Página 26 dos resultados de 2122 itens digitais encontrados em 0.036 segundos

‣ Validation of the Project Definition Rating Index (PDRI) for MIT building projects; Validation of the PDRI for Massachusetts Institute of Technology building projects

Ubach de Fuentes, Pere-Andreu, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 94 p.; 2536899 bytes; 5083044 bytes; application/pdf; application/pdf
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The thesis presents the work performed to validate the managerial tool called Project Definition Rating Index (PDRI). An improved methodology is presented. This new methodology produces much better linear correlation results between PDRI scores and Cost performance of the projects (R² = 0.957) than previous validation efforts. The projects used for validation purposes have been developed by MIT for its Capital Project effort that started officially in the year 2000. While the results are recommended to be applied to future MIT projects, the author explains how the PDRI works thus facilitating future validation tasks. In the process, the author proposes a modified version of the weights of the PDRI scoring sheet that better adjusts to the definition principles of the tool.; by Pere-Andreu Ubach de Fuentes.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.; Includes bibliographical references (p. 93-94).; This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.

‣ Revenue management under demand driven dispatch

Barocio Cots, Ruben, 1970-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 131 leaves; 8775737 bytes; 8775492 bytes; application/pdf; application/pdf
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by Ruben Barocio Cots.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Aeronautics and Astronautics; and (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1999.; Includes bibliographical references (leaves 129-131).

‣ Algorithmic aspects of high speed switching

Mneimneh, Saadeddine S
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 148 p.; 10667634 bytes; 10667392 bytes; application/pdf; application/pdf
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A major drawback of the traditional output queuing technique is that it requires a switch speedup of N, where N is the size of the switch. This dependence on N makes the switch non-scalable at high speeds. Input queuing has been suggested instead. The introduction of input queuing creates the necessity for developing switching algorithms to decide which packets to keep waiting at the input, and which packets to forward across the switch. In this thesis, we address various algorithmic aspects of switching. We prove in this thesis, that many of the practical switching algorithms still require a speedup to achieve even a weak notion of throughput. We propose two switching algorithms that belong to a family to which we refer in this thesis as priority switching. These two algorithms overcome some of the disadvantages in existing priority switching algorithms, such as the excessive amount of state information that needs to be maintained. We also develop a practical algorithm that belongs to a family to which we refer in this thesis as iterative switching. This algorithm achieves high throughput in practice and offers the advantage of not requiring more than one iteration, unlike other existing iterative switching algorithms which require multiple iterations to achieve high throughput. Finally...

‣ A design methodology for hysteretic dampers in buildings under extreme earthquakes

Fleming, Cody H. (Cody Harrison), 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 69 leaves; 2235352 bytes; 2235155 bytes; application/pdf; application/pdf
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This research proposes a design methodology for hysteretic dampers in buildings under high levels of seismic hazard. Developments in structural materials have led to designs that satisfy strength requirements but are often very flexible. This trend, along with increasingly stringent building performance criteria, suggests a philosophy of controlling structural motion as opposed to merely designing for strength, particularly when related to earthquake design. Included in this thesis is a design algorithm that calibrates stiffness and yield force level, two controlling parameters in the implementation of hysteretic dampers, in order to obtain optimal structural response under two levels of earthquake severity. In addition, a parametric study illustrates the merits and drawbacks of various stiffness and yield force allocations.; by Cody H. Fleming.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.; Includes bibliographical references (leaves 64-65).

‣ Overseas projects finance by international institutions for Japanese construction firms

Kojima, Masashi, 1968-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 100 p.; 6588270 bytes; 6588077 bytes; application/pdf; application/pdf
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This thesis analyzes the relationships between Japanese construction firms, and overseas projects financed by international institutions, such as the World Bank Group, United Nations, ADB, IDB, JBIC, and JICA. Japanese construction firms have as large revenues as other international construction firms in the world. However, the scale of overseas business is quite small compared to that of their domestic activities. Today firms in the Japanese construction industry suffer from the shrinking Japanese construction market. To survive in the future, exploring overseas construction markets is an option for Japanese construction firms. To expand their business overseas, Japanese construction firms should explore the possibilities of increasing contracts financed by international institutions, because payments and contracts for these projects are more secure than those of other financing sources, such as governments of developing countries. As the first step in increasing overseas revenues, projects financed by international institutions become appropriate starts for Japanese construction firms. On the other hand, today the Japanese government is one of the largest sponsors of international institutions. It contributes substantial funds to multilateral financing institutions as well as to Japanese bilateral financing institutions. The government has made extensive contributions to constructing projects in developing countries through these international institutions. However...

‣ PCoord : a decentralized network coordinate system for Internet distance prediction; Decentralized network coordinate system for Internet distance prediction

Lehman, Li-wei H., 1965-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 168 p.; 8052884 bytes; 8073773 bytes; application/pdf; application/pdf
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Several recently emerged Internet services make use of application-level or overlay networks. Examples of such services include overlay multicast, structured peer-to- peer lookup services, and peer-to-peer file sharing. Many of these services could benefit from enabling participating end hosts to estimate their relative network locations within the overlay. In this thesis, we present PCoord, a peer-to-peer network coordinate system for overlay topology discovery and distance prediction. The goal of PCoord is to allow participating peer nodes in an overlay network to collaboratively construct an accurate geometric model of the overlay network topology in a completely decentralized peer-to-peer fashion. We evaluate the PCoord approach through extensive simulations using both real network measurements and simulated topologies. Our simulation results indicate that PCoord can embed hosts in a low dimensional Euclidean model with a small median prediction error.; by Li-wei H. Lehman.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.; Includes bibliographical references (p. 163-168).

‣ Calibration of the demand simulator in a dynamic traffic assignment system

Balakrishna, Ramachandran, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 132 p.; 933436 bytes; 933154 bytes; application/pdf; application/pdf
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by Ramachandran Balakrishna.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2002.; 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. 129-132).

‣ The retrofitting of existing buildings for seismic criteria

Besing, Christa, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 53 leaves; 2120779 bytes; 2120587 bytes; application/pdf; application/pdf
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This thesis describes the process for retrofitting a building for seismic criteria. It explains the need for a new, performance-based design code to provide a range of acceptable building behavior. It then outlines the procedure for retrofitting a building. This procedure begins with acquiring information about the existing building and its surroundings. The building owner or client then needs to work with the design professional to establish an acceptable performance level, or rehabilitation objective. A rehabilitation method must then be selected that determines how the building should be analyzed. The analysis of the building, including suggested rehabilitation strategies, must then be performed. Once the analysis indicates that the building will perform to its prescribed performance level, the rehabilitation strategies must then be implemented. The thesis ends with a description of two buildings that have recently been retrofitted, or are in the processes of being retrofitted. It gives an overview of the selected rehabilitation strategies and the reasoning behind their selection.; by Christa Besing.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.; Includes bibliographical references (leaves 52-53).

‣ Comparison of three widely-used aerodynamic modifications that minimize the impact of wind loads on tall buildings; Comparison of 3 widely-used aerodynamic modifications that minimize the impact of wind loads on tall buildings

Kwok, Raymond Hoi-Kit
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 61, [28] leaves
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For tall buildings, motion caused by wind is usually the most damaging to the lateral support system. As a result, engineers have invented many different methods to limit the motion of the buildings, for example dampers, bracings and outriggers etc. Aerodynamic modification, which is a passive approach, can also be used to reduce the impacts of wind loads. In this thesis, three widely-used aerodynamics modifications are discussed: 1) Shaping the corners of buildings, 2) Addition of openings through buildings and 3) Optimizing cross-sectional shapes of buildings. Comparison based on five criteria related to economy, sustainability, appearance, ease of construction and effectiveness in suppressing response of buildings caused by wind, is performed. With the help of a comparison matrix, it is shown that for a building located in downtown Boston, the method based on optimizing cross-sectional shapes is the best option.; by Raymond Hoi-Kit Kwok.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (leaves 59-60).

‣ Maintenance-based design of concrete parking structures

Stoakes, Christopher D. (Christopher David)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 40 leaves
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The purpose of this study is to determine what type of preventative maintenance for a concrete parking structure will produce the maximum economic benefit. Existing models for concrete deterioration are analyzed for their accuracy in predicting the service lives of concrete structures and a model appropriate for concrete parking structures is selected. The selected model is modified to account for the unique microclimate that is created within a parking structure and used to create deterioration curves that quantify the fraction of a structure deteriorated at a given time. Several preventative maintenance programs that summarize current practice in the repair of concrete parking structures are created. The programs are analyzed using the selected concrete deterioration model and the method of preventative maintenance that maximizes the net present worth of a concrete parking structure is identified.; by Christopher D. Stoakes.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (leaves 37-40).

‣ Economical solutions to blast mitigation on bridges

DeRogatis, Austin (Austin Patrick)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 47 leaves
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Mitigating the energy created from a blast has been a topic of utmost importance in the terrorism-feared world of today. Main targets of concern are passageways that are significant to a specific area, such as bridges. These structures are expensive to construct and vulnerable to explosive loads which is why a cost-effective means of blast mitigation must be researched. There are many aspects of bridges that could be damaged when a blast load is applied. These susceptible areas can be strengthened using new-age, high-strength composite materials to ensure the security of the whole structure. These materials are able to sustain larger loads while dissipating higher amounts of energy when compared to conventional building materials. As a result, the response of the entire structure will be minimized when a blast load is applied. Despite the fact that these composites cost more than typical materials, the increase in project cost could be minimized by limiting the use of these high-strength materials for only the critical areas of the bridge. Other cost effective solutions to blast mitigation occur in the preliminary design phase. Eliminating all pressure-amplifying areas would save members and connections should a blast occur. Also, designing a bridge with high vertical clearances above areas of excessive boat traffic would also minimize the resultant forces and stresses from an explosion.; by Austin DeRogatis.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ Base isolation case study

Ching, Kenneth A. (Kenneth Apostol)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 52 leaves
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The primary objective of this thesis is the introduction of the current code, ASCE 7-05 into the base isolation design and the analysis of base isolation response due to seismic forces. An eight story irregular structure is modeled using SAP2000 structural program. The time history of Northridge earthquake is used as a seismic forcing function of the structure. The base isolator is designed by using the principle of bilinear modeling. Therefore, the base isolation system is analyzed using the non-linear time history analysis. The response of the isolation system is analyzed, and especially its hysteresis loop. Results show that the inputted energy of the seismic forces is dissipated by hysteretic and modal damping.; by Kenneth A. Ching.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2008.; Includes bibliographical references (leaf 51).

‣ The development of a selection criteria model for the type of seismic retrofitting scheme applicable to Philippine buildings

Angeles, Kathryn Patricia V. (Kathryn Patricia Velayo)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 53 leaves
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The Philippine Archipelago lies in a highly sensitive position in the Asian continent, named the Pacific "Ring of Fire" and it is one of the most seismically active and disaster prone areas in the world. In the Philippines, where a percentage of the buildings are structurally out of date, seismic retrofitting is of utmost importance. This study presents an overview of various rehabilitation strategies such as Seismic Isolation, Passive Energy Dissipation and Active Systems. An analysis of the rehabilitation process given by the Federal Emergency Management Agency is presented. The most significant factor affecting the modifications is the level of seismic activity in the Philippines. The direct implication of such a level of seismicity is directly seen in that the third phase of the rehabilitation process is Systematic Rehabilitation. Another direct effect is in the method of component analysis for the Philippine setting, which calls for the use of nonlinear analysis methodologies. This rehabilitation process was modified to provide a selection criteria model that was suited to meet the Philippine setting.; by Kathryn Patricia V. Angeles.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering...

‣ Design optimization of cable-stayed bridges

Bessas, Georgios
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 120 p.
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The goal of this thesis is to achieve a basic understanding of cable-stayed systems. Issues to be treated are the diachronic evolution of cable-stayed bridges, including the advantages, the limitations and the basic design concepts of these indeterminate systems. During this project, the design of typical cable-stayed bridges is optimized with computer-based simulation capabilities contained within the SAP2000 computer software system. The analysis strategy starts with the analyses of ten different 3D models under earthquake loading. The numerical results of the analyses form the basis for the optimization of the bridges' designs. This study has indicated that for the specific design examined, the optimum cable spacing is: 13.2m and 12.39m for equivalent steel decks with bending rigidities of IEequiv=3.25*105 kN*m2 and IEequiv=2.25*105 kN*m2 respectively. The procedure also identified the advantage of using bracing on the top half of the towers. The final part of this thesis concerns a case-study of the Rion-Antirion cable-stayed bridge. This includes the creation of an appropriate computer model as well as the proper examination of the quasi-static behavior of the bridge.; by Georgios Bessas.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ Modeling of nearshore hydrodynamics for sediment transport calculations

Gonzalez-Rodriguez, David, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 133 p.; 5324981 bytes; 5324767 bytes; application/pdf; application/pdf
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This thesis analyzes and improves Tajima's (2004) nearshore hydrodynamic model. Tajima's simple model accurately predicts long-shore sediment transport along long, straight beaches, while cross-shore transport predictions differ from observations. A better prediction of cross-shore transport requires improvement of the hydrodynamic model. We first contrast Tajima's model with other hydrodynamic models. To improve the characterization of incident waves, we examine a number of joint probability distributions of wave heights and periods. These distributions are then used to develop a probabilistic wave-by-wave hydrodynamic description based on Tajima's monochromatic wave model. We derive the model governing equations for the unsteady case and detail their numerical implementation. This unsteady model is applied to study the effect of a wave beat normally incident on a plane sloping beach. We use this case to illustrate the relevance of the unsteady generalization to sediment transport calculations.; by David Gonzalez-Rodriguez.; Includes bibliographical references (p. 129-133).; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.

‣ Simulation of the dynamic response of a damped taught string

Favennec, Hervé
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 54 leaves
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Marine pipeline are facing new issues involved by the increase of the depth of exploited oil and gas reservoirs. This thesis discusses the changes in the dynamic behavior of marine pipelines and proposes a simple simulation based on a taut string. The dynamic response of the taut string is modeled using two techniques, the Green's function and the modal superposition. This study demonstrates that the modal superposition technique, commonly used to assess the dynamic behavior of marine pipelines, is still valid under certain conditions.; by Hervé Favennec.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (leaf 44).

‣ How to prepare an airport for the Olympic Games? : transportation of the Olympic Family Members

Kassens, Eva
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 112 leaves; 5791258 bytes; 5804776 bytes; application/pdf; application/pdf
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This thesis describes and assesses the preparation of Athens International Airport for and its performance during the Olympic Games in 2004. The analysis includes infrastructural modifications made and organizational restructuring processes undertaken. It also describes the rationale behind some of the decisions, as well as the implementation of certain specific measures. The time-frame of the preparations stretches from the very strategic beginnings, the forecasting, to the actual management of passenger flows during the Games. The focus of the thesis is on the transportation of the Olympic Family Members, i.e. athletes, sponsors, and VIP's. Finally, the thesis incorporates lessons learned from the Athens Olympic Games.; by Eva Kassens.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.; Includes bibliographical references (leaves 111-112).

‣ Analysis of sustainable water supply options for Kuwait

Murtaugh, Katharine A. (Katharine Ann)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 139 leaves; 8829267 bytes; 8835083 bytes; application/pdf; application/pdf
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This thesis considers several options for improving the sustainability of Kuwait's water supply system. The country currently relies heavily on desalination and brackish groundwater extraction. The options considered for increasing the flux of potable water into Kuwait include expanding the desalination capacity, importing water from other countries, expanding the uses of reclaimed wastewater, and rainfall harvesting. Options for water storage are also considered, including both aquifer and surface systems. Case studies are presented which demonstrate the potential for indirect potable use of Kuwait's highly purified wastewater, and the importance of a storage reservoir as part of such a system. In order to assess the feasibility of rainfall harvesting, a model was constructed to simulate the runoff processes in the Rawdhatain drainage basin in northern Kuwait. Due to the coarse resolution of the input data, reasonable results could not be obtained using the input parameters gathered from available data.; (cont.) However, through sensitivity analysis, it was discovered that relatively minor variations in soil properties throughout the watershed could produce significant volumes of runoff during extreme rain events. Storage was considered for the small lens of fresh groundwater beneath the Rawdhatain basin or in a surface reservoir constructed in the drainage depression there. All of these options should continue to be considered as Kuwait attempts to expand its water supply in a sustainable manner...

‣ Effects of adding wash tower effluent to Ano Liossia landfill to enhance bioreaction c by Olympia Galenianou.

Galenianou, Olympia
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 45 leaves; 9163117 bytes; 9162799 bytes; application/pdf; application/pdf
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A theoretical study was performed on the effects of adding sulfate-rich wash tower effluent from the Athens hospital waste incinerator to the Ano Liossia landfill of Athens. The method of mass balance was used to examine the production of leachate, the generation of methane, and the reduction of sulfates into sulfides. The water mass balance was performed using the method of Thornthwaite and the result indicated that the leachate collection facility at Ano Liossia landfill would be able to handle the additional leachate. The hydrocarbon-methane mass balance was performed using the EPA's LandGEM model which is based on first-order decomposition of the waste. A 26% difference between the generation of methane in a conventional landfill and a bioreactor landfill was predicted. Finally, a first-order model was developed by analogy to the LandGEM model to study the reduction reaction of sulfates into sulfides. The amount of hydrogen sulfide produced from solid waste disposed in the landfill dominated the amount of hydrogen sulfide produced from the additional wastewater.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.; Includes bibliographical references (leaves 39-40).

‣ Hybrid vehicle-centric route guidance

Farver, Jennifer M. (Jennifer Margaret), 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 228 p.; 12468164 bytes; 12477779 bytes; application/pdf; application/pdf
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This thesis proposes a hybrid route guidance system in which predictive guidance is generated in a centralized layer and revised in a reactive, decentralized layer that resides on-board the vehicle. This hybrid approach is intended to improve guidance quality by balancing the ability of the centralized layer to generate consistent guidance with the ability of the decentralized layer to respond rapidly to incidents. Centralized guidance is computed using a rolling-horizon Dynamic Traffic Assignment routine based on the Method of Successive Averages. This guidance is disseminated to equipped vehicles in the form of prescribed paths, which may be subsequently revised by an on-board decentralized layer. This decentralized layer revises only the local portion of the vehicle's path in order to limit the potential negative impact of its myopic reactive algorithm. The layer uses a simple splitting algorithm in order to heuristically balance demand on alternate paths. Both layers utilize data collected by guided vehicles. The centralized layer uses position data from guided vehicles. The decentralized layer uses local arc travel time data which is shared among guided vehicles.; (cont.) This approach follows the vision of a vehicle-centric route guidance system whose design is focused on the vehicle...