Three-body problem, its Lagrangian points and how to exploit them using an alternative transfer to L4 and L5

An alternative transfer strategy to send spacecraft to stable orbits around the Lagrangian equilibrium points L4 and L5 based in trajectories derived from the periodic orbits around L1 is presented in this work. The trajectories derived, called Trajectories G, are described and studied in terms of the initial generation requirements and their energy variations relative to the Earth through the passage by the lunar sphere of influence. Missions for insertion of spacecraft in elliptic orbits around L4 and L5 are analysed considering the restricted three-body problem Earth–Moon-particle and the results are discussed starting from the thrust, time of flight and energy variation relative to the Earth.     

How do management alternatives of fast-growing forests affect water quantity and quality in southeastern Brazil? Insights from a paired catchment experiment

Fast-growing forest plantations have been expanding in Brazil in the last 50 years, which reach productivities by over 40 m³ ha⁻¹ year⁻¹ in reduced rotation between 5 and 15 years. In the 1990s, environmental warnings about these plantations guided research projects seeking to understand their effects on water and propose forest management actions to minimize them. The assessment of forest management effects on water resources is conducted by long-term experiments in paired catchments. In this paper we present results of some studies conducted at the hydrological monitoring centre of Itatinga Experimental Forest Station, of the University of São Paulo, where hydrological monitoring began in 1987, and currently include three catchments (83–98 ha) under different forest management regimes: short-rotation Eucalyptus plantation, long-term forest plantation mosaic and native forest restoration. Results show that at similar conditions observed at study area including deep soils and good natural water regulation, hydrological effects vary according to the forest management regime adopted, increasing water consumption and making the flow regime vulnerable to intra- and inter-annual seasonality. Regarding water quality, weekly sampling results showed suspended sediments and nitrate concentrations below water quality thresholds criteria by silvicultural operations, and the effects were transient but higher concentrations of nutrients were observed in intensive management regime. In the study area, reducing the management intensity of forest plantation by increasing the rotation time, adopting forest age mosaic and avoiding the coppice technique are alternative choices that reduced water use and increased flow regulation. Different adopted forest management schemes directly affected water use, showing that in water-deficit tropical regions, management regime of fast-growing forest plantations controls water availability.     

Near‐bed shear stress,turbulence production and dissipation in a shallow and narrow tidal channel

Near‐bed, highly resolved velocity profiles were measured in the lower 0.03 m of the water column using acoustic Doppler profiling velocimeters in narrow tidal channels in a salt marsh. The bed shear stress was estimated from the velocity profiles using three methods: the log‐law, Reynolds stress, and shear stress derived from the turbulent kinetic energy (TKE). Bed shear stresses were largest during ebbing tide, while near‐bed velocities were larger during flooding tide. The Reynolds stress and TKE method gave similar results, while the log‐law method resulted in smaller bed shear stress values during ebbing tide. Shear stresses and turbulent kinetic energy followed a similar trend with the largest peaks during ebbing tide. The maximum turbulent kinetic energy was on the order of 1 × 10^{? 2} m²/s². The fluid shear stress during flooding tide was approximately 30% of the fluid shear stress during ebbing tide. The maximum TKE‐derived shear stress was 0.7 N/m² and 2.7 N/m² during flooding and ebbing tide, respectively, and occurred around 0.02 m above the bed. Turbulence dissipation was estimated using the frequency spectrum and structure function methods. Turbulence dissipation estimates from both methods were maximum near the bed (~0.01 m). Both the structure function and the frequency spectrum methods resulted in maximum dissipation estimates on the order of 4 × 10^{? 3} m²/s³. Turbulence production exceeded turbulence dissipation at every phase of the tide, suggesting that advection and vertical diffusion are not negligible. However, turbulence production and dissipation were within a factor of 2 for 77% of the estimates. The turbulence production and dissipation decreased quickly away from the bed, suggesting that measurements higher in the water column cannot be translated directly to turbulence production and dissipation estimates near the bed. Copyright © 2015 John Wiley & Sons, Ltd.     

Improving the determination of reservoir capacities for drought control

Reliable methods of determining reservoir capacities are becoming more and more necessary to improve the planning and management of water resources. Due to its easy use and solid technical and scientific basis, the Reservoir Operation Study has been widely utilized by engineers. However, this method is limited by its strong dependence on the available database. This study was undertaken to propose potential modifications to the Reservoir Operation Study to overcome its problems, namely the strong dependence upon the first year of the time series and inability of associating the reservoir storage capacity with a frequency (return period). To make the reservoir capacity independent from the first year of the time series, we created (N ? 1) synthetic series of streamflows (N = the number of years in the time series) and applied the Reservoir Operation Study method to each one. To associate the reservoir capacity with a frequency factor (return period), we applied a Gumbel distribution to the reservoir capacity estimated from each one of the synthetic series. For β-values (proportion of the average streamflow to be regulated) greater than or equal to 0.75, the proposed method efficiently overcame the aforementioned limitation regarding the method’s dependence on the database. The association of storage capacities with return periods greater than the length of the time series, which is presented in this work, also considerably improves the Reservoir Operation Study method.     

A new model for flow in shale-gas reservoirs including natural and hydraulic fractures

In this work, we construct a new coupled Multiscale/Discrete Fracture Model for compressible flow in a multiporosity shale gas reservoir containing networks of natural and hydraulic fractures. The geological formation is characterized by four distinct length scales and levels of porosity. The window of observation of the finest (nanoscale) portraits the nanopores within organic matter containing adsorbed gas. At the microscale, the medium is formed by two solid phases: organic, composed by kerogen aggregates, and inorganic (clay, quartz, calcite). Such phases are separated by the network of partially-saturated interparticle pores where microscopic free gas flow influenced by Knudsen effects along with gas diffusion in the immobile water phase occur simultaneously. The upscaling of the local flow to the mesoscale gives rise to a nonlinear homogenized pressure equation in the shale matrix which lies adjacent to the system of natural fractures. Homogenization of the coupled matrix/preexisting fractures to the macroscale leads to a microstructural model of dual porosity type. Such homogenized model is subsequently coupled with the hydrodynamics in the network of induced fractures which, in the context of the discrete fracture modeling, are treated as (n ? 1), (n = 2, 3) lower dimensional objects. In order to handle numerically the nonlinear interaction between the different flow equations, we adopt a superposition argument, firstly proposed by Arbogast (1996), in each iteration of a fixed-point algorithm. The resultant governing equations are discretized by the finite element method and numerical simulations of gas production in stratified arrangements of the fracture networks are presented to illustrate the potential of the multiscale approach.     

Structures associated with inversion of the Donbas Foldbelt (Ukraine and Russia)

The Donbas Foldbelt is part of the Prypiat–Dnieper–Donets intracratonic rift basin (Belarus–Ukraine–southern Russia) that developed in Late Devonian times and was reactivated in Early Carboniferous. To the southeast, the Donbas Foldbelt joins the contiguous, deformed Karpinsky Swell. Basin “inversions” led first to the uplift of the Palaeozoic series (mainly Carboniferous but also syn-rift Devonian strata in the southwesternmost part of the Donbas Foldbelt, which are deeply buried in the other parts of the rift system), and later to the formation of the fold-and-thrust belt. The general structural trend of the Donbas Foldbelt, formed mainly during rifting, is WNW–ESE. This is the strike of the main rift-related fault zones and also of the close to tight “Main Anticline” of the Donbas Foldbelt that developed along the previous rift axis. The Main Anticline is structurally unique in the Donbas Foldbelt and its formation was initiated in Permian times, during a period of (trans) tensional reactivation, during which active salt movements occurred. A relief inversion of the basin also took place at this time with a pronounced uplift of the southern margin of the basin and the adjacent Ukrainian Shield. Subsequently, Cimmerian and Alpine phases of tectonic inversion of the Donbas Foldbelt led to the development of flat and shallow thrusts commonly associated with folds into the basin. A fan-shaped deformation pattern is recognised in the field, with south-to southeast-vergent compressive structures, south of the Main Anticline, and north- to northwest-vergent ones, north of it. These compressive structures are clearly superimposed onto the WNW–ESE structural grain of the initial rift basin. Shortening structures that characterise the tectonic inversion of the basin are (regionally) orientated NW–SE and N–S. Because of the obliquity of the compressive trends relative to the WNW–ESE strike of inherited structures (major preexisting normal faults and the Main Anticline), in addition to reverse displacements, right lateral movements occurred along the main boundary fault zones and along the faulted hinge of the Main Anticline. The existence of preexisting structures is also thought to be responsible for local deviations in contractional trends (that are E–W in the southwesternmost part of the basin).     

Geomorphological evidence of the influence of pre-volcanic basement structure on emplacement and deformation of volcanic edifices at the Cofre de Perote–Pico de Orizaba chain and implications for avalanche generation

Pre-volcanic structure of the basement influences volcanism distribution and avalanche generation in volcanic edifices. Therefore, systematic studies of basement structure below volcanic chains are necessary to understand the deformation effects observed in the surface and vice versa. Based on a compilation of pre-existing data, interpretation of aerial photographs and satellite images, and a collection of structural data we analyzed morphological and structural features of the Cofre de Perote–Pico de Orizaba (CP–PO) volcanic chain and its basement. We have identified three sets of regional lineaments that are related to basement trends. (1) NW 55° SE fractures are parallel to anticline folds observed in Cretaceous rocks that originated during Laramide shortening. These folds present an abrupt morphology observed only in the eastern flank but that is likely to continue below the volcanic chain. (2) NE 55° SW fractures are parallel to normal faults at the basement. We infer that these basement faults confine the CP–PO chain within a stepped graben with a total normal displacement of about 400 m. These faults have been active through time since they have affected volcanic deposits and induced the emplacement of monogenetic vents. Notably, lineaments of monogenetic vents concentrate where the basement is relatively shallow. (3) Another set of faults, oriented N–S, has been observed affecting the scarce basement outcrops at the western flank of the chain covered by lacustrine deposits. Lineaments measured in the volcanic edifice of Pico de Orizaba correlate with the regional trends.In particular, the NE 55° SW alignment of monogenetic vents and fractures at Pico de Orizaba suggest that the same dike trend exists within the volcanic edifice. A normal fault with similar orientation was documented at the NE continuation of an alignment crossing the volcanic edifice along the Jamapa canyon. In the absence of magmatic activity related to collapses, the displacement of NE 55° SW faults represents a potential triggering mechanism for generating avalanches at Pico de Orizaba volcano. Instability is enhanced by the presence of N–S trending fractures crossing the entire volcanic edifice and E–W fractures affecting only the present day cone. We conclude that mechanical instability of the volcanic chain is influenced by the basement structure heterogeneity, but further detailed studies are necessary at individual volcanoes to evaluate their effects on volcano deformation.     

Organo-colloidal control on major- and trace-element partitioning in shallow groundwaters: Confronting ultrafiltration and modelling

Ultrafiltration experiments using new small ultracentifugal filter devices were performed at different pore size cut-offs to allow the study of organo-colloidal control on metal partitioning in water samples. Two shallow, circumneutral pH waters from the Mercy site wetland (western France) were sampled: one dissolved organic carbon (DOC)- and Fe-rich and a second DOC-rich and Fe-poor. Major- and trace-element cations and DOC concentrations were analysed and data treated using an ascendant hierarchical classification method. This reveals the presence of three groups: (i) a “truly” dissolved group (Na, K, Rb, Ca, Mg, Ba, Sr, Si and Ni); (ii) an inorganic colloidal group carrying Fe, Al and Th; and (iii) an organic colloidal group enriched in Cr, Mn, Co, Cu and U. However, REE and V have an ambivalent behaviour, being alternatively in the organic pool and in the inorganic pool depending on sample. Moreover, organic speciation calculation using Model VI were performed on both samples for elements for which binding constants were available (Ca, Mg, Ni, Fe, Al, Th, Cr, Cu, Dy, Eu). Calculation shows relatively the same partitioning of these elements as ultrafiltration does. However, some limitations appear such as (i) a direct use of ultrafiltration results which tends to overestimate the fraction of elements bound to humic material in the inorganic pool as regards to model calculations as well as, (ii) a direct use of speciation calculation results which tends to overestimate the fraction of elements bound to humic material in the organic pool with regard to ultrafiltration results. Beside these limitations, one can consider that both techniques, ultrafiltration and speciation calculation, give complementary information, especially for more complex samples where inorganic and organic colloids compete.     

Competitive binding of REE to humic acid and manganese oxide: Impact of reaction kinetics on development of cerium anomaly and REE adsorption

The competitive binding of rare earth elements (REE) to purified humic acid (HA) and MnO₂ was studied experimentally using various HA/MnO₂ ratios over a range of pH (3 to 8). MnO₂, humic acid and REE solutions were simultaneously mixed to investigate the kinetics of the competitive reactions. Aqueous REE–HA complex is the dominant species whatever the experiment time, pH and HA/MnO₂ ratio. The value of the distribution coefficients between MnO₂ and solution (log K_d^Ree/Mno₂) increases with the HA/MnO₂ ratio, indicating that part of the REE–HA complexes are adsorbed onto MnO₂. The development of a Ce anomaly appears strongly limited in comparison with inorganic experimental conditions. Throughout the experimental run time, for HA/MnO₂ ratios of less than 0.4, MnO₂ acts as a competitor leading to a partial dissociation of the REE–HA complex. The majority of the dissociated REE is readsorbed onto the MnO₂ surface. The readsorption of REE is expressed by an increased Ce anomaly on the log K_d^Ree/Mno₂ pattern as well as a change in shape of the coefficient distribution of REE between soluble HA and solution pattern (log K_d^Ree/HA decrease for the heavy rare earth elements — HREE). Thus, REE are not only bound to MnO₂ as a REE–HA complex, but also as REE(III). Moreover, the competition between HA and MnO₂ for REE binding is shown to be higher at low pH (< 6) and low DOC/Mn ratio. This study partially confirms previous work that demonstrated the control of REE adsorption by organic matter, while shedding more light on the impact of pH as well as complexation reaction competition on long-term REE partitioning between solid surface and organic solutions. The latter point is important as regards to REE speciation under conditions typical of rock and/or mineral alteration.