• Refine Query
  • Source
  • Publication year
  • to
  • Language
  • 48
  • 15
  • 11
  • 9
  • 8
  • 8
  • 3
  • 3
  • 2
  • 2
  • 1
  • 1
  • 1
  • Tagged with
  • 129
  • 23
  • 21
  • 18
  • 14
  • 13
  • 13
  • 12
  • 11
  • 11
  • 10
  • 10
  • 10
  • 10
  • 9
  • 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.
31

Compósitos processados via RTM em molde de aço carbono e de liga de alumínio: efeito da condutividade térmica nas propriedades mecânicas e térmicas / Processed composites via RTM in carbon steel and aluminum alloy mold: effect of thermal conductivity in mechanical and thermal properties

Majewski, Marcelo [UNESP] 06 February 2017 (has links)
Submitted by MARCELO MAJEWSKI null (marcelomajewski@bol.com.br) on 2017-03-20T20:40:04Z No. of bitstreams: 1 Marcelo [v13-03-2017vFINAL].pdf: 3845690 bytes, checksum: c51d5240a6bf0ae87ee09592959712cc (MD5) / Rejected by Juliano Benedito Ferreira (julianoferreira@reitoria.unesp.br), reason: Solicitamos que realize uma nova submissão seguindo as orientações abaixo: No campo “Versão a ser disponibilizada online imediatamente” foi informado que seria disponibilizado o texto completo porém no campo “Data para a disponibilização do texto completo” foi informado que o texto completo deverá ser disponibilizado apenas 6 meses após a defesa. Caso opte pela disponibilização do texto completo apenas 6 meses após a defesa selecione no campo “Versão a ser disponibilizada online imediatamente” a opção “Texto parcial”. Esta opção é utilizada caso você tenha planos de publicar seu trabalho em periódicos científicos ou em formato de livro, por exemplo e fará com que apenas as páginas pré-textuais, introdução, considerações e referências sejam disponibilizadas. Se optar por disponibilizar o texto completo de seu trabalho imediatamente selecione no campo “Data para a disponibilização do texto completo” a opção “Não se aplica (texto completo)”. Isso fará com que seu trabalho seja disponibilizado na íntegra no Repositório Institucional UNESP. Por favor, corrija esta informação realizando uma nova submissão. Agradecemos a compreensão. on 2017-03-22T13:50:06Z (GMT) / Submitted by MARCELO MAJEWSKI null (marcelomajewski@bol.com.br) on 2017-03-23T01:46:44Z No. of bitstreams: 1 Marcelo [v13-03-2017vFINAL].pdf: 3845690 bytes, checksum: c51d5240a6bf0ae87ee09592959712cc (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-03-23T16:39:23Z (GMT) No. of bitstreams: 1 majewski_m_me_guara.pdf: 3845690 bytes, checksum: c51d5240a6bf0ae87ee09592959712cc (MD5) / Made available in DSpace on 2017-03-23T16:39:23Z (GMT). No. of bitstreams: 1 majewski_m_me_guara.pdf: 3845690 bytes, checksum: c51d5240a6bf0ae87ee09592959712cc (MD5) Previous issue date: 2017-02-06 / O aumento do uso de compósitos estruturais tem levado a uma preocupação constante com a confiabilidade destes materiais. Em particular, o processo de cura das resinas na fabricação é citado como um dos problemas mais significativos no processamento de compósitos estruturais. Assim, para que essa classe de materiais possa ser economicamente viável e atender às exigências dos padrões de qualidade do setor aeronáutico, tecnologias de processamento automatizado e novas formas de matéria-prima estão sendo desenvolvidas e implantadas na fabricação. Desta forma, o objetivo da presente pesquisa foi estudar a influência das propriedades térmicas dos materiais de moldes, utilizados no processamento de compósitos via RTM, nas propriedades finais dos laminados. Foram processadas três placas de compósitos com reforço não dobrável (NCF-non-crimp fabric) biaxial [+45°/-45°] via RTM: em molde de aço 1020, laminado 1; e em liga de alumínio 5052-F, laminados 2 e 3. Para verificar a influência dos materiais dos moldes nas propriedades finais, foram analisadas a tenacidade à fratura interlaminar em modo I e investigação das superfícies de fratura pelo Microscópio Eletronico de Varredura (MEV). O comportamento térmico estudado via análise térmica dinâmico-mecânica (DMA), que avaliou as diferenças no grau de cura dos laminados 1, 2 e 3 com a análise da Tg. Nos processamentos, evidenciou-se que o molde de alumínio apresentou maior controle e estabilidade térmica, enquanto que o molde de aço apresentou maior estabilidade dimensional. Pelo modo I, observou-se maior energia de iniciação de trinca (GIc) para o laminado 1 em relação aos laminados 2 e 3. Nas imagens de fratura no MEV constatou-se a influência da fração volumétrica de fibras e a quantidade de fiber bridging. No laminado 1, observou-se mechas de fibra sobre a costura e fibras rompidas originadas do fiber bridging, que foram responsáveis pela energia adicional exigida na propagação da trinca (GI). No laminado 2 observou-se acúmulo de resina e menor quantidade de fiber bridging, consequentemente, valores intermediários de GI, já no laminado 3 notou-se a ausência de fiber bridging, o que proporcionou a propagação da trinca no domínio da matriz, apresentando o menor valor GI entre os laminados. Nos dois últimos laminados a diminuição de GIc foi atribuida ao grau de cura da resina. Na qual observou-se as transições vítreas (Tg) próximas entre os laminados 1 e 3, e para o laminado 2 a Tg foi inferior, o que demonstrou efetiva correlação entre as características térmicas dos moldes com as propriedades físicas e mecânicas finais dos laminados compósitos obtidos via RTM. / The increase use of structural composites has led to a constant concern on the reliability of these materials. In particular, curing process of resins during manufacturing are cited as one of the most significant problems in the structural composites. Therefore, in order to this class of materials can be economically viable and meet the requirements of quality in the aeronautic industry standards, automated processing technologies and new materials have been developed and implemented in manufacturing sector. Thus, this research aimed to investigate the influence of thermal properties of the mold, which was used in the processing of composites via RTM, on the final properties of the laminates. Three composite plates comprised with NCF (non-crimp fabric) reinforcement, which has biaxial [+45°/-45°] configuration, and epoxy matrix. Two molds were employed for this investigation: steel 1020, for laminate 1, and aluminum alloy 5052-F, for laminates 2 and 3, all laminates with the same fiber stacking sequence. The influence of the materials of the molds in the final properties were verified with interlaminar fracture toughness in mode I (GIc), and their images of the fractured surfaces investigated by Scanning Electron Microscope (SEM). The thermal analysis conducted with Dynamic Mechanical Thermal Analysis (DMA), which evaluated the differences in the degree of cure of laminate 1, 2 and 3 by vitreous temperature transitions (Tg). It was evidenced that the aluminium mold showed better thermal conductivity and temperature stability, while the steel mold showed higher dimensional stability. Mode I showed higher energy crack initiation (GIc) for laminate 1 than for laminates 2 and 3. In the SEM images, it was verified a change in fiber volume fraction and the amount of fiber bridging. Laminate 1 showed fiber tows on the stitch regions and ruptured fibers originated from the fiber bridging, which were responsible for the additional energy of propagation (GI). Laminate 2 showed resin accumulation and less loose fibers, and consequently, intermediate values of GI, Laminate 3 no fiber bridging occured, which showed the propagation of the crack in the matrix domain, presenting the lowest GI value between the laminates. In laminates 2 and 3, the decrease in GIc can be attributed to the degree of cure, in which correlated to the glass transitions (Tg) results. Overall, the tests demonstrated a good correlation between the thermal characteristics of the molds with the final physical and mechanical properties of the laminates obtained via RTM.
32

SIGNATURES CHIMIQUES DE L'ACTIVITE BACTERIENNE DANS LES EAUX ACIDES MINIERES

Egal, Marion 25 November 2008 (has links) (PDF)
Les microorganismes extrêmophiles jouent un rôle déterminant dans le cycle du fer (oxydation et précipitation) dans les drainages miniers acides. Les phases minérales formées peuvent piéger efficacement des éléments toxiques tels que l'arsenic. L'objectif de ce travail est de mieux comprendre le rôle de l'activité bactérienne dans les processus d'atténuation naturelle des concentrations en Fe et As dans les DMA. Pour cela, différents marqueurs potentiels de l'activité bactérienne ont été étudiés (changement de spéciation, formation de biominéraux, fractionnement isotopique). L'approche de terrain a été combinée à des expériences de laboratoire. Des variations journalières et annuelles des concentrations en fer et arsenic ont été mises en évidence dans le DMA du Reigous, attribuées respectivement à des facteurs physico-chimiques et hydrologiques. La tooéléite, un oxyhydroxysulfate de Fe(III) et As(III), est présente dans les concrétions bactériennes tout au long de l'année. L'influence des facteurs biotiques (identité des souches bactériennes d'Acidithiobacillus ferrooxidans et concentration cellulaire) sur la formation de ce minéral a été étudiée en laboratoire. L'évolution de la composition isotopique du fer dans l'eau et les solides, mesurée au cours de ces expériences d'incubation et in situ (Reigous et Rio Tinto) montre un enrichissement systématique en isotopes lourds dans les solides par rapport à l'eau de départ quelle que soit la spéciation du fer initiale. Bien que l'activité bactérienne intervienne dans l'oxydation et la précipitation du fer dans ces systèmes, les fractionnements observés sont des fractionnements d'équilibre dominés par des processus abiotiques.
33

Design and Implementation of a DMA Controller for Digital Signal Processor

Jiang, Guoyou January 2010 (has links)
<p>The thesis work is conducted in the division of computer engineering at thedepartment of electrical engineering in Linköping University. During the thesiswork, a configurable Direct Memory Access (DMA) controller was designed andimplemented. The DMA controller runs at 200MHz under 65nm digital CMOS technology. The estimated gate count is 26595.</p><p>The DMA controller has two address generators and can provide two clocksources. It can thus handle data read and write simultaneously. There are 16channels built in the DMA controller, the data width can be 16-bit, 32-bit and64-bit. The DMA controller supports 2D data access by configuring its intelligentlinking table. The DMA is designed for advanced DSP applications and it is notdedicated for cache which has a fixed priority.</p>
34

Design of High-performance DMA Controller for Multi-core Platform

Wang, Tongtong January 2006 (has links)
<p>The DMA(direct memory access) controller is a special component in DSP processor used to offload the data transferring from CPU and improve the data access efficiency in the microprocessor.</p><p>This paper describes the design and implementation of DMA(direct memory access) device for microprocessor developed using C++ Language and SystemC libraries. The main facts covered within this report are the structure of a microprocessor with embedded DMA, and some interesting points of SystemC and TLM library that are useful for the design and implementation of the system level design.</p><p>This paper starts with an introduction of the theory of DMA , the structure of the microprocessor and the multicore microprocessor. Next it goes further into the DMA specification discussion. The next chapter is the implementation of DMA and the microsystem, later on in this chapter is an explanation of the SystemC methods I used in the system design.</p><p>At last, the simulation results of the whole system is presented and analyzed. The utility of the DMA is discussed and calculated.</p><p>With all these aspects covered in the paper, it is easy for the readers to understand the DMA theory , micro architecture as well as the fundamental knowledge of SystemC.</p>
35

Methyl arsenic adsorption and desorption behavior on iron oxides

Lafferty, Brandon James 29 August 2005 (has links)
Arsenic is a toxic element that is widely distributed throughout the earth??s crust as a result of both natural geologic processes and anthropogenic activities. In virtually all environments, methylated forms of arsenic can be found. Because of the widespread distribution and toxicity of arsenic and methyl-arsenic, their adsorption behavior on soil minerals is of great interest. Although considerable attention has been given to the behavior of inorganic arsenic on mineral surfaces, little research has been conducted regarding interactions of the methyl-arsenic forms. The objective of this study was to compare the adsorption and desorption behavior of methylarsonate (MMAsV), methylarsonous acid (MMAsIII), dimethylarsinate (DMAsV), dimethylarsinous acid (DMAsIII), arsenate (iAsV), and arsenite (iAsIII) on iron oxide minerals (goethite and ferrihydrite) by means of adsorption isotherms and adsorption envelopes. Additionally, desorption envelopes were obtained using sulfate and phosphate as competitive ligands. Arsenic was measured by FI-HG-AAS. MMAsV and iAsV were adsorbed in higher amounts than DMAsV on goethite and ferrihydrite at all pH values studied. Although MMAsV and iAsV were adsorbed quantitatively at lower concentrations on goethite and ferrihydrite, as arsenic concentration was increased MMAsV was adsorbed in slightly lower quantities than iAsV. DMAsV was not quantitatively adsorbed at any concentration on goethite or ferrihydrite. MMAsV and iAsV exhibited high adsorption affinities on both goethite and ferrihydrite at pH values below 9 and showed decreasing adsorption above this point (more rapidly for MMAsV). DMAsV was adsorbed only at pH values below 8 on ferrihydrite and below 7 on goethite. MMAsV, iAsV, and DMAsV each exhibited adsorption characteristics suggesting specific adsorption on both goethite and ferrihydrite. Increased methyl substitution resulted in increased ease of arsenic release from the iron oxide surface. MMAsIII and DMAsIII exhibited no evidence for any type of specific adsorption under the conditions studied. Phosphate was a more effective desorbing ion than sulfate, but neither desorbed all arsenic species quantitatively.
36

Software caching techniques and hardware optimizations for on-chip local memories

Vujic, Nikola 05 June 2012 (has links)
Despite the fact that the most viable L1 memories in processors are caches, on-chip local memories have been a great topic of consideration lately. Local memories are an interesting design option due to their many benefits: less area occupancy, reduced energy consumption and fast and constant access time. These benefits are especially interesting for the design of modern multicore processors since power and latency are important assets in computer architecture today. Also, local memories do not generate coherency traffic which is important for the scalability of the multicore systems. Unfortunately, local memories have not been well accepted in modern processors yet, mainly due to their poor programmability. Systems with on-chip local memories do not have hardware support for transparent data transfers between local and global memories, and thus ease of programming is one of the main impediments for the broad acceptance of those systems. This thesis addresses software and hardware optimizations regarding the programmability, and the usage of the on-chip local memories in the context of both single-core and multicore systems. Software optimizations are related to the software caching techniques. Software cache is a robust approach to provide the user with a transparent view of the memory architecture; but this software approach can suffer from poor performance. In this thesis, we start optimizing traditional software cache by proposing a hierarchical, hybrid software-cache architecture. Afterwards, we develop few optimizations in order to speedup our hybrid software cache as much as possible. As the result of the software optimizations we obtain that our hybrid software cache performs from 4 to 10 times faster than traditional software cache on a set of NAS parallel benchmarks. We do not stop with software caching. We cover some other aspects of the architectures with on-chip local memories, such as the quality of the generated code and its correspondence with the quality of the buffer management in local memories, in order to improve performance of these architectures. Therefore, we run our research till we reach the limit in software and start proposing optimizations on the hardware level. Two hardware proposals are presented in this thesis. One is about relaxing alignment constraints imposed in the architectures with on-chip local memories and the other proposal is about accelerating the management of local memories by providing hardware support for the majority of actions performed in our software cache. / Malgrat les memòries cau encara son el component basic pel disseny del subsistema de memòria, les memòries locals han esdevingut una alternativa degut a les seves característiques pel que fa a l’ocupació d’àrea, el seu consum energètic i el seu rendiment amb un temps d’accés ràpid i constant. Aquestes característiques son d’especial interès quan les properes arquitectures multi-nucli estan limitades pel consum de potencia i la latència del subsistema de memòria.Les memòries locals pateixen de limitacions respecte la complexitat en la seva programació, fet que dificulta la seva introducció en arquitectures multi-nucli, tot i els avantatges esmentats anteriorment. Aquesta tesi presenta un seguit de solucions basades en programari i maquinari específicament dissenyat per resoldre aquestes limitacions.Les optimitzacions del programari estan basades amb tècniques d'emmagatzematge de memòria cau suportades per llibreries especifiques. La memòria cau per programari és un sòlid mètode per proporcionar a l'usuari una visió transparent de l'arquitectura, però aquest enfocament pot patir d'un rendiment deficient. En aquesta tesi, es proposa una estructura jeràrquica i híbrida. Posteriorment, desenvolupem optimitzacions per tal d'accelerar l’execució del programari que suporta el disseny de la memòria cau. Com a resultat de les optimitzacions realitzades, obtenim que el nostre disseny híbrid es comporta de 4 a 10 vegades més ràpid que una implementació tradicional de memòria cau sobre un conjunt d’aplicacions de referencia, com son els “NAS parallel benchmarks”.El treball de tesi inclou altres aspectes de les arquitectures amb memòries locals, com ara la qualitat del codi generat i la seva correspondència amb la qualitat de la gestió de memòria intermèdia en les memòries locals, per tal de millorar el rendiment d'aquestes arquitectures. La tesi desenvolupa propostes basades estrictament en el disseny de nou maquinari per tal de millorar el rendiment de les memòries locals quan ja no es possible realitzar mes optimitzacions en el programari. En particular, la tesi presenta dues propostes de maquinari: una relaxa les restriccions imposades per les memòries locals respecte l’alineament de dades, l’altra introdueix maquinari específic per accelerar les operacions mes usuals sobre les memòries locals.
37

Design of High-performance DMA Controller for Multi-core Platform

Wang, Tongtong January 2006 (has links)
The DMA(direct memory access) controller is a special component in DSP processor used to offload the data transferring from CPU and improve the data access efficiency in the microprocessor. This paper describes the design and implementation of DMA(direct memory access) device for microprocessor developed using C++ Language and SystemC libraries. The main facts covered within this report are the structure of a microprocessor with embedded DMA, and some interesting points of SystemC and TLM library that are useful for the design and implementation of the system level design. This paper starts with an introduction of the theory of DMA , the structure of the microprocessor and the multicore microprocessor. Next it goes further into the DMA specification discussion. The next chapter is the implementation of DMA and the microsystem, later on in this chapter is an explanation of the SystemC methods I used in the system design. At last, the simulation results of the whole system is presented and analyzed. The utility of the DMA is discussed and calculated. With all these aspects covered in the paper, it is easy for the readers to understand the DMA theory , micro architecture as well as the fundamental knowledge of SystemC.
38

Automated Protocol for the Analysis of Dynamic Mechanical Analyzer Date from Fine Aggregate Asphalt Mixes

Cavalcanti De Sousa, Pedro 2010 August 1900 (has links)
Fatigue cracking and moisture damage are two important modes of distresses in asphalt pavements. Recently, the Dynamic Mechanical Analyzer (DMA) was used to characterize fatigue cracking and evaluate the effects of moisture damage on the Fine Aggregate Matrix (FAM) portion of asphalt mixtures. The FAM specimens should be properly fabricated to represent the composition and structure of the fine portion of the mixture. The objective of the first phase of this study was to develop a standard test procedure for preparing FAM specimens such that it is representative of the mixture. The method consists of preparing loose full asphalt mixtures and sieving through different sizes. Then, the ignition oven was used to determine the binder content associated with the small size materials (passing on sieve #16). Sieve #16 is used to separate fine aggregates from the coarse aggregates. The applicability of this new method will be evaluated using a number of asphalt mixtures. The objective of the second phase of this study was to develop software to analyze the data from DMA test. Such software will enable engineers and researchers to perform the complex analysis in very short time. This is Microsoft Windows ® based software, executable in any hardware configuration under this operational system.
39

Methyl arsenic adsorption and desorption behavior on iron oxides

Lafferty, Brandon James 29 August 2005 (has links)
Arsenic is a toxic element that is widely distributed throughout the earth??s crust as a result of both natural geologic processes and anthropogenic activities. In virtually all environments, methylated forms of arsenic can be found. Because of the widespread distribution and toxicity of arsenic and methyl-arsenic, their adsorption behavior on soil minerals is of great interest. Although considerable attention has been given to the behavior of inorganic arsenic on mineral surfaces, little research has been conducted regarding interactions of the methyl-arsenic forms. The objective of this study was to compare the adsorption and desorption behavior of methylarsonate (MMAsV), methylarsonous acid (MMAsIII), dimethylarsinate (DMAsV), dimethylarsinous acid (DMAsIII), arsenate (iAsV), and arsenite (iAsIII) on iron oxide minerals (goethite and ferrihydrite) by means of adsorption isotherms and adsorption envelopes. Additionally, desorption envelopes were obtained using sulfate and phosphate as competitive ligands. Arsenic was measured by FI-HG-AAS. MMAsV and iAsV were adsorbed in higher amounts than DMAsV on goethite and ferrihydrite at all pH values studied. Although MMAsV and iAsV were adsorbed quantitatively at lower concentrations on goethite and ferrihydrite, as arsenic concentration was increased MMAsV was adsorbed in slightly lower quantities than iAsV. DMAsV was not quantitatively adsorbed at any concentration on goethite or ferrihydrite. MMAsV and iAsV exhibited high adsorption affinities on both goethite and ferrihydrite at pH values below 9 and showed decreasing adsorption above this point (more rapidly for MMAsV). DMAsV was adsorbed only at pH values below 8 on ferrihydrite and below 7 on goethite. MMAsV, iAsV, and DMAsV each exhibited adsorption characteristics suggesting specific adsorption on both goethite and ferrihydrite. Increased methyl substitution resulted in increased ease of arsenic release from the iron oxide surface. MMAsIII and DMAsIII exhibited no evidence for any type of specific adsorption under the conditions studied. Phosphate was a more effective desorbing ion than sulfate, but neither desorbed all arsenic species quantitatively.
40

Design and Analysis of a Multi-Processor Communication Protocol for Real Time Sensor Data

Franke, Markus 23 September 2008 (has links) (PDF)
At IAV GmbH, Chemnitz, an embedded platform for high-performance sensor data acquisition has been developed. Sensor data is gathered and preprocessed by two digital signal processors (DSP) which communicate bidirectionally via dual-ported memory with the central controlling instance, a Freescale MCF5484 microcontroller running uClinux. The goal of this thesis is to design, implement, analyze and optimize a real-time communication protocol between both DSPs and the microcontroller. The challenges of this thesis can be defined as follows: • A uClinux driver for the dual-ported RAM must be implemented. This driver has to employ the microcontroller’s internal DMA engine and should be integrated into the Linux kernel’s DMA framework. • The DMA engine must be thoroughly analyzed. Especially interesting is its behavior when concurrently performing data transfers. Potential influence factors onto data transfer performance and timing predictability should be experimentally identified and quantitatively characterized, if possible. • Sensor data from the DSPs to the microcontroller has to meet real-time demands and must be prioritized in some way over status and parameter data from and to the DSPs. • Correct and efficient synchronization is a must. If possible, different synchronization schemes should be compared to each other. • The achievable performance in terms of guaranteed and maximum data throughput between DSP and microcontroller as well as end-to-end bandwidth has to be estimated. • Apart from the DMA engine analysis, a general evaluation of potential and achieved performance, timing predictability and the remaining microcontroller’s processing capacity (if any) should be executed.

Page generated in 0.0186 seconds