is shown to follow an exponential distribution. These three models enable operators to explore the impact of various inputs prior to programming the vehicle, thus allowing them to choose the best combination of vehicle parameters that minimize the offset error between the reported and actual locations.

Approved for public release; distribution is unlimited / A simple low-noise hydrophone design with internal preamplifier is presented. This design is similar to published designs and is a variation of the design developed in the NPS thesis by Miguel Alvarado [2003], except that several improvement features are included. These include a simplification of the structure and its modes of vibration, a large reduction in package diameter and the effect its acoustic diffraction has on the sensitivity, and an extended upper frequency response of 42 kHz resulting from the simplified structure and reduced diameter. Furthermore, the modified geometry along with its orientation in the water should produce a very omni-directional response in the horizontal plane at the higher frequencies. Finally, an new feedback preamplifier design developed by Hofler and Alvarado was discovered to have some subtle but serious performance problems. These problems were resolved in this research and the resulting preamplifier performance was tested and documented herein. / Lieutenant, Hellenic Navy

Approved for public release, distribution unlimited / Underwater Acoustic Networks (UANs) hold enormous potential for both military and civilian applications. However, current networking protocols implemented are often sub-optimal, resulting in severely underutilized networks. We believe one of the key reasons for this shortcoming is a lack of good underwater acoustic propagation models for simulation packages used to evaluate UAN protocols. This thesis addresses this problem by developing a computationally-efficient approximation of a sophisticated analytical model called Monterey-Miami Parabolic Equation model (MMPE). The approximation can then be used to support UAN simulations. The characteristics of the problem make a statistical approach the methodology of choice for this study. Data was generated using the MMPE model. The data was used to develop a much less complex approximation for which an OpNet simulation module could be developed. The latter allows UAN operation to be modeled over a collection of nodes and over an interval of time, rather than a single point in time between two specific nodes, as modeled by the original equation. The result of this research can enable a more complete analysis of network enabling protocols and support more informed decisions regarding the appropriate node topology and protocols to use in order to increase network performance.

This dissertation presents a novel underwater machine vision technique which uses the optical properties of water to extract range information from colour images. By exploiting the fact that the attenuation of light in water is a function of frequency, an intensity-range transformation is developed and implemented to provide monocular vision systems with a three-dimensional scene reconstruction capability. The technique can also be used with images that have no salient, contrasting features and there are no restrictions on surface shapes. From a generalized reflectance map based on the optical properties of water, the closed form intensity-range transformation is derived to convert intensity images from various spectral bands into a range map wherein the value of each "pixel" is the range to the imaged surface. The technique is computationally efficient enough to be performed in real time and does not require specialized illumination or similar restrictive conditions. A calibration procedure is developed which enables the transformation to be practically implemented. An alternate approach to estimating range from multispectral data based on expanding the medium's transfer function and using these terms as elements in sensitivity vectors is also presented and analyzed. Mathematical analysis of the intensity-range transformation and associated developments is provided in terms of its performance in noise and sensitivity to various system parameters. Its performance as a function of light scattering is studied with the aid of computer simulation. Results from transforming actual underwater images are also presented. The results of this analysis and the demonstrated performance of the intensity-range transformation endorse it as a practical enhancement to underwater machine vision systems. / Graduate

No description available.

A digital modulation method using Chirp-Slope Keying (CSK) is developed for coherent underwater acoustic communications. Effective signal detection is a critical stage in the implementation of any communications system; we will see that CSK solves some significant challenges to reliable detection. This thesis is primarily based on analyzing the effectiveness of CSK through simulations using Matlab's Simulink for underwater communications. The procedure begins with modulating a chirp's slope by random binary data with a linear-down-slope chirp representing a 0, and a linear-up-slope chirp representing a 1. Each received symbol is demodulated by multiplying it with the exact linear-up-slope chirp and then integrating over a whole period (i.e., integrate and dump). This slope-detection technique reduces the need for the extensive recognition of the magnitude and/or the frequencies of the signal. Simulations demonstrate that CSK offers sturdy performance in the modeled ocean environment, even at very low signal-to-noise ratio (SNR). CSK is first tested using the fundamental communication channel, Additive White Gaussian Noise (AWGN) channel. Simulation results show excellent BER vs. SNR performance, implying CSK is a promising method. Further extensive analysis and simulations are performed to evaluate the quality of CSK in more realistic channels including Rayleigh amplitude fading channel and multipath.

Automatic target recognition capabilities in autonomous underwater vehicles has been a daunting task, largely due to the noisy nature of sonar imagery and due to the lack of publicly available sonar data. Machine learning techniques have made great strides in tackling this feat, although not much research has been done regarding deep learning techniques for side-scan sonar imagery. Here, a state-of-the-art deep learning object detection method is adapted for side-scan sonar imagery, with results supporting a simple yet robust method to detect objects/anomalies along the seabed. A systematic procedure was employed in transfer learning a pre-trained convolutional neural network in order to learn the pixel-intensity based features of seafloor anomalies in sonar images. Using this process, newly trained convolutional neural network models were produced using relatively small training datasets and tested to show reasonably accurate anomaly detection and classification with little to no false alarms. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

by Julian Guerra. / Thesis (M.S.C.S.)--Florida Atlantic University, 2011. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2011. Mode of access: World Wide Web. / This work seeks to understand water turbine noise generation and to make preliminary estimations of the noise levels. Any structure attached to a turbine upstream its blades will generate unsteady fluctuating loads on the blade's surface, which are proportional to the radiated acoustic pressure. The noise levels of a simplified turbine based on existing designs surpass the ambient noise levels of the ocean at low frequencies (< 20 Hz) by approximately 50 dB ref 1 μPa and stay under the ambient noise levels at higher frequencies for a blade-passing frequency of 0.83 Hz and point of observation (100 m, 45 degrees, 45 degrees) from the hub. Streamlining the cross-section of the upstream structure as well as reducing its width decrease the noise levels by approximately 40 dB ref 1 μPa, at low frequencies and moderately increase them at higher frequencies. Increasing the structure-rotor distance decreases the noise levels with increasing frequencies (> 30 Hz).

This thesis explores underwater imaging solutions in order to alleviate the poor contrast and the distortion in the perception of colour caused by the processes of scattering and absorption. We demonstrate through simulated experiments that imaging systems with higher spectral resolution than RGB could be useful for underwater imaging tasks such as estimating illumination and spectral reflectance values. We also tested hyperspectral imagers in real world experiments and found that the current technology is limited for underwater image enhancement applications. To address the problem of poor visibility in underwater scenes we introduce dehazing methods for underwater RGB images and videos. Current underwater dehazing methods suffer from limitations such as estimated parameters being biased towards pixels of bright objects in a scene and artefacts being created in regions that contain pure haze. Bright objects in a scene are avoided by using texture features during the estimation of parameters and local bias is avoided by taking information from an image at different spatial resolutions. We inhibit noise and artefacts being created in the pure haze regions by segmenting these areas and treating them as a special case. We address the spectral distortion present in underwater scenes by applying a water-type dependent white balancing step. We also demonstrate the application of our method to underwater videos with a weighted temporal smoothing of the estimated parameters and a Gaussian normalisation step that ensures segmentation of pure haze regions is stable across frames. We evaluate our methods both on quantitative metrics and through subjective experiments and demonstrate an improved performance in comparison to the state of the art in underwater image and video enhancement. We also show how no-reference underwater image quality assessment metrics do not always correspond with human judgement and provide suggestions on how they could be improved.

Lui Yiu Wing Howard. / "Architecture Department, Chinese University of Hong Kong, Master of Architecture Programme 1996-97, design report." / Includes bibliographical references (leave 109). / Acknowledgements --- p.I / Chapter Chapter 1 --- Introduction --- p.1 / Chapter 1.1 --- Background --- p.2 / Chapter 1.2 --- Issues and potential --- p.5 / Chapter 1.3 --- Objectives --- p.6 / Chapter 1.4 --- Concept --- p.7 / Chapter 1.5 --- Development process --- p.8 / Chapter Chapter 2 --- Site Selection --- p.9 / Chapter 2.1 --- Kowloon side --- p.10 / Chapter 2.2 --- Proposed entrance at Tsim Sha Tsui --- p.11 / Chapter 2.3 --- Hong Kong Island side --- p.14 / Chapter 2.4 --- Proposed entrance at Hong Kong Island --- p.15 / Chapter 2.5 --- Choices of route --- p.18 / Chapter 2.6 --- Matrix --- p.24 / Chapter 2.7 --- Final decision & site analysis --- p.25 / Chapter Chapter 3 --- Research and Field Works --- p.31 / Chapter 3.1 --- Underwater tunnel construction (Western Harbour Crossing) --- p.32 / Chapter 3.2 --- Building systems and services of underwater tunnel --- p.40 / Chapter 3.3 --- Environmental impacts and issues --- p.44 / Chapter 3.4 --- Images of under mater (psychological & physiological) compare to underground environment --- p.46 / Chapter Chapter 4 --- Case Studies --- p.47 / Chapter 4.1 --- Hong Kong case studies --- p.48 / Chapter 4.2 --- Overseas case studies --- p.50 / Chapter Chapter 5 --- Project Brief --- p.52 / Chapter 5.1 --- Client profile --- p.53 / Chapter 5.2 --- Programs development --- p.55 / Chapter 5.3 --- Inter-relationship of programs structure --- p.56 / Chapter 5.4 --- Individual program components --- p.57 / Chapter Chapter 6 --- Design Development --- p.58 / Chapter 6.1 --- Design concepts --- p.59 / Chapter 6.2 --- Master layout plan development --- p.65 / Chapter 6.3 --- Schematic design --- p.68 / Chapter Chapter 7 --- Final Design --- p.76 / Chapter 7.1 --- Pre-concept --- p.78 / Chapter 7.2 --- Master planning --- p.81 / Chapter 7.3 --- Tunnel portion --- p.88 / Chapter 7.4 --- Detail design --- p.97 / Chapter 7.5 --- Construction sequence --- p.103 / Chapter 7.6 --- Fire services --- p.106 / Bioliography --- p.109