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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.
11

Statistical analysis of deterministic textures in steel sheet production

Porrino, Alessandre January 2004 (has links)
Textured surfaces are universally adopted in the steel sheet production industry, and manufacturers are continuously improving the quality of the finished products through intense research in the surface characterisation field. Deterministic Surfaces are textured with specifically designed rolls in order to present a certain degree of regularity, which allows better control over the functional behaviour of the metal sheets. The regularity of the texture impressed on the steel sheets also allows unconventional approaches to surface characterisation and to the assessment of the texture's structure. Statistical analysis is the most effective way to target the isolation of the deterministic part of the surface, which represents the desired product, from the stochastic part, called ‘noise’ and associated with the inaccuracies of production and measurement. This work addresses the problem of characterisation of deterministic textures through statistical analysis, proposing innovative filtering techniques aimed at the realisation of an On-line Process Control System. Firstly the techniques proposed are theoretically formulated and studied, addressing in particular the physical meaning of the geometrical parameters extracted through statistical analysis of highly correlated portions of the textures. A method for isolating the deterministic textures present on a surface, called the Statistical Surface Filter, is presented and discussed in detail, and tested on existing laboratory samples. Secondly the filter is applied to preliminary measurements acquired by an innovative on-line measurement system currently under development, and evidence is shown that the technique is effective in separating the information regarding the regular patterns from the stochastic noise. The possible applications to on-line Statistical Process Control are discussed. Thirdly, the Statistical Surface Filter is tested on a set of measurements representing texturing rolls and textured sheets with different characteristics; statistical analysis of the surface parameters extracted from the filtered surfaces show that the technique allows the assessment of the different contributions of the various stages of the texturing process to the final product. Finally, a software package is implemented for the practical application of the filtering techniques and the parameters extraction; the algorithms that perform the statistical filtering are described and discussed, concluding with the operations of optimisation and fine-tuning for production-line implementation.
12

Mechanical durability of hydrophobic surfaces fabricated by injection moulding of laser-induced textures

Romano, J.-M., Gulcur, Mert, Garcia-Giron, A., Martinez-Solanas, E., Whiteside, Benjamin R., Dimov, S.S. 23 January 2020 (has links)
Yes / The paper reports an investigation on the mechanical durability of textured thermoplastic surfaces together with their respective wetting properties. A range of laser-induced topographies with different aspect ratios from micro to nanoscale were fabricated on tool steel inserts using an ultrashort pulsed near infrared laser. Then, through micro-injection moulding the topographies were replicated onto polypropylene surfaces and their durability was studied systematically. In particular, the evolution of topographies on textured thermoplastic surfaces together with their wetting properties were investigated after undergoing a controlled mechanical abrasion, i.e. reciprocating dry and wet cleaning cycles. The obtained empirical data was used both to study the effects of cleaning cycles and also to identify cleaning procedures with a minimal impact on textured thermoplastic surfaces and their respective wetting properties. In addition, the use of 3D areal parameters that are standardised and could be obtained readily with any state-of-the-art surface characterisation system are discussed for monitoring the surfaces’ functional response. / The full-text of this article will be released for public view at the end of the publisher embargo on 23 Jan 2020.
13

The Tower: Constructing a 3D Scene

Wesson, John W 01 May 2014 (has links)
This thesis describes the process of creating a 3D environment from the initial concept to the final scene. It discusses relevant research into new technology in the field of real-time rendering, including Physically Based Rendering and a synced normals workflow. It examines how the goals of the project changed over time and how the associated challenges were resolved. Conclusions are drawn about what practices were most successful, and how the development process could be improved.
14

Surface Light Field Generation, Compression and Rendering

Miandji, Ehsan January 2012 (has links)
We present a framework for generating, compressing and rendering of SurfaceLight Field (SLF) data. Our method is based on radiance data generated usingphysically based rendering methods. Thus the SLF data is generated directlyinstead of re-sampling digital photographs. Our SLF representation decouplesspatial resolution from geometric complexity. We achieve this by uniform samplingof spatial dimension of the SLF function. For compression, we use ClusteredPrincipal Component Analysis (CPCA). The SLF matrix is first clustered to lowfrequency groups of points across all directions. Then we apply PCA to eachcluster. The clustering ensures that the within-cluster frequency of data is low,allowing for projection using a few principal components. Finally we reconstructthe CPCA encoded data using an efficient rendering algorithm. Our reconstructiontechnique ensures seamless reconstruction of discrete SLF data. We applied ourrendering method for fast, high quality off-line rendering and real-time illuminationof static scenes. The proposed framework is not limited to complexity of materialsor light sources, enabling us to render high quality images describing the full globalillumination in a scene.
15

Re-texturing and compositing new material on pre-rendered media : Using DirectX and UV sampling

Blidkvist, Jesper, Westgren, Joakim January 2016 (has links)
Context: This thesis investigates a new method for re-texturing and com- positing new or additional material on specific pre-rendered images using various blend equations. This is done by sampling a number of render passes created alongside the original source material, most notably a UV pass for accurate texture positioning and different lighting passes to enhance the control over the final result. This will allow comparatively simple and cheap compositing without the overhead that other commercially available tools might add. Objectives: Render the necessary UV coordinates and lighting calculations from a 3D application to two separate textures.Sample said textures in DirectX and use the information to accurately light and position the additional dynamic material for blending with the pre-rendered media. Method: The thesis uses an implementation method in which quantita- tive data is gathered by comparing the resulting composited images using two common image comparison methods, the Structured Similarity Index (SSIM) and Peak Signal to Noise Ratio (PSNR), against a Gold Standard render. Results: The results of this implementation indicates that both the per- ceived and measured similarity is close enough to prove the validity of this method. Conclusions. This thesis shows the possibility and practical use of DirectX as tool capable of the most fundamental compositing operations. In its current state, the implementation is limited in terms of flexibility and func- tionality when compared to other proprietary compositing software packages and some visual artefacts and quality issues are present. There are however no indications that these issues could not be solved with additional work.
16

Proposed workflow for UV mapping and texture painting

Hassan, Mostafa January 2016 (has links)
Context. There are several workflows for texturing 3D models. 3D models will often have to be constructed and textured before they can be viewed in a game engine. Files would have to be exported and imported in order to view the result. This thesis will look at the usability of having the programs that are used to construct and texture assets connected with each other. In other words, a program would send and receive data in real-time which can be used to avoid the exporting and importing of assets. Objectives. Define a better workflow for texturing models that will be used for games. Compare the usability in terms of speed and the bother of managing asset files. Methods. This work utilizes a comparative experiment were subjects get to test and evaluate two workflows, the traditional workflow which the subjects should already be familiar with, and the prototype system that allows subjects texture painting in real-time. Results. Results showed that all participants conducted the experiment faster using the proposed workflow rather than using the traditional one. According to the questionnaire, participants preferred the proposed workflow and did not mind having multiple application windows open simultaneously. Conclusions. The results of both questionnaire and the time correlation data were positive, suggesting that using real-time viewing when texturing assets can enhance efficiency.
17

Femtosecond-laser hyperdoping and texturing of silicon for photovoltaic applications

Lin, Yu-Ting 04 June 2016 (has links)
This dissertation explores strategies for improving photolvoltaic efficiency and reducing cost using femtosecond-laser processing methods including surface texturing and hyperdoping. Our investigations focus on two aspects: 1) texturing the silicon surface to create efficient light-trapping for thin silicon solar cells, and 2) understanding the mechanism of hyperdoping to control the doping profiles for fabricating efficient intermediate band materials. / Engineering and Applied Sciences
18

Mechanical durability of hydrophobic surfaces fabricated by injection moulding of laser-induced textures

Romano, J.-M., Gülçür, Mert,, Garcia-Giron, A., Martinez-Solanas, E., Whiteside, Benjamin R., Dimov, S.S. 22 January 2019 (has links)
Yes / The paper reports an investigation on the mechanical durability of textured thermoplastic surfaces together with their respective wetting properties. A range of laser-induced topographies with different aspect ratios from micro to nanoscale were fabricated on tool steel inserts using an ultrashort pulsed near infrared laser. Then, through micro-injection moulding the topographies were replicated onto polypropylene surfaces and their durability was studied systematically. In particular, the evolution of topographies on textured thermoplastic surfaces together with their wetting properties were investigated after undergoing a controlled mechanical abrasion, i.e. reciprocating dry and wet cleaning cycles. The obtained empirical data was used both to study the effects of cleaning cycles and also to identify cleaning procedures with a minimal impact on textured thermoplastic surfaces and their respective wetting properties. In addition, the use of 3D areal parameters that are standardised and could be obtained readily with any state-of-the-art surface characterisation system are discussed for monitoring the surfaces' functional response. / European Commission H2020 ITN programme “European ESRs Network on Short Pulsed Laser Micro/Nanostructuring of Surfaces for Improved Functional Applications” (Laser4Fun) under the Marie Skłodowska-Curie grant agreement No. 675063 (www.laser4fun.eu) and the UKIERI DST programme “Surface functionalisation for food, packaging, and healthcare applications”. In addition, the work was supported by three other H2020 programmes, i.e. the projects on “Modular laser based additive manufacturing platform for large scale industrial applications” (MAESTRO), “High-Impact Injection Moulding Platform for mass-production of 3D and/or large micro-structured surfaces with Antimicrobial, Self-cleaning, Anti-scratch, Anti-squeak and Aesthetic functionalities” (HIMALAIA) and “Process Fingerprint for Zero-defect Net-shape Micromanufacturing” (MICROMAN).
19

Thin-wall injection molding of polystyrene parts with coated and uncoated cavities

Masato, Davide, Sorgato, M., Babenko, Maksims, Whiteside, Benjamin R., Lucchetta, G. 29 December 2017 (has links)
Yes / The paper reports an investigation on the mechanical durability of textured thermoplastic surfaces together with their respective wetting properties. A range of laser-induced topographies with different aspect ratios from micro to nanoscale were fabricated on tool steel inserts using an ultrashort pulsed near infrared laser. Then, through micro-injection moulding the topographies were replicated onto polypropylene surfaces and their durability was studied systematically. In particular, the evolution of topographies on textured thermoplastic surfaces together with their wetting properties were investigated after undergoing a controlled mechanical abrasion, i.e. reciprocating dry and wet cleaning cycles. The obtained empirical data was used both to study the effects of cleaning cycles and also to identify cleaning procedures with a minimal impact on textured thermoplastic surfaces and their respective wetting properties. In addition, the use of 3D areal parameters that are standardised and could be obtained readily with any state-of-the-art surface characterisation system are discussed for monitoring the surfaces' functional response.
20

Effects of mould wear on hydrophobic polymer surfaces replicated using plasma treated and laser-textured stainless steel inserts

Dimov, Stefan, Romano, J.-M., Sarasa, J.F., Concheso, C., Gülçür, Mert,, Dashtbozorg, B., Garcia-Giron, A., Penchev, P., Dong, H., Whiteside, Benjamin R. 12 July 2020 (has links)
Yes / The mass production of polymeric parts with functional surfaces requires economically viable manufacturing routes. Injection moulding is a very attractive option however wear and surface damage can be detrimental to the lifespan of replication masters. In this research, the replication of superhydrophobic surfaces is investigated by employing a process chain that integrates surface hardening, laser texturing and injection moulding. Austenitic stainless steel inserts were hardened by low temperature plasma carburising and three different micro and nano scale surface textures were laser fabricated, i.e. submicron triangular LaserInduced Periodic Surface Structures (LIPSS), micro grooves and Lotus-leaf like topographies. Then, a commonly available talc-loaded polypropylene was used to produce 5000 replicas to investigate the evolution of surface textures on both inserts and replicas together with their functional response. Any wear orsurface damage progressively built up on the inserts during the injection moulding process had a clear impact on surface roughness and peak-to-peak topographies of the replicas. In general, the polymer replicas produced with the carburised inserts retained the wetting properties of their textured surfaces for longer periods compared with those produced with untreated replication masters. / European Union’s H2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No. 675063 (www.laser4fun.eu). The work was also supported by three other H2020 projects, i.e. “HighImpact Injection Moulding Platform for mass-production of 3D and/or large micro-structured surfaces with Antimicrobial, Self-cleaning, Anti-scratch, Anti-squeak and Aesthetic functionalities” (HIMALAIA, No. 766871), “Process Fingerprint for Zero-defect Net-shape Micromanufacturing” (MICROMAN, No. 674801) and “Modular laser based additive manufacturing platform for large scale industrial applications” (MAESTRO, No. 723826). Further support was provided by the UKIERI DST programme “Surface functionalisation for 18/20 Accepted in the journal Tribology – Materials, Surfaces & Interfaces. food, packaging, and healthcare applications”

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