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‣ Axiomatic system design : chemical mechanical polishing machine case study

Melvin, Jason W. (Jason Webley)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 209 p.; 3067201 bytes; 3066867 bytes; application/pdf; application/pdf
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Axiomatic design is investigated as a design methodology for large or complex system design. Particular considerations of system design are described and the suitability of axiomatic design for such considerations is discussed. Then, tools to enable successful application of axiomatic design to systems are developed. The tools are expressed as theorems for axiomatic system design. The first theorem describes conditions for equivalence of FRs, and helps define the relationships within a design matrix. The second theorem describes a method of using only leaf levels to represent a system, and re-sequencing the design to achieve a decoupled matrix. Therefore, some types of coupling at high levels may be reduced or eliminated. The third theorem defines the decomposition strategy that is necessary to make axiomatic design compatible with object-oriented simulation models that are created starting with the high levels of the decomposition. The fourth and fifth theorems present a new method for considering and increasing system robustness to external noise factors during the conceptual design phase. While techniques for increasing robustness to external noise factors are known, integrating them into axiomatic design has not been shown previously. A case study of the design of a machine tool system for polishing silicon wafers using chemical mechanical polishing (CMP) is presented. The CMP system architecture is decomposed from top level requirements using the principles of axiomatic design...

‣ Suppression of intention tremor by mechanical loading

Dunfee, David Edward
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 118 leaves; 7037903 bytes; 7037661 bytes; application/pdf; application/pdf
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by David Edward Dunfee.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1979.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Bibliography: leaves 117-118.

‣ Generation and evaluation of mechanical assembly sequences using the liaison-sequence method

Lui, Man-Cheung Max
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: [1], 137 leaves; 8563723 bytes; 8563477 bytes; application/pdf; application/pdf
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by Man-Cheung Max Lui.; Includes bibliographical references.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1988.

‣ Optimizing the location of components in mechanical assemblies

Kim, Jay Jung
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 140 leaves; 7986867 bytes; 7986622 bytes; application/pdf; application/pdf
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by Jay Jung Kim.; Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1989.; Includes bibliographical references (leaves 133-140).

‣ An interactive software tool for editing and evaluating mechanical assembly sequences based on fixturing and orientation requirements

Abell, Thomas Edward
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 166 leaves; 15037964 bytes; 15037722 bytes; application/pdf; application/pdf
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by Thomas Edward Abell.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1989.; GRSN 410198; Title as it appears in the M.I.T. Graduate List, Sept. 1989: An interactive software tool for evaluating and editing mechanical assembly sequences based on fixturing and orientation requirements.; Includes bibliographical references (leaves 142-145).

‣ Mechanics, mechanisms, and modeling of the chemical mechanical polishing process

Lai, Jiun-Yu
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 308 leaves; 20085318 bytes; 20085079 bytes; application/pdf; application/pdf
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The ever-increasing demand for high-performance microelectronic devices has motivated the semiconductor industry to design and manufacture Ultra-Large-Scale Integrated (ULSI) circuits with smaller feature size, higher resolution, denser packing, and multi-layer interconnects. The ULSI technology places stringent demands on global planarity of the Interlevel Dielectric (ILD) layers. Compared with other planarization techniques, the Chemical Mechanical Polishing (CMP) process produces excellent local and global planarization at low cost. It is thus widely adopted for planarizing inter-level dielectric (silicon dioxide) layers. Moreover, CMP is a critical process for fabricating the Cu damascene patterns, low-k dielectrics, and shallow isolated trenches. The wide range of materials to be polished concurrently or sequentially, however, increases the complexity of CMP and necessitates an understanding of the process fundamentals for optimal process design. This thesis establishes a theoretical framework to relate the process parameters to the different wafer/pad contact modes to study the behavior of wafer-scale polishing. Several models of polishing - microcutting, brittle fracture, surface melting and burnishing - are reviewed. Blanket wafers coated with a wide range of materials are polished to verify the models. Plastic deformation is identified as the dominant mechanism of material removal in fine abrasive polishing.; (cont.) Additionally...

‣ Augmenting Datum Flow Chain method to support the top-down design process for mechanical assemblies; Augmenting DFC method to support the top-down design process for mechanical assemblies

Shukla, Gaurav, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 204 p.; 17144302 bytes; 17144061 bytes; application/pdf; application/pdf
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by Gaurav Shukla.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2001.; Includes bibliographical references (p. 181-187).

‣ Effects of in vivo degradation on mechanical behavior of a novel bioelastomer; Effects of in vivo degradation on mechanical behavior of PSG

Aronstam, Robert A. (Robert Andrew), 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 33 leaves; 1381552 bytes; 1381359 bytes; application/pdf; application/pdf
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by Robert A. Aronstam.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, June 2002.; Includes bibliographical references (leaves 32-33).

‣ Analysis of slurry flow in chemical-mechanical polishing

Kopanski, Krzysztof D
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 112 leaves; 5545745 bytes; 5552090 bytes; application/pdf; application/pdf
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Chemical-Mechanical Polishing (CMP) is one of the enabling processes used in the manufacture of semiconductor chips. In the relentless progress to make computer chips faster, smaller, and cheaper, the CMP process plays a prominent role. One of its limitations, however, is non-uniform polishing rate at the die and wafer scales. In this thesis, an innovative CMP machine configuration is proposed to minimize wafer-scale non-uniformity. The new face-up machine lowers wafer-scale non-uniformity by minimizing over-polishing of any particular area. The thesis discusses the kinematics and design considerations of this machine. Additionally, this thesis develops an analytical model for slurry flow in CMP in two steps. First, a simple but useful method of estimating the effective gap between the wafer and the pad during polishing is developed. The method uses pressurized fluid flow and an analytical model to estimate the effective gap between the wafer and the pad. Second, this effective gap is used in the Couette model that describes the slurry behavior in CMP. The Couette model shows that rotational speeds of the wafer and pad, the effective gap, and the sizes of the wafer and pad dictate the slurry flow rate and flow pattern in both conventional CMP and the new face-up CMP. The Couette model can be used to estimate the slurry flow rate whenever the process parameters are changed.; by Krzysztof D. Kopanski.; Thesis (S.M.)--Massachusetts Institute of Technology...

‣ Modeling of dielectric erosion and copper dishing in copper chemical-mechanical polishing

Noh, Kyungyoon
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 226 leaves; 11281374 bytes; 11295636 bytes; application/pdf; application/pdf
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The phenomenal success in the manufacture of multi-layer, Ultra-Large-Scale-Integrated (ULSI) semiconductor devices is in part due to the local and global planarization capabilities of the chemical-mechanical polishing (CMP) process. At present, copper is widely used as the interconnect material in the ULSI technology. The greatest challenge in Cu CMP now is the control of wafer surface non-uniformity-primarily due to dielectric erosion and copper dishing at various scales--to within the ever stringent industry specifications. In this thesis, an integrated non-uniformity model is developed by combining wafer-, die- and feature-scale non-uniformities. A feature-scale pressure calculation scheme based on surface step-height is adopted, and the evolution of the surface in each polishing stage is modeled in terms of geometric, material and process parameters. Various pad/wafer contact mechanics regimes have been considered to model oxide erosion and Cu dishing, from submicron device level to the global wiring level. The plausible causes of erosion and dishing at wafer-, die- and feature-scales were identified and integrated into the feature-scale step-height models. Such parameters include: initial pattern geometry, wafer-scale uniformity...

‣ Microstructure, residual stress, and mechanical properties of thin film materials for a microfabricated solid oxide fuel cell

Quinn, David John, Sc. D. Massachusetts Institute of Technology
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 184 p.
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The microstructure and residual stress of sputter-deposited films for use in microfabricated solid oxide fuel cells are presented. Much of the work focuses on the characterization of a candidate solid electrolyte: Yttria Stabilized Zirconia (YSZ). Stress and structure of reactive RF sputtered YSZ films are explored as a function of thickness (5nm - 1000nm), deposition pressure (5mtorr - 1OOmtorr), and substrate temperature (room temperature, 3000C and 6000C). Microstructure is characterized by x-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM). Film composition, specifically impurity content, is investigated with secondary ion mass spectroscopy (SIMS). Results indicate that YSZ films likely have a columnar structure with fully cubic crystalline phases of (100) texture with mixed amorphous/crystalline phases. Residual stress is measured via substrate curvature techniques. Results indicate that the as-deposited residual stress of YSZ ranges from -1.4 GPa to 400MPa with variations in sputtering conditions. Transitions from compressive to tensile stress are identified with variations in working pressure and film thickness.; (cont.) The origins and variations in as-deposited stress are determined to be from two primary mechanisms: tensile stress due to grain coalescence/growth and compressive stresses due to forward sputtering of target atoms (also known as "atomic peening" stresses). Due to the expected high-temperature operation (-1 0000C) of microfabricated solid oxide fuel cells...

‣ Chemical, mechanical, and thermal control of substrate-bound carbon nanotube growth

Hart, Anastasios John, 1979-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 357 p.
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Carbon nanotubes (CNTs) are long molecules having exceptional properties, including several times the strength of steel piano wire at one fourth the density, at least five times the thermal conductivity of pure copper, and high electrical conductivity and current-carrying capacity. This thesis presents methods of CNT synthesis by atmospheric-pressure thermal chemical vapor deposition (CVD), where effective choice of the catalyst composition and processing conditions enables growth of tangled single-wall CNTs or structures of aligned multi-wall CNTs, on bare silicon, microstructured silicon, and ceramic fibers. Applying mechanical pressure during growth controls the structure of a CNT film while causing significant defects in the CNTs. This mechanochemisty approach is used to "grow-mold" CNTs into 3D-shaped microforms. A new reactor apparatus featuring a resistively-heated suspended platform enables rapid ( 100 °C/s) temperature control and versatile in situ characterization, including laser measurement of CNT film growth kinetics, and imaging of stress-induced film cracking. By thermally pre-treating the reactant mixture before it reaches the substrate platform, aligned CNTs are grown to 3 mm length in just 15 minutes.; (cont.) A microchannel array is created for combinatorial flow studies of nanomaterials growth...

‣ Magnetic induction systems to harvest energy from mechanical vibrations

Jonnalagadda, Aparna S
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 108 p.
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This thesis documents the design process for magnetic induction systems to harvest energy from mechanical vibrations. Two styles of magnetic induction systems - magnet-through-coil and magnet-across-coils - were analyzed. MATLAB models were created to serve as a design aid and optimization tool for both styles of magnetic induction systems. Prototypes were built to test the predictions of the MATLAB models. The experimental data was found to be in good agreement with the model predictions.; by Aparna S. Jonnalagadda.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.; Includes bibliographical references.

‣ Cell-seeded type II collagen scaffolds for articular cartilage tissue engineering

Vickers, Scott M. (Scott Mitchell), 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 241 p.
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Defects in articular cartilage exhibit little spontaneous healing response, in part due to the limited number of chondrocytes available to infiltrate the defect and the absence of a provisional fibrin scaffold to accommodate cell migration into the lesion. One variable related to tissue engineering strategies employing cell-seeded scaffolds to treat such defects is the amount of cartilage formed in the construct prior to implantation. The objectives of this thesis were to evaluate effects of scaffold cross-link density and bioreactor culture environment on chondrogenesis in cell-seeded type II collagen scaffolds in vitro, and to begin to test effects of implant compositional maturity (viz. glycosaminoglycan, GAG, content) on chondral defect repair. Scaffold cross-link density, a determinant of cell-mediated scaffold contraction and degradation, affected chondrogenesis; scaffolds of low cross-link density that experienced contraction exhibited greater cartilaginous tissue formation compared to highly cross-linked scaffolds that resisted contraction. In addition to tissue-level effects on histogenesis, cross-link density was found to direct phenotypic differentiation at the cellular level. When employing marrow-derived stem cells as an alternative to chondrocytes...

‣ Inter-finger coordination in robot hands via mechanical implementation of principal components analysis

Brown, Christopher Yeates
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 89 p.
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Postural synergies describe characteristic patterns of actuation in human hands arising from biomechanical constraints, physical tendon coupling, and neurological control schemes. Often, a small number of synergies contain much of the information required to describe an entire human hand posture, with 80% or more of the total information encoded in only two component values. Synergies have commonly been used to identify hand shapes with minimal processing power. However, they can also be used to recreate postures in robot hands, by allowing a mechanical implementation of inter-finger coordination. This can provide benefits of reduced cost, compact size, and decreased actuator count. In this paper, a novel mechanism is proposed to drive a dexterous, versatile, 17 degree-of-freedom robot hand using only two DC motors. Posture data was collected with a dataglove, and analyzed using principal components analysis to determine the postural synergies. The synergies are then mechanically hardwired into the driving mechanism, resulting in a concept dubbed eigenpostures.; (cont.) Two eigenpostures effectively recreate the entire posture set. Several observations and suggestions are presented on tendon-drive robotic hand design in general, and also specifically targeted towards synergy- or eigenposture-based design. Avenues for further research into synergy mechanism design are proposed...

‣ Nano-scale scratching in chemical-mechanical polishing; Nano-scale scratching in CMP

Eusner, Thor
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 127 leaves
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During the chemical-mechanical polishing (CMP) process, a critical step in the manufacture of ultra-large-scale integrated (ULSI) semiconductor devices, undesirable nano-scale scratches are formed on the surfaces being polished. As the width of the interconnect Cu lines continues to shrink to below 60 nm, and as the traditional Si02 dielectric is replaced by the compliant, lowdielectric-constant materials, scratching has emerged as a challenging problem. This thesis presents a contact mechanics based approach for modeling nano-scale scratching by the hard abrasive particles in the slurry. Single-particle models that use elastic and plastic analyses to determine both the lower- and upper-bounds for the load per particle are introduced. These bounds are established for both homogenous and composite coatings. Multi-particle models are also presented. These models use contact mechanics at the pad-particle-coating interface to relate the global parameters of CMP, such as pressure, particle radius, slurry volume fraction and the material and geometrical properties of the pad and coating, to the widths and depths of scratches in the coatings. A lower- and upper-limit for the scratch width and depth in CMP is defined. Controlled indentation and scratching experiments have been conducted using a Hysitron TriboIndenter to validate the single-particle models. Based on these experiments...

‣ Transportation technology choice and fuel consumption in Egypt : an engineering-economic model

Weaver, Christopher Scott
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 2 v. (431 leaves)
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by Christopher Scott Weaver.; Thesis (M.S.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 1985.; MICROFICHE COPY AVAILABLE IN ARCHIVES AND ENGINEERING.; Bibliography: leaves 274-279.

‣ Design and implementation of nanoscale fiber mechanical testing apparatus

Brayanov, Jordan, 1981-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 27 leaves; 1623339 bytes; 1621919 bytes; application/pdf; application/pdf
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The rapid growth in the synthetic manufacturing industry demands higher resolution mechanical testing devices, capable of working with nanoscale fibers. A new device has been developed to perform single-axis tensile tests on fibers with diameter ranging from 50 nm to 10 [micro]m. The device is capable of performing simple extension tests to determine the fiber's strength as well as high-frequency dynamic tests to look at fiber recovery rates, dampening, and fatigue. The force resolution obtained using a quartz strain gauge and a Zeaman interferometer was in the order of 1 nN and the forces measured by the instrument ranged over 10 orders of magnitude. This paper will present the design the Nanofiber tester, which offered better performance than any currently available commercial instruments and will discuss the subtleties around the implementation of the instrument, which is yet to be completed.; by Jordan Brayanov.; Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.; Includes bibliographical references (leaf 26).

‣ Characterization of the mechanical properties of tactors used in tactile displays

Held, David (David A.)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 99 leaves
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Pancake motors used in a tactile display were analyzed to understand the characteristics of their operation, as well as to suggest improvements in the design of the display. The frequencies and forces produced by unencased and encased pancake motors were measured, and a motor model was formulated to simulate the motion of the motors. It was found that there was considerate variability between pancake motors, and it was proposed that this may be due to a varying damping coefficient. A viscoelastic substrate, named Skinsim, was selected based on mechanical tests to have similar material properties to skin. It was found that when the motors were mounted on Skinsim their frequency of vibration was reduced by 62%. Measurements of the effects of damping in Skinsim led to the recommendation that inter-tactor spacing on a tactile vest should be at least 60 mm if the display is to be used for precise tactor localization. Finally, a GPS device was integrated into the tactile display. This allows appropriate navigational commands to be sent to the user through the tactile vest, based on information about the user's location.; by David A. Held.; Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2007.; Includes bibliographical references (leaves 97-99).

‣ Model parameter estimation of atherosclerotic plaque mechanical properties : calculus-based and heuristic algorithms

Khalil, Ahmad S. (Ahmad Samir), 1980-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 176 p.; 6604798 bytes; 6628578 bytes; application/pdf; application/pdf
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A sufficient understanding of the pathology that leads to cardiovascular disease is currently deficient. Atherosclerosis is a complex disease that is believed to be initiated and promoted by linked biochemical and biomechanical pathways. This thesis focuses on studying plaque biomechanics because (i) there is a dearth of data on the mechanical behavior of soft arterial tissue yet (ii) it is the biomechanics that is able to provide invaluable insight into patient-specific disease evolution and plaque vulnerability. Arterial elasticity reconstruction is a venture that combines imaging, elastography, and computational modeling in an effort to build maps of an artery's material properties, ultimately to identify plaques exhibiting stress concentrations and to pinpoint rupture-prone locales. The inverse elasticity problem was explored extensively and two solution methods are demonstrated. The first is a version of the traditional linear perturbation Gauss-Newton method, which contingent on an appropriate regularization scheme, was able to reconstruct both homogeneous and inhomogeneous distributions including hard and spatially continuous inclusions. The second was an attempt to tackle the inherent and problem-specific limitations associated with such gradient-based searches. With a model reduction of the discrete elasticity parameters into lumped values...