Página 6 dos resultados de 2122 itens digitais encontrados em 0.060 segundos

‣ Paying for transit operations : challenges and solutions for the Chicago Transit Authority

Kirschbaum, Julie B
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 147 p.; 7218941 bytes; 7338934 bytes; application/pdf; application/pdf
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This research identifies the challenges Chicagoland must confront to maintain a quality transit system. It analyzes the organizational and funding structure of the Regional Transportation Authority and its three service providers, including the Chicago Transit Authority. This investigation revealed that the greatest regional challenges are declining ridership (especially on bus) and increasing congestion from limited subsidies and a cost recovery statute. To address these challenges a series of alternatives were evaluated using a framework that considers revenue potential, incidence, side effects, and political feasibility. Based on this analysis, a four part strategy is recommended: 1. Change the current distribution formula. Unless a new allocation formula is established, CTA may not benefit from increased resources. The new formula should reduce reliance on discretionary funds by stabilizing current funding levels to the three service providers. 2. Increase RTA revenues. Currently the two wealthiest counties in the region (DuPage and Lake) pay significantly less than Cook County while enjoying comparable service. The RTA should increase their sales tax contributions to improve regional equity and increase resources. These resources should be used to address growing paratransit needs.; (cont.) 3. Develop a set of performance measures that respond to distinct transit markets. Rather than focusing exclusively on the cost recovery ratio...

‣ A study of air flow through saturated porous media and its applications to in-situ air sparging

Marulanda, Catalina, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (403 leaves); 53564692 bytes; 53564447 bytes; application/pdf; application/pdf
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The efficiency of an in situ air sparging system is controlled by the extent of contact between injected air and contaminated soil and pore fluid. Characterizing the mechanisms governing air propagation through saturated porous media is therefore critical to the design of an effective cleanup treatment. The objectives of this investigation were thus to identify and to quantify the parameters that affect the advancement of an air front through saturated soils. To this end, an experimental program was conducted in order to assess the impact of: 1) operational parameters, specifically the differences in air propagation as a result of injection under constant pressures and constant flow rate conditions, as well as the impact of injector geometry; and 2) medium properties, namely hydraulic conductivity and pore fluid characteristics. Experiments were conducted in a geotechnical centrifuge, which made it possible to test under a wide range of injection pressures while maintaining both realistic fluid and soil pressures, and sample stability. Experimental results show that air propagation characteristics through saturated soils are primarily controlled by two factors, the pressure in the air phase and the hydraulic conductivity of the medium. Under constant pressure injection...

‣ Ultrasonic nondestructive evaluation and imaging of defects in reinforced cementitious materials

Wang, Ji-yong, 1967-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 156 leaves; 7775811 bytes; 7775571 bytes; application/pdf; application/pdf
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Characterization of defect is one of the important objectives of nondestructive evaluation (NDE) for condition assessment of structures. Among many other NDE techniques, ultrasonic methods play a prominent role in the both quantitative and qualitative assessment of discontinuities in reinforced cementitious materials. Due to the heterogeneous nature of concrete, ultrasonic waves are highly scattered and attenuated, leading to the difficulty of concrete inspection using conventional ultrasonic techniques, including those that work well on relatively homogeneous materials such as metals. This thesis presents an advanced method for sizing and imaging of defects in reinforced cementitious materials. A two-dimensional, three-phase composite model of concrete is proposed to study the propagation and interaction behaviors of ultrasonic waves in concrete structures, and to gain a knowledge about wave diffraction with multiple cylindrical obstacles. The response of the modeled concrete structure to an incident ultrasonic pulse input signal (pulsed ultrasonic P-wave) is analytically investigated and simulated. A characteristic profile of the defect sizing as a function of focal depth is formulated via the synthetic focusing technique. A defect sizing parameter...

‣ Evaluating the costs and benefits of increased funding for public transportation in Chicago

Schofield, Mark L., 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 119 p.; 5721637 bytes; 5736486 bytes; application/pdf; application/pdf
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(cont.) off-peak ridership, is at or slightly below break-even with respect to net benefits if the CTA cost structure and tax source of subsidy remains unchanged. In order to justify any significant additional long-term funding for the purpose of growing ridership, the CTA should make operational changes to lower its costs and should seek additional funding from sources with lower societal costs.; The Chicago Transit Authority (CTA) faces an immediate financial crisis and a long-term struggle to maintain its role as a meaningful transportation provider in Chicago. Political and financial constraints will induce significant ridership losses in the near term unless additional operating funds are made available. Moreover, even if funding for current fares and service levels is maintained, the CTA risks a continuing decline in market share unless additional action is taken. This thesis investigates the costs and benefits of increased funding for the Chicago Transit Authority under various scenarios. First, it examines historical and political factors that have created the current tenuous environment for public transportation in Chicago. Then, it establishes a framework for assessing the potential effects of increased funding. A distinction is emphasized between measures that are internal to the agency...

‣ Logistics service network design : models, algorithms, and applications

Shen, Su, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 186 leaves; 5552658 bytes; 5552467 bytes; application/pdf; application/pdf
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Service network design is critical to the profitability of express shipment carriers. In this thesis, we consider two challenging problems associated with designing networks for express shipment service. The first problem is to design an integrated network for premium and deferred services simultaneously. Related existing models adapted to this problem are intractable for realistic instances of this problem: computer memory requirements and solution times are excessive. We introduce a disaggregate information-enhanced column generation approach for this problem that reduces the number of variables to be considered in the integer program from hundreds of thousands to only thousands, allowing us to solve previously unsolvable problem instances. The second problem is to determine the express package service network design in its entirety, including aircraft routings, fleet assignments, and package flow routings, including hub assignments. Existing models applied to this problem have weak associated linear programming bounds and hence, fail to produce quality feasible solutions. For example, for a small network design problem instance it takes days to produce a feasible solution that is provably near- optimal using the best performing existing model. To overcome these tractability challenges...

‣ Operator-adapted finite element wavelets : theory and applications to a posteriori error estimation and adaptive computational modeling

Sudarshan, Raghunathan, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 171 leaves; 7377914 bytes; 7399145 bytes; application/pdf; application/pdf
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We propose a simple and unified approach for a posteriori error estimation and adaptive mesh refinement in finite element analysis using multiresolution signal processing principles. Given a sequence of nested discretizations of a domain we begin by constructing approximation spaces at each level of discretization spanned by conforming finite element interpolation functions. The solution to the virtual work equation can then be expressed as a telescopic sum consisting of the solution on the coarsest mesh along with a sequence of error terms denoted as two-level errors. These error terms are the projections of the solution onto complementary spaces that are scale-orthogonal with respect to the inner product induced by the weak-form of the governing differential operator. The problem of generating a compact, yet accurate representation of the solution then reduces to that of generating a compact, yet accurate representation of each of these error components. This problem is solved in three steps: (a) we first efficiently construct a set of scale-orthogonal wavelets that form a Riesz stable basis (in the energy-norm) for the complementary spaces; (b) we then efficiently estimate the contribution of each wavelet to the two-level error and finally (c) we select a subset of the wavelets at each level to preserve and solve exactly for the corresponding coefficients. Our approach has several advantages over a posteriori error estimation and adaptive refinement techniques in vogue in finite element analysis. First...

‣ Decomposition of hydrogen peroxide and organic compounds in the presence of iron and iron oxides

Kwan, Wai P. (Wai Pang), 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 182 p.; 6488698 bytes; 6488505 bytes; application/pdf; application/pdf
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Most advanced oxidation processes use the hydroxyl radical (OH) to treat pollutants found in wastewater and contaminated aquifers because OH reacts with numerous compounds at near diffusion-limited rates. OH can be made by reacting hydrogen peroxide (H202) with either Fe(II) (the Fenton reaction), Fe(1), or iron oxide. This dissertation investigated the factors that influence the decomposition rates of H202 and organic compounds, as well as the generation rate of -OH (VoH), in the presence of dissolved Fe(IH) and iron oxide. The Fe(III)-initiated chain reaction could be the dominant mechanism for the decomposition of H202 and organic compounds. The degradation rates of H14COOH, an OH probe, and H202 were measured in experiments at pH 4 containing either dissolved Fe(III) or ferrihydrite. Combined with the results from experiments using a radical chain terminator, we concluded that a solution chain reaction was important only in the Fe(III) system. In the ferrihydrite system the amount of dissolved Fe was insufficient to effectively propagate the chain reaction. In addition, a nonradical producing H202 loss pathway exists at the oxide surface. The oxidation rate of any dissolved organic compound can be predicted from VOH if the main sinks of -OH in the solution are known. Experiments using H14COOH and ferrihydrite...

‣ Theoretical and experimental study of nonlinear internal gravity wave beams; Nonlinear internal gravity wave beams

Tabaei Befrouei, Ali, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 124 leaves; 6434918 bytes; 6450478 bytes; application/pdf; application/pdf
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Continuously stratified fluids, like the atmosphere and the oceans, support internal gravity waves due to the effect of buoyancy. This type of wave motion is anisotropic since gravity provides a preferred direction. As a result, a localized source oscillating at a frequency below the buoyancy frequency in a uniformly stratified Boussinesq fluid, rather than cylindrical wavefronts, gives rise to elongated disturbances propagating along specific directions depending on the driving frequency. Such wave beams can be readily generated in the laboratory by oscillating a cylinder in a stratified fluid tank, and, according to recent numerical simulations and field observations, often arise in the atmosphere due to thunderstorms and may also be generated in the oceans by tidal flow over sea-floor topography. So far, internal wave beams have been studied mostly using the linearized equations of motion valid for small-amplitude disturbances. The present thesis examines theoretically and experimentally some aspects of non-linearity in the propagation, reflection and collision of internal gravity wave beams. An asymptotic theory is developed for the propagation of isolated two-dimensional or axisymmetric nonlinear beams, that also takes into account viscous as well as re- fraction effects due to the presence of a mean flow and non-uniform buoyancy frequency. In this instance...

‣ Earth pressure balance (EPB) shield tunneling in Bangkok : ground response and prediction of surface settlements using artificial neural networks

Suwansawat, Suchatvee, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 597 leaves; 28602431 bytes; 28648126 bytes; application/pdf; application/pdf
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Although Earth Pressure Balance (EPB) shields have been used for several decades, very little information exists about the actual mechanisms of shield-ground interaction. The ground response mechanism induced by EPB tunneling is difficult to understand, because this requires not only reliable ground deformation measurements in the field but also operational records of the shield. Numerous empirical and analytical relations between characteristics of traditional shields and surface and subsurface deformations exist; also 2-D and 3-D numerical analyses have been applied to such tunneling problems. However, very few approaches have been developed for EPB tunneling. This research makes use of the fact that in the Bangkok MRTA project, data on ground deformation and shield operation were collected. The tunnel sizes are practically identical and the subsurface conditions over long distances are comparable, which allow one to establish relationships between ground characteristics and EPB-operation on the one hand, and surface and subsurface deformations on the other hand. A computerized database, which records much of the information on a ring-by-ring (1.2 meter interval) basis, was developed for this purpose. After using the information to identify which ground- and EPB-characteristic have the greatest influence on ground movements...

‣ Collection and representation of GIS data to aid household water treatment and safe storage technology implementation in the northern region of Ghana; Collection and representation of Geographic Information System data to aid HWTS and safe storage technology implementation in the northern region of Ghana

VanCalcar, Jenny E. (Jenny Elizabeth)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 56 leaves; 18480731 bytes; 18480414 bytes; application/pdf; application/pdf
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In 2005, a start-up social business called Pure Home Water (PHW) was begun in Ghana to promote and sell household water treatment and safe storage (HWTS) technologies. The original aim of the company was to offer a variety of products, allowing customers to choose the technology which best fit their individual needs. This differed from the typical implementation of HWTS promoters to date, in which an organization often distributes a single technology for the population to use. Instead, Pure Home Water wanted to give users a choice. PHW is also unique because they are attempting to sell their products without any subsidy. The goal is to create a sustainable business that will both bring better quality water to the population and be financially self-supporting. Because the company is new, a need existed to gather data on the demographic, health, and water and sanitation infrastructure within the region. Due to the geographic nature of the project, it was decided that a Geographic Information System (GIS) would be the best tool to store, analyze and represent the data.; (cont.) The system could be used to help plan relevant business strategies, and maps could be created to visually communicate important information among the Pure Home Water team and other interested parties. The final database did achieve the goal of collecting and bringing together important regional information in a form hopefully useful to PHW...

‣ Analysis and design of household rainwater catchment systems for rural Rwanda

Cresti, Daria
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 113 leaves
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The Dian Fossey Gorilla Fund International (DFGFI) contacted MIT in September 2006 for technical assistance to analyze the water-supply potential within the Bisate Sector, Musanze District, Rwanda. The present study focuses on designing low-cost household rainwater catchment systems to improve the quantity and quality of water available and therefore achieve higher standards of living for the Bisate village. Given the climatic and geographic characteristics of Bisate, rainwater harvesting represents one of the most appropriate solutions to improve water supply. The designed low-cost household rainwater catchment system consists of an excavated cistern of 6 cubic meters volume, lined with a plastic tarpaulin sheet and covered with a wood and iron lid, and with a hand pump to extract water. The cistern should provide an average of 16 liters/day/person for the entire year for medium-size houses (roof area of 35 m2) and 21.5 liters/day/person for large-size houses (82 m2). The excavated cistern is designed with walls to stop surface runoff from entering into the cistern, and a hard cover and hand pump to extract water and minimize water contamination from faecal bacteria. The implementation of these small-scale rainwater harvesting systems should improve water quality and supply for the families of Bisate Village.; (cont.) Indeed...

‣ Effects of dynamic vegetation and topography on hydrological processes in semi-arid areas

Ivanov, Valeri Yuryevich, 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 453 p.
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Ecosystems of dry climates represent a particularly interesting object for ecohydrological studies, as water is generally considered to be the key limiting resource. This work focuses on vegetation-water-energy dynamics occurring in the complex terrain of a semi-arid area characteristic of central New Mexico. The study constructs a dynamic model of coupled interactions, [tRIBS+VEGGIE], that considers essential water and energy processes over the river basin and links them to the basic plant life regulatory processes. After model calibration, a set of numerical experiments is carried out for two small-scale synthetic domains that exhibit characteristic hillslope curvatures. A weather generator is used to create the long-term series of meteorological forcing. The linkages between terrain attributes and patterns of C4 grass productivity and water balance components are examined for three generic soil types: sand, loam, and clay. It is argued that in conditions of negligible moisture exchange, site aspect and slope are the key determinants of both the hydrologic behavior and the degree of "favorability" to vegetation.; (cont.) As shown, certain topographic locations are more favorable to vegetation development, as compared to a flat horizontal surface not affected by lateral effects such as radiative shading or water transfer. These locations are associated with sites of northerly aspect with surface slopes within a narrow range of magnitudes. Contributions from both the rainfall and radiation forcings are discussed to explain the existence of these niches. The sensitivity of results is investigated relative to modifications in the meteorological forcing and the dominant mechanism of lateral water transfer. The analysis unequivocally demonstrates the critical role of soil texture type in regulating the spatio-temporal aspects of coupling between vegetation-hydrology processes. Two additional controlling topographic features are suggested...

‣ Evaluation of the complementary use of the ceramic (Kosim) filter and Aquatabs in Northern Region, Ghana

Swanton, Andrew A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 163 p.
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The Kosim filter is a ceramic water filter that is currently used in Northern Ghana. Based on prior MIT research in Northern Ghana, this technology is effective at removing 92% of turbidity, 99.4% of total coliforms, and 99.7% of E. Coli from unimproved water sources. However, the product water is still microbially contaminated. The purpose of this thesis is to explore the effectiveness of combining two household water treatment technologies, the Kosim filter and Aquatabs, in order to achieve a more effective and complete water treatment system. Aquatabs are sodium dichlorisocyanurate chlorine tablets that are used on the household scale. They are particularly effective at killing pathogenic bacteria; however, they have predominantly been applied in emergency relief situations and have never, apart from one research study conducted by the Center for Disease Control, previously been applied in Ghana. In this study, 59 rural households (24 in a lower-class community and 35 in a lower middle-class community) in possession of Kosim filters were visited as part of a three week pilot study. During the initial visit, households were surveyed about the use and perception of their Kosim filters, they were trained in the use and given a one week supply of Aquatabs...

‣ Using land value capture to fund rail transit extensions in Mexico City and Santiago de Chile

Covarrubias, Alvaro, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 213 p.; 9898828 bytes; 9978996 bytes; application/pdf; application/pdf
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The effects of rail rapid transit on land uses and land values are discussed. Rail transit can enhance accessibility, and can raise the demand for locating in areas around stations, increasing land value, and in some cases fostering redevelopment at higher densities. The attraction that the areas around stations produce depends on the number of trips generated for unit of land for different types of land-uses. A series of studies on the effect of rail transit on land values are reviewed. Using data from censuses and origin-destinations surveys, the effects of metro lines on land-uses during the 1990's in Mexico City and Santiago de Chile are determined. Results show that in Mexico City neither zones located next to the new lines, nor zones located next to the lines built before 1990 had a higher growth of population, income per capita or employment, as compared to other zones with similar densities and incomes per capita. In the case of Santiago, whereas the areas located next to the newly built line had similar changes to other zones, the areas located next to the two lines built before the 1990's had a significantly higher growth in number of households and average income per capita than other areas, especially in high-income districts. These results are explained by the lower attractiveness of the metro for middle and high-income people in Mexico City as compared to Santiago de Chile...

‣ Performance and functional enhancement of artificial market psychology simulator

Akula, Mohan Kumar, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 65 leaves; 2195900 bytes; 2195709 bytes; application/pdf; application/pdf
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Artificial Market Psychology Simulator (AMPS) is an adaptive and programmable simulation system designed to assist researchers in the study of psychology of securities traders. It forms a part of the larger system that includes the MIT Web Market - a double-auction engine for securities trading and RStudio - a physiology data acquisition software. The AMPS system controls price patterns and induces market events in an adaptive fashion. This research improves the performance and functioning of AMPS by generating realistic market scenarios in response to the trading subject's physiological feedback during the simulation process. Despite the subject's knowledge of the simulated system, AMPS generates market scenarios such that the trading subject can attach credibility to these events and respond accordingly. The adaptive nature of AMPS can be attributed to its ability to adjust market response based on observed physiological characteristics of the research subject. Another improvement is the integration of AMPS with RStudio. The simulation system uses real-time market and physiology data provided by the MIT Web Market and RStudio respectively. A prototypical scenario that represents a research subject's typical emotional states in response to market volatility during the simulation process has also been modeled. One specific software challenge is the integration of RStudio - written in C++...

‣ Material invariant properties and reconstruction of microstructure of sandstones by nanoindentation and microporoelastic analysis

Bobko, Christopher Philip, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 189 p.; 8789538 bytes; 8813337 bytes; application/pdf; application/pdf
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The diversity of sandstones and sandstone properties that exist in nature pose a significant problem for engineers who deal with these materials, whether in oil well exploration and exploitation or art and architectural conservation. The solution proposed in this thesis takes a highly reductionist approach to the problem. Properties of the sandstone material are first reduced to material invariant properties of the material phases present in sandstone. These are universal constants which do not vary from one sample to the other. From these material invariants, it is then possible to 'nanoengineer' the properties of a specific sandstone sample based only on a few easily measured properties - the volume fractions of the material phases. To help identify material invariant phases and reconstruct microstructure, a multi-scale think model for sandstone is developed from ESEM images as well as from the results of mineralogy, grain size, and porosimetry experiments. A nanoindentation campaign is performed to characterize sandstones at multiple scales and an innovative technique is used to separate the various indentation responses that can occur on a heterogeneous composite. Material invariant phase properties are obtained for both the sand grains and the clay minerals. A new technique for estimating volume fractions of composite materials using nanoindentation is developed and verified. Clay stiffnesses are found to be highly dependent on microstructure rather than on mineralogy...

‣ Effect of stratification due to suspended sediment on velocity and concentration distribution in turbulent flows

Herrmann, Julie Marine, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 152 p.; 6031433 bytes; 6051737 bytes; application/pdf; application/pdf
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(cont.) An examination of the effects of uncertainty in the predictive capability of our model reveals that this overshadows the slight improvement resulting from accounting for stratification. Finally, our stratification model appears to be nearly equivalent to making von Karman's constant a variable as done in the earliest attempts to account for stratification in sediment-laden flows.; Sediment-induced stratification effects on velocity profiles and sediment concentration distribution in a steady, uniform turbulent flow are examined in this thesis. The early work concerning sediment stratification relates this to von Karman's constant's variability. Subsequent attempts to account for stratification were based on the stratified flow analogy, introducing the parameters α and β, whose values were assumed to be those obtained for thermally stratified flows. Following these investigators, we assume stratification effects to be expressed through these parameters. We solve the governing equations for velocity and sediment concentration for a parabolic, a simplified linear-constant and an extremely simplified linear neutral eddy viscosity model. Analytically closed form solutions are obtained. The parabolic and linear-constant models' formulae require numerical evaluation of integrals. The linear model provides excellent estimates of velocity and concentration and does not require numerical computation. We run our model against experimental data to obtain the optimal set [α...

‣ Waves, currents, and sediment transport in the surf zone along long, straight beaches

Tajima, Yoshimitsu, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 313 p.; 11508303 bytes; 11508103 bytes; application/pdf; application/pdf
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This study presents a theoretical model for predictions of near-shore hydrodynamic characteristics and the local sediment transport rate along long, straight beaches. The wave may be periodic or random, the beach may be plane or barred, and the bed may be concrete or covered with movable natural sand grains. The present model must be efficient and flexible so that it can accommodate iterative computations for time-varying and hence arbitrary beach profiles. The near-shore hydrodynamics model consists of wave, surface roller, and near- shore current models. Both wave and surface roller models are based on simple energy balance equations and, based on these models, the near-shore current is determined from two-layer 2DH momentum equations. Coupled with a simple turbulent eddy viscosity model, vertical profiles of mean shear current are analytically obtained. The model accounts for advective interactions between waves, surface rollers, and currents and, coupled with the surface roller model, explain the shoreward shift of the peak longshore current velocity. The model applies a modified version of Madsen's (1994) wave-current bottom boundary layer model to specify the bottom boundary condition from knowledge of equivalent bottom roughness scaled by a sediment diameter.; (cont.) Introducing the predicted near-shore hydrodynamic characteristics...

‣ Forecasting 65+ travel : an integration of cohort analysis and travel demand modeling

Bush, Sarah, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 104 leaves; 5012420 bytes; 5012228 bytes; application/pdf; application/pdf
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Over the next 30 years, the Boomers will double the 65+ population in the United States and comprise a new generation of older Americans. This study forecasts the aging Boomers' travel. Previous efforts to forecast 65+ travel are lacking in key two respects: they have failed to incorporate generation differences and have forecasted only broad travel characteristics (e.g. vehicle miles traveled). Drawing on the theory of generations, this study investigates empirically whether cohort differences in travel exist between the Boomers and the current 65+ population. It incorporates theoretically motivated cohort variables related to the historical processes of motorization, proxied by registered automobiles per person, and gender role evolution, proxied by labor force participation rates of women. The resulting forecast predicts the aging Boomers' travel demand with respect to activities requiring travel, person miles traveled, usage of transit and non-motorized modes, and trip chaining propensity. Data extracted from the 1977, 1983, 1990, and 1995 National Personal Transportation Surveys (NPTS) are used to estimate discrete and joint discrete/continuous demand models. Multiple imputation is used to impute missing survey data. Iterative proportional fitting is used to simulate future populations for forecasting purposes. Although 65+ travel is predicted to increase across all the modeled travel indicators...

‣ Safe water storage in Kenya's modified clay pot : standardization, tap design, and cost recovery

Young, Suzanne E
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 120 leaves; 7055199 bytes; 7060253 bytes; application/pdf; application/pdf
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One of the main components necessary for providing safe drinking water for users who lack piped water in the home is the ability to safely store it in the home. Users in the Nyanza Province of Kenya frequently carry water from some distance or purchase vended water and traditionally store this water in their homes in clay pots. CARE/Kenya, a non-governmental organization working in conjunction with local women potters and the Centers for Disease Control and Prevention, modified these clay pots so that they fit the definition of designated safe storage water containers, which contain the following three characteristics: a narrow mouth, a lid, and a tap to prevent recontamination. Three pottery production sites were visited in order to document, analyze, and suggest improvements for the design of the modified clay pots, specifically with regards to the standardization of the size and shape of the pots, so as to allow simple and convenient standardized household chlorine dosing, and the tap design and attachment, because the current tap design is expensive and prone to leaking.; (cont.) The modified clay pots displayed little variability in pot dimensions, and the 20 liter modified clay pots from the Amilo location showed a less than or equal to 10% volume variability that is acceptable according to the Centers for Disease Control and Prevention household chlorine dosing procedure. A reference rope tool developed to help standardize the size of modified clay pots can be used to train new potters but is not necessary for experienced potters. The spring-operated plastic tap was found to be the most promising design to replace the current metal tap design. The material cost of the modified clay pots at the three sites was determined with some certainty to range from 202-370 KSH (US$2.70-US$4.90). However...