Depolarization ratio of the ν1 Raman band of methane at different environment

The work is aimed at measuring the depolarization ratio of the ν1 Raman band of methane in nitrogen and carbon dioxide media at a pressure of 50 atm. To improve the accuracy of estimating the ν1 intensity in the depolarized spectrum, we used the simulation of the ν3 band. It was found that the environment of nitrogen and carbon dioxide has a negligible effect on the depolarization ratio of the ν1 Raman band of methane

Effect of helium on the Raman spectrum of methane in the 2500–3300 cm−1 range

The peak positions and halfwidths of the Q-branch of the ν1 band and the ratios of intensities of the Q-branches of ν3 and 2ν2 bands of methane are measured in a methane–helium mixture at different pressures and concentrations. An empirical model is developed for estimation of the He concentration in a methane-containing medium from measurements of the above parameters. The error in the He concentration is found to be less than 1% when using the ν1 band halfwidth. The paths of improvement of this technique and enhancement of its accuracy are considered

Raman natural gas analyzer: Effects of composition on measurement precision

Raman spectroscopy is a promising method for analyzing natural gas due to its high measurement speed and the potential to monitor all molecular components simultaneously. This paper discusses the features of measurements of samples whose composition varies over a wide range (0.005-100%). Analysis of the concentrations obtained during three weeks of experiments showed that their variation is within the error caused by spectral noise. This result confirms that Raman gas analyzers can operate without frequent calibrations, unlike gas chromatographs. It was found that a variation in the gas composition can change the widths of the spectral lines of methane. As a result, the measurement error of oxygen concentration can reach 200 ppm. It is also shown that neglecting the measurement of pentanes and n-hexane leads to an increase in the calculated concentrations of other alkanes and to errors in the density and heating value of natural gas

SHG in γ-Ga2S3 powder

We report results on comparative study of SHG in powder of promising nonlinear γ-Ga2S3 crystal. Digallium trisulfide powders with particle size from 20 μm to 500 μm were tested in comparison with powders of well-known LBO, BBO, KABO, KDP, and LN crystals under the pumping by 7 ns 1064 Nd:YAG laser. Laser-induced damage threshold of different powder fractions were determined. The γ-Ga2S3 shown high damage threshold and large SHG intensity: 56 times to that in LBO powder, 15 in BBO, 50 in KABO, 67 in KDP, and 3 in LN (for particle size: 20–50 μm), that renders it amongst the most promising crystal for frequency conversion of high-intense nanosecond radiation of near-IR lasers by optical rectification technique

An Economic Model of Sustainable Development in the Russian Arctic: The Idea of Building Vertical Farms

The main aim of the article is to find out the key factors of sustainable development of the Russian Arctic, which is strategically significant for Russia. The academic literature was reviewed to find out the time dynamics of the references to the economic models suitable for achieving the goals of sustainable development, and there has been hyperbolic growth in the attention paid to similar problems all around the world. The article compares three relatively new economic models in order to understand which of them is the most applicable to the promotion of sustainable development in the Russian Arctic: (a) bioeconomy, (b) green economy and (c) circular economy. The analysis of the relevant sources shows that the model of the circular economy is preferable for the Russian Arctic. Most of the article is dedicated to understanding the sources and mechanisms of the circular economy. The schematic description of vertical greenhouses and possibility of using vertical farms are presented in the paper as an example of organization of local food production according to the principles of the circular economy. The article considers a modeled project of creating a vertical farm in the Russian Arctic and a simulated indicator—profit of the vertical farm

Evaluation of the metrological characteristics of Raman analyzer of natural gas

The article presents methods for analyzing the natural gas composition and describes the advantages of Raman spectroscopy compared with gas chromatography. The metrological characteristics of a Raman gas analyzer developed at the Institute of Monitoring of Climatic and Ecological Systems have been studied. A series of measurements of the characteristics of three natural gas simulators with different concentrations of components of gas mixtures were performed. Raman gas analyzers provided high measurement accuracy, close to gas chromatographs when analyzing components with a low molar fraction (0.001–0.010%). Notably, when analyzing components with a molar fraction range of 0.01–100.00%, the accuracy of the proposed Raman gas analyzer surpassed the accuracy of gas chromatographs