Massachusetts Institute of Technology. Dept. of Civil Engineering. Thesis. 1974. M.S. / MICROFICHE COPY ALSO AVAILABLE IN BARKER ENGINEERING LIBRARY. / Bibliography: leaves 38-40. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993. / Vita. / Includes bibliographical references (leaves 209-214). / by Peter W. Mueller. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 175-178). / The future availability of the natural resources (water and land) needed for food production is highly uncertain. Evidence shows diminishing natural resources and growing food demand throughout many parts of the world. China is one of the countries that face the challenge of managing its finite water and land resources to support their population. Difficulties mainly arise from: (1) the geographic mismatch between the location of water resources and available land; (2) a large and growing number of population; and (3) limited natural resources per capita. This thesis presents a systematic approach to evaluate the effects of water and land constraints on food production and applies it to China as a case study. Based on the basic principle of water and land balance, crop resource requirements, and per capita consumption, the assessment of natural resources limitations on food production can be formulated into an optimization model, with the objective function maximizing the number of people fed subject to resource constraints. This formulation makes it possible to systematically and efficiently evaluate the effects of natural resource constraints for such a complex and large scale study regions such as China. Even though our approach is based on the basic principle, we incorporate several significant features into the model to realistically represent the spatial and temporal heterogeneity in climate, land use, and crop requirements. Our analysis is conducted at a detailed spatial resolution of 0.5' by 0.5', includes water movement at the same resolution, accommodates the mixture of crops in people's diet, and distinguishes irrigated from rain-fed agriculture. Our optimization model presents an average long term analysis. The model is developed and calibrated to reproduce long-term observed conditions during the nominal period of 1990- 2000. We then use the model together with globally and locally available data to make future predictions of China's food production capacity during the future period of 2046-2065. These future predictions include the impacts of the South-to-North Water Diversion project and projected climate change. The future climate scenarios are taken from the general circulation model predictions and represent diverse seasonal and regional patterns. Regionally, land is a limiting factor in the south, while water is a limiting factor in the north. Our results suggest that irrigation and multiple-cropping are keys in enhancing China's food production capacity to support increasing population. The spatial and seasonal distribution of rainfall changes is critical for agriculture in meeting future food requirements under climate change. / by Piyatida Hoisungwan. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (v. 3, p.1198-1258). / The sorption behaviors of hydrophobic organic compounds (HOCs) in sediments were investigated using pyrene. Native pyrene desorbed slowly, taking from weeks to months to equilibrate. The end-point data suggested that, at nanogram-pyrene-per-liter porewater levels, sorption was much stronger than conventionally expected. The non-linearity of the isotherm may indicate physical occlusion of native sorbate and/or sorption onto micropore surfaces of char/charcoal. Between 30-70% of the native pyrene may be occluded. Conceptual pictures for both hypotheses were presented with supportive evidence from experiments and literature. Analysis of experimental and literature data suggested logKoc (organic-carbon normalized partition coefficient) and logKBC (black-carbon normalized partition coefficient) values were fairly constant across different geosorbents (around 4.5-5.7 and 5.6-6.3, respectively), while the non-linearity exponent varied substantially. This may explain the orders of magnitude scatter in logKoc's and logKBC's reported in recent reviews. An a priori non-linear numerical model based on Intra-particle Porewater Diffusion (IPD) was constructed and successfully predicted the desorption kinetics of native pyrene. Fitted kinetic parameters correlated with system and sorbate/sorbent properties. This suggested the empirical approach can be replaced by the a priori model and the diverse HOC desorption rates in the literature can be reconciled if relevant physicochemical properties are known. The regional fate of pyrene in Boston Harbor was evaluated with a box model using derived kinetic and equilibrium properties. Realistic predictions can be obtained when assuming pseudo steady state conditions, but not equilibrium partitioning, for the bed sediment and the water column. Furthermore, model results and literature evidence suggested that sediment resuspension may be a significant mobilization mechanism for sedimentary HOCs in estuaries and harbors. A new BC quantification method based on energy dispersive X-ray spectroscopy (EDX) was developed. The method identified/quantified Organic Carbon (OC) or Black Carbon (BC) by analyzing the elemental ratios of C, N, and 0 of the sample. Agreeable OC/BC estimates on a variety of carbonaceous materials were obtained using the method. The good analytical potential of the method warranted further exploration and methodological refinement. This study has great implications for the sequestration and bioavailability of HOCs in the environment. / by Dave T. F. Kuo. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 91-92). / Masonry is a fundamental building material that is used for a significant proportion of structures across the world, many of which lie in potentially hazardous environments. While masonry naturally has poor performance under lateral loads which lead to tensile forces, many of these structures lie within highly seismic regions. As a result, guidelines have been established to ensure structural integrity in case of a disaster, yet these are based on assumptions that limit the accuracy of these tools, and fail to address the needs of traditional non-engineered masonry environments. This thesis begins with an overview of seismic hazards and the effects they have on the structural design of unreinforced masonry. The failure modes of masonry structures are discussed, followed by an evaluation of reinforcement techniques and their effects on structural behavior. A comparison of quasi-static and dynamic analytical methods, and their conditional accuracies provides an argument towards a simplified approach to masonry modeling that is appropriate for engineering applications. The methodology of this thesis applies a quasi-static tilt analysis through the physical modeling of masonry structures with discrete scaled masonry blocks. The results of initial experiments support the validity of this model in representing predicted masonry behavior, leading to a series of experiments on a selection of masonry designs and the analysis of reinforcement modeling techniques. Further research can expand on the structural designs and reinforcement materials, and use the physical models in more complex load applications, for example, with a shaking table. / by Daniel D. Jimenez. / M.Eng.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000. / Includes bibliographical references (p. 173-174). / by Nicolas Aplincourt. / S.M.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1996. / Includes bibliographical references (leaves 314-316). / by Paolo Sammarco. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2012. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 87-90). / The number of aging commercial aircraft in service is steadily increasing as airlines continue to extend the life of their aircraft. Aging aircraft are more susceptible to fatigue and corrosion and require more frequent and intensive inspections and maintenance, which is a financial drain on operators. One way to improve the economics and safety of commercial aircraft is through implementation of a structural health monitoring (SHM) system. An ideal SHM would be able to give be capable of indicating damage type, location, severity, and estimate the remaining life of the structure while the structure is in use. This paper is an overview of how SHM can be applied in commercial aviation including discussion of requirements, implementation, challenges, and introducing several possible SHM systems. The SHM systems introduced in this paper are: vibration based monitoring, fiber optic sensors, and high frequency wave propagation techniques including acoustic emission, ultrasonic, Lamb waves, piezoelectric and MEMS actuator/sensors. The limitations and challenges inhibiting introduction of SHM to industry and recommendations for the future are also discussed. / by Nicholas Brigman. / M.Eng.

Thesis: S.M. in Transportation, Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 175-179). / Service reliability is a major concern for public transportation agencies. Transit services experience natural variability in scheduled service, due to factors such as traffic congestion, irregular demand, multi-route and branching corridors, and operator behavior. This variability leads to irregular headways, resulting in longer passenger waits and decreased effective capacity as gaps in service form. Real-time control strategies allow controllers to intervene at terminals and en route to regulate headways and improve performance. This research tests the effectiveness of holding control strategies on the Massachusetts Bay Transportation Authority (MBTA) Green Line in Boston, a complex, four-branch light rail line. A simulation model is developed to estimate and compare the benefits of different schedule-based and headway-based holding strategies. Dispatching trains at terminals to target headways is found to minimize wait time, and the addition of en route holding improves service further, albeit slightly. The simulation results inform the design of a field experiment, in which headway-based dispatching is implemented at a Green Line branch terminal. Terminal personnel are provided with tablet computers showing departure times optimized by an even-headway policy. When optimized departure times are adhered to, peak-hour headway variability is reduced by 40%. The average wait is shortened by 15% (30 seconds), and the 90th percentile wait is shortened by 21% (90 seconds). Compliance with the recommended departure times in the experiment was hampered by various human factors and station features. During the experiment, only 49% of trips left within 45 seconds of the departure times recommended by the algorithm. These results show that adopting headway-based dispatching at terminals promises significant benefits to service and passengers if operational changes are accompanied by improved supervision practices. This research fully supports the idea that transit agencies, such as the MBTA, should allocate supervisory resources for high-frequency services to prioritize terminal headway control versus en route and schedule-based strategies. / by Joshua Javier Fabian. / S.M. in Transportation

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1993. / Includes bibliographical references (leaves 146-149). / by John F. Romps, III. / M.S.