Ride-through-fault capabilities of DFIG wind farm connected to a VSC station during a DC fault

This work analyzes the capabilities of ride-through-fault (RTF) of a double-fed induction machine (DFIG), -based wind farm connected to a VSC-, in case of a fault in the DC side of the VSC. The modelling of the DFIG wind turbine takes into account key aspects that intervene in succeeding the fault ride-through such as the power capacity of its electronic converter and its control scheme. As result a better understanding of the behaviour and capabilities of such system to perform a successful RTF is achieved. This work also analyzes the behaviour of the momentary islanding of the system composed by the wind farm and the ac filters of the VSC station. Using that information, a novel control scheme for the offshore VSC station is proposed in order to enhance RTF capabilities of the wind farm in case of such DC faults

Ride-through-fault capabilities of DFIG wind farm connected to a VSC station during a DC fault

This work analyzes the capabilities of ride-through-fault (RTF) of a double-fed induction machine (DFIG), -based wind farm connected to a VSC-, in case of a fault in the DC side of the VSC. The modelling of the DFIG wind turbine takes into account key aspects that intervene in succeeding the fault ride-through such as the power capacity of its electronic converter and its control scheme. As result a better understanding of the behaviour and capabilities of such system to perform a successful RTF is achieved. This work also analyzes the behaviour of the momentary islanding of the system composed by the wind farm and the ac filters of the VSC station. Using that information, a novel control scheme for the offshore VSC station is proposed in order to enhance RTF capabilities of the wind farm in case of such DC faults

Environmental and geochemical characteristics of heavy metals in soils around the former mining area of zeïda (High Moulouya, Morocco)

The Zeïda mining center, closed in the mid-1980s, was once intensively exploited for lead concentrates. Throughout its activity, more than 12 Mt of tailings were generated and, to this day, they are still abandoned in the open air, exposed to weathering conditions without any rehabilitation. The purpose of the present study is to evaluate the environmental and geochemical characteristics of the soils, combining physicochemical, mineralogical, sequential, and kinetic extraction analyses, as well as the metallic spatial distribution and pollution indices of heavy metals (Pb, Cd, Cu, As, and Zn), levels, and risks. The results showed that the abandoned tailings had the highest concentrations of heavy metals, far exceeding their equivalents in the international and local guidelines. The soils spatial distribution maps showed that the levels of heavy metals decreased with distance from the tailings. Based on the pollution indices results, the soils located on and near the tailings are highly contaminated mainly by Pb. While downstream of the tailings, this contamination intensity decreased until becoming null. The sequential extraction results indicated that Pb, Zn, and Cd were primarily associated with the exchangeable fraction in tailings and soils. Therefore, they were more mobile and environmentally hazardous in the study area. The As was mainly associated with the residual fraction, and was thus immobile. Cu was more mobile in tailings as long as it was associated with the reducible fraction while it became immobile in the downstream soils. The kinetic extractions using EDTA and H2O revealed that the labile and less labile fractions were very significant in tailing for the majority of heavy metals. The methodology applied in this study may constitute a valuable tool to develop appropriate mine reclamation solution

Physical and chemical properties of the groundwater of the Santo Domingo-Salinas ranges, South Central Pyrenees

The Santo Domingo-Salinas ranges represent a unique Natural Area in the south-central Pyrenees, and they were declarationas a Protected Landscape in 2015. Available biological and geological knowledge is extensive but lacks of information on groundwater quality. In this work we provide new hydrogeological results and integrate them with previously available hydrogeological data. To do so, we have: (i) compiled existing hydrogeological information, (ii) exhaustively developed an inventory of water points, (iii) sampled, analyzed and interpreted the hydrochemical facies detected, and (iv) developed a preliminary conceptual model for the hydrogeological functioning of the area. These information has been integrated in an map that displays the chemical analyses of the two new campaigns (Stiff diagrams), the flow rates and the three aquifer systems defined. This new information improves and synthetizes the knowledge of the hidrogeology of the Santo Domingo-Salinas ranges Protected Landscape and it will help in its future management and planning

Transversal inhomogeneities in dilute vibrofluidized granular fluids

The spontaneous symmetry breaking taking place in the direction perpendicular to the energy flux in a dilute vibrofluidized granular system is investigated, using both a hydrodynamic description and simulation methods. The latter include molecular dynamics and direct Monte Carlo simulation of the Boltzmann equation. A marginal stability analysis of the hydrodynamic equations, carried out in the WKB approximation, is shown to be in good agreement with the simulation results. The shape of the hydrodynamic profiles beyond the bifurcation is discussed

Non-perturbative effects and the resummed Higgs transverse momentum distribution at the LHC

We investigate the form of the non-perturbative parameterization in both the impact parameter (b) space and transverse momentum (p_T) space resummation formalisms for the transverse momentum distribution of single massive bosons produced at hadron colliders. We propose to analyse data on Upsilon hadroproduction as a means of studying the non-perturbative contribution in processes with two gluons in the initial state. We also discuss the theoretical errors on the resummed Higgs transverse momentum distribution at the LHC arising from the non-perturbative contribution.Comment: 22 pages, 10 figure

Effects of Zn Substitution in the Magnetic and Morphological Properties of Fe-Oxide-Based Core-Shell Nanoparticles Produced in a Single Chemical Synthesis

Magnetic, compositional, and morphological properties of Zn-Fe-oxide core-shell bimagnetic nanoparticles were studied for three samples with 0.00, 0.06, and 0.10 Zn/Fe ratios, as obtained from particle-induced X-ray emission analysis. The bimagnetic nanoparticles were produced in a one-step synthesis by the thermal decomposition of the respective acetylacetonates. The nanoparticles present an average particle size between 25 and 30 nm as inferred from transmission electron microscopy (TEM). High-resolution TEM images clearly show core-shell morphology for the particles in all samples. The core is composed by an antiferromagnetic (AFM) phase with a Wüstite (Fe1-yO) structure, whereas the shell is composed by a ZnxFe3-xO4 ferrimagnetic (FiM) spinel phase. Despite the low solubility of Zn in the Wüstite, electron energy-loss spectroscopy analysis indicates that Zn is distributed almost homogeneously in the whole nanoparticle. This result gives information on the formation mechanisms of the particle, indicating that the Wüstite is formed first, and the superficial oxidation results in the FiM ferrite phase with similar Zn concentration than the core. Magnetization and in-field Mössbauer spectroscopy of the Zn-richest nanoparticles indicate that the AFM phase is strongly coupled to the FiM structure of the ferrite shell, resulting in a bias field (HEB) appearing below TNFeO, with HEB values that depend on the core-shell relative proportion. Magnetic characterization also indicates a strong magnetic frustration for the samples with higher Zn concentration, even at low temperatures

Global QCD Analysis and the CTEQ Parton Distributions

The CTEQ program for the determination of parton distributions through a global QCD analysis of data for various hard scattering processes is fully described. A new set of distributions, CTEQ3, incorporating several new types of data is reported and compared to the two previous sets of CTEQ distributions. Comparison with current data is discussed in some detail. The remaining uncertainties in the parton distributions and methods to further reduce them are assessed. Comparisons with the results of other global analyses are also presented.Comment: (Change in Latex style only: 2up style removed since many don't have it.) 35 pages, 23 figures separately submitted as uuencoded compressed ps-file; Michigan State Report # MSU-HEP/41024 and CTEQ 40

Coherent Photoproduction of pi^+ from 3^He

We have measured the differential cross section for the $\gamma$$^3$He$\rightarrow \pi^+ t$ reaction. This reaction was studied using the CEBAF Large Acceptance Spectrometer (CLAS) at Jefferson Lab. Real photons produced with the Hall-B bremsstrahlung tagging system in the energy range from 0.50 to 1.55 GeV were incident on a cryogenic liquid $^3$He target. The differential cross sections for the $\gamma$$^3$He$\rightarrow \pi^+ t$ reaction were measured as a function of photon-beam energy and pion-scattering angle. Theoretical predictions to date cannot explain the large cross sections except at backward angles, showing that additional components must be added to the model.Comment: 11 pages, 16 figure

Measurement of the Nucleon Structure Function F2 in the Nuclear Medium and Evaluation of its Moments

We report on the measurement of inclusive electron scattering off a carbon target performed with CLAS at Jefferson Laboratory. A combination of three different beam energies 1.161, 2.261 and 4.461 GeV allowed us to reach an invariant mass of the final-state hadronic system W~2.4 GeV with four-momentum transfers Q2 ranging from 0.2 to 5 GeV2. These data, together with previous measurements of the inclusive electron scattering off proton and deuteron, which cover a similar continuous two-dimensional region of Q2 and Bjorken variable x, permit the study of nuclear modifications of the nucleon structure. By using these, as well as other world data, we evaluated the F2 structure function and its moments. Using an OPE-based twist expansion, we studied the Q2-evolution of the moments, obtaining a separation of the leading-twist and the total higher-twist terms. The carbon-to-deuteron ratio of the leading-twist contributions to the F2 moments exhibits the well known EMC effect, compatible with that discovered previously in x-space. The total higher-twist term in the carbon nucleus appears, although with large systematic uncertainites, to be smaller with respect to the deuteron case for n<7, suggesting partial parton deconfinement in nuclear matter. We speculate that the spatial extension of the nucleon is changed when it is immersed in the nuclear medium.Comment: 37 pages, 15 figure