Página 24 dos resultados de 2122 itens digitais encontrados em 0.040 segundos

‣ Wavelet-based multiresolution data representations for scalable distributed GIS services

Wu, Jingsong, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 160 p.; 13932985 bytes; 13932743 bytes; application/pdf; application/pdf
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Demand for providing scalable distributed GIS services has been growing greatly as the Internet continues to boom. However, currently available data representations for these services are limited by a deficiency of scalability in data formats. In this research, four types of multiresolution data representations based on wavelet theories have been put forward. The designed Wavelet Image (WImg) data format helps us to achieve dynamic zooming and panning of compressed image maps in a prototype GIS viewer. The Wavelet Digital Elevation Model (WDEM) format is developed to deal with cell-based surface data. A WDEM is better than a raster pyramid in that a WDEM provides a non-redundant multiresolution representation. The Wavelet Arc (WArc) format is developed for decomposing curves into a multiresolution format through the lifting scheme. The Wavelet Triangulated Irregular Network (WTIN) format is developed to process general terrain surfaces based on the second generation wavelet theory. By designing a strategy to resample a terrain surface at subdivision points through the modified Butterfly scheme, we achieve the result: only one wavelet coefficient needs to be stored for each point in the final representation. In contrast to this result...

‣ A wavelet-based system for event detection in online real-time sensor data

Varadharajan, Charuleka, 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 78 p.; 3658378 bytes; 3666595 bytes; application/pdf; application/pdf
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Sensors are increasingly being used for continuous monitoring purposes, the process of which generates huge volumes of data that need to be mined for interesting events in real-time. The purpose of this research is to develop a method to identify these events, and to provide users with an architecture that will allow them to analyze events online and in real-time, to act upon them, and to archive them for future offline analysis. This thesis is divided into two major portions. The first discusses a general software architecture that performs the functions defined above. The architecture proposed assumes no prior knowledge of the data, and is capable of dealing with multi-source data feed from any type of sensor(s) on one end, and can handle multiple clients on the other. The second part of the thesis discusses a wavelet-based algorithm for detecting certain types of events in real-time in one-dimensional numeric time-series data. Wavelets were judged to be the most appropriate technique for analyzing random sensor signals for which no prior information is available. The wavelet-based method in addition allows users to delve into different levels of abstraction (based on varying time periods) while looking at the data, which cannot be done by any previous method for real-time event detection. This thesis also touches on the fundamental question of how one defines an event...

‣ Application of lean enterprise concept to construction firms in Japan

Taguchi, Hiroshi, 1973-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 80 p.; 3152647 bytes; 3152450 bytes; application/pdf; application/pdf
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Construction firms in Japan are struggling with the change in construction industry environment and need a new business model to meet the change. On the other hand, Japanese manufacturing companies, especially automobile companies, are at their peak standing on their strong production system, which is called the lean production system. The lean production system has its origin in the Japanese automobile industry and has changed the dynamics of international competition of the manufacturing industry. The construction industry is a non-manufacturing business; however, lean concepts could assist in the development of a new business model in the construction context. This thesis derived lean concepts from the manufacturing industry and examined their applicability for construction firms in Japan, by exploring the business processes of the Japanese construction industry from three perspectives: the production level, the enterprise level, and the extended enterprise level. This thesis revealed that the peculiarities of the construction industry created barriers to reap the full benefit of the lean transformation at the production and the enterprise level. This thesis concluded that the Japanese construction industry should apply lean concepts at the extended enterprise level. A case study of a new airport construction project in Japan supported this conclusion.; by Hiroshi Taguchi.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ Addressing endogeneity in residential location models

Guevara-Cue, Cristián Angelo
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 96 leaves; 5190524 bytes; 5201671 bytes; application/pdf; application/pdf
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Some empirical residential location choice models have reported dwelling-unit price estimated parameters that are small, not statistically significant, or even positive. This would imply that households are non-sensitive to changes in dwelling unit prices or location taxes, which is not only against intuition, but also makes the models useless for policy analysis. One explanation for this result is price endogeneity, which means that the price is correlated with the error term in the econometric model. This problem is caused either by the simultaneous determination of the supply and the demand for dwelling units in aggregated models, or by omitted attributes that are correlated with the price, in the disaggregated ones. The treatment of endogeneity in discrete choice models is an area of ongoing research in econometrics. Therefore, methods to treat this problem began to be proposed only in the last decade, and have not been thoroughly analyzed for residential location models. This thesis evaluated the available methods to treat endogeneity in discrete choice models. Each method was tested in terms of its applicability and robustness in a residential location choice framework, using a set of Monte Carlo experiments. The results showed that the control-function method (Petrin and Train...

‣ Using shape memory alloy as dampers : design methodology; Using SMA as dampers : design methodology

Leong, Siu Loong
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 143 p.; 4250028 bytes; 4255991 bytes; application/pdf; application/pdf
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Many shape memory alloy (SMA) material models have been proposed in the literature, but most are suited only to forward analysis and not to design. This project proposes a generalized friction element, the lambda box, to model the stress-strain curve of SMA during pseudoelasticity. Simulation is carried out to study the dynamic response of such a system under harmonic loading. Three kinds of systems were examined, in order of increasing complexity: the friction damper system, the hysteretic damper system, and the hysteretic lambda damper system, which dynamically is equivalent to the SMA damper system. Using the simulation results, various asymptotes on the design space are identified, and design methodologies for the three systems are proposed. As the determination of the system parameters is decoupled from the actual damper design, a design methodology to dimension and configure the SMA damper is then proposed, for two kinds of problems, initial design and retrofit design.; by Siu Loong Leong.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.; Includes bibliographical references (p. 141-143).

‣ Modeling of ultrasonic processing

Zhao, Wenguang, S.M. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 75 leaves; 2731489 bytes; 2734603 bytes; application/pdf; application/pdf
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This paper presents a finite element analysis (FEA) of ultrasonic processing of an aerospace-grade carbon-epoxy composite laminate. An ultrasonic (approximately 30 kHz) loading horn is applied to a small region at the laminate surface, which produces a spatially nonuniform strain energy field within the material. A fraction of this strain energy is dissipated during each ultrasonic loading cycle depending on the temperature- dependent viscoelastic response of the material. This dissipation produces a rapid heating, yielding temperature increases over 100⁰C in approximately Is and permitting the laminate to be consolidated prior to full curing in an autoclave or other equipment. The spatially nonuniform, nonlinear, and coupled nature of this process, along with the large number of experimental parameters, makes trial-and-error analysis of the process intractable, and the FEA approach is valuable in process development and optimization.; by Wenguang Zhao.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.; Includes bibliographical references (leaves 53-55).

‣ A study of interaction effects due to bored tunnels in clay

Sweeney, Paul, M. Eng. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 59 leaves; 2720466 bytes; 2722850 bytes; application/pdf; application/pdf
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As more and more tunnels are being bored in urban environments it is essential to understand the effects that this will have on adjacent structures, for example, the state of Singapore, which has been expanding its underground transit system extensively. The effects of tunneling twin tunnels in Singapore marine clay are outlined, analyzed and discussed. Three different configurations are taken into account, side-by-side tunnels, piggyback tunnels and angular-offset tunnels, located at a typical depth for Singapore. Empirical correlations, derived from extensive field data, are used to calculate ground movements caused by twin bored tunnel constructions using superposition. Non-linear finite element analysis is used for the same situations, as well as for analyzing the stresses in the tunnel lining. The use of superposition was tested using the non-linear analysis to check whether or not its use with empirical methods is appropriate. Although the numerical solutions suggest that superposition is a good approximation for twin tunnel bores, there is a clear discrepancy in the magnitude and distribution of ground movements calculated by empirical and numerical solutions.; by Paul Sweeney.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ The impact of high frequency/low energy seismic waves on unreinforced masonry

Meyer, Patrik K. (Patrik Kristof)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 89, [1] p.
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Traditionally, the high frequency components of earthquake loading are disregarded as a source of structural damage because of their small energy content and because their frequency is too high to resonate with the natural frequencies of structures. This thesis argues that higher frequency waves travelling through stiff masonry structures can trigger two types of failure mechanisms that have not yet been taken into account. First, the high frequencies can cause small vertical inter-stone vibrations that result in irreversible relative displacements of the stones, which may ultimately lead to collapse. The energy needed to cause this deformation and failure comes largely from gravitational forces. The second failure mechanism is associated with the increase of the outward thrust that results from the partial fluidization and densification of the loose granular inner core of some unreinforced masonry walls. Preliminary results of a series of static and dynamic tests, as well as of numerical models, demonstrate the potentially destructive effects of high frequency/low energy seismic waves on unreinforced masonry structures.; by Patrik K. Meyer.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering...

‣ Active control of extremely prestressed simple supported composite bridges

Dagher, Bahjat (Bahjat Nouhad)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 67 leaves
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More than 600,000 US bridges are considered to be in need of rehabilitation. More than 90 Billion US Dollars is the estimated amount of money required. According to the National Bridge Inventory, 18.5% of those bridges are structurally deficient. Many methods of rehabilitation have been sought out by engineers throughout the years. Perhaps the most interesting of all solutions is utilizing external post tensioning cables to add to the stiffness of the system. External post tensioning can be considered to be a cheap solution that is easy to install, and easy to fix in the future. What has not been discussed among engineers is the possibility of controlling the tendon force. Vertical deflections could be monitored and assessed, and a consequent axial prestressing force could be applied on the cables. This report investigates in detail the issues involved in the design of externally prestressed tendons on a simply supported composite bridge of specific properties, and touches on the reasoning behind active control and the limitations that the current technology has.; by Bahjat Dagher.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2007.; Includes bibliographical references (leaf 67).

‣ Calibration of dynamic traffic assignment models with point-to-point traffic surveillance

Vaze, Vikrant (Vikrant Suhas)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 180 p.
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Accurate calibration of demand and supply simulators within a Dynamic Traffic Assignment (DTA) system is critical for the provision of consistent travel information and efficient traffic management. Emerging traffic surveillance devices such as Automatic Vehicle Identification (AVI) technology provide a rich source of disaggregate traffic data. This thesis presents a methodology for calibration of demand and supply model parameters using travel time measurements obtained from these emerging traffic sensing technologies. The calibration problem has been formulated in two different frameworks, viz. in a state-space framework and in a stochastic optimization framework. Three different algorithms are used for solving the calibration problem, a gradient approximation based path search method (SPSA), a random search meta-heuristic (GA) and a Monte-Carlo simulation based technique (Particle Filter). The methodology is first tested using a small synthetic study network to illustrate its effectiveness. Later the methodology is applied to a real traffic network in the Lower Westchester County region in New York to demonstrate its scalability.; (cont.) The estimation results are tested using a calibrated Microscopic Traffic Simulator (MITSIMLab). The results are compared to the base case of calibration using only the conventional point sensor data. The results indicate that the utilization of AVI data significantly improves the calibration accuracy.; by Vikrant Vaze.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ A critical analysis of bulk precipitation recycling models

Fitzmaurice, Jean Anne
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 162 p.
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Precipitation recycling is the contribution of local land evaporation to the precipitation of a region. The significant local evaporative contribution to rainfall in many continental regions highlights the potential importance of land-atmosphere feedback. This thesis addresses three common assumptions in bulk precipitation recycling models: (1) the use of time-averaged data (2) the neglect of the atmospheric storage term and (3) the well-mixed assumption. Bulk precipitation recycling models have been criticized for their use of monthly mean data in estimating moisture influx, which does not capture the diurnal and synoptic variations important in hydrology. This work uses a method to compute moisture influx using the atmospheric data at the finest time-scale available. Smaller monthly recycling ratio estimates were found when using this new method. Most previous recycling studies are monthly. The atmospheric storage term is added to an earlier recycling model to study the submonthly time-scale. The southwest Amazon region during the wet season is investigated. There the synoptic conditions consist of alternating easterly and westerly regimes of three to fourteen day duration. The resulting recycling ratio spatial patterns are shown to reflect the synoptic circulation patterns.; (cont.) Two parameters are introduced to relax the the well-mixed assumption in the Bras and Eltahir model. Information from a water vapor tracer study and atmospheric reanalysis data are used to estimate parameter values. Applying this model to the central United States region during the summer...

‣ Modification of a biosand filter in the northern region of Ghana

Kikkawa, Izumi
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 127, [1] p.
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Four local plastic design (LPD) BSFs were constructed in Northern Region, Ghana, to test and evaluate an experimental modification of the LPD BSF for treatment of highly turbid water. Modifications of the LPD BSFs were made in order to provide an additional "biolayer," the core layer of a BSF where most removal and degradation of pathogens occur. This adjustment was carried out by providing an additional diffuser basin, with an additional layer of sand in it. Along with two unmodified LPD BSFs, two modified LPD BSFs were built: one with an additional 5-cm sand layer, one with an additional 10-cm sand layer. Filter ripening was confirmed through an increase in turbidity removal after 13 days. All four LPD BSFs removed turbidity by an average of 92-95 % after Day 13, with average effluents of 10 - 16 TU (14 - 22 NTU). The modified BSFs showed slightly higher removal of turbidity after 27 days of operation. This could be an indication that the modified BSFs potentially withstand greater operational variation, or that the modified BSFs require less frequent cleaning. The average total coliform removal after 11 days was 87 % with an average effluent concentration of 430 cfu/100 ml from an influent concentration of 15,000 cfu/100 ml. Concurrently...

‣ Strength of transversely isotropic rocks

Pei, Jianyong, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 339 p.
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This thesis proposes a new Anisotropic Matsuoka-Nakai (AMN) criterion to characterize the failure of transversely isotropic rocks under true triaxial stress states. One major obstacle in formulating an anisotropic criterion is that it usually involves six stress components, instead of three principal stresses. As such, anisotropic criteria usually lead to complicated mathematical expressions, and cannot be directly visualized in three-dimensional space. This problem is solved by introducing the Material Normal Stress System (MNSS), which is the space formed by the three normal stress components reflecting the material anisotropy. Within this system, the failure behavior of transversely isotropic rocks in conventional triaxial tests can be represented with geometrical features in the MNSS. These features are then incorporated into the failure surface of the original Matsuoka-Nakai criterion in the Material Normal Stress System, resulting in the Anisotropic Matsuoka-Nakai criterion. This criterion, combined with the Coulomb criterion, is validated against both conventional and true triaxial test data, that are collected from an extensive literature review. The combination of the AMN criterion and the Coulomb criterion satisfactorily characterizes the measured strength from an extensive program of true triaxial tests on a schist...

‣ General overview of the Nigerian construction industry

Dantata, Sanusi (Sanusi A.)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 83 leaves
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The purpose of this study is to investigate and provide a general overview of the Nigerian construction industry, its role in the national economy, the main participants in the industry, the problems that they face, and the opportunities that exist within the industry. Over the last decade, several changes have occurred in Nigeria, which have helped all sectors of the economy, especially the building & construction sector. With double digit growth rates in the last 3 years, the construction industry has outgrown all other sectors of the Nigerian economy. However, its contribution to the Nigerian GDP and employment of labor are still very low. Despite its impressive performance, the industry faces a significant number of challenges including the lack of local skilled labor, power shortage, the unavailability of materials, and the unethical practices that are very common in the industry. However, several opportunities exist in the industry especially in the ICT, education, and subcontracting sectors which makes it very attractive for investors.; by Sanusi Dantata.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, June 2008.; Includes bibliographical references (leaves 80-83).

‣ The effect of fluid acceleration on sediment transport in the surf zone

Durham, William McKinney
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 184 p.
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The surf zone is defined by highly non-linear, breaking waves that have very different acceleration signatures beneath their respective crests and troughs. The consequences of this dissimilarity on sediment transport is not fully understood. This thesis develops methodologies to predict sediment transport under these asymmetric, skewed waves. Two different transport mechanisms are considered: bedload transport and "subsurface" transport. The potential for subsurface transport was first realized by Madsen (1974) who found that the large pressure gradient beneath a breaking wave was sufficient to drive a substantial porous-media flow, adequate to create a soil-mechanics type failure extending several centimeters into a sandy sediment bed. The theoretical model of Madsen (1974) is extended to obtain estimates of subsurface transport by subdividing the sediment in failure into distinct, kinematically admissible slip circles. An equation governing the rotation of each slip circle is developed, yielding the subsurface sediment's horizontal movement as a function of depth. By integration, subsurface transport can predicted. In addition, a method is developed for estimating bedload transport under breaking waves, accounting for the enhanced shear stress beneath the wave's crest. An existing bedload formula is used as the foundation for this predictive model.; (cont.) The validity of the two predictive models is substantiated by experiments conducted in a laboratory wave flume. Breaking waves are passed over lightweight...

‣ Lane changing models for arterial traffic

Ramanujam, Varun
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 129 p.
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Driving behavior models for lane-changing and acceleration form an integral component of microscopic traffic simulators and determine its value in evaluation of different traffic management strategies. The state-of-art model for lane changing adopts a two-level framework: the first level involves a latent or unobserved choice of a target lane; the second level models the acceptance of adjacent gaps in the direction of the target lane. While this modeling approach has several advantages over past works, it assumes drivers to execute lane change within the same time step in which gap was found to be acceptable. In other words, under time steps typically adopted in model applications, the lane change duration is assumed to be negligibly small. However, past works report average lane change durations to the order of 5-6 seconds. Besides this practical maneuvering requirement, the assumption fails further in moderate or low density traffic conditions with ample gap sizes or low speed conditions, where lane changing maneuver can take longer than average. The work outlined in this thesis proposes an extension to the two-level framework for lane changing models through a third level that explicitly models the lane change duration.; (cont.) Traffic conditions in the driver's neighborhood that are likely to influence lane change duration are accounted for in the third level. The extended model is applied to data obtained from video observations on traffic on a stretch of an arterial corridor in California. Apart from possessing distinctive features including signalized intersections and multiple access locations that result in lower average speeds...

‣ Annotation persistence over dynamic documents

Wang, Shaomin, 1969-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 216 p.; 12022602 bytes; 12050532 bytes; application/pdf; application/pdf
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Annotations, as a routine practice of actively engaging with reading materials, are heavily used in the paper world to augment the usefulness of documents. By annotation, we include a large variety of creative manipulations by which the otherwise passive reader becomes actively involved in a document. Annotations in digital form possess many benefits paper annotations do not enjoy, such as annotation searching, annotation multi- referencing, and annotation sharing. The digital form also introduces challenges to the process of annotation. This study looks at one of them, annotation persistence over dynamic documents. With the development of annotation software, users now have the opportunity to annotate documents which they don't own, or to which they don't have write permission. In annotation software, annotations are normally created and saved independently of the document. The owners of the documents being annotated may have no knowledge of the fact that third parties are annotating their documents' contents. When document contents are modified, annotation software faces a difficult situation where annotations need to be reattached. Reattaching annotations in a revised version of a document is a crucial component in annotation system design. Annotation persistence over document versions is a complicated and challenging problem...

‣ Using keyword-based indexing for desktop content navigation : Desktop Content Manager; Desktop Content Manager

Ravichandran, Deepak, 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 p.; 1979250 bytes; 1979056 bytes; application/pdf; application/pdf
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Researchers and students gather a wealth of information from the Internet. With increasingly affordable large hard disk spaces, much content can be archived in the computer for future reference. However, the only means for organizing this information on today's machines is the folder system. Information on a topic may be spread over many folders. This provides for poor content navigation and retrieval. This thesis describes how the concept of keyword-based indexing can be applied towards navigation of electronic content. The idea is implemented in the form of a software solution - Desktop Content Manager. The information on keywords and content are stored and represented in a manner facilitating automatic hyper linking of related information providing immediate access. The software was tested with sample content extracted from different sources and the scalability and limitations of the suggested approach identified. The findings are used to define further work in this area.; by Deepak Ravichandran.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2004.; Includes bibliographical references (p. 65-66).

‣ High modulus carbon fiber/titanium laminates

Tsang, Lina
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 39 leaves; 1957494 bytes; 1959017 bytes; application/pdf; application/pdf
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Titanium has been used to meet ever-stricter standards for high-temperature performance, creep resistance, low weight and high strength. Having low density, a high melting point, and high tensile strength, it seems like the perfect material for numerous applications. For structural applications where flexural stiffness and strength play the most important role, titanium's high cost can be a restrictive factor. The cost-effectiveness of the material can be increased by using it together with other less expensive high strength and low weight materials in the form of composite laminates. In this investigation, laminates were fabricated using inorganic matrix/high modulus carbon fiber composites with titanium sheets. Laminates were tested in three-point bending to assess the performance of the upgrade. The results show that combining Geopolymer high modulus carbon composites with titanium sheets significantly increases the performance. Laminates provide a lower cost solution for given stiffness and weight requirements compared with other common structural materials, such as steel and aluminum.; by Lina Tsang.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2006.; Includes bibliographical references (leaves 38-39).

‣ Structural opportunities of ETFE (ethylene tetra fluoro ethylene); Structural opportunities of ethylene tetra fluoro ethylene

Robinson, Leslie A. (Leslie Anne), 1982-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 66 leaves; 4413773 bytes; 4420322 bytes; application/pdf; application/pdf
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An exploration of ETFE (ethylene tetra fluoro ethylene) foil cushions was performed in its use for building cladding. ETFE foil cushions consist of alternating layers of ETFE film and air cavities. An inflation system pressurizes the foil cushions prestressing the film layers to carry applied load. The ETFE cushion system is an extremely lightweight plastic offering considerable advantages over traditional cladding materials. ETFE foil cushions are self-cleaning, highly transparent to light, resistant to weathering and can be manufactured in almost any shape and size. Incorporating ETFE into a building's cladding results in a more efficient and low maintenance structure. ETFE foil cushions are successfully being implemented in cladding for botanical gardens, zoo buildings, and swimming pools. ETFE is currently finding its place as an effective alternative to glass in more traditional buildings as roofing for courtyards, atria, and shopping malls.; by Leslie A. Robinson.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2005.; Includes bibliographical references (leaves 53-54).