Nowadays, there are various electrokinetic phenomena which are utilized in a wide range of applications, ranging from microfluidics and colloid and interface science to electrochemistry. However, even after 200 years of research on electrokinetic phenomena, there are still open questions with respect to fundamental understanding. The focus of this thesis is on three different phenomena, i.e., streaming potential, streaming current and electroosmosis. Hence, the thesis is divided in two parts: The first part focuses on the applicability of the classical Helmholtz-Smoluchowski theory on streaming potential and streaming current measurements of poly(methyl methacrylate) (PMMA) wafers, to infer the zeta potential of this substrate in contact with liquids of defined pH and ionic strength. In detail, we perform electrical impedance spectroscopy measurements to infer the electrical resistance in a PMMA microchannel and derive novel correlations for the electrokinetic characterization of the substrate. We conclude that convection can have a significant impact on the electrical double layer configuration which is reflected by changes in the surfaces conductivity. The second part of the thesis is concerned with electroosmotic flows in porous substrates where we develop a phenomenological correlation which is based on dimensional reasoning. A large set of experiments is carried out using a relatively simple and cost-effective setup including different sintered packed beds of borosilicate microspheres. A centre-of-mass model of the experimental setup allows for the interpretation of various effects. Streaming current measurements result in a correlation for the zeta potential of borosilicate depending on ionic strength and pH of the liquid. Finally, a quantitative expression for electroosmotic flow in packed beds of granular material is derived from the experiments. This correlation can be employed with other materials as well. / Thesis (Master, Chemical Engineering) -- Queen's University, 2014-06-11 10:58:11.557

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Engineering epithelium with correct structure is essential for generating functional tissue. During tissue development, cells organize in defined patterns through cellular signalling. Artificial generation of the signalling that organizes cells within the tissue offers a novel approach for engineering tissues with appropriate structure. Planar cell polarity (PCP) is a cellular signalling pathway involved in the organization of epithelial cells. Our goal is to study the effect that co-culturing genetically distinct populations of epithelial cells, with variable levels of one of the core PCP proteins, has in epithelial cell sheet organization. MDCK cells transduced with a tagged PCP core protein (GFP-Vangl2) and wild type MDCK cells were co-cultured side-by-side. The effect of tight junction and cilia formation, and localization of the GFP-Vangl2 protein were evaluated. The results suggest that tight junction and cilia formation are not affected. On the other hand, the GFP-Vangl2 protein seems to be affected at some level.

Engineering epithelium with correct structure is essential for generating functional tissue. During tissue development, cells organize in defined patterns through cellular signalling. Artificial generation of the signalling that organizes cells within the tissue offers a novel approach for engineering tissues with appropriate structure. Planar cell polarity (PCP) is a cellular signalling pathway involved in the organization of epithelial cells. Our goal is to study the effect that co-culturing genetically distinct populations of epithelial cells, with variable levels of one of the core PCP proteins, has in epithelial cell sheet organization. MDCK cells transduced with a tagged PCP core protein (GFP-Vangl2) and wild type MDCK cells were co-cultured side-by-side. The effect of tight junction and cilia formation, and localization of the GFP-Vangl2 protein were evaluated. The results suggest that tight junction and cilia formation are not affected. On the other hand, the GFP-Vangl2 protein seems to be affected at some level.

Enhancing the performance of mixing and fluid entrainment by excitation of quasi-steady jets has been a subject of research for more than three decades. During the 1980s a special emphasis was placed on mechanically oscillating planar jets and the possibility to augment thrust of V/STOL aircraft. However, during this time, little attention was paid to the classification of flow regimes, the development of coherent structures or the existence of different regions in the flow within the jet near field. For the present study, a large aspect ratio nozzle was oscillated in the direction transverse to the width of the nozzle in simple harmonic motion. For a constant nozzle height, the stroke length, oscillation frequency and jet velocity were systematically varied. Over 240 flow cases were examined using a novel method of phase-locked flow visualisation. Following an initial analysis of the acquired data, a small subset of flow conditions was selected for further quantitative investigation using Particle Image Velocimetry (PIV). The phase-locked flow visualisation led to the identification and classification of three separate flow regimes, the Base Flow, the Resonant Flow and the Bifurcation Flow Regimes. Each regime is linked to the other regimes by the presence of a small number of repetitive coherent structures in the form of starting and stopping vortices. The analysis revealed a relationship between the stroke-to-nozzle height ratio and the ratio of the forcing frequency to the natural vortex shedding frequency in the planar jet. This directly contradicts the relationship between the Strouhal and Reynolds numbers of the jet that was proposed by previous investigators. Comparison of phase-locked PIV and flow visualisation data confirms both, the validity of the new regime classification and the identification of relevant large-scale structures. Time-averaged vorticity data are also used to further illustrate the differences between the three flow regimes. Investigation of the time-averaged qualitative data for the Base and Resonant Flow Regimes show that three distinct flow regions exist within both regimes. Adjacent to the nozzle is the initial formation region, where all large-scale structures form. This is followed by a coherent near-field region in which the jet exhibits very little spread for both the Base and Resonant Flow Regimes. Within this region no pairing of the large-scale vortices from the opposing sides of the flow can be found. This region is followed by a transition region that is marked by the sudden breakup and dissipation of all visible large-scale coherent structures. The vortex formation distance is then investigated using the available PIV data and compared with the results of previous investigations. The data show that the formation distance depends on the jet velocity, oscillation frequency and the stroke length. The agreement with previous data is poor due to differences in the method of measurement. Quantitative data are also used to investigate the centreline velocity decay in relation to changes of the jet Reynolds number and stroke-to-nozzle height ratio. The results show that the velocity decay rate increases with increasing stroke length as is expected from findings of earlier studies. In addition the centreline velocity decay rates in the mean jet transition region appear to be constant for each stroke length in the cases examined. Finally, conclusions are drawn and recommendations for future work are presented. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349701 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2009

Enhancing the performance of mixing and fluid entrainment by excitation of quasi-steady jets has been a subject of research for more than three decades. During the 1980s a special emphasis was placed on mechanically oscillating planar jets and the possibility to augment thrust of V/STOL aircraft. However, during this time, little attention was paid to the classification of flow regimes, the development of coherent structures or the existence of different regions in the flow within the jet near field. For the present study, a large aspect ratio nozzle was oscillated in the direction transverse to the width of the nozzle in simple harmonic motion. For a constant nozzle height, the stroke length, oscillation frequency and jet velocity were systematically varied. Over 240 flow cases were examined using a novel method of phase-locked flow visualisation. Following an initial analysis of the acquired data, a small subset of flow conditions was selected for further quantitative investigation using Particle Image Velocimetry (PIV). The phase-locked flow visualisation led to the identification and classification of three separate flow regimes, the Base Flow, the Resonant Flow and the Bifurcation Flow Regimes. Each regime is linked to the other regimes by the presence of a small number of repetitive coherent structures in the form of starting and stopping vortices. The analysis revealed a relationship between the stroke-to-nozzle height ratio and the ratio of the forcing frequency to the natural vortex shedding frequency in the planar jet. This directly contradicts the relationship between the Strouhal and Reynolds numbers of the jet that was proposed by previous investigators. Comparison of phase-locked PIV and flow visualisation data confirms both, the validity of the new regime classification and the identification of relevant large-scale structures. Time-averaged vorticity data are also used to further illustrate the differences between the three flow regimes. Investigation of the time-averaged qualitative data for the Base and Resonant Flow Regimes show that three distinct flow regions exist within both regimes. Adjacent to the nozzle is the initial formation region, where all large-scale structures form. This is followed by a coherent near-field region in which the jet exhibits very little spread for both the Base and Resonant Flow Regimes. Within this region no pairing of the large-scale vortices from the opposing sides of the flow can be found. This region is followed by a transition region that is marked by the sudden breakup and dissipation of all visible large-scale coherent structures. The vortex formation distance is then investigated using the available PIV data and compared with the results of previous investigations. The data show that the formation distance depends on the jet velocity, oscillation frequency and the stroke length. The agreement with previous data is poor due to differences in the method of measurement. Quantitative data are also used to investigate the centreline velocity decay in relation to changes of the jet Reynolds number and stroke-to-nozzle height ratio. The results show that the velocity decay rate increases with increasing stroke length as is expected from findings of earlier studies. In addition the centreline velocity decay rates in the mean jet transition region appear to be constant for each stroke length in the cases examined. Finally, conclusions are drawn and recommendations for future work are presented. / http://proxy.library.adelaide.edu.au/login?url= http://library.adelaide.edu.au/cgi-bin/Pwebrecon.cgi?BBID=1349701 / Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2009

The aim of this thesis is to improve understanding of the effects of rotor-rotor interference on small scale rotor systems used on Micro Air Vehicles (MAVs). Previous research on rotor-rotor interactions has focused primarily on planar co-axial and tandem rotors of large scale rotorcraft. The work presented is distinct from prior research not only in its consideration of non-planar rotor systems, but also because of the lower Reynolds numbers and the use of fixed-pitch variable-speed propulsion systems. A design for a novel adjustable rotor interaction test-rig is presented along with a methodology for acquiring accurate and repeatable steady state performance data for two interacting rotor systems. Two six-axis force balances are used to acquire instantaneous and time averaged force and torque data and PIV is used to derive instantaneous and time-averaged flow field data for single and interacting rotor cases. The resulting performance and flow field data represents a unique dataset that can be used in the analysis of small scale rotor interactions, and in the validation of CFD investigations. Results show that for disc angles of between 180 degrees and 90 degrees interactions between rotors are negligible. As the disc angle is reduced from the orthogonal case to the coaxial case interactions significantly effect thrust, pitching moment, and efficiency. It is recommended that in the design of non-planar multirotor vehicles disc angles greater than 75 degrees are utilised to avoid the strong rotor-rotor interactions seen at lower disc angles. A review of existing and future non-planar multirotor concepts shows that the majority avoid significant rotor interactions by virtue of large disc angles.

Made available in DSpace on 2014-06-11T19:34:58Z (GMT). No. of bitstreams: 0 Previous issue date: 2007-05Bitstream added on 2014-06-13T20:06:00Z : No. of bitstreams: 1 nunes_lenp_dr_guara.pdf: 1711475 bytes, checksum: 1ea89d3a534a0a1530a9ef0a0ba7cb3e (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Este trabalho trata da geração e otimização de trajetórias de um manipulador robótico planar (2D) de três graus de liberdade, num ambiente livre de obstáculos. Visto que a cinemática inversa de braços robóticos é um problema complexo que, em geral, geram múltiplas soluções, otimizam-se, aqui, estas soluções através de algoritmos genéticos (AGs). A função de avaliação do AG tem caráter multi-objetivo, de forma a minimizar os deslocamentos angulares e obter de forma precisa a posição da garra, usando funções desenvolvidas para o ambiente Matlab, tais como, GAOT e PLANMANT, devido a sua facilidade de programação e geração de gráficos. A seguir, foram obtidos resultados através de programa desenvolvido em linguagem C, utilizando a biblioteca GAUL, e tem-se avaliado o desempenho computacional de processamento. E finalmente, para a validação experimental deste estudo, tem-se implementado este procedimento em um manipulador robótico Robix RCS-6 de configuração similar ao modelo simulado. Os resultados mostram que o método implementado é eficiente, computacionalmente rápido e viável em aplicações reais. / This work treats of the generation and optimization of trajectories for a planar robotic manipulator (2D) of three degrees of freedom, in free environment obstacles. Since the inverse kinematics of robotic arms are a complex problem that, generally, generate multiple solutions, here are optimized these solutions through genetic algorithms (AGs). The evaluation function of the AG has multi-objective character which minimize the angular displacements and the positional errors, being used functions developed for the Matlab environment, such as, GAOT and PLANMANT, due its compliance of programming and graphics generation. Immediately, results were obtained through program developed in language C, using the GAUL library. The computational processing performance has been evaluated. And finally, for the experimental validation of this study, has been implemented this procedure in a robotic manipulator Robix RCS-6 of similar configuration to the simulated model. The results show that the implemented method is efficient, and computationally fast and viable in real applications. KEYWORDS: Robotic manipulator, Optimal trajectory, Inverse kinematics, Genetic algorithm.

This thesis involves the analysis of four classes of nonlinear oscillators. We investigate a damped planar pendulum subject to vertical sinusoidal displacement of appropriate amplitude and frequency, a Hamiltonian planar pendulum with support point oscillating in the vertical direction, a forced spherical pendulum as a constrained dynamical system and a spinning double pendulum with the two masses oscillating in transversal planes. The motivation for this research was to understand and determine the fundamental dynamical properties of the four model systems. For this purpose analytical and numerical tools have been employed. Linearization, phase portraits, Poincare sections, basins of attraction, KAM theory, Lyapunov exponents and normal form theory have been considered as examples. For the damped planar pendulum a rigorous analysis is presented in order to show that, in the presence of friction, the upward equilibrium position becomes asymptotically stable. Furthermore, using numerical tools, the dynamics of the system far from its equilibrium points is systematically investigated. For the undamped and parametrically perturbed planar pendulum, we use KAM type arguments to rigorously prove the stability of the equilibrium point corresponding to the upside-down position. For the spherical pendulum a numerical framework is developed, which allows orbits to explore the entire sphere. We show that the qualitative change in the Poincare sections from regular to chaotic behaviour is in excellent qualitative agreement with corresponding computations of the Lyapunov exponents. Finally we study the dynamics of the spinning double pendulum by using normal form theory. We have identified the regions in physical parameter space where a codimension-two singularity occurs. An algorithm for the Cushman-Sanders normal form is constructed and analyzed. A representative model for the truncated normal form is presented.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第21262号 / 医博第4380号 / 新制||医||1029(附属図書館) / 京都大学大学院医学研究科医学専攻 / (主査)教授 平井 豊博, 教授 伊達 洋至, 教授 渡邊 直樹 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM