The presented diploma thesis deals with designing electronic educational materials intended for learning/teaching physics at elementary schools. The work consists of the following parts. In the first part, we focuse on the description of the used HTML5 technology and its possibilities.Subsequently we analyze the applicability of the chosen technologies. The main part of the work comprises a description of designing and implementation of five selected teaching methods and their testing on interactive whiteboards and contemporary mobile devices.

Made available in DSpace on 2014-06-11T19:25:30Z (GMT). No. of bitstreams: 0 Previous issue date: 2001Bitstream added on 2014-06-13T19:06:47Z : No. of bitstreams: 1 silva_tr_me_guara.pdf: 448943 bytes, checksum: 69cd9d252dfbcf9b51952987c7904c0b (MD5) / Devido à sua dependência a um grande número de parâmetros de difícil determinação, o cálculo de coeficiente de arrasto para satélites artificiais torna-se extremamente complexo. Teorias, como as desenvolvidas por Schamberg e Sehnal levam em consideração o coeficiente de acomodação térmico e os ângulos de incidência e reflexão das moléculas na superfície do satélite. Outras teorias como a de Stalder e Zurick utilizam nas suas formulações os seguintes parâmetros: a razão entre as velocidades do satélite e das moléculas da atmosfera, o coeficiente de acomodação térmico, o ângulo de ataque e a razão entre as temperaturas da superfície do satélite e a temperatura das moléculas incidentes. Neste trabalho algumas teorias para o cálculo do coefienciente de arrasto são analisadas comparativamente. Exemplos são exibidos, utilizando como modelo os satélites SCD1, SCD2 e CBERS1. / Drag coefficient computation for artificial satellite is extremely complex due to its dependence on several parameters that are difficult to determine. Some theories for drag coefficient computation, such as those developed by Schamberg and Sehnal, took into account the thermal accommodation coefficient and the incident and reflection angles of the molecules in the satellite surface. Others theories, such as the Stalder and Zurick theories, use in their formulations the following parameters: the ratio between the satellite velocity and the velocity of the molecules in the atmosphere, the thermal accommodation coefficient, the attack angle and the ratio between the temperatures of the satellite surface and of the incident molecules. In this work some theories for drag coefficients computation are comparatively analyzed. Examples are exhibited using the satellites SCD1, SCD2 and CBERS1 as models.

Orientador: Edvaldo Sabadini / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica / Made available in DSpace on 2018-08-11T15:29:05Z (GMT). No. of bitstreams: 1 Guersoni_VanessaCristinaBizotto_D.pdf: 3480518 bytes, checksum: 90d693157249a652dfd8cc9e674e7ad2 (MD5) Previous issue date: 2008 / Resumo: Quando pequenas quantidades (da ordem de ppm) de polímeros de elevada massa molecular são dissolvidos num solvente submetidos a um escoamento turbulento, elevados níveis de redução de atrito hidrodinâmico (RA) podem ser obtidos. Quando o fluido entra em regime turbulento, ocorrem flutuações de velocidade, perturbações conhecidas por vórtices, com ampla distribuição de tamanhos. As perturbações de pequena dimensão são associadas com a perda de energia viscosa do líquido sob escoamento, sendo que os agentes redutores de atrito atuam nestas estruturas. Uma teoria bastante interessante foi desenvolvida por De Gennes para explicar o fenômeno de redução de atrito hidrodinâmico. Segundo esta teoria, deve haver uma ressonância entre a freqüência de desenvolvimento de vórtices com a freqüência de estiramento da macromolécula (dissolvida na solução) para que ocorra o truncamento da cascata de vórtices, diminuindo a dissipação de energia viscosa e, consequentemente, reduzindo o atrito hidrodinâmico. Assim, a flexibilidade da macromolécula que promove a redução de atrito é muito significativa. Neste estudo, foram usados dois polímeros flexíveis, poli(óxido de etileno), PEO e poliacrilamida, PAM, e empregadas duas técnicas para se investigar a teoria de De Gennes: impacto de gotas (¿splash¿) e reometria. No ¿splash¿, a redução de atrito foi estudada pela rápida deformação do líquido durante o impacto da gota, usando as imagens obtidas em uma câmera de alta velocidade. A porcentagem de RA foi determinada com base na altura do jato Rayleigh (uma das estruturas do ¿splash¿). Estes estudos permitiram estabelecer correlações entre a dinâmica de deformação do líquido e da cadeia polimérica. A redução de atrito estudada por reometria se baseia na mudança do esforço (torque) para manter o líquido em determinada rotação. Os resultados obtidos no reômetro são bastante reprodutíveis e permitiram a determinação de efeitos de redução de atrito para concentrações do agente de apenas 2 ppm. A degradação mecânica sofrida pelos polímeros, ao serem submetidos a intenso cisalhamento, também foi avaliada no reômetro rotacional. Um modelo cinético foi proposto para comparar a estabilidade de PEO e PAM frente a degradação mecânica. Observou-se que intrinsecamente os dois polímeros degradam na mesma taxa. Os estudos desenvolvidos no reômetro também permitiram avaliar os efeitos elásticos do agente redutor de atrito (de acordo com a teoria de de Gennes). Estes foram desenvolvidos adicionando-se pequenas concentrações (menores de 1%) de partículas rígidas de sílica em soluções aquosas contendo sistemas flexíveis (PEO). A adsorção de PEO sobre as partículas de sílica levam a formação de sistemas semi-flexíveis, afetando significativamente a capacidade de redução de atrito hidrodinâmico / Abstract: When a very small amount (in the range of ppm) of a polymer with high-molecular weight is added in turbulent flow, it can cause drastic reduction of frictional drag. In turbulent flow, the velocity fluctuation (vortices) with large size distribution is observed. The small fluctuations are associated with the loss of kinetic energy of the liquid, due to its viscosity, and the drag reducing agents act in these structures. An interesting theory was developed by de Gennes to explain the drag reduction phenomenon. According to this theory, the frequencies in which the vortices are created and the stretching of the polymer chain must be in resonance, in order to avoid the growing of the cascade of vortices, decreasing the loss of the energy (due to the viscosity), and consequently promoting the drag reduction. Therefore, the flexibility of the macromolecule is very important. In this study two flexible polymers, poly(ethylene oxide), PEO, and polyacrylamide, PAM, were used, and two techniques: the impact of drops (splash) and rheometry were employed to investigate the theory of de Gennes. For splash, the drag reduction was studied using the images of the liquid deformation during the drop impact (in range of some mili-seconds) obtained in a very fast digital camera. The percentage of drag reduction was determined using the maximum height of the Rayleigh jet (one of the splash structures). This study allows us to correlate the dynamic of the liquid deformation and the stretching of the polymer chain. The drag reduction using rheometry is based on the torque necessary to keep the liquid in a specific rotation. The results using the rheometer are very reproducible, allowing the determination of drag reduction even in very low polymer concentration (such as 2 ppm). The polymer mechanical degradation, due to the high shear, was also investigated in the rotational rheometer. A kinetic model was proposed to compare the mechanical stability of both polymers. It was observed that intrinsically, the two polymers undergo degradation in the same rate. The studies in the rheometer also allow the investigation of the elastic effect of the drag reducer agents (according to the theory of de Gennes). They were developed by adding small amounts of colloidal silica particles (less than 1%). The adsorption of the PEO chain at the surfaces of the particle, results in a semi-flexible system, affecting the capability of the particle to promote drag reduction / Doutorado / Físico-Química / Doutor em Ciências

La réduction de la trainée aérodynamique des véhicules terrestres est un défi actuel dans l’industrie automobile. La région de basse pression du sillage à l’arrière des voitures est responsable d’une part importante de la résistance à l’avancement. Cette étude porte sur le développement de nouvelles stratégies de manipulation de l’écoulement autour de ces géométries dans le but de réduire la traînée. Afin d’atteindre ces objectifs, nous explorons expérimentalement les effets d’un forçage fluidique sur le sillage et la traînée d’un corps au culot droit. Des jets périodiques émis aux bords de fuite du modèle, tangentiellement à l’écoulement principal et avec des fréquences et amplitudes variables sont utilisés pour forcer le sillage. Selon les conditions du contrôle, trois phénomènes sont principalement observés. Premièrement, sur la plage des fréquences comprenant celle du lâcher tourbillonnaire, les jets pulsés sont convectés et modifient l’entrainement de fluide vers la région de recirculation ainsi que l’évolution des instabilités de la couche cisaillée. Cette dynamique complexe a comme conséquence l’augmentation de la trainée du corps. De plus, une résonance subharmonique apparait quand les jets pulsés sont émis avec des fréquences voisines de deux fois la fréquence du mode global. Une importante augmentation de la trainée est alors mesurée et corrélée à une forte amplification des mouvements du sillage. Une augmentation de la fréquence de pulsation se traduit par un effet de vectorisation des couches cisaillées. En outre, une diminution de l’intensité turbulente du sillage proche ainsi qu’une réduction de l’entrainement de fluide le long des couches cisaillées sont mesurés, correspondant à une réduction globale de l’énergie cinétique turbulente de l’écoulement. Le couplage de ces effets est responsable d’une augmentation de la pression au culot et de la réduction de la traînée. Il est important de noter que ces trois régimes d’actuation sont indépendants des modes de brisure de symétrie existant dans ces écoulements, qui sont analysés ici par des études paramétriques de sensibilité aux perturbations. Les aspects physiques de ces phénomènes sont discutés par des mesures de la traînée, de la pression pariétale et de la vitesse avec différentes conditions de l’écoulement et du contrôle. L’addition d’une surface courbée au voisinage du jet pulsé permet de profiter d’un effet Coanda et augmente les réductions de traînée jusqu'à 20%dans le régime instationnaires. De façon générale, l’effet Coanda amplifie non seulement la récupération de la traînée mais préserve aussi les effets de la pulsation haute fréquence sur l’écoulement turbulent. Ces résultats encouragent le développent des actionneurs fluidique pour l’utilisation en aérodynamique des véhicules et fournissent un complément pour notre compréhension sur la traînée des corps non profilés et sa manipulation. / Aerodynamic drag reduction of bluff bodies has become a major challenge for transport vehicles. The massive flowseparation occurring behind cars, buses or trucks is responsible for a large resistance force due to the low-pressure, rearwake flow. The present study aims to develop novel strategies to manipulate the flow past such geometries as well as toassociate its modifications to the corresponding drag changes. In order to achieve this goal, we experimentally investigatethe impact of fluidic actuation on the wake and drag of a square-back bluff body. Wake forcing is performed by theemission of pulsed jets along the blunt trailing-edges of the model, tangentially to the main flow with variable frequencyand velocity. Depending on the forcing conditions, mainly three flow regimes can be identified. First, for a broadbandrange of frequencies comprising the natural wake instabilities, the convection of the jet structures enhances wakeentrainment, shortens the recirculating flow length with an increase of the bluff body drag. Besides, a subharmonicresonance takes place on the flow at forcing frequencies in the vicinity of twice the wake vortex shedding, leading to ahighly unsteady near wake with significant decrease of the bluff body base pressure. It corresponds to an importantincrease of the model’s drag. Further increase of the actuation frequency induces a wake fluidic boat-tailing by shearlayerdeviation. It additionally lowers turbulent intensity and entrainment of high momentum fluid in the shear layer,revealing an overall reduction of the wake fluctuating kinetic energy. The association of both mechanisms is responsiblefor a raise of base pressure and a decrease of the model's drag. These actuation regimes are independent of the symmetrybreaking modes, wake reversals existing in such flows, which are further clarified here by parametric sensitivity analysisusing flow perturbations. The physical features of such regimes are discussed on the basis of drag, pressure and velocitymeasurements at several upstream conditions and control parameters. By adding curved surfaces at the jet outlets totake advantage of the so-called Coanda effect, the effect of periodic actuation can be further reinforced leading to dragreductions of about 20 % in unsteady regime. In general, the unsteady Coanda blowing not only intensifies the basepressure recovery but also preserves the effect of unsteady high frequency forcing on the turbulent field. The presentresults encourage the development of fluidic control in road vehicles' aerodynamics as well as provide a complement toour current understanding of bluff body drag and its manipulation.

Detailed sensitivity numerical studies have shown that the mesh cell-size may have a drastic effect on the modelling of circulating fluidized bed with small particles. Typically, the cell-size must be of the order of few particle diameters to predict accurately the dynamical behaviour of a fluidized bed. Hence, the Euler-Euler numerical simulations of industrial processes are generally performed with grids too coarse to allow the prediction of the local segregation effects. Appropriate modelling, which takes into account the influence of unresolved structures, have been already proposed for monodisperse simulations. In this work, the influence of unresolved structures on a binary mixture of particles is investigated and models are proposed to account for those effect on bidisperse simulations of bidisperse gas-solid fluidized bed. To achieve this goal, Euler-Euler reference simulations are performed with grid refinement up to reach a mesh independent solution. Such kind of numerical simulation is very expensive and is restricted to very simple configurations. In this work, the configuration consists of a 3D periodical circulating fluidized bed, that could represent the established zone of an industrial circulating fluidized bed. In parallel, a filtered approach is developed where the unknown terms, called sub-grid contributions, appear. They correspond to the difference between filtered terms, which are calculated with the reference results then filtered, and resolved contributions, calculated with the filtered fields. Then spatial filters can be applied to reference simulation results to measure each sub-grid contribution appearing in the theoretical filtered approach. A budget analysis is carried out to understand and model the sub-grid term. The analysis of the filtered momentum equation shows that the resolved fluid-particle drag and inter-particle collision are overestimating the momentum transfer effects. The analysis of the budget of the filtered random kinetic energy shows that the resolved production by the mean shear and by the mean particle relative motion are underestimating the filtered ones. Functional models are proposed for the subgrid contributions of the drag and the inter-particle collision.

Magister Artium - MA / The last few decades have seen the development of a large body of scholarly work on drag queens and performances of femininity by men (see Barrett 1995, 1999). However, performances of masculinity by women have largely been overlooked. Research by scholars like Judith Halberstam (see Halberstam 1997, 1998) on female masculinity and the drag king performer has attempted to address this imbalance, but the phenomenon has yet to receive any attention from sociolinguists. This study aims to bring attention to performances of masculinity by women in the South African context through a multi-sited ethnography of the country’s first known drag king troupe, Bros B4 Ho's. The study will examine not only the group's stage performances, but also their activity on the online social networking platform of Facebook, using multimodal critical discourse analysis. The internet has revolutionised the way we communicate and share information, and has provided interesting new arenas for individuals to explore identity performance. In extending the investigation to include the group's online activity, the study will give a more complete picture of the negotiation of drag king subjectivities across different spaces.

The human body consists of a number of very complex, highly specialised organs which perform a variety of functions that are essential to life and health. One of the main functions of the skin, the largest of the human organs, is to maintain the integrity of the body. It does this by acting as a physical barrier, preventing micro-organisms and other potentially harmful substances from entering the body. When the integrity of the skin is damaged through injury, a self-protective mechanism is triggered and the reparative wound healing process begins. Under normal circumstances the wound healing process culminates in the skin recuperating its normal characteristics and functions at the site of the injury, with only a small visible mark being left behind. However, in some cases the wound healing process may become altered leading to the production of abnormal scars, such as keloids. Keloid scars are formed from scar tissue at the site of an injury, as a result of excessive tissue repair that extends beyond the boundaries of the original wound. These scars are characterised by excess collagen deposition produced during the wound healing process. It is estimated that as many as 20% of the black and Hispanic population are affected by keloid scarring. In addition to the aesthetic aspect, keloid scars can also be painful, itchy and prone to become infected. Keloid scar formation can be triggered by skin injuries caused by, for example, acne, wounds, shaving, burns, and surgical incisions. The mechanism by which keloid scars form is currently not well understood and consequently no effective treatments exist to date.This thesis describes an investigation into the mechanical properties of single keloid and normal skin fibroblast cells for the purpose of establishing if there is a quantitative difference between the two types of cells. This information will be of benefit to researchers looking for a better understanding of the keloid formation mechanism and for those seeking improved treatments. An atomic force microscope (AFM) was employed to indent single Keloid and normal skin fibroblast cells taken from five patients. Values for the apparent Young's modulus of the cells were then calculated by fitting the experimental data using Hertz's model. Apparent Young's modulus values were then compared. The findings of the analysis indicate that statistically, there is a significant difference in the Young's modulus values of normal and keloid cells, with keloid cells exhibiting substantially greater stiffness than normal skin fibroblast cells. To enable the keloid and normal skin fibroblast cells to be studied in as close to their natural, physiological environment as is possible the AFM experiments described in this thesis were undertaken in a phosphate buffered saline (PBS) solution. In such cases the use of a fluid medium presents additional complexities, not least of which is the introduction of a hydrodynamic drag force due to viscous friction of the cantilever with the liquid which can affect the experimental data obtained and consequently any material properties calculated as a result of using these data. In order to investigate the effect of dragging force on the experimental data obtained from the AFM a novel integrated finite element based model was developed. The model, described in this thesis, provides quantification of the drag force in AFM measurements of soft specimens in fluids, consequently enabling more accurate interpretation of the data obtained from AFM experimentation. The model is validated using extensive data obtained from AFM experimentation undertaken in a number of fluids of different viscosities, at a variety of tip velocities and platform-tip separations and by comparison with an existing analytical model. The novel model is shown to accurately account for drag forces in AFM in fluid media without the need for extrapolation of experimental data and can be employed over the range of tip geometries and velocities typically utilised in AFM experimentation.The work described in this thesis demonstrates that the AFM is a valuable tool that can be used to successfully investigate the mechanical properties of biological samples in fluids. It was shown that increased accuracy in the interpretation of data obtained from AFM experimentation can be obtained by taking into account the hydrodynamic drag force due to viscous friction of the cantilever with the liquid. The investigation into the mechanical behaviour of keloid cells described in this thesis significantly adds to the yet small body of research undertaken on keloid cells to date. The findings of the investigation will provide valuable information that will be of benefit in the future to researchers looking to develop effective treatments for the prevention, reduction or removal of keloid scars.

The effect of configuration changes and add-on devices on the drag reduction of a tractor-trailer is studied through wind tunnel tests using two 1/12-scale models. The configuration changes involve ground clearance, tractor-trailer gap, roof angle and back inclination while add-on devices include flow deflectors, skirts and gap seals. Moving surface boundary layer control as a means of drag reduction is also attempted. Both drag and pressure data are obtained to help identify local contributions. Results suggest that an optimum combination of configuration parameters can reduce drag up to 17% while the add-on devices resulted in a further decrease by a modest amount. The results with moving surface boundary layer control proved to be inconclusive. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

Thesis advisor: David Broido / We present fundamental studies of phonon and electron transport in semiconductors. First principles density functional theory (DFT) is combined with exact numerical solutions of the Boltzmann transport equation (BTE) for phonons and electrons to calculate various transport coefficients. The approach is used to determine the lattice thermal conductivity of three hexagonal polytypes of silicon carbide. The calculated results show excellent agreement with recent experiments. Next, using the infinite orders T-matrix approach, we calculate the effect of various neutral and charged substitution defects on the thermal conductivity of boron arsenide. Finally, we present a general coupled electron-phonon BTEs scheme designed to capture the mutual drag of the two interacting systems. By combining first principles calculations of anharmonic phonon interactions with phenomenological models of electron-phonon interactions, we apply our implementation of the coupled BTEs to calculate the thermal conductivity, mobility, Seebeck and Peltier coefficients of n-doped gallium arsenide. The measured low temperature enhancement in the Seebeck coefficient is captured using the solution of the fully coupled electron-phonon BTEs, while the uncoupled electron BTE fails to do so. This work gives insights into the fundamental nature of charge and heat transport in semiconductors and advances predictive ab initio computational approaches. We discuss possible extensions of our work. / Thesis (PhD) — Boston College, 2019. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Physics.

Smart skins are integrating an increasing number of functionalities in order to improve the interaction between the systems they equip and their ambient environment. Here we have developed an electromechanical soft actuator with controlled surface texture due to applied thermal gradient via electrical voltage. The device was fabricated and integrated with optimized process parameters for a prepared heater element [doped PEDOT: PSS (poly-(3, 4 ethylenedioxythiophene): poly (styrene sulfonic acid))], a soft actuator (Ecoflex 00-50/ethanol) and overall packaging case [PDMS (polydimethylsiloxane)]. To study a potential application of the proposed smart skin, we analyze the fluid drag reduction in a texture controlled water flow unit. As a result, we obtained a reduction of approximately 14% in the skin drag friction coefficient during the actuation. We conclude that the proposed soft actuator device is a preferred option for a texture-controlled skin that reduces the skin drag friction coefficient.