Página 1 dos resultados de 1727 itens digitais encontrados em 0.029 segundos

‣ Public interest and the formulation of international air transport policy in a developing nation : Mexico vis-á-vis the United States

Lisker-Melman, Bernardo
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 401 leaves; 20197845 bytes; 20197643 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
109.22766%
by Bernardo Lisker-Melman.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS.; Vita.; Bibliography: leaves 395-400.

‣ Instrument scan, performance, and mental workload in aircraft pilots

Stephens, Albert Thomas
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: [1], 246 leaves; 10742235 bytes; 10741994 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.96387%
by Albert Thomas Stephens.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1981.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS.; Bibliography: leaves 129-132.

‣ Engineering design and political choice: the space shuttle 1969-1972

Pace, Scott
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 228 leaves; 25712153 bytes; 25711910 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
109.113545%
by Scott Pace.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 1982.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND AERONAUTICS; Bibliography: leaves 220-228.

‣ Design trade studies and assessment for advanced quiet aircraft concepts

Tan, David York Luen, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 104 leaves; 908618 bytes; 860272 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.84996%
(cont.) designed for 4,000nm range, 25,000 to 35,000ft cruise altitude, Mach 0.8 at cruise, and 10,000 to 14,000ft takeoff field length. By identifying the main high-level design drivers of an aircraft design, the mission for a baseline silent aircraft planform and engine was determined. A silent aircraft was designed for a range of 4,000nm and 250 passengers. A noise assessment was conducted on the engine and airframe noise sources of the resulting design. The noise impacts of five engine (jet, fan forward, fan rearward, core, and turbine) and airframe (airfoil, elevator, slat, drag rudder, and undercarriage) noise sources were investigated in terms of their noise footprints and, more specically, the loudest noise caused outside the airport boundary. The greatest noise source was the drag rudder, which was required to offset the idle thrust of the engine during approach. Because of the variable cycle and shielding effects on the embedded engines, engine noise at takeoff was greatly reduced. The main contribution of engine noise was the fan rearward noise. Overall, airframe and engine noise during approach was found to be 12dBA and 9dBA louder than during takeoff respectively. The loudest airframe noise occurred during a 3-degree approach...

‣ A multi-objective, decomposition-based algorithm design methodology and its application to runaway operations planning

Anagnostakis, Ioannis
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 388 p.; 20408634 bytes; 20460405 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.84831%
(cont.) to the design of a heuristic decomposed algorithm for solving the ROP problem. This decomposition methodology offers an original paradigm potentially applicable to the design of solution algorithms for a class of problems with functions and parameters that, similar to those of the ROP problem, can be parsed in subsets. The potential merit in decomposing the ROP problem in two stages and the resulting utility of the two-stage solution algorithm are evaluated by performing benefits analysis across specific dimensions related to airport efficiency, as well as stability and robustness analysis of the algorithm output.; Significant delays and resulting environmental impacts are commonly observed during departure operations at major US and European airports. One approach for mitigating airport congestion and delays is to exercise tactical operations planning and control with an objective to improve the efficiency of surface and terminal area operations. As a subtask of planning airport surface operations, this thesis presents a thorough study of the structure and properties of the Runway Operations Planning (ROP) problem. Runway Operations Planning is a workload-intensive task for controllers because airport operations involve many parameters...

‣ Distributed satellite communications system design : first-order interactions between system and network architectures

Underwood, Jennifer E. (Jennifer Elizabeth)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 165 p.; 10868422 bytes; 10877880 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.84905%
Humanity now exists in the midst of the fast-moving Information Age, a period of history characterized by fast travel and even faster information transfer. As data becomes seemingly more valuable than physical possessions, the introduction of exciting applications for communications services becomes ever more critical for the success - and in some cases, survival - of businesses and even nations. While the majority of these innovations have occurred over cable and fiber, a number of the most socially significant have occurred due to the introduction of satellites. Terrestrial fiber and cable systems have a number of advantages, but the extent of their reach and the cost of installation - in terms of both capital and time - favor industrialized nations over more remote and underdeveloped communities. Even as satellites offer the only real chance for ultimate communications ubiquity and true global unity, there remains a significant cost-benefit barrier. Few commercial satellite systems have succeeded economically without first falling victim to bankruptcy. The upfront capital required to implement a satellite communications system is staggering, and historically satellite companies have failed to adequately match capacity and service options to the current and actual future demand. The design process itself is an inherent limiting factor to the achievable cost and performance of a system.; (cont.) Traditionally...

‣ System modeling, analysis, and optimization methodology for diesel exhaust after-treatment technologies; Diesel exhaust after-treatment technologies

Graff, Christopher Dominic
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 230 p.; 11711585 bytes; 11721301 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.84968%
Developing new aftertreatment technologies to meet emission regulations for diesel engines is a growing problem for many automotive companies and suppliers. Balancing manufacturing cost, meeting emission performance, developing competitive engine power, reducing weight and operational costs are all tradeoffs that companies and operators have to resolve for new aftertreatment technologies. However, no single technology has been able to address the wide range of performance and cost objectives in this field. The traditional design philosophy of developing components, optimizing them for particular operation states, and then adding them together into a system may not yield the best solution to this complex problem. Manufacturers may not be able to offer the best balance of performance and cost developing systems in this manner. Two useful product development tools that can address this issue is Systems Architecture and multidisciplinary design optimization (MDO). This thesis develops and exercises a framework for modeling, designing, analyzing, and optimizing of complex diesel exhaust after-treatment systems.; (cont.) The methodology presented addresses the issue of complexity of systems and their components, and how to use systems architecture to develop a modeling technique that allows for flexibility in design...

‣ Robust and decentralized task assignment algorithms for UAVs

Alighanbari, Mehdi, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 158 p.
Português
Relevância na Pesquisa
108.84869%
This thesis investigates the problem of decentralized task assignment for a fleet of UAVs. The main objectives of this work are to improve the robustness to noise and uncertainties in the environment and improve the scalability of standard centralized planning systems, which are typically not practical for large teams. The main contributions of the thesis are in three areas related to distributed planning: information consensus, decentralized conflict-free assignment, and robust assignment. Information sharing is a vital part of many decentralized planning algorithms. A previously proposed decentralized consensus algorithm uses the well-known Kalman filtering approach to develop the Kalman Consensus Algorithm (KCA), which incorporates the certainty of each agent about its information in the update procedure. It is shown in this thesis that although this algorithm converges for general form of network structures, the desired consensus value is only achieved for very special networks. We then present an extension of the KCA and show, with numerical examples and analytical proofs, that this new algorithm converges to the desired consensus value for very general communication networks. Two decentralized task assignment algorithms are presented that can be used to achieve a good performance for a wide range of communication networks. These include the Robust Decentralized Task Assignment (RDTA) algorithm...

‣ A framework for dynamic safety and risk management modeling in complex engineering systems

Dulac, Nicolas, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 338 p.
Português
Relevância na Pesquisa
108.85268%
Almost all traditional hazard analysis or risk assessment techniques, such as failure modes and effect analysis (FMEA), fault tree analysis (FTA), and probabilistic risk analysis (PRA) rely on a chain-of-event paradigm of accident causation. Event-based techniques have some limitations for the study of modem engineering systems. Specifically, they are not suited to handle complex software-intensive systems, complex human-machine interactions, and systems-of-systems with distributed decision-making that cut across both physical and organizational boundaries. STAMP (System-Theoretic Accident Model and Processes) is a comprehensive accident model created by Nancy Leveson that is based on systems theory. It draws on concepts from engineering, mathematics, cognitive and social psychology, organizational theory, political science, and economics. The general notion in STAMP is that accidents result from inadequate enforcement of safety constraints in design, development, and operation. STAMP includes traditional failure-based models as a subset, but goes beyond physical failures to include causal factors involving dysfunctional interactions among non-failing components; software and logic design errors; errors in complex human decision-making; various organizational characteristics such as workforce...

‣ Summary of Research 1996, Department of Aeronautics and Astronautics

Faculty of the Department of Aeronautics and Astronautics, Naval Postgraduate School
Fonte: Office of the Associate Provost and Dean of Research, Naval Postgraduate School. Publicador: Office of the Associate Provost and Dean of Research, Naval Postgraduate School.
Tipo: Relatório
Português
Relevância na Pesquisa
139.11956%
The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or U.S. Government.; This report contains summaries of research projects in the Department of Aeronautics and Astronautics. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

‣ Summary of Research 1997, Department of Aeronautics and Astronautics

Faculty of the Department of Aeronautics and Astronautics, Naval Postgraduate School
Fonte: Office of the Associate Provost and Dean of Research, Naval Postgraduate School. Publicador: Office of the Associate Provost and Dean of Research, Naval Postgraduate School.
Tipo: Relatório
Português
Relevância na Pesquisa
139.11956%
The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or U.S. Government.; This report contains summaries of research projects in the Department of Aeronautics and Astronautics. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

‣ Summary of Research 1998, Department of Aeronautics and Astronautics

Faculty of the Department of Aeronautics and Astronautics, Naval Postgraduate School
Fonte: Office of the Associate Provost and Dean of Research, Naval Postgraduate School. Publicador: Office of the Associate Provost and Dean of Research, Naval Postgraduate School.
Tipo: Relatório
Português
Relevância na Pesquisa
139.11956%
The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government.; This report contains summaries of research projects in the Department of Aeronautics and Astronautics. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

‣ Summary of Research 2000, Department of Aeronautics and Astronautics

Faculty of the Department of Aeronautics and Astronautics, Naval Postgraduate School
Fonte: Office of the Associate Provost and Dean of Research, Naval Postgraduate School. Publicador: Office of the Associate Provost and Dean of Research, Naval Postgraduate School.
Tipo: Relatório
Português
Relevância na Pesquisa
139.11956%
The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government.; This report contains summaries of research projects in the Department of Aeronautics and Astronautics. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

‣ Summary of Research 2001, Department of Aeronautics and Astronautics

Faculty of the Department of Aeronautics and Astronautics, Naval Postgraduate School
Fonte: Office of the Associate Provost and Dean of Research, Naval Postgraduate School. Publicador: Office of the Associate Provost and Dean of Research, Naval Postgraduate School.
Tipo: Relatório
Português
Relevância na Pesquisa
139.11956%
The views expressed in this report are those of the authors and do not reflect the official policy or position of the Department of Defense or the U.S. Government.; This report contains summaries of research projects in the Department of Aeronautics and Astronautics. A list of recent publications is also included which consists of conference presentations and publications, books, contributions to books, published journal papers, technical reports, and thesis abstracts.

‣ Mobile backbone architecture for wireless ad-hoc networks : algorithms and performance analysis

Srinivas, Anand, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 189 p.
Português
Relevância na Pesquisa
108.84869%
In this thesis, we study a novel hierarchical wireless networking approach in which some of the nodes are more capable than others. In such networks, the more capable nodes can serve as Mobile Backbone Nodes and provide a backbone over which end-to-end communication can take place. The main design problem considered in this thesis is that of how to (i) Construct such Mobile Backbone Networks so as to optimize a network performance metric, and (ii) Maintain such networks under node mobility. In the first part of the thesis, our approach consists of controlling the mobility of the Mobile Backbone Nodes (MBNs) in order to maintain network connectivity for the Regular Nodes (RNs). We formulate this problem subject to minimizing the number of MBNs and refer to it as the Connected Disk Cover (CDC) problem. We show that it can be decomposed into the Geometric Disk Cover (GDC) problem and the Steiner Tree Problem with Minimum Number of Steiner Points (STP-MSP). We prove that if these subproblems are solved separately by y- and 5-approximation algorithms, the approximation ratio of the joint solution is y1+6. Then, we focus on the two subproblems and present a number of distributed approximation algorithms that maintain a solution to the GDC problem under mobility. A new approach to the solution of the STP-MSP is also described. We show that this approach can be extended in order to obtain a joint approximate solution to the CDC problem. Finally...

‣ Design and implimentation of a supervisory safety controller for a 3DOF helicopter

Ishutkina, Mariya A. (Mariya Aleksandrovna)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 80 p. + 1 computer optical disc (4 3/4 in.); 1070020 bytes; 1066854 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
109.12169%
This research effort presents the design and implementation of a supervisory controller for a 3DOF helicopter. This safety critical system is used in undergraduate laboratories in the Department of Aeronautics and Astronautics at MIT. There already exists a framework for designing a supervisory safety controller for motions about one axis. It is based on an analytical description of the safety region in state space. However, this framework cannot be easily extended to more complicated systems such as a 3DOF helicopter. In this thesis we present a different approach which uses a real-time simulation of linearized plant dynamics with a feedback law to ensure the system's safety. We describe the development of the system model, the design and implementation of the supervisory safety controller, integration of the safety controller as part of a remote laboratory and its evaluation based on its performance during laboratory exercises.; by Mariya A. Ishutkina.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics, 2004.; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.; Includes bibliographical references (p. 79-80).

‣ MEMS turbomachinery rotordynamics : modeling, design and testing; Microelectromechanical systems turbomachinery rotordynamics : modeling, design and testing

Teo, Chiang Juay
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 350 p.
Português
Relevância na Pesquisa
108.84905%
One of the major challenges encountered for the successful operation of high-power-density micro-devices lies in the stable operation of the bearings supporting the high-speed rotating machinery. This thesis presents the analysis, design, microfabrication, testing and operation of high speed micro-hydrostatic gas bearings for microturbomachinery in power-MEMS applications. A novel turbine driven microbearing test device for demonstrating repeatable high-speed gas bearing operation was designed, microfabricated and tested. The new microbearing test device incorporates numerous features, including a four plena journal bearing feed system enabling both isotropic and anisotropic journal bearing operation, labyrinth seals for reducing rotordynamic coupling, a redesigned turbine for satisfying power requirements, reinforced thrust bearing structural design, a novel rotor fabrication technology for achieving low radial imbalance and a symmetric feed system to avoid rotor sideloading arising from pressure or flow non-uniformities. A rigorous theory is presented to analyze the effects of compressibility in micro-flows (characterized by low Reynolds numbers and high Mach numbers) through hydrostatic thrust bearings for application to microturbomachines.; (cont.) Operating protocols for ensuring thrust bearing static stability have been established and successfully demonstrated on several micro-devices in the MIT Microengine Project. In addition...

‣ Graph-theoretical consideration in the design of complex engineering systems for robustness and scalability

Bounova, Gergana Assenova, 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 114 p.; 6386072 bytes; 6399831 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.84905%
(cont.) and (2) a forward approach which achieves optimality at the start and grows the system using an optimization technique. We systematically compare the two staging techniques in the context of telescope arrays and evaluate the hypothesis that the backward approach is superior for telescope arrays because it incorporates knowledge of the desired future end state of the system. The modelling framework introduced is applicable to various engineering problems susceptible to network representation, including biological systems, telecommunication networks, transportation routes, and space exploration systems.; System optimization for extensibility and robustness is a fundamental challenge of engineering disciplines. Traditional approaches have aimed to optimize cost and performance of a system at a given point in its lifespan. However, as systems evolve with increasing resources and load, system extensibility has to be included in the earliest stages of planning and deployment. In this thesis, we study the staged deployment of large telescope array configurations as an optimization problem subject to cost, performance and network robustness. The LOFAR (LOw Frequency ARray) is the world's largest telescope array, deploying in its full design 25000 antennas over 350kin in diameter in Northern Europe. These are deployed in clusters...

‣ Modeling aviation's global emissions, uncertainty analysis, and applications to policy

Lee, Joosung Joseph, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 134, [6] p.; 12999387 bytes; 13016200 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.84869%
(cont.) fuel burn results below 3000 ft. For emissions, the emissions indices were the most influential uncertainties for the variance in model outputs. By employing the model, this thesis examined three policy options for mitigating aviation emissions. More stringent engine certification standards, continuous descent approach procedures, and derated take-off procedures were analyzed. Uncertainties of the model were carefully accounted for in the fuel burn and emissions scenarios of the policy options. The considered policy options achieved roughly 10-30% reductions in NOx emissions. However, HC and CO emissions rather increased due to higher emissions production rate for the CDA and derated take-off. In addition, the NOx emissions reductions in some cases were not statistically significant given the uncertainty in the modeling tool.; Air travel continues to experience fast growth. Although the energy intensity of the air transport system continues to improve, aviation fuel use and emissions of many pollutants have risen. This thesis focuses on developing, assessing and applying a system model to evaluate global aircraft fuel consumption and emissions, and to examine technological and operational measures to mitigate these emissions. The model is capable of computing how much emissions are produced on a flight-by-flight...

‣ Assessing selected technologies and operational strategies for improving the environmental performance of future aircraft

Mahashabde, Anuja (Anuja Anil)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 89 p.; 4904711 bytes; 5155080 bytes; application/pdf; application/pdf
Português
Relevância na Pesquisa
108.85021%
The aviation industry is expected to grow at a rate of 4-5% in the next 20 years. Such a growth rate may have important impacts on local air quality, climate change and community noise. This work assesses selected technologies and operational procedures aimed at improving the environmental performance of future airplanes. Two different studies are presented: estimating turbine durability benefits from jet engine water injection and evaluating improvements in fuel burn and operating costs from using advanced technology, high bypass ratio engines and varying the design cruise speed. Water injection in commercial airplane engine combustors lowers operating temperatures and can lead to significant reductions in NO, and soot emissions, potentially improving engine hot section life. With increasing fuel prices and possible introduction of emissions trading in the future, fuel burn may become a more critical aircraft design driver. Increasing engine bypass ratio and lowering cruise speed can lead to reduced fuel consumption. The dominant mechanisms of failure in turbine blades are low cycle fatigue, creep and oxidation. The Universal Slopes method is used to evaluate possible fatigue life benefits from water injection for three representative blade materials.; (cont.) For a 67K change in turbine inlet temperature...