Process for the leaching of AP from propellant

A method for the recovery of ammonium perchlorate from waste solid rocket propellant is described wherein shredded particles of the propellant are leached with an aqueous leach solution containing a low concentration of surface active agent while stirring the suspension

Optimal redesign study of the harm wing

The purpose of this project was to investigate the use of optimization techniques to improve the flutter margins of the HARM AGM-88A wing. The missile has four cruciform wings, located near mid-fuselage, that are actuated in pairs symmetrically and antisymmetrically to provide pitch, yaw, and roll control. The wings have a solid stainless steel forward section and a stainless steel crushed-honeycomb aft section. The wing restraint stiffness is dependent upon wing pitch amplitude and varies from a low value near neutral pitch attitude to a much higher value at off-neutral pitch attitudes, where aerodynamic loads lock out any free play in the control system. The most critical condition for flutter is the low-stiffness condition in which the wings are moved symmetrically. Although a tendency toward limit-cycle flutter is controlled in the current design by controller logic, wing redesign to improve this situation is attractive because it can be accomplished as a retrofit. In view of the exploratory nature of the study, it was decided to apply the optimization to a wing-only model, validated by comparison with results obtained by Texas Instruments (TI). Any wing designs that looked promising were to be evaluated at TI with more complicated models, including body modes. The optimization work was performed by McIntosh Structural Dynamics, Inc. (MSD) under a contract from TI

Resaca ecosystem development: colonization and succession of the macroinvertebrate community

Freshwater wetlands in the Lower Rio Grande Valley of Texas are locally known as resacas. Resacas are remnants of the Rio Grande River channel that were cut off by sedimentation and erosion of river banks. Many are maintained as permanent wetlands through intermittent water pumping from the river; and provide valuable habitat for fish, invertebrates, migratory birds and a diverse floral community in the semi-arid environment of South Texas. Three resacas in different stages of ecosystem development were studied, including one from day zero after re-flooding. The objectives were to document the colonization process of the re-flooded resaca and the macroinvertebrate community of all three sites to differentiate successional stages of the studied resacas. Two invertebrate collection methods were used, benthic corer and sweep net, in order to gather a representative sample from the entire community. Results indicated that environmental factors (i.e. water, sediment) varied little between resacas, but there were significant differences in the benthic and water column invertebrate communities among the sites studied. The most developed site exhibited the lowest diversity and richness, and the highest dominance. The intermediate site exhibited the greatest diversity and richness, and a low level of dominance. The new site fell between the other two, but was most similar to the intermediate site. Composition of the functional feeding groups did not follow expected trends within this community, but is still a useful metric for differentiating the study sites, particularly the predator and scraper taxa. The invertebrate community in the studied resacas did not follow successional trends that were expected based on other studies and the community was strongly influenced by the presence of an invasive gastropod. Based on the results of this baseline study, the invertebrate community may be useful in discriminating between successional stages of resacas

Greenbug: a hybrid web-inspector, debugger and design editor for greenstone

In this paper we present Greenbug: a hybrid web inspector, debugger and design editor developed for use with the open source digital library software Greenstone 3. Inspired by the web development tool Firebug, Greenbug is more tightly coupled with the underlying (digital library) server than that provided by Firebug; for example, Greenbug has a fine-grained knowledge of the connection between the underlying file system and the rendered web content, and also provides the ability to commit any changes made through the web interface back to the underlying file system. Moreover, because web page production in Greenstone 3 is the result of an XSLT processing pipeline, the necessarily well-formed hierarchical XML content can be manipulated into a graphical representation, which can then be manipulated directly through a visual interface supplied by Greenbug. We showcase the interface in use, provide a brief overview of implementation details, and conclude with a discussion on how the approach can be adapted to other XSLT transformation-based content management systems, such as DSpace

Invited commentary on Stewart and Davis " 'Big data' in mental health research-current status and emerging possibilities"

No abstract available

The effect of oxygen starvation on ignition phenomena in a reactive solid containing a hot-spot

In this paper, we explore the effect of oxygen supply on the conditions necessary to sustain a self-propagating front from a spherical source of heat embedded in a much larger volume of solid. The ignition characteristics for a spherical hot-spot are investigated, where the reaction is limited by oxygen, that is, reactant + oxygen ? product. It is found that over a wide range of realistic oxygen supply levels, constant heating of the solid by the hot-spot results in a self-propagating combustion front above a certain critical hot-spot power; this is clearly an important issue for industries in which hazard prevention is important. The ignition event leading to the formation of this combustion wave involves an extremely sensitive balance between the heat generated by the chemical reaction and the depletion of the reactant. As a result, for small hot-spot radii and infinite oxygen supply, not only is there a critical power above which a self-sustained combustion front is initiated there also exists a power beyond which no front is formed, before a second higher critical power is found. The plot of critical power against hot-spot radius thus takes on a Z-shape appearance. The corresponding shape for the oxygen-limited reaction is qualitatively the same when the ratio of solid thermal diffusion to oxygen mass diffusion (N) is small and we establish critical conditions for the initiation of a self-sustained combustion front in that case. As N gets larger, while still below unity, we show that the Z-shape flattens out. At still larger values of N, the supercritical behaviour becomes increasingly difficult to define and is supplanted by burning that depends more uniformly on power. In other words, the transition from slow burning to complete combustion seen at small values of N for some critical power disappears. Even higher values of N lead to less solid burning at fixed values of power

Static aeroelastic analysis and tailoring of missile control fins

A concept for enhancing the design of control fins for supersonic tactical missiles is described. The concept makes use of aeroelastic tailoring to create fin designs (for given planforms) that limit the variations in hinge moments that can occur during maneuvers involving high load factors and high angles of attack. It combines supersonic nonlinear aerodynamic load calculations with finite-element structural modeling, static and dynamic structural analysis, and optimization. The problem definition is illustrated. The fin is at least partly made up of a composite material. The layup is fixed, and the orientations of the material principal axes are allowed to vary; these are the design variables. The objective is the magnitude of the difference between the chordwise location of the center of pressure and its desired location, calculated for a given flight condition. Three types of constraints can be imposed: upper bounds on static displacements for a given set of load conditions, lower bounds on specified natural frequencies, and upper bounds on the critical flutter damping parameter at a given set of flight speeds and altitudes. The idea is to seek designs that reduce variations in hinge moments that would otherwise occur. The block diagram describes the operation of the computer program that accomplishes these tasks. There is an option for a single analysis in addition to the optimization

Correlations of the IR Luminosity and Eddington Ratio with a Hard X-ray Selected Sample of AGN

We use the SWIFT Burst Alert Telescope (BAT) sample of hard x-ray selected active galactic nuclei (AGN) with a median redshift of 0.03 and the 2MASS J and K band photometry to examine the correlation of hard x-ray emission to Eddington ratio as well as the relationship of the J and K band nuclear luminosity to the hard x-ray luminosity. The BAT sample is almost unbiased by the effects of obscuration and thus offers the first large unbiased sample for the examination of correlations between different wavelength bands. We find that the near-IR nuclear J and K band luminosity is related to the BAT (14 - 195 keV) luminosity over a factor of $10^3$ in luminosity ($L_{IR} \approx L_{BAT}^{1.25}$)and thus is unlikely to be due to dust. We also find that the Eddington ratio is proportional to the x-ray luminosity. This new result should be a strong constraint on models of the formation of the broad band continuum.Comment: accepted to ApJ