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‣ MathCAD model for the estimation of cost and main characteristics of air-cushion vehicles in the preliminary design stage

Gougoulidis, Georgios
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 100 p.; 5370122 bytes; 5374315 bytes; application/pdf; application/pdf
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In the naval architecture terminology, the term ACV (Air Cushion Vehicle) refers to this category of vehicles, in which a significant portion of the weight (or all the weight) is supported by forces arising from air pressures developed around the craft, as a result of which they hover in close proximity to the sea. Major types are hovercrafts and SES (Surface Effect Ships). A well-designed Air Cushion Vehicle (ACV) is superior to a conventional ship, because it has less drag and requires less horsepower to operate at the same speed. An ACV is much more fuel-efficient than a ship with similar capacity or size. Rising fuel prices and shortages will make ACVs a desirable form of transportation in the future. In order to cover this future trend in marine transportation, a MathCAD model for the estimation of the main characteristics of Air Cushion Vehicles in the preliminary design stage is being developed. This model is based on a statistical analysis of the various parameters of existing crafts. For this reason, a statistical database has been created using publicly available information. A regression analysis has been performed using the data collected and the trend lines for every case have been derived.; (cont.) For the validation of the code...

‣ Responses of floating wind turbines to wind and wave excitation

Lee, Kwang Hyun
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 55 leaves; 1895511 bytes; 1897721 bytes; application/pdf; application/pdf
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The use of wind power has recently emerged as a promising alternative to conventional electricity generation. However, space requirements and public pressure to place unsightly wind turbines out of visual range make it desirable to move large wind farms offshore and into deeper coastal waters. A necessary step for the deployment of wind turbines into deeper waters is the development of floating platform systems. This thesis will present a general technical description of two concept designs for floating wind turbine systems, and make a preliminary evaluation of their performance in wind and waves. A new approach to computing the nonlinear wave excitation is also presented.; by Kwang Hyun Lee.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.; Includes bibliographical references (leaf 55).

‣ Robust evaluation of differential geometry properties using interval arithmetic techniques

Lee, Chih-kuo
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 82 p.; 2725656 bytes; 2729017 bytes; application/pdf; application/pdf
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This thesis presents a robust method for evaluating differential geometry properties of sculptured surfaces by using a validated ordinary differential equation (ODE) system solver based on interval arithmetic. Iso-contouring of curvature of a Bezier surface patch. computation of curvature lines of a Bezier surface patch and computation of geodesics of a Bezier surface patch are computed by the Validated Numerical Ordinary Differential Equations (VNODE) solver which employs rounded interval arithmetic methods. Then. the results generated from the VNODE program are compared with the results from Praxiteles code which uses non-validated ODE solvers operating in double precision floating point arithmetic for the solution of the same problems. From the results of these experiments, we find that the VNODE program performs these computations reliably, but at increased computational cost.; by Chih-kuo Lee.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.; Includes bibliographical references (p. 79-82).

‣ Experimental hydrodynamics of spherical projectiles impacting on a free surface using high speed imaging techniques

Laverty, Stephen Michael
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 80 leaves; 6623911 bytes; 6627257 bytes; application/pdf; application/pdf
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This thesis looks at the hydrodynamics of spherical projectiles impacting the free surface using a unique experimental WebLab facility. Experiments were performed to determine the force impact coefficients of spheres and then compare obtained results to theories developed by Von-Karman [ 19] and Wagner [20]. It was found that experimental results matched a generalized Wagner approach developed by Touvia Miloh [12]. A critical impact speed for splash formation was determined before which no splash cavity would form. The cone angle formed behind an impacting object was also studied. The cone angle was found to be a function of depth and impact speed over the range of impact velocities tested. Steel spheres ranging in diameter from 0.64 cm (1/4 in) to 5.08 cm (2 in) were used at impact speeds from 0 to 6.9 m/s. Standard billiard balls of diameter 5.72 cm (2.25 in) were also used in this study. As part of this project, the WebLab facility was constructed. iMarine WebLab is an interactive teaching tool used to educate students in various aspects of marine hydrodynamics and experimental fluid mechanics.; by Stephen Michael Laverty, Jr.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.; Includes bibliographical references (leaves 78-80).

‣ Deterministic and stochastic modeling of the water entry and descent of three-dimensional cylindrical bodies

Mann, Jennifer L. (Jennifer Lynn)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 77 p.; 3555490 bytes; 3558650 bytes; application/pdf; application/pdf
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An effective physics-based model has been developed that is capable of reliably predicting the motion of a three-dimensional mine-shaped object impacting the water surface from air and subsequently dropping through the water toward the sea bottom. This deterministic model, MINE6D, accounts for six-degree-of-freedom motions of the body. MINE6D allows for physics-based modeling of hydrodynamic effects due to water impact, viscous drag associated with flow separation and vortex shedding, air entrainment, and realistic flow environments. Unlike existing tools that are limited to plane motions only, MINE6D captures the myriad of complex three-dimensional motions of cylindrical mines observed in field and laboratory experiments. In particular, accounting for the three-dimensional viscous drag and air entrainment cavity produces an accurate prediction of the velocity, trajectory, and orientation of mines freely dropping in the water. The model development and effects on body motion are presented for both viscous drag and air entrainment cavities.; (cont.) Monte Carlo simulation using MINE6D is then used to obtain statistical characterization of mine motions in practical environments. These statistical results are not only the essential input for stochastic bottom impact and burial predictions of mines but also important for the design of mines.; by Jennifer L. Mann.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ Hydrodynamic performance and vortex shedding of a biologically inspired three-dimensional flapping foil

Lim, Keith, K. L
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 131 p.; 11019540 bytes; 11025034 bytes; application/pdf; application/pdf
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The dynamics of flapping remains a subject a great theoretical and practical interest. Propulsion and maneuvering by flapping, optimized through years of evolution, is ubiquitous in nature, yet marine pulsars inspired by examples of highly maneuverable marine life or aquatic birds remain unheard of. The motivation of this research stems from the notion that better propulsive strategies could be obtained from flapping foils; presenting superior alternatives to the conventional propeller for waterborne propulsion. The propulsive properties of a Nasa 0012 linearly tapered rigid foil, with a .5.5 cm average chord and 24.6 cm span performing a combined roll and pitch motion are investigated. The mean planform area thrust coefficient and efficiency are recorded over a paramtetric space that included three roll amplitudes, with induced heave (at 0.7 span) to chord ratio, ḣ₀.₇ / c = 1.0, 1.5 and 2.0; Strouhal numbers ranging from 0.2 to 0.6 and maximum angle of attack varying from 15 to 45 degrees. Results show that a maximum planform area thrust coefficient of 2.09 is achieved at h₀.₇ / c = 1.5, St = 0.6 and ,[alpha][max] = 30⁰. The thrust and efficiency data also reveal a useful performance trend where at low [alpha][max]...

‣ Shipping : is it a high risk low return business?

Patitsas, Leon S
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 226 p.; 13788500 bytes; 13798058 bytes; application/pdf; application/pdf
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The purpose of this thesis is to investigate the risk and return characteristics of the shipping business. Shipping profitability and returns are evaluated and an analysis is performed to examine whether the returns are adequate to compensate the amount of risk the investor is bearing. Statistical tools are used to quantify risk and the average returns of the shipping industry are measured and compared with other asset classes. Diversification among different types of ships, and different asset classes is used to maximize the return and minimize the risk of an "efficient fleet". The Capital Asset Pricing Model and the efficient frontier are used to identify the optimal asset allocation. Valuation methods and investment timing techniques are used in order to increase the probability of success and improve the decision making. Finally a real project is evaluated using financial tools.; by Leon S. Patitsas.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.; Includes bibliographical references (p. 78-79).

‣ Port security and information technology

Petrakakos, Nikolaos Harilaos
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 92 p.; 4387441 bytes; 4391236 bytes; application/pdf; application/pdf
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The terrorist attacks of September 11th 2001 on New York and Washington DC shed light on the many security shortcomings that sea ports and the entire import and export process face. A primary source of these problems is the information sharing process which makes it hard to track the source of a problem in the import and export process due to lack of information and coordination. This thesis attempts to examine these data sharing problems by looking at what federal agencies, ports, and other private firms have been doing to solve the problems. The document exchange between various stakeholders and the process behind that was also examined to find potential problems. The reason behind doing this is because it is essential to understand the process and its problems before any meaningful results can be extracted from examining the efforts being done to solve the problems. The findings were similar for all cases showing that the primary reason preventing any of these problems to be solved is the unwillingness of commercial stakeholders to share information due to lack of incentives and privacy concerns.; by Nikolaos Harilaos Petrakakos.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.; Includes bibliographical references (p. 92).

‣ Multi-frequency cable vibration experiments

Wiggins, Andrew (Andrew Dale)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 101 p.; 4593779 bytes; 4597935 bytes; application/pdf; application/pdf
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A series of Multi-Frequency cable vibration experiments at Reynolds number 7600 were carried out at the MIT Tow Tank using the Virtual Cable Towing Apparatus (VCTA). Motions observed in a Direct Numerical Simulation of a flexible cylinder in a shear current were imposed on the VCTA and force measurements taken. Results showed a good agreement between the RMS lift coefficients of experiment and simulation. Complex Demodulation Analysis revealed significant lift force phase modulations. This analysis also showed that to a large extent the 3-dimensional behavior of the DNS was captured by the 2-d experiment in regions of low inflow, and to a lesser extent in regions of high inflow. Applications of results to future vortex induced vibration force models are discussed.; by Andrew Wiggins.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2005.; Includes bibliographical references (p. 99-101).

‣ Comparative naval architecture analysis of diesel submarines

Torkelson, Kai Oscar
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 91 leaves; 3898121 bytes; 3901874 bytes; application/pdf; application/pdf
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Many comparative naval architecture analyses of surface ships have been performed, but few published comparative analyses of submarines exist. Of the several design concept papers, reports and studies that have been written on submarines, no exclusively diesel submarine comparative naval architecture analyses have been published. One possible reason for few submarine studies may be the lack of complete and accurate information regarding the naval architecture of foreign diesel submarines. However, with some fundamental submarine design principles, drawings of inboard profiles and plan views, and key assumptions to develop empirical equations, a process can be developed by which to estimate the submarine naval architectural characteristics. comparative naval architecture analysis creates an opportunity to identify new technologies, review the architectural characteristics best suited for submarine missions and to possibly build more effective submarines. An accurate observation is that submarines designed for different missions possess different capabilities. But are these unique capabilities due to differences in submarine naval architecture? Can mission, cost, or other factors affect the architecture?; (cont.) This study examines and compares the naval architecture of selected diesel submarines from data found in open literature. The goal is to determine weight group estimates and analyze whether these estimates provide a relevant comparison of diesel submarine naval architecture.; by Kai Oscar Torkelson.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ Increasing intermodal transportation in Europe through realizing the value of short sea shipping

Tenekecioglu, Goksel
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 89 leaves; 5159220 bytes; 5162898 bytes; application/pdf; application/pdf
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This thesis describes the role of short sea shipping within the transportation network in the European Union. It examines the existence of externalities relating to congestion, infrastructure, air pollution, noise, and accidents in the transportation sector. It evaluates the level of these externalities and also their effects on the Community. It then explains current attempts to internalize these factors, or incorporate them into the cost of transportation that the user pays. It concludes that current efforts are lacking and do not produce the most beneficial situation for the citizens of Europe. Consequently, the thesis investigates other possible methods of internalization that may produce more advantageous results and analyzes their possible effects on the transportation sector. The value of short sea shipping is examined in regards to the previously mentioned externalities. It concludes that, with the exception of the emission of sulfur dioxide, maritime transportation outperforms other modes of transportation by producing relatively few external effects.; (cont.) The current status of the short sea shipping industry is then described, followed by a discussion of intermodal transportation and the initiative within the European Community to increase the use of intermodal transportation. Two case studies are then reviewed...

‣ Supply chain security along the Columbia River : an analysis of maritime supply chain security with respect to communication between security experts

Sichel, Alexander R. (Alexander Russell)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 102, D1-D64, E1-E18 leaves; 8658550 bytes; 8666333 bytes; application/pdf; application/pdf
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The amount of cargo that enters the US border is at an all time high. Cargo containers and vessel shipments enter the US from all over the world. Tracking these shipments from their origin to destination requires professional expertise. Security organizations, such as the Regional Maritime Security Coalition of the Columbia River, realize the potential of these professionals, who track and coordinate cargo containers as they move through a supply chain, to enhance security of maritime cargo. In order to utilize these supply chain logistic professionals in a security coalition, proper training and certification would be required to comply with the US Federal Code on Liability Protection. This study examines the requirements that are necessary to certify supply chain logistic professionals as certified volunteers in an information sharing, security communication network to prevent terrorist activity, smuggling, theft, and to assist in general crisis mitigation. The thesis studies how the RMSC is currently developing its security communication system around supply chain logistic professionals, and the requirements and training that would be necessary to certify them under the US Federal Code.; by Alexander R. Sichel.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ A preliminary design tool for resistance and powering prediction of catamaran vessels

Zouridakis, Fragiskos
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 144 p.; 7290379 bytes; 7296440 bytes; application/pdf; application/pdf
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During the last decade catamaran ships have been very rapidly evolved into a dominant mode of sea transportation. Their particular area of proliferation is the short sea shipping where they show considerable superiority over competitive designs in attributes such as power requirements, economy, space availability and seakeeping. The rapid growth of the market has led to the need for an expanded range of catamaran designs in terms of size, speed, and payload diversity (passengers, vehicles, containers). However, even now, there is a scarcity of publicly available preliminary design tools for catamarans. This fact hinders the ship owner and naval architect from being able to quickly assess the relative merits of alternative potential designs without having to resort to expensive expert consultancy solutions. Resistance characteristics and power requirements are principal aspects of the catamaran design spiral as they are strongly coupled with speed and fuel economy, and, consequently, the operating and cost efficiencies of the vessel. This thesis aims towards the development of a tool that predicts the resistance and required power for catamaran vessels in the range of 20m to 80m. Vessels with both round bilge and hard chine hulls are considered.; (cont.) Reasonable accurate prediction may be achieved for all speed regions of intended operation. (Displacement...

‣ Design and analysis of a high-rate acoustic link for underwater video transmission

Pelekanakis, Konstantinos
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 75 leaves; 3360736 bytes; 3363804 bytes; application/pdf; application/pdf
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A high bit rate acoustic link for underwater video transmission is examined. Currently, encoding standards support video transmission at bit rates as low as 64 kbps. While this rate is still above the limit of commercially available acoustic modems, prototype acoustic modems based on phase coherent modulation/detection have demonstrated successful transmission at 30 kbps over a deep water channel. The key to bridging the remaining gap between the bit-rate needed for video transmission and that supported by the acoustic channel lies in two approaches: use of efficient image/video compression algorithms and use of high-level bandwidth-efficient modulation methods. An experimental system, based on discrete cosine transform (DCT) and Huffman entropy coding for image compression, and variable rate M-ary quadrature amplitude modulation (QAM) was implemented. Phase-coherent equalization is accomplished by joint operation of a decision feedback equalizer (DFE) and a second order phase locked loop (PLL). System performance is demonstrated experimentally, using transmission rate of 25000 symbols/sec at a carrier frequency of 75 kHz over a 10 m vertical path.; (cont.) Excellent results were obtained, thus demonstrating bit rates as high as 150 kbps...

‣ Lorentz actuators for turbulence control and underwater acoustic communications

Sura, Daniel A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 180 leaves; 8228710 bytes; 8729269 bytes; application/pdf; application/pdf
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Lorentz actuator dynamics in a fluid are governed by the fundamental principles of electromagnetism and hydrodynamics and have several potential applications in the marine field. Two areas of interest where improvements would lead to significant contributions are the turbulence control and underwater acoustic communication fields. The ability to control turbulence is directly associated with controlling drag. Shipping industries and naval institutions are constantly seeking ways to reduce drag on marine vessels. A reduction in drag would have significant impact in the marine field allowing reduced vessel fuel consumption and faster marine travel. Experimental implementation for turbulence control was carried out at the Marine Hydrodynamics Laboratory of MIT on a flat plate setup with an integrated Lorentz actuator cassette. The data acquisition system included a dynamometer setup with integrated load cells for direct force measurements, and a Laser Doppler Velocimetry system for measuring boundary layer profiles in the flow. The results showed apparent wall shear reduction of about 30% over the Lorentz actuated cassette using the boundary layer technique but no measurable change in drag with the direct force measurement method. Most of the hardware used today in underwater acoustic communications result in a limited frequency bandwidth for data transmission and is a function of the material properties used in the design. The advantage of using Lorentz actuators for underwater sound transmission is that the frequency bandwidth is controlled by the electronics which allows us to select broader ranges of frequency transmission. A hydrophone was used to quantify acoustic noise in a conducting fluid 100 mm from the surface of a Lorentz Actuator...

‣ A framework for evaluating advanced search concepts for multiple autonomous underwater vehicles (AUV) mine countermeasures (MCM)

Gooding, Trent R. (Trent Ronald), 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 114 leaves; 5752855 bytes; 5757596 bytes; application/pdf; application/pdf
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by Trent R. Gooding.; Thesis (Nav.E. and S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, February 2001.; Includes bibliographical references (leaves 113-114).

‣ Computational and experimental investigations of the flow around cavitating hydrofoils

Fine, Neal E
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 87 leaves; 2793999 bytes; 2793805 bytes; application/pdf; application/pdf
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by Neal E. Fine.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1988.; Includes bibliographical references.

‣ The complete second-order diffraction and radiation solutions for a vertically axisymmetric body

Kim, Moo-Hyun
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 251 leaves; 10349549 bytes; 10349358 bytes; application/pdf; application/pdf
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by Moo-Hyun Kim.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1989.; Includes bibliographical references (leaves 233-238).

‣ Diaphragm forming : innovation and application to ocean engineering

Langlois, Gilles
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 107, [5] p.
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by Gilles Langlois.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1994.; Includes bibliographical references (p. 105-107).

‣ Underwater in situ optical measurements and coral fluorescence for shallow water remote sensing

Fuchs, Eran, 1963-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 90 leaves
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by Eran Fux.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1996.; Includes bibliographical references (leaves 89-90).