Dimension of interaction dynamics

A method allowing to distinguish interacting from non-interacting systems based on available time series is proposed and investigated. Some facts concerning generalized Renyi dimensions that form the basis of our method are proved. We show that one can find the dimension of the part of the attractor of the system connected with interaction between its parts. We use our method to distinguish interacting from non-interacting systems on the examples of logistic and H\'enon maps. A classification of all possible interaction schemes is given.Comment: 15 pages, 14 (36) figures, submitted to PR

Produtividade de genótipos de soja transgênica em Porto Velho, RO.

O objetivo deste trabalho foi avaliar a produtividade de diferentes genótipos de soja no Município de Porto Velho

Evaluation of classical precipitation descriptions for γ′′(Ni3Nb−D022) in Ni-base superalloys

The growth/coarsening kinetics of γ′′(Ni3Nb−D022) precipitates have been found by numerous researchers to show an apparent correspondence with the classical (Ostwald ripening) equation outlined by Lifshitz, Slyozov and (separately) Wagner for a diffusion controlled regime. Nevertheless, a significant disparity between the actual precipitate size distribution shape and that predicted by LSW is frequently observed in the interpretation of these results, the origin of which is unclear. Analysis of the literature indicates one likely cause for this deviation from LSW for γ′′ precipitates is the “encounter” phenomenon described by Davies et al. (Acta Metall 28(2):179–189, 1980) that is associated with secondary phases comprising a high volume fraction. Consequently, the distributions of both γ′′ precipitates described in the literature (Alloy 718) and measured in this research in Alloy 625 are analysed through employing the Lifshitz–Slyozov-Encounter-Modified (LSEM) formulation (created by Davies et al.). The results of the LSEM analysis show good far better agreement than LSW with experimental distributions after the application of a necessary correction for what is termed in this research as “directional encounter”. Moreover, the activation energy for γ′′ coarsening in Alloy 625 shows conformity with literature data once the effect of heterogeneous (on dislocations) precipitate nucleation at higher temperatures is accounted for

Extreme Ultraviolet Reflective Grating Characterization and Simulationsfor the Aspera SmallSat Mission

The Aspera SmallSat mission is designed to detect and map the warm-hot gaseous component of the halos of nearby galaxies through long-slit spectroscopy of the ionized O VI emission line (103.2 nm) for the first time. The Aspera Rowland circle type spectrograph uses a toroidal grating coated with a multilayer film consisting of aluminum, lithium fluoride, and magnesium fluoride capping to optimize reflectivity in the extreme ultraviolet (EUV) waveband from 103 to 104nm. We discuss the grating characterization test setup at the University of Arizona (UA), which will validate the multilayer coating and grating efficiency in a UV vacuum chamber. We also simulate the reflectivity of the multilayer thin film coating using IMD IDL software to compare simulated results with measured reflectivity. Additionally, non-sequential ray trace simulations and 3D CAD modeling are used for verification of the test setup. Finally, the implications of the differences between the measured and simulated reflectivity and grating efficiencies are considered, including impact to the mission

Mechanical Properties and Microstructural Characterization of Aged Nickel-based Alloy 625 Weld Metal

The aim of this work was to evaluate the different phases formed during solidification and after thermal aging of the as-welded 625 nickel-based alloy, as well as the influence of microstructural changes on the mechanical properties. The experiments addressed aging temperatures of 650 and 950 A degrees C for 10, 100, and 200 hours. The samples were analyzed by electron microscopy, microanalysis, and X-ray diffraction in order to identify the secondary phases. Mechanical tests such as hardness, microhardness, and Charpy-V impact test were performed. Nondestructive ultrasonic inspection was also conducted to correlate the acquired signals with mechanical and microstructural properties. The results show that the alloy under study experienced microstructural changes when aged at 650 A degrees C. The aging was responsible by the dissolution of the Laves phase formed during the solidification and the appearance of gamma aEuro(3) phase within interdendritic region and fine carbides along the solidification grain boundaries. However, when it was aged at 950 A degrees C, the Laves phase was continuously dissolved and the excess Nb caused the precipitation of the delta-phase (Ni3Nb), which was intensified at 10 hours of aging, with subsequent dissolution for longer periods such as 200 hours. Even when subjected to significant microstructural changes, the mechanical properties, especially toughness, were not sensitive to the dissolution and/or precipitation of the secondary phases

Geochemical investigation of Pt, Pd, Rh, Ru and Au in cobalt-rich deposits from the Tuamotu Plateau (French Polynesia)

Pt, Pd, Rh, Ru and Au contents were determined in 35 samples of hydrogenous ferromanganese crusts and nodules from the Tuamotu Plateau (French Polynesia), collected during the Nodco II cruise undertaken by IFREMER during March 1987. These samples are characterized by high Pt and Rh contents. A statistical analysis including PGE and data on Mn, Fe, Ni, Co and Cu contents does not reveal significant correlations between the elements. Although meteoritical origin of PGE remains possible, the process of fractionation and deposition is probably hydrogenetic as confirmed by normalization diagrams to chondrite C1. This point of view is supported by the determination of some partition coefficients of PGE between the oxidized phase and the aqueous medium. The deposition mechanism is discussed

Anisotropy in creep properties of DS200 + Hf alloy

International audienceThe directionally solidified Ni-based superalloy DS200 + Hf is used in aero-engines and industrial gas turbines for the manufacturing of intermediate and low-pressure turbine blades. This material consists of ~ columnar grains oriented along the solidification direction and with random secondary orientations. In this study, the creep behaviour of the DS200 + Hf alloy has been investigated along longitudinal and transverse directions. The main objective was to investigate the durability of this alloy and the damage mechanisms for four different crystalline microstructures: DS200 + Hf composed of fine grains loaded longitudinally, the same alloy composed of coarse grains or fine grains, loaded transversally to the solidification direction and finally, the single crystal version, Mar-M200 + Hf, loaded along a crystallographic orientation. Creep tests were performed from 750°C up to 1100°C. Under all conditions, a pronounced decrease in the strain to failure is observed for specimens loaded along the transverse direction compared to specimens tested along longitudinal direction or single crystals. Fracture surface observations revealed that the lower creep ductility along such a loading direction results from an intergranular failure mode. Furthermore, the creep life anisotropy significantly decreases when temperature increases. Additional creep experiments under vacuum at 900°C and experiments using single crystalline specimens far away from the crystallographic orientation show a prominent damaging role of oxidation at very high temperature and a major contribution of the local crystallography at low temperatures. In addition, the grain size effect observed when testing in the transverse direction only results from the grain boundary oxidation