Página 6 dos resultados de 1134 itens digitais encontrados em 0.014 segundos

‣ Supervisory control of an autonomous underwater vehicle using an acoustic communication link

Kreamer, William Ryan, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 86 leaves; 5753243 bytes; 5753005 bytes; application/pdf; application/pdf
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by William Ryan Kreamer.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.; Includes bibliographical references (leaves 84-86).

‣ Vessel valuation : an options approach

Largiadèr, Caspar Andri, 1965-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 75 leaves; 4138217 bytes; 4137977 bytes; application/pdf; application/pdf
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by Caspar Andri Largiadèr.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1999.; Includes bibliographical references (p. 74-75).

‣ Analysis of functionally graded material object representation methods

Jackson, Todd Robert
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 224 leaves; 18425052 bytes; 18424809 bytes; application/pdf; application/pdf
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by Todd Robert Jackson.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.; Includes bibliographical references (leaves 218-224).

‣ Navigation and target localization performance of the autonomous underwater vehicle REMUS; Navigation and target localization performance of the AUV Remote Environmental Measuring UnitS

Cassidy, Christopher John, 1970-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 75 leaves; 6183967 bytes; 6183728 bytes; application/pdf; application/pdf
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by Christopher John Cassidy.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.; Includes bibliographical references (leaves 72-75).

‣ Modeling of shell forming by line heating

Yu, Guoxin, 1968-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 179 leaves; 11000937 bytes; 11000696 bytes; application/pdf; application/pdf
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by Guoxin Yu.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.; Includes bibliographical references (leaves 172-179).

‣ An approach for developing a preliminary cost estimating methodology for USCG vessels

Gray, Mark James
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (334 leaves); 10931241 bytes; 10976351 bytes; application/pdf; application/pdf
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by Mark James Gray.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1987.; Bibliography: v. 2, leaves 287-291.

‣ Algorithms for three-dimensional free-form object matching; Algorithms for 3D free-form object matching

Ko, Kwang Hee, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 126 leaves; 6593704 bytes; 6593511 bytes; application/pdf; application/pdf
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This thesis addresses problems of free-form object matching for the point vs. NURBS surface and the NURBS surface vs. NURBS surface cases, and its application to copyright protection. Two new methods are developed to solve a global and partial matching problem with no a priori information on correspondence or initial transformation and no scaling effects, namely the KH and the umbilic method. The KH method establishes a correspondence between two objects by utilizing the Gaussian and mean curvatures. The umbilic method uses the qualitative properties of umbilical points to find correspondence information between two objects. These two methods are extended to deal with uniform scaling effects. The umbilic method is enhanced with an algorithm for scaling factor estimation using the quantitative properties of umbilical points. The KH method is used as a building block of an optimization scheme based on the golden section search which recovers iteratively an optimum scaling factor. Since the golden section search only requires an initial interval for the scaling factor, the solution process is simplified compared to iterative optimization algorithms, which require good initial estimates of the scaling factor and the rigid body transformation. The matching algorithms are applied to problems of copyright protection.; (cont.) A suspect model is aligned to an original model through matching methods so that similarity between two geometric models can be assessed to determine if the suspect model contains part(s) of the original model. Three types of tests...

‣ Design and control of an autonomous destroyer model; Autonomous destroyer model

Wu, Albert (Albert Tetai), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 leaves; 5671520 bytes; 5673645 bytes; application/pdf; application/pdf
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by Albert Wu.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2000.; Includes bibliographical references (leaf 66).

‣ Steady and unsteady dynamics of an azimuthing podded propulsor related to vehicle maneuvering

Stettler, Jeffrey W. (Jeffrey Wayne)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 187 p.; 39477222 bytes; 40353275 bytes; application/pdf; application/pdf
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While the implementation of azimuthing propulsors powered by internal electric motors (often called "podded propulsors") into the commercial ship market has been swift, the understanding of their hydrodynamics through research, particularly in the area of maneuvering performance, has been very limited. This thesis research investigates the steady and unsteady dynamic maneuvering forces associated with an azimuthing podded propulsor, and provides supporting theoretical insight toward understanding their mechanisms and prediction. Because of the wide range of potential applications of azimuthing podded propulsion in the marine field, dynamic force phenomena applicable to maneuverability of both large and small scale vehicles are investigated. These include quasi-steady vectored maneuvering forces, of importance to all maneuvering vehicles or ships, as well as unsteady or transient maneuvering forces, which have more significance to the maneuverability of smaller vehicles, particularly for precision control applications. The ultimate goal of the research is to provide a comprehensive understanding of the maneuvering forces associated with an azimuthing podded propulsor, such that future maneuvering and control applications, and computational fluid dynamics studies in the field...

‣ Legacy Computing Markup Language (LCML) and LEGEND -- LEGacy Encapsulation for Network Distribution; LEGEND

Geiger, Stephen Kurt
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 133 p.; 5694968 bytes; 5700502 bytes; application/pdf; application/pdf
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The rapid increase of computing power and emergence of distributed computing technologies such as Grid computing create new opportunities for scientific computing. One of the challenges faced in harnessing the emerging computational power is how to effectively use traditional command-line driven "legacy" codes within a networked framework; and a related challenge is how to make the operation of such codes a more user-friendly process. In this work a specification for an XML-based Legacy Computing Markup Language (LCML) is developed. This language can be used to create a parametized encapsulation of command-line driven codes and their associated files. Such an encapsulation can then be viewed and edited with a program developed to process LCML descriptions. The program LEGEND (LEGacy Encapsulation for Network Distribution) is under development as a Java implementation of such a program. LEGEND demonstrates that a validating graphical user interface can automatically be generated from an LCML description. Some issues related to the encapsulation of legacy programs and use of LCML and LEGEND are discussed, as well as the possibilitites for the integration of these technologies with Sun Grid Engine (SGE) and Globus software.; by Stephen Kurt Geiger.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ The effectiveness and economic impact of enhancing container security

Dresser, Eric L. (Eric Lane)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 125 p.; 8871450 bytes; 8876677 bytes; application/pdf; application/pdf
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Over the past few decades, international containerized shipping has evolved to become the main artery of global trade, providing both convenient and inexpensive access to goods from markets around the world. Yet the very size and efficiencies that have made container shipping such an attractive means of transport have also created a system that is highly vulnerable to terrorist exploitation. This paper outlines the current initiatives taken by both the public and private sector to address the security vulnerabilities in the container industry. The solution targets three main areas for, security: documentation/information, physical security, and inspections. The technology utilized to improve the physical security of the container can also be used to track shipments and secure the container from pilferage. This generates a win-win relationship between enhancing container security while improving supply chain information and control. An economic model is used to demonstrate the cost savings and cost avoidance from the information and control provided by security technologies. The savings to shippers more than offsets the cost of implementing these technologies. This is a valuable approach to solving the problem of container security because it concurrently provides incentive to the private sector and protects global interests.; by Eric L. Dresser.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ A scatter diagram approach to the selection of design currents for prediction of marine riser vortex-induced vibration; (cont.) This scatter diagram method could reduce the cost of risers by reducing the over- conservatism that is introduced by the common practice of using an envelope design current profile. It also reduces the analysis time required for the brute force approach by allowing the designer to focus on only the most relevant profiles.

Donnelly, Jessica Mary
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 49 leaves; 2451416 bytes; 2453365 bytes; application/pdf; application/pdf
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This paper describes a scatter diagram approach for the classification of large numbers of current profiles for use in the prediction of riser fatigue damage due to vortex-induced vibration. Scatter diagrams have long been used to characterize the probability of various combinations of wave height and period, which are then used to assess wave forces. To predict VIV fatigue damage the designer needs to know which current profiles have the combined property of long regions of relatively constant velocity and relatively high speed. A sorting algorithm is proposed which searches every current profile for long regions of relatively constant flow speed. The probability of each length and speed combination is assessed and the data is used to populate the bins of the scatter diagram. The designer need only select relatively few representative profiles for detailed VIV analysis from those bins that would account for the most damage. The method is tested by making comparison to a brute force approach in which each of many thousands of profiles is evaluated for fatigue damage by running it in the SHEAR7 VIV response prediction program.; by Jessica Mary Donnelly.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering...

‣ Roll stabilization for fast monohulls by using passive and active lifting appendages

Ulusoy, Talha
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 143 p.; 6269327 bytes; 6275329 bytes; application/pdf; application/pdf
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Roll stabilization for monohulls is an important issue in naval architecture. Several methods including roll stabilization tanks, active control fins, rudder roll stabilization systems, and bilge keels are commonly used for roll stabilization purposes and each one of them has its own advantages and disadvantages. In this thesis roll stabilization is studied by using passive and active roll stabilization configurations with hydrofoils. The main objective of this research is to identify an effective roll stabilization system for use on high- speed monohull vessels. The analysis of the performance of a passive hydrofoil configuration is used as a starting point for the development of active control mechanisms. A generic fast monohull was created for study purposes and the SWAN-2 code (ShipWaveANalysis), a state-of-the-art time domain simulation program, was used for the analysis of the linear free-surface flow around the vessel. Simulations were carried out in regular waves incident at angles ranging from 90⁰, 105⁰,120⁰,135⁰ and 150⁰ degrees relative to the ship axis, 900 being beam waves and 180⁰ degree being head waves. The ship was equipped with a hydrofoil fixed amidships, quarter to aft and aft to determine the sensitivity of roll motion on the longitudinal position of the lifting appendage.; (cont.) It was found that the most efficient location for the hydrofoil is amidships leading to a 20% to 60% roll motion reduction (depending on the wave angle and ship speed) of the RMS value of roll motion in an ISSC spectrum. Also studies were performed to determine the planform area of the hydrofoil for optimal roll motion reduction. In addition...

‣ The Jones Act : an economic and political evaluation

Smith, Richard A. (Richard Allen), 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 119 leaves; 6986409 bytes; 6991367 bytes; application/pdf; application/pdf
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On June 5, 1920, the Merchant Marine Act of 1920, also known as the Jones Act, became law. The Jones Act, a cabotage law, restricts American waterborne domestic trade to vessels flagged in the United States, owned by citizens of the United States, operated by citizens of the United States, and built in the United States. This highly restrictive law has become an integral part of American maritime policy. A brief history of the maritime policies of the United States and the Merchant Marine Act of 1920 is followed by an evaluation of the effects of the act on the maritime and shipbuilding industries, an evaluation of the effects on the American economy, and an evaluation of the political debate surrounding the act. Conclusions are made regarding the effects of the act and recommendations are made for the future of the act.; by Richard A. Smith.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 2004.; Includes bibliographical references (leaves 115-119).

‣ Applying lean manufacturing initiatives to naval ship repair centers : implementation and lessons learned

Murphy, Brian P. (Brian Patrick), 1963-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 58 p.; 3592492 bytes; 3594828 bytes; application/pdf; application/pdf
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The United States Navy is under pressure to reduce the cost of fleet maintenance in order to redirect funds for the construction of new ships and submarines. The Navy looks to private industry for process improvement ideas such as the Theory of Constraints, Six Sigma and Lean Manufacturing Principles. This thesis examines the Lean Manufacturing movement in the private sector of ship repair and how it eventually came to government owned ship repair operations. Recent National Ship Research Program (NSRP) initiatives provide shipyards a strategy of how to select areas of an operation for Lean improvements. The Norfolk Naval Shipyard method is a combination of the Theory of Constraints, Six Sigma and Lean Principles called Lean Sigma. The Lean Sigma methodology for planning, executing and sustaining lean improvement and how to measure success with various metrics is presented. Lean Sigma is implemented into the Electric Motor Rewind and Repair Center as a case study. Before and after assessments, lessons learned, and recommendations from the implementation case study are presented.; (cont.) Details of the challenges and pitfalls encountered during the Lean Sigma implementation in the areas of culture, budget, management, metrics and cost benefit measurement...

‣ Decisionmetrices : dynamic structural estimation of shipping investment decisions; Dynamic structural estimation of shipping investment decisions

Dikos, George
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 179 p.; 12764418 bytes; 12771956 bytes; application/pdf; application/pdf
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This dissertation develops structural models for analyzing shipping investment decisions, namely ordering, scrapping and lay-up decisions in the tanker industry. We develop models, based on a microeconomic specification, that allow us to understand the dynamics of shipping investment decisions under uncertainty and test interrelated economic assertions with aggregate data. The main framework is a three-party model with a structural specification of the time charter rate process, based on market clearing conditions. Structural estimation of shipping investment decisions is performed by using advanced econometric methods consistent with the Real Options and Market Microstructure literature. Several statistical tests are employed, in order to evaluate alternative specifications. Once the aggregate models have been identified and estimated, some of the early hypotheses in maritime economics are addressed and re-evaluated. Finally we integrate the three different investment modules and reconstruct the structural transportation supply function that determines the equilibrium time charter rate. System identification techniques and advanced econometric methods are employed separately and then combined, resulting in an exceptional "within-sample"...

‣ Efficient simultaneous localization and mapping algorithms using submap networks; Efficient SLAM algorithms using submap networks

Kim, SungJoon, 1970-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 223 leaves; 9228976 bytes; 9238436 bytes; application/pdf; application/pdf
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Autonomous mapping of large-scale environments has been a critical challenge confronting researchers in mobile robotics. This thesis investigates two aspects of the large-scale simultaneous localization and mapping (SLAM) problem: (1) the behavior of the covariance matrix in the Kalman filter solution to the linear Gaussian SLAM problem, and (2) the development of new algorithms for efficient large-scale mapping. The key issue motivating study of the linear Gaussian SLAM problem is to understand the behavior of the uncertainty estimates with time. In this thesis, we provide an analysis of the asymptotic behavior of the full covariance SLAM solution. We present a novel generalized closed-form solution to the single degree-of-freedom SLAM problem (known as the MonoRob problem). We examine the cross correlation behavior for the case of observed and non-observed features, and show that a feature must be repeatedly reobserved for it to become fully correlated with other features. Additionally, we provide a new "tight" lower bound for the map uncertainty for a certain class of the MonoRob problem. The second part of the thesis develops new techniques for attacking the scaling problem in SLAM.; (cont.) The work builds on the Constant Time SLAM (CTS) method developed by Newman and Leonard...

‣ Scattering from sub-critically insonified buried elastic shells

Lucifredi, Irena
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 217 p.; 10275853 bytes; 10285045 bytes; application/pdf; application/pdf
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Buried mines have been so far generally considered undetectable by conventional high frequency sonars mostly due to the low levels of energy penetrating into the sediment at high frequencies. Furthermore, in a shallow water environment a high frequency high grazing angle mine-hunting sonar approach is vastly limited by the coverage rate, making the detection and classification of buried objects using subcritical grazing incidence an attractive alternative. In mine countermeasurements (MCM) applications resonance of man-made elastic targets is a pivotal concept that distinguishes them from rocks or other clutter that may have a similar mine-like shape. Nevertheless, burial of an elastic target in the seabed results in a variety of modifications to the scattered response caused by different physical mechanisms, geometric constrains, and intrinsic properties of the sediment. The goal of this thesis was to identify, analyze and explain the fundamental effects of the outer sediment and the proximity of the seabed interface on the scattering of sound from elastic shells insonified using low frequencies at subcritical incident angles.; (cont.) The approach to scattering from buried elastic shells consisted of the development and the evaluation of ways of computing the scattered field...

‣ Combinatorial algorithms for stacking problems

Aslidis, Anastasios Haralampos
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 243 leaves; 8948166 bytes; 8947976 bytes; application/pdf; application/pdf
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by Anastasios Haralampos Aslidis.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Ocean Engineering, 1989.; Includes bibliographical references (leaves 229-230).

‣ Fracture prediction in metal sheets

Lee, Young-Woong
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 411 p.; 22951572 bytes; 22969776 bytes; application/pdf; application/pdf
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One of the most important failure modes of thin-walled structures is fracture. Fracture is predominantly tensile in nature and, in most part, is operated by the physical mechanisms of void nucleation, growth, and linkage. For ductile sheet, fracture is preceded by necking. Prediction of necking which limits sheet metal formability is well established and has been developed over the past several decades. However, an in-depth understanding of the mechanical process inside the neck leading to sheet metal fracture is lacking. This is true for both static and high intensity, short duration loads. Furthermore, there is an ever increasing need to raise the safety envelope of existing protective structures against localized extreme loading. The present thesis addresses four parts of the many outstanding issues in sheet metal fracture. In the first part, the new Bao-Wierzbicki (BW) fracture criterion formulated in terms of the accumulated equivalent plastic strain with the stress triaxiality as a weighting function is considered. Using the equations of plane stress von-Mises plasticity and the strain-to-stress mapping procedure, the BW fracture criterion is transformed to the spaces of the principal tensile strains and stresses in a sheet and compared with experimental results for various materials. An extensive comparative study of the most widely used fracture criteria is then conducted.; (cont.) The applicability and expected errors of those criteria are investigated. In the second part...