Search for drowned human body by divers is a highly technical dependent, difficult and dangerous work. How to improve this kind of underwater rescue work, under the considerations of the safety of divers and the effectiveness in detection of the target within a limited period of time, is a major subject for fire fighters. For the time being, a normal search and rescue procedure basically includes visual observation of the bank area and surficial water area. In addition, divers are sometimes sent out to complement the search procedure by either visual observation or tactile. A much more efficient way to conduct this kind of recovery activity is to incorporate the state of art of the underwater acoustics technique, such as scanning sonar, into the operation procedures. This investigation was focused on the application of scanning sonar and image analysis techniques as well as seafloor object identification skills for the detection of drowned human body. In addition, safety of divers under water and their activities could be improved and monitored. Remotely operated vehicle (ROV) and towed operated vehicle (TOV) should be incorporated into the normal search procedure for the purpose of improving target identification in the future. Under this circumstance, both target searching rate and divers¡¦ safety could be effectively improved or guaranteed. The proposed procedure which incorporated both acoustical (i.e., scanning sonar) and optical (i.e., ROV or TOV) apparatus are expected to simplify and improve the underwater target search and identification activities and will allow fire fighters a more professional and safety way in conducting drowned human body recovery activities.

The purpose of this study is to incorporate the knowledge and technique of marine geotechnical engineering, underwater acoustic surveying and hydraulic experiment into studying the problems of artificial reefs off Ling-yang, Kaohsiung Country, South-western part of Taiwan deployed in March 1996. Based on hydraulic experiment, we try to observe the scouring mechanism of artificial reefs. Beside, two other reefs Yung-an, Fang-lio reef were surveyed in this study .The ultimate goal of this investigate was intended to deduce ways to solve the problem of excessive scouring and subsidence, and decide the appropriate environment of the seafloor to deploy artificial reefs for promoting fishing developing. The topography of Ling-yang is generally gentle. Based on the test of physics and mechanics, most surficial sediments at the surface was cohesiveless sand sediments including a lot of seashell. Therefore, we deduced that the surficial sediments are easier to drift caused by monsoon and typhoon in summer. The phenomenon indicated that the surface of sediments is unstable when the sediments are cohesiveless or were loaded by other forces. This study showed that there were obvious scouring effect occurred in and around the reefs, Ling-yang, Yung-an and Fang-lio. The most serious scouring area was occurred in Ling-yang, and a majority of reefs have been buried there. Therefore, the major factors, which could induce excessive subsidence or undermining of the artificial reefs in the testing site, were proposed to be scouring effects. Compared with other reef areas, the scouring effect was related to the grain distribution on the seafloor and the velocity of currents. In the aspect of preventing subsidence of reefs, the reefs closely deployed were better than that loosely deployed.

Thesis (M.S. in Computer Science)--Naval Postgraduate School, September 2003. / Thesis advisor(s): Geoffrey Xie, John Gibson. Includes bibliographical references (p. 65-66). Also available online.

In scuba diving any problem that can be solved underwater will be solved underwater. This helps to prevent a dive from being disrupted. If a diver is separated from the group and is unable to find the group within a short time both the diver and dive group must surface to find each other and rejoin. To prevent the separation of divers a Stray Diver Alert System has been devised involving wireless communication to track the diver's position relative to the dive masters. Underwater communication holds many challenges that are not found in above water networks. Through simulation, it has been shown that the communication requirements for the Stray Diver Alert can be met with existing technology and protocols. This has been done by evaluating the resolution, power consumption and physical size of the device for three different communication protocols. This has shown that current technology is capable of meeting the requirements of the stray diver alert system.

Underwater communication is necessary for a variety of applications, including transmission of diver speech, communication between manned and/or unmanned underwater vehicles, and data harvesting for environmental monitoring, to name a few. Examples of communication between underwater vehicles include unmanned or autonomous underwater vehicles (UUV or AUV) for deep water construction, military UUVs such as submarine drones, repair vehicles for deep water oil wells, scientific or resource exploration, etc. Examples of underwater communication between fixed submerged devices are sensor networks deployed on the ocean floor for seismic monitoring and tsunami prediction, pollution monitoring, tactical surveillance, analysis of resource deposits, oceanographic studies, etc. The underwater communication environment is a challenging one. Radio signals experience drastic attenuation, while optical signals suffer from dispersion. Because of these issues, acoustic (sound) signals are usually used for underwater communication. Unfortunately, acoustics has its own problems, including limited bandwidth, slow propagation, and signal distortion. Some of these limitations can be overcome with advanced modulation and coding, but to do so requires better understanding of the underwater acoustic propagation environment, which is significantly different than air- or space-based radio propagation. The underwater environment must be studied and characterized to exploit these advanced modulation and coding techniques. This thesis addresses some of these concerns by proposing a derivation of the envelope level crossing rate of the underwater channel, as well as a simulation model for the channel, both of which agree well with the measured results. A velocity estimator is also proposed, but suffers from a high degree of root mean square error

As diverse and data-heavy underwater applications emerge, demanding requirements are further imposed on underwater wireless communication systems. Future underwater wireless communication networks might consist of both mobile and stationary nodes which exchange data such as control, telemetry, speech, and video signals among themselves as well as a central node located at a ship or onshore. The submerged nodes, which can, for example, take the form of an autonomous underwater vehicle/robot or diver, can be equipped with various sensors, sonars, video cameras, or other types of data acquisition instruments. Innovative physical layer solutions are therefore required to develop efficient, reliable, and high-speed transmission solutions tailored for challenging and diverse requirements of underwater applications. Building on the promising combination of multi-carrier and cooperative communication techniques, this dissertation investigates the fundamental performance bounds of cooperative underwater acoustic (UWA) communication systems taking into account the inherent unique characteristics of the UWA channel. We derive outage probability and capacity expressions for cooperative multi-carrier UWA systems with amplify-and-forward and decode-and-forward relaying. Through the derived expressions, we demonstrate the effect of several system and channel parameters on the performance. Furthermore, we investigate the performance of cooperative UWA systems in the presence of non-uniform Doppler distortion and propose receiver designs to mitigate the degrading Doppler effects.

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 39-43).

Thesis--Auburn University, 2008. / Abstract. Vita. Includes bibliographical references (p. 40-44).

Thesis (M.S. in Engineering Acoustics)--Naval Postgraduate School, December 2008. / Thesis Advisor(s): Rice, Joseph A. "December 2008." Description based on title screen as viewed on January 29, 2009. Includes bibliographical references (p. 89-91). Also available in print.

Thesis (Ph. D.)--University of Rhode Island, 2004. / Typescript. Includes bibliographical references (leaves 118-121).