Gallium Arsenide solar cell radiation damage experiment

Gallium arsenide (GaAs) solar cells for space applications from three different manufactures were irradiated with 10 MeV protons or 1 MeV electrons. The electrical performance of the cells was measured at several fluence levels and compared. Silicon cells were included for reference and comparison. All the GaAs cell types performed similarly throughout the testing and showed a 36 to 56 percent power areal density advantage over the silicon cells. Thinner (8-mil versus 12-mil) GaAs cells provide a significant weight reduction. The use of germanium (Ge) substrates to improve mechanical integrity can be implemented with little impact on end of life performance in a radiation environment

Dynamic instabilities of fracture under biaxial strain using a phase field model

We present a phase field model of the propagation of fracture under plane strain. This model, based on simple physical considerations, is able to accurately reproduce the different behavior of cracks (the principle of local symmetry, the Griffith and Irwin criteria, and mode-I branching). In addition, we test our model against recent experimental findings showing the presence of oscillating cracks under bi-axial load. Our model again reproduces well observed supercritical Hopf bifurcation, and is therefore the first simulation which does so

Carleman estimates and absence of embedded eigenvalues

Let L be a Schroedinger operator with potential W in L^{(n+1)/2}. We prove that there is no embedded eigenvalue. The main tool is an Lp Carleman type estimate, which builds on delicate dispersive estimates established in a previous paper. The arguments extend to variable coefficient operators with long range potentials and with gradient potentials.Comment: 26 page

Bounds on the Wilson Dirac Operator

New exact upper and lower bounds are derived on the spectrum of the square of the hermitian Wilson Dirac operator. It is hoped that the derivations and the results will be of help in the search for ways to reduce the cost of simulations using the overlap Dirac operator. The bounds also apply to the Wilson Dirac operator in odd dimensions and are therefore relevant to domain wall fermions as well.Comment: 16 pages, TeX, 3 eps figures, small corrections and improvement

Use of ERTS-1 data in identification, classification, and mapping of salt-affected soils in California

There are no author-identified significant results in this report

Modern trends in the retail ice cream store

Cover title.Includes bibliographical references

Noncompact chiral U(1) gauge theories on the lattice

A new, adiabatic phase choice is adopted for the overlap in the case of an infinite volume, noncompact abelian chiral gauge theory. This gauge choice obeys the same symmetries as the Brillouin-Wigner (BW) phase choice, and, in addition, produces a Wess-Zumino functional that is linear in the gauge variables on the lattice. As a result, there are no gauge violations on the trivial orbit in all theories, consistent and covariant anomalies are simply related and Berry's curvature now appears as a Schwinger term. The adiabatic phase choice can be further improved to produce a perfect phase choice, with a lattice Wess-Zumino functional that is just as simple as the one in continuum. When perturbative anomalies cancel, gauge invariance in the fermionic sector is fully restored. The lattice effective action describing an anomalous abelian gauge theory has an explicit form, close to one analyzed in the past in a perturbative continuum framework.Comment: 35 pages, one figure, plain TeX; minor typos corrected; to appear in PR

Large scale in-situ experiments on sealing constructions in underground disposal facilities for radioactive wastes -examples of recent BfS-and GRS-activities

Abstract: This paper shows examples of in-situ constructions and laboratory tests that have been designed and implemented by BfS und GRS in order to demonstrate the technical feasibility of special constructions for the sealing of drifts and shafts in different salt formations. Since a direct verification of the long-term functionality (for times scales envisaged in long-term safety assessments) of such constructions is often not possible, an overall understanding of the main chemical and physical processes involved needs to be developed. Such an understanding is required in order to extrapolate the evolution of a sealing system with a sufficient degree of reliability. Laboratory tests and large-scale in-situ tests are necessary and integral parts of the procedures for enhancing the process understanding. Based on a safety case, BfS has developed a robust decommissioning concept for the closure of the low-and intermediate-level waste disposal facility Morsleben (ERAM) which also takes into account the retention of radionuclides by combined effects of different sealing components. GRS has contributed to this concept with laboratory tests and modelling of the long-term behaviour of the sealing material "Salt concrete" foreseen for the sealing constructions in Morsleben. Salt concrete is based on the cement Portlandite i.e., on CaO. Furthermore GRS has also investigated the MgO based "Sorel concrete" employed by BfS for the Asse project. The chemical corrosion path and the subsequent permeability changes for both concretes have been investigated with test procedures developed in the GRS laboratory. GRS has also developed and tested in laboratory and in-situ experiments a new Self-Sealing material "Selbst Verheilender Versatz -SVV" (SVV, German for Self Sealing Backfill) which is able to achieve an instantaneous and long-lasting permeability reduction within the complex system consisting of the sealing construction and the Excavation Disturbed Zone (EDZ) upon brine intrusion. The presentation demonstrates details of the concepts and highlights results from the in-situ experiments of BfS in Morsleben and the preceding GRS laboratory and in-situ tests