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CIVINS / The changing state of warfare has driven the US Navy's area of operations closer to shore into littoral coastal waters. Mine Warfare has been proven as an extremely effective means of battlespace control in these waters. Mines can be inexpensively mass produced and rapidly deployed over large areas. The most common type of mine in use is the bottom placed mine, an object with simple geometry that sits on the seafloor. These mines often exhibit scour induced burial below the seafloor, making detection through traditional mine hunting methods difficult or impossible, while the mines themselves remain lethal. The Office of Naval Research (ONR) has developed a computer model that predicts the extent of mine burial to aid mine hunting and mine clearing operations. Investigations under ONR's Mine Burial Program are presently being conducted to calibrate and validate this model. This thesis uses data from the deployment of an acoustically instrumented model mine near the Martha's Vineyard Coastal Observatory in part of a larger, 16 total object investigation. A 2-axis pencil beam sonar was deployed concurrently with the mine to obtain microbathymetric measurements of the scour pit development and the progression of mine burial. Data correction techniques to correct for beam pattern induced bathymetry errors and a transformed coordinate system are detailed within. An analysis of scour pit dimensions includes scour depth, area, and volume as well as a look into percent burial by depth as a characteristic measurement important for operational mine hunting. The progression of mine burial is related to the wave climate, unsteady flow hydrodynamic forcing, and bed-load transport. The analysis examines the relative roles of these mechanisms in the scour-infill-bury process.

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

Actualmente en el Perú, la investigación submarina está poco desarrollada y en consecuencia no existen medios suficientes para seguir una evolución constante de nuestra ciencia y tecnología en esa rama. Además el actual sistema de navegación submarina está basado en el buceo, y como es sabido está limitado ya que toda investigación depende de las máximas capacidades a los que pueda llegar un hombre totalmente preparado para llevar a cabo esta tarea. Es por eso que la investigación submarina en el Perú está supeditada a lo que puedan lograr buzos submarinos, con los límites naturales que pueda soportar una persona totalmente capacitada. Entonces el desarrollo de un control electrónico, para implementarlo en un submarino eléctrico experimental puede solucionar en gran medida los problemas existentes que impiden una mejora substancial en lo que navegación submarina se refiere. El presente trabajo contiene cuatro capítulos donde se muestra el desarrollo del sistema. El primer capítulo trata sobre la problemática que se aborda en este trabajo mostrando las dificultades actuales en investigación. El segundo muestra la fundamentación teórica que respalda este estudio. El tercer capítulo muestra el diseño de la solución que se obtiene en este desarrollo, finalmente en el cuarto capítulo se muestra los resultados de pruebas del sistema integrado. Finalmente se concluye que el desarrollo de este control electrónico brinda las herramientas necesarias para desarrollar una investigación submarina efectiva, siendo necesario continuar con el estudio de esta rama tecnológica dentro del Perú. / Tesis

Tese de mestrado integrado. Engenharia Civil (especialização em Estruturas). Faculdade de Engenharia. Universidade do Porto. 2008

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 75-78).

This research is to study the fundamental theory of Synthetic Aperture Sonar (SAS) through numerical simulation and experimental analysis. The basic principle of SAS is to enhance the capability of spatial resolution by moving the transducer element to increase aperture so that it achieves a better resolution. The factors affecting the capability of resolution include the actual size of the transducers, frequency and its bandwidth, pulse length, and moving speeds. The effects of various factors on the resolution were examined through numerical simulation. The results have shown that the smaller the true size of the transducer, the better the resolution. Moreover, when the bandwidth is increased, the resolution also increases. The SAS is sensitive to the speed of movement due to the fact that data acquisition may be limited, therefore the speed can not be too high, e.g., less than 1.5 m/s. The experiment was carried out in a water tank of size 4 m x 3.5 m x 2 m. The transducers of AST MK VI 192 kHz were employed to transmit and receive signals. Copper spheres of various sizes (3 cm, 6 cm, 8 cm diameter) were used as targets. The data were obtained and analyzed, and the results have shown that the resolution may be achieved by SAS analysis, establishing the fundamental principle and offering opportunity for future study.

There are many Sciaenid species found in coastal water of Taiwan, and most of them can generate sound in the spawning season. However due to overfishing, the populations of these high economic value fishes have been greatly decreased. To study and protect Sciaenid, whose habitat should be identified to set up seasonal protection zones. In this study, easy and low cost measure by using passive sonar is proposed to map the habitat in the field. Measurement and analysis of Sciaenid¡¦s sound were performed to investigate its acoustic characteristic, and frequency range was found to be 350 to 1,500 Hz. The statistical distribution of sound levels can be built up by enough field measurement, therefore source levels can be defined in this method. In the addition, the transmission loss of in site shallow water was studied to compute the real decaying factor (TL=n*logR) of the survey site. By using 3 sonobuoys, with known source level distribution and transmission loss, the distance of possible habitat can then be inverted. Through enough measurements, the map of coastal habitat of Sciaenid can be generated with efficiency and accuracy.

Recovery of unattached offshore facilities or missing equipments is a challenging activity. Generally speaking, this activity involves a comprehensive procedure which includes: target characterization, searching, detection, verification, locating, reacquisition and salvage. Among them, target searching and detection are the most critical components of the whole procedure. The purpose of this investigation was dedicated in discussing the efficiency by the application of side-scan sonar, magnetometer and sub-bottom profiler simultaneously in searching, detecting, identifying and locating underwater stationary targets. Procedures of this research include: 1. Discussing the capabilities of instruments and verification cruises on target. 2. Discussing the salvage activity we conducted off Kaohsiung harbor on a depleted anchor. 3. Estimating the practicability of the methodology. According to the characteristics of these apparatus, the water depth, collected by echo sounder, is capable of expressing the relief of the seabed. Seabed sonographs, recorded by side-scan sonar, show that it is feasible to detect, verify and locate targets on the seabed. Sub-bottom profiler provides the sub-surface sedimentary information which can be used to detect buried targets. Magnetometer can detect environmental magnetic intensities, which can locate and determine the size of ferrous targets. Two depleted anchors were recorded off Kaohsiung harbor on the navigation chart. A recovery plan was then arranged which included 4 phases: collection of anchor characteristics, initial field survey and target detection, target verification and locating, target recovery. The underwater searching equipment employed in this activity include: side-scan sonar, sub-bottom profiler, magnetometer, echo sounder, underwater positioning system (include GPS), remotely operated vehicle (ROV) and professional divers. The offshore working platform used in this activity was R/V Ocean Research#3. Results of the initial search phase by side-scan sonar indicated there was only one potential target in the searching area. Follow up verification cruises confirmed acoustically that the target was an anchor with a piece of chain clogged on a block. The results of this investigation included the information such as the dimensions and the location of the anchor. Furthermore, the reason which caused the anchor being abandoned on the seafloor was derived. For underwater ferrous targets, such as anchor and chain cable, all of the aforementioned apparatus, have good potential for their detection and verification. It can be concluded that, applying these apparatus simultaneously can more effectively conduct searching, detecting, identifying and locating underwater stationary targets than by the application of a single instrument such as side-scan sonar system. Optical verifications of this target by ROV were attempted, nevertheless, were not success due to the difficulties in maneuvering OR#3 into proper position. An attempt to recovery this target by divers was arranged. But due to bad weather and rough sea state, the divers were not even allowed to dive. However, according to the experiences collected, a target reacquisition and recovery facility was built to fulfill the necessity of guiding divers to the target and lift it.

The research aims to design an experimental testing mechanism and process for measuring the scattering strength and the pattern induced by an underwater target. The experimental data are to compare with existing theoretical results to insure the integrity of experimental design. The experiment is conducted in a water tank of dimension 4m x 3.5 m x 2m. The main work is to measure the sound field scattered by a copper sphere of diameter 60mm. There are two types of sources employed in this analysis: one is omni-directional, 70kHz CTG-0708 transducer, and the other is directive, 192 kHz iTP-192k transducer. Both transducers transmit sine waves with the pulse lengths roughly equal to 0.143 msec (equivalent to 10 waves) and 0.333 msec (equivalent to 64 waves), respectively. The scattering field theory is based on the formulation developed by Hickling (JASA, 34, 1962, pp.1582-1592). The experimental process has demonstrated that it is more difficult to measure the forward scattering field than the backward scattering field, due to the fact that the forward scattering field is likely to be mingled with the direct waves. To deal with this problem, the treatment developed by L. Ding¡]JASA, 101,1997, pp.3398-3404¡^has been invoked, in that the direct waves may be filtered by phase shift. This procedure requires the special concern on synchronism of sound source in order to avoid the variation of scattering signals. The comparison between experimental and theoretical results shows that the discrepancy in the forward scattering sector is within 3 to 4 dB, while in the backscattering sector, it is within 1 to 2 dB; however, generally speaking, the variation of the curves show a good agreement. These results indicate that the design of this experiment is basically practicable, and with further improvements, it could be applied to measure other underwater targets. As a whole, the thesis is composed by basic theory deduction, experimental instrumentation, mechanism design, and experiment data analysis. The emphases place on the design and observation of the scattering experiment, data analysis, and further improvement.