Acoustic measurements of a large cavity in a wind tunnel

Acoustic measurements were made with inside and far-field microphones. Correlation of measured frequencies with available theories indicates that existing theories are applicable over a broader range than previously shown. The cavity configuration with a partial covering downstream amplified tonal intensities. The frequency of the tones depended on cavity size, not on cavity open area. Introducing upstream disturbances decreased the amplitude of the cavity tones

LDA seeding system for the Langley Low Turbulence Pressure Tunnel

A Laser Velocimetry (LV) seeding system was specifically developed for the Langley Low Turbulence Wind Tunnel (LTPT), and it has been successfully used for LV measurements in two major tests (Juncture Flow Experiment and Gortler Experiment). The LTPT is capable of operating at Mach numbers from 0.05 to 0.50 and unit Reynolds numbers from 100,000 to 15,000,000 per foot. The test section is 3 feet wide and 7.5 feet high. The turbulence level in the test section is relatively low because of the high contraction ratio and because of the nine turbulence reduction screens in the settling chamber. A primary requirement of the seeding system was that the seeding material not contaminate or damage in any way these screens. Both solid and liquid seeding systems were evaluated, and the results are presented. They can provide some guidelines for setting up seeding systems in other similar tunnels

Laser velocimeter measurements in a wing-fuselage type juncture

A single axis, five beam, three component laser velocimeter system was used in a juncture flow experiment. A description of the seeding system developed for and used in this experiment is given. The performanace of the LV system was evaluated, and some of the problems associated with it were identified. Satisfactory results were obtained in the juncture flow experiments using this LV system

Thermal cycle testing of Space Station Freedom solar array blanket coupons

Lewis Research Center is presently conducting thermal cycle testing of solar array blanket coupons that represent the baseline design for Space Station Freedom. Four coupons were fabricated as part of the Photovoltaic Array Environment Protection (PAEP) Program, NAS 3-25079, at Lockheed Missile and Space Company. The objective of the testing is to demonstrate the durability or operational lifetime of the solar array welded interconnect design within the durability or operational lifetime of the solar array welded interconnect design within a low earth orbit (LEO) thermal cycling environment. Secondary objectives include the observation and identification of potential failure modes and effects that may occur within the solar array blanket coupons as a result of thermal cycling. The objectives, test articles, test chamber, performance evaluation, test requirements, and test results are presented for the successful completion of 60,000 thermal cycles

Rapid thermal cycling of solar array blanket coupons for Space Station Freedom

The NASA Lewis Research Center has been conducting rapid thermal cycling on blanket coupons for Space Station Freedom. This testing includes two designs (8 coupons total) of the solar array. Four coupons were fabricated as part of the Photovoltaic Array Environmental Protection Program (PAEP), NAS3-25079, at Lockheed Missiles and Space Company. These coupons began cycling in early 1989 and have completed 172,000 thermal cycles. Four other coupons were fabricated a year later and included several design changes; cycling of these began in early 1990 and has reached 90,000 cycles. The objective of this testing is to demonstrate the durability or operational lifetime (15 yrs.) of the welded interconnects within a low earth orbit (LEO) thermal cycling environment. The blanket coupons, design changes, test description, status to date including performance and observed anomalies, and any insights related to the testing of these coupons are described. The description of a third design is included

A calibration technique for a hot-wire-probe vector anemometer

Calibration tests using hot wires were conducted using a newly developed test rig that greatly reduced the data acquisition time. A comparison of measured and computed velocity vector magnitude and direction indicates the necessity of complete probe calibration to determine flow interference and/or operating limitation regions. Calibration results indicate that flow rates with 3 percent accuracy and flow angles with 5 deg accuracy are attainable

Feasibility of making sound power measurements in the NASA Langley V/STOL tunnel test section

Based on exploratory acoustic measurements in Langley's V/STOL wind tunnel, recommendations are made on the methodology for making sound power measurements of aircraft components in the closed tunnel test section. During airflow, tunnel self-noise and microphone flow-induced noise place restrictions on the amplitude and spectrum of the sound source to be measured. Models of aircraft components with high sound level sources, such as thrust engines and powered lift systems, seem likely candidates for acoustic testing

Effects of Leafy Spurge (Euphorbia esula) Infestation on Breeding Birds of the Sheyenne National Grassland, ND

Leafy spurge (Euphorbia esula) is an exotic invasive weed in the northern Great Plains. We examined the effects of leafy spurge infestation on densities and nest success of breeding birds in grasslands on the Sheyenne National Grassland (SNG), ND. We categorized spurge-infested grasslands into three levels of infestation, based on the area covered by spurge patches: (a) low (0-20%), (b) medium (20-60%) and, (c) high (\u3e 60%). We surveyed 60 100-m radius circular plots (20 in each category), and searched for nests in three 16-ha plots (one in each category). There were no statistically significant differences in mean species richness or mean species diversity among the three types of survey points. Of the eight most abundant grassland birds, only Upland Sandpiper (Bartramia longicauda) densities were significantly different among spurge categories, with highest mean density (13.5 ± 4.1 birds/100 ha) occurring on medium-spurge points. However, none of these species occurred in highest densities on high-spurge points. Le Conte\u27s Sparrows (Ammodramus leconteii) and Savannah Sparrows (Passerculus sandwichensis) were significantly negatively correlated with spurge infestation (-0.23 and -0.24, respectively). Spurge infestation was not correlated with grazing intensity (number of stems/m2: rs = -0.01; % cover: rs= -0.03). Le Conte\u27s Sparrows were negatively correlated (-0.34) with grazing intensity; whereas Savannah Sparrows were positively correlated with this factor (0.28). The low-spurge plot contained the most nests (n = 24), but nests on the high-spurge plot (n = 11) experienced the highest nest success (0.745, χ2 = 13.2, df = 2, P \u3c 0.01). There were no significant differences between successful and unsuccessful nests or between nests and nearby paired sites with respect to number of spurge stems/m2 or percent cover of spurge. However there were significant differences for other measured vegetational features. Thus, based on these data, most birds appeared to show little response to leafy spurge per se. Birds may choose microhabitats based more on characteristics of vegetation structure (e.g. ground cover, vegetation height, vertical density, litter depth) than on particular plant species. Circumstantial evidence suggests that spurge may even provide benefits for certain species through foraging opportunities and nest protection. Assuming spurge can alter vegetation structure to the detriment of grassland birds, infestation may not be high enough over much of the SNG to show a strong negative effect on bird community parameters. Other factors may obscure relationships between bird densities and spurge infestation including strong avian preferences for other vegetation characteristics, cattle grazing intensity, and habitat productivity. We surveyed the breeding bird communities of the five major habitat types (grassland, sedge meadow, wetland, savanna, and woodland) of the SNG. Grasslands contained the greatest number of total species (47), but species richness/point and species diversity/point were not significantly different among habitat types (F = 1.33, P = 0.29; F = 0.65, P 0.63, respectively). The most abundant species on grassland survey points was the Western Meadowlark (47.5 birds/100 ha). The Red-winged Blackbird was the most abundant species on sedge meadow and wetland survey points (88.5 and 382.2 birds/100 ha, respectively). Ground foragers were the most abundant guild on savanna and woodland points (236.6 and 229.3 birds/100 ha, respectively). The complex interspersion among habitat patches, combined with the relatively broad range of habitat preferences and flexibility displayed by many bird species probably lead to the observed patterns of species overlap among communities

Optimizing cardiovascular and chemopreventive benefits of aspirin: what role for the proton-pump inhibitors?

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/75584/1/j.1365-2036.2004.02347.x.pd

The effect of the low Earth orbit environment on space solar cells: Results of the Advanced Photovoltaic Experiment (S0014)

The results of post-flight performance testing of the solar cells flown on the Advanced Photovoltaic Experiment are reported. Comparison of post-flight current-voltage characteristics with similar pre-flight data revealed little or no change in solar cell conversion efficiency, confirming the reliability and endurance of space photovoltaic cells. This finding is in agreement with the lack of significant physical changes in the solar cells despite nearly six years in the low Earth orbit environment