A ship-based seismic survey was conducted close to a fiber-optic submarine cable, and 50 km-long distributed acoustic sensing (DAS) recordings with air-gun shots were obtained for the first time. We examine the acquired DAS dataset together with the co-located hydrophones to investigate the detection capability of underwater acoustic (hydroacoustic) signals. Here, we show the hydroacoustic signals identified by the DAS measurement characterizing in frequency-time space. The DAS measurement can be sensitive for hydroacoustic signals in a frequency range from $$10^{-1}\,\text {Hz}$$ 10 - 1 Hz to a few tens of Hz which is similar to the hydrophones. The observed phases of hydroacoustic signals are coherent within a few kilometers along the submarine cable, suggesting the DAS is suitable for applying correlation analysis using hydroacoustic signals. Although our study suggests that virtual sensor’s self-noise of the present DAS measurement is relatively high compared to the conventional in-situ hydroacoustic sensors above a few Hz, the DAS identifies the ocean microseismic background noise along the entire submarine cable except for some cable sections de-coupled from the seafloor.

The molecular dynamics technique has been used, in conjunction with the interionic potentials of Dagens et al. to study the stability. configuration, binding, and induced migration of mixed dumbbells in an irradiated AI-Zn alloy. For the purpose of comparisons, self-interstitials in pure AI were also investigated. The AI-AI and AI-Zn interactions were described by pair potentials which extended to ninth-neighbour distances. Both the self-interstitial dumbbell and the mixed dumbbell were found to be stable in the (l00) configuration. The formation energy of the self-interstitial is 2.89 eV and the mixed-dumbbell binding energy is 0.38 eV. As a result of this strong binding, the threshold energy required to induce the migration of the mixed dumbbell is about 1.2 eV, which is significantly larger than the minimum energy of about 0.15 eV transferred to a self-interstitial to induce its jumps in pure Al. Caging motions of the mixed dumbbell were observed. The present computer-simulation results are compared with experimental measurements.

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Mobile holographic lidar for remote determination of quantitative characteristics of gas and aerosol air pollution with high accuracy and space resolution is proposed. Differences in reflectivity of liquid and solid particles give a possibility to form polarization holograms and observe liquid and solid aerosols separately. Quantitative analysis of composition and concentration of particles observed in their holographic images is characterized by high level of sensitivity. Determination of gas pollution composition and concentration is performed by the spectral analysis of scattered signals.

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