A small-sized two-frequency fluorometer based on the method of laser-induced fluorescence has been developed. This complex is intended for use on a remote-controlled uninhabited underwater vehicle (ROV) for simultaneous monitoring of oil products dissolved in sea water and assessing the state of phytoplankton communities. The spectrometer has passed full-scale tests on ROV of observation class RB-660D in the waters of the Amur Bay (Vladivostok) when submerged to depths of about 20 meters. The developed methodology and equipment can be used both for ecological monitoring of underwater areas in the presence of pollution in the form of dissolved oil products, and for assessing the damage caused by these pollutions to phytoplankton communities.
The paper presents a developed complex for monitoring and liquidation of emergency oil spills on the sea surface based on an unmanned aerial vehicle (UAV). For the monitoring function, a software component with elements of artificial intelligence is proposed that allows for the process of spill detection and semantic segmentation of oil slicks, followed by an assessment of the area and volumes of marine pollution. To eliminate oil spills, it is proposed to use dispersant spraying from an experimental UAV. Individual elements of the developed tools and methods were tested both in the course of laboratory tests and in the course of system monitoring of port water areas, and showed high efficiency.
A hardware-software complex based on UAVs with the possibility of splashdown for monitoring marine areas for the detection of oil spills and discharge of bilge water has been developed and assembled. Using the assembled complex, laboratory measurements of the induced fluorescence spectra of solutions of low-viscosity marine fuel DMA were performed under conditions of solar illumination and implemented a software component with elements of artificial intelligence for semantic image segmentation to identify oil spills on the sea surface.
The dynamics of spectral components arising in the time interval up to 15 ns after the main femtosecond pulse is investigated for filamentation of tightly focused laser radiation. The femtosecond pulse duration was 65 fs, the main pulse energy increased from 0.5 to 1.7 mJ. Several spectral components of laser emission in the wavelength range of 720–780 nm are registered. With increase of main pulse energy, the shape of the spectrum of the supercontinuum changes, the intensity of the post-pulse and the amplified spontaneous emission increases, and a shift of the component to the blue region is observed. It is assumed that the component whose central wavelength shifts to the blue region with is associated with Rabi splitting of the oxygen atom levels.
The compact mobile hardware-software complex based on a remotely operated vehicle (ROV) and a laser-induced breakdown spectrometer (LIBS) has been developed and tested in laboratory and in real-time condition for the tasks of analyzing the composition of sea water and bottom sediments on the continental shelf.
A program for recognizing oil spill on the sea surface, based on an artificial intelligence element, was developed and tested on the example of real oil pollution in Peter the Great Bay for use on an unmanned aerial vehicle. The feature of the spectra of broadband radiation ascending from the sea surface is analyzed. It is concluded that the method of recording the spectra of the ascending radiation can be used to detect heavy oil fractions on the sea surface. A software algorithm for the formation of datasets of spectra of induced fluorescence of sea water containing various dissolved grades of petroleum products has been developed and tested. A machine learning procedure has been carried out to create a program element for classifying the type of oil hydrocarbons dissolved in seawater.
The spectral and temporal characteristics of plasma radiation generated by a Ti:Sa femtosecond laser pulses on the surface of Ca aqueous solutions are investigated. Optimum parameters of laser radiation and signal registration are determined to improve the metrological characteristics of time-resolved femtosecond laser induced breakdown spectroscopy.
The limit of detection for Mg, Mn, Sr, B was experimentally investigated depending on the laser pulse repetition rate in the time resolved femtosecond LIBS. Optical breakdown on the surface of aqueous solutions was generated by the femtosecond Ti:Sa laser with the following parameters: central wavelength - 800 nm, pulse width - 60 fs, pulse energy - 1 mJ, repetition rate 50 Hz, 166 Hz, 250 Hz, 500 Hz, 1000 Hz. The best limit of detection was obtained for the 166 Hz laser repetition rate and for the following elements Mg I (285.2 nm), Mn I (403 nm, 403.3 nm), B I (283.2 nm), Sr I (460.7 nm) are 0.058, 0.025, 1.13, 4.69-3 mg/kg respectively.
Limits of detection of concentrations for dissolved samples of Medium fuel oil and Marine gas oil were measured by two frequency of laser induced fluorescence with 266 and 400 wave length and 100 fs pulses duration. Dynamics of fluorescence spectrums of different types of oil products was investigated.
The spectral and temporal characteristics of plasma radiation (contours and kinetics of the intensity of spectral lines) generated by a Ti:Sa femtosecond laser pulses on the surface of water solutions are investigated. The best parameters of optical spectra registration and of the laser radiation are determined to improve the metrological characteristics of timeresolved femtosecond laser induced breakdown spectroscopy.
The temporal evolution of width and shift of N I 746.8 and O I 777.4 nm lines is investigated in filament plasma produced by tightly focused femtosecond laser pulse (0.9 mJ, 48 fs). Nitrogen line shift is determined by joint action of electron impact shift and far-off resonance AC Stark effect. Intensive (I ~ 1010 W/cm2 ) electric field of ASE and postpulses result in possible LS coupling break for O I 3p 5P level and generation of Rabi sidebands. The blue-shifted main femtosecond pulse and Rabi sideband cause the stimulated emission of N21+ system.
The spectral bands shape of sea water Raman scattering and laser induced fluorescence of chlorophyll A were experimentally investigated when scattering and fluorescence induced by the different wavelength and duration of laser radiation. The femtosecond laser pulses with 400, 480, 500 nm of wavelength, nanosecond impulse (532 nm) and continuous laser radiation (527 nm and 400 nm) were used in these experiments. The spectral line shape of the sea water Raman scattering is Gauss function corresponding to the symmetrical vibrations (ν1) when femtosecond laser pulses were used. Maxima corresponding to the Fermi resonance (2ν2) and antisymmetric vibrations (ν3) were not detected.
Dependence of filamentation thresholds were investigated as well as filamentation special spread and supercontinuum generation concerning concentration of chlorophyll A photosynthetic pigment. Energy thresholds of filamentation origin were identified in sea water samples. It was observed that rise of chlorophyll A concentration led to rise of filamentation origin threshold. As chlorophyll A concentration rise the efficiency of radiation transformation reduces (radiation of basic harmonic of titan-sapphire laser onto supercontinuum spectrums in wave length range from 420nm to 680 nm).
Time-resolved laser-induced breakdown spectroscopy (LIBS) has been used as an analytical chemistry technique suitable for water analysis. Optical breakdown on the surface of water solutions was generated by the femtosecond Ti:Sa laser with the following parameters: central wavelength - 800 nm, pulse width - 60 fs, pulse energy - 1 mJ, repetition rate 50 Hz, 166 Hz, 250 Hz, 500 Hz, 1000 Hz. The limit of detection (LOD) for Mg I (285.2 nm), Mn I (403 nm, 403.3 nm), Pb I (283.3 nm), Sr I (460.7 nm) was experimentally investigated depending on the laser pulse repetition rate by the time resolved femtosecond LIBS. The best LODs for Mg I - 0.058 mg/kg, Mn I - 0.025 mg/kg, Pb I - 0.711 mg/kg, Sr I - 4.69x10-3 mg/kg water solutions were obtained for 166 Hz repetition rate.
The developed underwater laser induced breakdown spectrometer consists of two units: 1- remotely operated vehicle (ROV) with the next main characteristics: work deep – up to 150 meters, maximum speed of immersion 1 m/s, maximum cruise velocity - 2 m/s and 2 – spectrometer unit (SU) consist of a DPSS Nd: YAG laser excitation source (double pulse with 50 mJ energy for each pulse at wavelength 1064 nm, pulse width 12 ns and pulse repetition rate 1-15 Hz, DF251, SOL Instruments), a spectrum recording system (Maya HR4000 or 2000 Pro spectrometer, Ocean Optics) and microcomputer. These two units are connected by Ethernet network and registered spectral data are automatically processed in a MATLAB platform.
Experimentally investigated limit of detection Mg, Al, Sr, Pb. depending on the pulse repetition rate femtosecond Ti: Sa laser optical breakdown in aqueous solutions on the surface of the investigated element in the laser pulse duration 60 fs, pulse energy of 1 mJ. The study was conducted for the laser pulse repetition rate of 50 Hz, 150 Hz, 250 Hz. To choose the optimal time delay of registration relative to the laser beam for the following chemicals Na, N, Fe, Ca, Mg, Al, Pb, Mn.
Investigation of nonlinear optical properties of solutions of carbon quantum dots synthesized by hydrothermal synthesis of chitin before and after coating with titanium dioxide. It is shown that the titanium dioxide has an activating effect, allows varying the carbon quantum dots non-linear characteristics.
The forms and intensities of Raman lines and chlorophyll A fluorescence have been researched when excited at 532 nm, depending on the duration of the pulses of the exciting radiation. The duration of continuous operation ranged from emission to 120 fs.
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