Pressure limiting propellant actuating system

A pressure limiting propellant activating system for simultaneously limiting the output force while maintaining a constant output pressure from the combustion chamber is described. The propellant actuated system includes an outer barrel, outer housing and a combustion chamber. A main piston is movable in the barrel housing when gas pressure is developed in the combustion chamber. A relief piston is concentrically mounted and fixedly movable with the main piston when gas pressure is exerted from the combustion. A relief piston has a force-activated separation mechanism for limiting the output force while simultaneously maintaining constant output pressure on the main piston from the combustion chamber

Efficient fe strategies for springback prediction – material modelling and computational aspects

Blanks of sheet metal are characterized by an intrinsic plastic anisotropic behaviour resulting from the plastic deformation during the rolling of sheets. Another type of anisotropy is elastic anisotropy which might be essential especially during elastic recovery processes during unloading after forming and springback. Thus, this paper focuses on the study of the sensitivity of the amount of springback in unconstrained bending with respect to elastic anisotropy. A finite strain constitutive model for evolving elastic and plastic anisotropy combining nonlinear isotropic and kinematic hardening is discussed. The evolution of elastic anisotropy is described by representing the Helmholtz free energy as a function of a family of evolving structure tensors. In addition, plastic anisotropy is modelled via the dependence of the yield surface on the same family of structure tensors. The constitutive equations of the model are implemented as a user material subroutine UMAT in the commercial solver ABAQUS/Standard, which is then applied to the simulation of springback in unconstrained bending

The Influence of Winter Social Behavior on the Habitat Selection and Reproductive Success of the Black-billed Magpie

This study examined the influence of winter social behavior, particularly dominance relationships, on the subsequent nesting habitat selection and reproductive success of Black-billed Magpies (Pica ~ hudsonia) on 2 areas in northern Utah. Hierarchical cluster analysis ordinated the habitats available to breeding birds and Chi-square and Bonferoni-z statistics were used to determine those habitat types the magpies seemed to prefer. Social status was determined by observing color-banded birds engaged in agonistic encounters at winter bait stations. Social dominance was evaluated by% dyads won, not by total % victories. Relationships between winter social status of magpies and their subsequent breeding habitat use and reproductive performance was tested by Kenda 11 \u27s Tau. Winter foraging flocks were comprised primarily of juvenile (1st year) birds while adults tended to remain as isolates or in pairs. Social status within flocks was correlated with age and sex; males dominated females and juvenile males dominated adult males. This was caused by differences in the social organization of adults and juveniles which created asymmetric views of winter food resources between male age classes. Breeding territories were densely packed in all habitats with a mean size of 0.5 ha. Date of clutch initiation was significantly correlated with clutch size and number of fledglings, with earlier nests more successful. Juveniles occupied marginal habitats and produced fewer offspring than adults. Within a dominance hierarchy of juvenile males, no significant differences in reproductive variables were detected except date of clutch initiation and weight of nestlings. Nestlings of dominant parents fledged earlier and were heavier than those of subordinates, which should increase post-fledging survival. This study has documented, for the first time in a free-living population, relationships between characteristics of nestlings and their future dominance status. Two characteristics, fledging date and rank (by weight) in the brood, were correlated with future winter dominance of juvenile males. The dominance status of male magpies is associated with many factors related to relative fitness, with hereditary components moderated by environmental and social factors

Insect (Arthropoda: Insecta) Composition in the Diet of Ornate Box Turtles (Terrapene ornata ornata) in Two Western Illinois Sand Prairies, with a New State Record for Cyclocephala (Coleoptera: Scarabaeidae)

A study of fecal samples collected over a two-year period from juvenile ornate box turtles (Terrapene ornata ornata Agassiz) revealed diets consisting of six orders of insects representing 19 families. Turtles were reared in captivity from eggs harvested from local, wild populations, and released at two remnant prairies. Identifiable insect fragments were found in 94% of samples in 2013 (n=33) and 96% in 2014 (n=25). Frequency of occurrence of insects in turtle feces is similar to results reported in previous studies of midwestern Terrapene species. A comparison of insect composition presented no significant difference between release sites. There is no significant difference in consumed insect species between turtles released into or outside of a fenced enclosure at the same site. Specimens of Cyclocephala longula LeConte collected during this study represent a new state record for Illinois

Self-trapping at the liquid vapor critical point

Experiments suggest that localization via self-trapping plays a central role in the behavior of equilibrated low mass particles in both liquids and in supercritical fluids. In the latter case, the behavior is dominated by the liquid-vapor critical point which is difficult to probe, both experimentally and theoretically. Here, for the first time, we present the results of path-integral computations of the characteristics of a self-trapped particle at the critical point of a Lennard-Jones fluid for a positive particle-atom scattering length. We investigate the influence of the range of the particle-atom interaction on trapping properties, and the pick-off decay rate for the case where the particle is ortho-positronium.Comment: 12 pages, 3 figures, revtex4 preprin