Recursos de colección

DSpace at MIT (104.280 recursos)

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Civil and Environmental Engineering - Ph.D. / Sc.D.

Mostrando recursos 1 - 20 de 743

  1. A policy sensitive model of freight demand.

    Chiang, Yu-Sheng
    Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Civil Engineering, 1979.

  2. Relationships between economies of scale and the shape of transportation networks.

    Gordon, Steven Ronald
    Thesis. 1975. Ph.D.--Massachusetts Institute of Technology. Dept. of Civil Engineering.

  3. Exploring interactions between agriculture and air quality on regional to global scales

    Schiferl, Luke D. (Luke Daniel)
    As concern grows over increasing human population and the effects of industrialization on the environment, agriculture and air quality have become important areas of research. Both are vital to human prosperity, determining what we eat and what we breathe. The interactions between agriculture and air quality (defined by ozone and particulate matter (PM) concentrations) are many and often poorly understood. This thesis examines their interactions in two parts. First, we investigate the influence and characterize the importance of the variability in agricultural ammonia emissions on surface inorganic fine PM (PM₂.₅). In a case study, airborne observations indicate that summertime concentrations...

  4. A multiscale computational framework for cement paste

    Palkovic, Steven D. (Steven David)
    Cement paste is the matrix phase in mortar and concrete that exhibits a hierarchical structure spanning orders of magnitude in length scales. These complexities have prevented systematic studies of structure-property relationships. This understanding is necessary to design sustainable cementitious materials that substitute locally available additives for ordinary Portland cement (OPC), while still achieving a mixture with high strength, stiffness and durability. To address this challenge, we develop a multiscale framework connecting molecular details with macroscale performance. This is accomplished through modeling that captures the essential structures and interactions at atomistic (~1 nm), colloidal (~100 nm), and microstructural (~100 [um) length...

  5. Inference and uncertainty quantification for unsupervised structural monitoring problems

    Mohammadi Ghazi, Reza
    Health monitoring is an essential functionality for smart and sustainable infrastructures that helps improving their safety and life span. A major element of such functionality is statistical inference and decision making which aims to process the dynamic response of structures in order to localize the defects in those systems as well as quantifying the uncertainties associated with such predictions. Accomplishing this task requires dealing with special constraints, in addition to the general challenges of inference problems, which are imposed by the uniqueness and size of civil infrastructures. These constraints are mainly associated with the small size and high dimensionality of...

  6. Prediction of instability and ground movements during tunnel construction in non-homogenous conditions

    Founta, Vasiliki
    Advances in tunneling technology, notably in the widespread use of closed-face tunneling boring machines, have reduced risks and greatly increased the productivity of underground construction projects. For shallow tunnels in 'soft ground', instabilities can create collapse mechanisms that propagate to the ground surface, while the prediction and control of tunnel-induced ground deformations remain a key challenge. These problems are especially significant for 'mixed face' conditions, where the tunnel boring machine encounters soils of contrasting mechanical and/or hydraulic properties. This thesis uses finite element simulations to investigate the control of face stability and ground deformations for shallow tunnels in soft ground....

  7. Reliability of shell buckling predictions based upon experimental analysis of plastic models

    Litle, William A. (William Albert)
    by William A. Litle.

  8. Trapdoor experiments on the centrifuge--a study of arching in geomaterials and similitude in geotechnical models

    Iglesia, Geraldo R. (Geraldo Ramiro)
    by Geraldo R. Iglesia.

  9. Membrane-flexural failure modes of square horizontaly restrained R/C slabs.

    Jacobson, Amnon
    Massachusetts Institute of Technology, Dept. of Civil Engineering, Thesis. 1965. Sc. D.

  10. Exploring the absorption properties and direct radiative impact of atmospheric carbonaceous aerosols

    Wang, Xuan, Ph. D. Massachusetts Institute of Technology
    Atmospheric aerosols are important due to their adverse effects on human health and their direct and indirect radiative effects on climate, which are significant and very uncertain factors contributing to global climate change. In estimating the direct radiative effect (DRE), the absorption from carbonaceous aerosols, including black carbon (BC) and brown carbon (BrC, a component of organic aerosol, OA), are highly uncertain. This thesis addresses this uncertainty by combining models and observations to better constrain the optical properties and radiative impact of carbonaceous aerosols. First, a global model simulation (GEOS-Chem) of BC is expanded to separately treat both the aging...

  11. Observations and mechanistic modelling of the role of Aedes mosquitoes in dengue transmission in Singapore

    Seidahmed, Osama M. E. (Osama Mohamed Elmekki)
    Dengue is the most prevalent human arboviral disease in the world with an estimate of 390 million cases per year. The disease is mainly transmitted by two mosquitoes: Aedes aegypti and Ae. albopictus. Despite the continuous efforts to curb the spread of the disease in Singapore, there is an upsurge in dengue epidemics. In this thesis, the role of Aedes mosquitoes in shaping the spatiotemporal patterns of dengue transmission in Singapore is investigated. Field surveys are carried out to study the effect of monsoons on the disease vectors; the impact of urban housing on spatial patterns of dengue transmission is...

  12. Adaptation of granular solid hydrodynamics for modeling sand behavior

    Panagiotidou, Andriani Ioanna
    The development of constitutive models that can realistically represent the effective stress-strain-strength of the soil properties is essential for making accurate predictions using finite element analysis. Currently, most of the existing constitutive models are based on the framework of incrementally-linearized elasto-plasticity. However, most of these models do not typically consider energy conservation and are also phenomenological. This means that they can only be used to predict the behavior/ loading conditions for which they have been developed and that they often employ artificial mathematical formulations. This research proposes an improved constitutive model for sands based on the framework of Granular Solid...

  13. Investigation of the impact of desalination on the salinity of the Persian Gulf

    Ibrahim, Hamed D. (Hamed Dare)
    The Persian Gulf (also known as the Arabian Gulf) is a shallow marginal sea located in a region of Southwest Asia with arid climate. Because of this aridity, evaporation from the Gulf is extremely high (1.84 meters per year) and far exceeds the sum of freshwater inflow to the Gulf, mainly from precipitation and some from river flow. A residual circulation exists between the Gulf and the Indian Ocean such that saline water flows into the Gulf from the Indian Ocean in order to balance the freshwater deficit due to high evaporation rate; and since evaporation only removes freshwater, the...

  14. Carbon fluxes from tropical peatlands : methane, carbon dioxide, and peatland subsidence

    Hoyt, Alison May
    Tropical peatlands in Southeast Asia have sequestered carbon over thousands of years and are an important global carbon stock. In natural peat swamp forests, high water levels inhibit decomposition due to anoxic conditions. However, they are being rapidly deforested and drained, releasing stored carbon to the atmosphere. In this thesis, we investigate the carbon dioxide and methane fluxes from both pristine and degraded peat swamp forests in Borneo using field measurements, modeling and remote sensing. We first study methane fluxes from natural peatlands. We use an isotope-based mass transport model to evaluate the extent of methane production, transport and oxidation....

  15. Field observations and numerical model simulations of a migrating inlet system

    Hopkins, Julia A
    Waves, currents, and bathymetric change observed along 11 km of the southern shoreline of Martha's Vineyard include storm events, strong tidal flows (> 2 m/s), and an inlet migrating 2.5 km in ~7 years. A field-verified Delft3D numerical model developed for this system is used to examine the hydrodynamics in the nearshore and their effect on the migrating inlet. An initial numerical experiment showed that the observed 700 tidal modulation of wave direction in the nearshore was owing to interactions with tidal currents, and not to depth-induced refraction as waves propagated over complex shallow bathymetry. A second set of simulations...

  16. Using polyethylene passive sampling to assess transport of polychlorinated biphenyls (PCBs) between contaminated sediments, water, and biota

    Apell, Jennifer Nicole
    Polychlorinated biphenyls (PCBs), which were a widely used group of chemicals before their manufacture was banned in 1979 in the United States, still contaminate numerous aquatic systems. Although there are ongoing efforts to remediate these sites, our ability to implement effective remediation strategies has been hindered by a limited understanding of how PCBs are transported in the environment as well as how they bioaccumulate into aquatic animals. Investigations of contaminated sites often rely on sediment measurements since PCB concentrations are highest in the sediment phase. However, previous research has shown that sediment concentrations are a poor predictor of contaminant fate...

  17. Optimal land and water allocation to agriculture and hydropower in the Upper Blue Nile basin

    Allam, Mariam M. (Mariam Mohammed Nasr El Din Ibrahim)
    The Nile basin is an ecosystem under stress due to rapid population growth, urgent needs for more efficient utilization of natural resources, potential impacts of climate change, and persistent conflicts between riparian countries on the limited set of resources. This thesis develops a framework for optimal allocation of land and water resources to agriculture and hydropower production in the upper Blue Nile (UBN) basin, which contributes about 60 percent of the Nile river flow. The framework consists of three optimization models that aim to: (a) provide accurate estimates of the basin water budget components, (b) allocate land and water resources...

  18. The significance of ion concentration in the anaerobic biochemical decomposition of acetate

    McCarty, Perry L
    by Perry Lee McCarty.

  19. The significance of ion concentration in the anaerobic biochemical decomposition of acetate

    McCarty, Perry L
    by Perry Lee McCarty.

  20. Activated sludge metabolism of certain quaternary carbon compounds

    Mohanrao, Govindaraju Jagan
    by Govindaraju Jagan Mohanrao.

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