The vibrational spectrum of CaCO3 aragonite: A combined experimental and quantum-mechanical investigation

The vibrational properties of CaCO3 aragonite have been investigated both theoretically, by using a quantum mechanical approach (all electron Gaussian type basis set and B3LYP HF-DFT hybrid functional, as implemented in the CRYSTAL code) and experimentally, by collecting polarized infrared (IR) reflectance and Raman spectra. The combined use of theory and experiment permits on the one hand to analyze the many subtle features of the measured spectra, on the other hand to evidentiate limits and deficiencies of both approaches. The full set of TO and LO IR active modes, their intensities, the dielectric tensor (in its static and high frequency components), and the optical indices have been determined, as well as the Raman frequencies. Tools such as isotopic substitution and graphical animation of the modes are available, that complement the analysis of the spectrum

Long range propagation modeling of offshore wind turbine construction noise using Finite Element and Parabolic Equation models

Noise generated by marine pile driving during offshore wind turbine construction radiates into and propagates through the air, water, and ocean bottom. Predicting noise levels around wind turbine support structures at sea is required to estimate the effects of the noise on marine life. We use Finite Element (FE) and Parabolic Equation (PE) models to predict long range propagation of noise from the construction of offshore wind turbines. FE analysis produced pressure outputs at short ranges which are used as a starting field for a modified PE propagation model. In FE analysis models, we implement the axisymmetric elements and implicit and steady state dynamic analysis with pressure impact loading on top of the pile to simulate pile driving noise radiation. This paper shows the modified PE long range pressure field outputs from the offshore wind turbine support structure in a shallow water environment around Block Island, Rhode Island. © 2012 IEEE

Sorption of Uranyl Cations on a Rutile (001) Single Crystal Monitored by Surface Second-Harmonic Generation

The rotational anisotropy of second-harmonic generation at the surface of a (001) single-crystal rutile is obtained in the presence of uranyl cations sorbed at the surface from acidic solutions at various concentrations. Surface second-harmonic generation appears to be sensitive to the presence of uranyl cations on the rutile samples. Evolution of the anisotropy pattern with initial uranyl concentration is analyzed through a phenomenological model. The elements obtained for the nonlinear susceptibility tensor for each sample significantly constrain the geometry of the possible sorption complexes between uranyl cations and rutile and lead to the proposition of two sorption sites involving different oxygen atoms of the rutile surface

Underwater acoustic energy fluctuations during strong internal wave activity using a three-dimensional parabolic equation model

The three-dimensional Monterey-Miami parabolic equation model is used to simulate a nonlinear internal wave (NIW) crossing the sound field in a shallow water environment. The impetus for this research stems from acoustic measurements taken during the Shallow Water \u2706 (SW06) field experiment, where a NIW traversed the water column such that soliton wavecrests were nearly parallel to the source-receiver path. Horizontal refraction effects are important in this scenario. A sound speed profile adapted from experimental SW06 data is used to simulate the NIW, assuming variations along the wavecrests (e.g., curvature) are negligible. Broadband and modal energy metrics show acoustic fluctuations due to internal wave activity. Repeated model runs simulate the NIW crossing the parabolic equation (PE) field over space and time. Statistical analysis shows the PE data are best fit by a lognormal distribution but tends to an exponential distribution during certain scenarios. Small angle differences between the acoustic track and the propagating NIW cause substantial differences in energy distribution throughout the PE field. While refraction effects due to the leading edge of the NIW\u27s arrival are important in all cases, the impacts of focusing and defocusing in the perfectly parallel case dominate the field fluctuations. In the non-parallel case, the strong fluctuations introduced by the passage of the NIW are of similar order to the refraction off the leading edge