Experimental assembly of structures in EVA: Hardware morphology and development issues

A large body of data was obtained by MIT during neutral boyancy testing at Marshall Space Flight Center from 1980 to the present. These efforts, and the most significant results are summarized. The Experimental Assembly of Structure in EVA (EASE) flight experiment was undertaken to validate these results and flown on the STS 61-B in November 1985. The EASE experiment hardware is discussed and how the experiment goals dictate its size, shape, and operational characteristics, are illustrated

Empirical Support for Establishing Common Assumptions in Cost Research in Education

The economic evaluation of educational policies and programs employing the ingredients method for cost, cost-effectiveness, or benefit-cost analysis is no exception to the critique that economic models require an untenable number of assumptions. Educational economists must make assumptions due to two sources of uncertainty: model uncertainty, as in the well-documented debate over the selection of the appropriate social discount rate to calculate present value and empirical uncertainty due to the infeasibility of gathering sufficiently detailed data on all resources. This paper highlights the frequency of empirical assumptions made in the education literature and proposes a set of harmonized assumptions to address empirical uncertainty that can be used to increase comparability of economic evaluation across programs and across studies. By building consensus on a set of reasonable, empirically derived assumptions that are selected so as to minimally distort the results of evaluations, differences in costs, cost effectiveness, and benefit-cost ratios can be more confidently ascribed to meaningful differences in resource use, program implementation, and program effectiveness, as opposed to differences in choices made by the analyst

Penetration of Air Jets Issuing from Circular, Square, and Elliptical Orifices Directed Perpendicularly to an Air Stream

An experimental investigation was conducted to determine the penetration of air jets d.irected perpendicularlY to an air stream. Jets Issuing from circular, square, and. elliptical orifices were investigated. and. the jet penetration at a position downstream of the orifice was determined- as a function of jet density, jet velocity, air-stream d.enaity, air-stream velocity, effective jet diameter, and. orifice flow coeffIcient. The jet penetrations were determined for nearly constant values of air-stream density at three tunnel-air velocities arid for a large range of Jet velocities and. densities. The results were correlated in terms of dimensionless parameters and the penetrations of the various shapes were compared. Greater penetration was obtained. with the square orifices and the elliptical orifices having an axis ratio of 4:1 at low tunnel-air velocities and low jet pressures than for the other orifices investigated. The square orifices gave the best penetrations at the higher values of tunnel-air velocity and jet total pressure

Incipience of two-phase flow from a stratified gas-liquid region in multiple discharging branches : experimental investigation including PIV measurements

The importance of predicting the incipience of two-phase flow from a stratified gas-liquid region in discharging branches has strong implications in industries where safe operation is of primary concern. This is particularly true in the nuclear reactor industry, where two-phase flow in the reactor cooling channels occurs due to a loss-of-coolant accident (LOCA). The incipience of two-phase flow can be characterized by the location of the gas-liquid interface relative to the discharging branch. If the gas-liquid interface is above the discharging branch, gas can entrain into the branch liquid flow by either vortex formation or vortex-free gas pull through. If the gas-liquid interface is below the discharging branch, liquid can entrain into the branch gas flow. A semi-circular test section geometry, with three discharging branches, was used to simulate a typical CANDU header-feeder. The experimental investigation consisted of a two part study. In the first, the onset of liquid entrainment was investigated in multiple discharge scenarios. In the second, the liquid velocity flow field was investigated at the onset of gas entrainment in a single discharging bottom branc

Experiments and Modeling of the Onset of Gas Entrainment into Small Branches from a Co-Currently Flowing Stratified Gas-Liquid Regime

The discharge of two-phase flow from a co-currently flowing gas-liquid region through single or multiple branches is an important process in many industrial applications including oil-gas production and nuclear power plants. Accurate physical descriptions of the flow phenomena involved, along with the quality and mass flow rate of the discharging streams, is necessary to adequately predict the different phenomena associated with the process. A test facility was developed, consisting of a horizontal pipe with an inlet diameter of 50.8 mm and three 6.35 mm diameter branches located at a distance of 1.8 m from the pipe inlet. The branches were machined perpendicularly into the test section wall, and oriented at 0, 45, and 90 degrees down from horizontal. Air and water, operating at 206 kPa, were used to provide a two-phase flow regime. Both fluids flowed co-currently within the inlet, and mainly in the stratified regime, but transitions to wavy and slug regimes were observed. Extensive experimental data are reported for the three branch orientations. The relation between the air-water interface height, the inlet superficial gas and liquid velocities, and the branch two-phase quality and mass flow rate are presented for each branch orientation. The critical inlet conditions leading to beginning of two-phase flow in the branch, the onsets of gas and liquid entrainment, respectively, were reported in both single and dual branch cases. Effects of inlet measurement location, the secondary branch Froude number, and branch fluid phase on the critical conditions were investigated. A novel map relating the dual discharge branch Froude numbers, the inlet superficial liquid velocity, and the related dual branch phenomena was developed. The map presented the three observed modes of gas entrainment during dual discharge. A two-fluid separated theoretical model was developed in order to predict the critical height at the onset of gas entrainment in a bottom branch. Potential flow theory leads to the branch being simulated by a point-sink, while the flowing liquid upstream of the branch was simulated by a uniform constant crossflow velocity. Two analytical criteria were used to predict the dip position (height and offset distance) relative to the branch. Inaccuracies with experiments lead to the inclusion of empirical terms to satisfy the local crossflow velocities within the inlet. A digital imaging technique was also developed in order to record local interface profiles at the onset of gas entrainment, and was used to satisfy the relationship between the dip height and offset distance. The semi-empirical approach provided a significant improvement over the purely analytical model, and demonstrated that the critical height to be predicted within a reasonable error

Management of Wintering Short-eared Owls at Airports in the Lower Great Lakes Region

USDA Wildlife Services airport wildlife biologists have been tasked with reducing the hazards that raptors (including owls) pose to safe aircraft operations at airports and military airfields throughout the USA. A review of available wildlife strike information suggests short-eared owls (Asio flammeus) are frequently struck by aircraft during the winter months at numerous airports within the Lower Great Lakes Region of the United States. Further, this species is listed as ‘endangered’ by state fish and wildlife agencies in many states, although not at the federal level. Consequently, there is particular interest in developing non-lethal management tools for reducing the hazards posed by this species. In an effort to gain a better understanding of the efficacy of managing the hazards to aviation posed by short-eared owls, we developed methods to live-capture, mark with USGS aluminum leg bands, and translocate short-eared owls from airport environments (i.e., airfield areas) as part of the overall programs to reduce wildlife hazards to safe aircraft operations at airports. During 2012−2015, a total of 32 short-eared owls was live-captured, banded, and translocated to release sites approximately 64 to 80 km (40 to 50 miles) away from the airports. Only 1 short-eared owl (3%) was resighted and this bird was found on a different airport from where it had been translocated from. Future research in needed to evaluate the efficacy of translocating wintering short-eared owls from airport environments

Management of Wintering Short-eared Owls at Airports in the Lower Great Lakes Region

USDA Wildlife Services airport wildlife biologists have been tasked with reducing the hazards that raptors (including owls) pose to safe aircraft operations at airports and military airfields throughout the USA. A review of available wildlife strike information suggests short-eared owls (Asio flammeus) are frequently struck by aircraft during the winter months at numerous airports within the Lower Great Lakes Region of the United States. Further, this species is listed as ‘endangered’ by state fish and wildlife agencies in many states, although not at the federal level. Consequently, there is particular interest in developing non-lethal management tools for reducing the hazards posed by this species. In an effort to gain a better understanding of the efficacy of managing the hazards to aviation posed by short-eared owls, we developed methods to live-capture, mark with USGS aluminum leg bands, and translocate short-eared owls from airport environments (i.e., airfield areas) as part of the overall programs to reduce wildlife hazards to safe aircraft operations at airports. During 2012−2015, a total of 32 short-eared owls was live-captured, banded, and translocated to release sites approximately 64 to 80 km (40 to 50 miles) away from the airports. Only 1 short-eared owl (3%) was resighted and this bird was found on a different airport from where it had been translocated from. Future research in needed to evaluate the efficacy of translocating wintering short-eared owls from airport environments

Management of Wintering Short-eared Owls at Airports in the Lower Great Lakes Region

USDA Wildlife Services airport wildlife biologists have been tasked with reducing the hazards that raptors (including owls) pose to safe aircraft operations at airports and military airfields throughout the USA. A review of available wildlife strike information suggests short-eared owls (Asio flammeus) are frequently struck by aircraft during the winter months at numerous airports within the Lower Great Lakes Region of the United States. Further, this species is listed as ‘endangered’ by state fish and wildlife agencies in many states, although not at the federal level. Consequently, there is particular interest in developing non-lethal management tools for reducing the hazards posed by this species. In an effort to gain a better understanding of the efficacy of managing the hazards to aviation posed by short-eared owls, we developed methods to live-capture, mark with USGS aluminum leg bands, and translocate short-eared owls from airport environments (i.e., airfield areas) as part of the overall programs to reduce wildlife hazards to safe aircraft operations at airports. During 2012−2015, a total of 32 short-eared owls was live-captured, banded, and translocated to release sites approximately 64 to 80 km (40 to 50 miles) away from the airports. Only 1 short-eared owl (3%) was resighted and this bird was found on a different airport from where it had been translocated from. Future research in needed to evaluate the efficacy of translocating wintering short-eared owls from airport environments