2,460 research outputs found
Comparison of language ability in children with cochlear implants in oral and total communication educational settings
No full textThe use of middle ear muscle reflexes in post-operative programming of cochlear implants
No full textModelling deposition environments around superheater tubes
Get PDFIn an important initiative to reduce carbon dioxide emission from pulverized fuel boilers, coal is now co-fired with biomass. During the combustion process, however, chlorine and sulphur in chemical compounds associated with sodium and potassium are released in a form which can deposit onto and then corrode the steel heat exchanger tubes. The deposition and corrosion can have serious implications for the power generation industry because the corrosive damage on heat exchange tubes can shorten the operational life of the boilers and lead to significant economic penalties.
The deposition and corrosion processes have been widely studied but eliminating the deposits and corrosive materials is still a challenging problem. Computational fluid dynamics (CFD) has been used to model the deposition processes and it mainly focuses on experimentally deriving constants in the models that capture some aspects of the problem such as the motion behaviour of aerosols. However, using CFD has a limitation that results in periodic instability when solving the models with numerical computation.
Modelling deposition environments around superheater tubes is a complex problem as many aspects, such as particle motion, condensation of matter and continuous combustion of particles, should be considered.This thesis has:
(1) developed a new mathematical approach that uses mesh-free methods to solve Hamilton’s equations with a consideration of the total energy of the system, where the Hamilton’s equation is scale independent;
(2) developed a model that can simulate the mass accumulation process based on graph and combinatorics theory;
(3) developed a model depicting the continuous combustion of particles in motion;
(4) developed a model depicting the behaviour of changing matter states;
(5) developed a model depicting the vapour phase deposition on particles; and
(6) verified the developed models with case studies.
This work shows the importance of homogenous and heterogeneous vapour depositions on binding particles onto superheater tubes
Architectural illustrations... 1899
No full textArchitectural illustrations / A.W. Leh. [s.l.] : The author, 1899. 1 leaf, 23 plates ; 21 x 29 cm
Processo para a produção de carvão ativo a partir do subproduto resultante da lixívia alcalina da cinza da casca do arroz
Get PDFDissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Tecnológico, Programa de Pós-Graduação em Engenharia Química, Florianópolis, 2010A busca por rotas alternativas de geração de energia e produtos comercialmente viáveis oriundos de resíduos agrícolas são fontes atuais de estudo. Um processo para desenvolver um material carbonoso ativado a partir da lixívia alcalina da cinza da casca do arroz foi proposto e discutido neste trabalho. O carvão ativo é um material carbonáceo quimicamente inerte, muito utilizado na indústria em diversas aplicações, como no tratamento de águas residuais, purificação de gases, geração de materiais antimicrobianos, etc. Na transformação da cinza da casca do arroz foram realizados procedimentos laboratoriais mecanoquímicos que visam a redução da sílica livre (quartzo), redução do teor de cinza além das impurezas que podem interferir no processo de ativação subseqüente. A amostra original e as frações obtidas através da realização de um peneiramento foram caracterizadas inicialmente quanto ao teor de cinzas, fluorescência de raios-X e difração de raios-X para avaliar sua composição e fases mineralógicas constituintes. A fração que obteve menor porção de sílica em sua composição foi utilizada como precursor na ativação química das amostras posteriores por apresentar uma melhor eficiência no processo. O ácido fosfórico foi o agente oxidante eleito e este foi utilizado em quatro proporções diferentes (relação massa de cinza: H3PO4): 1:2, 1:4, 1:8 e 1:12 sob três temperaturas de ativação: 80°C, 120°C e 180°C. Estas amostras ativadas foram caracterizadas quanto ao teor de cinza e número de iodo. Uma proporção de massa:ácido foi eleita como ideal diante dos resultados obtidos, e este carvão ativado foi analisado quanto a sua química de superfície (FTIR), área superficial (BET), porosidade e análise de imagem através da microscopia eletrônica de varredura sendo comparado à amostra original para que o processo de transformação desta matriz carbonosa fosse elucidado e o entendimento alcançado com sucesso.The search for new routes to alternative energy generation and commercially viable products derived, from agricultural waste, are sources of current study. A process to develop an activated carbonaceous material, from the alkaline digestion of rice husk ash, was proposed and discussed in this paper. The charcoal is a carbonaceous material chemically inert, widely used in industry in various applications, such as wastewater treatment, gas purification, generation of antimicrobial materials, etc. The transformation of rice husk ash were performed by mechanochemical laboratory procedures that aimed at reducing the silica (quartz), reducing the ash content and the impurities that can interfere in the subsequent activation process. The original sample and the fractions, obtained by conducting an initial bolting, were characterized as the ash content, X-ray fluorescence and X-ray diffraction to assess their mineralogical composition and phase constituents. For the future, fractions of samples that had lower portion of silica in its composition were used as precursor in the chemical activation. Phosphoric acid is the oxidizing agent elected and this was used in four different proportions (mass ratio of ash: H3PO4): 1:2, 1:4, 1:8 and 1:12 in three activation temperatures: 80 °C, 120 ºC, and 180 °C. These samples were characterized by activated ash content and iodine number. According to the results a proportion of mass ratio of ash: acid was chosen as an ideal. This activated carbon was examined for its surface chemistry (FTIR), surface area (BET), porosity and image analysis by scanning electron microscopy which were compared to the original sample so that the transformation of carbonaceous matrix was elucidated with more clarity and understanding reached with success
Contested Successions. The Transmission of Imperial Power in Tacitus’ Histories and Annals
Get PDFContains fulltext :
127811.pdf (Publisher’s version ) (Open Access)Radboud Universiteit Nijmegen, 07 juli 2014Promotores : Hekster, O.J., Ash, R. Co-promotor : Breij, B.M.C.452 p
Festuca ovina L., s.l. en Festuca rubra L., s.l. in Nederland
No full textThe author gives a survey of the taxa belonging to Festuca ovina L., s.l. and F. rubra L., s.l. as they occur in the Netherlands. Four species are distinguished, viz. F. ovina L., F. trachyphylla (Hack.) Kraj., F. heterophylla Lamk., and F. rubra L. F. ovina L. is represented by 3 subspecies, subsp. tenuifolia (Sibth.) Čelak., subsp. ovina, and subsp. cinerea (Vill.) Duyfjes, nov. comb.; F. rubra L. can be subdivided into 2 subspecies, subsp. rubra and subsp. juncifolia (St. Am.) R. Lit.
Of these taxa F. heterophylla is most probably introduced with grass-seeds; the others are native
Effective Shoulder Design and Maintenance: TR-531, 2007
No full textGranular shoulders are an important element of the transportation system and are constantly subjected to performance problems due to wind- and water-induced erosion, rutting, edge drop-off, and slope irregularities. Such problems can directly affect drivers’ safety and often require regular maintenance. The present research study was undertaken to investigate the factors contributing to these performance problems and to propose new ideas to design and maintain granular shoulders while keeping ownership costs low. This report includes observations made during a field reconnaissance study, findings from an effort to stabilize the granular and subgrade layer at six shoulder test sections, and the results of a laboratory box study where a shoulder section overlying a soft foundation layer was simulated. Based on the research described in this report, the following changes are proposed to the construction and maintenance methods for granular shoulders:
• A minimum CBR value for the granular and subgrade layer should be selected to alleviate edge drop-off and rutting formation.
• For those constructing new shoulder sections, the design charts provided in this report can be used as a rapid guide based on an allowable rut depth. The charts can also be used to predict the behavior of existing shoulders.
• In the case of existing shoulder sections overlying soft foundations, the use of geogrid or fly ash stabilization proved to be an effective technique for mitigating shoulder rutting
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