Aerodynamic flow control can improve aerofoil performance by influencing the natural growth of boundary layers, which develop on the surface of vehicles moving in viscous fluids. Many active and passive techniques have been developed to reduce drag and/or increase the lift of aerofoil sections. The work presented in this thesis is concerned with the active excitation of the boundary layer on the suction side of aerofoil sections through momentum transfer via a secondary flow. The secondary flow was achieved by air passing through an air breathing device (ABD) which was implemented in the aerofoil surface. This resulted in an almost tangential and uni-directional fluid interaction. Numerical and experimental work showed a beneficial influence of the secondary flow on the aerodynamic characteristics of the studied aerofoil sections. A Taguchi analysis was initially used to confirm findings from previous work on the use of an ABD on a NACA0012 aerofoil section. The resulting parameter ranking showed general agreement with previous data in that the most important parameters are the gap-size i.e. the length over which the two fluids are in contact and the velocity gradient between the two fluids. However, it also raised questions that required an additional in-depth analysis of the parameters governing the flow control process. Due to the greater importance to the modern aviation industry of the NACA65-415 aerofoil section this particular cambered aerofoil section was used for further investigations. This study highlighted the importance of the velocity gradient between the main and secondary flows as well as the location of interaction of the ABD. In addition the gap-size is also important. Consideration of the power requirements for the ABD indicated that this may limit exploitation of the device. An evolutionary search strategy based on genetic algorithms, was employed to optimize the air breathing geometry. This optimisation produced non-intuitive geometries which revealed the importance of promoting an inner fluid recirculation in the device. Finally experimental data in a closed loop wind-tunnel showed trends which were in general agreement with the numerical predictions. However, the measurements indicated significantly greater enhancements of lift forces than those predicted by thenumerical investigation.

Submitted by DANIELA BRANCO TAVARES MASCAGNI null (danibtmascagni@gmail.com) on 2017-07-19T19:56:50Z No. of bitstreams: 1 TESE final.pdf: 4219528 bytes, checksum: 2e34e6b34687082855e27d79457027bc (MD5) / Approved for entry into archive by Luiz Galeffi (luizgaleffi@gmail.com) on 2017-07-19T20:03:40Z (GMT) No. of bitstreams: 1 mascagni_dbt_dr_bauru.pdf: 4219528 bytes, checksum: 2e34e6b34687082855e27d79457027bc (MD5) / Made available in DSpace on 2017-07-19T20:03:41Z (GMT). No. of bitstreams: 1 mascagni_dbt_dr_bauru.pdf: 4219528 bytes, checksum: 2e34e6b34687082855e27d79457027bc (MD5) Previous issue date: 2017-04-24 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Neste trabalho, foram desenvolvidos biossensores eletroquímicos enzimáticos fabricados com óxido de grafeno reduzido (rGO) e funcionalizado depositados pelas técnicas LbL (Layer-by-Layer) e Langmuir-Blodgett (LB) para a detecção de glicose. Para isso, primeiramente foi sintetizado quimicamente o óxido de grafeno (GO) pela oxidação do grafite, em seguida, o GO foi reduzido para aumentar a sua condutividade elétrica e foi funcionalizado em meio estabilizante contendo cloridrato de poli(dialildimetilamônio), formando o GPDDA, ou poli(4-estireno sulfônico) PSS, formando GPSS. Com isso, foi possível formar dispersões aquosas estáveis das nanofolhas de grafeno, essencial para a fabricação de filmes LbL. Em um primeiro momento, foram fabricados biossensores com filmes LbL contendo GPDDA, GPSS e a enzima glucose oxidase (Gox). O desempenho desses biossensores na detecção de glicose foi avaliado em função do número de bicamadas contendo Gox. O melhor desempenho na detecção de glicose foi apresentado pelo biossensor com o filme LbL com a arquitetura (GPDDA/GPSS)/(GPDDA/GPSS)2. Este biossensor apresentou limite de detecção de 13,4 µmol.L-1, sensibilidade 2,47 μA.cm-2.mmol-1.L e faixa analítica entre 0,04 e 0,95 mmol.L-1. Este biossensor foi eficiente na detecção de glicose na presença de interferentes comumente encontrados em fluidos corporais, alimentos e fármacos. Quando avaliado na detecção de glicose em amostras reais, recuperou 100,8% para uma solução eletrolítica comercial e 88,8% para leite sem lactose. Em um segundo momento, foram fabricados biossensores a partir de filmes LB contendo os mesmos materiais utilizados para fabricar os biossensores com filmes LbL (GPDDA, GPSS e Gox), com a finalidade de comparar os dois métodos de fabricação de filmes no desempenho dos biossensores. O desempenho dos biossensores fabricados com filmes LB foi avaliado em relação à quantidade de monocamadas (GPDDA/GPSS/Gox) depositadas. O melhor desempenho na detecção de glicose entre os biossensores com filme LB foi apresentado pelo biossensor de arquitetura (GPDDA/GPSS/Gox)3. Este biossensor apresentou limite de detecção 0,54 µmol.L-1, sensibilidade de 8,69 μA.cm-2.mmol-1.L e faixa analítica entre 0,0018 e 1,5 mmol.L-1. Também se mostrou eficiente na detecção de glicose na presença de interferentes e na detecção de glicose em amostra real, com recuperação de 101,2 % para o leite sem lactose. A partir dos resultados de desempenho dos biossensores com filme LbL e LB foi possível concluir que a técnica LB promoveu uma maior sinergia entre os nanomateriais, atribuída ao maior ordenamento dos nanomateriais proporcionado pela técnica LB. / In this work, enzymatic electrochemical biosensors fabricated with reduced graphene oxide (rGO) and functionalized deposited by the LbL (Layer-by-Layer) and LangmuirBlodgett (LB) techniques were developed for the detection of glucose. Firstly, to get this, graphene oxide (GO) was chemically synthesized by the oxidation of graphite and after GO was reduced to increase its electrical conductivity and it was functionalized in stabilizing medium containing the poly (diallyl dimethyl ammonium chloride) PDDA, forming the GPDDA, or poly (4-styrene sulphonic) PSS, forming GPSS. Hence, stable aqueous dispersions of graphene nanosheets were formed, essential for the fabrication of LbL films. In a first moment, biosensors with LbL films containing GPDDA, GPSS and the enzyme glucose oxidase (Gox) were fabricated. The performance of these biosensors in the detection of glucose was evaluated as a function of the number of bilayers containing Gox. The best performance in the detection of glucose was presented by the biosensor with the LbL film with the architecture (GPDDA/GPSS)/(GPDDA/GPSS)2. It presented a detection limit of 13.4 μmol.L-1 , sensitivity 2.47 μA.cm-2 .mmol-1 .L and analytical range between 0.04 and 0.95 mmol.L-1 . This biosensor was efficient in detecting glucose in the presence of interferents commonly found in body fluids, foods and drugs. When evaluated in the detection of glucose in real samples, it recovered 100.8% for a commercial electrolytic solution and 88.8% for lactose-free milk. In a second moment, biosensors were fabricated from LB films containing the same materials used to fabricate the biosensors with LbL films (GPDDA, GPSS and Gox), in order to compare the two methods of films deposition in the performance of the biosensors. The performance of biosensors fabricated with LB films was evaluated in relation to the amount of deposited monolayers (GPDDA/GPSS/Gox). The best performance on the detection of glucose among LB film biosensors was presented by the architecture biosensor (GPDDA/GPSS/Gox)3. The detection limit was 0.54 μmol.L-1 , sensitivity of 8.69 μA.cm- 2 .mmol-1 .L and analytical range between 0.0018 and 1.5 mmol.L-1 . This biosensor was also efficient in the detection of glucose in the presence of interferents and in the detection of glucose in a real sample, with a recovery of 101.2% for lactose-free milk A conclusion derived from the performance results of the biosensors with LbL and LB films, may support that LB technique promoted a greater synergy among the nanomaterials, attributed to the best arrangement of nanomaterials provided by LB technique.

No description available.

Surface chemistry of wood is based on the exposed cut surface that is the combination of intact (lumen wall) and cut cell wall material. It is inherently complex and changes with history of processing. Modification of wood surface through noncovalent attachment of amine containing water soluble polyelectrolytes provides a path to create functional surfaces in a controlled manner. Furthermore, modification of the surface can be performed using layer-by-layer (LbL) assembly, where the adsorption of polyelectrolytes or nanoparticles in sequential steps yields a multilayer film with a defined layer sequence on a given substrate. The objective of this study was to quantify adsorption of polyelectrolytes onto wood surface and use these polyelectrolytes as adhesives. In this study, optimal pH conditions for modifying wood surfaces, by anchoring adsorbing polyelectrolytes, were detected using zeta- ( )-potential measurements. Positively charged wood surfaces were also detected by the same technique after a layer of poly(diallyldimethylammonium chloride) (PDDA) or poly (ethylenimine) (PEI) was adsorbed. Both X-ray photoelectron spectroscopy (XPS) and Carbon-Nitrogen-Sulfur analyzer (CNS) were used to quantify the amount of charged polymer on wood surfaces to elucidate optimal pH and ionic strength for polyelectrolyte adsorption. Confocal laser scanning microscopy (CLSM) and Environmental Scanning Electron Microscope (ESEM) were used to characterize adsorbed LbL multilayers of poly(acrylic) acid (PAA) and poly(allylamine hydrochloride) (PAH). Cross-linking between PAA and PAH at various temperatures was studied by Fourier Transform Infrared Spectroscopy (FTIR) and the evaluation of multilayer as bonding agents was carried out by compression shear test following ASTM D905 standard. / Master of Science

No description available.

In this thesis, we present results of studies of the electronic band structures and related electronic properties of some layered transition metal chalcogenides and their intercalation complexes. The materials investigated include group VIIc transition metal dichalcogenides, and 2H-TaS<SUB>2</SUB> and its lithium-, lead-, and tin-intercalated complexes, as well as dihafnium sulphide and selenide. Both experimental measurements and theoretical elect'onic band structure calculations have been carried out. The types of measurements conducted consist of reflectivity measurements in the energy range from 0.5 eV to 4.5 eV using the home-made reflectivity spectrometer, and electron energy loss measurements in the energy range up to 100 eV using the scanning transmission electron microscope as well as some characterization experiments (structural, chemical composition and thermal properties). The experimental investigations were restricted to the layered group VIIc metal dichalcogenides. All the electronic band structures are calculated using the linearized muffin-tin orbital (LMTO) method, and are reported for the first time except PdTe<SUB>2</SUB> and 2H-TaS<SUB>2</SUB>. The obtained electronic band structures for the Ni-group metal dichalcogenides, and the semiconductor-metal shift in progression from PtS<SUB>2</SUB> through PtSe<SUB>2</SUB> to PtTe<SUB>2</SUB> are discussed in terms of the binding energies of the atomic valence orbitals of the constituent atoms, the local coordination of the metal atoms and the symmetry of the crystals as well as the charge transfer effects. A superlattice structural phase transition is proposed for PtSe<SUB>2</SUB>, which may possibly explain the anomaly observed in the previous transport measurement. The previous photoemission spectra from NiTe<SUB>2</SUB>, PdTe<SUB>2</SUB> and PtTe<SUB>2</SUB>, and dHvA measurement on PdTe<SUB>2</SUB> are compared with their band structures in details, and a good agreement is found. Other available experimental data including the previous transport, optical and magnetic susceptibility measurements as well as the reflectivity and electron energy loss spectra measured in this work are also discussed in terms of these electronic structures. The band structure calculations for dihafnium chalcogenides predict that these materials are metals. They also suggest that there is a strong bonding between Hf atoms in the adjacent layers, thus giving rise to the rigidity in the c-direction which may preclude the intercalation of these materials. The results for 2H-TaS<SUB>2</SUB> and its intercalation complexes show that the rigid band model is essentially correct for 2H-LiTaS<SUB>2</SUB> but is an oversimplication for the post-transition metal intercalation compounds. Changes in the electronic structure upon intercalation are discussed in terms of the intercalant-host charge transfer and the hybridisation between the host states and the intercalation valence orbitals. Electrical conduction in 2H-PbTaS<SUB>2</SUB> and SnTaS<SUB>2</SUB> is found to be largely due to the p-valence electrons from the intercalant Pb (Sn) layers, resulting in the considerable increase in the superconducting transition temperature following intercalation. The results are also compared with the observed optical and transport properties and a broad agreement is found. The band structures and the electronic properties of other layered transition metal dichalcogenides and their intercalation complexes, as well as the band structure calculation techniques for the layered compounds are also reviewed in this thesis.

No description available.

No description available.

No description available.

Receptivity refers to the generation of boundary layer instability waves by external disturbances. Recent work by M. E. Goldstein has set the general framework for the different types of boundary layer receptivity mechanisms. Therefore, it is now understood that receptivity occurs near the leading edge or at locations downstream where the boundary layer undergoes a rapid streamwise adjustment. The present work analyzes the receptivity due to a free-stream acoustic wave interacting with a suction surface--hard wall junction. In this case, receptivity occurs because of the rapid changes in wall suction distribution. Analytical expressions for the amplitude of the generated instability wave have been derived and numerical estimates provided for parameter values typical of hybrid laminar flow control applications. The importance of the junction receptivity as compared to other receptivity mechanisms has been assessed.