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Copyright of Experimental Technology & Management is the property of Experimental Technology & Management Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to obtain SnO2 quantum dots with good gas response, the SnO2 quantum dots with diameters of about 4 nm were successfully synthesized by using 1,3-dimethyl imidazolium-2-carboxylate (1,3-diMiM-2-COO) as inducing agent and polyethylene glycol 200 (PEG200) as dispersant. The struc- ture and morphology of SnO2 quantum dots were characterized by X-ray diffraction and high resolution transmission electron microscope. The purity, optical properties, and the specific surface area of SnO2 quantum dots were tested by FT-IR, UV-Vis spectrophotometer and specific surface analyzer, respective- ly. The response to ethanol gas was also tested. The results show that the prepared SnO2 quantum dots have uniform particle size, specific surface area of 123.89 m²/g, visible light transmittance of more than 90%, excellent ethanol gas sensitivity, and the sensitivity of SnO2, quantum dots can be up to 195. 34 at 250 °C and ethanol volume fraction of 300×10-6. [ABSTRACT FROM AUTHOR]

GB/T 3836.1-2021 Explosive atmospheres-Part 1: Equipment-General requirements stipulates that the threshold power of RF equipment in explosive environments shall not exceed 6 W. This regulation limits the application of high-power RF equipment in coal mines. However, existing research on electromagnetic safety in explosive environments lacks comprehensive theoretical analysis and experimental verification. In order to solve the above problems, the electromagnetic wave thermal effect equation is derived. It is analyzed that the controllable parameters affecting the generation of thermal energy from the mixture of gas and coal dust coupled by electromagnetic waves are the electromagnetic wave coupling time, the electric field strength and the electromagnetic wave frequency. Based on the regulation in GB/T 3836.1-2021 that the maximum surface temperature of electrical equipment that may accumulate coal dust cannot exceed 150 ℃, simulation experiments are conducted using the multi physics field simulation software COMSOL to evaluate the thermal safety of gas and coal dust mixtures coupled with electromagnetic waves of different emission powers. The results show that the emission power that meets the safety threshold of electromagnetic wave thermal effect with a temperature not exceeding 150 ℃ is 16.48 W. With the increase of electromagnetic wave emission power, the safe duration of electromagnetic wave thermal effect (the corresponding time period that the thermal energy generated by the mixed gas of electromagnetic wave coupling gas and coal dust not causing the ambient temperature to exceed 150 ℃) gradually decreases. However, as long as the safe duration is maintained, the emission power of electromagnetic waves is not limited.

Copyright of Chemical Engineering (China) / Huaxue Gongcheng is the property of Hualu Engineering Science & Technology Co Ltd. and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Mine Automation is the property of Industry & Mine Automation Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In order to study the effects of heat, viscosity reducing agent and gas on the viscosity of crude oil, the effects of heat, viscosity reducing agent and gas on the viscosity of crude oil in composite flooding were studied by using high temperature and high pressure rheometer. The results show that increasing temperature is the most effective way to reduce the viscosity of crude oil. In a certain pressure range, N2 is disadvantageous to reduce the viscosity of crude oil, and CO2 is advantageous to reduce the viscosity of crude oiL The viscosity reducer and CO2 can synergistically reduce the viscosity of crude oil. [ABSTRACT FROM AUTHOR]

As a member of the two-dimensional (2D) material family, 2D GaS has attracted much attention of researchers in recent years, In this paper, the electronic structure properties, magnetic properties and optical properties of monolayer 2D GaS doped with transition metal elements X (X=Mo, Tc, Ru) were calculated based on the density functional theory. The calculation results show that the monolayer GaS material is a non-magnetic semiconductor with an indirect band gap. When the S element is replaced, both the values of the formation energy under Ga-rich and S-rich conditions are positive, indicating that the transition metal elements Mo, Tc and Ru cannot spontaneously enter into the monolayer GaS material. All doped systems decrease the band gap of the monolayer GaS. In all doped systems, impurity energy levels are introduced around the Fermi level and they are mainly contributed by the 4d orbitals of the doped atoms. After doping, the band structures of all systems are asymmetric under spin-up and spin-down conditions, making the Mo-doped system become half-metallic ferromagnetic, the Tc-doped and Ru-doped systems are magnetic semiconductor properties. The total magnetic moments after Mo, Tc and Ru doping are 4 μB, 3 μB and 2 μB, respectively. The total magnetic moments of all doped systems are mainly generated by the local magnetic moments of the doped atoms. Moreover, the static dielectric constant of monolayer GaS is improved after doping with transition metal elements X, the polarization ability is enhanced, the absorption spectrum appears red-shifted, the absorption coefficients in the visible and near-infrared regions become larger, and the utilization rate of visible light is enhanced. [ABSTRACT FROM AUTHOR]

Copyright of Special Oil & Gas Reservoirs is the property of Special Oil & Gas Reservoirs Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The geological conditions of the karst terrace of synclinore are complicated. Geological disasters such as water inrush and mud outburst often occur when the tunnel crosses it. The Anping Tunnel was taken as an example. In the early stage of the design of the tunnel route, from the geological perspective, five main geological problems and possible geological disaster risks within the scope of the tunnel route were analyzed and evaluated one by one. And the concept of geological route selection of avoidance without disturbance was used. The route avoidance scheme was selected according to the evaluation results and the horizontal and vertical design indicators were determined. The research results have certain reference significance for geological route selection and route design of tunnels on the karst terrace under similar complicated geological conditions. [ABSTRACT FROM AUTHOR]

Objective As an important way to achieve energy measurement by obtaining the average heat value of natural gas, the study of performance evaluation methods for the cumulative sampling system is of great significance for ensuring the normal operation of the cumulative sampling system and obtaining representative samples. Methods According to the requirements of GB/T 13609-2017 Natural gas sampling guidelines and GB/T 30490-2014 The method for automatic sampling of natural gas, and combined with the on-site application of the cumulative sampling system, a performance evaluation method has been established, including the integrity of the sampling system configuration, compliance, airtightness and consistency of the sampling system, and compliance with preset parameters. Results Through specific evaluation experimental examples, it is verified that this performance evaluation method has good operability and adaptability. Conclusion The performance evaluation method of the cumulative sampling system can meet the current on-site usage needs. In the future, relevant method standards will be further established to provide standard guarantees for the promotion and implementation of natural gas energy metering. [ABSTRACT FROM AUTHOR]

In order to study the gas leakage in a confined space and the effect of venting methods on the subsequent explosion, a major gas accident scene in confined space was constructed based on FLACS software. The leakage, diffusion, and explosion behavior of the leaked gas in the confined space was investigated, and the venting effect on the subsequent explosion was analysed. The results showed that the leaked gas cloud from the closed section of the pipeline diffuses outward along the outer wall of the pipeline, forming an irregular concave shape, and the diffusion speed will be accelerated when encountering obstacles. The maximum overpressure of leaked gas cloud is 660.7 kPa, which can seriously damage the surrounding buildings, and the degree of damage to the buildings at the open end of the restricted space is higher than that at the closed end. When the outlet is installed in the axial position of the flame development, the pressure- venting effect is the best. The maximum explosion pressure in the confined space can be reduced to 312.4 kPa, a reduction of 52.70%. If the outlet is placed on the side of the confined space, the closer it is to the ignition source, the better the venting effect will be. The maximum explosion pressure in the confined space can be significantly reduced by increasing the length-to-width ratio of the outlet to expand the explosion area. When the length-to-width ratio is 34 : 1, the maximum explosion pressure is reduced to 15.4 kPa, a reduction of 97.65%. Reducing the outlet opening pressure can effectively reduce the maximum explosion pressure in the confined space. For the outlet opening pressure at 50 kPa, the maximum explosion pressure is reduced to 351.0 kPa, a reduction of 46.87%. [ABSTRACT FROM AUTHOR]

Copyright of Railway Construction Technology is the property of Railway Construction Technology Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Artificial improvement of coal seam permeability is the key to solve the low gas drainage efficiency and prevent gas dynamic disaster. Plasma based on physical discharge is one of the effective means of coal seam antireflection. However, previous studies focus on the characterization of pore-fissure structure of single breakdown, ignore the polarization effect of plasma on coal, and lack of in-depth research on the electrical properties and the evolution characteristics of pore-fissure structure under the action of cyclical plasma of loaded coal. In this paper, the cyclical plasma breakdown experiments of coal samples were carried out. The voltage and current waveforms in the process of coal breakdown were monitored thorough combining with high-voltage attenuation rod and the Roche coil, and the variation of electrical parameters such as pre-breakdown period, plasma breakdown period, number of wave peaks, peak voltage, peak current and energy conversion efficiency were analyzed. The evolution of small pores, medium pores, large pores and micro cracks under the conditions of 1, 5, 10, 15 and 20 times of breakdown was tested by NMR. The fractal dimension of seepage pore was also discussed through geometric fractal theory. The results show that the pre-breakdown period is at the level of thousands of microseconds only for the first time, and then it will drop to tens of microseconds, while the plasma breakdown period shows a “ladder” growth with the increase of breakdown times. The energy conversion efficiency is maintained at 28.7%−55.9%, showing a trend of rapid increase at first and then stable, indicating that the polarization effect of plasma on the electrical properties of coal is limited. The growth rate of medium and large pores is the most obvious, and some micro fracture structures will achieve a “0” breakthrough, indicating that plasma will significantly improve the seepage of gas. The fractal dimension shows a decreasing trend after breakdown, which proves that the originally isolated pore structure will be connected by the fracture from the perspective of pore fracture space dimension. The similarity between the change trend of porosity and energy conversion efficiency shows that plasma has an impact on the electrical properties of coal, and the change of coal electrical properties will also have an impact on the distribution of plasma channels.

In order to investigate the microscopic physicochemical properties and macroscopic coal-oxygen complex thermal effects in the low-temperature oxidation of coal under gas atmosphere, different metamorphic coal and secondary oxidized coal samples as research objects were selected in this paper. Fourier infrared spectrometer and C80 microcalorimeter were employed to study the changes of physicochemical structural properties, kinetic parameters and thermal effects in the low-temperature oxidation of coal under different gas atmospheres. By analysing the microstructure and macroscopic exothermic characteristics of different gas content during coal spontaneous oxidation, the ultimate influence of gas on the oxidation characteristics of coal was clarified. The results show that gas delays the low-temperature oxidation process of coal by inhibiting the relative content of key active groups in the low-temperature oxidation process of coal. 4% gas has the most obvious inhibitory effect. The degree of inhibition on the four active groups is: oxygen-containing functional groups (66.5%) > Aromatic hydrocarbons (47.0%) > Aliphatic hydrocarbons (29.7%) > Hydroxyl (24.7%). In the rapid exothermic stage, due to the large adsorption capacity of coal to gas molecules, gas occupies the adsorption sites in coal molecules, which hinders the process of coal-oxygen recombination reaction, resulting in the exothermic effect being suppressed by gas; at the same time, gas content significantly affects coal oxygen. The amount of activation energy required for the recombination process. For high metamorphic non-stick coal, lean coal and anthracite, gas has a more significant inhibitory effect on its low temperature oxidation reaction; it has less effect on low metamorphic long flame coal. For secondary oxidized coal samples, the inhibitory effect of gas on coal samples increases with the increase of gas content, while the effect of gas on primary oxidized coal samples decreases as the degree of metamorphism decreases, and the degree of inhibition when the gas content is 2% is stronger than 4%. The results of the work have great significance to the theoretical study of the prevention and control of the coupling of gas and coal spontaneous combustion causing accidents.

Aiming at the problem of coal and gas outburst in the process of coal mining in China, this paper first summarizes the research progress of coal and gas outburst mechanism, and points out that the research on outburst mechanism of tectonic belt is of great significance by summarizing the shortcomings of existing theoretical models. Then, the influence of geological structure on three key factors of coal and gas outburst is analyzed, that is, geological structure has a control effect on the distribution of in-situ stress and gas occurrence in coal seams, and tectonic movement can change the microstructure of coal, thus changing the physical and mechanical properties of coal; the coal and gas outburst process in the structural belt is summarized and divided into four stages: preparation, initiation, development and termination. The preparation stage includes two parts: tectonic movement and mining operation. Finally, based on the shortcomings of the existing research results, the direction of coal and gas outburst to be further studied is put forward from the perspective of geological structure.

In order to explore the influence of mechanical vibration on the gas diffusion characteristics of granular coal, the self-developed vibration-gas adsorption-desorption experimental platform was used to conduct the gas desorption-diffusion experiments of coal samples with different particle sizes before and after vibration. The dynamic diffusion coefficient model was used to select the lean coal of 1-3 mm and 0.25-0.3 mm in Guishuting Mine, respectively. The gas desorption-diffusion experiment of coal samples was carried out, and the vibration of coal samples with different particle sizes before and after was compared. The results show that the application of vibration can increase the gas diffusion amount and diffusion speed of granular coal, and the initial effective diffusion coefficient of gas desorption is also improved. The initial effective diffusion coefficient of small particle size coal sample is smaller than that of large particle size coal sample, but the early diffusion rate is larger, and the vibration has a greater impact on the diffusion characteristics. It is pointed out that, on the one hand, the enhancement of vibration effect of small-size coal samples leads to more obvious external force generated by vibration, which further aggravates the degree of gas diffusion. On the other hand, coal samples with large particle size have larger surface area, and can absorb more gas than coal samples with small particle size, so the initial diffusion rate is larger.

Coal spontaneous combustion and gas symbiosis disaster prevention and control has become an important issue to be solved urgently in coal mines. In order to explore the coupling characteristics and disaster-causing mechanism of symbiotic disasters, the evolution process of symbiotic disasters was studied by methods such as numerical simulation, and the early warning and prevention system framework of symbiotic disasters was established. The results show that the symbiotic disasters are based on the interweaving of multi-field time-space coupling, the ventilation volume increases, the air leakage in the goaf increases, and the disaster area moves to the middle and deep parts of the goaf; compared with the U-shaped ventilation system, the Y-shaped ventilation system can be effectively prevent gas accumulation in the upper corner, and the disaster area moves to the middle and deep parts of the goaf. Based on gas concentration and temperature, the symbiotic disasters early warning model is established, and a symbiotic disasters collaborative prevention and control system is proposed from the aspects of gas control, time control, oxygen control, and temperature control, etc., and an intelligent symbiotic disaster monitoring system framework is constructed.

Copyright of Railway Investigation & Surveying is the property of Railway Investigation & Surveying Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Food Research & Development is the property of Food Research & Development Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The micro crack and micro annular gap are inevitable during the production of condensate gas reservoir in Shunbei oil & gas field, but the existing self-healing agent has low temperature resistance, and the evaluation method of self-healing ability is very different from the downhole working conditions. So it can not be applied to Shunbei oil & gas field. A self-healing emulsion in gas suitable for Shunbei oil & gas field is developed, with the volume expansion rate in gas reaches 30%. This agent can prepare selfhealing cement slurry with density range of 1.45-2.20 g/cm³, which is suitable for 90-180 ℃, with low modulus of elasticity <7 GPa. At the same time, a reasonable evaluation method for the self-healing ability of cement in gas is devised. Through the first and second artificial fractures making, the self-healing ability of cement paste is 100% and 95.1% respectively. At present, the selfhealing cement slurry for gas has been tested in 3 wells, and the high quality rate of cementing quality is 100%, which meets the needs of long-term sealing of HTHP gas wells in Shunbei oil & gas field. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

China has a large number of abandoned coal mines, many of which are highly gassy mines. Considering the pros and cons of gas occurrence in abandoned coal mine and its timeliness characteristics, it is considered that there is an urgent need to develop and utilize gas resources in abandoned coal mines. This paper starts with two key steps of gas resource development and utilization in abandoned coal mine: gas resource evaluation, gas extraction and utilization in abandoned coal mine, to systematically summarize and analyze the current research progress in gas occurrence scope, gas source and gas occurrence state, gas resource estimation model, gas enrichment distribution law and optimization of extraction well distribution. The existing problems in the evaluation, extraction and utilization of gas resources in abandoned coal mines are obtained, and the next research direction is pointed out.

In order to be able to “see” the information inside the structure about premixed gas of air and gas deflagration flow field in a underground coal mine, to recognize the coupling relationship between shock wave and flame, obstacles accelerating the incentive effects of the flame, the nature of the inert medium flame retardants to suppress deflagration, the super high-speed laser schlieren system was further built on the existing mesoscale explosion shock wave pipeline, and the experimental test scheme of “M”, “Z” and linear optical path arrangement was proposed to replace the traditional pressure flame sensor test method, it provides a new idea to obtain the evolution process of shock wave and the microstructure flow field of flame when gas/air premixed gas is deflagrated.

Quaternary salt was an efficient additive for hydrate formation, which usually achieves the effect of improving hydrate phase equilibrium conditions by filling the hydrate cage. The effect of quaternary salt on phase equilibrium conditions of gas hydrates such as CH4 and CO2 was mainly relate to the concentration of quaternary salt. In terms of methane hydrate, TiPeAF and TiAAB had significant effects on phase equilibrium under the same phase equilibrium pressure: the phase equilibrium temperature of the system with TiPeAF (0.315%) and TiAAB (0.438%) was 20 K and 22 K higher than pure water system respectively. TBANO3, TAAB and TAAC had little effect on phase equilibrium: the phase equilibrium temperature was 10 K lower than that of the system with TBAB and TBAC. For CO2 hydrate, the phase equilibrium temperature of TiAAB system was 29 K higher than pure water system, and that of TBAF system was 26 K higher than that of pure water system. In addition, the combination of quaternary salt and other additives had a better improvement effect on the phase equilibrium conditions of hydrate: the phase equilibrium temperature of hydrate in the combination system of TBAB (0.05%) and NaCl (0.03%) was 10 K higher compared with the system which adding TBAB only. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Based on the three-phase reaction experiments, taking CO2 as the main gas phase, the typical minerals in coal as solid phase and mine water rich in iron and sulfate as liquid phase, the water-rock-gas reaction simulation experiment of closed gassy mine is carried out. The changes of chemical composition of mine water and coal mineral composition are compared and analyzed. The results have showed that in the mine water-rock-gas reaction, the pH value of the mine water increases and the Eh decreases, and the dissolution of mineral phase resulted in the increase of the content of Ca2+, HCO3-, SO42- and soluble SiO2 in mine water, while the content of Mg2+ did not change significantly, the total Fe concentration decreased, and the salinity increased significantly. Typical minerals of coal and rock have different degrees of dissolution reactions. When calcite dissolves, new carbonate minerals will be generated in the reaction process, while pyrite dissolves with the generation of chlorite.

The effects of the crack opening and closing, the change of temperature and relative humidity, and the different permeable media of water and gas on the permeability of concrete with macro crack were studied experimentally. The experimental results show that the initial degree of crack opening and closing has a great influence on the permeability. There is a nonlinear relationship between crack opening and closing degree and confining pressure. When the confining pressure reaches its threshold 20 MPa, the crack opening and closing degree and the variation range of gas permeability decrease. In the loading and unloading process of confining pressure, the crack opening amplitude during unloading phase is lower than the closing degree during loading phase, and the gas permeability change during unloading phase is relatively small. Due to the effect of high confining pressure, the occlusion of rough crack surface is more compact, and the crack width presents irreversible plastic deformation. Although the change of ambient temperature and humidity can bring the water vapor adsorption on the crack surface, its influence on the concrete permeability with macro crack is limited. [ABSTRACT FROM AUTHOR]

Aiming at the problem of gas overrun at No.31102 working face in Cuncaota No.2 Mine, a comprehensive control was adopted by combining the adjustment of the air supply of the working face and the gas extraction of the buried pipe in the tail roadway. By establishing a fluid-chemical-thermal multi-field coupling mathematical equation and using COMSOL software to simulate the gas control process, the hazard law of multi-field coupling in goaf was obtained. The research results show that the air volume of the working face increases, the high gas area of the goaf moves toward the back of the goaf, and the gas volume fraction of the working face decreases. The air volume of working face is 1 174 m³/min as the basic air volume. When the ratio is increased to 1.25, the gas volume fraction at the corner of the working face is reduced to 0.24%, the high temperature area of the goaf has a certain hysteresis relative to the range of the oxidation zone, the drainage flow rate of the buried pipe gas drainage increases, and the goaf is oxidized. The width of the belt also gradually increased, and finally the extraction flow rate was 60 m³/min, the width of the oxidation belt was 295 m, and the gas at the corner of the working face was reduced to 0.16%. [ABSTRACT FROM AUTHOR]

Copyright of New Building Materials / Xinxing Jianzhu Cailiao is the property of New Building Materials Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Pulp & Paper is the property of China Pulp & Paper Magazines Publisher and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Earthquake emergency treatment is a key technology to solve the last 1 km of earthquake early warning applications, and it has obvious effects on preventing gas accidents in earthquakes. As a communication technology, NB-IoT has technical advantages such as low cost, low power consumption, and wide coverage compared to traditional wireless communication methods such as 4G. In recent years, NB-IoT communication technology has been widely promoted in the field of Internet of Things as the latest technology, but there is no public application in the field of earthquake early warning. This article introduces a new gas earthquake emergency treatment system based on NB-IoT, discusses the principle and basic composition of the gas earthquake emergency treatment device based on NB-IoT, and analyzes and compares it with the existing similar devices. The key points in the research and development process are aimed to promote solutions based on NB-IoT to realize gas earthquake emergency disposal system, and provide technical guarantee for gas earthquake safety. [ABSTRACT FROM AUTHOR]

After a refinery was overhauled in 2019, the contents of hydrogen and liquefied gas above C3 in gas system changed greatly. The hydrogen and hydrocarbon enriched components were sent to high pressure gas system. The hydrogen and liquefied gas components were not fully recovered and used as fuel gas of heating furnace, which caused the waste of hydrogen and liquefied gas resources. By optimizing the flow and operation parameters of the feed gas and the flow of the light hydrocarbon recovery, adjusting initial distillation tower pressure of atmospheric vacuum unit, the monthly total economic benefit increased 1.27 million yuan, which achieved good economic. At the same time, the optimization directions at the next step were put forward:(1) The hydrogen-rich gas flow of S Zorb was further optimized; (2) The adsorbent of aromatic and hydrogen production PSA was replaced to increase processing load and increase output of hydrogen; (3) Optimal operation of diesel hydrotreating unit to decrease the emission of hydrocarbon-rich gas; (4) The gas compressor of coking unit in high load was operated to increase the recovery of hydrocarbon-rich gas and increase the yield of liquefied gas. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Clean Coal Technology is the property of Clean Coal Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Food Safety & Quality is the property of Journal of Food Safety & Quality Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The large eddy simulation of the turbulent mixing process for different density gases in the case of circular tube jet was carried out to investigate the effect of gas density ratio on the downstream gas mixing process. The results show that with helium and carbon dioxide injecting into air, the Reynolds numbers are 7 000 and 32 000, respectively. The calculated results of velocity and mass fraction are in good agreement with the experimental results. For the same jet flow flux, the low-density jets are developed faster than high-density jets. The pseudo-similarity of the variable-density jet is verified, and the coherent vortex structure is analyzed. The turbulent flow fields of carbon dioxide jets at different jet velocities are calculated to show that the low velocity jet has higher mixing rate than the high velocity jet. [ABSTRACT FROM AUTHOR]

Copyright of Tunnel Construction / Suidao Jianshe (Zhong-Yingwen Ban) is the property of Tunnel Construction Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective: To investigate low polarity chemical components of Schisandrae Sphynantherae Fructus (SSF). Methods: SSF was extracted by heat extraction with 95% ethanol. Then, the obtained extracts were further extracted with petroleum ether (PE) at 60-90°C. The main components of PE were analyzed by GC-MS method. The detection results were comparatively analyzed with the standard mass spectra data, and relative contents of the components were calculated using peak area normalization method. Results: Totally, 47 components were identified from the PE extraction of SSF. Sesquiterpenoids (82.35%) were the main components, then came fatty acids and their esters (5.8%), of which the 2 highest chemical compounds were ledene oxide (II) (22.71%) and alloaromadendrene oxide (II) (11.98%). Thirteen chemical components were first detected from this genus. Conclusion: Compared with the components extracted by steam distillation, supercritical CO2 extraction and Soxhlet extraction, the main components extracted by ethanol and PE were basically the same, but the contents were different. The study results indicated that the contents of fatty acids and esters were relatively lower by this method. [ABSTRACT FROM AUTHOR]

Aiming at the problem that the gas suction negative pressure can not be effectively improved due to the existence of the gas leakage passage and the poor drainage effect, the gas drainage sealing technology is studied. Based on the analysis of the distribution characteristics of the stress field around the borehole, the cause of the gas leakage in the bedding borehole is determined. And by simulating and analyzing the leakage of the borehole under the action of the active support force using COMSOL simulation software, a method of sealing the casing with a "sleeve support" is proposed. Field application at Marburg coal mine shows that the casing fixing technique can effectively support the drilling, and the single-hole gas drainage mixing flow rate is increased by about 10 times compared with the ordinary pumping drilling hole without the casing, and the concentration of single-hole gas extraction in single hole is increased by about 1.6 times. The research conclusions help to improve the efficiency of coal mine gas drainage. [ABSTRACT FROM AUTHOR]

To study the anisotropy of gas seepage in coal seams with low permeability,coal samples were prepared respectively in the parallel bedding direction and the vertical stratification direction of the same coal rock. Tri-axial servo seepage tests on gascontained coal were detected by using a self-developed apparatus. It is found that the permeability of coal samples in the parallel is far greater than that of coal samples in the vertical. With the increase of axial pressure,the permeability of coal samples in the parallel reaches its minimum at the yield point before the peak failure,while the permeability of coal samples in the vertical gets its minimum at the initial period of the elastic stage. The permeability of both the parallel and the vertical nonlinearly increases after the peak failure.

A one-dimensional mathematical model based on heat transfer and reaction kinetics was developed for an oxygen blast furnace and was validated with the operating conditions and dissected data of a conventional blast furnace. The influence of oxygen concentration and upper gas volume on the smooth operation and process variables of the oxygen blast furnace was investigated by the model combined with coal combustion at tuyeres and top gas balance for separation and preheating. When the oxygen blast furnace with top gas recycling is of low oxygen concentration and upper gas volume, the reduction of iron ore is worsen and massive unreduced iron oxide comes into slag. In the oxygen blast furnace with top gas recycling, oxygen concentration and upper gas volume have significant effect on the temperature, reducing ability of gas and reduction rate. A comparative analysis of the conventional blast furnace and the oxygen blast furnace with top gas recycling show that the oxygen blast furnace has a higher reducing ability of gas (1.0 to 1.5 times higher for CO content), faster reduction rate (1.49 m higher for the position of ore reduction), and less direct reduction (55.2% to 79.2% less for direct reduction degree).

Copyright of Journal of Heilongjiang University of Science & Technology is the property of Journal of Heilongjiang University of Science & Technology Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Objective： To establish a gas chromatography（GC） method for simultaneous determination of the contents of menthol and phenol in calamine menthol lotion，in order to provide a reliable method for quality control of calamine menthol lotion.Methods： Camphor was used as the internal standard and the solvent was 95% ethanol.Separation was carried out on an Agilent DB-624 capillary column （30 m×320 μm，1.8 μm） with nitrogen as the carrier gas.The column temperature was 140 ℃ and the injection port and flame ionization detector temperatures were 240 ℃ and 250 ℃，respectively.The split ratio was 10∶1 and the injection volume was 1 μl.Results：The contents of menthol and phenol in the ranges of 69.97-129.95 μg/ml （r=0.999 1） and 141.75-263.25 μg/ml （r=0.999 2） showed a good linear relationship with the peak area of internal standard. The average recovery rates of menthol and phenol were （103.35±1.14）% and （103.16±0.95）%（n=9），respectively.Conclusion：The established method is simple， feasible and reproducible， and could be used for quality control of calamine menthol lotion. [ABSTRACT FROM AUTHOR]

Copyright of Coal Science & Technology (0253-2336) is the property of Coal Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper focused on the problem of the source localization of coal mine gas release. Due to the existence of wind leakage,it is difficult to find the location accurately by using the conventional algorithms. In this study,a multisource sensor fusion based algorithm for locating the coal mine gas release was proposed. Firstly, the gas distribution in the goaf of a fully mechanized working face was analyzed and the observation model ol mine goaf area and the diffusion model of gas release were established. Then,the gas release source parameters of goaf were estimated using the Mixed Kalman Particle Filter algorithm ( MKPF) , and the coordinate of the estimated parameters was obtained according to the iterative operation. Finally, the data of wireless sensor target source sensing nodes and cluster head nodes were fused to locate the accurate coordinate of the gas release source. The research concludes that the MKPF algorithm has obvious advantages in accuracy localization, which can effectively overcome the difficulty of gas release source localization impacted by wind leakage. It can provide support for gas warning and gas drainage in goaf. [ABSTRACT FROM AUTHOR]