A numerical algorithm for endochronic plasticity and comparison with experiment

A numerical algorithm based on the finite element method of analysis of the boundary value problem in a continuum is presented, in the case where the plastic response of the material is given in the context of endochronic plasticity. The relevant constitutive equation is expressed in incremental form and plastic effects are accounted for by the method of an induced pseudo-force in the matrix equations. The results of the analysis are compared with observed values in the case of a plate with two symmetric notches and loaded longitudinally in its own plane. The agreement between theory and experiment is excellent

A direct measurement of the charge states of energetic iron emitted by the sun

The charge states of energetic iron have been measured directly for the first time in a solar particle event. In the energy interval 0.01 to 0.25 MeV per nucleon, iron is not fully stripped but has a mean ionization state of 11.6. This value is remarkably similar to the mean ionization state of iron in the quiet solar wind and suggests that the charge states were "frozen-in" at a coronal temperature of approximately 1,500,000 K

Emission of nearly stripped carbon and oxygen from the sun

Energy spectra of nearly stripped carbon and oxygen nuclei were observed during several solar particle events indicating a systematic deviation of these spectra from a simple power law. The spectra bend below 100 keV per nucleon and the degree of turn-over are highly correlated with the size of the flare, as measured by the event averaged flux of 130 to 220 keV protons. The energy spectra of helium computed for the same time periods do not show a similar feature. A large variability of the alpha/CNO ratio from event to event (from 2 to about 20 at 40 keV per nucleon) is found, and, in all cases examined, the carbon and oxygen nuclei are nearly fully stripped. These results are interpreted as evidence for storage of energetic ions in hot (T sub e is approximatey 1.5 million K) coronal regions, followed by strong adiabatic deceleration

Radiation damage and annealing in large area n+/p/p+ GaAs shallow homojunction solar cells

Annealing of radiation damage was observed for the first time in VPE-grown, 2- by 2-cm, n+/p/p+ GaAs shallow homojunction solar cells. Electrical performance of several cells was determined as a function of 1-MeV electron fluence in the range of 10 to the 13th power to 10 to the 15th power e-/sq cm and as a function of thermal annealing time at various temperatures. Degradation of normalized power output after a fluence of 10 to the 15th power 1-MeV electrons/sq cm ranged from a low of 24 to 31 percent of initial maximum power. Normalized short circuit current degradation was limited to the range from 10 to 19 percent of preirradiated values. Thermal annealing was carried out in a flowing nitrogen gas ambient, with annealing temperatures spanning the range from 125 to 200 C. Substantial recovery of short circuit current was observed at temperatures as low as 175 C. In one case improvement by as much as 10 percent of the postirradiated value was observed. The key features of these cells are their extremely thin emitter layers (approxmately 0.05 micrometers), the absence of any Al sub xGd sub 1-x As passivating window layer, and their fabrication by vapor phase epitaxy

A V-Diagram for the Design of Integrated Health Management for Unmanned Aerial Systems

Designing Integrated Vehicle Health Management (IVHM) for Unmanned Aerial Systems (UAS) is inherently complex. UAS are a system of systems (SoS) and IVHM is a product-service, thus the designer has to take into account many factors, such as: the design of the other systems of the UAS (e.g. engines, structure, communications), the split of functions between elements of the UAS, the intended operation/mission of the UAS, the cost verses benefit of monitoring a system/component/part, different techniques for monitoring the health of the UAS, optimizing the health of the fleet and not just the individual UAS, amongst others. The design of IVHM cannot sit alongside, or after, the design of UAS, but itself be integrated into the overall design to maximize IVHM’s potential. Many different methods exist to help design complex products and manage the process. One method used is the V-diagram which is based on three concepts: decomposition & definition; integration & testing; and verification & validation. This paper adapts the V-diagram so that it can be used for designing IVHM for UAS. The adapted v-diagram splits into different tracks for the different system elements of the UAS and responses to health states (decomposition and definition). These tracks are then combined into an overall IVHM provision for the UAS (integration and testing), which can be verified and validated. The stages of the adapted V-diagram can easily be aligned with the stages of the V-diagram being used to design the UAS bringing the design of the IVHM in step with the overall design process. The adapted V-diagram also allows the design IVHM for a UAS to be broken down in to smaller tasks which can be assigned to people/teams with the relevant competencies. The adapted V-diagram could also be used to design IVHM for other SoS and other vehicles or products

Solar modulation of cosmic ray intensity and solar flare events inferred from (14)C contents in dated tree rings

The delta 14C values in 42 rings of a white spruce grown in Mackenzie Delta was measured as a continuing effort of tracing the history of solar modulation of cosmic ray intensity. The delta 14C values in six rings were measured, in search of a 14C increase due to two large solar flares that occurred in 1942. The results are presented