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.

Dealiased Seismic Data Interpolation Using Seislet Transform With Low-Frequency Constraint

Abstract: Interpolating regularly missing traces in seismic data is thought to be much harder than interpolating irregularly missing seismic traces, because many sparsity-based approaches cannot be used due to the strong aliasing noise in the sparse domain. We propose to use the seislet transform to perform a sparsity-based approach to interpolate highly undersampled seismic data based on the classic projection onto convex sets (POCS) framework. Many numerical tests show that the local slope is the main factor that will affect the sparsity and antialiasing ability of seislet transform. By low-pass filtering the undersampled seismic data with a very low bound frequency, we can get a precise dip estimation, which will make the seislet transform capable for interpolating the aliased seismic data. In order to prepare the optimum local slope during iterations, we update the slope field every several iterations. We also use a percentile thresholding approach to better control the reconstruction performance. Both synthetic and field examples show better performance using the proposed approach than the traditional prediction based and the $F\mbox{--}K$ -based POCS approaches.

Boroxol Rings in Liquid and Vitreous B2O3 from First Principles.

Abstract: We investigate the structural and vibrational properties of glassy ${\mathrm{B}}_{2}{\mathrm{O}}_{3}$ using first-principles molecular dynamics simulations. In particular, we determine the boroxol rings fraction $f$ for which there is still no consensus in the literature. Two numerical models containing either a low or a high level of boroxol rings are tested against a gamut of experimental probes (static structure factor, Raman, $^{11}\mathrm{B}$ and $^{17}\mathrm{O}$ NMR data). We show that only the boroxol-rich model ($f=75%$) can reproduce the full set of observables. Total-energy calculations show that at the glass density, boroxol-rich structures are favored by about $6\text{ }\text{ }\mathrm{kcal}/(\mathrm{mol}\text{ }\text{ }\mathrm{\text{boroxol}})$. Finally, the liquid state is explored in the 2000--4000 K range and a reduction of $f$ to 10%--20% is obtained.

Metamictization and chemical durability of detrital zircon

Abstract: We have investigated the effect that metamictization has on the weathering of zircon in detrital continental sediments and tropical soils of the Amazon basin, Brazil. The degree of radiation damage in the near-surface region of the zircon grains was determined by Raman microprobe. In each of the four series investigated (i.e., sediment, podzol, topsoil, and subsoil horizons of lateritic soil), the degree of radiation damage ranges from less than 1014 to ~3.5 × 1015 α−decay/mg. The maximum degree of radiation damage coincides with the first percolation threshold of the metamictization process at ~3.5 × 1015 α-decay/mg. Below this threshold, amorphous volumes in the structure of damaged zircon are not connected to each other. The ranges of U, Th, and Pb contents (in ppm) measured by proton induced X-ray emission (PIXE) microanalysis are 100 < U < 7000, 100 < Th < 18000, and 100 < Pb < 1300. Chemical ages, assessed from U, Th, and total-Pb, range between 0.15 Ga and 2.8 Ga. This range is roughly consistent with the ages reported for the Precambrian shields of the Amazon basin (0.45–3.5 Ga). Corresponding radiation doses range between <2 × 1015 and 3 × 1016 α-decay/mg. Comparison of calculated doses with the degree of structural damage indicates that most of the zircon grains have experienced significant annealing. However, the degree of annealing differs from one grain to another. Thus, the acute maximum limit observed for the degree of radiation damage of the whole zircon series is better explained by low-temperature alteration or weathering processes than by thermal resetting. Following this interpretation, our results provide evidence for a dramatic decrease in the chemical durability of zircon in natural weathering environments when the radiation dose exceeds 3.5 × 1015 α-decay/mg. Below the first percolation threshold, the zircon population survives the soil formation intact, but more damaged zircons are dissolved during weathering/ alteration processes.