IPG Photonics

About: IPG Photonics is a based out in . It is known for research contribution in the topics: Laser & Fiber laser. The organization has 903 authors who have published 1241 publications receiving 63339 citations.

The biogeochemistry of mercury at the sediment–water interface in the Thau lagoon. 1. Partition and speciation

Abstract: Solid sediment, pore and epibenthic waters were collected from the Thau lagoon (France) in order to study the post-depositional partition and mobility of mercury in organic rich sediment. Total Hg (HgT) and monomethylmercury (MMHg) profiles were produced in both dissolved and solid phases. The distribution of HgT in the solid phase appeared to be related to the historical changes in the Hg inputs into the lagoon. HgT was in equilibrium between solid and solution phases in the sulfidic part of the cores, with a mean log Kd of 4.9 ± 0.2. The solid phase appeared to be a source of HgT for pore water in the upper oxic to suboxic parts of the cores. The MMHg represented a small fraction of HgT: 3–15% and 0.02–0.80% in the dissolved and solid phases, respectively. Its distribution was characterized by a main peak in the superficial sediments, and another deeper in the core within the sulfide-accumulating zone. In addition, high dissolved MMHg concentrations and methylated percentage were found in the epibenthic water. Ascorbate (pH 8) dissolution of the sediments and analyses of the soluble fraction suggest that the amorphous oxyhydroxides played a major role in controlling total and methylmercury mobility throughout the sediment–water interface. These features are discussed in terms of sources, transfer and transformations. Diffusive fluxes of HgT and MMHg from sediment to the water column for the warm period were estimated to be 40 ± 15 and 4 ± 2 pmol m−2 d−1, respectively.

Thermal properties, density and structure of percalcic and peraluminus CaO–Al2O3–SiO2 glasses

Abstract: Calcium silicate and aluminosilicate glasses with various SiO 2 contents (10–76 mol%) were prepared in the wide range of [Al 2 O 3 ]/[CaO] molar ratio from 0.10 to 4.00 by conventional melt-quenching method and an aerodynamic levitation device for a part of peraluminus glasses. Variations of glass transition temperature, the coefficient of linear expansion, and ionic packing factor derived from density measurements with [Al 2 O 3 ]/[CaO] molar ratio were studied. The glass structures of SiO 4 three dimensional network, mixed anions of (Si, Al)O 4 tetrahedra, isolated AlO 4 and Al–O–Al linkages were evaluated by FT-IR measurements. Compositional dependences of the properties are qualitatively related to the glass structure examined by IR spectroscopy and the proportions of AlO x (x = 4, 5, 6) species evaluated in a previous study by using 27 Al MQ NMR spectroscopy.

Numerical Modeling of Surface Waves Over Shallow Cavities

Abstract: A new stable and accurate, finite-difference 2D elastic seismic wave propagation modeling algorithm is developed, with a Perfectly Matched Layer (PML) absorbing boundary condition to avoid reflections from the edges of the numerical model. This is used to study the interaction of seismic surface waves with near-surface heterogeneities. The effects of different empty cavity shapes and depths and altered zones is evaluated from the direct and diffracted seismograms and corresponding Rayleigh wave dispersion images. Differential seismograms calculated for models both with and without a cavity show a complex, non-symmetrical, diffraction pattern and their dispersion images show well-localized scattering from heterogeneities. Missing coherent energy appears in specific frequency bands, related to the cavity depth, shape and degree of modification of the surrounding medium. The cavity more strongly affects seismograms when it is shallower. A 2‐m deep rectangular cavity generates more severe perturbations than a...

Macroscopic permeability of three-dimensional fracture networks with power-law size distribution.

Abstract: Fracture network permeability is investigated numerically by using a three-dimensional model of plane polygons uniformly distributed in space with sizes following a power-law distribution. Each network is triangulated via an advancing front technique, and the flow equations are solved in order to obtain detailed pressure and velocity fields. The macroscopic permeability is determined on a scale which significantly exceeds the size of the largest fractures. The influence of the parameters of the fracture size distribution---the power-law exponent and the minimal fracture radius---on the macroscopic permeability is analyzed. Eventually, a general expression is proposed, which is the product of a dimensional measure of the network density, weighted by the individual fracture conductivities, and of a fairly universal function of a dimensionless network density, which accounts for the influences of the fracture shapes and of the parameters of their size distribution. Two analytical formulas are proposed which successfully fit the numerical data over a wide range of network densities.