Symmetries and choreographies in families that bifurcate from the polygonal relative equilibrium of the <Emphasis Type="Italic">n</Emphasis>-body problem     

Renato Calleja  Eusebius Doedel  Carlos García-Azpeitia 《Celestial Mechanics and Dynamical Astronomy》2018,130(7):48

We use numerical continuation and bifurcation techniques in a boundary value setting to follow Lyapunov families of periodic orbits and subsequently bifurcating families. The Lyapunov families arise from the polygonal equilibrium of n bodies in a rotating frame of reference. When the frequency of a Lyapunov orbit and the frequency of the rotating frame have a rational relationship, then the orbit is also periodic in the inertial frame. We prove that a dense set of Lyapunov orbits, with frequencies satisfying a diophantine equation, correspond to choreographies. We present a sample of the many choreographies that we have determined numerically along the Lyapunov families and along bifurcating families, namely for the cases \(n=3\), 4, and 6–9. We also present numerical results for the case where there is a central body that affects the choreography, but that does not participate in it. Animations of the families and the choreographies can be seen at the link below.  相似文献   

Common-offset common-reflection-surface attributes estimation with differential evolution     

Tiago Barros  Renato Lopes  Rafael Krummenauer  Hervé Chauris 《Geophysical Prospecting》2019,67(8):2022-2034

Common-reflection surface is a method to describe the shape of seismic events, typically the slopes (dip) and curvature portions (traveltime). The most systematic approach to estimate the common-reflection surface traveltime attributes is to employ a sequence of single-variable search procedures, inheriting the advantage of a low computational cost, but also the disadvantage of a poor estimation quality. A search strategy where the common-reflection surface attributes are globally estimated in a single stage may yield more accurate estimates. In this paper, we propose to use the bio-inspired global optimization algorithm differential evolution to estimate all the two-dimensional common-offset common-reflection surface attributes simultaneously. The differential evolution algorithm can provide accurate estimates for the common-reflection surface traveltime attributes, with the benefit of having a small set of input parameters to be configured. We apply the differential evolution algorithm to estimate the two-dimensional common-reflection surface attributes in the synthetic Marmousi data set, contaminated by noise, and in a land field data with a small fold. By analysing the stacked and coherence sections, we could see that the differential evolution based common-offset common-reflection surface approach presented significant signal-to-noise ratio enhancement.  相似文献   

Presence of Anthropogenic Markers in Water: A Case Study of the Guaporé River Watershed,Brazil          下载免费PDF全文

Marilia Camotti Bastos  Danilo Rheinheimer dos Santos  José A. Monteiro de Castro Lima  Thibaut le Guet  Maria A. Santanna dos Santos  Renato Zanella  Elodie Aubertheau  Leslie Mondamert  Laurent Caner  Jérôme Labanowski 《洁净——土壤、空气、水》2018,46(3)

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Hidden in plain sight: How finding a lake in the Brazilian Pantanal improves understanding of wetland hydrogeomorphology     

Eder Renato Merino  Mario Luis Assine 《地球表面变化过程与地形》2020,45(2):440-458

Wetlands are permanently or seasonally flooded areas which support countless species of plants and animals. The Pantanal, in central-west Brazil is one of the largest freshwater wetlands in the world covering an area of ~150 000 km². The relationships between geomorphology, hydrology, sedimentation, and vegetation cover are critical for understanding how the landscape constrains the dynamics of wetlands. We provide a detailed study of the geomorphology and surface hydrology of the Negro River Interfan System (NRIS), in the southern Pantanal, by applying multiple approaches (i.e. remote sensing analysis, geomorphological zonation and hydrosedimentological surveys). A multitemporal analysis of Landsat imagery produced an inundation frequency map (2000–2011 period) that revealed a permanently flooded area in the central portion of the NRIS. A hidden fluvial lake was previously undetected due to the accumulation of floating mats and floating meadows of macrophytes. The Negro and Aquidauana feeder rivers exhibit remarkable differences in channel planform, water discharge, and sediment load. The Negro River presents a distributary pattern with marginal levees with decreasing elevation as it progrades into the lake and remains as a subaqueous landform conditioning the water flow downstream. The lake outflow to the Paraguay River occurs mainly by sheet flow during flood seasons and through small tributary channels during dry months. The lake's geometry is outlined by east–northeast and west–northwest straight borders, suggesting that the area is tectonically controlled. A cloud-based worldwide water surface database (1984–2015) revealed frequent channel changes within the NRIS. Recent channel avulsions in the lower course of the Negro River are noteworthy mainly because the former river channel at the confluence with the Paraguay River is no longer connected with the Negro River channel. © 2019 John Wiley & Sons, Ltd.  相似文献   

In situ experimental study of reed leaf decomposition along a full salinity gradient     

Victor Quintino  Franca Sangiorgio  Fernando Ricardo  Renato Mamede  Adília Pires  Rosa Freitas  Ana Maria Rodrigues  Alberto Basset 《Estuarine, Coastal and Shelf Science》2009

An experimental study on Phragmites australis leaf litter decomposition was conducted in the estuarine environment, Ria de Aveiro, Western Portugal, using the leaf-bag technique, with fine- (1 mm) and coarse-mesh (5 mm) bags. The leaf bags were placed in the field sites at day 0, covering a complete salinity gradient, and replicates were collected over time, at days 3 (leaching), 7, 15, 30 and 60. The biomass loss through the leaching phase, about 20% of the initial leaf mass, was independent of both the salinity and the bag mesh size. The biomass decay pattern along the salinity gradient varied through time and presented strong similarities between the two mesh sizes, with the remaining biomass always lower in the 5 mm mesh-size bags. At days 7 and 15, the lowest remaining biomass was observed at the head of the estuary, the preferential distribution area of P. australis. At day 30, the remaining biomass was higher in the marine area and diminished under a direct relationship with salinity, reaching the lowest value in the freshwater environment, with values ranging from 66% to 44% of the initial weight in 5 mm bags, and from 79% to 51% in 1 mm bags. The largest heterogeneity in the remaining biomass among the study areas positioned along the salinity gradient was found close to days 30 (5 mm) and 40 (1 mm). The overall results indicate that the relationship between leaf decay rate and salinity depends on the decay time considered (k₁₅, k₃₀ or k₆₀) and, for the later stages (k₆₀), also on the leaf-bag mesh size. This implies that the use of leaf litter decay rates as a functional indicator in transitional waters will need to take into consideration the factor location in the salinity gradient and leaf litter stage at which the decay rate is determined. The differences between the decay rates with the mesh size acted mainly at the level of the absolute k value and not at the level of the pattern along the salinity gradient. Even so, the data obtained at the mouth of the estuary, in the area closest to a fully marine environment, indicated that after the initial biomass loss through leaching, P. australis decayed either very slowly, in the 5 mm, or not at all, in the 1 mm mesh bags.  相似文献   

The role of discontinuities in the susceptibility,development, and runout of rock avalanches: a review     

Lan  Hengxing  Zhang  Yixing  Macciotta  Renato  Li  Langping  Wu  Yuming  Bao  Han  Peng  Jianbing 《Landslides》2022,19(6):1391-1404

Landslides - Rock avalanche is one of the most spectacular and catastrophic type of natural hazard phenomena. Those events typically start with a giant rock block or multiple blocks becoming...  相似文献   

Landslide longitudinal shape: a new concept for complementing landslide aspect ratio     

Li  Langping  Lan  Hengxing  Strom  Alexander  Macciotta  Renato 《Landslides》2022,19(5):1143-1163

Landslides - Aspect ratio is an elementary parameter widely adopted to characterize landslide geometry. Nevertheless, it in essence reflects an overall elongation of landslide only, and cannot...  相似文献   

Evaluation of wave model performance in the South Atlantic Ocean: a study about physical parameterization and wind forcing calibration     

Kaiser  J&#;lia  Nogueira  Izabel C. M.  Campos  Ricardo M.  Parente  Carlos E.  Martins  Renato P.  Belo  Wellington C. 《Ocean Dynamics》2022,72(2):137-150

Ocean Dynamics - This paper evaluates the performance of the spectral wave model WAVEWATCH III for the South Atlantic Ocean forced by wind inputs from the most recent reanalyses, NCEP/CFSR and...  相似文献   

Do small marinas drive habitat specific impacts? A case study from Mediterranean Sea     

Di Franco A  Graziano M  Franzitta G  Felline S  Chemello R  Milazzo M 《Marine pollution bulletin》2011,62(5):926-933

Many human activities add new structures to the marine landscape. Despite the fact that human structures cause some inevitable impacts, surprisingly little information exists on the effects of marina on natural marine assemblages. The aim of this paper is to assess habitat-specific response of benthic sessile organisms of rocky shores in relation to the presence of a small marina. Sampling was carried out at three coastal habitats (midshore, lowshore and subtidal) by means of visual censuses adopting an after-control-impact (ACI) experimental design. It appears that the marina affects the structure and composition of benthic communities of both the midshore and the lowshore. Little effect was evident on shallow subtidal assemblage structure. The results of the present study clearly show habitat-specific responses of coastal benthic assemblages to the presence of infrastructure.  相似文献   

A parameterized model for local infiltration in two-layered soils with a more permeable upper layer     

Corrado Corradini  Renato Morbidelli  Alessia Flammini  Rao S. Govindaraju 《Journal of Hydrology》2011,396(3-4):221-232

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