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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.
281

Influence of hot rolling microstructure on mechanical properties of fullyannealed 5052 aluminum alloy

Hung, Liang-Jie 24 July 2012 (has links)
The objective of this work is to investigate the influence of hot rolling process on the mechanical properties of AA 5052 aluminum alloy. Hot-rolled band fabricated by tandem mill (hot-band A) will be compared with that fabricated by reverse mill hot-band C). Optical microscopic observations revealed that hot-band A has a uniform microstructure throughout the thickness, while hot-band C exhibits non-uniform microstructure, fine grains near the surface and coarser grains in the center. Both hot-bands were subjected to cold-rolling and annealing to O-temper. Two annealing processes were used: (a) annealing in 500oC salt bath, which may simulate the high heating rate of continuous annealing line (CAL), and (b) annealing in 320oC conventional air furnace with heating rate of 30oC/h, which may simulate the slow heating rate of batch-type annealing. In general, both materials annealed in 320oC air furnace exhibit higher yield strength than those annealed in 500oC salt bath do, however, both materials exhibit better tensile ductility after annealed in 500oC salt bath as compared with those annealed in 320oC air furnace.TEM examinations indicated that the cold-rolled sheet after annealing in 320oC air furnace contains larger number of precipitates comparing with its 500oC salt bath annealed counterpart. This observation may account for the higher yield strength of cold-rolled sheet annealed in 320oC air furnace. After cold-rolling and annealing in 320oC air furnace, the material C shows higher yield strength than the material A does. However, after annealing in 500oC salt bath, both materials have similar yield strength. XRD pole-figure analysis indicated that hot-band A exhibited stronger texture than hot-band C did. The texture intensity for both materials decreased considerably after cold-rolling and annealing. Orientation image mapping (OIM) obtained by EBSD (electron backscattered diffraction) analysis indicated that the grain boundaries in both materials after cold-rolling and annealing were mainly high angle boundaries, and the 500oC salt bath annealed specimens have more equiaxed grain shape as compared with the 320oC air furnace annealed specimens.
282

Investigation of Skin Tribology and Its Effects on Coefficient of Friction and Other Tactile Attributes Involving Polymer Applications

Darden, Matthew Aguirre 2010 December 1900 (has links)
Perception and sense of touch are extremely important factors in design, but until recently, the exploration of skin tribology related to tactility has been relatively untouched. In this emergence, skin-on-polymer interactions are becoming more widely investigated due to the prevalence of polymers in everyday life, and the ability to define these interactions in terms of tactility would be hugely beneficial to the engineering and design process. Previous work has investigated polymer textiles concerning tactility, examining environmental and material properties that affect skin on fabric coefficient of friction. In this study, similar friction procedure was used to compare coefficients of friction of a fingerpad across varying polymer fabrics. Forces were applied in both longitudinal and lateral directions, and it was discovered that force directionality greatly affects coefficient of friction. Specific causes have yet to be determined, but it is suspected that material weave and microscopic surface properties play a major role in this directional behavior. To complement these studies and relate them to tactility, trained human evaluators rated the samples against four tactile attributes: abrasiveness, slipperiness, sensible texture, and fuzziness. These ballots were then analyzed with Quantitative Data Analysis and shown to be repeatable among the participants, and each of the attributes were shown to be statistically independent of coefficient of friction. It should be noted, however, that fuzziness showed the greatest correlation coefficient of R^2=0.27. Material selection plays an integral role in frictional behavior, and researchers have been studying contact theory on both microscopic and macroscopic levels to determine how surface topography affects skin-polymer tribology. To negate material effects discussed in the Greenwood-Williamson contact model, frictional tests were performed on identical polypropylene plaques with textured grooves of varying dimensions. Both geometry and directionality proved to be major frictional contributors; as groove size increased, finger friction in the longitudinal direction decreased, but friction increased laterally. In addition to testing a fingerpad, friction was measured with a silicone wand to simulate a finger with different material properties. The silicone exhibited the opposite trend as skin; as groove width decreased, frictional forces increased longitudinally and decreased laterally. While topography affects frictional behavior, counterface stiffness, and intrinsic material properties may cause the trend shift between skin and silicone.
283

Fabrication of pyramid textures as anti-reflection layer on single crystal silicon solar cell

Wang, Jung-Shin 06 July 2007 (has links)
A simple and high efficient wet etching technique for fabricating pyramid textures on (100) Si wafer is proposed. Conventionally, pyramid textures were formed on Si wafers to reduce reflections using KOH anisotropic etching. Isopropyl Alcohol (IPA) is often added to the solution to abate the bubbling effect caused by hydrogen released form the Si surfaces during reaction. In this study, a metal net with proper opening dimension was used as a shelter to trap the hydrogen from leaving the surfaces of Si, and therefore turns the hydrogen gas into a gas-type etching mask during the anisotropic etching. In this way, pyramid textures with dimensions range from 3µm to 8µm were successfully fabricated. The measured average reflectivity of the texture for incident optical wave length from 400nm to 1000nm is less than 18%.
284

Microtexture and Mechanical Properties of Electron Beam or Tungsten Inert Gas Arc Welded Mg Alloys

Wu, Hsin-Hui 13 August 2003 (has links)
none
285

A study of micro fiber dispersion using digital image analysis

Hendrarsakti, Jooned 15 November 2004 (has links)
The area of the digital image processing is getting more attention in the hope that it will increase the accuracy of any scientific measurements, such as in determining an object velocity, temperature, and size. While human vision is excellent to recognize and differentiate objects, it has been proven to be a poor tool when it comes to measure the object performance. One of many digital image processing applications is texture analysis whose purpose is to evaluate image patterns. The purpose of this dissertation is to investigate the use of texture analysis as a tool to micro fiber dispersion measurement. Micro fiber dispersion can be found in many applications such as in paper and industry powder engineering. Three cases related to micro fiber dispersion were investigated in this study. The first case was the experimental study of the dispersion in open water channel. Sets of synthetic fibers were put into water channel to simulate a process that can be found in papermaking industry. The research investigated the effect of three operating parameters: fluid velocity, fiber consistency, and fiber aspect ratio to fiber dispersion. Using two-factorial experimental design technique, the main and interaction effects of these parameters were evaluated. The study found that increasing fluid velocity, fiber aspect ratio, and consistency decreased the dispersion level. The study also found that the effect of individual parameters is more pronounced than the role of the interactive terms on the fiber flocculation. The second case considered was applying the fiber dispersion analysis to computer-synthesized images consisting of different arrangements of fibers. Four sets of sub-cases were presented. These sub-cases were divided based on the fiber-concentrated location and fiber distribution. The use of computer-synthesized images was found to be very useful to simulate real situation during fiber dispersion. The third case investigated the fiber distribution on a dry paper. Images for different types of paper were taken and evaluated to see the dispersion level of each type of paper. It was found that the current texture analysis was applicable to determine the dispersion level for dry papers. While three cases indicated that the texture analysis can be used to investigate the fiber dispersion, the texture analysis used here is not a perfect and universal method and may not be suitable to analyze other types of dispersions. The human vision will always be essential to determine if the texture analysis is applicable to any other problem.
286

Characterization of aggregate resistance to degradation in stone matrix asphalt mixtures

Gatchalian, Dennis 12 April 2006 (has links)
Stone matrix asphalt (SMA) mixtures rely on stone-on-stone contacts among particles to resist applied forces and permanent deformation. Aggregates in SMA should resist degradation (fracture and abrasion) under high stresses at the contact points. This study utilizes conventional techniques as well as advanced imaging techniques to evaluate aggregate characteristics and their resistance to degradation. Aggregates from different sources and types with various shape characteristics were used in this study. The Micro-Deval test was used to measure aggregate resistance to abrasion. The aggregate imaging system (AIMS) was then used to examine the changes in aggregate characteristics caused by abrasion forces in the Micro-Deval. The resistance of aggregates to degradation in SMA was evaluated through the analysis of aggregate gradation before and after compaction using conventional mechanical sieve analysis and nondestructive X-ray computed tomography (CT). The findings of this study led to the development of an approach for the evaluation of aggregate resistance to degradation in SMA. This approach measures aggregate degradation in terms of abrasion, breakage, and loss of texture.
287

Translating Indian miniature paintings into a time-based medium

Vaidya, Aradhana 10 October 2008 (has links)
The purpose of this research and the corresponding project is to explore and interpret the qualities of the traditional art form of Indian miniature paintings into a digital, time based medium. These are beautiful, finely-drawn paintings with rich detailed patterns and striking bold colors. Intricately and meticulously drawn, they employ an alternative means of representation distinctly different from a conventional lens-based perspective. Most 3-dimensional digital media makes use of either a real or a virtual camera to inform the representation of space. In this project I deviate from this convention to create a new visual style for animation. The project demonstrates how a consistent yet different visual look can be achieved that retains the richness and visual expression of the traditional painting style through the use of new technology.
288

Camera-based Texture Mapping: An Approach for Creating Digital Environments with Foreground Forms Using 2d Paintings

Samman, Juwana Nicole 10 October 2008 (has links)
This thesis develops the method of using textures projected from the perspective of a projection camera, in combination with two-dimensional paintings and threedimensional models, to create digital environments. Past uses have demonstrated effectiveness only for background and midground scene elements with limited camera movement. This work explores how camera animation can be maximized using the projected texture technique onto foreground environment forms. Through several case studies, general guidelines for artists are developed for using camera-based projected textures.
289

Kinmen specific area land development permission consideration system to traditional settlement public space production result research consideration system , review on the traditional settlement public space development's influence

hsu, shih-ching 10 September 2008 (has links)
Therefore Kinmen because of the Kuomintang and Communist Parties war, for a long time battlefield government affairs related prohibition rule and military control influence. After on November 1, 1992 relieved the battlefield government affairs military control, for the effective management land resource's development, in January 20, 1996 announced that implemented the Kinmen specific area plan. But shape extension from the Minnan tradition construction pattern and the culture, has the regional color extremely the traditional settlement, after facing the so significant policy the change, in the settlement has many big heavy changes inevitably. This research is on the Kinmen specific area land development permission consideration system (Kinmen County natural village development permit consideration standard), review on the traditional settlement public space development's influence, divides into the system and the actual case observation and so on two general orientations, spirit and the goal the elaboration development permit consideration system, the execution way and the result is the key point; The actual case extension of by the traditional settlement public space texture, newly supposes the construction to use the open area for the public to use directions and so on inventory survey primarily. By present situation material's collection reorganization,, preceding the public spatial production result the appraisal, Seeks for the settlement public space the significance and the value is., seeks for in the system the feasible adjustment. The public space's production is the Kinmen specific area land development permission consideration system important goal. This research already regarding development plan's important item and the topographic diagram, inspected one by one by the observation approach the development base has constructed in the use, the collection reorganization public uses the open area present situation material. After collecting entire data and set of cartography discovery, this policy and is inferior to the public spatial production's result to anticipate obviously. May discover the consideration system lacks the superior plan to instruct, the examination resolution carries out the mechanism deficient, with the place environment project deficient conformity contact surface, to use the open area deficient for the public to be too scattered, and the development consideration process lacks questions and so on public participation to wait for overcoming with adjusts. In addition, this research to Kinmen area tradition settlement under development licensing system, for adaptation modern life state, regarding public spatial texture development and vicissitude, by examination licensing system moderate adjustment, but promotes the public spatial production to carry out the proportion effectively, improves in the natural village the living conditions quality.
290

Microstructure and Properties of AZ31 Magnesium Alloy Processed by Equal Channel Angular Extrusion.

Ding, Shi-xuan 17 September 2008 (has links)
none

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