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Operation of a Direct Methanol Fuel Cell (DMFC) at high temperature with vapor feed can avoid many of the issues of conventional low temperatures DMFC, such as crossover, low efficiency and high catalyst loading. Here we investigate the behavior of a PBI-phosphoric acid membrane based DMFC. This project has two goals. The first goal is to investigate the effect of temperature and methanol concentration on the performance of Direct Methanol Fuel Cell (DMFC). The second goal is to investigate the effect of temperature and methanol on its oscillatory behavior under constant current or constant voltage operation. In this project, we use a commercial polybenzimidazole (PBI)-phosphoric acid based membrane electrode assembly (MEA), namely, Celtec-P 1100 from BASF. The Celtec-P 1100 MEA is actually designed for high temperature operation with referenced hydrogen. This kind of MEA operates at temperatures between 140℃ to 180℃, tolerating high concentrations of carbon monoxide and running independently of humidification. This study uses different vaporized concentration methanol instead of hydrogen at the anode and oxygen at the cathode. We tested in different conditions, the concentration of methanol from 1M to 10M and the operating temperature from 160℃ to 180℃. Results show that the performance of fuel cell increases with temperature up to 180℃ and the effect of methanol concentration is small. Further, oscillatory behavior is observed and reported for the first time. The oscillation is not significantly affected by the temperature and methanol concentration, current density or voltage. However, the oscillation is in special region in different condition.

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No description available.

No description available.

In this work, numerical simulations of flow separation control are performed. The sep-aration control technique studied is called 'synthetic jet actuation'. The developed code employs a cell centered finite volume scheme which handles viscous, steady and unsteady compressible turbulent flows. The pulsating zero mass jet flow is simulated by imposing a harmonically varying transpiration boundary condition on the airfoil's surface. Turbulence is modeled with the algebraic model of Baldwin and Lomax. The application of synthetic jet actuators is based in their ability to energize the boundary layer, thereby providing signifcant increase in the lift coefficient. This has been corroborated experimentally and it is corroborated numerically in this research. The performed numerical simulation investigates the flow over a NACA0015 air-foil. For this flow Re = 9??105 and the reduced frequency and momentum coefficient are F+ = 1:1 and C?? = 0:04 respectively. The oscillatory injection takes place at 12.27% chord from the leading edge. A maximum increase in the mean lift coefficient of 93% is predicted by the code. A discrepancy of approximately 10% is observed with corresponding experimental data from the literature. The general trend is, how-ever, well captured. The discrepancy is attributed to the modeling of the injection boundary condition and to the turbulence model.A sensitivity analysis of the lift coefficient to different values of the oscillation parameters is performed. It is concluded that tangential injection, F + ?? O(1) and the utilized grid resolution around the site of injection are optimal. Streamline fields ob-tained for different angles of injection are analyzed. Flow separation and attachment as functions of the injection angle and of the velocity of injection can be observed. It is finally concluded that a reliable numerical tool has been developed which can be utilized as a support tool in the optimization of the synthetic jet operation and in the modeling of its operation.

Clinical concerns exist regarding the delivered tidal volume (Vt) during high-frequency oscillatory ventilation (HFOV). HFOV is increasingly being used as a lung protective mode of ventilation for patients with Adult Respiratory Distress Syndrome (ARDS), but caution must be utilized. The purpose of this study was to investigate the effect of airway compliance on Vt delivered by HFOV to the adult patient. Method: An in vitro model was used to simulate an adult passive patient with ARDS, using a high fidelity breathing simulator (ASL 5000, IngMar Medical). The simulation included independent lung ventilation with a fixed resistance and adjustable compliance for each lung. Compliances of 10, 15, 20 and 25 ml/cmH2O were used and resistance (Raw) was fixed at 15 cm H2O/L/s. The ventilator SensorMedics 3100B (Cardinal Health, Dublin, Ohio) was set to a fixed power setting of 6.0, insp-% of 33%, bias flow =30 L/min, and 50% oxygen and Hz of 5.0 (n=5) for each compliance setting. Mean airway pressure (mPaw) and amplitude (AMP) varied as the compliance changes were made. Approximately 250 breaths were recorded at each compliance setting and the data was collected via the host computer and transferred to a log to be analyzed by SPSS v. 10. Data Analysis: The data analysis was performed using SPSS v. 10 to determine the statistical significance of the delivered Vt with different compliances, different AMP and a fixed power setting. A probability of (p < 0.05) was accepted as statistically significant. Results: The average delivered Vt with each compliance was 124.181 mL (range of 116.4276 mL and 132.6637 mL) and average AMP of 84.85 cm/H2O (range 82.0 cm/H2O and 88.0801 cm/H2O) n=5. There was an inverse relationship between Vt and AMP at a fixed power of 6.0. As compliance improved Vt increased and there was a corresponding decrease in AMP. The one-way ANOVA test showed that there were significant differences between the delivered tidal volume and AMP at a fixed power setting. When the post hoc Bonferroni test was used the data showed significant differences between AMP achieved with each compliance change and a fixed power of 6.0. When the post hoc Bonferroni test was used the data showed significant differences between Vt delivered with each compliance change and a fixed power setting of 6.0. Conclusion: Vt is not constant during HFOV. Compliance is one determinant of Vt in adults with ARDS during HFOV. AMP and Vt are inversely related during HFOV at a fixed power setting and improving compliance.

The meniscus is a soft, fibrocartilaginous tissue critical for the maintenance of normal knee biomechanics, providing shock absorbance and overall joint lubrication and stability. The adult tissue is highly avascular with a poor autonomous repair capacity in response to injury. Despite the estimated 850,000 arthroscopic surgeries performed per year to repair torn menisci and the increasing evidence showing a high incidence of meniscal degeneration during very early stages of osteoarthritis, little is currently known of the responses of meniscal fibrochondrocytes to physiological stimuli. Therefore, this work explored the responses of meniscal fibrochondrocytes to exogenous biomechanical and biochemical stimuli in an effort to better understand the sensitivity of these cells in their native tissue matrix as well as in a 3-D scaffold environment. Using the immature bovine model, the changes in biosynthesis of fibrochondrocytes in tissue explants and in an agarose scaffold due to unconfined oscillatory compression were explored. This biomechanical stimulus, previously identified to stimulate matrix production of chondrocytes of articular cartilage, stimulated total protein synthesis in both culture environments. In contrast, the synthesis of proteoglycans, matrix components important in mechanical stiffness and hydration of the tissue, was not affected by these compression protocols. However, the use of a biochemical stimulus in the form of anabolic cytokines significantly enhanced both protein and proteoglycan synthesis as a function of culture environment as well as type of cytokine used. The superposition of oscillatory compression in addition to the use of these potent biochemical stimulators, insulin-like growth factor-I or transforming growth factor-beta 1, did not further enhance matrix synthesis of fibrochondrocytes in agarose culture, suggesting an insensitivity of the fibrochondrocytes to biomechanical stimuli during early stages of matrix maturation within the agarose scaffold. As a combination of biomechanical and biochemical stimuli are responsible for directing the development, maintenance, and repair of the tissue, these findings aid in understanding fibrocartilage maintenance through studying responses in a tissue explant model. Additionally, studying agarose scaffolds aid in the understanding fibrocartilage development and deposition of a de novo matrix.

In todays highly maneuverable jet aircraft designs, aircraft are required to have a propulsion system that can operate during sudden accelerations and rapid changes in angle-of-attack. Consequently, the compressor of the jet engine occasionally must operate at low-flow rates and rapid changes in inlet conditions. The high angle-of-attack and low-flow regime of compressor operation is often plagued by rotating stall and surge. Rotating stall and surge can result in loss of engine performance, rapid heating of the blades, and severe mechanical stresses. Traditional methods for suppressing rotating stall and surge only partially protect against rotating stall or reduce compressor efficiency. The objective of this research is to design a stall suppression system that will introduce oscillatory blowing into one of the rotor blade (stall suppression blade). This oscillatory blowing method has been tested on a wing section in a wind tunnel and has shown to increase the stall angle-of-attack by several degrees.\cite{gilarranzetal02} This increase in stall angle-of-attack will eliminate stall cells as they form in the compressor. The goal of this research is to design a single stage axial compressor that will incorporate the new oscillatory blowing stall suppression system; moreover, this research will design, build, and test a scaled down version of this suppression system.