Thesis (PhD) - Swinburne University of Technology, 2006. / Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Civil Engineering, Swinburne University of Technology - 2006. Typescript. Includes bibliographical references.

Diss. (sammanfattning) Stockholm : Tekn. högsk., 2001. / Härtill 7 uppsatser.

Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2005. / Anderson, David, Committee Chair ; Barnwell-III, Thomas, Committee Member ; Clements, Mark, Committee Member ; Truong, Kwan, Committee Member ; Basu, Saugata, Committee Member. Vita. Includes bibliographical references.

Thesis (M. Sc.)--University of Hong Kong, 1999. / Includes bibliographical references (leaves 83-88).

Thesis (M.S.)--Brigham Young University. Dept. of Physics and Astronomy, 2007. / Includes bibliographical references (p. 103-109).

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 27-29). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1996. / Typescript. Vita. Includes bibliographical references (leaves 27-29). Also available on the Internet.

Thesis (Ph. D.)--Florida State University, 2005. / Advisor: Dr. Christopher K. W. Tam, Florida State University, College of Arts and Sciences, Dept. of Mathematics. Title and description from dissertation home page (viewed Sept. 21, 2005). Document formatted into pages; contains xv, 118 pages. Includes bibliographical references.

Thesis (MScEng)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: Active noise reduction (ANR) is a method of cancelling acoustic noise in a defined enclosure. Two methods exist to implement ANR, they are the analog feedback method and the digital feedforward method. Commercial ANR systems employing feedback methods have been around since the 1980's. Feedforward methods have however only become practically implemental with the age of fast real time digital signal processing. In current systems, feedback ANR is used to attenuate broadband noise whilst feedforward methods are used to attenuate narrow band or tonal noise [2]. This thesis investigates feedforward ANR to cancel broadband acoustic noise in aircraft headsets. Different adaptive filters, optimal configuration of adaptive filters and practical limitations to broadband attenuation for headsets are addressed. Results from this thesis show that at least 10dS noise energy attenuation is attainable over a bandwidth of 2.5kHz. A number of areas for further research are also identified. / AFRIKAANSE OPSOMMING: Aktiewe geraas beheer (AGS) is 'n metode om akoestiese geraas te kanselleer in 'n gedefinieerde omgewing. Twee metodes bestaan om AGS te implementeer. Hulle is die analoog terugvoer en digitale vorentoevoer metode. Kommersiële AGS wat die terugvoer metode gebruik is al in gebruik van die 1980's. Vorentoevoer metodes is egter eers sedert vinnige intydse digitale sein prosessering moontlik. In huidige stelsels word terugvoer AGS gebruik vir die attenuasie van wyeband geraas terwyl vorentoevoer metodes gebruik word om nouband of enkel toon geraas te kanselleer [2]. Die tesis ondersoek vorentoevoer AGS om wyeband akoestiese geraas te kanselleer in vliegtuig kopstukke. Verskillende aanpasbare filters, optimale opstelling van aanpasbare filters en praktiese beperkings tot wyeband attenuasie vir kopstukke word ondersoek. Resultate van die tesis wys dat ten minste 10dS geraas energie attenuasie behaal kan word oor 'n bandwydte van 2.5kHz. 'n Aantal areas vir verder navorsing is ook geïdentifiseer.

Misturas de poliacetal (POM), polímero de engenharia com boas propriedades mecânicas, com poliuretano termoplástico (TPU), um polímero composto por uma fase rígida e outra flexível visam buscar alternativa de materiais a serem utilizadas em bandas externas de roldanas, visando a diminuição da emissão de ruído das roldanas quando utilizadas em sistema de movimentação de portas de armários, em contato com um trilho metálico. Neste trabalho foram avaliadas as propriedades mecânicas, físicas, térmicas e morfológica de misturas de POM/TPU nas proporções 100/0, 80/20, 70/30, 60/40, 50/50, 40/60 e 0/100 (m/m). As misturas foram preparadas em extrusora dupla rosca corrotante e após os corpos de prova foram injetados em injetora convencional. O aumento dos teores de TPU nas misturas promoveu o aumento da resistência ao impacto, à abrasão e diminuição na dureza do material. Houveram aumentos da temperatura de deflexão térmica das misturas com o aumento do teor de POM. Através da microscopia eletrônica de varredura (MEV) pode ser analisada uma mistura homogênea com partículas dispersas de TPU em formato de gotículas. A avaliação de emissão de ruído mostrou que com a diminuição do módulo de elasticidade, com o aumento da quantidade TPU na mistura, ocorre a redução da emissão de ruído do mesmo, esta redução fica evidente em frequências acima de 1kHz, ocorrendo uma redução da emissão de ruído de 2-5dB. / Submitted by Ana Guimarães Pereira (agpereir@ucs.br) on 2015-02-20T16:45:11Z No. of bitstreams: 1 Dissertacao Celso Roman Junior.pdf: 3205658 bytes, checksum: 028ff664a71b2d23dd502892c15b0e08 (MD5) / Made available in DSpace on 2015-02-20T16:45:11Z (GMT). No. of bitstreams: 1 Dissertacao Celso Roman Junior.pdf: 3205658 bytes, checksum: 028ff664a71b2d23dd502892c15b0e08 (MD5) / Bolsa Desenvolvimento de Tecnologia e Inovação / Polyoxymethylene (POM), an engineering polymer with good mechanical properties, blended with thermoplastic polyurethane (TPU), a polymer composed by a flexible and a rigid phase, are an alternative of materials to be used in external bands of pulleys, aiming to reduce the noise emission of pulleys when used in system drive cabinets doors, occurring pulleys contact with a metallic rail. In this work, the mechanical, physical, thermal and morphological properties of POM/TPU blends were evaluated in the proportions of 100/0, 80/20, 70/30, 60/40, 50/50, 40/60 and 0/100 (w/w). The blends were prepared in a twin screw extruder and after the samples were injected in a conventional injector. The increase in the levels of TPU on the blends promoted a rise in the impact resistance, abrasion and a decrease in the material hardness. There was an increase in the deflection heat temperature of the blends with enhanced content of POM. Through scanning electron microscopy (SEM) was observed a blend with the presence of dispersed TPU particles. The noise emission showed that with the decrease in the modulus of elasticity of the polymer occurs a reduction of noise emission. This reduction is evident in frequencies above 1 kHz, causing 2-5dB reduction of noise emission.