Carbon monoxide (CO) is a colourless and highly toxic gas. The detection of CO is a key requirement for safety and control in combustion processes. A number of sensors are currently available but all have drawbacks with most if not all having questions raised about their effective detection of CO over other gases such as hydrogen and methane. The power consumption of some methods of gas sensing is high as the active material must be heated to 400.600°C in order to function. The aim of this project was to attempt to eliminate this high power requirement and to study the design, fabrication and testing of CO sensors which function at room temperature, based on a supported platinum electrode in combination with a solid polymer electrolyte. It is therefore conceivable that the power source of such a sensor could be a battery, which could power a microcontroller and the relatively simple diagnostic testing equipment in a final commercial product.

In this study the development of an improved electrochemical fuel cell sensor for the detection of low-levels of formaldehyde vapour is described. Current fuel cell sensors used in the commercial Formaldemeter™ instrument lack sensitivity, respond to methanol, and show an interference response to humidity. For the detection and accurate determination of low-level concentrations of formaldehyde an improvement in these characteristics is essential. Two routes were investigated to achieve these requirements. Firstly the oxygen reduction reaction at the cathode was replaced with that of a conducting polymer, polyaniline (P ANI). Before construction of the fuel cells the stability and open circuit behaviour of various P ANI films were investigated in order to assay their suitability as a cathode material in a fuel cell application. Based on these results various fuel cells containing P ANI as the cathode were prepared and incorporated into the FormaldemeterTM. The cells were then evaluated using a calibrated vapour stream. Fuel cells containing a Pt-black anode and a P ANI/SOlcoated Pt-black cathode in H2S04 electrolyte displayed a significant improvement in sensitivity, selectivity and a reduced humidity response. In addition a fast response time, excellent reproducibility and a long shelf life was demonstrated. It is proposed that a P ANI film coated on Pt-black behaves as a more stable electron sink for the cathodic reaction instead of the oxygen reduction reaction which is dependent on the diffusion of oxygen. The fast fuel cell response time is explained by the fast switching of PAN I « lOJls). In the second part of the work, the effect of changing fuel cell catalyst was investigated. Initially, the electrocatalytic activity of various noble metals and alloys electrodeposited on glassy carbon were investigated. Based on these results several fuel cell electrodes were prepared and characterised by SEM and EDAX. Fuel cells were then constructed and their performance evaluated. Cells made up of 50:50 % atomic weight ratio of platinum and palladium showed that while the fuel cell was active towards low levels of formaldehyde, its response to equivalent levels of methanol was very small.

Made available in DSpace on 2014-06-11T19:35:06Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-08-28Bitstream added on 2014-06-13T20:06:26Z : No. of bitstreams: 1 dias_ds_dr_araiq.pdf: 2168209 bytes, checksum: 92fc6fd83876c2b2bf91b5e580b4f894 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Com o avanço da tecnologia e industrialização houve um aumento de produtos descartáveis de uso doméstico ou industrial. A partir de então, tem início o trabalho de coleta seletiva e a reutilização desses produtos nas mais diversas áreas. Os “plásticos” são os produtos mais agressivos ao meio ambiente devido a sua difícil degradabilidade. Entre eles está o PET (polietileno tereftalato). Sabendo que garrafas PET pós-consumo (PET-R) é um problema muito sério no meio ambiente devido a sua alta resistência a degradação, pensou-se na sua reutilização, preparando blendas poliméricas com poli(3- hidroxibutirato), (PHB), que pertence a uma família de polímeros biodegradáveis, os polihidroxialcanoatos (PHAs) produzidos a partir de matéria-prima renovável como o açúcar da cana, matérias amiláceas e óleos vegetais. O PHB apresenta desvantagens como alto grau de cristalinidade e instabilidade térmica. Para melhorar essas características, o preparo de blendas poderia aliar as características dos polímeros convencionais, que são poucos degradáveis, mas possuem boas propriedades mecânicas com os polímeros biodegradáveis. Esse trabalho tem como objetivo a obtenção de blendas poliméricas na forma de mistura mecânica e na forma de filmes a partir de solução de PET-R e PHB (PHBPET-R) em várias proporções de massa As misturas obtidas foram caracterizadas utilizando Termogravimetria (TG), Calorimetria Exploratória Diferencial (DSC), difratometria de raios X, espectrometria na região do infravermelho (FTIR), Microscopia Eletrônica de Varredura (MEV) e Microscopia Óptica (MO). Os resultados obtidos por TG, DSC, MEV e MO evidenciam que amostras obtidas por métodos e proporções diferentes possuem comportamento térmico e morfologia diferente. Os parâmetros cinéticos foram obtidos utilizando o modelo de Flynn - Wall e Ozawa e a partir... / With the advancement of technology and industrialization is verified an increase of household disposable products and industrial. The disposable products and reused of in several field. The plastic products are harmful to the environment due to their hand degradability, among them is the PET (polyethylene terephthalate). Once that post- consumer PET bottles (PET-R) constitutes a very serious problem in the environment due to its high resistance to degradation, it was thought in his re-obtain polymer blends with poly (3-hydroxybutyrate) (PHB), which belongs to a family of biodegradable polymers, the polyhydroxyalkanoates (PHAs) produced from renewable raw materials such as sugar from cane, vegetable oils and starch materials. The PHB presents disadvantages such as high degree of crystallinity and thermal instability. To improve these characteristics, a solution would be the preparation of blends. Thus, one can combine the characteristics of conventional polymers, which are few degradable but have good mechanical properties with biodegradable polymers. The aim of this study was investigate the synthesis of polymer blends in the form of mechanical mixture and in the form of films from solution between PET and R-PHB (PHBPET-R) in various proportions of mass. The mixtures obtained were characterized using thermogravimetry (TG), differential scanning calorimetry (DSC), X ray diffraction, spectroscopy in the infrared (FTIR), scanning electron microscopy (SEM) and optical microscopy (OM). The results obtained by TG, DSC, SEM and OM showed that samples obtained by different methods and proportions present different thermal behavior and morphology. The kinetic parameters were obtained using the model of Flynn - Wall and Ozawa and from the values of activation energy (Ea) and pre-exponential factor log A were evaluated the change of kinetic energy (Ea) on alpha (α) and ... (Complete abstract click electronic access below)

No description available.

A common misconception in our understanding of the history of conducting stems from a failure to identify properly the origin of beat patterns. Berlioz's L'Art du chef d'orchestra, written in 1844, has long been accepted as the first major text to codify both the principles of conducting and the beat-patterns conductors have employed to facilitate communication with performers.The beat-patterns illustrated in L'Art du chef d'orchestre had actually been in existence for well over a century before Berlioz wrote about them. The present study will document the existence of beat patterns prior to 1844 and examine their influence on performance practice.

No description available.

No description available.

The purpose of this study was to identify and describe the convictions about choral conducting is held and applied by Caro Carapetyan which may have contributed to his superior choral work. The primary source of information was a series of personal interviews with Carapetyan. The report was organized into five sections. The first part supplied background material. Subjects covered in the report include philosophy, the relationship between conductor and singers the conductor's knowledge of music history and literature, rehearsal planning, conducting technique the selection of singers, choral tone, blend and balance, diction, intonation, rhythm, and dynamics. Each of the chapters in Parts II, III and IV includes a summary and some comparisons with other choral music sources. The fifth part is a summary of the findings, conclusions, and recommendations. Recommendations for choral conductors and future researchers are included.

No description available.

No description available.