Heatshield material selection for advanced ballistic reentry vehicles

The Performance of staple rayon fiber and AVTEX continuous rayon fiber was evaluated as precursor materials for heatshields. The materials studied were referenced to the IRC FM5055A heatshield materials flown during the past decade. Three different arc jet facilities were used to simulate portions of the reentry environment. The IRC FM5055A and the AVTEX FM5055G, both continuous rayon fiber woven materials having the phenolic impregnant filled with carbon particles were compared. The AVTEX continuous fiber, unfilled material FM5822A was also examined to a limited extent. Test results show that the AVTEX FM5055G material provided a close substitute for the IRC FM5055A material both in terms of thermal protection and roll torque performance

Tidal currents, winds and the morphology of phytoplankton spatial structures

Chlorophyll a, nutrients and salinity distributions were studied at two spatial scales (10 cm and 0.25 to 2.5 km) in the St. Lawrence Estuary (Quebec, Canada), in order to investigate the role of tidal currents and winds in the formation and maintenance of spatial structures. Data were collected according to a synoptic sampling pattern using three sampling platforms simultaneously, and they were analyzed using analysis of variance. The sampling pattern was repeated on four occasions during July 1980.Analyses of variance indicated significant spatial heterogeneities of about the same magnitude at the two scales studied for chlorophyll and nutrients, whereas salinity showed only large–scale variability. At the kilometer scale, the frequency distribution spectra of patch length for chlorophyll showed the existence of patches of various dimensions between 0.2 and 6.0 km with a dominance of small patches (≤0.5 km). Frequency maxima were usually observed at the smaller (≤0.5 km) and larger (≥2.0 km) scales for the nutrients and only at larger (≥2.0 km) scale for salinity. The distribution spectra of patch dimensions were characteristic for each sampling experiment, depending on tidal currents and prevailing wind conditions. Estimated patch dimensions were larger parallel to the current direction than perpendicular to current direction, implying that spatial structures are elongated in the sense of the current direction. Higher winds have, first, a tendency to increase the small–scale structure of the environment by breaking up larger patches into smaller patches, before structures are completely eliminated. The implication of these findings is that different results could be obtained depending on the sampling strategy used (sampling either at anchor stations or at random, independent of current direction), which could lead to different conclusions

Subsurface chlorophyll maximum and hydrodynamics of the water column

The vertical distributions of chlorophyll a (in vivo fluorescence) and hydrodynamic properties were monitored in the Gulf of St. Lawrence (Canada) from 6 to 10 August 1983, using an automatic yo-yo profiling system and a chain of 4 current meters. Spectral analyses of temperature and in vivo fluorescence series showed that dominant frequencies were associated with internal waves (∼16 h inertial frequency). A subsurface chlorophyll maximum was continuously observed in the lower part of the 20 m thick photic layer, at a depth corresponding with maximum vertical stability of the water column, just above the nutricline.The depth of maximum phytoplankton production, at least on sunny days, corresponded to that of the subsurface chlorophyll maximum and of the maximum in vertical stability. This close association persisted despite strong horizontal advection and vertical movements caused by internal waves. Photosynthetic adjustment did occur in the water column: higher vertical stability at depth favored shade adaptation of the phytoplankton in the layer of maximum stability, as compared to the more light-adapted cells of the upper well-mixed layer. At our sampling station, vertical turbulent diffusion seemed to be high enough to replenish nutrients in the photic layer, so that they never became completely exhausted, even in surface waters. Therefore, the observed subsurface chlorophyll maximum not only resulted from environmental conditions more favorable for phytoplankton accumulation and growth, but it also involved active photosynthetic responses of phytoplankton

Moller operators and Lippmann-Schwinger equations for step-like potentials

The Moller operators and the asociated Lippman-Schwinger equations obtained from different partitionings of the Hamiltonian for a step-like potential barrier are worked out, compared and related.Comment: 15 pages, 1 inlined figure, iopart.cl

Aging Management and License Renewal

ABSTRACT Lifetime management of EDF PWR vessels and pipings are one of the main technical key points of safety and competitivness. This paper describes the EDF global approach in this field, which is applied to the nuclear fleet i.e 58 nuclear power plants, and particularly to the first 34 three loops, as far as lifetime is concerned : operating procedures and routine maintenance, special maintenance and ten years safety reassessment, engineering analysis ,based on feed back experience, scientific knowledge, degradations mechanisms, causes and consequences management, operating loadings decrease, complementary deterministic and cost-benefit analysis, fit for service justifications. anticipation strategy to prepare future, based on Non Destructive Testing investigations, ability to repair and/or to replace components, in situ expertises, ... Some examples are given : lifetime management of reactor vessels heads and bottom penetrations of pressure vessels, fit for service of cast stainless steel primary pipings, primary nozzles and auxiliary pipings special maintenance. 11

Chemical analysis of Cd12xZnxS/CdTe solar cells by plasma profiling TOFMS

Thin film CdTe photovoltaic (PV) devices and reference layers obtained by the atmospheric pressure metalorganic vapour deposition (AP-MOCVD) method have been studied for their chemical structure using plasma profiling time-of-flight-mass spectroscopy (PP-TOFMS, also called glow discharge TOFMS). Different levels of arsenic (As) dopant in CdTe films were measured by PP-TOFMS and compared to results obtained from a more conventional depth profiling method (secondary ion mass spectrometry or SIMS). This comparison showed that PPTOFMS has the sufficient sensitivity towards detection of the As dopant in CdTe and hence is suited as a rapid, low vacuum tool in controlling the large scale production of CdTe PV materials

On uniformization of Burnside's curve y2=x5−xy^2=x^5-x

Main objects of uniformization of the curve $y^2=x^5-x$ are studied: its Burnside's parametrization, corresponding Schwarz's equation, and accessory parameters. As a result we obtain the first examples of solvable Fuchsian equations on torus and exhibit number-theoretic integer $q$-series for uniformizing functions, relevant modular forms, and analytic series for holomorphic Abelian integrals. A conjecture of Whittaker for hyperelliptic curves and its hypergeometric reducibility are discussed. We also consider the conversion between Burnside's and Whittaker's uniformizations.Comment: Final version. LaTeX, 23 pages, 1 figure. The handbook for elliptic functions has been moved to arXiv:0808.348

MIXING AND RECIRCULATION CHARACTERISTICS OF GAS- LIQUID TAYLOR FLOW IN MICROREACTORS

Abstract. The effects of operating parameters (capillary and Reynolds numbers) and microchannel aspect ratio (= w/h = [1, 2.5, 4]) on the recirculation characteristics of the liquid slug in gas-liquid Taylor flow in microchannels has been investigated using 3-dimensional Volume Of Fluid numerical simulations. The results show good agreement with previous results in circular and square geometrie