Search

Coal and gas outburst is still a major safety problem in the process of coal production in China. Correctly understanding of the migration law of outburst high gas and pulverized coal is an important basis for accurately predicting the occurrence time and possible scope of outburst. To reveal the airflow disturbance characteristics and coal-gas flow rule in coal and gas outburst process, outburst coal-gas migration simulations under different gas pressures were conducted using a self-developed visual outburst dynamic effect test device. The results showed that coal-gas flow state at the outburst port is divided into subcritical flow, critical flow, and supercritical flow state. The pulverized coal-gas flow migration in the roadway space can be divided into coal gas two-phase flow area, air compression area, and undisturbed area. Under the experimental conditions, the maximum propagation velocities of wave are 342.22~359.21 m/s, and the coal gas two-phase flow is far less than the propagation velocities of outburst wave, just 3.68~33.33 m/s. When the outburst energy is large, multiple compression waves can superimpose to form shock waves. The peak value of the wave does not necessarily appear in the first boosting range. The presence of pulverized coal leads to a faster attenuation of shock wave, but it makes a greater dynamic destructive force at the same speed.

In order to deeply explore the destructive effect of the impulsive airflow on the mine antioutburst door when coal and gas outbursts occur in underground coal mines, a large-scale coal and gas outburst dynamic effect simulation experiment device is used to carry out the coal and gas outburst disaster simulation experiment. The impact load and deformation characteristics of the antioutburst door under the impact airflow during coal and gas outburst are analyzed, and the experimental results are discussed in depth through numerical simulation analysis and field example analysis. Based on this, the internal and external causes of the damage of the antioutburst door on the coal mine site are analyzed, the key technologies that need to be solved in the design of the antioutburst door’s disaster resistance are studied, and the overall design of the structure optimization design of the antioutburst door is proposed. The research results show that after coal and gas outburst, the pressure on the antioutburst door will rise and fall, and the fluctuation will be greater. Under the same installation position, the farther the antioutburst door is from the protruding point, the less pressure it bears. In the middle and late stages of the outburst, intermittent negative pressure of the gas at the antioutburst door appeared. The key technologies for the design of the antioutburst door and its disaster resistance mainly include that strengthen theoretical and experimental research on the formation mechanism of outburst shock waves in mines, the interaction mechanism between disaster shock loads and dampers, and the magnitude of disaster expected shock loads; optimize the structure of the antioutburst door size, the width of the contact surface between the air door and the door wall, the stress distribution of the air door under impact load, the design of the safety hole, and the locking device; and improve the disaster monitoring and alarm capabilities of the antioutburst door and collect changes in antioutburst door pressure in real time. The research results provide a theoretical basis and technical support for the optimization of the antishock performance of underground antioutburst doors in coal mines and have important practical significance for improving the disaster resistance of the ventilation system.

In this study, an indicator model and system for coal and gas outburst prediction are identified and established based on gas geological anomalies, mining stress, and gas emission characteristics. In this regard, the coal and gas outburst prevention techniques and mine rules in China are taken into account. In addition, using this model, an online integrated system and database for coal and gas outburst prediction were built for Xinjing Mine in Shanxi Province. The application results of the prediction system indicate that the system software and hardware can guarantee early warning of coal and gas outburst. The system is continuous and stable, and the early warning results are issued in a timely and accurate manner. The accuracy of the early warning results is high and consistent with the actual risk of the mine.

Coal and gas outburst is one of major dynamic disasters that have affected safety production in coal mines for many years, in which gas is an important factor that influence its intensity. To analyze the role of gas, especially the role of gas adsorption, in the dynamics of coal and gas outbursts, a self-developed experimental device for the measurement of the dynamic effects of coal and gas outburst was used to perform outburst experiments under different adsorption gas conditions. The device has a simulated roadway sub-system with a length of up to 50 m, which can collect and monitor the typical dynamic effect appearance characteristics such as the shock wave propagation and the pulverized coal distribution of the outburst. Based on the energy theory, we quantitatively discuss the effect of gas adsorption on the outburst. After the outburst occurred, the air in the roadway around the outburst port was disturbed by the shock wave, and the gas pressure rose and then fell within a very short period of time. The adsorption properties of the coal determined the intensity of coal and gas outbursts. The amount of outburst pulverized coal in the CO2 test condition was 3 times larger than that in the air test condition. Additionally, the particle size distribution of the coal samples did not change markedly during the test, indicating that the impact of the crushing effect on the pulverized coal was not significant during the outburst process under the action of gas only. The coal-gas transport energy was 3–5 orders of magnitude greater than the coal crushing energy and the remaining kinetic energy of the gas. It was verified that the role of gas in the outburst process principally related to throwing and carrying the broken coal in the roadway. The energy involved in the outburst process for the CO2 condition was approximately 5.8 times larger than the energy involved in the outburst process for the air condition, which was mainly due to the different adsorbed gas internal energies. The adsorption characteristic is one of key factors affecting the outburst energy and strength. These research results can provide guidance for perfecting coal and gas outburst mechanisms and developing outburst disaster early warning technologies.

Coal and gas outburst disasters affect safe production from coal mines. There has been limited progress in understanding and predicting these outbursts in the past years. Therefore, a novel large scale three-dimensional simulation experimental apparatus to study mechanisms of coal and gas outburst was developed. The experimental apparatus has dimensions of 1.5 m × 0.8 m × 0.8 m and can achieve a gas seal of 6 MPa. Its hydraulic sub-system can perform axial (3000 t) and horizontal symmetric (2000 t) loading. The outburst port can be initiated actively and instantaneously, similar to the sudden excitation of an outburst. The apparatus realizes the roadway network simulation of various fluid migration routes, resistance characteristics, and ventilation facilities. Simultaneously, 90 test channels and a sampling frequency of up to 4 Ms/s can be used to monitor the time–space distribution law of multiple parameters in the apparatus and realize the real-time observation of the experimental phenomena. The experimental apparatus can be used to simulate the entire process of the coal and gas outburst, including accumulation, motivation, development, and termination stages as well as systematically study the features and mechanisms of the outburst. A complete simulation experiment of an outburst under a high geo-stress was performed. The distribution and variation of the gas pressure and geo-stress before, during, and after the outburst were analyzed. The distribution of the outburst-pulverized coal and gas concentration rule was obtained, which shows the characteristics of the extrusion type. This experiment validates the capability and reliability of the newly developed coal and gas outburst simulation apparatus.

This article has selected Shanghai and Shenzhen A-share listed companies from 2004 to 2009 as a sample, adopted descriptive statistics and earnings stock return models tested the changes in accounting conservatism of companies before and after the implementation of new Chinese Accounting Standards. After analysis, some reforms in the new accounting standards, such as the transform of accounting objectives and the introduction of fair value measurement, will affect the accounting conservatism of enterprises. The result shows that: the implementation of the new accounting standards has reduced the accounting conservatism of enterprises.

Zhong-Jun Chen, Xu-Sheng Zhao, Tie-Ping Fan, Heng-Xu Qi, Di Li Neurological Intervention Department, Dalian Municipal Central Hospital, Dalian, Liaoning Province, People’s Republic of ChinaCorrespondence: Di LiNeurological Intervention Department, Dalian Municipal Central Hospital, Dalian, Liaoning Province, People’s Republic of ChinaTel +86 411-84412001-8481Email xiangqing14740@163.comPurpose: To explore the molecular mechanism of glycine in improving ischemic stroke.Patients and Methods: The serum samples of patients with ischemic stroke and healthy people were compared. The ischemic stroke model of PC12 cells was established by oxygen-glucose deprivation (OGD). qPCR quantified miR-19a-3p and AMPK mRNA, and protein expression was detected by Western blot. MTT was used to detect cell activity. Flow cytometry was used to detect cells. Glucose metabolism kit was used to detect glucose intake and formation amount of lactic acid.Results: Compared with the control group, OGD group (OGDG) showed lower cell activity and increased cell apoptosis. TNF-α, IL-1βI, L-6, Caspase 3, Caspase 9 and Bax were up-regulated, and Glut1, HK2, LDHA, PDK1, PKM2 and Bcl2 were down-regulated. At the same time, glucose intake, formation amount of lactic acid and cell apoptosis rate were reduced, and AMPK/GSK-3β/HO-1 pathway activity was down-regulated. Glycine could counteract the above phenomena in OGDG. miR-19a-3p and AMPK decreased and increased, respectively, during glycine therapy. AMPK was the target gene of miR-19a-3p. Rescue experiments demonstrated that glycine improved cell apoptosis, inflammatory response and glucose metabolism disorder of ischemic stroke through miR-19a-3p/AMPK/GSK-3β/HO-1 pathway.Conclusion: Glycine improves ischemic stroke through miR-19a-3p/AMPK/GSK-3β/HO-1 pathway.Keywords: ischemic stroke, AMPK/GSK-3β/HO-1 pathway, miR-19a-3p, glycine

Additional file 1. Materials and Methods.

In the present work, an industrial-scale experiment on ventilation air methane (VAM) utilization by a multibed thermal flow-reversal reactor (TFRR) is conducted in China. The influence of the inlet flow rate, feed methane concentration, and cycle time on the temperature distribution of the bed and heat recovery efficiency are investigated. The methane conversion in the studied cases exceeds 97%. The results show that the methane concentration during self-maintained operation of the TFRR without heat recovery should not be less than 0.22 vol % when the inlet flow rate is 103,000 Nm3/h and the cycle time is 300 s. As the inlet flow rate decreases, the lower concentration limit of automatic thermal maintenance increases. The peak temperature of the bed approaches the inlet side as the feed methane concentration increases and the cycle time decreases. The heat recovery efficiency increases linearly with increasing inlet flow rate, rises parabolically with an increasing feed methane concentration, and decreases weakly with increasing cycle time.

Coal and gas outburst is one of the major serious natural disasters during underground coal, and the shock air flow produced by outburst has a huge threat on the mine safety. In order to study the two-phase flow of a mixture of pulverized coal and gas of a mixture of pulverized coal and gas migration properties and its shock effect during the process of coal and gas outburst, the coal samples of the outburst coal seam in Yuyang Coal Mine, Chongqing, China were selected as the experimental subjects. By using the self-developed coal and gas outburst simulation test device, we simulated the law of two-phase flow of a mixture of pulverized coal and gas in the roadway network where outburst happened. The results showed that the air in the roadway around the outburst port is disturbed by the shock wave, where the pressure and temperature are abruptly changed. For the initial gas pressure of 0.35 MPa, the air pressure in different locations of the roadway fluctuated and eventually remain stable, and the overpressure of the outburst shock wave was about 20~35 kPa. The overpressure in the main roadway and the distance from the outburst port showed a decreasing trend. The highest value of temperature in the roadway increased by 0.25 °C and the highest value of gas concentration reached 38.12% during the experiment. With the action of shock air flow, the pulverized coal transportation in the roadway could be roughly divided into three stages, which are the accelerated movement stage, decelerated movement stage and the particle settling stage respectively. Total of 180.7 kg pulverized coal of outburst in this experiment were erupted, and most of them were accumulated in the main roadway. Through the analysis of the law of outburst shock wave propagation, a shock wave propagation model considering gas desorption efficiency was established. The relationships of shock wave overpressure and outburst intensity, gas desorption rate, initial gas pressure, cross section and distance of the roadway were obtained, which can provide a reference for the protection of coal and gas outburst and control of catastrophic ventilation.

The effect of VAM on reducing wilt caused by Fusarium oxysporum Schlecht. f.sp. fragariae Winks et Williams (FO) infection in strawberry and the possible mechanisms involved were investigated. Two key substances involved in disease defenses, lignin and hydroxyproline-rich glycoprotein were induced and formed in the cell wall of strawberry root, and the peak content of lignin and hydroxyproline-rich glycoprotein was obtained on the 25th day (149.52mg/g) and on the 15th day (10.08 mg/g), respectively. The activity of protective enzymes SOD, POD and CAT inoculation with VAM significantly increased when compared with the control under both CK (natural growth) and inoculated with FO. The conductivity of VAM plus FO treatment was higher than the CK treatment, but significantly lower than the FO treatment.

Windblown methane is an important gas resulting in atmospheric greenhouse effect. Therefore, reduction in windblown methane is one of the important measures to mitigate atmospheric greenhouse effect. In China, weak coal seam of low permeability is common in coal mines, so it is beset with difficulties to decrease the methane emission rate by means of gas drainage from the virgin coal seam, further to decrease the windblown mine gas. Utilizing the pressure relief and permeability and fluidity improvement effect in coal mining an approach to release methane emission through surface borehole was established, for example establishing a comprehensive deformation fracture model of surface borehole in extraction area based on quantitative rule of overlying rock movement in pit and forming a technology to select the surface borehole arrangement site in extraction area on the basis of deformation of bore frame structure and distribution characteristics of extraction flow field. And optimization technology of shape and structure of surface borehole in extraction area on the basis of ultimate stress analysis of surface borehole casing was given. The technology overcomes effectively the problem that surface borehole casing is vulnerable to premature fracture due to impact of strata movement on the surface borehole, and further increases the drainage result of the surface borehole. The technology has been test in China Shanxi Jincheng Sihe Coal Mine, achieving good results, including 12,000 Nm3/d pure methane drainage rate from single borehole, 85% methane concentration and 1.1 million Nm3 accumulative methane drainage, which demonstrate practicability and advanced performance of the technology.

Coal and gas outburst is an extremely complex and serious gas dynamic phenomenon. Therefore, building an early warning system based on computer system, safety monitoring systems of coal mines and local area network is a precondition for effectively preventing coal and gas outburst. Combining the hardware conditions, organization management structures and characteristics of preventing outburst technology systems, this paper discusses the principle, logic structure and implementation process of gas outburst warning, devises the software and hardware structure of the warning system and therefore offers theoretical thought and methods for the forecasting of coal and gas outburst.

The paper proposed the principle and approach of comprehensive early warning of coal and gas outburst. Objectively existing outburst risk of working face, defects of outburst prevention measures and management are the main source of danger of coal and gas outburst. Based on the opinion, the integrated index system of outburst early warning is established. According to relevant regulations, standards, and actual mine condition, the rule base models of comprehensive early warning of outburst were established, and the warning degree system is divided into two major categories: the state and the trend. Implementation method of the warning system was studied, and the software, hardware architecture and computer systems were built. The onsite trials and applications indicate that the comprehensive early warning system of coal and gas outburst can realize the intelligent advance warning of hazards, improve the mine management level of outburst prevention, and secure the mine production safety.

The risk of supporting wood fire induced by methane explosions in roadway was studied by doing some research on the mechanism of it. The thermal environment of methane explosions which include the characteristics of fire flame and the temporal and spatial thermal environment was studied. Based on the research of thermal environment, the fast pyrolysis of supporting wood was carried out by using fast pyrolysis apparatus. The experiment temperature is from 592∼1 313K, and the heat duration were 1s, 2s, 5s, 10s. Connected with combustion theory, the possibility of supporting wood fire induced by methane explosions was discussed from the following several aspects: fuel, combustion limit, the minimum combustion oxygen limit, and fire period. If the initial methane concentration is between 5.0∼9.25% with someone volume, then the sub-fire may occur at a certain distance from explosion source.

Division of coalbed methane (CBM)-enriched units primarily depends on the analysis of the main controlling factors of CBM occurrence. The main controlling factors analyzed in this article are sedimentary sequences related to the forming and alteration of CBM, tectonic movement, and burial and hydrocarbon-generation histories. The parameters were measured for independent quantities such as CBM content, gradient, coefficient of extraction difficulty and geological structure complexity. Correlation analysis was conducted between the measured parameters of CBM-bearing systems and the main controlling factors. When the controlling factors are sedimentary sequences and the sedimentary systems tract, the division of CBM-enriched units is based on the coal-forming environment, coal mass distribution and coal characteristics. When the controlling factor is the tectonic matching between the orefield, mining area and mining wells, the division of CBM-enriched units is based on tectonic movement. When burial and hydrocarbon-generation histories are the controlling factors, the division of CBM-enriched units is based on metamorphic traits.