The hovering flight of a micro air vehicle was investigated. Various flight control concepts, inspired by observation of insect and bird flight, were investigated in some detail. The concepts make use of flap frequency or phase between the flap and pitch attitudes of the wing to control the force magnitude. Tilt of the stroke plane or fuselage was used to vector the force. A flight control system was designed for each concept investigated. The investigation has revealed that the preferred control concept is one in which force vectoring is achieved by the fuselage tilt through a shift in the centre of gravity location while the force magnitude is controlled by the phase between pitch and flap attitudes. This has the advantage of reducing the vehicle weight while at the same time relaxing the demand of extremely high frequency actuators. The equations of motion based on a multi-body representation of a flapping wing micro air vehicle were derived and these form the basis for the SIMULINK flight simulation program used to carry out the above investigation. The aerodynamic model used for the simulation was obtained from force measurements with a flapping mechanism that allows the model wing to oscillate with two degrees of freedom (flap and pitch). During these measurements, the phase angle between the flap and pitch angles of the model wing was varied to determine the effects on the force magnitude and direction.

Soft tissue defects resulting from trauma, cancer surgery or congenital abnormalities can occur throughout the body, and are reconstructed with surgical flaps by plastic surgeons. Perforator flaps are the most recent applications of surgical tissue transfers. These tissue transfers are reliant on a single artery and vein, which perfuse a portion of tissue with the blood required for survival. As a result of diminished flap bulk, minimal donor site morbidity, and more donor site choices, perforator flaps are considered to be an advanced form of tissue transfer. Fifteen thighs obtained from 10 fresh human cadavers were studied. This study employed the 3D imaging software, Materialise’s Interactive Medical Image Control System (MIMICS), to create 3D models of the vascular anatomy of the thigh. In total there is an average of 88 ± 16 arterial perforators supplying the integument of the thigh from nine source arteries.

Refractive surgery is designed to minimize the need for glasses and/or contact lenses and is often used for convenience, cosmetic or occupational purposes. The two most common types of laser eye surgery are LASIK and LASEK. During LASIK, the first step is the creation of the corneal flap using either a femtosecond laser or a mechanical microkeratome. The femtosecond laser has been seen to create more uniform flaps that reduce the risk of intraoperative and postoperative flap complications compared to the mechanical microkeratome. The purpose of this study was to investigate the effect on visual outcomes of second surgery LASEK on patients following aborted LASIK surgeries due to Femtosecond laser flap complications. LASIK was performed as planned and the corneal flap was created by the femtosecond laser but could not be lifted when a surgical cut was made. The procedure was aborted and LASEK was performed within a few weeks to attain the desired vision correction. A total of 14 patients were identified over a 6-year period ranging from 2009-2015. Most patients underwent surface ablation within two weeks of the initial aborted procedure. 12 of the 14 patients had a UCVA of 20/20, while the remaining 2 patients had a UCVA of 20/25 at their last postoperative visit. None of the patients required surgical enhancements despite the flap complications and no major postoperative complications were noted in any of the patients. Provided the corneal flap was well centered and there was no evidence of microstriae or epithelial ingrowth, surface ablation LASEK can be performed within a week of the aborted LASIK procedure to minimize discomfort and trauma to the patient. LASEK is associated with a slightly longer healing time but no evidence of corneal or retinal issues were noted in these patients. None of the patients experienced any significant changes in refraction between surgeries and was thus a reliable indicator of refractive stability following the flap complication. No significant differences were noted with delaying the second surgery LASEK as several patients attained 20/20 vision when it was performed within a week. The most common flap complication was the formation of an incomplete flap that could not be lifted. The cause could not be identified.

Flaps used in modern aircraft are known to produce high-intensity noise. Their blunt side edges of the wing's flap produce vorticial wakes which are the main contributors to the noise generated. A concept called continuous mold-line (CML) link flap has been studied rigorously for its impact on the acoustic behavior of the wing. These studies found that eliminating the blunt side tips with a continuous mold-line reduces the noise generated by the wing, drastically. However, very few studies have discussed the effects of mold-line shape on its aerodynamic characteristics. Therefore, the objective of this research is to investigate the effect of shape and geometry on the aerodynamics of CML wings. First, the shape of the continuous mold-line is parametrized using a hyperbolic tangent curve. Then, using ANSYS FLUENT a computational model is developed to calculate the lift and drag generated by different CML configurations. Both, inviscid and viscous studies are performed using FLUENT's pressure-based solver. The effect of span and slope at the mid-point of the transition zone are discussed. The study found that the slope at the mid-point of the transition zone does not affect the overall lift generated by the wing. Also, increasing the span of the transition zone initially increases the drag and begins to decrease at higher span lengths. Overall, it was found that the aerodynamic characteristics (such as lift, drag, and efficiency) of the CML wing are better than the conventional blunt tip hinged flap. / Master of Science / Flaps used in modern aircraft are known to produce high-intensity noise. One of the main contributors to the high-intensity noise is the blunt side edges of the wing's flap. To eliminate the noise produced by the flaps, researchers have come up with a concept called continuous mold-line (CML) link flap. In this concept, we join the flap side edge with the main wing and thus remove the side edges. Studies undertaken till now have mainly focused on the acoustic aspects of the CML wing. Hence, this study focuses on the effect the mold-line shape has on the wing's aerodynamic behavior. The study first discusses a parametric curve that will be used to define the shape of the CML region of the wing. Then, the study calculates the aerodynamic characteristics, such as lift and drag generated by the wing, using the commercial software ANSYS FLUENT. The results obtained by changing the slope at the mid-point and length of the CML region are discussed. Finally, the study presented also compares the aerodynamic characteristics (such as lift, drag, and efficiency) of the CML wing are better than the conventional blunt tip hinged flap.

No description available.

No description available.

Introduction. Free tissue transfer is the 'gold standard' of surgical care for patients requiring composite tissue reconstruction when local options are unavailable or unsuitable. It is a form of autologous transplant wherein composite tissue is harvested from a distant site and used to reconstruct the primary defect. The flap is rendered ischaemic following transection of its vascular pedicle until successful anastomosis with the recipient vessels is completed. Ischaemia depletes cellular ATP, lowers pH and strains cellular homeostatic mechanisms. The only way to halt the inevitable progression to cell death is by reperfusion. However, reperfusion per se initially worsens the injury through the influx of inflammatory cells and mediators. This biphasic injury is named ischaemia reperfusion injury (IRI) and is characterized by microcirculatory dysfunction primarily mediated by oxidative stress. This can lead to inadequate perfusion and ultimately tissue necrosis. IRI occurs in all transplants, is unavoidable and has no treatment. Preconditioning is an intervention performed before a known event that improves the outcome of that event. The elective nature of transplants permits such interventions to be executed. Haem-­oxygenase 1 (HO-­1) is a cytoprotective enzyme that is up-­regulated in response to diverse stressors including oxidative stress. Haem arginate (HA) is a potent inducer of this enzyme. Pharmacological preconditioning with HA has been shown to reduce IRI and improve clinical outcome in models of visceral IRI. Aim: to investigate whether HA could be used to improve outcome in myocutaneous flaps. Objectives: (1) to establish a reliable model of myocutaneous IRI (2) to assess the effects of pharmacological preconditioning with HA on clinical outcome measures and (3) to investigate the mechanisms underlying the effects of HA preconditioning demonstrated in the in vivo model by in vitro work. Methods. An in situ transverse rectus abdominis myocutaneous (TRAM) flap was developed. Forty male, Lewis rats were randomly assigned to receive IV: Control (NaCl); HA; HA + tin mesoporphyrin (SnMP, an HO-­1 inhibitor) and SnMP alone. Laser Doppler imaging (LDI) scans were performed to assess perfusion. Clinical outcome was assessed by percentage area flap necrosis and perfusion. In vitro adult human epidermal keratinocytes (HEKa) were treated in: Control medium; HA; SnMP and Desferrioxamine (DF) or combinations thereof. MTT and VialightTM plus ATP assays were used to assess cytotoxicity. Intracellular reactive oxygen species (ROS) concentration was determined by flow cytometry (CMH2DCFDA assay). Statistical analysis was performed by one-­way analysis if variance (ANOVA) followed by Tukey's test. Results. In vivo preconditioning with HA increased HO-­1 protein expression and level of bioactivity. This bioactivity was successfully inhibited by SnMP. In the skin, HO-­1 up-­regulation occurred in macrophages. HA based treatments resulted in significantly worse necrosis at 48 h: Control vs HA (p = 0.01). HA based treatments significantly decreased perfusion at: 24 h (Control vs HA, p = 0.0002) and 48 h (Control vs HA, p = 0.04). By contrast, SnMP did not affect either clinical outcome measure. In vitro preconditioning with HA was cytotoxic and increased intracellular ROS: both were reversed by co-­administration of DF but not SnMP. Conclusion. In contrast to data from visceral models, HA preconditioning proved deleterious in myocutaneous flaps. This is most likely due to the generation of ROS by free haem independent of HO-­1 up-­regulation.

Com o desenvolvimento dos motores turbofan, a contribuição das estruturas hipersustentadoras no ruído total gerado pelas aeronaves tem se tornado mais considerável. Sendo que as estruturas do flape tornaram-se uma das principais fontes de ruído. Dispositivos para redução do nível sonoro nessas regiões são investigados em uma asa MD 30P30N, ensaiada em um túnel de vento adaptado para medições aeroacústicas. A localização das fontes de ruído foi obtida através de uma antena de Beamforming (técnica de identificação de fontes acústicas) com 109 microfones, dos quais 60 deles são de alta freqüência (até 40 kHz). As características aerodinâmicas foram avaliadas através de medidas de pressão na superfície do modelo, e com o mapeamento de vórtice em ponta de flape. Dentre os dispositivos avaliados para redução de ruído, foram testadas chapas porosas de diversos tamanhos. Os sinais dos microfones foram processados com o algoritmo DAMAS2 para obtenção dos espectros do Beamforming em uma região de interesse definida. As configurações com porosidade têm nível de ruído equivalente para freqüências até 2000 Hz. A partir daí, há uma redução de até 6 dB em 3200 Hz em relação ao baseline (tipo de teste aplicado à asa). Os resultados de Beamforming para duas configurações diferentes, baseline e chapa porosa foram apresentados usando uma faixa dinâmica de 12 dB, com pico de 58 dB. Observa-se que houve redução dos níveis de ruído na região selecionada. A perda de pressão total na ponta do flape mostrou que há uma aparente correlação entre o gradiente da pressão total e o nível de ruído. Estudos adicionais são necessários para entender os mecanismos de redução de ruído e assim otimizar a geometria das chapas porosas. No entanto, os resultados apresentados indicam que esses dispositivos são candidatos para aplicação em aeronaves. / With the development of high-bypass turbofan engines, the airframe contribution to the total aircraft noise has become considerable. One of the largest sources of airframe noise is the flap side-edge, which is investigated experimentally in a MD 30P30N wing. Several devices are also tested to reduce the side-edge noise, especially porous plates. Wind tunnel testing is carried out and the position of noise sources and their levels is obtained with a beamforming antenna. It has 112 microphones, in which 60 of them are suitable for acoustic measurements of up to 40 kHz. The aerodynamic characteristics are evaluated with pressure measurements on the model surface, as well as with vortex mapping on the flap side-edge. To evaluate the noise levels, microphone signals were processed with the DAMAS2 algorithm. Beamforming spectra were then obtained considering only the side-edge region. The baseline configuration and those with porous plates were tested and equivalent noise levels were obtained up to 2000 Hz. For higher frequencies, the model with porous plates has a lower noise level, reaching a difference of 6 dB in 3200 Hz, compared to the baseline configuration. Vortex mapping was carried out with a seven hole Pitot probe developed at the University for the measurement of flows with high angularity. The results for the baseline configuration allows to correlate aerodynamic and aeroacoustic data. This helps to design the side-edge region with a low noise level. Additional studies are necessary to understand the mechanisms of noise reduction and to optimize the geometry of the porous plate. However, the presented results indicate that this device is a candidate for application in aircraft, in special by its superior durability compared to the foam generally used for noise attenuation.

No description available.

An experimental investigation was undertaken to determine the ability of Synthetic Jet Actuators to control the aerodynamic properties of a wing. The Synthetic Jet Actuator (SJA) was placed at two separate positions on a wing comprised of a NACA0015 airfoil. The first of the jet positions is located at 12% of the chord, hereby referred to as the leading edge Synthetic Jet Actuator. The second exit position is located at 99% chord of an airfoil and hereby is referred to as the trailing edge Synthetic Jet Actuator. The two locations produced different benefits as the angle of attack of the wing was increased. The leading edge Synthetic Jet Actuator delayed the onset of stall of an airfoil, suppressing stall up to 25 degrees angle of attack. The control of the aerodynamic characteristics was achieved by influencing the amount of the separated flowfield region. The effects of the dynamic stall vortex were investigated with wind tunnel testing during the pitching motion of an airfoil to determine how the flow reacts dynamically. The trailing edge synthetic jet actuator was investigated as a form of low angle “hingeless” control. The study investigated the effect of the jet momentum coefficient on the ability of the synthetic jet to modify the lifting and pitching moment produced from the wind tunnel model. The data indicates that, with the present implementation, the SJA-jet flap generates moderate lift and moment coefficient increments that should be suitable for hinge- less control. It was also shown that, for the current experimental setup and a given jet momentum coefficient, continuous blowing is more effective than oscillatory blowing/sucking. The data shows that combining the SJA with a Gurney flap does not result in performance enhancement.