15,492 research outputs found
Initial ionization rates in shock-heated Argon, Krypton, and Xenon
The rate of ionization behind strong shock waves in argon, krypton, and xenon, is observed by
a transverse microwave probe, over a range of electron densities low enough that atom-atom inelastic
collisions are the rate-determining mechanism. Shocks of Mach number 7.0 to 10.0 propagate
down a 2-in. sq. aluminum shock tube into ambient gases at pressures of 3.0 to 17.0 mm. Hg., heating
them abruptly to atomic temperatures of 5500°K to 9600°K. The subsequent relaxation toward
ionization equilibrium is examined in its early stages by the reflection, transmission, and phase shifts
of a 24.0 Gc/sec (1.25 cm) transverse microwave beam propagating between two rectangular horns
abreast a glass test section. The data yield effective activation energies of 11.9 ± 0.5 eV for argon,
10.4 ± 0.5 eV for krypton, and 8.6 ± 0.5 eV for xenon. These coincide, within experimental error,
with the first excitation potentials, rather than the ionization potentials of the gases, indicating that
in this range ionization proceeds via a two-step process involving the first excited electronic states
of which the excitation step is rate controlling
Visualizing Two Qubits
The notions of entanglement witnesses, separable and entangled states for two
qubits system can be visualized in three dimensions using the SLOCC equivalence
classes. This visualization preserves the duality relations between the various
sets and allows us to give ``proof by inspection'' of a non-elementary result
of the Horodeckies that for two qubits, Peres separability test is iff. We then
show that the CHSH Bell inequalities can be visualized as circles and cylinders
in the same diagram. This allows us to give a geometric proof of yet another
result of the Horodeckies, which optimizes the violation of the CHSH Bell
inequality. Finally, we give numerical evidence that, remarkably, allowing
Alice and Bob to use three rather than two measurements each, does not help
them to distinguish any new entangled SLOCC equivalence class beyond the CHSH
class.Comment: 22 pages, 5 figures. Added several reference
Entrepreneurial Experiments in Science Policy: Analizing the Human Genome Project
We re-conceptualize the role of science policy makers, envisioning and illustrating their move from being simple investors in scientific projects to entrepreneurs who create the conditions for entrepreneurial experiments and initiate them. We argue that reframing science policy around the notion of conducting entrepreneurial experiments – experiments that increase the diversity of technical, organizational and institutional arrangements in which scientific research is conducted – can provide policy makers with a wider repertoire of effective interventions. To illustrate the power of this approach, we analyze the Human Genome Project (HGP) as a set of successful, entrepreneurial experiments in organizational and institutional innovation. While not designed as such, the HGP was an experiment in funding a science project across a variety of organizational settings, including seven public and one private (Celera) research centers. We assess the major characteristics and differences between these organizational choices, using a mix of qualitative and econometric analyses to examine their impact on scientific progress. The planning and direction of the Human Genome Project show that policy makers can use the levers of entrepreneurial experimentation to transform scientific progress, much as entrepreneurs have transformed economic progress.Entrepreneurial Experiments; Science Policy; Human Genome Project
Convective heat transfer measurements from a NACA 0012 airfoil in flight and in the NASA Lewis Icing Research Tunnel
Local heat transfer coefficients were measured on a smooth and roughened NACA 0012 airfoil. Heat transfer measurements on the 0.533 m chord airfoil were made both in flight on the NASA Lewis Twin Otter Icing Research Aircraft and in the NASA Lewis Icing Research Tunnel (IRT). Roughness was obtained by the attachment of uniform 2 mm diameter hemispheres to the airfoil surface in 4 distinct patterns. Flight data were taken for the smooth and roughened airfoil at various Reynolds numbers based on chord in the range 1.24 to 2.50 x 10(exp 6) and at various angles of attack up to 4 deg. During these flight tests, the free stream velocity turbulence intensity was found to be very low (less than 0.1 percent). Wind tunnel data were acquired in the Reynolds number range 1.20 to 4.25 x 10(exp 6) and at angles of attack from -4 to 8 deg. The turbulence intensity in the IRT was 0.5 to 0.7 percent with the cloud generating sprays off. A direct comparison was made between the results obtained in flight and in the IRT. The higher level of turbulence in the IRT vs. flight had little effect on the heat transfer for the lower Reynolds numbers but caused a moderate increase in heat transfer at the high Reynolds numbers. Roughness generally increased the heat transfer
Comparative Analysis of Two Cryogenic Force Balance Calibration Systems
Cryogenic wind-tunnel facilities face unique challenges in the calibration and operation of various measurement systems and instrumentation. Instruments that are subjected to the cryogenic conditions of the test plenum require careful design and calibration procedures to maintain instrument performance. NASAs National Transonic Facility (NTF) and the European Transonic Windtunnel (ETW) are two cryogenic wind-tunnel facilities, each with the ability to calibrate force measurement systems (FMS) at cryogenic conditions. These facilities have different methodologies and processes for calibrating these systems. This paper discusses differences in the methodologies and processes and compares the results of two separate cryogenic calibrations of the NTF-118A force balance that were completed at both wind-tunnel facilities
Measurement of local convective heat transfer coefficients from a smooth and roughened NACA-0012 airfoil: Flight test data
Wind tunnels typically have higher free stream turbulence levels than are found in flight. Turbulence intensity was measured to be 0.5 percent in the NASA Lewis Icing Research Tunnel (IRT) with the cloud making sprays off and around 2 percent with cloud making equipment on. Turbulence intensity for flight conditions was found to be too low to make meaningful measurements for smooth air. This difference between free stream and wing tunnel conditions has raised questions as to the validity of results obtained in the IRT. One objective of these tests was to determine the effect of free stream turbulence on convective heat transfer for the NASA Lewis LEWICE ice growth prediction code. These tests provide in-flight heat transfer data for a NASA-0012 airfoil with a 533 cm chord. Future tests will measure heat transfer data from the same airfoil in the Lewis Icing Research Tunnel. Roughness was obtained by the attachment of small, 2 mm diameter hemispheres of uniform size to the airfoil in three different patterns. Heat transfer measurements were recorded in flight on the NASA Lewis Twin Otter Icing Research Aircraft. Measurements were taken for the smooth and roughened surfaces at various aircraft speeds and angles of attack up to four degrees. Results are presented as Frossling number versus position on the airfoil for various roughnesses and angles of attack
Method for improved prediction of bone fracture risk using bone mineral density in structural analysis
A non-invasive in-vivo method of analyzing a bone for fracture risk includes obtaining data from the bone such as by computed tomography or projection imaging which data represents a measure of bone material characteristics such as bone mineral density. The distribution of the bone material characteristics is used to generate a finite element method (FEM) mesh from which load capability of the bone can be determined. In determining load capability, the bone is mathematically compressed, and stress, strain force, force/area versus bone material characteristics are determined
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