock wave model, the proposed stochastic parameter estimation approach provides statistically reliable and qualified results. The content-based audio classification part of the thesis is based on a dedicated framework consisting of several individual binary classifiers. In this work, artificial neural networks (ANNs) are used within the framework, for which the parameters and network structures are optimized based the desired item outputs, i.e. the ground truth class labels. The optimization process is carried out using a multi-dimensional extension of the regular PSO algorithm (MD PSO). The audio retrieval experiments are performed in the context of feature generation (synthesis), which is an approach for generating new audio features/attributes based on some conventional features originally extracted from a particular audio database. Here the MD PSO algorithm is applied to optimize the parameters of the feature generation process, wherein the dimensionality of the generated feature vector is also optimized. Both from practical perspective and the viewpoint of complexity theory, stochastic optimization techniques are often computationally demanding. Because of this, the practical implementations discussed in this thesis are designed as directly applicable to parallel computing. This is an important and topical issue considering the continuous increase of computing grids and cloud services. Indeed, many of the results achieved in this thesis are computed using a grid of several computers. Furthermore, since also personal computers and mobile handsets include an increasing number of processor cores, such parallel implementations are not limited to grid servers only

A Search for Ultra-High Energy Neutrinos and Cosmic Rays with ANITA-3

The Antarctic Impulsive Transient Antenna (ANITA) is a balloon borne radio inter- ferometer, designed to detect the impulsive Askaryan radiation created by ultra-high energy neutrinos interacting in the ice sheets of Antarctica. Previous flights of the experiment have demonstrated an unexpected sensitivity to cosmic rays, detecting the radio emission from geo-magnetically induced transverse currents in extended air showers. The third flight of ANITA (ANITA-3) took place during the austral summer of 2014-15. In this thesis I present two contributions to the ANITA-3 experiment, the tim- ing calibration of the digitizer electronics, and my implementation of a real-time interferometric event prioritizer using a GPU flown with the experiment. Finally, I present a search for neutrinos and cosmic rays in the ANITA-3 data set. No evidence of neutrino interactions is observed, with zero candidate events discovered on a background of 0.11 ± 0.07 leading to the world’s best limit on the ultra-high energy neutrino flux in the energy range 10^19 eV to 10^21 eV. Four isolated, predominantly horizontally polarised events are found in the data. Further work is required to confirm these events have all the properties consistent with radio emission induced by cosmic ray air shower