Página 8 dos resultados de 2122 itens digitais encontrados em 0.026 segundos

‣ Investigation factors that control trace metal toxicity in coastal systems : a temporal and spatial analysis of kinetically inert copper in Boston Harbor

Fitzmaurice, Arthur G., 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 71 p.; 2651674 bytes; 2658782 bytes; application/pdf; application/pdf
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(cont.) form of inert Cu. Correlations between Cu concentrations and total suspended solids at one sampling location suggested that sediment resuspension may be a source of inert Cu to coastal waters. Consistently significant inert Cu concentrations at a site near a salt marsh implied that the presence of sulfides may result in formation of inert Cu. No correlation between inert Cu and chlorophyll a was observed, suggesting that biological formation of inert Cu compounds in situ did not occur in this system. Whether Cu is added to surface waters as existing inert Cu compounds or as inert Cu that is formed when exchangeable Cu reacts with certain constituents in surface waters remains a subject for future work.; Understanding how Cu reacts with constituents in coastal waters and interacts with biota is important for predicting Cu toxicity. It was recently shown that some of the Cu in coastal waters is present in kinetically inert forms that are not released from strongly bound compounds and do not bind to a strong synthetic ligand, remaining undetectable by competitive ligand exchange / adsorptive cathodic stripping voltammetry (CLE-ACSV) on time scales relevant to natural processes (48 hours). Inert Cu seems to be irreversibly bound to strong ligands or physically sequestered within organic and inorganic matrices such that it is likely non-toxic. The primary objective of this work was to collect an extensive data set on one site...

‣ Analysis of radiation mechanism and polarizing properties of metamaterials

Nikku, Madhusudhan, 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 80 p.; 3502547 bytes; 3511013 bytes; application/pdf; application/pdf
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(cont.) isotropic permeability. The characteristics used as a basis for comparison are: 1. Leakage of light (transmittance) through a pair of crossed-polarizers, and 2. Fresnel coefficients of a single polarizer. The expressions for the transmittance and the Fresnel coefficients are obtained analytically using the kDB method. A novel procedure to determine the angles of transmission of the ordinary and extraordinary waves through a uniaxial slab is developed, along with the procedures for validation. The viability of enhancing the performance of polarizers by using metamaterial media is investigated.; Metamaterials are media have a negative permittivity (epsilon) or a negative permeability (mu) or both. Metamaterials promise tremendous advances in lensing applications, antenna technologies and the like. In the present research, the radiation mechanism of metamaterial composites made up of pairs of S-shaped structures (also known as S-rings) is studied in detail. Numerical simulations using the Ansoft HFSS [TM] software package, lead to an understanding of the currents induced on a single S-ring due to a plane wave excitation. The current density observed along a single ring is expressed as a periodic function of the distance along it...

‣ Diversity and phylogenetic structure of two complex marine microbial communities

Klepac-Ceraj, Vanja, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 106 p.; 5426635 bytes; 5439562 bytes; application/pdf; application/pdf
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(cont.) competitive mechanisms are too weak to purge diversity from within them.; Molecular surveys have revealed that microbial communities are extraordinarily diverse. Yet, two important questions remain unanswered: how many bacterial types co-exist, and do such types form phylogenetically discrete units of potential ecological relevance? This thesis explores these questions by investigating bacterial diversity in two complex marine communities (coastal bacterioplankton and sediment sulfate-reducing bacteria) by (i) comprehensive analysis of large 16S rRNA clone libraries, and (ii) refinement and application of parametric diversity estimators. Identification and correction of sequence artifacts demonstrated their potentially significant contribution to diversity estimates. Still, hundreds of unique rRNA sequences (ribotypes) were detected in the corrected libraries, and extrapolation to community diversity with commonly used non-parametric diversity estimators suggested at least thousands of co-existing ribotypes in the two communities. However, close inspection revealed that the non-parametric estimators likely lead to underestimation of ribotype diversity in the clone libraries. Thus, an improved parametric method was developed and shown to closely fit the data. The extrapolated total ribotype diversity in the sample by the improved method was up to one order of magnitude higher than estimated with common non-parametric approaches. Most significantly...

‣ Current technologies and trends of aluminum design

Chen, Michael, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 50 p.; 3400987 bytes; 3404877 bytes; application/pdf; application/pdf
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A literature review of current aluminum technology in the building and construction industry was carried out. Aluminum is an ideal material for building in corrosive environments and for building structures where small dead loads are desired. This has led to the increased use of aluminum in industrial areas and bridge retrofitting projects. By replacing conventional concrete decks of a bridge with aluminum decks, not only is the dead load red load capacity of the bridge is increased. However, there are design issues related with aluminum construction that must be carefully considered. Issues such as welding and temperature effects play a major factor in the application of aluminum in design and construction. Depending on the alloy and temper, welding of aluminum can reduce the strength of an aluminum alloy by half in heat-affected zones. A life cycle assessment of aluminum production is discussed. Green-house gas emissions from aluminum production over the past several decades have declined consistently due to new smelting technologies. In addition, a great amount of aluminum in use today is recycled aluminum. As engineers and architects look for more sustainable solutions and the price of the metal continues to decline, aluminum offers designers an attractive and viable solution.; by Michael Chen.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ Creation and deployment of the NEREUS autonomous underwater chemical analyzer and Kemonaut, an odyssey class submarine

Camilli, Richard, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 341 p.; 17047155 bytes; 17046956 bytes; application/pdf; application/pdf
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NEREUS is a compact self-contained low-power submersible membrane-inlet mass spectrometer, designed to measure dissolved volatile gasses in the water column. It is capable of intelligent data collection, analysis and state-based mission control while operating as a stand-alone instrument or onboard the Kemonaut autonomous underwater vehicle (AUV). Kemonaut is an Odyssey class AUV with increased payload carrying capacity and dynamic stability, and is intended for freshwater and coastal marine applications to depths of 300 meters. The NEREUS-Kemonaut system characteristics allow for greatly improved dissolved gas data collection rates, accuracy and mapping resolution over presently available technologies. Applications particularly well suited for the NEREUS-Kemonaut system include identification and mapping of pollution sources such as chemical spills, investigation of enigmatic freshwater and marine ecosystems, assessment of subsurface natural resources and estimation of marine-related greenhouse gas cycling.; by Richard Camilli.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.; Includes bibliographical references (p. 175-181).

‣ Schedule and cost estimate for an innovative Boston Harbor concert hall

Coste, Amelie, 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 77 leaves; 3060851 bytes; 3060660 bytes; application/pdf; application/pdf
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This thesis formulates a cost estimate and schedule for constructing the Boston Concert Hall, an innovative hypothetical building composed of two concert halls and a restaurant. Concert Halls are complex and expensive structures due to steep design requirements reflecting their status as signature buildings and because they require extensive furnishing. Restaurants are not as complex but require the same kind of attention in their interior furnishing as well as in the choice of their kitchen equipment. Because the structure houses two complicated entities, feasibility analysis required a careful cost and schedule estimation. On the basis of several assumptions, a rough estimate of the cost and schedule of the entire structure has been developed along with a more detailed estimate of the two auditoriums and the restaurant. The study suggests that the interior finishing of such unique buildings represent a large fraction of their overall costs and construction time.; by Amelie Coste.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.; Includes bibliographical references (leaves 75-77).

‣ Ductility enhancement of high performance cementitious composites and structures

Chuang, Eugene (Eugene Yu), 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 319 p.; 15990178 bytes; 16005039 bytes; application/pdf; application/pdf
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High performance cementitious composites (HP2C) are a new generation of fiber reinforced cementitious composites (FRCC) with substantial improvements in mechanical behavior. The most important development in these HP2C materials may be the nearly elasto-plastic ductile behavior, which allows safe exploitation of the tensile and shear capacity in structural elements. This thesis presents a comprehensive investigation into the ductility enhancement of HP2C structures. Beginning at the micromechanical level, sources of ductility are examined and micro-to-macro relations are derived from homogenization theory and fracture mechanics. These micro-to-macro relations form the basis for a novel 3-D two-phase material model, which captures macroscopically observed behavior. Currently existing models which describe the mechanical behavior of FRCC are often micromechanical in nature. However, this macroscopic approach permits one to model the mechanical behavior of HP2C in a continuous fashion, i.e. through the various states of cracking in HP2C, while capturing - through the two-phase composite structure of the model - the micromechanical sources of energy dissipation in the fiber reinforced composite.; (cont.) The 3-D model is implemented in a finite element program to simulate the behavior of two HP2C applications: a flexural girder and a shear girder...

‣ Job accessibility and journey to work : the case of Boston Metropolitan area

Chung, Jee-seong, 1969-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 109 leaves; 9546356 bytes; 9550912 bytes; application/pdf; application/pdf
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In this study, variations in levels of transit usage to work from block groups in the Boston metropolitan area were explored. The examination of the 2000 Census data showed that there were significant differences in the transit share of the work trip at the block group level. In order to understand this variation, which is required to plan and implement transportation policy in the region, the study area was categorized into three groups based on the level of relative job accessibility. Commuting patterns in these areas were examined and compared to each other. First, the conceptual and measurement issues surrounding accessibility are reviewed. Next, travel time impedance functions were developed using the journey to work data from Census Transportation Planning Package (CTPP) 2000, considering both transit and auto travel time between all origin-destination pairs in the Boston Metropolitan area thanks to the Central Transportation Planning Staff (CTPS), the transportation network data from Massachusetts Geographic Information Systems (MassGIS), and the job location data from Initiatives for a Competitive Inner City (ICIC).; (cont.) Then, job accessibility by auto and transit were calculated based on a hypothesis that job accessibility is an important factor in determining transit mode share from both residential and workplace perspectives. Finally...

‣ Simulation of models and algorithms for wireless communication systems

Jabbour, Imad W
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 61 leaves
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The thesis presents a set of simulations of models and algorithms for wireless communication systems. The simulations are developed using graphical MATLAB interfaces, and cover the fundamentals of wireless channel modeling, the advantages and limitations of antenna beamforming in multiuser systems, and the underlying principles of OFDM. The thesis targets two types of audiences in particular: students and wireless industry professionals. For the former, it constitutes an excellent complement to lecture notes, and for the latter, it is an efficient way to review the key principles and technologies. In either case, the simulations provide an intuitive view of the addressed topics, thus allowing users to comprehend the basics of wireless channels and phenomena without delving into mathematical complexities.; by Imad W. Jabbour.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (leaf 61).

‣ Water quality and business aspects of sachet-vended water in Tamale, Ghana

Okioga, Teshamulwa (Teshamulwa Irene)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 168, [1] leaves
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Microbial water quality analyses were conducted on 15 samples of factory-produced sachet water and 15 samples of hand-tied sachet water, sold in Tamale, Ghana. The tests included the membrane filtration (MF) test using mColiBlue24® medium, 3MTM PetrifilmTM test, and Hydrogen Sulfide Presence Absence (P/A H2S) test. With the MF method, 1 factory-produced and 1 hand-tied sachet-water sample had E.coli counts of 5 CFU/100ml and 49 CFU/100ml respectively. Almost half (47%) of the factory-produced sachet-water samples had some total coliforms (range from 1 CFU/100ml to 115 CFU/100ml). All the 15 hand-tied sachet-water samples had total coliforms (range from 4 CFU/100ml to 2010 CFU/100ml). One sample recorded TNTC at a dilution factor of 10. The MF method showed little correlation with the 3MTM PetrifilmTM method (R=0. 16). With the 3MTM PetrifilmTM test method, none of the factory-produced sachet-water samples had E.coli and only one sample had total coliforms with 100 CFU/100ml. The hand-tied sachet-water sample with 49 E.coli CFU/100ml in the MF test, turned out to have 100 CFU/100ml in the 3MTM PetrifilmTM test. The MF test results were considered more reliable.; (cont.) For the P/A H2S test, 7% of factory-produced sachet-water samples and 27% of the hand-tied sachet-water samples returned positive results. Overall...

‣ Effects of water on chemomechanical instabilities in amorphous silica : nanoscale experiments and molecular simulation

Silva, Emílio César Cavalcante Melo da
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 114 leaves
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We elucidate the tensile failure mechanism of amorphous silica and the effects of water on the process, combining: (a) atomic force microscope (AFM) bending tests, (b) molecular dynamics (MD) simulation and (c) molecular orbital (MO) simulation. Bending tests of silica nanowires provide validation for the predictions of the simulations, in which we study the failure of dry silica using MD and define a representative system to be studied with the more chemically accurate MO method. We used the AFM to perform bending tests on silica nanowires of diameter D < 1 [mu]m, which have very high surface-to-volume ratio and no microscopic flaws. No size effects on elastic modulus were observed down to 130 nm. For 500 nm wires, water reduces the strength from 10.5 GPa in air to 6.5 GPa in water, results comparable to those reported for micrometer-scale fibers. By probing the strength of silica at this scale, we bring experiments to the length scales accessible to atomistic simulation. Using classical MD, we found that crystalline silica fails globally by crack nucleation, but amorphous silica displays plastic deformation due to the formation of local defects, which cascade into larger compound defects. We extend to amorphous systems the instability criterion for material failure and use the Lanczos iteration method to isolate unstable modes. Failure of these modes create local defects...

‣ GIS representation and assessment of water distribution system for Mae La Temporary Shelter, Thailand; Geographic information systems representation and assessment of water distribution system for Mae La Temporary Shelter, Thailand

Harding, Mary Pierce
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 57 leaves
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ArcGIS is used to analyze water access in Mae La, Thailand, home to 45,000 residents living as refugees in a temporary camp. Drinking water for the shelter is supplied at public tap stands while water for hygienic purposes such as bathing and laundry is available via covered rope-pump wells which reach shallow ground water; stream and river surface water; and hand-dug wells. In all, 7,117 homes were identified using Google Earth and the corresponding proximity to the nearest tap stand and rope-pump well was calculated. ArcGIS was used together with an EPANET water-distribution model created by Rahimi (2008) to evaluate the predicted daily volume of drinking water available per home. Overall this research shows that the vast majority of residents in Mae La have sufficient access to water. Homes located further than 115 meters from a tap stand, located further than 180 meters from a rope-pump well, or having access to less than 50 liters of water per day were considered a cause for concern. Approximately one in four homes met these criteria. Only 5% of homes are located more than 115 meters from a tap stand. Approximately 14% of homes did not meet the rope-pump proximity criterion, and 15% of homes did not meet the available volume criterion. The tap-stand proximity results provide a much higher degree of confidence compared to the other results. Alternative sources for hygienic water besides rope-pump wells exist...

‣ Price competition in the top US domestic markets : revenues and yield premium

Pyrgiotis, Nikolas
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 132 p.
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Since 2000 the US airline industry has gone through a severe crisis which initiated important changes in the competitive environment of the industry. The economic downturn, the fierce competition between Legacy carriers, the rapid expansion of Low Cost carriers, the soaring fuel prices and the 9/11 attacks are some of the reasons that put many US airlines into a financial crisis. Many of the traditional major US airlines were forced into bankruptcy during the first five years of the decade. That forced Legacy airlines to change their pricing strategies to better match their LCC competitors and stimulate demand. This thesis concentrates on the pricing and competition between Legacy and low cost carriers in the US domestic markets by analyzing the Top 1000 US domestic markets. A new metric is introduced, the yield index, that compares fares among airlines in specific markets in order to quantify the fares collected by major airlines with respect to their competitors in different segments of the domestic market. Furthermore a quantitative analysis of competition is performed to identify important changes during the years of the crisis. The average fare gap between Legacy carriers and LCCs that existed in 2000 was shrinking until 2005. The traffic and revenue losses of Legacy carriers combined with the rapid expansion of LCCs have also mitigated the market share difference and revenue difference between Legacy and LCC carriers. Legacy carriers were forced out of numerous domestic markets by new competition. Overall...

‣ Mixing processes and hydraulic control in a highly stratified estuary

MacDonald, Daniel George, 1970-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 214 p.; 14325658 bytes; 14325370 bytes; application/pdf; application/pdf
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This thesis utilizes field data from the Fraser River Estuary, a highly stratified system located in southwestern British Columbia, Canada, to investigate the nature of mixing processes in a highly stratified environment, and to extend two-dimensional hydraulic theory to a three dimensional environment. During the late ebb, a stationary front exists at the Fraser mouth. Although densimetric Froude numbers in the vicinity of the front are supercritical in a frame of reference parallel to the local streamlines, the front itself is oriented such that the value of the Froude number is equal to the critical value of unity when taken in a frame of reference perpendicular to the front. This observation presents a robust extension of established two-dimensional, two-layer hydraulic theory to three dimensions, and implies similarity with trans-sonic flows, in that a Froude angle can be used to identify critical conditions in a manner similar to the Mach angle. Mixing processes were evaluated at the mouth during the late ebb using a control volume approach to isolate mean vertical entrainment processes from turbulent processes, and quantify the vertical turbulent salt and momentum fluxes. Observed turbulent dissipation rates are high, on the order of 10-3 m2s-3...

‣ Agency and incentive contract in private investment of transport project : an exploration of fundamental relationships

Chiang, Risharng
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 177 p.; 12917212 bytes; 12916971 bytes; application/pdf; application/pdf
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This thesis codifies and relates critical incentive-design and financial-contracting issue to the unique principal-agent circumstances generated from private investment of transport infrastructure and provides a framework for designing incentive contract and increasing future economic efficiency gains (or minimizing loses). In the mathematical form, we uniquely integrated multitask agency and common agency into our modeling. The outcome could be simplified as: the equilibrium with n principals is exactly as if there is just one hypothetical principal with an objective function that is the sum of all the separate principals' objectives, but the agent's risk aversion is multiplied n-fold. Remember that the more risk averse the agent, the lower the power of the incentive scheme. Thus, the Nash equilibrium incentive scheme with n principals has, roughly speaking, only (/n)-th the power of the second-best scheme that would be offered by one truly unified principal. With promotion of incentive competition among the Government and the Board the incentives can be more powerful than those in the second-best. The reason is that each must now use a positive coefficient on the component of output that is of direct concern to him in order to divert the CEO from tasks that benefit the other. This competition among the Government and the Board leads them to raise those coefficients to higher levels. The most important predictions of the theoretical model are as follows. First...

‣ A lean enterprise approach for developing high speed rail in Japan and Portugal

Iwamura, Nobuhiro
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166 p.
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This thesis explores and evaluates the application of the lean enterprise concept to the expansion and development of the high speed railway industry in Japan. The basic idea of the lean enterprise is increasing value-added processes, eliminating waste, and creating equitable value delivery throughout the enterprise. It also focuses on both radical change and continuous improvement. The application of the lean enterprise concept to the railway industry, a service industry, is the first such example. Therefore, the aim is not only to consider the future strategy of the new high speed rail in Japan, but also to assess whether lean enterprise architecting is applicable to the new construction projects of railway industry. First, this thesis looks back at the history of the Japanese railway system and examines the details of the present Shinkansen railway system. It then makes an international comparison with the United Kingdom and German railway systems to be utilized it in the later analysis. Next, the Enterprise Value Stream Mapping and Analysis (EVSMA) is applied to the new extended Shinkansen projects in Japan, providing suggestions that for strategy that can offer the projects some advantages from the lean enterprise perspective.; (cont.) The results suggest that the lean enterprise concept is very suitable for the development of railway industries to enhance the total enterprise performance...

‣ System design and requirements for Automated Law Review Submission System; System design and requirements for ALRSS

O'Shea, Colleen Ruth, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 143 leaves; 5105524 bytes; 5105331 bytes; application/pdf; application/pdf
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The submission of manuscripts by Authors to Law Reviews is presently an inefficient process for both parties. The integration of technology allows for improvements to this process as can be seen in ExpressOTM and the Stanford Law Review's Electronic Submission System. The Automated Law Review Submission System (ALRSS) was developed to make the submission process even more efficient and effective than present systems allow. This is a software design thesis with emphasis on the System Requirements developed for the ALRSS. The method of developing System Requirements started with discussing the present process with Authors and Law Reviews and determining current needs of the users. Afterwards, a comparison among competitors was discussed to generate limitations of these systems and determine features to emulate for the development of ALRSS. Thirdly, a workflow model was created to examine internal issues of submission tracking and management within the Law Review to further automate the review process and make management of the process more effective. As a result, a more efficient and effective submission process is feasible for both the Author and Law Review by allowing processes to occur electronically from the Author submitting a manuscript to a Law Review Editor assigning or viewing a manuscript. In addition...

‣ Integrated optimization model for airline schedule design : profit maximization and issues of access for small markets

Garcia, Flora A., 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 100 p.; 4427821 bytes; 4439324 bytes; application/pdf; application/pdf
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The purpose of the National Airspace System Strategy Simulator is to provide the FAA with a decision support system to evaluate long-term infrastructure and regulatory strategies. The NAS strategy simulator consists of several modules representing the different entities within the NAS embedded in a system dynamics framework. The MIT Airline Scheduling Module is the module within the NAS Strategy Simulator that represents the decision making process of the airlines with respect to the schedules that they fly. The MIT Airline Scheduling Module is an incremental optimization tool to determine schedule changes from one time step to another that best meets demand using available resources. The optimization model combines an Integrated Schedule Design and Fleet Assignment model and a model, based on Passenger Decision Window model, that determines passenger preference for itineraries. We simultaneously establish frequency, departure times, fleet assignment, passenger loads and revenue within a competitive environment. Optimization methods often lead to extreme schedule decisions such as eliminating service to markets, often small markets, that are not financially profitable for the airlines. This is of grave concern to government policy makers as rural access to markets...

‣ Measuring congestion and emissions : a network model for Mexico City

Amano, Yasuaki Daniel, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 58 p.; 2082818 bytes; 2082626 bytes; application/pdf; application/pdf
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Congestion is a major problem for the major cities of today. It reduces mobility, slows economic growth, and is a major cause of emissions. Vehicles traveling at slow speeds emit significantly more pollutants than vehicles traveling at free flow speeds. It is therefore important to determine the extent of congestion in a city, and its impact on the environment. This thesis focuses on congestion in the Mexico City Metropolitan Area. Mexico City is one of the largest cities in the world, and faces severe levels of congestion and emissions. Although much of the transportation trips are made by high capacity modes such as buses and colectivo microbuses, a growing population and increasing automobile ownership rate will further exacerbate the city's mobility and environment. In order to measure the level of congestion in Mexico City, a network model was built. Combining data from a 1994 origin destination survey and the 2000 census with a digitized roadway network, we were able to determine the state of vehicle speeds on roadways throughout the city. This speed distribution was then used in the MOBILE6 model to estimate the total emissions from road based transportation sources. The network model was also used to study the extent of congestion and emissions for various future infrastructure projects. An analysis was done for a year 2025 growth scenario...

‣ An analysis of the production and manufacture of the modified clay pot at the Oriang Women's Pottery Group, the Amilo-Rangwe Pottery Group, and the Kinda E Teko Pottery Group in Nyanza Province, Kenya

Pihulic, Michael P. (Michael Phillip), 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 127 p.; 6588784 bytes; 6605374 bytes; application/pdf; application/pdf
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In response to the growing demands for safe water supplies and the absence of a central infrastructure capable of meeting those demands, CARE-Kenya has implemented a safe water storage program at the household level. Central to this program is the modified clay pot, a hybrid of traditional Kenyan pottery and safe water storage principles. The modified clay pot exhibits a flat base for stability, a narrow neck to prevent access and thus reducing the chances of contamination, a standardized size in order to be compatible with chlorine dosing standards, and a tap at the base to provide safe access to the water within. The goal of this thesis is to analyze and record the production and manufacturing methods used by three local pottery groups in rural eastern Kenya using a combination of video, photography and written text. The primary focus of this work is to examine the ways in which the production processes could be improved and refined in order to increase both the efficiency of production, thus reducing the cost, and increase the scale of production, in order to increase availability of the modified clay pot to people within the Nyanza Province of Kenya.; by Michael P. Pihulic; Thesis (M. Eng.)--Massachusetts Institute of Technology...