Página 20 dos resultados de 2122 itens digitais encontrados em 0.042 segundos

‣ The role of private participation in enhancing the Indian transport sector

Sharma, Nand, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 148 p.; 6684060 bytes; 6700521 bytes; application/pdf; application/pdf
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The Indian transport sector, one of the largest transport networks in the world, faces some serious issues. These may be identified as follows: * Unmet demand for service and infrastructure * Conflicting responsibilities * Inadequate resource mobilization * Poor Asset Management * Inadequate imposition of accountability Increasing the level of private participation in transport sector is one of the possible solutions to solve these problems. At present, private participation in the transport sector in India is low and generally restricted to small projects. Although various steps have been taken to attract the private sector participation in transport sector in India, various indirect and direct constraints exist in its implementation. Indirect constraints include low economic growth, higher poverty rate and high population growth rate. The direct constraints include planning and the institutional issues, methodological or procedural issues, financial constraints, social and the political constraints. In order to alleviate these constraints various steps can be taken. At the planning and the institutional level, India needs to develop a strategic planning network. At the legal and the regulatory level, there is a need for well-drafted laws and regulations related to private sector participation. Also...

‣ Stochastic analysis of dense nonaqueous phase liquid dissolution in naturally heterogeneous subsurface systems; Stochastic analysis of DNAPL dissolution in naturally heterogeneous subsurface systems

Fu, Xin, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 228 p.; 8870536 bytes; 8870345 bytes; application/pdf; application/pdf
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Field-scale Dense Nonaqueous Phase Liquid (DNAPL) dissolution in three-dimensional heterogeneous subsurface systems is investigated using a stochastic approach that treats the variability of flow properties as three-dimensional random fields. A steady-state, quasi-static DNAPL saturation distribution in a source zone is derived, based on the previous research to describe the field-scale nonuniform residual DNAPL distribution. A local-scale dissolution model is generalized from the laboratory experimental results. Effective transport and dissolution properties are obtained by a stochastic analysis, which includes nonstationarity in the concentration field to address both boundary and downstream effects. An extrapolation of the effective properties is performed for the large spatial variability of hydraulic and dissolution parameters. The extrapolation is evaluated using a unique two-zone model that simplifies the continuous DNAPL distribution to two components: low permeability lens zone with high DNAPL saturation and a surrounding permeable zone with low DNAPL saturation. The agreement between the two-zone model results with stochastic solutions demonstrates the adequacy of the extrapolation of the latter. Four field sites with different geological settings and hydraulic characteristics are evaluated using effective properties: the Borden site...

‣ Bathymetric evolution of sand bed forms under partially standing waves

Landry, Blake Jude
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (641 p.); 21593482 bytes; 37335576 bytes; application/pdf; application/pdf
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Experiments were conducted in a large wave flume where the interaction between water waves and a movable sand bed were investigated. Monochromatic and poly- chromatic waves of specified amplitudes and period were generated under cases of weak (R=0.2) and/or strong (R=0.9) reflections. Experiments included one of two mean grain sand sizes (0.2mm and O.mm) to examine the effects of different sediment transport modes (bed load and suspended load), on the over all evolution of the sand bed. Throughout the experiments, conductivity probes measured the surface wave envelope, charged-coupled device (CCD) cameras recorded small scale (ripple) formations and migrations, while a digital camera was employed to capture large scale variations (bars) and ripples over the entire sand bed. A final experiment was conducted using a mixture of the two uniform grain size to observe sediment sorting within the sand bed. Numerous sieve analysis and measurements of the active sorting sand depth were performed on sediment samples from various positions along the flume to quantitatively study the phenomena of sediment sorting.; by Blake Jude Landry.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.; Includes bibliographical references (v. 2...

‣ A federated time distribution system for online laboratories

Northridge, Jedidiah, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 82 leaves; 2914574 bytes; 2914382 bytes; application/pdf; application/pdf
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The iLab project began in June of 2000 with the initial goal of creating Internet accessible laboratory experiments. After the successful implementation of several distinct laboratories, the goals of the project shifted to address the design and construction of a generalized infrastructure capable of supporting a wide variety of laboratory experiments. Early experiences suggested the need for a configurable experiment scheduling system. Such a system would be particularly important in the face of expected growth: as the number of providers and consumers grew, it would become crucial to empower providers with the ability to enforce experiment usage policies, to guarantee timely lab access to clients, and to maximize resource usage whenever possible. We will explore how the present iLab infrastructure can be modified to allow for experiment scheduling. This system would be designed in keeping with two key principles: generality and architectural consistency. It would have to support disparate scheduling algorithms of varying complexity and remain faithful to the theme and priorities of the existing iLab infrastructure. Design will be based on requirements gathering and the analysis of existing remotely available experiments. Resulting changes to the iLab infrastructure will be enumerated...

‣ Reliability-based optimization of rail inspection

Kashima, Takashi, 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 126 p.; 3393398 bytes; 3393204 bytes; application/pdf; application/pdf
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This thesis proposes a quantitative method to optimize inspection/repair intervention in rail defect management. Rail defect management is important for track maintenance, since rails are the most significant and basic component of the track systems. Rail inspection is a fundamental intervention to prevent rail failure. Railroads have evolved the rail inspection interval based on their empirical judgement and on field data. A crack size is predicted by linear elastic fracture mechanics (LEFM). The proposed method identifies the time-varying rail reliability due to deterioration, using data obtained from LEFM and from first-order reliability methods (FORM), which consider the uncertainty regarding the model. Since FORM is an approximation method, Monte Carlo simulation confirms the results. To represent practical situations regarding rail defect management, an event tree (ET) analysis is performed. The ET is modeled to all events and actions with respect to inspection/repair intervention. The ET analysis evaluates the expected reliability of a rail after inspections and possible remedial actions. Based on these results, a life-cycle cost (LCC) model is formulated, taking into consideration the time value of money. To this end, applications of the model to optimization of inspection intervals and to investigation of the effect of nondestructive testing and remedial actions on the LCC and the interval are analyzed.; (cont.) As a result...

‣ Dynamic analysis of concrete coupled wall structures : a parametric study

Huang, Elaine Annabelle, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 103, [1] p.; 5285882 bytes; 5297953 bytes; application/pdf; application/pdf
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Concrete coupled wall structure is a system that can efficiently dissipate energy under the effect of lateral loads. It has been widely used in medium height buildings for several decades. While researchers have conducted both experimental and analytical investigations in order to improve the performance of concrete shear wall, there is a lack of systematic comparison of coupled wall behavior due to variation of parameters. Therefore, this report will carry out a parametric study by varying the height of the building, the degree of coupling (DC), and the shape of the wall piers. A computer-simulated study was carried out on the performance of coupled wall structures. The research process was divided into two phases with the first focusing on only on the shear wall system and the second on the interaction between the building and the core shear wall structure. Static pushover analysis was applied in Phase I, and acceleration response spectrum was employed in Phase II. The comparison of the results from both phases provided valuable insight on the structural behaviors of shear walls. The Phase I results showed that C-shaped coupled wall were more efficient than rectangular wall piers. From further investigation in Phase II, it was found that C-shaped wall with 15 degree opening could achieve the greatest stiffness. Same-size coupling beams could create DC in shorter buildings in Phase I...

‣ A performance study of ceramic candle filters in Kenya including tests for coliphage removal

Franz, Amber, 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 99 leaves; 7821320 bytes; 7832823 bytes; application/pdf; application/pdf
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Approximately 80% of all diseases in the developing world are caused by contaminated water (GDRC, 1999). In response to this crisis, decentralized point-of-use systems, such as ceramic candle filters, have emerged as viable options for improving water quality at the household level. This thesis evaluates the performance of five brands of ceramic candle filters that are locally available in the developing nation of Kenya: the AquaMaster (Piedra candle), Doulton Super Sterasyl, Stefani Sao Joao, Pelikan, and Pozzani candles. Filters were evaluated based on turbidity removal, flow rate, total coliform and E. coli removal, and cost. The Pelikan filters were also subjected to tests for viral removal using MS2-coliphages. Results from studies indicated that the Pelikan filters were the most effective at removing turbidity from Charles River water (97% reduction). Turbidity removal by other filters ranged from 88%-94%. Results from studies utilizing more turbid Nairobi water showed filters to reduce turbidity by 97%-99%. Results from flow rate studies performed at MIT revealed the Doulton Super Sterasyl to possess a significantly greater flow rate (0.55 L/hr) than the other brands. The flow rates of the other filters ranged from 0.14-0.26 L/hr. Filter tests utilizing the more turbid Nairobi water showed flow rates of 0.09-0.24 L/hr. Results from coliform removal studies performed at MIT showed the AquaMaster (Piedra candle)...

‣ A mouse model for studying gastrointestinal microbial ecology

Sarma-Rupavtarm, Ramahi Bhushan, 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 182 p.; 6650285 bytes; 6673397 bytes; application/pdf; application/pdf
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The mammalian gastrointestinal (GI) tract harbors a complex microbial ecosystem with hundreds of bacterial species at total levels as high as 10¹¹⁻¹² cells/g tissue. These bacteria play an important role in the health of the host as well as in causing disease, but studies on the roles of the GI microflora are hindered by the lack of a suitable model system. This thesis characterizes and uses a defined flora mouse model to study interactions between exogenous bacteria and the GI microflora. The first part of the thesis characterizes a defined flora mouse model consisting of immunodeficient C.B-17 SCID mice colonized with the eight bacterial strains of the altered Schaedler flora (ASF). Specific and sensitive molecular methods were developed to accurately estimate the levels of different ASF strains. Distribution of specific ASF strains along the GI tract was dependent on the oxygen tolerance of the strains. Fecal levels of different strains, which are typically used as a model for colonic bacteria, were different from colonic levels, although all colonic strains were present in feces. ASF strains were persistent in the mouse GI tract even in the face of long-term exposure to other bacteria. The second part of the thesis evaluates the presence of different ASF strains in inbred and outbred mouse models from different vendors to establish the potential for widespread use of these strains as representatives of the mouse GI microflora. Seven of the eight strains were persistent in both inbred and outbred mice from all vendors studied. This indicates the potential for the ASF strains to be used as a model system even in mouse models that do not harbor a defined flora.; (cont.) The third part of the thesis explores ecological interactions following infection by an intestinal pathogen...

‣ Electrochemistry of soluble methane monooxygenase on a modified gold electrode : implications for chemical sensing in natural waters; Electrochemistry of soluble MMO on a modified gold electrode

Chuang, Janet Duanping
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 90 p.; 4754623 bytes; 4764724 bytes; application/pdf; application/pdf
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This work explored the possibility of using the soluble methane monooxygenase (MMO) enzyme, a three-component enzyme which catalyzes the oxygenation of methane and other substrates, to design a methane sensor for use in natural waters. Such a sensor would be useful for monitoring lake biogeochemistry, including the potential for lakes to be a source of methane into the atmosphere. An op amp-based potentiostat was constructed, and a LabVIEW program was written to control the instrument and acquire data digitally. Cyclic voltammetry experiments were conducted with both acetonitrile, a liquid substrate, and the natural substrate methane. With the hydroxylase component of the enzyme (MMOH) adsorbed onto a peptide-modified gold electrode, the amount of charge transferred during a scan depended on both substrate and oxygen concentrations. This concentration dependence did not occur when MMOH was not present. In the case of methane, the kinetic limitations of partitioning between gas and liquid phases may have contributed to experimental scatter. These results raise the possibility that MMOH may be used without the other two components to generate a reproducible, concentration-dependent signal. Signal strength was also dependent on the order in which high- and low-concentration trials were conducted. The hydroxylase may be able to store methane and oxygen in a hydrophobic cavity for later use...

‣ Crack coalescence in rock-like material under cycling loading

Ko, Tae Young, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 184 p.; 31606880 bytes; 31630176 bytes; application/pdf; application/pdf
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A total of 170 tests (68 tests for monotonic loading, 102 tests for cyclic loading) have been performed to investigate crack initiation, propagation and coalescence. The specimens have two pre-existing flaws which are arranged at different distances and angles. Wing cracks and secondary cracks are observed in both monotonic and cyclic tests. Wing cracks, which are tension cracks, initiate at (or near) the tips of the flaws and propagate parallel to the compressive loading axis. Secondary cracks always appear after wing crack initiation and lead to final failure. Secondary cracks initiate at the tips of the flaws and propagate in the coplanar direction of the flaw or horizontal (quasi-coplanar) direction. Six types of coalescence are observed. For coplanar geometry specimens, coalescence occurs due to the internal shear cracks. For non-coplanar geometry specimens, coalescence occurs through combinations of internal shear cracks, internal wing cracks and tension cracks. Contrary to monotonic tests, cyclic tests produce fatigue cracks. Fatigue cracks usually occur when 1) after coalescence, the specimens behave as if they had only one larger crack 2) specimens have been subjected to a particular number of cycles. In these experiments...

‣ Review of CPT based design methods for estimating axial capacity of driven piles in siliceous sand; Review of Cone Penetration Test based design methods for estimating axial capacity of driven piles in siliceous sand

Monzón A., Juan Carlos (Monzón Alvarado)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 100 leaves; 5159064 bytes; 5163204 bytes; application/pdf; application/pdf
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The Cone Penetration Test has been used for more than 30 years for soil exploration purposes. Its similarities in mode of installation with driven piles provides the potential of linking key variables of pile design and performance, such as base resistance and shaft friction, to measured cone tip resistance. Large scale pile load tests, performed in the last two decades, have shown better agreement with recent CPT based design criteria, than with conventional American Petroleum Institute (API) earth pressure approach design guidelines. The CPT based design methods provide a more coherent framework for incorporating soil dilation, pile size effect, pile plugging during installation, and the friction at the pile-soil interface. A review, of four recent CPT based design methods and the API design guidelines, for estimating axial capacity of driven piles in siliceous sands was performed by comparing their predictive performance to six documented on-shore piles with load tests. First, a detailed site investigation based on CPT data was performed to validate the provided soil profile, and to evaluate the accuracy of the CPT readings to identify and classify soil strata.; (cont.) Three piles were selected for further study and axial capacity calculations. Three of the design methods...

‣ Sustainable water resources development in Kuwait : an integrated approach with comparative analysis of the case of Singapore

Nazerali, Nasruddin A
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 60 leaves
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This thesis assesses the water resource status of Kuwait and Singapore, both countries considered as water scarce. The institutional aspect of Integrated Water Resource Management (IWRM) efforts in both countries is closely examined at international, regional, national and administrative levels. Aspects of the institutional framework which have contributed to the successful water management scenario in Singapore are identified in order to draw lessons for the case of Kuwait. Although complete emulation of the national and administrative bodies of Singapore may not be justified, specific activities, methodologies and structures are recommended for the institutional capacity building of Kuwaiti water management. Artificial surface aquifers are proposed as a suitable solution for enhancement of water storage capacity in Kuwait, one of the main aspects of sustainable water resources development for the country. The drainage depressions of Rawdhatain and Umm Al-Ahish, locations of water and oil resource development and the surrounding area are assessed for suitable sites. Impacts on the land use, land cover and natural drainage pattern are assessed. A specific design is recommended for the artificial surface aquifers and the storage capacity is computed.; (cont.) Storage of up to 70% of the 2010 projected water budget is found to be possible. However...

‣ The physical role of transverse deep zones in improving constructed treatment wetland performance

Lightbody, Anne F. (Anne Fraser), 1977-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 289 p.
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Velocity heterogeneity is often present in wetland systems and results in some influent water remaining in the wetland for less than the expected residence time. This phenomenon, known as short-circuiting, alters the distribution of the chemical and biological transformations that occur within the wetland and decreases performance in constructed treatment wetlands. In this thesis, field observations, experiments in a laboratory physical model, and mathematical modeling are used to explore the ability of transverse deep zones to mitigate the negative effect of short-circuiting on constructed wetland performance. Field observations were used to quantify short-circuiting in a 360-acre constructed treatment wetland in Augusta, Georgia. In each of the three marsh sections examined, between three and six narrow flowpaths were found that together carried 20-70% of the flow at a velocity at least ten times faster than the rest of the marsh. One known method for offsetting the deleterious effect of short-circuiting flowpaths is to include several transverse deep zones within each wetland cell. To study the physical mechanisms behind this proposed strategy, laser-induced fluorescence (LIF) was used within a laboratory scale model of a short-circuiting wetland with a transverse deep zone. Water exiting a fast flowpath formed a jet that initially entrained co-flowing fluid and spread laterally but then...

‣ Decision making under epistemic uncertainty : an application to seismic design

Agarwal, Anna
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 92 leaves
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The problem of accounting for epistemic uncertainty in risk management decisions is conceptually straightforward, but is riddled with practical difficulties. Simple approximations are often used whereby future variations in epistemic uncertainty are ignored or worst-case scenarios are postulated. These strategies tend to produce sub-optimal decisions. We develop a framework based on Bayesian decision theory that accounts for the random temporal evolution of the epistemic uncertainty and minimum safety standards, and illustrate the effects of these factors for the case of optimal seismic design of buildings. Results show that when temporal fluctuations in the epistemic uncertainty and regulatory safety constraints are included, the optimal level of seismic protection exceeds the normative level at the time of construction. We do a sensitivity analysis concerning the repair and retrofit strategies that control the repair actions following earthquake damages and the amount of structural upgrading in the case of non-compliance with the safety standards. We see, that just like the optimal initial design system, upgrades should also be made conservatively to provide a margin of safety against future adverse changes in the epistemic uncertainty and regulations. The optimal degree of conservatism depends in a complex way on the cost of providing additional seismic protection...

‣ Nonlinear resonance of trapped waves on a plane beach

Li, Guangda, Ph. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 310 p.
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Linear edge waves were first found mathematically by Stokes (1846). It has long been a topic of interest, since edge waves are believed to be responsible for the formation of beach cusps. Galvin (1965) was the first to observe in the laboratory that edge wave mode of frequency w can be excited by incident waves of frequency w. Guza and Bowen (1976) gave a theoretical explanation of the nonlinear mechanism of sub-harmonic resonance. This type of theory has been extended by Minzoni & Whitham (1977), Rockliff (1978), and Rockliff & Smith (1985), among others. Rockliff also initiated a. theory whereby subharmonic resonance can be achieved by an incident wave of frequency w, which leads to second harmonic at the second order to excite the edge wave. Their theory was however incomplete. The goal of this thesis is to extend the existing theories in order to show other paths to resonance. The nearshore region is a plane beach of small slope. For all cases we shall derive the evolution equations governing the edge wave amplitudes and analyze the stability of the equilibrium (static or dynamic) state. We first study in Chapter 2 synchronous resonance as a special case. We shall show that interaction between the edge wave and the incident/reflected wave also generates circulation cells on the beach.; (cont.) Comparison is made between our theoretical results and the experiments by Bowen & Inman. We then give a corrected version of the work of Rockliff and Rockliff & Smith. Next...

‣ Development of a landslide hazard map for the island of Puerto Rico

Kamal, Sameer A. (Sameer Ahmed)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 58 leaves
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This thesis describes the development of a landslide hazard map for the island of Puerto Rico through the use of Graphical Information System (GIS) tools. Parameters considered in this study are elevation, slope aspect, slope angle and land use. This study employed data for a total of 2,966 landslides. The elevation and land use analysis was conducted on the entire landslide dataset, while the slope aspect and slope angle analysis was conducted on a smaller subset (366 landslides). This work builds on previous landslide studies in Puerto Rico by employing a 5-m Digital Elevation Model (DEM) for the slope angle and slope aspect analysis. The major steps involved in the landslide hazard map generation are: a categorization analysis to determine relative hazards for each parameter, assignment of weights to each parameter based on their range of relative hazard values, and a consolidation of results from each parameter that is analogous to a multi-factorial analysis. Results indicate that slope angle is the dominant factor (87.5%) in determining landslide hazard, followed by elevation, slope aspect and land use. The slope angle results were found to be very sensitive on the choice of sampling methodology and data resolution. . In particular...

‣ Hybrid forecasting for airline revenue management in semi-restricted fare structures

Reyes, Michael H. (Michael Hamilton)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 134 p.; 6078346 bytes; 6080764 bytes; application/pdf; application/pdf
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In recent years, the airline industry has seen diminished performance of traditional Revenue Management (RM) systems largely due to the growth of Low Cost Carriers and the increased use of their "simplified" fare structures. With the removal of many of the fare restrictions essential to RM systems, standard demand forecasters can no longer segment demand and passengers are able to book air travel in fare classes lower than their actual willingness to pay. These "semi-restricted" fare structures typically contain several homogenous fare classes undifferentiated except by price, as well as several distinct fare classes with unique combinations of booking restrictions and advance purchase requirements. This thesis describes" Hybrid Forecasting" (HF) -- a new technique which separately forecasts "product-oriented" demand using traditional forecasting methods, and "price-oriented" demand for passengers who purchase only in the lowest priced fare class available when booking. The goal of this thesis is two-fold: to first measure the potential benefit of Hybrid Forecasting in terms of network revenue in semi-restricted fare structures, and then to measure potential improvements to Hybrid Forecasting.; (cont.) "Path Categorization" attempts to improve revenues by exploiting the expected higher level of passenger willingness-to-pay for non-stop service versus connecting service. And "Fare Adjustment" accounts for passenger sell-up behavior from lower to higher fare classes...

‣ Multi-criteria analysis : an alternative approach for the evaluation of road pricing strategies; Alternative approach for the evaluation of road pricing strategies

Ensor, Jeffrey D. (Jeffrey Douglas)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 205 p.; 13746776 bytes; 13773312 bytes; application/pdf; application/pdf
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Interest in road pricing among political leaders, transportation analysts, academics, and government agencies has increased in recent years. There are myriad reasons for this newfound consideration, but the deployment of intelligent transportation systems, the desire for additional revenue sources, and the search for policies that can reduce congestion are among the most important. This thesis examines the impacts of six different types of road pricing strategies, namely: conventional tolling, facility congestion pricing, express lanes (e.g. HOT lanes), area- wide and cordon pricing, network pricing, and distance-based pricing. It also presents a new sketch-planning model, the Road Pricing Decision Analysis Tool (RPDAT), which highlights each strategy's unique set of strengths and weaknesses for achieving different policy objectives and recommends road pricing strategies for particular metropolitan areas. Despite a growing interest in pricing, many decision makers feel unable to estimate the impacts of pricing strategies accurately with conventional models. This thesis discusses the factors believed to be responsible for drivers' choosing to use priced facilities, explains why conventional models are incapable of capturing many of these factors or the aggregate effects of a pricing policy...

‣ Regional parking fee : a potential funding source for transit?

Misiak, Jodie Mercer
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 156 leaves; 13542533 bytes; 13551261 bytes; application/pdf; application/pdf
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From a regional mobility perspective, Chicagoland is in serious trouble. The current Chicago Transit Authority (CTA) funding shortfall is just the most recent evidence of major flaws in the region's transit governance and finance structures. Over the past two decades, there have been numerous reasons and opportunities to modify the regional approach to public transportation provision. Yet the Regional Transportation Authority (RTA), the area's transit oversight entity, never initiated a critical re-evaluation of its role. Ideally, the central goal of the RTA would be to enable ample transport options throughout the region. However, rather than fostering enhanced service and increased ridership levels, the RTA funding process has resulted in performance declines and has encouraged a divisive political environment. This is ultimately damaging to both the economic health and the global competitiveness of the region. Now, as Chicagoland faces a particularly severe budget crisis, it is time to finally begin the discussion that should have commenced two decades ago. The region must alter its approach to transit finance and an additional operations funding source must be identified immediately. The implementation of a region-wide, non-residential parking fee could help achieve both of these goals. When compared with the option of a sales tax increase...

‣ The effect of the packing density on the indentation hardness of cohesive-frictional porous materials

Cariou, Sophie, S.M. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 192 p.; 30577924 bytes; 30577274 bytes; application/pdf; application/pdf
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Natural composites in general and sedimentary rocks in particular are highly heterogeneous materials which defy a straightforward implementation of the materials science paradigm of microstructure-properties-performance correlation. The application of nanoindentation to natural composites has provided the geomechanics community with a new versatile tool to test in situ phase properties and structures of geomaterials that cannot be recapitulated ex situ in bulk form. But it requires a rigorous indentation analysis to translate indentation data into meaningful mechanical properties. The development and implementation of such an indentation analysis for the strength properties of cohesive-frictional porous materials is the focus of this thesis. We report the development and implementation of a multi-scale indentation analysis based on limit analysis, which makes it possible to infer from an experimental hardness value and the solid's packing density the strength properties of the cohesive-frictional porous material.; (cont.) Making use of most recent advances in non-linear strength homogenization theory, we implement a homogenized cohesive Cam-Clay type elliptical strength criterion which takes into account the strength properties of the constituents (cohesion and friction)...