Página 5 dos resultados de 2573 itens digitais encontrados em 0.148 segundos

‣ Nucleation and growth of a single martensitic particle

Haezebrouck, Dennis Michael
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 251 leaves; 18569905 bytes; 18569665 bytes; application/pdf; application/pdf
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by Dennis Michael Haezebrouck.; Thesis (Sc. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1987.; Vita.; Bibliography: leaves 243-250.

‣ Damage development and failure of fiber-reinforced ceramic matrix composites

Dannemann, Kathryn Ann
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 268 leaves; 22044396 bytes; 22044153 bytes; application/pdf; application/pdf
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by Kathryn Ann Dannemann.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1989.; Vita.; Includes bibliographical references (leaves 111-120).

‣ Transmission and routing of optical signals in on-chip waveguides for silicon microphotonics

Lee, Kevin Kidoo, 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 142 p.; 8607232 bytes; 8606992 bytes; application/pdf; application/pdf
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by Kevin Kidoo Lee.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2001.; Includes bibliographical references (p. 139-142).

‣ Synthesis and characterization of ring-opening metathesis polymers with pendant carborane groups

Man, Alice (Alice Mei-Ling), 1972-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 191 leaves; 10330493 bytes; 10354751 bytes; application/pdf; application/pdf
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by Alice Man.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1999.; Includes bibliographical references (leaves 180-191).

‣ Design, synthesis and characterization of side chain liquid crystal segmented polyurethanes

Nair, Bindu R., 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 146 leaves; 12011567 bytes; 12011323 bytes; application/pdf; application/pdf
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by Bindu R. Nair.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000.; Includes bibliographical references.

‣ Alloy design or three-dimensional printing of hardenable tool materials

Guo, Honglin, 1965-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 174 leaves; 8524668 bytes; 8524474 bytes; application/pdf; application/pdf
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Three-dimensional printing (3DP) is a state-of-the-art manufacturing technology, One of its many important applications is to fabricate the metal tooling for plastic injection molding. In order to achieve a fully dense 3DP metal tool, the current 3DP process involves five steps: printing, debinding, sintering, liquid metal infiltration and heat treatment. Due to the infiltration requirement, all 3DP tools made to date are composed of a high-strength skeleton material and a low-strength infiltrant. The search for a hardenable/hard 3DP system is the mission of this dissertation. Five major accomplishments can be found in the dissertation: (1) development of the 420/bronze material system for 3DP tooling; (2) development and optimization of the post-processing of the system; (3) development of a computer model simulating the interaction of powder/liquid infiltrant; (4) computer-aided material system design and (5) methodology exploration of the material system development.The 420/bronze material system with a minimum reaction was developed experimentally, by screening 30 potential material systems. Compared to the initial 3DP and reactive system, the system strength was significantly improved. More than 50 3DP injection tools have been fabricated using this material system. A 3DP tool made of the 420/bronze system has been used to mold more than one hundred thousand plastic products without major repairing of the tool. It was the first time that an injection mold was made of 60 vol% 420 and 40 vol% bronze. The system was a milestone in the 3DP material system development. In addition...

‣ Quantifying the economic potential of a biomass to olefin technology

Chiang, Nicholas (Nicholas Kuang Hua)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 40 leaves; 1722349 bytes; 1723916 bytes; application/pdf; application/pdf
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Oil is one of the most valuable natural resources in the world. Any technology that could possibly be used to conserve oil is worth studying. Biomass waste to olefin (WTO) technology replaces the use of oil as a feedstock. WTO technology is actually a combination of two different processes: the waste to methanol (WTM) process and the methanol to olefins (MTO) process. However, WTO technology is still not commercially applied. Despite the environmentally beneficial advantages of biomass waste to olefins technology, the economic advantages or disadvantages still need to be explored further. This thesis tries to determine under what operating conditions (production volumes, feedstock prices, etc.) make the biomass waste to olefins technology most competitive. The WTM process is the economical limiting factor in the WTO technology. However, for relatively significant production volumes, the WTO technology is still competitive with a slight decrease in biomass feedstock price.; by Nicholas Chiang.; Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, September 2005.; Includes bibliographical references (leaves 39-40).

‣ Commercial assessment of roll to roll manufacturing of electronic displays

Randolph, Michael Aaron
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 81 leaves
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The cost of manufacturing electronic displays currently limits the range of applications and markets into which it is currently economically feasible to adopt displays. Roll-to-roll manufacturing has been identified by the display industry as a new and fundamentally different manufacturing paradigm that has the potential to significantly reduce the manufacturing cost of a display relative to the conventional approaches used in the industry. This manufacturing cost reduction could have a profound impact on the display industry by not only transforming the display manufacturing infrastructure, but also by permitting electronic displays to penetrate new markets. The purpose of this thesis is to determine how roll-to-roll manufacturing technology could develop and to assess what impact the technology could have on the electronic display manufacturing industry. This work first identifies the material, patterning, and equipment technologies that need to come together in order for roll-to-roll manufacturing to be industrially feasible, and then determines how and if the technology will offer a cost reduction over conventional manufacturing techniques.; (cont.) Next, the markets for displays are segmented and analyzed to discern whether niche initial markets exist where roll-to-roll could have a distinctive advantage and gain traction. Competitive technologies such as LCD and modular LED are discussed and it is determined that roll-to-roll displays must compete with LCD technology on the basis of price in the markets in which LCD has incumbency in order to achieve widespread adoption. The display industry structure is analyzed by means of an assessment of the supply chain...

‣ Process and design techniques for low loss integrated silicon photonics

Sparacin, Daniel Knight
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 260 p.
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Microprocessors have truly revolutionized the efficiency of the world due to the high-volume and low-cost of complimentary metal oxide semiconductor (CMOS) process technology. However, the traditional scaling methods by which chips improve are soon to end. The continued drive towards smaller circuit elements and dense chip architecture has yielded to power consumption, heat production, and electromagnetic interference (RC-delay) limitations. A logical solution to surmounting this electronic interconnect bottleneck is to utilize photonic interconnects. Photonic interconnects (waveguides) offer high data bandwidths with low signal attenuation and virtually zero heat dissipation. Strategic replacement of RC speed-limited electronic interconnects with photonic interconnects is a logical step to improving data processing performance in future microprocessors. Integration of photonic circuits onto electronic chips also enables sought after networking technologies that have higher complexity and unique functionality. Similar to the integrated microchip, the employment of CMOS technology in the fabrication of integrated photonic chips enables high yield, low cost, and increased performance. Essentially, the development of an integrated CMOS compatible photonic circuit technology is an enabler of improved communication.; (cont.) However...

‣ Shape morphing structures via intercalation compounds

Wong, John T., M. Eng. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 40 leaves
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Recent research has allowed the use of electrode-active materials as actuators by harnessing reversible volumetric change due to intercalation during charging and discharging. These actuators provide a relatively large strain, 2-3%, while requiring less than ten volts to operate with a cycle time on the order of one hundred seconds. This technology can be used in any moderate bandwidth, high-force, high-strain application, including shape-morphing helicopter blades, boat hulls, satellites, and any other structure that benefits from shape change. An analysis is performed on the state of the technology, the intellectual property held, and the potential markets that exist. A recommendation is made to pursue the technology, while cognizant of the fact that it is still in a seed stage and requires significant time and financial investment before entering production. Two business models are proposed and rough market calculations are also presented. The basis of this project is work done at the Massachusetts Institute of Technology by Professor Yet-Ming Chiang and Professor Steven Hall. Industrialists, including but not limited to, William Fallon and Dan Ursenbach of Sikorsky Aircraft in Stratford, Connecticut are also involved in the project.; by John T. Wong.; Thesis (M. Eng.)--Massachusetts Institute of Technology...

‣ Mechanical property characterization and enhancement of rigid rod polymer fibers

Fahey, Maureen Theresa
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 51 leaves
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by Maureen Theresa Fahey.; Thesis (B.S.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 1990.; Includes bibliographical references (leaf 51).

‣ Novel patterning techniques for manufacturing organic and nanostructured electronics

Chen, Jianglong, 1976-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 206 p.
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Molecular organic semiconductors and nanometer size particles are two new classes of functional materials allowing fabrication of electronic devices on low-cost and large area substrates. Patterning these electronic materials requires the development of unconventional techniques, and the scientific understanding behind the manufacture processes. We introduce the first-generation Molecular Jet (MoJet) printing technique for vacuum deposition of evaporated thin films and apply it to the fabrication of high-resolution pixelated (800 ppi) molecular organic light emitting devices (OLEDs) based on aluminum tris(8-hydroxyquinoline) (Alq3), and the fabrication of pentacene based organic field effect transistors (OFETs) with narrow channel (15 gm) and asymmetric silver/gold contacts. Patterned printing of both organic and metal films is demonstrated, with the operating properties of MoJet-printed OLEDs and OFETs shown to be comparable with the performance of devices fabricated by conventional evaporative deposition through a metal stencil. This MoJet printing technique is reconfigurable for digital fabrication of arbitrary patterns with multiple material sets and a high print accuracy of better than 5gtm, and scalable to large area substrates.; (cont.) Analogous to the concept of "drop-on-demand" in Inkjet printing technology...

‣ Commercial potential for thermal & magnetic sensitive polymer in drug delivery applications; Commercial potential for thermal and magnetic sensitive polymer in drug delivery applications

Edward, Jonathan M. (Jonathan Mark)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 80 leaves
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Thermal and magnetically sensitive polymers are a new class of materials with unique properties suitable for applications in drug delivery. Specifically, these polymers can be combined with a drug reservoir to make a drug delivery device that can be triggered externally. Such a device could be implanted subcutaneously and allow for temporal control of drug release and localized delivery. Current experiments have shown that a prototype device is capable of delivering both small and large molecule drugs. Attractive medical applications for this technology were discovered and their respective markets examined. Additionally, the scientific literature and intellectual property in this field were analyzed for competing technologies that would hinder development of this invention. Novel attributes of this technology were also identified and specific competitive advantages made evident. To facilitate the commercialization of this novel technology, a business model has been proposed that identifies possible risks and provides strategies for overcoming them. Using this model, a timeline for future research and development has been constructed that traces the technology from its current state to a final product that can be launched commercially. The requirements for regulatory approval have also been investigated and a plausible manufacturing process has been established. Furthermore...

‣ Electrothermal controlled-exposure technology

Maloney, John Mapes
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 79 p.
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A technology is presented for exposing the contents of microfabricated cavities in a substrate. These contents are hermetically sealed until exposure is triggered by an electronic signal. The exposure mechanism uses electrothermal heating to rupture a metal membrane at one end of the cavity. The device's capability for storing a variety of contents and exposing them on demand makes it well suited for periodic exposure of new sensors as old ones degrade. Two commercialization possibilities are investigated: biowarfare agent detection and in vivo glucose sensing. Both applications employ sensing mechanisms that can be miniaturized and packaged in an array. These sensors are susceptible to fouling or degradation over time from environmental factors. The controlled-exposure technology addresses this problem by periodically exposing fresh sensors. The two applications are thought to be especially favorable markets because of the need for reliable, continuous sensing. The engineering aspects of the technology are investigated by identifying key material properties for each component of the device.; (cont.) The key properties for the substrate material are suggested to be its vapor permeability and suitability for cavity formation. The most important properties of the membrane are its electrical requirements (the current and voltage required to expose or "activate" the device)...

‣ Novel thermoelectric materials development, existing and potential applications, and commercialization routes

Bertreau, Philippe
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 86 leaves
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Thermoelectrics (TE) are devices which can convert heat in the form of a temperature gradient into electricity, or alternatively generate and absorb heat when an electrical current is run through them. It was established in the 1950's that the effectiveness of a thermoelectric could approximately be described in terms of a dimensionless figure of merit ... being respectively the Seebeck coefficient, the electrical resistivity and the thermal conductivity of the material. Until recently, ZT1 was the best performance these materials could achieve. However, the field of thermoelectrics advanced rapidly in the five last years, leading to the first significant breakthroughs in this area in the past fifty years, with materials with ZT up to 3 being reported. It is therefore interesting to wonder what new applications and markets these improvements at the material level could lead to. The first section of this thesis is a review of the principles of TE technology, the current materials and their level of performance. The recent materials developments are also described.; (cont.) The commercialization of TE is then discussed, along with the requirements in terms of performance and costs which would have to be achieved to make TE a further commercial success. Eventually...

‣ Magneto-mechanical properties and applications of Ni-Mn-Ga ferromagnetic shape memory alloy

Murray, Steven J. (Steven James), 1974-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 182 p.; 10548393 bytes; 10548149 bytes; application/pdf; application/pdf
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by Steven J. Murray.; Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2000.; Vita.; Includes bibliographical references (p. 151-155).

‣ Environmentally benign manufacturing of three dimensional integrated circuits; Manufacturing of three dimensional integrated circuits

Somani, Ajay
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 268 p.
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Along with scaling down in size, novel materials have been introduced into the semiconductor industry to enable continued improvements in performance and cost as predicted by Moore's law. It has become important now more than ever to include an environmental impact evaluation of future technologies, before they are introduced into manufacturing, in order to identify potentially environmentally harmful materials or processes and understand their implications, costs, and mitigation requirements. In this thesis, we introduce a methodology to compare alternative options on the environmental axis, along with the cost and performance axes, in order to create environmentally aware and benign technologies. This methodology also helps to identify potential performance and cost issues in novel technologies by taking a transparent and bottoms-up assessment approach. This methodology is applied to the evaluation of the MIT 3D IC technology in comparison to a standard CMOS 2D IC approach. Both options are compared on all three axes - performance, cost and environmental impact.; (cont.) The "handle wafer" unit process in the existing 3D IC technology, which is a crucial process for back-to-face integration, is found to have a large environmental impact because of its use of thick metal sacrificial layers and high energy consumption. We explore three different handle wafer options...

‣ Fabrication and characterization of Ni-Mn-Ga ferromagnetic shape-memory alloy composites

Ivester, Robin H. C. (Robin Hansell Corbin), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 48 leaves; 3257018 bytes; 3256778 bytes; application/pdf; application/pdf
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by Robin H.C. Ivester.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2002.; Includes bibliographical references (leaves 46-48).

‣ Multilayer composite photonic bandgap fibers; Composite photonic bandgap fiber materials and fabrication

Hart, Shandon D. (Shandon Dee), 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 126 leaves; 6020400 bytes; 6018127 bytes; application/pdf; application/pdf
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Materials and fabrication techniques are developed that lead to the successful fabrication of multilayer composite photonic bandgap fibers. The pertinent background in electromagnetic theory of multilayer dielectric mirrors and optical fibers is surveyed. Materials properties constraints are outlined, with emphasis on those constraints related to processing strategy and ultimate target length scale. Interfacial energy is measured in a chalcogenide glass / organic polymer composite system selected for fiber fabrication. A classical capillary instability model is employed to predict the feasibility of fiber fabrication based on material properties; from this model, quantitative materials selection criteria related to ultimate length scale are derived. Good agreement is found between the calculated materials selection criteria and controlled fiber experiments. The fiber fabrication techniques are described and analyzed; chalcogenide film deposition is characterized using Raman and electron microprobe spectroscopy, and heat transfer during fiber drawing is modeled using a commercial finite-element software package. The developed materials and fabrication processes are used to perform two case studies in novel photonic bandgap fiber fabrication; the first case study deals with externally reflecting omnidirectional 'mirror-fibers'...

‣ Integration of III-V optical devices and interconnects on Si using SiGe virtual substrates

Yang, Vicky Kung-Fan, 1975-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 160 p.; 14074873 bytes; 14074623 bytes; application/pdf; application/pdf
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Because of the limitations to the functionality that Si can provide, integration of light emitting materials such as GaAs and other III-V materials provides the promise for the combination of electrical and optical devices onto a Si platform. Monolithic integration, compare to hybrid integration, is the more cost effective and reliable way to combine these dissimilar materials. However, materials compatibility issues such as lattice mismatch, polar-on-non-polar epitaxy, and thermal mismatch make the direct growth of high quality GaAs-based material on Si difficult. However, with the use of SiGe virtual substrates, Si substrates that have the Ge lattice constant, this goal can be achieved since Ge and GaAs have a small lattice mismatch of only 0.07%. High quality GaAs on Si having a threading dislocation density lower than 3x 106 cm'2 on offcut SiGe virtual substrates has been demonstrated. While utilizing SiGe virtual substrate technology to enable high quality GaAs on Si, we have studied the crack formation in GaAs layers on SiGe resulting from the thermal mismatch between the film and the substrate. GaAs has a thermal expansion coefficient of 5.8x10-6 /ʻC while the value for Si and the SiGe substrate is 2.6x10-6 /C. The thermal expansion coefficient of the SiGe virtual substrate is mainly dictated by the underlying Si substrate. As a result of the thermal mismatch...