Development of detonation reaction engine

Reaction engine operates on the principle of a controlled condensed detonation. In this engine the gas products that are expelled from the engine to produce thrust are generated by the condensed detonation reaction. The engine is constructed of two basic sections consisting of a detonation wave generator section and a condensed detonation reaction section

Continuous detonation reaction engine

Reaction engine operates on the principles of a controlled condensed detonation rather than on the principles of gas expansion. The detonation results in reaction products that are expelled at a much higher velocity

Optical links in the angle-data assembly of the 70-meter antennas

In the precision-pointing mode the 70 meter antennas utilize an optical link provided by an autocollimator. In an effort to improve reliability and performance, commercial instruments were evaluated as replacement candidates, and upgraded versions of the existing instruments were designed and tested. The latter were selected for the Neptune encounter, but commercial instruments with digital output show promise of significant performance improvement for the post-encounter period

Some properties of a 5-parameter bivariate probability distribution

A five-parameter bivariate gamma distribution having two shape parameters, two location parameters and a correlation parameter was developed. This more general bivariate gamma distribution reduces to the known four-parameter distribution. The five-parameter distribution gives a better fit to the gust data. The statistical properties of this general bivariate gamma distribution and a hypothesis test were investigated. Although these developments have come too late in the Shuttle program to be used directly as design criteria for ascent wind gust loads, the new wind gust model has helped to explain the wind profile conditions which cause large dynamic loads. Other potential applications of the newly developed five-parameter bivariate gamma distribution are in the areas of reliability theory, signal noise, and vibration mechanics

Ranging system which compares an object reflected component of a light beam to a reference component of the light beam

A system is described for measuring the distance to an object by comparing a first component of a light pulse that is reflected off the object with a second component of the light pulse that passes along a reference path of known length, which provides great accuracy with a relatively simple and rugged design. The reference path can be changed in precise steps so that it has an equivalent length approximately equal to the path length of the light pulse component that is reflected from the object. The resulting small difference in path lengths can be precisely determined by directing the light pulse components into opposite ends of a detector formed of a material that emits a second harmonic light output at the locations where the opposite going pulses past simultaneously across one another

Effects of temperature and diet on the growth rate of year 0 oyster toadfish, Opsanus tau

Author Posting. © Marine Biological Laboratory, 2006. This article is posted here by permission of Marine Biological Laboratory for personal use, not for redistribution. The definitive version was published in Biological Bulletin 210 (2006): 64-71.The effects of temperature and diet on the growth of captive year 0 specimens of Opansus tau were examined for two consecutive year classes. The 2001 year class was raised at about 23, 26, or 29°C and provided with live brine shrimp, frozen butterfish and squid, or commercial food pellets (45% protein, 19% fat, and 3% fiber) three times per week. Maximal growth was achieved with the pellet diet, and fish raised at 29°C attained the highest mean wet weight (84.0 g ± 14.6 g SE) and fastest instantaneous relative growth rate (IRGR, 1.79% body weight/d). The 2002 year class was raised on the same pellet diet at 31.5°C and fed 3, 5, or 7 times per week. Although more frequent feedings led to significantly greater mean wet weight in the first half of the year, by month 12 there was no significant difference between the three feeding frequencies. These fish weighed approximately 68g and had an average IRGR of 1.74% body weight/d. The pellet diet during both years was correlated with high survival (> 75%).Support was provided by the Marine Models in Biological Research Program, the University of Minnesota Grant in Aid, the NASA Life Science Fellowship, the MBL Associates Fellowship, and NIH grant DC01837

Educational Leadership Preparation: What Supervisors, Candidates, And Mentors Said

The findings of this study identified practicum areas that meet the educational demands of candidates while highlighting practicum areas that need improvement. The study contributes to the knowledge base of the field by drawing upon feedback from university supervisors, school mentors and program candidates to evaluate and improve the practicum experience in the educational leadership program. Program candidates are in the best position to discuss their recent experiences of exposure to the real world. Supervisors and mentors can witness from their first hand experience how effective practicum activities work. Responses from supervisors, mentors and candidates regarding leadership practicum experiences are valuable to program developers in their future program redesign effort. Practicum experiences expose candidates to real-world school leadership experiences. Unfortunately, because of all kinds of conditional limitations, such practicum experiences can only be offered in conjunction with candidates' regular work in school. However, leadership practicum experiences can be well planned with a high collaboration of supervisors, mentors and candidates who have an invested interest in school improvement. In this study, what we learn from the differences of perceptions among supervisors, mentors and candidates is a caution to all stakeholders that we need to do a better job to prepare the next generation of school leaders. Supervisors, mentors and candidates need to form a coalition to explore other options, especially out-of-the-box strategies, to deliver a highly effective practicum program for potential educational leaders.&nbsp

Diffraction-limited CCD imaging with faint reference stars

By selecting short exposure images taken using a CCD with negligible readout noise we obtained essentially diffraction-limited 810 nm images of faint objects using nearby reference stars brighter than I=16 at a 2.56 m telescope. The FWHM of the isoplanatic patch for the technique is found to be 50 arcseconds, providing ~20% sky coverage around suitable reference stars.Comment: 4 page letter accepted for publication in Astronomy and Astrophysic

Lucky Imaging: High Angular Resolution Imaging in the Visible from the Ground

We use a Lucky Imaging system to obtain I-band images with much improved angular resolution on a ground-based 2.5m telescope. We present results from a 10-night assessment campaign on the 2.56m Nordic Optical Telescope and quantify the performance of our system in seeings better than 1.0''. In good seeing we have acquired near diffraction-limited images; in poorer seeing the angular resolution has been routinely improved by factors of 2.5-4. The system can use guide stars as faint as I=16 with full performance and its useful field of view is consistently larger than 40" diameter. The technique shows promise for a number of science programmes, both galactic (eg. binary candidates, brown dwarfs, globular cluster cores) and extragalactic (eg. quasar host galaxies, damped Lyman-alpha absorbers).Comment: 7 pages, 10 figures, submitted to A&A. For further information, see http://www.ast.cam.ac.uk/~optics/Lucky_Web_Site

Mu and Tau Neutrino Thermalization and Production in Supernovae: Processes and Timescales

We investigate the rates of production and thermalization of $\nu_\mu$ and $\nu_\tau$ neutrinos at temperatures and densities relevant to core-collapse supernovae and protoneutron stars. Included are contributions from electron scattering, electron-positron annihilation, nucleon-nucleon bremsstrahlung, and nucleon scattering. For the scattering processes, in order to incorporate the full scattering kinematics at arbitrary degeneracy, the structure function formalism developed by Reddy et al. (1998) and Burrows and Sawyer (1998) is employed. Furthermore, we derive formulae for the total and differential rates of nucleon-nucleon bremsstrahlung for arbitrary nucleon degeneracy in asymmetric matter. We find that electron scattering dominates nucleon scattering as a thermalization process at low neutrino energies ($\epsilon_\nu\lesssim 10$ MeV), but that nucleon scattering is always faster than or comparable to electron scattering above $\epsilon_\nu\simeq10$ MeV. In addition, for $\rho\gtrsim 10^{13}$ g cm$^{-3}$, $T\lesssim14$ MeV, and neutrino energies $\lesssim60$ MeV, nucleon-nucleon bremsstrahlung always dominates electron-positron annihilation as a production mechanism for $\nu_\mu$ and $\nu_\tau$ neutrinos.Comment: 29 pages, LaTeX (RevTeX), 13 figures, submitted to Phys. Rev. C. Also to be found at anonymous ftp site http://www.astrophysics.arizona.edu; cd to pub/thompso