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The purposes of this research have been to determine a) the basic physical causes of acoustic scattering from zooplanktonic organisms and b) necessary criteria for future acoustic studies involving these animals. In situ measurements at 102 kHz have been made of the scattering of sound from a volumetric distribution of a zooplanktonic organism, the euphausiid. Quantitative information was recorded on analog magnetic tape and subsequently converted to digital form for analysis. Based on simultaneous measurements of side and back scattering from euphausiids and on a mathematical model, four-fifths of the scattered sound is considered to be caused by the compressibility contrast between the animals and the sea water. The remaining one-fifth is attributed to density contrast. Acoustic energy distribution curves are characteristic of the number and size of the animals contained in the small volume of the ocean that was studied. Acoustic counting of the animals gave results that compared favourably with simultaneous controlled net sampling. The back scattering cross-section of a typical euphausiid at 102 kHz has been found to be 1.4 x 10⁻⁴ cm² . Based on this value it is possible to predict the optimum frequency and intensity of incident sound for future acoustic studies involving these animals. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

Quantitative volume-scattering measurements were compared to the distribution of euphausiids in Saanich Inlet, British Columbia. Scattering was recorded at 42, 107, and 200 kHz from the depths of high euphausiid concentrations, and volume-scattering coefficients were determined. No scattering from euphausiids was recorded by a 11 kHz echo-sounder. Daily variations in the volume-scattering coefficients, m(Δz), generally compared well with variations in the concentration of euphausiids. The daily behaviour of the high-frequency scattering layer., and therefore m(Δz) and the concentration of euphausiids, was influenced by moonlight and weather conditions as well as the presence or absence of an oxycline in the inlet. In the absence of an oxycline conditions would have been closer to conditions in the open ocean. Under these circumstances euphausiid concentrations and m(Δz) were low in the mornings and gradually increased throughout the day; the high-frequency scattering layer consolidated. During the evening migration, the layer became more diffuse, and the number of euphausiids per cubic metre decreased. The scattering cross-section, σ (cm²), of a euphausiid was found to increase with the average dry weight and length, and with increased frequency. For each cruise σ was approximately one order of magnitude apart at the three frequencies. The values of σ (in cm²) ranged from 4.81 x 10⁻⁵ to 5.21 x 10⁻³(200 kHz), 5.49 x 10⁻⁶ to 3.99 x 10⁻⁴ (107 kHz), and 2.30 x 10⁻⁷ to 3.67 x 10⁻⁵ (42 kHz). / Science, Faculty of / Zoology, Department of / Graduate

The issue of Command and Control (C2) is generally associated with the management infrastructure of large scale systems for warfare, public utilities and public transportation, and is concerned with ensuring that the distributed human elements of command and control can be fully integrated into a coherent, total system. Intelligent Autonomous Systems (IASs) are a class of complex systems that perform tasks autonomously in uncertain, dynamic environments, the management of which can be viewed from the perspective of embedded command and control systems. This thesis establishes a vision for the modular construction of intelligent autonomous embedded C2 systems, which defines a complex integration problem characterised by distributed intelligence, world knowledge and control, concurrent processing on heterogeneous platforms, and real-time performance requirements. It concludes that by adopting an appropriate systems infrastructure model, based on Object Technology, it is possible to view the construction of embedded C2 systems as the integration of a temporally assembled collection of reusable components. To support this metaphor it is necessary to construct a common reference model, or standards framework, for the representation and specification of modular C2 systems. This framework must support the coherent long term development and evolution in system capability, ensuring that systems are extensible, robust and perform correctly. In this research, which draws together the themes of other published research in object oriented systems and robotics, classical AI models for intelligent systems architectures are used to specify the overall system structure, with open systems technologies supporting the interoperation of elements within the architecture. All elements of this system are modelled in terms of objects, with well defined, implementation independent interfaces. This approach enables the system to be specified in terms of an object model, and the development process to be framed in terms of object technology, defining a new approach to IAS development. The implementation of an On-board Command and Control System for an Autonomous Underwater Vehicle is used to validate these concepts. The further application of emergent industrial standards in distributed object oriented systems means that this kind of component-based integration is scaleable, providing a near-term solution to generic command and control problems, including Computer Integrated Manufacturing and large scale autonomous systems, where individual autonomous systems, such as robots, form elements of a complete, total intelligent system, for application to areas such as fully automated factories and cooperating intelligent autonomous vehicles for construction sites.

Earth psychosomatically shrinks with each passing technological feat as persons and thoughts, continents apart, relay information with coherent conversation. Advances in satellite uplink speed, signal coverage, transportation methodologies, et cetera culminates a planet whose habitats, when distance is measured in time, no longer appear as weeks apart, but only a few hours worth of travel. Population continues to rise while Earth slowly wilts from the human_s stampeding footprint. In the context of humanity's relatively brief existence, number of trees is fewer nowadays than ever recorded. Atmospheric carbon parts per million is at an all-time high. Habitable land slowly dwindles along coasts as sea levels continue to rise. Evidence of climate change and studies on the depletion of the ozone layer forebode a grim future for surface dwelling. As humanity continues to expand, the given density of continents can only rise, resulting in hubris and apocalyptical outcomes lest stagnation occurs. While natural disasters and war may cull population rates and expansion, another solution exists within the duration before extrasolar expansion: subaqueous habitation. Oceans compromise over 71% of Earth_s surface, meaning expanding settlements into the deep blue more than triples habitable land. Natural disasters, such as tornadoes, meteorites, electrical storms, drought, heavy snowfall, wildfire, nuclear detonation, haboobs, and surface burning lessen in their hazardous effect with the absence of land. Other present disasters, including hurricanes, submerged volcanoes, torrential currents, landslides, earthquakes, tsunamis, death stranding, and pollution dictate the concepts building design must adhere in order to create habitable living. Furthermore, the effects which sensory deprivation (namely from the absence of light and wide-open spaces) have on inhabitants must be remedied through fabricated scenarios. These may include Virtual Reality, and artificial islands. In terms of expansion, design then must decide whether to unction as a grouping of pods, or a single society a la L_Unite d_habitation. Submersible vehicles may be used to travel from one structure to another, gather resources, and function similarly to vehicles on preset roads. This opens up the possibility of multiple underwater cities, and pathing networks spanning inbetween continents. In the far future, vehicles may be designed for traversing land and underwater terrain. In sum, the highly unexplored ocean provides alleviation to Earth_s near-distant carrying capacity until mankind undergoes planetary exodus. / 0 / SPK / specialcollections@tulane.edu

A MEMS piezoresistive pressure sensor provides a low-cost and accurate means of detecting and quantifying small-scale disturbances in underwater environments. A highly sensitive MEMS pressure sensor has been developed that can be packaged in two different ways – one in a cylindrical housing, and the other in a flexible, yet robust, strip configuration – enabling more freedom for the user to choose an option that fits their needs. The sensing element of each consists of four piezoresistive elements in a Wheatstone Bridge configuration arranged on a deformable buried-oxide layer, which is then bonded to a Silicon base layer with a hollow cavity carved using reactive-ion etching. Previous work has shown the survivability of these sensors in an underwater environment and also measurements of low frequency pressure changes due to flow and varying turbulence intensities. The present work is focused on evaluating these pressure sensors and testing the limits of the sensing element in the low, medium, and high frequency regime (<100Hz to >1kHz) to gain further insight into the performance. Five experimental tests were developed and conducted to guide this research objective. The sensor responses under different flow conditions were measured and analyzed with selected filtering and resampling techniques to eliminate background noises. First, the sensors were calibrated to ensure their linearity and to determine their pressure sensitivities. Then, using bench-top testing rigs and a water tunnel, the sensor performance was evaluated in submerged environments when subjected to multiple small-scale flow disturbances across the tested frequency regime. It was found that the present sensors are capable of providing more accurate measurements across a tested frequency regime of 0 to 20,000Hz when compared to other off-the-shelf products. Testing in submerged environment showed that the sensors are capable of detecting small-scale pressure fluctuations as a result of eddies which are evident in a Von Karman vortex street and a turbulent flow. Despite the presence of EMI noise within a water tunnel, the sensors demonstrated a decay of pressure fluctuations that is consistent with previous research in the field. Overall, the present work increases understanding of the sensors' performances across a broad range of frequencies and provides insight into potential uses and future work. / Master of Science / Pressure sensors are an important, if not the most important, measurement device available today. Pressure sensors play an integral role in the everyday lives for everyone around the world; from applications in medicine, aerospace, autonomy and computation, these sensors provide real-time feedback and help gain a deeper understanding of a system. However, with the technological advances in the Modern Age, there has been a growing need for smaller, cheaper, and faster sensors. As a result, engineers continued to improve sensor performance in the past century with new technologies. A micro-electromechanical system (MEMS) pressure sensor offers a low-cost and energy efficient method to quantify pressure fluctuations within a system. This work focuses on evaluating the performance of three MEMS pressure sensors for use in a submerged environment to detect small-scale pressure fluctuations across a broad range of frequencies. Five different tests were conducted to investigate this research objective. The first three were performed in a controlled underwater environment from which direct conclusions could be made. The last two were performed in an uncontrolled underwater environment from which comparisons to literature and known phenomena were used to draw conclusions. A key result showed that the sensor measurements aligned with prior research in the field. Multiple data reduction techniques were also used during post-processing to ensure accurate data was being collected. The studies showed that the developed MEMS pressure sensors provided the same capabilities as other commercially available pressure measurement devices, all the while displaying a higher sensitivity and broader frequency range. Furthermore, the survivability and robustness of the sensor was proven when subjected to large- and small-scale flow disturbances in a water tunnel.

What is a library in the future? Will it be extinct? I don't believe so. In fact, library is never a space only for storing, neither in the past nor in the future. It provide quiet space. From this perspective, a library will never be extinct. However, it will merge into some other kinds of space. This is why I put this building at a place which is more like a park. I put this building under the water at Duck Pond because I want to make it merge into landscape around. In my design, the roof of the building could be served as a connection between the bank and island. It makes the island accessible and extends the landscape. My project is a library for thesis book of CAUS in Virginia Tech. There are so many graduate students which would leave there best projects for our college. These books are not only good references for following students, but also witness for development of CAUS. I want to design a library which is just for these thesis books. / Master of Architecture

Unlike many terrestrial applications, GPS is unavailable to autonomous underwater vehicles (AUVs) while submerged due to the rapid attenuation of radio frequency signals in seawater. Underwater vehicles often use other navigation technologies. This thesis describes a range-based acoustic navigation system that utilizes range measurements from a single moving transponder with a known location to estimate the position of an AUV in geodetic coordinates. Additionally, the navigation system simultaneously estimates the currents acting on the AUV. Thus the navigation system can be used in locations where currents are unknown. The main contribution of this work is the implementation of a range-based navigation system in geodetic coordinates for an AUV. This range-based navigation system is implemented in the World Geodetic System 1984 (WGS 84) coordinate reference system. The navigation system is not restricted to the WGS 84 ellipsoid and can be applied to any reference ellipsoid. This thesis documents the formulation of the navigation system in geodetic coordinates. Experimental data gathered in Claytor Lake, VA, and the Chesapeake Bay is presented. / Master of Science

This Research Report presents some of the equations of underwater acoustics that relate to the signal excess noise received by a transducer. The basic structural equation is developed, as are defining equations for each term in that equation. An analysis is performed utilizing typical values to ascertain if the elements of the structural equation can be simplified. Results delineate that several terms of that equation can be neglected while maintaining a relative high degree of accuracy.

Current wireless underwater communication technologies—i.e. underwater acoustic modems—are extremely bandwidth limited as compared to land-based wireless technologies. Additionally, acoustic modem technologies are not advancing at the same high rate as computing technologies. Therefore, it is proposed that image compression techniques be applied to sonar maps. This will both reduce the amount of information that must be transferred by these modems which in turn reduces the amount of time required to send information across acoustic channels. After compression is performed on one platform's map, the information is transformed into the coordinate system of the uncompressed second, non-collocated platform's map and the two maps are additively compared. If returns are common in both maps, they will be show up with higher energy than the individual maps' returns. This thesis proves that application of image compression techniques on range-angle maps allow for target detection, down to a minimum target strength value of 0 dB, independent of target return strength. / Master of Science