Inhibited Shaped Charge Launcher Testing of Spacecraft Shield Designs

This report describes a test program in which several orbital debris shield designs were impact tested using the inhibited shaped charge launcher facility at Southwest Research Institute. This facility enables researchers to study the impact of one-gram aluminum projectiles on various shielding designs at velocities above 11 km/s. A total of twenty tests were conducted on targets provided by NASA-MSFC. This report discusses in detail the shield design, the projectile parameters and the test configuration used for each test. A brief discussion of the target damage is provided, as the detailed analysis of the target response will be done by NASA-MSFC

Rubber friction on wet and dry road surfaces: the sealing effect

Rubber friction on wet rough substrates at low velocities is typically 20-30% smaller than for the corresponding dry surfaces. We show that this cannot be due to hydrodynamics and propose a novel explanation based on a sealing effect exerted by rubber on substrate "pools" filled with water. Water effectively smoothens the substrate, reducing the major friction contribution due to induced viscoelastic deformations of the rubber by surface asperities. The theory is illustrated with applications related to tire-road friction.Comment: Format Revtex 4; 8 pages, 11 figures (no color); Published on Phys. Rev. B (http://link.aps.org/abstract/PRB/v71/e035428); previous work on the same topic: cond-mat/041204

Rubber friction on smooth surfaces

We study the sliding friction for viscoelastic solids, e.g., rubber, on hard flat substrate surfaces. We consider first the fluctuating shear stress inside a viscoelastic solid which results from the thermal motion of the atoms or molecules in the solid. At the nanoscale the thermal fluctuations are very strong and give rise to stress fluctuations in the MPa-range, which is similar to the depinning stresses which typically occur at solid-rubber interfaces, indicating the crucial importance of thermal fluctuations for rubber friction on smooth surfaces. We develop a detailed model which takes into account the influence of thermal fluctuations on the depinning of small contact patches (stress domains) at the rubber-substrate interface. The theory predicts that the velocity dependence of the macroscopic shear stress has a bell-shaped f orm, and that the low-velocity side exhibits the same temperature dependence as the bulk viscoelastic modulus, in qualitative agreement with experimental data. Finally, we discuss the influence of small-amplitude substrate roughness on rubber sliding friction.Comment: 14 pages, 16 figure

Reachability and error diagnosis in LR(1) automata

National audienceGiven an LR(1) automaton, what are the states in which an error can be detected? For each such " error state " , what is a minimal input sentence that causes an error in this state? We propose an algorithm that answers these questions. Such an algorithm allows building a collection of pairs of an erroneous input sentence and a diagnostic message, ensuring that this collection covers every error state, and maintaining this property as the grammar evolves. We report on an application of this technique to the CompCert ISO C99 parser, and discuss its strengths and limitations

Reachability and Error Diagnosis in LR(1) Parsers

International audienceGiven an LR(1) automaton, what are the states in which an error can be detected? For each such " error state " , what is a minimal input sentence that causes an error in this state? We propose an algorithm that answers these questions. This allows building a collection of pairs of an erroneous input sentence and a (handwritten) diagnostic message, ensuring that this collection covers every error state, and maintaining this property as the grammar evolves. We report on an application of this technique to the CompCert ISO C99 parser, and discuss its strengths and limitations

Epífitos vasculares predominantes em zonas ecológicas de forófitos, Santa Catarina, Brasil.

Espécies epifíticas apresentam formas, dimensões e biomassa distintas e colonizam os forófitos em regime temporário ou permanente. O presente trabalho teve como objetivo avaliar a distribuição de epífitos vasculares de biomassa visualmente dominante nas zonas ecológicas dos forófitos (fuste, copa interna e copa externa) da Floresta Ombrófila Densa de Santa Catarina. Os estudos foram realizados em 13 unidades amostrais, no interior das quais foram selecionados oito forófitos. Para a coleta dos dados, foi empregada a técnica de arvorismo e observação a partir do solo. De modo geral, as espécies registradas puderam ser classificadas como holoepífitos característicos e facultativos, e hemiepífitos primários e secundários. A família Bromeliaceae destacou-se dentre as demais nas três zonas ecológicas dos forófitos, reunindo as espécies com maiores biomassas. Relacionando as categorias ecológicas, os holoepífitos característicos, como bromeliáceas e orquidáceas, concentraram-se na região da copa e os hemiepífitos, como as aráceas Philodendron loefgrenii e Philodendron appendiculatum, foram encontradas geralmente na região do fuste.Edição especial: II Seminário sobre Inventário Florestal