Design and fabrication of a boron reinforced intertank skirt

Analytical and experimental studies were performed to evaluate the structural efficiency of a boron reinforced shell, where the medium of reinforcement consists of hollow aluminum extrusions infiltrated with boron epoxy. Studies were completed for the design of a one-half scale minimum weight shell using boron reinforced stringers and boron reinforced rings. Parametric and iterative studies were completed for the design of minimum weight stringers, rings, shells without rings and shells with rings. Computer studies were completed for the final evaluation of a minimum weight shell using highly buckled minimum gage skin. The detail design is described of a practical minimum weight test shell which demonstrates a weight savings of 30% as compared to an all aluminum longitudinal stiffened shell. Sub-element tests were conducted on representative segments of the compression surface at maximum stress and also on segments of the load transfer joint. A 10 foot long, 77 inch diameter shell was fabricated from the design and delivered for further testing

Development of lightweight aluminum compression panels reinforced by boron-epoxy infiltrated extrusions

Analytical and experimental studies were performed to evaluate the structural efficiencies afforded by the selective reinforcement of conventional aluminum compression panels with unidirectional boron epoxy composite materials. A unique approach for selective reinforcement was utilized called boron/epoxy infiltration. This technique uses extruded metal sections with preformed hollow voids into which unidirectional boron filaments are drawn and subsequently infiltrated with resin to form an integral part. Simplified analytical models were developed to investigate the behavior of stiffener webs with reinforced flanges. Theoretical results are presented demonstrating the effects of transverse shear, of the reinforcement, flange eccentricity and torsional stiffness in such construction. A series of 55 tests were conducted on boron-infiltrated rods and extruded structural sections

Gas Kinematics and Excitation in the Filamentary IRDC G035.39-00.33

Some theories of dense molecular cloud formation involve dynamical environments driven by converging atomic flows or collisions between preexisting molecular clouds. The determination of the dynamics and physical conditions of the gas in clouds at the early stages of their evolution is essential to establish the dynamical imprints of such collisions, and to infer the processes involved in their formation. We present multi-transition 13CO and C18O maps toward the IRDC G035.39-00.33, believed to be at the earliest stages of evolution. The 13CO and C18O gas is distributed in three filaments (Filaments 1, 2 and 3), where the most massive cores are preferentially found at the intersecting regions between them. The filaments have a similar kinematic structure with smooth velocity gradients of ~0.4-0.8 km s-1 pc-1. Several scenarios are proposed to explain these gradients, including cloud rotation, gas accretion along the filaments, global gravitational collapse, and unresolved sub-filament structures. These results are complemented by HCO+, HNC, H13CO+ and HN13C single-pointing data to search for gas infall signatures. The 13CO and C18O gas motions are supersonic across G035.39-00.33, with the emission showing broader linewidths toward the edges of the IRDC. This could be due to energy dissipation at the densest regions in the cloud. The average H2 densities are ~5000-7000 cm-3, with Filaments 2 and 3 being denser and more massive than Filament 1. The C18O data unveils three regions with high CO depletion factors (f_D~5-12), similar to those found in massive starless cores.Comment: 20 pages, 14 figures, 6 tables, accepted for publication in MNRA

Palaeoecological Implications of Archaeological Seal Bone Assemblages: Case Studies from Labrador and Baffin Island

In recent years, increasing scientific attention has been paid to sea mammals as biological indicators of Arctic environmental change. The usefulness of animals such as ringed seal (Phoca hispida), harp seal (Phoca groenlandica), bearded seal (Erignathus barbatus), and harbour seal (Phoca vitulina) as indicator species is due to the close relationship of their range, reproductive cycles, and life histories to sea ice. The behaviour and distribution of these species correlate with ice conditions in the areas where the animals are encountered. The proportions of seal species represented in archaeological deposits may therefore reflect, at least in part, environmental conditions characterizing past seascapes. This paper examines zooarchaeological data from several Thule and historic Inuit archaeological sites in Baffin Island and Labrador, sites occupied during the last 700 years, to determine whether regional relationships can be demonstrated between subsistence economies, seal populations, and sea ice conditions. Ratios of ringed seal, harbour seal, bearded seal, and walrus (Odobenus rosmarus) bone frequencies from several archaeological sites are analyzed and discussed in light of new high-resolution proxy sea ice and regional palaeoenvironmental data. This exploratory study suggests that characteristics in seal species composition reflected in these assemblages can, in some circumstances, be correlated with recent sea ice reconstructions. However, a regional comparison of a larger number of more precisely dated archaeological sites is required for a full examination of these relationships. Au cours des dernières années, on a porté de plus en plus d'attention scientifique aux mammifères marins en tant qu'indicateurs biologiques du changement global dans l'Arctique. L'utilité d'animaux tels que le phoque annelé (Phoca hispida), le phoque du Groenland (Phoca groenlandica), le phoque barbu (Erignathus barbatus) et le phoque commun (Phoca vitulina) comme espèces indicatrices est due au rapport étroit que leurs aires de distribution, leurs cycles de reproduction et leurs cycles de vie ont avec la glace marine. Le comportement et la distribution de ces espèces sont corrélés avec les conditions de la glace dans les zones où l'on rencontre ces animaux. Les proportions des espèces de phoques qui se trouvent dans les dépôts archéologiques pourraient donc refléter, du moins partiellement, les conditions environnementales qui caractérisaient les paysages marins du passé. Cet article se penche sur les données zooarchéologiques provenant de plusieurs sites archéologiques Thulé et inuits dans l'île Baffin et le Labrador, sites occupés au cours des 700 dernières années, pour déterminer si l'on peut démontrer l'existence de rapports régionaux entre les économies de subsistance, les populations de phoques et les conditions de glace marine. Des taux de fréquence d'os de phoque annelé, de phoque commun, de phoque barbu et de morse provenant de plusieurs sites archéologiques font l'objet d'une analyse et d'une discussion à la lumière de nouvelles données indirectes à haute résolution sur la glace marine et sur le paléoenvironnement régional. Cette étude préliminaire suggère que les caractéristiques présentes dans la composition des espèces de phoques reflétée dans ces assemblages peuvent, dans certaines conditions, être corrélées aux reconstructions récentes de la glace marine. Une comparaison régionale d'un plus grand nombre de sites archéologiques datés de façon plus précise est toutefois nécessaire pour un examen exhaustif de ces rapports.

Palaeoecological Implications of Archaeological Seal Bone Assemblages: Case Studies from Labrador and Baffin Island

In recent years, increasing scientific attention has been paid to sea mammals as biological indicators of Arctic environmental change. The usefulness of animals such as ringed seal (Phoca hispida), harp seal (Phoca groenlandica), bearded seal (Erignathus barbatus), and harbour seal (Phoca vitulina) as indicator species is due to the close relationship of their range, reproductive cycles, and life histories to sea ice. The behaviour and distribution of these species correlate with ice conditions in the areas where the animals are encountered. The proportions of seal species represented in archaeological deposits may therefore reflect, at least in part, environmental conditions characterizing past seascapes. This paper examines zooarchaeological data from several Thule and historic Inuit archaeological sites in Baffin Island and Labrador, sites occupied during the last 700 years, to determine whether regional relationships can be demonstrated between subsistence economies, seal populations, and sea ice conditions. Ratios of ringed seal, harbour seal, bearded seal, and walrus (Odobenus rosmarus) bone frequencies from several archaeological sites are analyzed and discussed in light of new high-resolution proxy sea ice and regional palaeoenvironmental data. This exploratory study suggests that characteristics in seal species composition reflected in these assemblages can, in some circumstances, be correlated with recent sea ice reconstructions. However, a regional comparison of a larger number of more precisely dated archaeological sites is required for a full examination of these relationships. Au cours des dernières années, on a porté de plus en plus d'attention scientifique aux mammifères marins en tant qu'indicateurs biologiques du changement global dans l'Arctique. L'utilité d'animaux tels que le phoque annelé (Phoca hispida), le phoque du Groenland (Phoca groenlandica), le phoque barbu (Erignathus barbatus) et le phoque commun (Phoca vitulina) comme espèces indicatrices est due au rapport étroit que leurs aires de distribution, leurs cycles de reproduction et leurs cycles de vie ont avec la glace marine. Le comportement et la distribution de ces espèces sont corrélés avec les conditions de la glace dans les zones où l'on rencontre ces animaux. Les proportions des espèces de phoques qui se trouvent dans les dépôts archéologiques pourraient donc refléter, du moins partiellement, les conditions environnementales qui caractérisaient les paysages marins du passé. Cet article se penche sur les données zooarchéologiques provenant de plusieurs sites archéologiques Thulé et inuits dans l'île Baffin et le Labrador, sites occupés au cours des 700 dernières années, pour déterminer si l'on peut démontrer l'existence de rapports régionaux entre les économies de subsistance, les populations de phoques et les conditions de glace marine. Des taux de fréquence d'os de phoque annelé, de phoque commun, de phoque barbu et de morse provenant de plusieurs sites archéologiques font l'objet d'une analyse et d'une discussion à la lumière de nouvelles données indirectes à haute résolution sur la glace marine et sur le paléoenvironnement régional. Cette étude préliminaire suggère que les caractéristiques présentes dans la composition des espèces de phoques reflétée dans ces assemblages peuvent, dans certaines conditions, être corrélées aux reconstructions récentes de la glace marine. Une comparaison régionale d'un plus grand nombre de sites archéologiques datés de façon plus précise est toutefois nécessaire pour un examen exhaustif de ces rapports.

Meshfree finite differences for vector Poisson and pressure Poisson equations with electric boundary conditions

We demonstrate how meshfree finite difference methods can be applied to solve vector Poisson problems with electric boundary conditions. In these, the tangential velocity and the incompressibility of the vector field are prescribed at the boundary. Even on irregular domains with only convex corners, canonical nodal-based finite elements may converge to the wrong solution due to a version of the Babuska paradox. In turn, straightforward meshfree finite differences converge to the true solution, and even high-order accuracy can be achieved in a simple fashion. The methodology is then extended to a specific pressure Poisson equation reformulation of the Navier-Stokes equations that possesses the same type of boundary conditions. The resulting numerical approach is second order accurate and allows for a simple switching between an explicit and implicit treatment of the viscosity terms.Comment: 19 pages, 7 figure

Laser Applications

Contains research objectives and reports on five research projects.U. S. Air Force - Office of Scientific Research(Contract F44620-71-C-0051)Joint Services Electronics Programs (U. S. Army, U. S. Navy, and U. S. Air Force) under Contract DAAB07-71-C-0300Naval Air Systems Comman

Looking back at superfluid helium

A few years after the discovery of Bose Einstein condensation in several gases, it is interesting to look back at some properties of superfluid helium. After a short historical review, I comment shortly on boiling and evaporation, then on the role of rotons and vortices in the existence of a critical velocity in superfluid helium. I finally discuss the existence of a condensate in a liquid with strong interactions, and the pressure variation of its superfluid transition temperature.Comment: Conference "Bose Einstein Condensation", Institut henri Poincare, Paris, 29 march 200