DSpace at MIT
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Civil and Environmental Engineering - Ph.D. / Sc.D.
Mostrando recursos 1 - 20 de 590
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Risks and decision making in development of new power plant projects - Kristinsdottir, Asbjorg
Power plant development projects are typically capital intensive and subject to a complex network of interconnected risks that impact development's performance. Failure to develop a power plant to meet performance constraints can come at great cost to the developer and other stakeholders involved. In order to develop an investment strategy plan based on their risk appetite, and manage risks effectively, developers must be able to identify and analyze project opportunity risks. This dissertation is motivated by the need to study the nature and impact of risks on a power plant development project, and to demonstrate how proper management of those...
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Nanomechanical coupling of mechanomutable polyelectrolytes - Cranford, Steven W
Nanotechnology has advanced to the point where almost any molecular functional group can be introduced into a composite material system. However, emergent properties attained via the combination of arbitrary components - e.g., the complexation of two weak polyelectrolytes - is not yet predictive, and thus cannot be rationally engineered. Predictive and reliable quantification of material properties across scales is necessary to enable the design and development of advanced functional (and complex) materials. There is a vast amount of experimental study which characterize the strength of electrostatic interactions, topology, and viscoelastic properties of polyelectrolyte multilayers (PEMs), but very little is known...
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Analytical and experimental studies of plant-flow interaction at multiple scales - Luhar, Mitul
Across scales ranging from individual blades to river reaches, the interaction between water flow and vegetation has important ecological and engineering implications. At the reach-scale, vegetation is often the largest source of hydraulic resistance. Based on a simple momentum balance, we show that the resistance produced by vegetation depends primarily on the fraction of the channel cross-section blocked by vegetation. For the same blockage, the specific distribution of vegetation also plays a role; a large number of small patches generates more resistance than a single large patch. At the patch-scale, velocity and turbulence levels within the canopy set water renewal...
4.
Seawater circulation in coastal aquifers : processes and impacts - Karam, Hanan Nadim
This thesis explores the subterranean domain of chemical cycling in coastal oceans abutting permeable aquifers, where transport through sediments is dominated by advection, rather than diffusion. We investigate the mechanisms by which seawater circulates in the subsurface over a range of spatio-temporal scales, and the chemical reactions to which this circulation is coupled. Seawater circulation in coastal aquifers is driven by salinity variations in pore water as well as by the effects of temporally variable forcings at both terrestrial (variable recharge) and marine (tides, waves and secular sea level changes) boundaries. It is coupled to the transport of biogeochemically reactive...
5.
Automated security analysis of payment protocols - Huang, Enyang
Formal analyses have been used for payment protocol design and verification but, despite developments in semantics and expressiveness, previous literature has placed little emphasis on the automation aspects of the proof systems. This research develops an automated analysis framework for payment protocols called PTGPA. PTGPA combines the techniques of formal analysis as well as the decidability afforded by theory generation, a general-purpose framework for automated reasoning. A comprehensive and self-contained proof system called TGPay is first developed. TGPay introduces novel developments and refinements in the formal language and inference rules that conform to the prerequisites of theory generation. These target...
9.
The natural and industrial cycling of indium in the environment - White, Sarah Jane O'Connell
Indium is an important metal whose production is increasing dramatically due to new uses in the rapidly growing electronics, photovoltaic, and LED industries. Little is known, however, about the natural or industrial cycling of indium or its environmental behavior. Industrial emissions of indium are already larger than natural emissions. A review of the literature suggests that metal smelting and coal burning are the primary industrial sources of indium to the environment, while releases from the semiconductor and electronics industries are small at present. This scenario may change with the rapid growth of indium use in the electronics and semiconductor industries....
10.
ThermoSolar and photovoltaic hybridization for small scale distributed generation : applications for powering rural health - Orosz, Matthew S. (Matthew Sándor), 1977-
The problem of provisioning a remote health clinic or school with electricity, heating and cooling (trigeneration) is considered from an engineering design and optimization standpoint. A baseline technical-economic review of existing options is performed, and a novel alternative is proposed: micro-Concentrating Solar Power (CSP), featuring an Organic Rankine Cycle (ORC) using repurposed HVAC scroll compressors as expanders. The design of the [mu]-CSP technology is informed by a semi-empirical steady state multi-physics sizing and performance model (SORCE) which predicts system output, efficiency, and specific costs as a function of geoposition. Empirical validation of key mechanical and electrical components is performed to...
11.
The effect of geometry and topology on the mechanics of grid shells - Malek, Samar R. (Samar Rula)
The use of grid shell structures in architecture and structural engineering has risen in the past decade, yet fundamental research on the mechanics of such structures is lacking. Grid shells are long span structures comprised of a lattice of single layer members forming a curved surface. Grid shells can be made of a wide range of materials from steel to wood. They have potential to be used in readapting existing spaces or in new aesthetically pleasing structures. By studying their mechanics, engineers can be more effective at the schematic phase of design so that the potential of grid shells can...
12.
Reduced-order modeling for ensemble real-time estimation and control - Lin, Binghuai
Efficient exploitation of subsurface resources requires better understanding of subsurface physical properties as well as optimization of control strategies. Advances in technology have created the possibility of providing real time measurements of subsurface conditions. These measurements can be used to reduce uncertainty in the description of subsurface conditions, and combining uncertainty quantification and control optimization leads to improved management of subsurface resources through the closed-loop control framework. The ensemble closed-loop control utilizes an ensemble representation to describe complex probabilistic distributions of uncertain model parameters. To reduce the computational burden and make it feasible to apply the ensemble closed-loop control to...
13.
Debonding in bi-layer material systems under moisture effect : a multiscale approach - Lau, Tak-bun, Denvid
Bi-layer material systems are found in various engineering applications ranging from nano-scale components, such as thin films in circuit boards, to macro-scale structures such as adhesive bonding in aerospace and civil infrastructure applications. They are also found in many natural and biological materials such as nacre or bone. One of the most human-related applications of bi-layer material systems is the artificial tooth involving the bonding between the natural tooth and the metal cap glued with a polymer based material. The structural integrity of a bi-layer system depends on properties of both the interface and the constitutive materials. In particular, interfacial...
14.
The effects of sample disturbance on preconsolidation pressure for normally consolidated and overconsolidated clays - Kontopoulos, Nikolaos S. (Nikolaos Stefanos)
Sample disturbance has always been a particularly challenging topic in Geotechnical Engineering exercise. The effect and importance of disturbance on stress-strain history and undrained shear strength of soft clays are well stated in the literature over the past decades. However, in practice, few qualitative methods are used even in the most complex engineering projects. Furthermore, there is not a widely accepted, quantitative method in order to assess sample disturbance and treat the lab engineering values to match the "in-situ" properties of the soil. This research consists of a systematic review of the methods available to estimate preconsolidation pressure and sample...
15.
Development of a combined multi-sensor/signal processing architecture for improved in-situ quantification of the charge balance of natural waters - Mueller, Amy, 1980-
This thesis details the design, implementation, and testing of a new electrochemical instrument for the in situ measurement of both major and environmentally relevant minor ions in fresh waters, namely Na+, K+, Ca2+, Mg2+, NH+4 , Cl-, NO-3 , and SO2-4 . The instrument is built on a hybrid multi-probe / signal processing architecture and is implemented using commercial sensor hardware (primarily ion-selective electrodes (ISEs)) paired with a novel neural network processor designed to take advantage of a priori chemical knowledge about the system. Adaptation of this architecture to in-situ conditions and quantification of relatively minor ions required overcoming a...
16.
Low-Cost, Passive UHF RFID Tag Antenna-Based Sensors for Pervasive Sensing Applications - Bhattacharyya, Rahul
In the future, large-scale sensor deployment would enable many areas such as infrastructure condition monitoring and supply chain management. However, many of today's wireless sensor technologies are still too expensive to meet this need. Radio Frequency IDentification (RFID) offers good potential for the development of pervasive sensors: RFID tags have a proven track record of large-scale, highly integrated deployment for object identification in the retail and consumer goods industry. Furthermore, the last decade has seen much progress in making RFID a reliable, standardized wireless communication medium with the ability to mass produce low-cost RFID tags. My thesis introduces the concept...
17.
Hysteresis and urban rail : the effects of past urban rail on current residential and travel choices - Block-Schachter, David
Cities are endowed with and accumulate assets based on their unique histories, which in turn define the choice set of the present. These assets range from the natural-sheltered ports, fertile land--to the constructed--concrete and cement, institutions and people. This dissertation examines the effects of one of these assets, urban rail, on residential location and travel behavior, from the era of horsecars and streetcars to the present in Boston. It explores the hysteretical effects of past access to rail--the extent to which the urban system retains the impacts of rail even when it no longer exists. Current density and travel behavior...
20.
Phytoplankton in flow - Durham, William McKinney
Phytoplankton are small, unicellular organisms, which form the base of the marine food web and are cumulatively responsible for almost half the global production of oxygen. While phytoplankton live in an environment characterized by ubiquitous fluid motion, the impacts of hydrodynamic conditions on phytoplankton ecology remain poorly understood. In this thesis, we propose two novel biophysical mechanisms that rely on the interaction between phytoplankton motility and fluid shear and demonstrate how these mechanisms can drive thin phytoplankton layers and microscale cell aggregations. First, we consider 'thin phytoplankton layers', important hotspots of ecological activity that are found meters beneath the ocean...
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