Performance characteristics of axisymmetric convergent-divergent exhaust nozzles with longitudinal slots in the divergent

An investigation was conducted in the Langley 16 foot Transonic Tunnel and in the static test facility of that tunnel to determine the effects of divergent flap ventilation of an axisymmetric nozzle on nozzle internal (static) and wind on performance. Tests were conducted at 0 deg angle of attack at static conditions and at Mach numbers from 0.6 to 1.2. Ratios of jet total pressure to free stream static pressure were varied from 1.0 (jet off) to approximately 14.0 depending on Mach number. The results of this study indicate that divergent flap ventilation generally provided large performance benefits at overexpanded nozzle conditions and performance reductions at underexpanded nozzle conditions when compared to the baseline (unventilated) nozzles. Ventilation also reduced the peak static and wind on performance levels

Operating Characteristics of the Multiple Critical Venturi System and Secondary Calibration Nozzles Used for Weight-Flow Measurements in the Langley 16-Foot Transonic Tunnel

An investigation has been conducted in the Langley 16 Foot Transonic Tunnel to determine the weight flow measurement characteristics of a multiple critical Venturi system and the nozzle discharge coefficient characteristics of a series of convergent calibration nozzles. The effects on model discharge coefficient of nozzle throat area, model choke plate open area, nozzle pressure ratio, jet total temperature, and number and combination of operating Venturis were investigated. Tests were conducted at static conditions (tunnel wind off) at nozzle pressure ratios from 1.3 to 7.0

Direct Experimental Evidence of Metal-Mediated Etching of Suspended Graphene

Atomic resolution high angle annular dark field imaging of suspended, single-layer graphene, onto which the metals Cr, Ti, Pd, Ni, Al and Au atoms had been deposited was carried out in an aberration corrected scanning transmission electron microscope. In combination with electron energy loss spectroscopy, employed to identify individual impurity atoms, it was shown that nano-scale holes were etched into graphene, initiated at sites where single atoms of all the metal species except for gold come into close contact with the graphene. The e-beam scanning process is instrumental in promoting metal atoms from clusters formed during the original metal deposition process onto the clean graphene surface, where they initiate the hole-forming process. Our observations are discussed in the light of calculations in the literature, predicting a much lowered vacancy formation in graphene when metal ad-atoms are present. The requirement and importance of oxygen atoms in this process, although not predicted by such previous calculations, is also discussed, following our observations of hole formation in pristine graphene in the presence of Si-impurity atoms, supported by new calculations which predict a dramatic decrease of the vacancy formation energy, when SiOx molecules are present.Comment: final version accepted in ACS Nano + supplementary info. 22+6 pages, 4+5 figure

Static internal performance of a nonaxisymmetric vaned thrust reverser with flow splay capability

An investigation was conducted in the Static Test Facility of the Langley 16-Foot Transonic Tunnel on a dual-port, nonaxisymmetric, block-and-turn type thrust reverser model with vane cascades in the reverser ports which turned the flow in the splay direction and aided in turning the flow in the reverse direction. Splaying reverser flow is a method of delaying to lower landing ground roll speeds the reingestion of hot exhaust flow into the inlets. Exhaust flow splay can also help prevent the impingement of hot exhaust gases on the empennage surfaces when the reverser is integrated into an actual airframe. The vane cascades consisted of two sets of perpendicular vanes with a variable number of turning and splay vanes. A skewed vane box was also tested which had only one set of vanes angled to provide both turning and splay. Vane cascades were designed to provide different amounts of flow splay in the top and bottom ports. Inner doors, trim tabs, and an orifice plate all provided means of varying the port area for reverser flow modulation. The outer door position was varied as a means of influencing the flow reverse angle. Nozzle pressure ratio was varied from 1.75 to approximately 6.00

Insecurity for compact surfaces of positive genus

A pair of points in a riemannian manifold $M$ is secure if the geodesics between the points can be blocked by a finite number of point obstacles; otherwise the pair of points is insecure. A manifold is secure if all pairs of points in $M$ are secure. A manifold is insecure if there exists an insecure point pair, and totally insecure if all point pairs are insecure. Compact, flat manifolds are secure. A standing conjecture says that these are the only secure, compact riemannian manifolds. We prove this for surfaces of genus greater than zero. We also prove that a closed surface of genus greater than one with any riemannian metric and a closed surface of genus one with generic metric are totally insecure.Comment: 37 pages, 11 figure

Implementing Zn²⁺ ion and pH-value control into artificial mussel glue proteins by abstracting a His-rich domain from preCollagen

A His-rich domain of preCollagen-D found in byssal threads is derivatized with Cys and Dopa flanks to allow for mussel-inspired polymerization. Artificial mussel glue proteins are accessed that combine cysteinyldopa for adhesion with sequences for pH or Zn2+ induced β-sheet formation. The artificial constructs show strong adsorption to Al2O3, the resulting coatings tolerate hypersaline conditions and cohesion is improved by activating the β-sheet formation, that enhances E-modulus up to 60%

Physical and functional fitness changes in older adults in response to a traditional training program and a Wii enhanced training program

The Wii Fit Plus Balance program has been recommended as an alternative training tool for older adults to improve physical and functional fitness. However, the effectiveness of the Wii Fit Plus in combination with traditional training approaches in older adults is unclear. PURPOSE: To compare changes in physical fitness measures in older adults (OA) engaging in two different training programs: 1) traditional exercises performed by the control group (CG) and 2) traditional exercises complemented by Wii balance games performed by the experimental group (EG). METHODS: 35 untrained OA (mean ± SD Age: 68.86 ± 6.13; BMI: 28.89 ± 5.32) with no exercise history were recruited and randomly assigned to either the CG or EG group. CG and EG programs both included cardio, strength, flexibility, and balance training exercises. However, subjects in the EG group performed additional balance exercises using Wii fit plus program. Both CG and EG subjects exercised twice per week for twelve weeks. Fitness assessments were based on standard procedures including the chair stand, gallon jug transfer, 8 foot up-and-go tests, as well as a long ramp walk and medicine ball throw tests. Data were collected at weeks 1, 6, and 12. Data analysis was conducted using the general linear mixed model with alpha level set at p\u3c0.05. RESULTS: A significant time effect was found for all fitness measures in both groups from week 1 to 6 (p\u3c0.001) and week 1 to 12 (p\u3c0.001). In general CG and EG subjects made 5.5% to 31.7% improvement from Week 1 to 6 and 8.1% to 52.5% improvement from Week 1 to 12. No significant group effects were observed between the CG and EG groups (p\u3e0.370). Also, no significant group by time interactions were observed for any of the fitness measures (p\u3e0.290). CONCLUSION: It appears that the use of the Wii Fit Plus Balance in conjunction with a traditional exercise program does not provide added significant fitness benefits for older adults. While additional fitness benefits are not evident, it appears that both a traditional exercise program alone and a traditional exercise program combined with the Wii Fit Plus Balance training may elicit significant fitness improvements

Mechanisms of Timing Across Tasks and Temporal Intervals.

This dissertation investigates whether the information-processing instantiation of scalar expectancy theory (SET) is responsible for timing durations that span both the milliseconds and seconds ranges across perceptual and motor timing tasks. A common-timer view predicts that variability increases proportionally with increasing duration in a similar fashion across tasks. We use the coefficient of variation as an estimate of temporal sensitivity, and we perform Weber slope analysis to compare estimates of duration-dependent variance across durations and tasks. Other dependent variables included measures of temporal accuracy and response latency. Experiment 1 investigated whether a common mechanism can account for performance across a range of durations within a temporal reproduction task. The results were inconsistent with a single scalar timer across durations. Experiment 2 involved using endpoint pairs to reduce anchoring effects, a larger number of stimulus durations, and the addition of a similarly structured task that emphasized perception. Temporal reproduction and discrimination tasks were run in different subject groups, and again, the data challenge a single scalar timer within reproduction and point to separate timers for the two tasks. The third experiment examined the similarly structured temporal reproduction and discrimination tasks in a within-subjects design, eliminating the procedural differences between the tasks present in Experiment 2, and allowing for analysis of individual differences. The data again revealed nonlinear timing in the two tasks as well as evidence for task-specific clocks. Overall, these data argue against the possibility of a single scalar timer across durations in motor and perceptual timing and suggest a reformulation of the processes responsible for timing in these task conditions.Ph.D.PsychologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/57725/2/abangert_1.pd