Space shuttle elevon seal panel mechanism

The orbiter elevon seal panel mechanism controls the position of fairing panels between the orbiter wing and elevon. Early mechanism designs used linkages which approximately matched the panel motion to elevon position, depending on panel deflections to maintain sealing. These linkages were refined during orbiter development to match panel motion to elevon motion more exactly, thus reducing panel deflections, loads, and weight. Changes to the adjacent cove seal resulted in the use of curved tension compression links. Mechanism temperatures up to 750 F (locally) posed difficulties in bearing lubrication. Despite the adverse effect of the many fabrication tolerances, the system successfully prevented the entry of 1200 F hot gases into the wing/elevon joint

NEC violation in mimetic cosmology revisited

In the context of Einstein gravity, if the null energy condition (NEC) is satisfied, the energy density in expanding space-times always decreases while in contracting space-times the energy density grows and the universe eventually collapses into a singularity. In particular, no non-singular bounce is possible. It is, though, an open question if this energy condition can be violated in a controlled way, i.e., without introducing pathologies, such as unstable negative-energy states or an imaginary speed of sound. In this paper, we will re-examine the claim that the recently proposed mimetic scenario can violate the NEC without pathologies. We show that mimetic cosmology is prone to gradient instabilities even in cases when the NEC is satisfied (except for trivial examples). Most interestingly, the source of the instability is always the Einstein-Hilbert term in the action. The matter stress-energy component does not contribute spatial gradient terms but instead makes the problematic curvature modes dynamical. We also show that mimetic cosmology can be understood as a singular limit of known, well-behaved theories involving higher-derivative kinetic terms and discuss ways of removing the instability.Comment: 7 page

The Rural Reconstruction Scheme

In 1971 the Commonwealth Government passed the State Grants (Rural Reconstruction) Act to provide $100m to assist rural industry to adjust itself to the severe downturn in income. The money was to be divided amongst the States to enable State Governments to make loans to farmers and pastoralists. In Western Australia the Government passed the Rural Reconstruction Scheme Act, 1971 , to implement the Scheme

Last resort loans for farmers

Several sources of finance are available to help fsrmers survive through a crisis. One source of last resort is Rural Adjustment Authority

Probate another farm cost

Death duties are too big a cost to be ignored on most farms, because most farms have substantial assets in land, stock, buildings and machinery. The saying a wise man does not lay up treasures, the more he gives to others the more he keeps for his own seems true of the types of estate planning outlined in the following article

Within The City Gates : Theme Varie

https://digitalcommons.library.umaine.edu/mmb-ps/1721/thumbnail.jp

Life history traits and population processes in marine bivalve molluscs

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution February 1998In this thesis, I investigated the how the life history characteristics of the clam Mya arenaria determine the population response to chronic contaminant exposure. To predict the potential responses of a broadcast-spawning life history such as that of M. arenaria, I surveyed the literature on a variety of bivalve species. By incorporating information on growth, survival, and reproduction into matrix population models I could evaluate the relative contributions of these factors to fitness. For broadcast-spawners, long life is an important factor enabling them to gamble on rare, large recruitment events. Another important aspect of the broadcast spawning strategy is the possibility of high variation in larval settlement from year to year. I evaluated the role that this variability plays using a stochastic matrix model, and showed that it tends to increase population growth because of the larger size of rarer, successful recruitment events. With an understanding of how the life history traits of M. arenaria might control its responses to change in the environment, I analyzed the vital rates of clams at clean and contaminated sites. The effects of contaminants measured in the lab do not necessarily predict population condition in the field. Since surviving with a long life span contributes the most to fitness in broadcast-spawning bivalves, effects on reproductive output and juvenile survival, which are strong in many lab studies, may not necessarily playa large role in field populations. The life history of this clam, with natural variation in recruitment from year to year, further reduces the population dependence on high reproductive output and larval survival. The combination of little population-level relevance of the strongest contaminant effects, and potential contaminant effects on very important clam predators, could explain why populations at contaminated sites are observed to be growing the fastest. The interaction of contaminant exposure and normal ecological processes determines the overall impact on the population.This research was supported by a Massachusetts Bay Programs grant to Judith McDowell and Damian Shea, NSF grant # DEB-9211945 to Hal Caswell, a National Defense Science and Engineering Graduate Fellowship to Bonnie Ripley, a Pew Fellowship in Conservation and the Environment to Judith McDowell, Sea Grant grant # NA46RG0470 (project # RIP-54), and by the M.I.T./W.H.O.I. Joint Program Education Office

Creation and characterization of vortex clusters in atomic Bose-Einstein condensates

We show that a moving obstacle, in the form of an elongated paddle, can create vortices that are dispersed, or induce clusters of like-signed vortices in 2D Bose-Einstein condensates. We propose new statistical measures of clustering based on Ripley's K-function which are suitable to the small size and small number of vortices in atomic condensates, which lack the huge number of length scales excited in larger classical and quantum turbulent fluid systems. The evolution and decay of clustering is analyzed using these measures. Experimentally it should prove possible to create such an obstacle by a laser beam and a moving optical mask. The theoretical techniques we present are accessible to experimentalists and extend the current methods available to induce 2D quantum turbulence in Bose-Einstein condensates.Comment: 9 pages, 9 figure

VALIDATION OF A COMMERCIALLY AVAILABLE STRAIN GAUGE AGAINST A SERIES OF KNOWN LOADS USING A SHORT TIME APPROACH

The purpose of this study was to identify the content validity and accuracy of a commercially available strain gauge (GSTRENGTH (Exsurgo Technologies, Virginia, USA), aimed at use within athletic populations. Six standardised IWF (International Weightlifting Federation) calibrated weights (5-, 25-, 50-, 100-, 200-, 250-kg) were hung from the strain gauge and raw data was collected over a five-second period and exported to a computer. A perfect relationship between the known loads and the strain gauge (r = 1.00, p\u3c0.001) was identified, although the strain gauge was found to have a small overestimation error with no fixed or proportional bias. During data collection there were non-significant, trivial-small differences between the first and last second, demonstrating minimal drift. The commercially available strain gauge was found to be valid when compared to the known loads. Further investigation of the strain gauge is required to assess the concurrent validity when compared to gold standard methods of assessment, such as force plates, in a range of test designs