This thesis is a study of a journey in the deep mystery of the eastern harbor on the Mediterranean sea in the city of Alexandria. For Herodotus, the four major elements for civilization's development overtime are water, air, land, and fire. In this project, the effort is made to connect three of the four elements within an architectural context: "Underwater museum". The building orientation, shape and location allow a discovery of the building elements and shape consequently while participating in the building visit. From street level, the building can be seen as a simple curved wall on the harbor facing the sea. While pursuing the passage in the journey, the building shape and components start to build the experience. Different lighting conditions, vertical and horizontal circulation methods, building form and structure are used to direct the journey starting from sky and land, through water, to underwater, then finally discovering the ruins at the seabed. / Master of Architecture

Approved for public release; distribution is unlimited. / Direct-Sequence Spread-Spectrum (DS-SS) is among the preferred modulation techniques for military applications. DS-SS offers three greatly desired characteristics. It allows for the development of Low Probability of Detection (LPD) and Low Probability of Intercept (LPI) systems and has a very good performance in fading channels. This thesis investigates the performance of the "Cross-Product RV (CRV) decomposition" as the basis of blind-equalization algorithms. The CRV is a rank-revealing decomposition alternative to the Eigenvalue Decomposition (EVD) that can provide a recursively updated estimate of the signal and noise subspace at a reduced computational cost. The CRV updating algorithm is implemented in MATLAB and evaluated in a previously proposed communication scheme intended for use in an underwater acoustic network called Seaweb. The underwater channel is modeled with the Monterey-Miami Parabolic Equation Model (MMPE) for various multipath perturbations. The receiver performance is examined using Monte Carlo simulation. Bit-error rates versus signal-to-noise ratio are presented for various, noise assumptions, and receiver synchronization assumptions. / Lieutenant, Hellenic Navy

This research concerns the continuing development of Seaweb underwater networking. In this type of wireless network the radio channel is replaced by an underwater acoustic channel which is strongly dependent on the physical properties of the ocean medium and its boundaries, the link geometry and the ambient noise. Traditional acoustic communications have involved a priori matching of the signaling parameters (e.g., frequency band, source level, modulation type, coding pulse length) to the expected characteristics of the channel. To achieve more robust communications among the nodes of the acoustic network, as well as high quality of service, it is necessary to develop a type of adaptive modulation in the acoustic network. Part of this process involves estimating the channel scattering function in terms of impulse response, the Doppler effects, and the link margin. That is possible with the use of a known probe signal for analyzing the response of the channel. The estimated channel scattering function can indicate the optimum signaling parameters for the link (adaptive modulation). This approach is also effective for time varying channels, including links between mobile nodes, since the channel characteristics can be updated each time we send a probe signal.

The U.S. Navy is developing through-water acoustic communications capability for undersea, distributed systems. These wireless communication links form a wide-area network of fixed nodes consistent with future autonomous sensors on the seafloor. Mobile nodes may operate in the domain of the grid using the fixed nodes as both navigation reference points and communication access points. This thesis evaluates the experimental performance of such networked communications between an undersea vehicle and a ship. Physical-layer considerations include refraction, wind-induced ambient noise, and vehicle aspect angle.

Thesis (M. Arch.)--Massachusetts Institute of Technology, Dept. of Architecture, 1982. / MICROFICHE COPY AVAILABLE IN ARCHIVES AND ROTCH. / Includes bibliographical references. / There are many reasons for undertaking a work such as this. Among them are the benefits offered to society when we acknowledge the potential of submersible structures, The provision of habitable underwater space remains an unexploited resource of great potential. Hopefully, it will be utilized in an ethically intelligent manner. Perhaps, the spiritual qualities of water will foster peace engendering or life sustaining pursuits resulting in paradigms of new urban forms and ideals. Herein, a broad view is offered of inspirations and ideologies leading towards a conceptual basis for sea dwellings. Developed from an ontogenesis into criteria for environmental design, siting, energy options and program ethics, a platform for establishing a sea utilization framework is imparted. The structural design development incorporates fundamental considerations for aqueous habitats. Reinforced concrete for sea use is discussed in depth including expositions on hydraulic cements and construction techniques . A basic sea structure design/analysis method which uses thin shell theory to reliably approximate the behavior of thick shells is presented through both simple and complex examples. The volume concludes with a metamorphosis of sea dwelling concepts in the form of original sketches, technical drawings and tone paintings. This thesis attempts to broaden the scope of knowledge of the architectural designer and planner through an effort to bridge ocean sciences, ocean engineering and architectural concerns. With the knowledge thus gained, it may be possible to project further into civilization's potential for cultural development within the limited context of the sea as a dwelling place. / by Ricardo Guillermo. / M.Arch.

The purpose of this paper is to investigate the survey strategy for marine archaeology using modern underwater survey and identification instruments and techniques on Peng-Hu underwater cultural site survey. The survey process can be roughly divided into three stages, preliminary and comprehensive survey¡]PCS¡^, double-check and localization survey¡]DLS¡^, and precise and identification surve¡]PIS¡^respectively. The objective of PCS is not to miss any possible target. The major equipments of the underwater engineering including marine magnetometer, the subbottom profiler, and the side-scan sonar are deployed simultaneously. After the comparisons and analysis of the images from various instruments obtained from PCS and DLS, the PIS will obtain the direct photo viewing of the targets using remotely-operated vehicle¡]ROV¡^or divers. This strategy has been conducted firstly in Kaohsiung Sizihwan bay Marine Test Field as the preliminary. The research by PCS and DLS analysis out twelve possible targets, detailed investigations, respectively, the north of Tongpan Islet and internal bay discovered two suspected sunken ships of Qing Dynasty, the Steamboat Willie and Matsushima, after crossing validation documentary and divers salvaged ashore of relics to corroboration for PIS, founded that the Steamboat Willie identity and corrected Matsushima, should be the Japanese Asaka Maru ship, also verify that the feasibility of this research. In addition, the research also integrated data for the three years on Peng-Hu survey to establish a database inquire system, it will help in analysis and review for the future.

Taiwan is surrounded by ocean, we expect through the underwater survey could make us know more about the marine resources, history and culture and understand how to use the natural resource well. The purpose of this paper is to investigate the survey strategy for marine archaeology using modern underwater survey and identification instruments and techniques on Peng-Hu underwater cultural site survey. The survey process can be roughly divided into three stages, preliminary and comprehensive survey (PCS), double-check and localization survey (DLS), and precise and identification survey (PIS) respectively. The objective of PCS is not to miss any possible target. The major equipments of the underwater engineering including marine magnetometer, the subbottom profiler, and the side-scan sonar are deployed simultaneously. After the comparisons and analysis of the images from various instruments obtained from PCS and DLS, the PIS will obtain the direct photo viewing of the targets using remotely-operated vehicle (ROV) or divers. This strategy has been conducted firstly in Kaohsiung Sizihwan bay Marine Test Field and Kaohsiung Cross-Harbor Tunnels as the preliminary. Then move to Peng-Hu Sea Area for the underwater archaeology survey which is authorized by Acdemia Sinica from April 2008 to June 2009. From the result, the megnetometer can help sonar to identify the target more specifically, especially for the sediment. It brings better result than side-scan sonar and multi-beam echo sounder which can only search the target on seabed and can search broader area than subbottom profiler. Therefor, magnetomator is an essential equipment for underwater archology.

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.

This thesis describes the development and testing of the Combustive Sound Source (CSS), which is a broadband underwater sound source. The CSS is being developed as a clean, safe, and cost effective replacement to underwater explosive charges, which exhibit an inherent danger to marine life and researchers using the charges. The basic operation of the CSS is as follows. A combustible mixture of gas is held below the surface of the water in a combustion chamber and ignited with an electric spark. A combustion wave propagates through the mixture and converts the fuel and oxidizer into a bubble of combustion products, which expands due to an increase in temperature, and then ultimately collapses to a smaller volume than before ignition, producing a high intensity, low frequency acoustic signal. The thesis begins by discussing the background, history, and purpose of developing the CSS. It continues by describing the current apparatus and the essential components and convenient features added to the latest mechanical design. The general operation is discussed along with a description of an experiment conducted to determine the acoustic output and robustness of the current CSS. The results of this experiment are presented in terms of the effect of volume, ignition depth, oxidizing gas, combustion chamber size, and repeatability of acoustic signatures. Discussion of apparatus robustness is presented to suggest improvements for future CSS designs. / text

The use of Remotely Operated Vehicles (ROVs) in exploring and building infrastructure in the ocean is expanding. ROVs are performing tasks underwater that would be difficult or impossible to do with human divers. These vehicles are being used in increasingly complicated and demanding environments that require improvements in the methods for controlling these vehicles. Currently, research into semi-autonomous control is being conducted to aide ROV pilots in compensating for environmental disturbances and unknown dynamics. To effectively implement semi-autonomous control, precise thrust forces must be elicited from the thrusters. This work discusses a low-level thruster controller that can be used as part of a semi- autonomous guidance, navigation and control system for a ROV. A thruster dynamics model describing the thrust force of a propeller-type underwater thruster was derived and implemented for the thruster on the Saab Seaeye Falcon ROV. The thruster dynamics model described is a quadratic equation that uses the propeller velocity to determine thrust force. This model includes a mechanism for compensation against the external motion of the thruster, such as occurs when the ROV moves through the water. Several experiments were performed to fully characterize the quadratic thruster dynamics model and test its ability to accurately predict thrust force based on a known ambient water velocity and propeller angular velocity. The drag force was calculated and removed from the force measurements to get the thrust force used in the model. The model coefficients were determined and then the resulting model was tested against experimental data to determine the efficacy of the model in the lab environment and compare it to a widely used linear thruster dynamics model. The results showed the quadratic model improved upon the linear model, and the quadratic model was valid over a larger range of ambient water velocities. The quadratic model was then inverted to provide a thruster control algorithm that determines the propeller angular velocity necessary to produce a desired thrust force. This algorithm was used to design a low-level thruster controller. This controller was designed to be used on an existing vehicle where thrust force feedback is not available and difficult or expensive to add. This allows it to be used in a wider range of applications than controllers that rely on such feedback to operate. The controller was implemented using a PID control loop to drive the angular velocity of the propeller to the desired rate. An iso-parametric mapping, which transforms the linear PID output to the non-linear thruster input, was added to provide a faster response time for the controller over the entire range of the propeller velocity. The performance of this low-level thruster controller was demonstrated in the test environment. The low-level thruster controller followed a desired thrust force under a range of ambient water velocities. The thruster characterization and low-level thruster controller was designed to be used on an existing ROV. The motivation behind this work is to build a controller that may be implemented for use by a high-level vehicle controller. The low-level thruster controller presented here does not depend on sensors or equipment that is largely unavailable on vehicles without costly retrofits, and the experimental characterization does not require intimate knowledge of the inner workings of the thruster. This makes it easy to implement and generalize to a variety of thrusters. The results of this work show a low-level thruster controller than can be used in a control schema for existing ROVs. / Graduate / 0547 / matt@amosbuchanan.net