Engineering topics

Beck, T.

Publications and source records attributed to Beck, T..

21 records · Page 2

DOE OSTI2020

Firm spin and parity assignments for high-lying, low-spin levels in stable Si isotopes

A natural silicon target was investigated in a nat Si(γ,γ') photon-scattering experiment with fully linearly-polarised, quasi-monochromatic γ rays in the entrance channel. The mean photon energies used were < E γ >= 9.33, 9.77, 10.17, 10.55, 10.93, and 11.37 MeV, and the relative energy spread (full width at half maximum) of the incident beam was ΔE γ /< E γ >≈ 3.5–4 %. The observed angular distributions for the ground-state decay allow firm spin and parity assignments for several levels of the stable even-even silicon isotopes.

74 ATOMIC AND MOLECULAR PHYSICS↗

NASA NTRS2013

The HERschel Inventory of the Agents of Galaxy Evolution in the Magellanic Clouds, a HERschel Open Time Key Program

We present an overview or the HERschel Inventory of The Agents of Galaxy Evolution (HERITAGE) in the Magellanic Clouds project, which is a Herschel Space Observatory open time key program. We mapped the Large Magellanic Cloud (LMC) and Small Magellanic Cloud (SMC) at 100, 160, 250, 350, and 500 micron with the Spectral and Photometric Imaging Receiver (SPIRE) and Photodetector Array Camera and Spectrometer (PACS) instruments on board Herschel using the SPIRE/PACS parallel mode. The overriding science goal of HERITAGE is to study the life cycle of matter as traced by dust in the LMC and SMC. The far-infrared and submillimeter emission is an effective tracer of the interstellar medium (ISM) dust, the most deeply embedded young stellar objects (YSOs), and the dust ejected by the most massive stars. We describe in detail the data processing, particularly for the PACS data, which required some custom steps because of the large angular extent of a single observational unit and overall the large amount of data to be processed as an ensemble. We report total global fluxes for LMC and SMC and demonstrate their agreement with measurements by prior missions. The HERITAGE maps of the LMC and SMC are dominated by the ISM dust emission and bear most resemblance to the tracers of ISM gas rather than the stellar content of the galaxies. We describe the point source extraction processing and the critetia used to establish a catalog for each waveband for the HERITAGE program. The 250 micron band is the most sensitive and the source catalogs for this band have approx. 25,000 objects for the LMC and approx. 5500 objects for the SMC. These data enable studies of ISM dust properties, submillimeter excess dust emission, dust-to-gas ratio, Class 0 YSO candidates, dusty massive evolved stars, supemova remnants (including SN1987A), H II regions, and dust evolution in the LMC and SMC. All images and catalogs are delivered to the Herschel Science Center as part of the conummity support aspects of the project. These HERITAGE images and catalogs provide an excellent basis for future research and follow up with other facilities.

AGENTS↗

NASA NTRS1992

Melt-processing of lunar ceramics

The goal of this project is to produce useful ceramics materials from lunar resources using the by products of lunar oxygen production processes. Emphasis is being placed on both fabrication of a variety of melt-processed ceramics, and on understanding the mechanical properties of these materials. Previously, glass-ceramics were formed by casting large glass monoliths and heating these to grow small crystallites. The strengths of the resulting glass-ceramics were found to vary with the inverse square root of the crystal grain size. The highest strengths (greater than 300 MPa) were obtained with the smallest crystal sizes (less than 10 microns). During the past year, the kinetics of crystallization in simulated lunar regolith were examined in an effort to optimize the microstructure and, hence, mechanical properties of glass ceramics. The use of solar energy for melt-processing of regolith was examined, and strong (greater than 630 MPa) glass fibers were successfully produced by melt-spinning in a solar furnace. A study of the mechanical properties of simulated lunar glasses was completed during the past year. As on Earth, the presence of moisture was found to weaken simulated lunar glasses, although the effects of surface flaws was shown to outweigh the effect of atmospheric moisture on the strength of lunar glasses. The effect of atmospheric moisture on the toughness was also studied. As expected, toughness was found to increase only marginally in an anhydrous atmosphere. Finally, our efforts to involve undergraduates in the research lab fluorished this past year. Four undergraduates worked on various aspects of these projects; and two of them were co-authors on papers which we published.

Fabes, B. D.↗