Theory of intermittency applied to classical pathological cases

The classical theory of intermittency developed for return maps assumes uniform density of points reinjected from the chaotic to laminar region. Though it works fine in some model systems, there exist a number of so-called pathological cases characterized by a significant deviation of main characteristics from the values predicted on the basis of the uniform distribution. Recently, we reported on how the reinjection probability density (RPD) can be generalized. Here, we extend this methodology and apply it to different dynamical systems exhibiting anomalous type-II and type-III intermittencies. Estimation of the universal RPD is based on fitting a linear function to experimental data and requires no a priori knowledge on the dynamical model behind. We provide special fitting procedure that enables robust estimation of the RPD from relatively short data sets (dozens of points). Thus, the method is applicable for a wide variety of data sets including numerical simulations and real-life experiments. Estimated RPD enables analytic evaluation of the length of the laminar phase of intermittent behaviors. We show that the method copes well with dynamical systems exhibiting significantly different statistics reported in the literature. We also derive and classify characteristic relations between the mean laminar length and main controlling parameter in perfect agreement with data provided by numerical simulation

Exportação de biomassa e nutrientes de povoamentos de Pinus taeda L. desbastados em diferentes idades

Três povoamentos de Pinus taeda L., por ocasião do 19, 29 e 39 desbaste, com 7, 10 e 14 anos de idade, respectivamente, foram amostrados no período de junho a setembro de 1985 para determinar o peso de matéria seca e de nutrientes dos componentes da parte aérea das árvores retiradas e remanescentes e dos componentes da manta orgânica florestal (horizonte orgânico). Foram abatidas 51, 39 e 25 arvores nos povoamentos de 1°, 29 e 3° desbaste, respectivamente, abrangendo toda a variação do diâmetro a altura do peito (DAP) das árvores. Foram desenvolvidas equações de regressão em função do DAP para estimar o peso de matéria seca dos componentes vivos das árvores. Sob o povoamento de 1° desbaste, foram utilizadas 60 parcelas de 0,25 m , distribuídas ao acaso, para amostrar a manta orgânica. Em cada um dos demais povoamentos foram utilizadas 180 parcelas. Antes dos desbastes, nos povoamentos de 7, 10 e 14 anos, que apresentaram 2.062, 1.240 e 731 árvores/ha, foram estimadas 72,7, 145,9 e 183,8 t/ha de biomassa da parte aérea das árvores, respectivamente. Os pesos de nutrientes da biomassa da parte aérea oscilaram entre 413 g/ha de Cu no povoamento de 7 anos até 422,5 kg/ha de N no povoamento de 14 anos. Os pesos de biomassa da manta orgânica foram de 7,7, 19,7 e 24,3 t/ha, respectivamente nos povoamentos de 7, 10 e 14 anos. Os pesos de nutrientes da manta orgânica variaram de 34 g/ha de Cu no povoamento de 7 anos a 185 kg/ha de N no povoamento de 14 anos. As exportações de biomassa, com a retirada da madeira e casca do fuste de 38,4, 40,7 e 39,3% das árvores existentes, respectivamente no 1°, 2° e 3° desbaste, foram de 11, 36 e 49 t/ha, equivalentes a 14, 22 e 24% do peso total da biomassa estimada acima do solo mineral. Juntamente com a retirada da madeira e casca dos talhões, foram exportados desde 50 g/ha de Cu no 19 desbaste até 58,3 kg/ha de N no 39 desbaste. Os ramos e acículas, como resíduos da operação de desbaste, pesaram cerca de 7, 10 e 12 t/ha, equivalentes a 9, 7 e 5% do peso total de biomassa estimada acima do solo mineral nos povoamentos de 19, 29 e 39 desbaste, respectivamente. Estes resíduos apresentaram desde 2% de Fe até 16% de N e K, em relação ao peso total estimado acima do solo mineral. A permanência destes resíduos no sistema florestal é de grande importância para a ciclagem dos nutrientes, principalmente para a do K

Tribological Properties of High-Speed Uniform Femtosecond Laser Patterning on Stainless Steel

In this work, an analysis of the tribological performance of laser-induced periodic surface structures (LIPSS) treated X5CrNi1810 stainless steel was conducted. The approach followed by authors was to generate LIPSS-patterned circular tracks, composed of radial straight grooves with uniform angular periodicity. This permitted to measure the tribological properties in a pin-on-flat configuration, keeping fixed the orientation between the grooves and the sliding direction. A Stribeck curve was measured, as well as the consequent wear. A deep analysis of the sub-surface conditions after LIPSS generation was moreover performed using Focused Ion Beam (FIB) cross-section

Influence of defect distribution on the reducibility of CeO2-x nanoparticles

Ceria nanoparticles (NPs) are fundamental in heterogeneous catalysis because of their ability to store or release oxygen depending on the ambient conditions. Their oxygen storage capacity is strictly related to the exposed planes, crystallinity, density and distribution of defects. In this work a study of ceria NPs produced with a ligand-free, physical synthesis method is presented. The NP films were grown by a magnetron sputtering based gas aggregation source and studied by high resolution- and scanning-transmission electron microscopy and x-ray photoelectron spectroscopy. In particular, the influence of the oxidation procedure on the NP reducibility has been investigated. The different reducibility has been correlated to the exposed planes, crystallinity and density and distribution of structural defects. The results obtained in this work represent a basis to obtain cerium oxide NP with desired oxygen transport properties

Influence of size, shape and core\u2013shell interface on surface plasmon resonance in Ag and Ag@MgO nanoparticle films deposited on Si/SiOx

Ag and Ag@MgO core-shell nanoparticles (NPs) with a diameter of d = 3-10 nm were obtained by physical synthesis methods and deposited on Si with its native ultrathin oxide layer SiOx (Si/SiOx). Scanning electron microscopy and transmission electron microscopy (TEM) images of bare Ag NPs revealed the presence of small NP aggregates caused by diffusion on the surface and agglomeration. Atomic resolution TEM gave evidence of the presence of crystalline multidomains in the NPs, which were due to aggregation and multitwinning occurring during NP growth in the nanocluster source. Co-deposition of Ag NPs and Mg atoms in an oxygen atmosphere gave rise to formation of a MgO shell matrix surrounding the Ag NPs. The behaviour of the surface plasmon resonance (SPR) excitation in surface differential reflectivity (SDR) spectra with p-polarised light was investigated for bare Ag and Ag@MgO NPs. It was shown that the presence of MgO around the Ag NPs caused a red shift of the plasmon excitation, and served preserve its existence after prolonged (five months) exposure to air, realizing the possibility of technological applications in plasmonic devices. The Ag NP and Ag@MgO NP film features in the SDR spectra could be reproduced by classical electrodynamics simulations by treating the NP-containing layer as an effective Maxwell Garnett medium. The simulations gave results in agreement with the experiments when accounting for the experimentally observed aggregation

Steering the magnetic properties of Ni/NiO/CoO core-shell nanoparticle films: The role of core-shell interface versus interparticle interactions

Supported core-shell Ni/NiO/CoO nanoparticle (NP) films were obtained by deposition of preformed and mass-selected Ni NPs on a buffer layer of CoO, followed by a top CoO layer. The resulting NPs have core/shell morphology, with a McKay icosahedral Ni core and a partially crystalline CoO shell. X-ray photoelectron spectroscopy evidenced the presence of a thin NiO layer, which was shown to be between the Ni core and the CoO shell by elemental TEM mapping. CoO and NiO shells with different thickness values were obtained, allowing us to investigate the evolution of the magnetic properties of the NP assemblies as a function of the oxide shell thickness. Both exchange-coupling and magnetostatic interactions significantly contribute to the magnetic behavior of Ni/NiO/CoO NP films. After the Ni/NiO/CoO NPs are cooled in a weak magnetic field, they have blocking temperature higher than room temperature because of strong magnetostatic interactions, which support the formation of a spin-glass-like state below similar to 250 K. Exchange coupling dominates the magnetic behavior after the NPs are cooled in a strong magnetic field. The exchange bias (EB) is in the 0.17-2.35 kOe range and strongly depends on the CoO thickness (0.4-2.7 nm), showing the onset of the EB at the few-nanometer scale. The switching field distribution showed that the EB opposes the magnetization reversal from the direction along the cooling field but it does not significantly ease the opposite process. The EB depends on t(CoO) only for t(NiO) <= 0.5 nm, but when NiO is 0.7 nm thick it strongly interacts with CoO and a large increase of the EB and coercivity is observed

Influence of Edaphic and Phytosociological Attributes on Semideciduous Remnants Vegetation

Abstract Atlantic forest biome in Brazil has high biodiversity that is threated due to fragmentation and its remnants retain important residual flora that should be preserved. Studies of environmental conditions that influence species occurrence in those areas are very important to preserve them. This study characterized two remnants vegetation in the Biological Reserve, Pindorama-SP, Brazil, classified as seasonal semideciduous forest sampled in 65 plots of 400 m 2 , using soil attributes and vegetation data. Soil attributes altitude, basal area, height and number of trees with diameter at breast height (DBH) ≥ 5 cm were evaluated in the plots and non-arboreous species infestation was evaluated in a randomly drawn quadrant of 100 m 2 . The hierarchical clustering, based on soil attributes, separated plots in two major groups and five subgroups of similarity used to characterize the vegetation and the species diversity, by the Shannon Index (H&apos;) and the Pielou Equitability Coefficient (J). Soil attributes influenced endemic trees and non-arborous vegetation showing that preservation of native vegetation should consider these species relationships. Plots with higher clay percentage and higher fertility had higher infestation of non-arboreous plants as bamboo, lianas and different grasses species and had lower species diversity, basal area and height of tree species