Página 7 dos resultados de 2122 itens digitais encontrados em 0.027 segundos
Resultados filtrados por Publicador: Massachusetts Institute of Technology

‣ Assessing the impact of regulation and deregulation on the rail and trucking industries

Lowtan, Donavan M. (Donavan Mahees), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 210 p.; 11476173 bytes; 11503455 bytes; application/pdf; application/pdf
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(cont.) Many Class I railroads disappeared and severe competition bankrupted many small carriers in the trucking industry. Larger trucking carriers gained market dominance. Real wages in the trucking industry fell. The size of the railroad labour force decreased while railroad wages remained stagnant. Based on numerous pre-deregulation indicators provided by the government, industry, and academia, this essay shows that deregulation did not fulfill many of the promises made prior to the Staggers Act and the Motor Carrier Reform Act.; The Interstate Commerce Commission successfully implemented its 1887 mandate of reducing the monopolistic powers of the railroads. However, as freight transportation evolved into a competitive system with the emergence of trucking, the ICC effectively adapted its policies. ICC minimum rate regulations and track abandonment procedures kept many Class I railroads competitive. ICC ownership certificate requirements reduced destructive competition in the trucking industry. The blame assigned to the ICC for railroad problems was exaggerated. The Penn Central bankruptcy showed that the railroads had a variety of non-regulation related problems; including rigid management, poor attitudes towards passenger rail services...

‣ Architecture and optimization for a peer-to-peer content management system

Edge, Dion M. (Dion Miguel), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 88 leaves; 5378094 bytes; 5387910 bytes; application/pdf; application/pdf
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This thesis will explore the design and optimization of a peer-to-peer network application as a solution to complex content management problems. Currently, most content management systems are expensive, cumbersome and inflexible custom solutions that require knowledge workers to change their work habits. Peer-to-peer offers a uniquely decentralized and, potentially, scalable solution for knowledge workers by providing a simple and visual tool for file management, meta-data description and collaboration. This thesis will reference a client beta designed and developed by the author. Additionally, this thesis will address the need for content management solutions, the state of current solutions and a requirements document for a solution. Subsequently, the thesis will explore the design aspects of a peer-to-peer content management solution. As well as designing and developing a P2P client as proof of concept, this thesis will mathematically explore the implications of scaling the client to many users and methods to optimize performance. The last few chapters will cover the implementation of the client, proposed next steps for development and analysis of alternative architectures.; by Dion M. Edge.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ Improving transit service connectivity : the application of operations planning and operations control strategies

Younan, Bassel J., 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 133 p.; 5638060 bytes; 5655126 bytes; application/pdf; application/pdf
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(cont.) showed that the benefits accrued from coordinating schedules on Route 53 were not significant mainly due to the headway compatibility requirement which reduces the number of transfers amenable for improvement. Greater benefits were encountered when the schedules on the connecting routes were allowed to change as well. For Route 63, schedule coordination is not worth attempting due to the combination of the short six-minute headway on that route and the high variability in vehicle arrival times. On the control side, the practice currently adopted at CTA is to hold a "ready" vehicle at a transfer stop if the connecting vehicle has already arrived and this is likely to be an effective as well as easy-to-implement control policy.; Providing direct public transportation service for every origin-destination pair is very expensive if not infeasible for a transit agency, so it relies on the willingness of passengers to transfer. However, transfers usually reduce the attractiveness of transit because they add uncertainty, discomfort, waiting time and cost to most trips. This research focuses on examining different transfer coordination strategies that can reduce the disutility of transfers by minimizing the expected waiting times of transferring passengers. Two models are developed to assess scheduling and real-time holding decision rules for vehicles on a transit corridor. The operations planning model involves the simultaneous application of two planning strategies: changing the terminal departure time and inserting slack time. The operations control model has the capability to utilize any available current network information and to determine optimal dispatch times for vehicles at transfer stops. The two models were tested on a hypothetical corridor to illustrate their applicability in coordinating transfers. On the planning side...

‣ Mechanical and optical behavior of a novel optical fiber crack sensor and an interferometric strain sensor

Olson, Noah Gale, 1969-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 220 leaves; 9058832 bytes; 9058641 bytes; application/pdf; application/pdf
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The proper interpretation of measurements from an optical fiber sensor requires a full understanding of its mechanical response to external action and the corresponding change in optical output. To quantify the mechanical behavior it is necessary to know the mechanical properties of the fiber coatings. A new method for measuring the coating stiffness directly on the fiber uses nano-indentation. Special sample preparation and testing procedures were developed for the measurement of very low modulus materials using the Nano Indenter II. Results are obtained for two different acrylate coated optical fibers, namely Corning SMF28 and 3M FS-SN-4228. These results are used in understanding the behavior of the novel crack sensor and of an interferometric strain sensor. A distributed crack sensor that does not require prior knowledge of crack location and employs a small number of fibers to monitor a large number of cracks is developed. The basic design of the sensor is a polymer sheet containing an inclined fiber that is coupled to a structure. The sensor principle is that cracking in the structural member leads to cracking in the polymer sheet which induces fiber bending leading to signal loss. Monitoring the backscattered signal provides crack opening size and location. A theoretical model for optical fiber loss prediction is developed based on a combination of mechanical and optical analyses.; (cont.) Model prediction is found to be in relatively close agreement with experimental results. Model simulation can hence be carried out to provide guidelines for designing crack sensors for various applications. The behavior of both coated and uncoated fibers for strain measurement applications is also examined. A theoretical assessment using a three-dimensional finite element model for both coated and uncoated optical fibers is presented. Results show that the coating stiffness can significantly affect the strain transfer from the member under load to the optical fiber. The three-dimensional finite element model can provide guidelines for the optimized design of strain sensors. A straightforward analytical solution shows good equivalence with the theoretical solution under certain conditions. Experiments using an interferometer were conducted to verify the results of the theoretical study and show good correspondence.; by Noah Gale Olson.; Thesis (Ph. D .)--Massachusetts Institute of Technology...

‣ Low-impact development in the Assabet River Watershed : site hydrologic design and watershed-scal implications

Friedlich, Brian J. (Brian Joseph), 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 96 leaves; 5994683 bytes; 6005667 bytes; application/pdf; application/pdf
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Low-Impact Development (LID) is a relatively new approach to stormwater management. It aims to mimic natural hydrology through increased recharge and decreased runoff. LID technologies focus on distributed treatment of stormwater, as opposed to traditional centralized management. The potential benefits include improved water quality in runoff, decreased flooding in rivers and streams, and increased baseflow critical to surface water quality. This thesis investigates two important aspects of any new stormwater management technology: the site level design and large-scale implications. A case study for site-level design is performed in the town of Acton in central Massachusetts. An LID stormwater management design is completed on a three-acre site. The design implements LID technologies, such as rain garden storage areas, pervious pavement, and curb cuts. Pre-developed, existing, and LID-designed scenarios are analyzed. A computer program called the Site Low-Impact Development Design (SLIDD) Model is developed to account for the distributed nature and unique characteristics of the LID technologies. Analysis reveals that LID is capable of not only improving the existing site hydrology, but returning a developed site to natural hydrologic conditions. The design is able to control both peak runoff rates and runoff volume. The watershed-scale implications of LID are of great importance...

‣ Carbon and electron flow via methanogenesis, So₄²⁻, NO₃⁻ and Fe³⁺ reduction in the anoxic hypolimnia of upper Mystic Lake

Peterson, Eliza J. R. (Eliza Jane Reader), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 96 leaves; 3739765 bytes; 3750869 bytes; application/pdf; application/pdf
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The profiles of CH₄ and CO₂ obtained by the use of a novel sampler, along with the profiles for nitrate (NO₃⁻), sulfate (So₄³⁻)and iron (Fe²⁺) were used to estimate the rates of the various anaerobic decomposition reactions during spring and fall stratification in Upper Mystic Lake. The equivalent electron and carbon flow of the reactions were also calculated to obtain a mass balance within the hypolimnia of UML. From the calculations, the approximate organic carbon decomposition rate, measured as CO₂ accumulation, was 7.54 mmol m⁻² d⁻¹. The amount of decomposition from the reactions involving nitrate, sulfate, iron and methane formation together accounted for 80% of the total organic carbon decomposition. Therefore, 20% of the CO₂ accumulation in UML could not be accounted for. Possible explanations for the excess CO₂ production could be the formation of reduced iron minerals and/or the loss of methane due to ebullition and oxidation. Such explanations suggest future studies of UML to better resolve the electron budget. In order to study the redox balance in Upper Mystic Lake, a method was devised for precisely sampling dissolved gases in the water column. Like other stratified lakes, UML has a large amount of anaerobic metabolism of organic matter occurring in the sediments and a subsequent accumulation of methane (CH₄) and carbon dioxide (CO₂) in the hypolimnia. Previously...

‣ The design and field evaluation of a new dual pressure and temperature tapered probe

Chartier, Matthew G. (Matthew Garth)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 406 p.; 11125203 bytes; 11181549 bytes; application/pdf; application/pdf
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The T2P is a new penetration device that measures temperature at its tip and pore pressure at a point just above the tip and at a second location near the base of the probe shaft. The main purpose of the T2P, recently designed and fabricated at MIT, is to reduce the time required to accurately estimate in-situ pore pressures (u₀) of marine sediments. This goal will be accomplished by using the two-point matching method (Whittle et al., 1997; 2001) to compare measured partial T2P dissipation records with theoretical dissipation curves, derived using the Strain Path Method (Baligh, 1985) and total or effective stress soil models. A four-day field program was conducted at a test site in Newbury, Massachusetts to evaluate the design and performance of the T2P. The field program was designed with the intention of performing a number of dissipation tests at a series of elevations within a deep deposit of Boston Blue Clay. Twenty-four hour operation of the data acquisition system allowed overnight dissipation data to be collected. Two boreholes were used to collect a total of eight pore pressure dissipation records, whose length ranged from 0.74 to 19.74 hours. It is not clear if any of the eight monitoring periods were of sufficient duration for full dissipation to occur; it is suspected that measurement periods longer than 20 hours are required to allow complete dissipation around the probe...

‣ Express shipment pick-up and delivery : evaluating airline recovery options

Cheung, Jennifer C. (Jennifer Ching Wah)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 96 p.; 4130348 bytes; 4141485 bytes; application/pdf; application/pdf
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Irregular operations in the Express Shipment Service Delivery industry require real time solutions that can be implemented to determine routings for aircraft and time-sensitive commodities. During inclement weather, crew unavailability, and mechanical failures, operations personnel use various approaches to recover from disruptions, including rescheduling or canceling flight legs, diverting aircraft and commodities, or missing service all together. We present an optimization approach that can capture and evaluate the effects of different operating policies. Specifically, we compare and contrast three different strategies, namely: 1) minimizing schedule delay, 2) minimizing the number of service failures, and 3) minimizing the combined cost of operations and service failures. We provide proof of concept by implementing our optimization models and evaluating them using several representative scenarios and conducting computational experiments. The solutions, which are highly dependent on user-defined parameters, represent tradeoffs between costs of operations and service failures.; by Jennifer C. Cheung.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.; Includes bibliographical references (p. 93-96).

‣ Water balance investigations of groundwater depletion in Asia : information needs and uncertainty analysis

Kiang, Julie E. (Julie Ega), 1971-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 101 leaves; 5507596 bytes; 5507404 bytes; application/pdf; application/pdf
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Irrigated agriculture is an essential component of global food production. In many regions of the world, and Asia in particular, groundwater is a major source of irrigation water. Over-pumping of groundwater aquifers has depleted storage in some areas. Quantification of the degree to which groundwater is being used unsustainably is critical to our understanding of the stability of irrigated agriculture. In this study, we investigate the feasibility of estimating groundwater storage changes using the water balance equation and currently available sources of global data. We employ multiple measurements of each water balance component and a constrained least squares estimation method in order to reduce uncertainties. Global datasets of precipitation, evapotranspiration, and runoff were obtained and evaluated for suitability for use in the water balance. In order to fill gaps in the existing data, we developed a new estimate of evapotranspiration based on NDVI measurements and land use information. Results are presented for the continental U.S. and for our study region in Asia. We also show that multiple regression of runoff against basin characteristics can provide additional runoff information in ungaged basins. The water balance can be used as a screening tool for poor quality data...

‣ Analysis and comparison of connections in steel structures

Manson, Leigh (Leigh Caroline)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 55 leaves; 3021738 bytes; 3023947 bytes; application/pdf; application/pdf
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The topic of connections is often given only limited attention in structural analysis and design of buildings, despite the fact that they can play a critical role in the structure. It is customary practice in the U.S. for the structural engineer to design the structural members, but leave the connection details to the steel fabricator. While this practice is more efficient and pragmatic in some instances, it is also necessary for structural engineers to have a good knowledge of connection behavior, especially when dealing with newer or atypical connections. Both the theoretical modeling of connections and the physical geometry and components of connections are considered in this thesis. For the theoretical modeling of connections, the concept of semi-rigid connections as an alternative to the conventional idealizations of perfectly pinned or rigid connections will be addressed. Included will be methods to model and design semi-rigid connection behavior within frames. The effects of connection behavior on frames will also be considered.; (cont.) With regard to the physical components of connections, an overview of types of fasteners and joints will be presented, including types and methods of installing bolts and welds, shop-welded...

‣ Efficacy, national/international practices and motivational factors of lifelong driver education for the aging population

Israels, Richard (Richard Steven)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 182 leaves; 10929297 bytes; 10936965 bytes; application/pdf; application/pdf
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In a society facing a significant increase in its aging population, older driver education/training is emerging as a potential solution to help seniors drive more safely, thus maintaining their mobility and quality of life. Nonetheless, sufficient evidence has not emerged directly linking such programs to significant reductions in accident rates for seniors. But older driver education has produced certain outcomes that have been indirectly linked to driver safety. Among these secondary outcomes that led to significant reductions in crash rates are increases in self-regulation (i.e., modifying driving behavior to compensate for certain physical limitations) and a measure of visual/perceptual ability called Useful Field of View (UFOV). Despite some questions surrounding the efficacy of these programs, older driver courses are offered in the United States and internationally among various countries of the Organization for Economic Cooperation and Development (OECD). Many of the courses address similar core topics such as the effects on driving from certain physiological, cognitive changes that accompany aging. On the other hand, the programs can vary more on structural/administrative factors. For example, many courses in Europe offer behind the wheel training to supplement the material learned in the classroom.; (cont.) For other courses...

‣ Essays on airport and airway congestion

Schorr, Raphael Avram, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166 p.
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Runway and airspace congestion are the primary causes of flight delays in the US. These delays cost airlines and airline customers billions of dollars per year. This thesis consists of two essays. The first essay focuses on several of the commonly proposed market-based solutions to airport congestion. Most of the literature on these market-based solutions has assumed that these remedies are justified by welfare economics, but there is relatively little focus on these justifications. We explore the economic arguments for and against using various market-based approaches to treating airport congestion. The second essay examines the relationship between aviation infrastructure pricing and congestion. Aviation taxes (and some airport fees) are currently designed to tax large aircraft more than small aircraft and flights with more passengers more than flights with few passengers. Several authors have argued that these taxes and fees create an incentive system for airlines to use small aircraft with high frequency, which exacerbates the congestion problem. We study this effect by developing a game theoretic model of airline behavior.; (cont.) Using this model, we are able to find a pure-strategy Nash equilibrium behavior for any given set of taxes and fees. These equilibrium results allow us to directly test the potential effects of changing the fees and taxes. We propose an alternative system of taxes and airport fees that charges all similar flights equally...

‣ The intelligent container concept : issues, initiatives, and implementation

Bryn, Peter Christopher
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 111 p.
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Shipping containers have been under increased scrutiny in recent years for two primary reasons. Within the private sector, they are one component of a continuing process by organizations to use effective supply chain management to their competitive advantage. Within the public sector, they are the central focus of a growing concern over cargo security. Indeed, these issues involve many parties, including regulators, carriers, shippers, container solution providers, research, and academia. Many of the proposed solutions involve new strategies, systems, and technologies applied to containers that fall into what this paper calls the "intelligent container concept." As a relatively nascent field, information is currently very fragmented, standards are still being researched, and few universal goals exist. This study is focused on compiling, understanding, and organizing the universe of options available, the concerns of the parties involved, the relevant and significant initiatives underway or completed, and the issues surrounding implementation.; (cont.) While cost and technology are critical components of the debate, this study focuses more on the benefits that the proposed solutions might add and how they can be incorporated into the supply chain. This study is intended to familiarize the reader with the status and extent of the intelligent container field...

‣ Sliding contact at plastically graded surfaces and applications to surface design

Prasad, Anamika, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 171 p.
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Tailored gradation in elastic-plastic properties is known to offer avenues for suppressing surface damage during normal indentation and sliding contact. These graded materials have potential applications in diverse areas such as barrier coatings for structural components and industrial tools. The gradient in plastic properties is of greater significance for such tribological applications due to the higher level of plastic strains. However, no systematic study exists to predict the impact of plastic gradients for such abrasive events. Such a study is required, both for a fundamental understanding of the plastic gradient effects, and for a practical requirement of the design of graded surfaces. In this work, the effects of the plastic gradient on the surface deformation and hardness response are investigated through systematic experiments and simulations of the scratch test. For the case of the linear increase in the yield strength, some of the fundamental questions related to the mechanism of behavior are addressed, and its implications in the design of graded surfaces are discussed. Through derivation of dimensionless functions, a simple framework is developed to predict the scratch test response of such materials.; (cont.) A model plastically graded nanostructured Ni-W alloy is chosen for the experimental evaluation. In this material system...

‣ Scheduling services and security ticket token services in iLab interactive services

Mao, Tingting
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 leaves
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The iLab architecture allows students to execute laboratory experiments remotely through internet. It supports three different kinds of experiments: batched, interactive and sensor-based. The iLab Interactive Experiments architecture includes the following servers and services: the Interactive Service Broker (ISB), the Experiment Storage Service (ESS) and the Lab Server (LS). In addition, students execute interactive experiments by running a Lab Client (LC). In order to support interactive experiments which require scheduled access, the iLab interactive architecture envisions scheduling servers and services which enable students from different campuses to reserve time periods to execute experiments. Since the user side and lab side require different scheduling functionalities, a user-side scheduling server (USS) and a lab-side scheduling server (LSS) are introduced in the iLab Interactive Services to manage reservations. In the first part of this thesis, the philosophy of the scheduling services design and the implementation will be illustrated in detail. In dealing the security issues in the iLab interactive architecture, the complexity of the higher level authentication between iLab processes increases when one considers collaboration between domains. In second part of this thesis...

‣ Modeling and mapping of MaeLa refugee camp water supply

Rahimi, Navid
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 190 p.
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This thesis describes the development and use of a model, using the EPANET computer code, to simulate the three-hour intermittent MaeLa refugee camp water supply. In coordination with Aide Medicale Internationale, a field survey and pressure, flow and salt tracer testing were conducted as a basis to model the water distribution system in MaeLa, Thailand. The collected data was assembled in EPANET and controls were added to best represent the functioning of the water system and to simulate the calibration tests. The model simulated field parameters successfully despite inaccuracies in elevation due to imprecise instrumentation. The model served as a tool to further understand the dynamics of the system such as mixing in the supply tanks, connections between subsystems and system controls. The distribution model was used to evaluate three alternative scenarios to improve system performance. The objective of the first and second scenario was to increase the flow rate at taps of low supply; the third scenario aimed at adding taps to parts of the camp without easy access to running water. The first scenario consisted in opening valves to connect subsystems: it increased the flow rate at taps of large supply more so than at taps of low supply. This scenario was not recommended because it would quickly drain parts of the water supply. The second scenario consisted in adding connecting pipes between subsystems of high pressure and those of low pressure. It was recommended because it would increase the flow rate of low and medium supply taps. For the third scenario...

‣ Sizing the first flush and its effect on the storage-reliability-yield behavior of rainwater harvesting in Rwanda

Doyle, Kelly C. (Kelly Carroll)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 151 p.
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Rainwater harvesting is a technology used to supply water for domestic purposes in developing countries. Rooftop rainwater harvesting involves collection of rainwater from a rooftop via a guttering system and storage in a cistern. During dry weather, dust and other pollutants accumulate on the roof surface and are washed off at the beginning of the next rain. The initial contaminated volume of water flowing from a roof after a rainstorm is known as the first flush and research has shown that diverting it from the main supply can improve the quality of stored water. This thesis considers a variety of design options for rainwater harvesting, set in the context of rural Bisate Village in northwestern Rwanda. Fieldwork evaluated the potential for rainwater harvesting at three community-scale locations; a health clinic, a primary school, and a house for gorilla trackers and by analysis of the water quality, sought to characterize the first flush phenomenon using an apparatus to collect discrete time-sequenced volumes of runoff. The reliability of a rainwater harvesting system is a measure of its ability to produce the water needed by the system users and depends partially upon the rainfall distribution of the area, the size of the collection roof...

‣ Past and future of grid shell structures

Paoli, Céline (Céline Aude)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 63 leaves
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Because of their original organic shape and the column free space that they provide, the design of grid shell structures challenges architects and structural engineers in more than one way. Very few grid shell building exist around the world. This scarcity may be explained by the level of innovation required in such fields as design technique; construction scheme, use of material... The goal of this paper is to unify the design work done on grid shells, to understand the evolution of the designs and to provide the reader with a sense of what awaits grid shell structures in the future. The construction of a timber grid shell starts from a flat, two dimensional wooden net, the three dimensional shell type structure is then achieved by pushing on the edges of this mat and gradually releasing the internal stresses at the joints to enable the shape to live and the structure to take its most adequate form. Only three wooden grid-shell structures exist world wide, by studying the way they work and behave, as well as the process that lead to the choice of such a structure, we'll understand how grid shell were born in the mind of architects and structural engineers.; (cont.) Even if the mechanism of grid shells is a very clever and well thought system...

‣ Cross-sectional epidemiological study on water and sanitation practices in the northern region of Ghana

Peletz, Rachel Louise
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 134 p.; 8449207 bytes; 8454799 bytes; application/pdf; application/pdf
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A cross-sectional epidemiological study was conducted to obtain baseline data on drinking water and sanitation practices in the Northern Region of Ghana. This study was performed in conjunction with Pure Home Water (PHW) which aims to provide safe drinking water to the Northern Region of Ghana by selling household water treatment and safe storage devices as a sustainable business. Currently ceramic filters constitute PHW's major sales. In the study, fifty households were surveyed, including both homes that had and had not purchased the PHW products in order to obtain baseline data and product feedback. Targeted participants were mothers of the households with children under five. At each household, drinking water samples were collected and analyzed for bacterial contamination with hydrogen sulfide (H2S) and membrane filtration testing techniques. This data is analyzed as an epidemiological cross-sectional study and basic risk assessment. In general, the surveys were well received within the communities, resulting in 100% participation. The product users responded positively to the PHW technologies, with 93% of customers still using the products within six months of purchase.; (cont.) From the overall survey results, there is a great need for safe water and sanitation in the Northern Region of Ghana...

‣ Long-term management and discounting of groundwater resources with a case study of Kukio̕ Hawaii̕

Duarte, Thomas Kae̕o, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 182 leaves; 10589047 bytes; 10588805 bytes; application/pdf; application/pdf
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Long-term management strategies for groundwater resources are examined with theoretical examples and with a case study of Kuki'o, Hawai'i. In Part I a groundwater mining and a dryland salinization optimal management problem are solved analytically, and used to examine the implications of how one values the future through discounting. Exponential and hyperbolic discounting functions are tested with the full range of discount rates and time-scales for the hydrologic system. While the optimal management strategies change depending on the form of the discounting function, they are relatively insensitive to the discount rate itself. For all solutions an initial Dirac delta of pumping brings the system from initial conditions to the optimal trajectory. Following this initial spike of pumping, the exponential pumping solutions are constant over all time. The hyperbolic pumping solutions are more complex, time-dependent functions and they asymptotically approach the no-discounting solution at late times. In Part II a hydrologic-economic model is constructed for a dual coastal and high-level aquifer system at Kuki'o, Hawai'i. The high-level aquifer is modeled as a leaky bucket, while the coastal aquifer is modeled using a sharp-interface formulation of the basal lens. Salinization of pumping wells due to saltwater upconing is superimposed upon the sharp-interface model using an empirical equation based on data from the area.; (cont.) Energy costs...