Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1996. / Includes bibliographical references (leaves 173-188). / by Adil Najam. / M.S.

Thesis (S.M. in Transportation)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2010. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 121-122). / This thesis studies the integration of public transportation systems, focusing on the development of strategies to implement such goal for networks operated by different service agencies. A literature review on public transportation integration is initially presented, its main conclusion being that, even though many studies have identified a range of integration practices, only a few describe strategies to implement and materialize them in a multi agency context. The province of Gipuzkoa, in the Basque Country of Spain, is used as a case study to develop strategies which facilitate integration among different transit agencies. After describing the current services of the different agencies, two specific cases of integration are analyzed: fare integration between interurban and urban bus services in Donostia-San Sebastian and connectivity improvements between rail and bus services. The first case is analyzed quantitatively in great detail, given the availability of smartcard data describing the current utilization of the systems. This critical component of the work was possible thanks to the fare media integration agreement reached previously by the two agencies. The processing of the data on the use of the smartcard, reveals that not only transferring passengers are benefiting from the integration, which was the original intent of the agreement. In fact, regular urban passengers are also migrating to the interurban card due to a supposedly higher user convenience. Given the revenue sharing agreement subscribed by the two agencies, this migration implies unexpected high costs for the interurban agency. Since this agreement could obstruct further integration improvements, alternative agreements are proposed and evaluated. A recommendation is made for a new agreement that would lead to either reduced or free transfers without imposing high cost on either agency, while increasing their incentive to pursue further integration practices. In the second case, a connectivity improvement plan between rail and bus services is proposed. This plan prioritizes the available connectivity improvements not only according to their cost-benefit ratio, as the process regularly used by a single agency, but also with respect to whether the improvement could be implemented by a single agency or whether it requires inter agency negotiations. Further research on integration is proposed for Gipuzkoa based on the expected future integration of rail services into the current smartcard used in the bus system. / by Julián Andrés Gómez Gélvez. / S.M.in Transportation

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1996. / Includes bibliographical references (p. 133-134). / by James M. Nissenberg. / M.S.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1995. / Includes bibliographical references (leaves 140-144). / by Ming-Hung Lin. / M.S.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2011. / Cataloged from PDF version of thesis. / Includes bibliographical references (p. 253-255). / Finite Element Methods hold promise for modeling the behavior of an unsaturated soil specimen subjected to bender element agitation. The immediate objective of this research project is to reproduce a bender element test using Abaqus Finite Element Software assuming elastic and isotropic conditions. Extensive compressions were made of bender element testing of unsaturated Ticino Sand specimens uniaxially compressed and the Abaqus Finite Element Method program simulation. The research determined that the mesh resolution of a numerical analysis are optimal at a resolution of a twentieth of the shear wavelength and the integration time step has a negligible effect on the observed wave velocity. Moreover, it is possible to reproduce an uniaxially stressed bender element experiments of unsaturated Ticino sand in an Abaqus Finite Element Method program with relatively minimal error of the body wave velocity measurements if the source receiver distance is beyond two shear wavelengths and the reflected signals from the boundaries are suppressed. / by Sean Johnson. / S.M.

Thesis (S.M.)--Massachusetts Institute of Technology, Department of Civil and Environmental Engineering, 2013. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Widespread use of petrochemicals often leads to accidental releases in aquatic environments, occasionally with disastrous results. Recent advances in the understanding of selectively wetting surfaces have led to the development of functionalized steel meshes with hydrophobic and oleophilic surfaces. These meshes can perform oil/water separation in situ, continuously, via capillary action. The goal of this study is to determine the potential of hydrophobic meshes as oil spill recovery devices. A fabrication method was developed using steel mesh dip-coated in a hot solution of low-density polyethylene (LDPE) in xylene. The mesh gained a rough, hydrophobic coating of LDPE, with tunable pore sizes and surface roughness. The coating was characterized using microscopy techniques and contact angle analysis, in order to identify surface features relevant to oil/water separation. Oil was found to persistently wet the mesh, attenuating any effects from roughness. Next, a key performance metric, the water breakthrough pressure, was predicted using a modified version of the Young-Laplace equation incorporating an unpinned meniscus. The model was successful for meshes with pore radii between 7 - 220 tm, which could hold back up to 40 cm of water. Finally, a bench-scale apparatus was built to test the oil permeate flux at steady state under capillary-driven flow. The mesh successfully recovered oil from the surface of a pool of water, with less than 1% water recovered by mass, with a representative flux of 1 L-m-²-s. These results were used to discuss implications for the feasibility of field-scale devices. / by Daniel P. Prendergast. / S.M.

Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 1998. / Includes bibliographical references (p. 148-151). / by Seiji Naito. / M.S.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004. / Includes bibliographical references (p. 219-230) and index. / Wavelets and filter banks have revolutionized signal processing with their ability to process data at multiple temporal and spatial resolutions. Fundamentally, continuous-time wavelets are governed by discrete-time filter banks with properties such as perfect reconstruction, linear phase and regularity. In this thesis, we study multi-channel filter bank factorization and parameterization strategies, which facilitate designs with specified properties that are enforced by the actual factorization structure. For M-channel filter banks (M =/> 2), we develop a complete factorization, M-channel lifting factorization, using simple ladder-like structures as predictions between channels to provide robust and efficient implementation; perfect reconstruction is structurally enforced, even under finite precision arithmetic and quantization of lifting coefficients. With lifting, optimal low-complexity integer wavelet transforms can thus be designed using a simple and fast algorithm that incorporates prescribed limits on hardware operations for power-constrained environments. As filter bank regularity is important for a variety of reasons, an aspect of particular interest is the structural imposition of regularity onto factorizations based on the dyadic form uvt. We derive the corresponding structural conditions for regularity, for which M-channel lifting factorization provides an essential parameterization. As a result, we are able to design filter banks that are exactly regular and amenable to fast implementations with perfect reconstruction, regardless of the choice of free parameters and possible finite precision effects. Further constraining u = v ensures regular orthogonal filter banks, / (cont.) whereas a special dyadic form is developed that guarantees linear phase. We achieve superior coding gains within 0.1% of the optimum, and benchmarks conducted on image compression applications show clear improvements in perceptual and objective performance. We also consider the problem of completing an M-channel filter bank, given only its scaling filter. M-channel lifting factorization can efficiently complete such biorthogonal filter banks. On the other hand, an improved scheme for completing paraunitary filter banks is made possible by a novel order-one factorization which allows greater design flexibility, resulting in improved frequency selectivity and energy compaction over existing state of the art methods. In a dual setting, the technique can be applied to transmultiplexer design to achieve higher-rate data transmissions. / by Ying-Jui Chen. / Ph.D.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007. / Includes bibliographical references. / Widespread arsenic contamination of groundwater has become a major concern in Bangladesh since the water supply, particularly in rural areas, is heavily dependent on groundwater. However, relative to the extent of research on biogeochemical processes of arsenic mobilization, very little work has been conducted to understand the complex transient dynamics of groundwater flow, and the transport of arsenic and other solutes that control its mobility in the area. A detailed three-dimensional hydrological model of our study area in Munshiganj indicates that: (1) the shallow aquifer acts primarily as a conduit for flow from ponds and rice fields to irrigation wells and rivers; (2) most inflow to the aquifer occurs during the dry season, and monsoon contributes relatively little to the inflow since the aquifer storage is small; (3) since the increase in irrigation pumping and pond construction have changed the groundwater flow dynamics, arsenic concentrations are unlikely to be at steady-state. These observations are consistent with those from the lumped-parameter model. Analysis of various fluxes from the three-dimensional groundwater model also reveals that ponds provide the largest source of recharge to the aquifer, and hence, is a potential source of dissolved arsenic to the subsurface. Accordingly, a "Pond Hypothesis" has been developed suggesting that arsenic mobilization in Bangladesh aquifer is deriving from reductive dissolution of various arsenic bearing oxides (the widely accepted mechanism for arsenic mobilization in Bangladesh) deposited at the pond bottoms. The process of reductive dissolution occurs in the presence of organic matter and under reducing environment, when residing microbes respire on oxygen from oxide-minerals (e.g. Fe and Mn oxides) to process the organic matter for growth, and subsequently causes release of arsenic associated with the oxide-minerals to the aqueous phase. / (cont.) Afterwards, at the end of flooding season, the dissolved arsenic along with mixture of various dissolved solutes from pond bottoms enters the aquifer and is driven towards the well screen both vertically due to overlying recharge and horizontally due to increased pumping. Extensive small-scale pump tests and one large-scale extended pumping experiment carried out at our study area in Munshiganj indicates that the aquifer is anisotropic in nature creating flow convergence at the depth of irrigation well screen. Results from a three-dimensional hydrological model suggests that groundwater irrigation has changed the flow dynamics in the area - not only by reducing the residence and travel times, but also carrying solutes to particular depth from different sources and locations. Model simulations carried out for three different scenarios - 'Current Stage' (if the current flow condition continues), 'Ancient Stage' (before the advent of habitation and irrigation practices), and 'Inception Stage' (the beginning of irrigation and creation of ponds) - indicates that in general, the rice field water dominates at the shallowest depth while pond water dominates at the depth of irrigation well, and the contribution from river water increases with depth. Analysis of the average groundwater age distribution indicates that younger age dominates at shallower depths. More importantly, the age values at the monitoring locations can be explained by the relative contribution of recharge water from different sources. Furthermore, modeling results indicate that the groundwater age at 30m depth in Bejgoan Field Site is about 24-60 years old, which is consistent with the tritium age measurement at the same depth. The stable water isotope values in our study area shows a similar profile to the dissolved arsenic concentration, and their peak concentrations coincidence with the depth of irrigation well. / (cont.) Furthermore, comparison of calculated and measured isotopic values at the Bejgoan Field Site indicates that the calculated values are within the range of measured values, and thereby, confers that the observed isotopic profile results from the mixing of water from various recharge sources. More importantly, the lighter water at the depth of peak arsenic concentration can only be derived from lighter pond water recharge in November, whereas recharge from river and rainfall mainly occurs after March when those waters are actually heavier. Finally, observation of two distinct peaks in the dissolved arsenic concentration profile from a recently installed cluster beside a highly recharging pond provides a direct evidence supporting the "Pond Hypothesis". While the peak concentration at 30-40m depth corresponds to the characteristic regional hump observed in our study area, the second peak at a shallower depth (20m) has been explained as the local arsenic plume originating from the nearby pond bottom. / Ph.D.

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2009. / Includes bibliographical references (p. 58-59). / In this thesis, the importance of cladding panels on mid-rise buildings in an earthquake-prone region is investigated. A cladding panel acts as a protective or an insulating layer to control weather infiltration. The Northridge Earthquake, which took place on January 17, 1994, caused numerous heavy cladding panels to fall off the walls of residential and commercial buildings. The failure of these panels was a result of an insufficient understanding of the cladding behaviors as a subsystem in the three-dimensional framing system. Cladding is designed to be isolated from the structural frame movement during an earthquake. However, numerous studies have concluded that cladding interacts with the structural frame in providing lateral resistance. The advantages and disadvantages of different cladding materials, cladding systems, and cladding connections are presented in this thesis. The effects of cladding on mid-rise buildings in the Northridge Earthquake in the Los Angeles area are simulated in this study. Motion resistance contributed from cladding in a particular mid-rise building, a 19-story office building in downtown Los Angeles, is investigated. Analyses of clad models and unclad models are carried out, and clad models are discovered to displace less than unclad models. Therefore, cladding is able to contribute lateral motion resistance to a building during an earthquake, and structural engineers should include cladding in their analysis models when designing a building. / by Chuan-Hua Kuo. / M.Eng.