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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.
31

Hydrogen production by steam reforming of bio-alcohols:the use of conventional and membrane-assisted catalytic reactors

Seelam, P. K. (Prem Kumar) 24 November 2013 (has links)
Abstract The energy consumption around the globe is on the rise due to the exponential population growth and urbanization. There is a need for alternative and non-conventional energy sources, which are CO2-neutral, and a need to produce less or no environmental pollutants and to have high energy efficiency. One of the alternative approaches is hydrogen economy with the fuel cell (FC) technology which is forecasted to lead to a sustainable society. Hydrogen (H2) is recognized as a potential fuel and clean energy carrier being at the same time a carbon-free element. Moreover, H2 is utilized in many processes in chemical, food, metallurgical, and pharmaceutical industry and it is also a valuable chemical in many reactions (e.g. refineries). Non-renewable resources have been the major feedstock for H2 production for many years. At present, ~50% of H2 is produced via catalytic steam reforming of natural gas followed by various down-stream purification steps to produce ~99.99% H2, the process being highly energy intensive. Henceforth, bio-fuels like biomass derived alcohols (e.g. bio-ethanol and bio-glycerol), can be viable raw materials for the H2 production. In a membrane based reactor, the reaction and selective separation of H2 occur simultaneously in one unit, thus improving the overall reactor efficiency. The main motivation of this work is to produce H2 more efficiently and in an environmentally friendly way from bio-alcohols with a high H2 selectivity, purity and yield. In this thesis, the work was divided into two research areas, the first being the catalytic studies using metal decorated carbon nanotube (CNT) based catalysts in steam reforming of ethanol (SRE) at low temperatures (<450 °C). The second part was the study of steam reforming (SR) and the water-gas-shift (WGS) reactions in a membrane reactor (MR) using dense and composite Pd-based membranes to produce high purity H2. CNTs were found to be promising support materials for the low temperature reforming compared to conventional catalyst supports, e.g. Al2O3. The metal/metal oxide decorated CNTs presented active particles with narrow size distribution and small size (~2–5 nm). The ZnO promoted Ni/CNT based catalysts showed the highest H2 selectivity of ~76% with very low CO selectivity <1%. Ethanol was shown to be a more suitable and viable source for H2 than glycerol. The dense Pd-Ag membrane had higher selectivity but a lower permeating flux than the composite membrane. The MR performance is also dependent on the active catalyst materials and thus, both the catalyst and membrane play an important role. Overall, the membrane–assisted reformer outperforms the conventional reformer and it is a potential technology in pure H2 production. The high purity of H2 gas with a CO-free reformate for fuel cell applications can be gained using the MR system. / Tiivistelmä Maailman energiankulutus on kasvussa räjähdysmäisen väestönkasvun ja voimakkaan kaupungistumisen myötä. Tällä hetkellä energian tuottamisen aiheuttamat ympäristöongelmat ja taloudellinen epävarmuus ovat seikkoja, joiden ratkaisemiseksi tarvitaan vaihtoehtoisia ja ei-perinteisiä energialähteitä, joilla on korkea energiasisältö ja jotka tuottavat vähän hiilidioksidipäästöjä. Eräs vaihtoehtoisista lähestymistavoista on vetytalous yhdistettynä polttokennotekniikkaan, minkä on esitetty helpottavan siirtymistä kestävään yhteiskuntaan. Vety on puhdas ja hiilivapaa polttoaine ja energian kantaja. Lisäksi vetyä käytetään monissa prosesseissa kemian-, elintarvike-, metalli- ja lääketeollisuudessa ja se on arvokas kemikaali monissa prosesseissa (mm. öljynjalostamoissa). Uusiutumattomat luonnonvarat ovat olleet tähän saakka merkittävin vedyn tuotannon raaka-aine. Tällä hetkellä noin 50 % vedystä tuotetaan maakaasun katalyyttisellä höyryreformoinilla. Puhtaan (yli 99,99 %) vedyn tuotanto vaatii kuitenkin useita puhdistusvaiheita, jotka ovat erittäin energiaintensiivisiä. Integroimalla reaktio- ja puhdistusvaihe samaan yksikköön (membraanireaktori) saavutetaan huomattavia kustannussäästöjä. Biopolttoaineet, kuten biomassapohjaiset alkoholit (bioetanoli ja bioglyseroli), ovat vaihtoehtoisia lähtöaineita vedyn valmistuksessa. Tämän työn tavoitteena on tuottaa vetyä bioalkoholeista tehokkaasti (korkea selektiivisyys ja saanto) ja ympäristöystävällisesti. Tutkimus on jaettu kahteen osaan, joista ensimmäisessä tutkittiin etanolin katalyyttistä höyryreformointia matalissa lämpötiloissa (<450 °C) hyödyntämällä metallipinnoitettuja hiilinanoputkia. Työn toisessa osassa höyryreformointia ja vesikaasun siirtoreaktioa tutkittiin membraanireaktorissa käyttämällä vedyn tuotantoon tiheitä palladiumpohjaisia kalvoja sekä huokoisia palladiumkomposiittikalvoja. Hiilinanoputket (CNT) havaittiin lupaaviksi katalyyttien tukimateriaaleiksi verrattuna tavanomaisesti valmistettuihin tukiaineisiin, kuten Al2O3. CNT-tukiaineelle pinnoitetuilla aktiivisilla aineilla (metalli-/metallioksidit) todettiin olevan pieni partikkelikoko (~2–5 nm) ja kapea partikkelikokojakauma. Sinkkioksidin (ZnO) lisäyksellä Ni/CNT-katalyytteihin saavutettiin korkea vetyselektiivisyys (~76 %) ja erittäin alhainen hiilimoksidiselektiivisyys (<1 %). Etanolin todettiin olevan parempi vedyn raaka-aine kuin glyserolin. Tiheillä Pd-Ag-kalvoilla havaittiin olevan vedyn suhteen korkeampi selektiivisyys mutta matalampi vuo verrattuna palladiumkomposiittikalvoihin. Membraanireaktorin suorituskyky oli riippuvainen myös katalyytin aktiivisuudesta, joten sekä kalvolla että katalyyttimateriaalilla oli merkittävä rooli kyseisessä reaktorirakenteessa. Yhteenvetona voidaan todeta, että membraanierotukseen perustuva reformointiyksikkö on huomattavasti perinteistä reformeriyksikköä suorituskykyisempi mahdollistaen tehokkaan teknologian puhtaan vedyn tuottamiseksi. Membraanitekniikalla tuotettua puhdasta vetyä voidaan hyödyntää mm. polttokennojen polttoaineena.
32

Monitorização de Bio-Sinais em Smartphones

Celso Filipe Pereira Silvestre 07 September 2013 (has links)
No description available.
33

A natureza da comunicação bios midiática

Cimino, Laura Fernanda 11 May 2010 (has links)
Made available in DSpace on 2016-04-26T18:18:33Z (GMT). No. of bitstreams: 1 Laura Fernanda Cimino.pdf: 1155152 bytes, checksum: e0109748c8084954890af5eacfaab56d (MD5) Previous issue date: 2010-05-11 / Conselho Nacional de Desenvolvimento Científico e Tecnológico / One of the recurring themes in the reported studies comunicative has been the possibility of proposing another way of dealing with communication that is able to understand the recent changes in the culture caused by the new instrumental technologies of social virtual. This study therefore is to investigate how to structure those bonds mediated by the spread of the virtualization of everyday experience and that currently result from communication media bios (conceptual metaphor used by Muniz Sodré to designate new forms of life and socialization driven by the current stage of cognitive capitalism). In other words, this research seeks to analyze and interpret the ontological character of interactive links which are reflected in real time and space self-referential and, therefore, will give the specific internal communicative action. Hence, our hypothesis is that the communication capacity of a medium is directly related to how the operating systems (codes) are organized into the various complex communicative (language). In this sense, self-referentiality of digital media for interfering in the production and distribution of informative content, while it changes the meaning of communicative procedures by means of another diagram of communicating that occurs in a continuous way and evolutionary designing a mapping between culture and ecological environment. This fact has led us to other parameters epistemological who see the bios of the media, despite its vagueness and weaknesses as an object of study, as a new, potentially capable of promoting an ecological science of communication nowadays / Uma das temáticas recorrentes nos estudos comunicativos tem sido o da possibilidade de proposição de um outro modo de tratar a comunicação que dê conta de compreender as recentes mudanças no ambiente da cultura provocadas pelo novo instrumental social das tecnologias do virtual. O objetivo desta pesquisa, portanto, é o de investigar como se estruturam àqueles vínculos mediatizados pela crescente expansão da virtualização da experiência cotidiana e que, contemporaneamente, decorrem da comunicação bios midiática (metáfora conceitual empregada por Muniz Sodré para designar novas formas de vida e socialização impulsionadas pela atual fase do capitalismo cognitivo). Em outros termos, esta pesquisa procura analisar e interpretar o caráter ontológico dos vínculos interativos que se manifestam através do tempo real e do espaço auto-referente e que, consequentemente, vão conferir especificidade à ação comunicativa. Nesse sentido, nossa hipótese é a de que a capacidade de comunicação de um meio está diretamente relacionada ao modo como os sistemas operativos (códigos) são organizados dentro dos diferentes complexos comunicativos (linguagens). Neste sentido, a auto-referencialidade do meio digital deve interferir na produção e na distribuição dos conteúdos informativos, ao mesmo tempo em que, altera o significado dos procedimentos comunicativos por meio de um outro diagrama do comunicar que ocorre de maneira processual e evolutiva, desenhando uma cartografia ecológica entre cultura e meio. Tal fato coloca-nos diante de outros parâmetros epistemológicos que vêem o bios midiático, apesar de sua indeterminação e fragilidades enquanto objeto de estudo, como um novo meio, potencialmente, capaz de promover uma ciência ecológica da comunicação na contemporaneidade
34

EL GAUCHO: BIOS A MITHOS

Rodríguez, Manuel Chávez January 1978 (has links)
No description available.
35

RE ECO BIO PARK

Jansson, Anna January 2018 (has links)
No description available.
36

Design Strategies for the Rillito River, Tucson, Arizona: Exploring the Urban Design Opportunities for Improving the River Corridor

Bio, Robert January 2007 (has links)
No description available.
37

Investigation of catalyzed hydrodechlorination reactions of organochlorines in supercritical carbon dioxide /

Aikawa, Bio, January 1900 (has links)
Thesis (Ph. D.)--Carleton University, 2001. / Includes bibliographical references. Also available in electronic format on the Internet.
38

Bio-optische Modellierung des pelagischen Oekosystems noerdlich der

Zielinski, Oliver, o.zielinski@gmx.de 12 November 1999 (has links)
No description available.
39

Untersuchungen zur zytobakteriologischen Qualität von Ziegenmilch in bayerischen Bio-Betrieben

Höhn, Sarah 10 February 2006 (has links) (PDF)
No description available.
40

Einsatz Virtueller Welten in der Aus- und Weiterbildung – Das Projekt Bio-VWe

Lattemann, Christoph, Stieglitz, Stefan 09 May 2014 (has links) (PDF)
No description available.

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