Detection of 12426 SB2 candidates in the LAMOST-MRS, using a binary spectral model

We use an updated method for the detection of double-lined spectroscopic binaries (SB2) using $v \sin{i}$ values from spectral fits. The method is applied to all spectra from LAMOST-MRS. Using this method, we detect 12426 SB2 candidates, where 4321 are already known and 8105 are new discoveries. We check their spectra manually to minimise possible false positives. We also detect several cases of contamination of the spectra by solar light. Additionally, for candidates with multiple observations we compute mass ratios with systemic velocities and determine Keplerian orbits. We present an updated catalogue of all SB2 candidates together with additional information for some of them in separate data tables.Comment: accepted in MNRAS 2023-10-16. arXiv admin note: substantial text overlap with arXiv:2207.0699

Factors impacting gas content measurements using gas desorption by drilling underground boreholes

Accurate determination of the gas content in coalbeds is important for safe mining. Currently, gas desorption by drilling underground boreholes is the most commonly used gas determination method. However, this method is not very accurate and needs to be improved. In this study, we established a laboratory protocol based on coal adsorption studies to analyse factors affecting the measurement accuracy. The results showed that exposure time, sampling method, sample weight, particle size and gas loss estimate significantly affected the gas content measurement using gas desorption by drilling underground boreholes. Longer exposure time and increased particle size resulted in higher relative errors. Sampling by coring is more accurate than sampling by drilling. The higher the sample weight is for samples weighing less than 240 g, the larger the error of the in situ measurements of desorbed gas, residual gas and lost gas is. The error tends to stabilize for heavier samples. The gas losses at different exposure times calculated using the commonly used Barrer model, power function method and negative exponent method were compared. The gas loss error within 0–12 min, computed with the Barrer model, and after 12 min, computed with the power function method, is minimal. The modified formula of gas loss was obtained using the combination of a fitting analysis and the relationship between gas loss and exposure time. Subsequently, the optimal procedure for in situ gas content measurements using gas desorption by drilling underground boreholes was determined. The gas content errors for anthracite, gas coal, lean coal and long flame coal, which were measured using gas desorption by drilling underground boreholes and corrected using the gas loss formula, decreased significantly to less than 10%, thus, meeting the engineering accuracy norm

Studies on the Low-Temp Oxidation of Coal Containing Organic Sulfur and the Corresponding Model Compounds

This paper selects two typical compounds containing organic sulfur as model compounds. Then, by analyzing the chromatograms of gaseous low-temp oxidation products and GC/MS of the extractable matter of the oxidation residue, we summarizing the mechanism of low-temp sulfur model compound oxidation. The results show that between 30 °C to 80 °C, the interaction between diphenyl sulfide and oxygen is mainly one of physical adsorption. After 80 °C, chemical adsorption and chemical reactions begin. The main reaction mechanism in the low-temp oxidation of the model compound diphenyl sulfide is diphenyl sulfide generates diphenyl sulfoxide, and then this sulfoxide is further oxidized to diphenyl sulphone. A small amount of free radicals is generated in the process. The model compound cysteine behaves differently from diphenyl sulfide. The main reaction low-temp oxidation mechanism involves the thiol being oxidized into a disulphide and finally evolving to sulfonic acid, along with SO2 being released at 130 °C and also a small amount of free radicals. We also conducted an experiment on coal from Xingcheng using X-ray photoelectron spectroscopy (XPS). The results show that the major forms of organic sulfur in the original coal sample are thiophene and sulfone. Therefore, it can be inferred that there is none or little mercaptan and thiophenol in the original coal. After low-temp oxidation, the form of organic sulfur changes. The sulfide sulfur is oxidized to the sulfoxide, and then the sulfoxide is further oxidized to a sulfone, and these steps can be easily carried out under experimental conditions. What’s more, the results illustrate that oxidation promotes sulfur element enrichment on the surface of coal