8,410 research outputs found
Thrust vector control study for large /260 inch/ rocket motor applications
Design concepts of thrust vector control for large rocket motor application
Centaur Propellant Thermal Conditioning Study
A wicking investigation revealed that passive thermal conditioning was feasible and provided considerable weight advantage over active systems using throttled vent fluid in a Centaur D-1s launch vehicle. Experimental wicking correlations were obtained using empirical revisions to the analytical flow model. Thermal subcoolers were evaluated parametrically as a function of tank pressure and NPSP. Results showed that the RL10 category I engine was the best candidate for boost pump replacement and the option showing the lowest weight penalty employed passively cooled acquisition devices, thermal subcoolers, dry ducts between burns and pumping of subcooler coolant back into the tank. A mixing correlation was identified for sizing the thermodynamic vent system mixer. Worst case mixing requirements were determined by surveying Centaur D-1T, D-1S, IUS, and space tug vehicles. Vent system sizing was based upon worst case requirements. Thermodynamic vent system/mixer weights were determined for each vehicle
How has the Louisiana Scholarship Program Affected Students? A Comprehensive Summary of Effects after Four Years
School choice has long been a subject of robust debate. Private school vouchersâprograms providing public funds for students to attend K-12 private schoolsâtend to be the most contentious form of school choice. Over the past three years, our research team has released a series of reports examining how the LSP has affected key student and community conditions
Spectra of Nearby Galaxies Measured with a New Very Broadband Receiver
Three-millimeter-wavelength spectra of a number of nearby galaxies have been
obtained at the Five College Radio Astronomy Observatory (FCRAO) using a new,
very broadband receiver. This instrument, which we call the Redshift Search
Receiver, has an instantaneous bandwidth of 36 GHz and operates from 74 to
110.5 GHz. The receiver has been built at UMass/FCRAO to be part of the initial
instrumentation for the Large Millimeter Telescope (LMT) and is intended
primarily for determination of the redshift of distant, dust-obscured galaxies.
It is being tested on the FCRAO 14m by measuring the 3mm spectra of a number of
nearby galaxies. There are interesting differences in the chemistry of these
galaxies.Comment: published in the Proceedings of the International Astronomical Union
(2008), 4. Vol 251, pp 251-256 Cambridge University Pres
Evidence for nodal superconductivity in LaFePO
In several iron-arsenide superconductors there is strong evidence for a fully
gapped superconducting state consistent with either a conventional s-wave
symmetry or an unusual state where there the gap changes sign between
the electron and hole Fermi surface sheets. Here we report measurements of the
penetration depth in very clean samples of the related
iron-phosphide superconductor, LaFePO, at temperatures down to 100 mK.
We find that varies almost perfectly linearly with strongly
suggesting the presence of gap nodes in this compound. Taken together with
other data, this suggests the gap function may not be generic to all pnictide
superconductors
Spitzer IRS Observations of the Galactic Center: Shocked Gas in the Radio Arc Bubble
We present Spitzer IRS spectra (R ~600, 10 - 38 micron) of 38 positions in
the Galactic Center (GC), all at the same Galactic longitude and spanning
plus/minus 0.3 degrees in latitude. Our positions include the Arches Cluster,
the Arched Filaments, regions near the Quintuplet Cluster, the ``Bubble'' lying
along the same line-of-sight as the molecular cloud G0.11-0.11, and the diffuse
interstellar gas along the line-of-sight at higher Galactic latitudes. From
measurements of the [O IV], [Ne II], [Ne III], [Si II], [S III], [S IV], [Fe
II], [Fe III], and H_2 S(0), S(1), and S(2) lines we determine the gas
excitation and ionic abundance ratios. The Ne/H and S/H abundance ratios are ~
1.6 times that of the Orion Nebula. The main source of excitation is
photoionization, with the Arches Cluster ionizing the Arched Filaments and the
Quintuplet Cluster ionizing the gas nearby and at lower Galactic latitudes
including the far side of the Bubble. In addition, strong shocks ionize gas to
O^{+3} and destroy dust grains, releasing iron into the gas phase (Fe/H ~ 1.3
times 10^{-6} in the Arched Filaments and Fe/H ~ 8.8 times 10^{-6} in the
Bubble). The shock effects are particularly noticeable in the center of the
Bubble, but O is present in all positions. We suggest that the shocks
are due to the winds from the Quintuplet Cluster Wolf-Rayet stars. On the other
hand, the H_2 line ratios can be explained with multi-component models of warm
molecular gas in photodissociation regions without the need for H_2 production
in shocks.Comment: 51 pages, 17 figures To be published in the Astrophysical Journa
Research Project as Boundary Object: negotiating the conceptual design of a tool for International Development
This paper reflects on the relationship between who one designs for and what one designs in the unstructured space of designing for political change; in particular, for supporting âInternational Developmentâ with ICT. We look at an interdisciplinary research project with goals and funding, but no clearly defined beneficiary group at start, and how amorphousness contributed to impact. The reported project researched a bridging tool to connect producers with consumers across global contexts and show players in the
supply chain and their circumstances. We explore how both the nature of the research and the toolâs function became contested as work progressed. To tell this tale, we invoke
the idea of boundary objects and the value of tacking back and forth between elastic meanings of the projectâs artefacts and processes. We examine the projectâs role in India, Chile and other arenas to draw out ways that it functioned as a catalyst and how absence of committed design choices acted as an unexpected strength in reaching its goals
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