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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

A within-subject comparison of mandibular long-bar and hybrid implant-supported prostheses

Tang, Ling, January 1988 (has links)
Thesis (Ph. D.)--Université de Montréal, 1999. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references.
2

A within-subject comparison of mandibular long-bar and hybrid implant-supported prostheses

Tang, Ling, January 1988 (has links)
Thesis (Ph. D.)--Université de Montréal, 1999. / Includes bibliographical references.
3

Efficient Parallel Algorithm for Overlaying Surface Meshes

Jain, Ankita 17 May 2007 (has links)
Many computational applications involve multiple physical components, each having its own computational domain discretized by a mesh. An integrated simulation of these physical systems require transferring data across these boundaries, which are typically represented by surface meshes composed of triangles or quadrilaterals and are non-matching with differing connectivities and geometry. It is necessary to constructa common refinement (or common tessellation) of the surface meshes to transfer data between different domains accurately and conservatively. For large-scale problems that involve moving boundary, the common tessellation must be updated frequently within the integrated simulations running on parallel computers. Previously, Jiao and Heath developed an algorithm for constructing a common tessellation by overlaying the surface meshes. The original algorithm is efficient and robust, but unfortunately, it is complex and difficult to parallelize. In this thesis, we develop a modified algorithm for overlaying surface meshes. Our algorithm employs a high-level primitive, face-intersection, which combines the low-level point-projection and edge-intersection primitives of the original algorithm. A main advantage of our modified algorithm is its ease of implementation and parallelization. Our implementation utilizes flexible data structures for efficient computation and query of the common tessellation and avoids potential redundancy in computations to achieve high efficiency. To achieve robustness, we pay special attention to avoid potential topological inconsistencies due to numerical errors, and introduce a preprocessing step to project a far-apart surface mesh onto other before computing the common tessellation. We present numerical examples to demonstrate the robustness and efficiency of our method on parallel computers.
4

Materials selection for concrete overlays

Kim, Dong-Hyun, 1984- 29 September 2011 (has links)
Concrete overlays have been a rehabilitation method for many years. It has been extensively utilized and studied in other states, but Texas is still at an initial stage of fully implementing the method. The large volume of concrete highways in Texas makes bonded concrete overlays, unbonded concrete overlays, and whitetoppings very viable options. However, there is a lack of educational guidelines for pavement engineers for concrete overlay construction. This research presents the information gathered from literature review, condition survey, and evaluation of existing concrete overlays in Texas. Also, a laboratory research was performed for recommendations for materials selection and construction for concrete overlays. From these, guidelines for materials selection and construction method developed that will assist in future concrete overlays in Texas are presented. / text
5

A three dimensional photoelastic stress analysis of the distribution and magnitude of forces transmitted by the overdenture

Davis, William Jarman. January 1977 (has links)
Thesis (M.S.)--University of Michigan, Ann Arbor, 1977. / Typescript (photocopy). Includes bibliographical references (leaves 105-112). Also issued in print.
6

A three dimensional photoelastic stress analysis of the distribution and magnitude of forces transmitted by the overdenture

Davis, William Jarman. January 1977 (has links)
Thesis (M.S.)--University of Michigan, Ann Arbor, 1977. / Typescript (photocopy). eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 105-112).
7

Topologically-aware Construction of Unstructured Overlays over Ad Hoc Networks/Construction topologiquement avertie d'overlays sans structure sur des réseaux ad hocs

Calomme, Sandrine 12 January 2009 (has links)
The number of electronic devices, equipped with a wireless interface has exploded over the last decades. Unfortunately, their usage is often restricted to the connection to a wired infrastructure, even for local communications. That is quite surprising as the research area of infrastructureless, or ad hoc, networks has flourished for years. The literature on ad hoc networks is very rich, but their usage almost inexistent. Potential users have plenty of solutions at hand, but do not exploit them. Even if ad hoc networks allow us to get rid of the infrastructure, they still require an implicit agreement on the solution to use. Nevertheless, it is very dicult to pick in the rich panel of protocols the best one, that would fit any ad hoc user in any ad hoc network. As an example, it has been demonstrated, for the routing, that each protocol has definite advantages and disadvantages, in every different scenario, and is well suited for certain situations. Yet, a salient feature of ad hoc networks is precisely that the panel of situations is very large. The ad hoc network conditions are influenced by the number of ad hoc users, their relative positions, their capabilities, their mobility pattern, the applications they use, the traffic load and type, and so forth. Moreover, the users may themselves be heterogeneous, with different hardware and software capabilities, mobile behaviour and communication needs. Hence, there is a particular need in ad hoc networking for flexible techniques. We contribute to this problem by studying the feasibility of overlay routing and giving some hints in that direction. We explain how the overlay members can avoid the expensive process of building an overlay topology, before using their customised routing application. The rationale exploits the broadcast nature of ad hoc networks, and is qualified as a Reactive Overlay Approach. We also detail an elementary reactive overlay routing application and test it, by simulations, in a variety of conditions, including the network and overlay densities. This performance study shows the feasibility and the efficiency of overlay routing applications developed according to the Reactive Overlay Approach. It also evidences the impact of using an appropriate value for the neighbourhood range, defined as the maximum number of hops between two overlay neighbours. Hence, we detail the critical neighbourhood range (CNR) problem, which, in short, consists in determining the minimum neighbourhood range value that generates a connected overlay. We solve it in the asymptotic case, i.e. when the number of nodes in the underlay or the size of the field tends to infinity. The mathematical results are interesting in the sense that they can be useful for a better understanding of the interaction between various typical characteristics of a connected overlay topology on an ad hoc network. However, the theoretical, asymptotic, CNR is not adequate in practice. We thus also explore heuristics for estimating the CNR. We present a simple protocol which estimates an appropriate neighbourhood range for overlay routing applications. For the purpose of its evaluation, we define general performance criteria based on overlay flooding. Namely, these are the delivery percentage, bandwidth consumption and time duration of flooding on the overlay. The main drawback of the Reactive Overlay Approach is the amount of bandwidth consumed during the flooding of overlay route requests. Hence, we also consider the Proactive Overlay Approach, which consists in building the overlay topology before the emission of any overlay broadcast message, and maintaining it. We compare the quality of various overlay topologies in the static case. We finally describe and evaluate the Overlay Topology Control (OTC) protocol, that maintains, in a mobile context, the overlay topology as close as possible to the overlay topology evaluated as the best. The main objection that would arise against overlay routing on ad hoc networks is that the ad hoc nodes do generally own poor resources and that overlay routing consumes them even more than native routing. The feasibility study we conducted with the reactive approach and the evaluation of OTC, designed in the context of the proactive overlay approach, confirm that the consumption of resources must be handled carefully. Nevertheless, they show that this problem is not insurmountable.
8

Dual field nano precision overlay

Yin, Bailey Anderson 03 January 2011 (has links)
Currently, the imprint lithography steppers are designed to only pattern one field of 26 x 33 mm at a time. This choice is based on the desire to mix-and-match to the standard optical lithography tools whose field size is also 26 x 33 mm. Throughput can be increased if more than one field can be imprinted simultaneously. The problem with adding a field to the imprinting template is that each field has overlay errors associated with it that are created when the template is manufactured and when the corresponding prior field is manufactured on the wafer. The current process is able to correct these template and wafer overlay errors using a precision stage and actuators that elastically deform the template. The same method cannot be used when there are two fields because the fields are not independent and interact with each other. Correcting the errors in one of the fields tend to increase the error in the second field. vii In this thesis, a new control method has been created to account for the dependent motion. A new template concept was also created to try to limit the interaction between the two fields. The new control algorithm was tested in simulation to see if it could correct the current 1-field setup as well as the new concept of having more than one field on a template. The control algorithm was also used to test applications where the overlay errors in only one direction need to be corrected. The control algorithm was tested on a solid single field template, the baseline case, and was able to achieve 1.3 nm overlay, which is consistent with the current method. The algorithm was then tested on the dual field concepts. The range of alignment errors needed to get 5 nm overlay are too tight for current manufacturing but the compliant concept did have more relaxed ranges than the solid dual field template. With more research, the compliant template concept might be changed to allow for wider ranges. The tests with correction in only one direction had promising data that should be investigated further. / text
9

Effects of Surface Treatments on National Bridge Inventory Condition Ratings for Concrete Bridge Decks in Utah

De Leon, John Taani 01 April 2018 (has links)
Although the application of surface treatments on bridge decks is expected to positively impact bridge deck condition, the effectiveness of specific surface treatments on extending bridge deck life has not yet been quantified on Utah bridge decks. Therefore, the objectives of this research were to develop and analyze deterioration curves for bare concrete bridge decks and decks with specific treatments commonly used in Utah. The scope of this study was determined by the types and extent of electronically available data, including selected static inventory information; maintenance, rehabilitation, and reconstruction histories; and National Bridge Inventory (NBI) condition ratings for the bridge decks. Bridge deck selection criteria and analysis procedures were developed to enable evaluation of the effects of surface treatments on bridge decks in Utah. Characteristics of a typical bridge were defined, and a list of typical bridges was produced to minimize potentially confounding effects of atypical bridge characteristics in comparisons of deterioration curves for monolithic concrete decks, decks with a bituminous overlay, decks with an epoxy overlay, and decks with a latex-modified concrete overlay. Climatic differences were taken into account by grouping bridges not only by overlay type, but also by Utah Department of Transportation region, which was used in this research as a general surrogate for latitude. Individual bridge deck deterioration curves were then combined to generate average deterioration curves aligned by deck construction time and average deterioration curves aligned by deck treatment time. To at least partially account for the potentially different effects of different treatment times, the bridge groups involving overlays were divided into two treatment time categories, early and late, for analysis. The average deterioration curves aligned by deck construction time suggest that certain treatments applied at certain times can achieve average NBI ratings greater than those for monolithic concrete during selected years of bridge deck life. The average deterioration curves aligned by deck treatment time suggest that certain treatments applied at certain times can achieve improvements in NBI ratings that correspond to apparent increases in bridge deck service life. Primarily because the NBI rating system is based mainly on visual inspection, the full benefits of early applications of surface treatments are not apparent in the results of this research. Supplemental perspectives may be gained about the performance of specific surface treatments by evaluating bridge deck deterioration in terms of delamination, half-cell potential, and chloride concentration, for example, which are direct measures of the deterioration process typically experienced by concrete bridge decks in Utah.
10

Overlay welding of FeCrAl alloys / Påsvetsning av FeCrAl legeringar

Rashid, Lezan January 2016 (has links)
In this master thesis different overlay welding methods suitable for boiler application has been investigated. The purpose of this project is to define advantages and disadvantages for each overlay welding methods and suggest some evaluation criteria on some commercial and experimental alloys aimed for overlay welding material. Many components in a boiler are made of low alloy steel and the atmosphere in the furnace region can be very complex; therefore many different types of corrosion can occur. Weld overlay is a process where one or multiple layers of corrosion resistant material are applied to a base material. The two overlay welding methods investigated in this study were Tungsten Inert Gas welding and Metal Inert/Active Gas welding. Tests were performed with FeCrAl alloys (Kanthal A, Kanthal D and some experimental alloys). FeCrAl alloys in general are ferritic iron-based steels with a typical concentration of 20-23 wt. % chromium and ~5 wt.% aluminum. Different overlay welding evaluation was made; visual examination, dye penetrant inspection, macro/micro examination, side bend test and short term corrosion test (~50hours). Conclusion of this thesis is that MIG welding is a more productive method than TIG, but more defects such cracks and lack of fusion can be produced for MIG welding. These defects can be “fixed” if welding parameters is optimized. If repairing a certain place TIG welding is a better option. A conclusion about number of layers; one layer with MIG welding is almost as thick as three layers with TIG welding with welding wire Ø 1mm. Three welding evaluation that is really important is visual examination, dye penetrant testing and corrosion test in order to choose which overlay welding method is suitable in boiler application. / I detta examensarbete har olika påsvetsningsmetoder som är lämpliga för en pannapplikation undersökts. Syftet med denna studie var att undersöka både för- och nackdelar med påsvetsningsmetoderna och föreslå några utvärderingskriterier på vissa kommersiella och experimentella legeringar som lämpar sig för påsvetsningsmaterial. Många komponenter i en panna är tillverkade av låg legerat stål och miljön där förbränningen sker kan vara väldigt komplex, därför kan det ske korrosion. Påsvetsning är en process där ett eller flera skikt av ett mer korrosionsbeständigt material appliceras på ett basmaterial. De två olika svetsmetoderna som undersöktes i denna studie var TIG-svetsning och MIG-svetsning. Testerna utfördes med FeCrAl legeringar (Kanthal A, Kanthal D och vissa experimentella legeringar). FeCrAl legeringar är i allmänhet ferritiska järnbaserade stål med 20-23% krom och ~5% aluminium. De utvärderingsmetoderna som undersöktes var: visuell undersökning, penetrantprovning, makro/ mikroundersökning, sidobockprovning och korttidskorrosionstest (~50 timmar). Slutsatsen av detta examensarbete är att MIG-svetsning är en mer produktiv metod än TIG, men fler defekter såsom bindfel och sprickor uppkom för MIG-svetsning. Dessa defekter kan ”fixas” genom optimering av svetsparametrar. Om man bara ska reparera ett specifikt område är TIG-svetsning ett bättre alternativ. En slutsats om antal lager är att ett lager med MIG-svetsning är nästan lika tjockt som tre lager med TIG-svetsning med Ø 1mm svetstråd. Tre svetsutvärderingar som är viktiga är visuell undersökning, penetrantprovning och korrosionstest för att välja vilken påsvetsmetod som är lämpligast i pannapplikation.

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