Search

The enhanced coalbed methane (ECBM) technology has the potential to enhance coal seam gas extraction efficiency, while also achieving CO2 storage, thereby promoting the dual carbon reduction goals. It holds broad prospects for its application in unconventional natural gas development. The fracture structure and distribution within coal seams determine the effectiveness of supercritical carbon dioxide (SC-CO2) fracturing, which is pivotal in enhancing coal seam gas extraction efficiency. Under prolonged exposure, the adsorption swelling and dissolution-extraction effects generated by SC-CO2 interacting with coal can alter the morphology of coal fractures. However, during the fracturing process, the contact time between SC-CO2 and coal is relatively short, thus the impact of the adsorption swelling and dissolution-extraction effects of supercritical carbon dioxide on coal fractures under short-term conditions remains unclear. Therefore, this study investigated the evolution of coal fractures under a short-term SC-CO2 exposure. Different metamorphic coal samples were studied through CT scans to observe the variations in fractures with accumulated immersion time. A grayscale distribution function of CT two-dimensional scan images was established, and the relationship between immersion time and fracture evolution patterns was constructed. This was combined with the XRD experiments to examine the impact of immersion time on the changes in coal composition. The primary factors driving the evolution of coal fractures under a short-term SC-CO2 exposure were thus clarified. The results indicate that under a short-term SC-CO2 exposure, the adsorption-induced swelling leads to the contraction of coal fractures, while the dissolution-extraction effect causes the fractures to expand. During the coal immersion process, both the adsorption-induced swelling and the dissolution-extraction effect occur simultaneously, with their intensities changing over time. Within different time intervals, they alternately dominate the evolution of coal fractures. Different metamorphic coals affect the intensity and dominant time of adsorption expansion and dissolution extraction. The adsorption and expansion dominated when lignite was immersed for 30 min, and the dissolution and extraction increased and dominated when it was immersed for 90−240 min. The adsorption and expansion were stronger when bituminous coal was immersed for 30−90 min, and the dissolution and extraction were dominant when it was immersed for 90−240 min. Adsorption and swelling dominated when anthracite was immersed for 30−150 min, and dissolution and extraction dominated when it was immersed for 150−240 min.

To address the challenges of fracture recognition in the CT scanning images of coal or rock, particularly the interference of gangue and the recognition of fractures at different scales, proposed and implemented a network model for coal-rock fracture extraction based on deep learning (MCSN). According to the U-Net architecture, the model utilized its encoder-decoder structure and skip connections to segment the fracture structure images from complex coal-rock body images. Firstly, the fracture structures in the CT scanning images were annotated manually using the internal scan images captured by a coal industrial CT scanning system. And the annotated original data was augmented to create a coal-rock CT fracture dataset. Subsequently, to make the extraction network of main features have a stronger extraction capability of fracture structure features, the weights of a pre-trained VGG16 model were transferred to the U-Net encoder through a transfer learning technique. Simultaneously, the decoder part of the U-Net model was improved using the deep separable dilated convolutional modules (DCAC) and residual modules to effectively boost the recognition capability of fracture structures in the CT images, demonstrating a superior segmentation accuracy and robustness. To validate the effectiveness of the coal-rock fracture extraction network model proposed, the results obtained by the MCSN were compared with those of classical convolutional neural networks and threshold segmentation methods. Experimental comparisons revealed a significant advantage of the model proposed in both qualitative and quantitative analyses. The proposed model, employing a multi-scale fusion strategy, demonstrated the capability to effectively extract fractures in complex coal-rock images, thereby enhancing the efficiency and accuracy of fracture identification. The model was applied to the identification of fractures in roadway surrounding rock based on borehole imaging. Fracture extraction was performed through the analysis of borehole videos and planar unfolded images collected by a borehole imaging instrument. The results from both sources were cross-validated to obtain an accurate distribution of fractures in roadway surrounding rock. Furthermore, the model provides guidelines for the injection and sealing of boreholes, increasing volume fraction of coal seam gas extraction.

The supercritical carbon dioxide (SC-CO2) jet has a wide application prospect in drilling engineering, and its low coal breaking pressure threshold and high efficiency can improve drilling efficiency. But it has the problems of high coal breaking threshold pressure and system energy consumption, which limits its application. The high pulse pressure and resonance effect of the self-excited oscillation pulse SC-CO2 jet can effectively reduce the coal breaking threshold pressure and significantly improve the coal breaking efficiency. Based on this, the variation law and comprehensive effect of the self-oscillating pulse SC-CO2 jet pulse frequency and pulse pressure amplitude at different target distances were studied. Large eddy simulation was used to analyze the flow field structure of the jet, and the variation laws of the pulse frequency and pressure amplitude in the axial direction of the flow field were clarified. The effect of the target distance on the impact frequency and impact pressure of the jet was studied by pulse characteristics test experiment, and the comprehensive effect of pulse characteristics on coal breaking was studied by coal breaking experiment. It was concluded that the pulse frequency and pulse pressure amplitude of the self-oscillation pulsed SC-CO2 jet do not remain constant in the axial direction of the jet, and they gradually decrease with the increasing target distance. Considering only the pulse frequency cannot maximize the resonance effect, and it is necessary to comprehensively consider the influence of pulse frequency and pressure amplitude on the resonance effect. Using displacement response amplitude to characterize resonance effect can reflect the comprehensive influence of frequency and amplitude on resonance. When the target distance is small, from 0 mm to 15 mm, the main influencing factor of the displacement response amplitude is the pulse pressure amplitude. When the target distance is large, from 15 mm to 30 mm, the main influencing factor is pulse frequency. In addition, reducing the pulse frequency and increasing the pressure amplitude can effectively improve the displacement response amplitude. The transition positions of the main influencing factors of displacement response amplitude under different nozzle structure conditions are different, and the optimal target distance is also not the same. In this study, the optimal target distance for nozzle a is 22 mm, where the displacement response amplitude is the largest and the coal breaking effect is the best, while the optimal target distance for nozzle b is 26 mm.

The SC-CO2 jet drilling and completion technology can ensure the stability of coalbed methane wells, improve drilling speed and rock breaking efficiency, and has a wide application prospect. However, the high energy consumption and complex system of coal breaking limit its engineering application. The impact frequency of self-excited oscillation pulse SC-CO2 jet is the same as the natural frequency of coal and rock mass or satisfies the phase relationship, which can give full play to the resonance effect and achieve a better coal breaking effect. The nozzle structure is the key to affect the jet impact frequency. The existing frequency modulation method of self-resonating pulsed water jet is not suitable for the SC-CO2 jet. In order to realize the modulation of the impact frequency of the SC-CO2 jet, a large eddy simulation was used to study the influence law of different nozzle structures on the impact frequency of self-excited oscillation pulse SC-CO2 jet, and the influence degree of different nozzle structure parameters on jet impact frequency was obtained by weight analysis. The influence rule of nozzle structure on the jet impact frequency and the reliability of jet impact frequency modulation method are verified by jet impact frequency measurement experiment and coal breaking experiment. The results show that the diameter and length of the oscillating cavity, and the angle of the collision wall are the key factors affecting the jet impact frequency. The jet impact frequency can be substantially modulated by adjusting the structure of the oscillating cavity, so as to achieve the resonance effect. By adjusting the oscillating cavity structure, the jet impact frequency forms resonance with the inherent frequency of coal, then the coal breaking effect is significantly improved, and the smaller the resonance multiplier, the better the coal breaking effect of the jet, which can effectively improve the coal breaking efficiency. When the natural frequency of coal is 25 Hz, the outlet diameter of the upstream and downstream nozzle is set as 2.5 mm and 3.0 mm, and the diameter, length and angle of the oscillating chamber are adjusted to 10 mm, 3 mm and 120° respectively. The jet impact frequency reaches 25051.83 Hz, which is 1002.0 times of the natural frequency of coal and forms a resonance effect with the natural frequency of coal, effectively improves the coal breaking efficiency.

Cutter wear and frequent cutter change in hard rock tunneling are the main factors limiting an efficient tunneling. Low-pressure abrasive air jet assisted cutter rock breaking is a feasible idea to break through the bottleneck of rock breaking technology in hard rock tunnel. To achieve assisted high traverse speed cutter breaking, a rectangular nozzle was proposed. The rectangular nozzle can effectively improve the agglomeration of the abrasive in the moving direction, thereby reducing the cutting width，and improve the cutting depth. To clarify the influence of rectangular nozzle on abrasive acceleration and rock breaking, a circular nozzle and a rectangular nozzle were designed with approximately equivalent lengthening divergent section length and cross-section, and then the influence of nozzle divergent section length on gas and abrasive acceleration was determined based on numerical methods, and the influence of different cross-sectional shapes of nozzles on abrasive acceleration and distribution characteristics were comparatively analyzed. Finally, by carrying out the low-pressure abrasive air jet erosion crushing granite experiment, the influence of nozzle structure and traverse velocity on the erosion effect was studied, the cutting efficiency of nozzles with different cross-sectional shapes was analyzed, and the optimal nozzle structure suitable for rock breaking by assisted tools was determined. The numerical study results show that when the pressure is 2 MPa, the length of the divergent section is extended, the gas-solid two-phase energy conversion is more complete, and the abrasive acceleration is more sufficient, but with the continuous lengthening of the nozzle divergent section, the abrasive speed is not significantly increased. Compared with the circular nozzle, the rectangular nozzle is slightly worse at the abrasive acceleration, but it can still accelerate the abrasive to 300 m/s, and the abrasives accelerated by the rectangular nozzle are distributed flat and rectangular in the free flow basin, which effectively improves the agglomeration of the abrasive in the horizontal movement direction of the cutter. Experiments show that the divergent section of the circular nozzle is lengthened, and the erosion depth of rock is increasing, when the length of the divergent section is 145 mm, the erosion depth of granite is 23.90 mm and 20.23 mm, respectively, and the continuous lengthening of the divergent section length, and the erosion depth of rock is not significantly improved. When the traverse speed is 0.02 m/s, the cutting depths of basalt of nozzles C4, R1 and R2 are 3.35 mm, 12.15 mm and 8.25 mm, and the granite depths are 5.2, 14.9 and 11.5 mm, respectively. When the traverse speed is 0.30 m/s, the depths of basalt cutting by nozzles C4 and R1 are 0.8 mm and 3.0 mm, and the granite depths are 1.0 mm and 3.6 mm, respectively. Compared with the nozzle C4, the same as the numerical simulation results, the rectangular nozzle can make the abrasive energy concentrate, the abrasive utilization is fully utilized, and the cutting efficiency is better. And the cutting efficiency of nozzle R1 is the best, and the nozzle structure is the best. The research will provide theoretical and technical support for the abrasive air jet assisted cutter rock breaking.

Using an impact damage-percolation experimental system for gas-bearing coal or rock, the authors carry out various gas-bearing coal impact experiments with in-situ seepage tests to reveal the law of dynamic mechanical characteristics, fracture expansion, and permeability changes of gas-bearing coal under different impact loads and gas pressures loading. Using an industrial CT scanning system, the authors conduct a 3D reconstruction of the fracture structure in order to analyze the internal fracture expansion characteristics of gas-bearing coal and the influence law on gas permeation patterns. The results show that both the impact load and gas pressure play an important role in the dynamic mechanical properties, deformation process, fracture expansion, and gas permeation patterns of gas-bearing coal: ① Under the coupling of impact load and gas pressure, the stress-strain curve of gas-bearing coal has an inconspicuous compaction stage due to the influence of confining pressure and axial pressure. The deformation process of gas-bearing coal includes elastic deformation stage, strain strengthening stage, and failure stage. ② The increase of impact load will increase the dynamic mechanical parameter value of gas-bearing coal, while the increase of gas pressure will reduce the value. The greater the impact load, the higher the gas pressure, and the more sufficient the fracture expansion of gas-bearing coal. At the same time, the fracture structure is more complex. ③ The seepage law of gas-bearing coal is controlled by fracture expansion. Under the coupling of impact load and gas pressure, three types of gas flow exist in gas-bearing coal: pore flow, coexistence of pore flow and fracture flow, and fracture flow. After the impact failure of gas-bearing coal, the gas flow pattern can transition from pore flow to coexistence of pore flow and fracture flow, and eventually to fracture flow, as the gas pressure increases and the influence of gas wedges intensifies. Fracture expansion and flow patterns jointly affect the seepage law of gas-bearing coal. The permeability of gas-bearing coal generally exhibits a trend of initially increasing and then decreasing with the increase of gas pressure.

With the gradual implementation of China’s deep-earth engineering strategy, deep resource extraction and underground space construction have brought in some new opportunities, but they also face many challenges, with extreme geological conditions such as high geopathic stresses, high ground temperatures and hard rock bodies popping up all the time. Rock breaking technology is the main engineering activity for all resource extraction and underground space construction, and it is the main factor determining the construction process and engineering efficiency. Under extreme geological conditions, tool-based rock breaking technology has become a key technical bottleneck to affect the smooth implementation of deep-earth engineering strategy due to fast tool wear and low rock breaking efficiency. In order to solve the problem of high-efficiency rock breaking in deep-earth and to guarantee the smooth implementation of deep-earth engineering strategy, there is an urgent need for a revolutionary rock breaking technology. As an important supplement to the tool-based breaking technology, the non-tool rock breaking technology is a feasible solution to break through the bottleneck of the tool-based breaking technology. To this end, the non-tool rock breaking technology is summarized into three types of technological systems, namely, impact rock breaking, thermal stress rock breaking and erosion and abrasion rock breaking. Sixteen types of rock breaking technologies, such as water jets, lasers and abrasive air jets, etc., are systematically analyzed. Also, the history of the development of each technology and their technical principles are summarized, and the advantages of the rock breaking and the technological bottlenecks are analyzed. It is concluded that the main reasons why the current non-tool rock-breaking technologies are not widely used in resource extraction and underground space construction are high energy consumption, poor adoptability and complex technical equipment. Compared with tool-based breaking, non-tool breaking technology has a lower energy utilization rate for breaking rock. The specific energy consumption of water jet breaking is 40−70 times that of a tool breaking. Microwave, laser and plasma technologies require high-standard operation environment and cannot be applied in drilling, tunneling and other restricted and harsh environments. In order to solve the problem of rock breaking in extreme geological conditions, the idea of synergistic rock breaking by multiple non-tool rock breaking technologies is proposed, giving full play to the technological advantages of each non-tool rock breaking technology. The rock breaking concept of unloading high geo-stress by jet slit and breaking hard rock by particle impact volume is constructed to minimize the energy consumption of rock breaking, simplify the system equipment, and provide a theoretical support for the development of non-tool rock breaking technology.

Abstract With the application of new technologies for coal mine gas control, it has been increasingly urgent to apply the fixed‐point closed sampling (FPCS) technology for accurate measurement of coal seam gas content. In this study, gas desorption during FPCS was analyzed. In addition, gas desorption experiments and COMSOL simulations were conducted on coal particles. Furthermore, the gas desorption law during FPCS was compared with that under atmospheric pressure. The results show that Sun's formula can effectively characterize the gas desorption law during FPCS, and the i value remains unchanged when the gas desorption curve is fitted with Sun's formula. On this basis, a specific method for calculating gas loss during FPCS by using Sun's formula was proposed. The research findings are expected to provide a theoretical basis for accurate measurement of coal seam gas content by means of FPCS.

In actual coal mining operations, hazards like coal and gas outbursts pose significant threats to safety. Extracting coal seam gas through boreholes is the main method of coal mine gas disaster management. Currently, coal seam gas pressure often obtained through direct measurement in underground boreholes requires substantial human and material resources. Therefore, by integrating orthogonal experimental design (OED), random forest regression (RFR) algorithms and Bayesian optimization (BO), a model named OED–BO–RFR was proposed for predicting coal seam gas pressure during pre-drainage processes. The OED–BO–RFR model was tested against RFR, deep neural network (DNN) and support vector regression (SVR) models using a test dataset, revealing its substantial superiority in forecasting coal seam gas pressure during pre-drainage. Furthermore, analyzing the importance of various factors in the OED–BO–RFR model’s construction confirmed its scientific robustness and effectiveness. Subsequently, the OED–BO–RFR, RFR, DNN and SVR models were validated in situ for coal seam gas pre-drainage engineering. The OED–BO–RFR exhibited the best performance among the four models. These results demonstrate that the OED–BO–RFR model can swiftly and accurately predict gas pressure in borehole pre-drained coal seams, providing valuable insights and references for gas disaster management in coal mining enterprises.

Cement-based materials are the most commonly used grouting and sealing materials in underground coal mines, but due to the effects of stress perturbation as well as water loss and shrinkage of cementitious materials, the traditional cementitious materials are prone to regeneration cracks, which leads to the reduction of gas extraction rate in the boreholes. In order to reduce the influence of regenerated fissures on the gas extraction effect, a self-repairing cement sealing material is developed, which can realize the self-healing of fissures when the fissures are generated again at the grouting location. Firstly, the self-healing performance of self-healing cement under air conditions was studied through the fissure self-healing experiment, and a high-magnification measuring microscope was used to record the change rule of the fissure width over time. It was found that the self-healing cement was able to repair the fissure with the maximum width of 0.46 mm in 4 d under the natural air conditions. A large amount of white minerals were generated at the fissure, and the volume of repaired material still increased significantly in 14 d. After scraping off the repair products, white minerals were still generated. In order to further study the generation mechanism of the self-repair products, the microscopic morphology and microelement distribution of the two kinds of cements hydrated for 7 and 21 d were comparatively analyzed by SEM-EDS, and the physical phase information of the two kinds of cements was comparatively analyzed by XRD and Raman spectroscopy. The SEM-EDS results showed that, for the traditional cement, the needle-like and flocculent materials were cross-linked with each other and the overall structure was dense, whereas a large number of porous materials were distributed in the self-healing cement and the structure was relatively loose. Compared with the traditional cement, the mass fractions of four elements, C, Na, Al and Si, in the hydration products of the self-repairing cement were significantly higher. A large number of tightly arranged long strips are distributed on the surface of the fissure repair products, and the main elemental compositions are C, O, Na, and Ca. The XRD results showed that more diffraction peaks of unhydrated tricalcium silicate appeared in the self-healing cement compared with the traditional cement, and the hydration products of the traditional cement were mainly calcium hydroxide and calcium alumina for the same hydration time, while aluminosilicate minerals such as sodium feldspar and zeolite appeared in the self-healing cement. The fracture restorations consisted of various silicate minerals such as zeolite, calcium chalcocite and wollastonite as well as calcium carbonate, of which calcium carbonate had the highest number of diffraction peaks. The Raman spectral results showed that compared with the traditional cement, the self-healing cement had obvious Raman spectral peaks at 2860−2960 cm−1. At 7 d of hydration, the traditional cement Raman peaks were generally sharp, while the self-healing cement Raman peaks were significantly broader. More Raman peaks of high-intensity calcium hydroxide appeared in the traditional cement, while more Raman peaks of C—O vibration in \begin{document}$ {\rm{CO}}^{2-}_{3} $\end{document} appeared in the self-healing cement with larger peak area, which shows that the self-healing cement is more likely to react with CO2 in air to carbonize. At 21 d of hydration, the Raman peaks of both cements were sharp, and the main phases were hydrated calcium silicate and calcium hydroxide, while the self-healing cement also included a large amount of unhydrated tricalcium silicate. Finally, the effects of secondary hydration and carbonation on fracture self-healing were analyzed, and the equations for the generation of fracture repair products were deduced combining the experimental results.

In order to obtain the impact frequency of resonant coal breaking by self-excited oscillation pulsed supercritical carbon dioxide (SC-CO2) jet, large eddy simulation was used to analyze the formation and development process of self-excited oscillation pulsed SC-CO2 jet, the variation of jet impact frequency in the nozzle and the free flow field, and the variation of jet impact frequency at different positions in the jet axis and under different cavity lengths. The test device of jet impact frequency was developed, and experiments were performed to verify the conclusions of the numerical simulations. The results show that the frequency of the self-excited oscillation pulsed SC-CO2 jet is different in the nozzle and the free flow field. In the nozzle, the frequency generated by the fluid disturbance is the same, and the jet frequency at the exit of the nozzle is consistent with that inside the nozzle. In the free flow field, due to the compressibility of CO2, the pressure, velocity and other parameters of SC-CO2 jets have obvious fluctuation patterns. This feature causes the impact frequency of the self-excited oscillation pulsed SC-CO2 jet to decrease gradually in the axis. Changing the cavity length allows the adjustment of the jet impact frequency in the free flow field by affecting the disturbance frequency of the self-excited oscillation pulsed SC-CO2 jet inside the nozzle.

Using an impact damage-percolation experimental system for gas bearing coal or rock and an industrial CT scanning system, the authors design and carry out a series of dynamic compression-seepage tests for loading at different impact velocities under triaxial prestressed states and reconstruct the three-dimensional crevices structure of the impact-damaged sandstone in order to reveal the law of damage features and permeability of the gas bearing sandstone under different impact loads. The experimental results of dynamic stress-strain curve characteristics, energy dissipation laws, damage and permeability evolution features under different impact velocities loading of fluid-solid coupling sandstone samples show that as the impact loading velocity increases, the strain rate of the gas bearing sandstone increases. The incident wave energy, reflection wave energy, transmission wave energy and absorption energy increase simultaneously as well. The peak stress and peak strain of gas bearing sandstone increase with the impact velocity as well, and the compaction stage in the dynamic stress-strain curve is constantly compressed until it disappears completely. The failure form of gas bearing sandstone is mainly shear failure under the condition of triaxial static and gas-solid coupling. With the increase of impact velocity, the number of tensile cracks under the combination of impact load and gas pressure increases continuously. Poisson's ratio effect and eccentric compression form two types of tensile cracks along the axial direction or perpendicular to the sample. The two types of tensile cracks are connected along the outer edge of the specimen, showing a grid shape. Nascent cracks are interconnected, which drives macroscopic through cracks formation. The absorption energy of gas bearing sandstone directly determines the degree of damage. The increasing absorption energy not only increases the damage degree of gas bearing sandstone after damage, but also greatly improves the permeability. The permeability of gas bearing sandstone after impact damage follows a linear positive correlation with its crack rate.

Coal dust is one of the seven disasters in coal mine. It affects the health of workers and causes coal dust explosion. The wetting effect of coal has a great influence on dust removal. Studies have shown that the wetting effect of coal is related to the wettability, surface roughness and surfactants of coal. In order to effectively solve the problem of coal dust under the mines, which selects hydrophilic Hami lignite, hydrophobic Anyang coking coal and weakly hydrophilic anthracite of Zhaogu No.2 mine as the research objects. The mean square roughness of the three coal samples were measured by the optical contact angle morphology combined instrument, the intrinsic contact angles of the three coal samples were measured, the two-dimensional physical model was constructed by COMSOL numerical software, the simulation conditions were set, the simulation parameters were adjusted, the experimental and simulation values were analyzed and compared, the feasibility of COMSOL numerical simulation was verified, and the influence of coal surface roughness on coal surface contact angle was studied. The results show that the droplet spreading process, the droplet spreading velocity and the droplet spreading shape of numerical simulation are similar to those of experiment, but the simulated contact angle is larger than that of experiment. With the increase of coal surface roughness, the contact angle of lignite decreases from 60.7° to 50.9°, the variation range is about 10°, the contact angle of coking coal increases from 96.5° to 112.7°, the variation range is about 16°, and the contact angle of anthracite decreases from 89.7° to 78.3°, and the variation range is about 11°. The simulated and experimental values of contact angle of three kinds of coal samples with the same surfactant have the same change trend, but the simulated value is larger than the experimental value. It is feasible to study the influence of coal surface roughness on coal surface contact angle by numerical simulation. The wetting of coal surface affected by roughness conforms to Wenzel model. The existence of surfactant does not change the variation of contact angle with surface roughness of three coal samples.

Background Leptomeningeal metastasis (LM) is the most devastating complication of non-small cell lung cancer (NSCLC), and its incidence is increasing. There is currently no standard treatment for LM, and the efficacy of traditional intravenous drug treatment is low, making refractory LM a difficult problem. In this study, we evaluated the efficacy and safety of intrathecal chemotherapy (IC)-based regimens in patients with refractory LM. Methods We retrospectively enrolled NSCLC patients with confirmed LM who received IC and systemic therapy at the Second Affiliated Hospital of Nanchang University from December 2017 to July 2022. We analysed overall survival (OS), intracranial progression-free survival (iPFS), clinical response, and safety in these patients. Results A total of 41 patients were enrolled. The median number of IC treatments was seven (range: 2–22). Seven patients received intrathecal methotrexate, and 34 patients received intrathecal pemetrexed. Clinical manifestations related to LM improved after IC and systemic therapy in 28 (68.3%) patients. The median iPFS in the whole cohort was 8 months (95% confidence interval [CI]: 6.4–9.7 months), and the median OS was 10.1 months (95% CI: 6.8–13.4 months). Multivariate analysis of the 41 patients with LM using a Cox proportional risk model showed that bevacizumab was an independent prognostic factor in patients treated with combination therapy (p = 0.002; hazard ratio [HR] 0.240; 95% CI: 0.097–0.595). Poor ECOG performance status remained a significant predictor of poor prognosis for survival (p = 0.048; HR 2.560; 95% CI: 1.010–6.484). Myelosuppression was the major adverse event over all IC dose levels. There were 18 cases of myelosuppression, 15 cases of leukopenia, and nine cases of thrombocytopenia. Eleven patients had myelosuppression above grade 3, including four with thrombocytopenia and seven with leukopenia. Conclusions Combination therapy based on IC had good curative effects, was safe to use, and was associated with prolonged survival in NSCLC patients with LM. The use of bevacizumab is a good prognostic factor for NSCLC LM patients with combination therapy.

The present study aimed to develop low-sodium curing agents for dry-cured meat products. Four low-sodium formulations (SPMA, SPM, SP, and SM) were used for dry-curing meat. The physicochemical properties and flavor of the dry-cured meat were investigated. The presence of Mg2+ ions hindered the penetration of Na+ into the meat. The weight loss, moisture content, and pH of all low-sodium salt groups were lower than those of S. Mg2+ addition increased the water activity (Aw) of SPMA, SPM, and SM. Dry-curing meat with low-sodium salts promoted the production of volatile flavor compounds, with Mg2+ playing a more prominent role. Furthermore, low-sodium salts also promoted protein degradation and increased the content of free amino acids in dry-cured meat, especially in SM. Principal component analysis (PCA) showed that the low-sodium salts containing Mg2+ were conducive to improving the quality of dry-cured meat products. Therefore, low-sodium salts enriched with Mg2+ become a desirable low-sodium curing agent for achieving salt reduction in dry-cured meat products.

Abstract The variations of strain and permeability of coal were systematically studied through the physical simulation of N2 and water injection. The effects of fluid adsorption capacity and initial permeability on strain, permeability and the dominant effect of pore pressure were discussed. The adsorption strain and strain rate of coal during water injection are significantly higher than those during N2 injection. An edge of free adsorption exists in the early phase of N2 and water injection, which is related to fluid saturation. Within this boundary, the strain rate and pore pressure are independent. Moreover, the injection time of initial stage accounts for about 20% of the total injection time, but the strain accounts for 70% of the total strain. For water injection, this boundary is about half of water saturation of coal. Besides, the influence of pore pressure on permeability is complex, which is controlled by adsorption capacity and initial permeability of coal. When the initial permeability is large enough, the effect of adsorption strain on permeability is relatively weak, and the promoting effect of pore pressure on fluid migration is dominant. Therefore, the permeability increases with increasing pore pressure. When the initial permeability is relatively low, the pore pressure may have a dominant role in promoting fluid migration for the fluid with weak adsorption capacity. However, for the fluid with strong adsorption capacity, the adsorption strain caused by pore pressure may play a leading role, and the permeability reduces first and then ascends with increasing pore pressure.

Abstract The natural frequency of coal is one of the important technical parameters for the application of the permeability enhancement technology of coal and rock forced vibration. Aiming at exploring the dominant frequency of the permeability enhancement technology of coal vibration excited by vibration wave, the model of coal vibration excited by simple harmonic wave (SHW) was constructed. Furthermore, considering the three main control parameters, i.e., excitation force, coal sample size and mechanical parameters, the response characteristics of coal vibration excited by SHW were simulated and calculated. The calculation results demonstrate that when the frequency of excitation force equals the natural frequency of coal, the vibration occurs and the peak values of response parameters all increase significantly. The peak acceleration response of coal increases with the increase of excitation force, whereas it decreases with the increase of coal size. Under the same SHW excitation force, the mechanical parameters of coal determine the vibration response characteristics of coal, and the natural frequency of coal is proportional to the elastic modulus. Finally, the variation law of natural frequency response characteristics of coal vibration excited by SHW was verified by the response experiment on coal vibration under SHW excitation and related test results. The research results can serve as a theoretical basis for the application of the permeability enhancement technology of coal vibration excited by vibration wave.

Introduction: The initial velocity of gas diffusion (ΔP) of coal is an important index to characterize the outburst risk of coal, and temperature is an important factor affecting the determination of initial velocity of gas diffusion. However, how to control the temperature during ΔP determination remains a significant challenge. Methods: In this paper, an experimental system for ΔP testing under temperature-controlled conditions was constructed, and the effect of temperature on the ΔP determination results was further explored by accurately controlling the temperature of the testing system. Results: The results show that the temperature change will affect the determination result of ΔP in the range of 13°C–40°C, and the determination results do not show obvious regularity. Discussion: The main reasons for the analysis are as follows: during the determination of ΔP, although the higher the temperature is, the faster the speed of gas diffusion and the greater the amount of gas diffusion and the pressure produced in the first 60 s, but the smaller the amount of gas adsorption before release. There is a situation of mutual offset between the two, resulting in the fluctuation of ΔP determination results. It is concluded that the temperature change will affect the determination of the initial velocity of gas diffusion, and when ΔP is measured, the temperature of the experimental system should be consistent with the actual temperature of the sampled coal body as far as possible, so as to increase the reliability of the measured results for the prediction of coal and gas outburst. This paper provides an experimental basis for clarifying the industry standard of temperature related to ΔP.

Ice abrasive jet technology is a green and environmentally friendly process with wide application prospects in the field of surface treatment. Ice abrasive jets constitute an essential technical parameter of the process, and temperature affects the hardness of ice. Therefore, in this paper, we investigated the hardness of ice at different temperatures. The dynamic characteristics of ice at different temperatures were simulated using molecular dynamics methods, and the laws of the dynamic characteristics of ice with temperature were analysed. Hardness testing experiments were carried out to grade the hardness of ice and then linearly fitted the hardness versus temperature. The results show that as the temperature increased, the dynamic characteristics of ice changed correspondingly, and the intermolecular hydrogen bonds and van der Waals interactions of ice weakened. From a chemical perspective, with the increase in temperature the intermolecular force weakens, the lattice energy of the crystal decreases, the resistance required to destroy the crystal decreases, and the crystal exhibits low hardness. Temperature affects the hardness of ice by changing the strength of the intermolecular force. The experimentally measured ice hardness was classified into five classes, and the fit revealed a strong linear correlation between ice hardness and temperature. In this study, numerical simulations were performed and experimental results were analyzed to identify the effect of temperature on the hardness of ice by changing the force between ice molecules, which is crucial for improving the erosion efficiency of ice abrasive jets.

A. acidoterrestris has been identified as the target bacterium in fruit juice production due to its high resistance to standard heat treatment. Multiple studies have shown that cold plasma can effectively inactivate pathogenic and spoilage microorganisms in juices. However, we are aware of only a few studies that have used cold plasma to inactivate A. acidoterrestris. In this study, the inactivation efficacy of cold plasma was determined using the plate count method and described using a biphasic model. The effects of the food matrix, input power, gas flow rate, and treatment time on inactivation efficacy were also discovered. Scavenging experiments with reactive oxygen species (•OH, •O2−, and 1O2), scanning electron microscopy (SEM), Raman spectra, as well as an in vitro toxicology assay kit, were used to determine the inactivation mechanism. According to the plate count method, a maximum reduction of 4.14 log CFU/ mL could be achieved within 7 s, and complete inactivation could be achieved within 240 s. The scavenging experiments showed that directly cold plasma-produced singlet oxygen plays the most crucial role in inactivation, which was also confirmed by the fluorescence probe SOSG. The scanning electron microscopy (SEM) and Raman spectra showed that the cold plasma treatment damaged the membrane integrity, DNA, proteins, lipids, and carbohydrates of A. acidoterrestris. The plate count results and the apple juice quality evaluation showed that the cold plasma treatment (1.32 kV) could inactivate 99% of A. acidoterrestris within 60 s, with no significant changes happening in apple juice quality, except for slight changes in the polyphenol content and color value.

Coal seam gas content is frequently measured in quantity during underground coal mining operation and coalbed methane (CBM) exploration as a significant basic parameter. Due to the calculation error of lost gas and residual gas in the direct method, the efficiency and accuracy of the current methods are not inadequate to the large area multi-point measurement of coal seam gas content. This paper firstly deduces a simplified theoretical dynamic model for calculating lost gas based on gas dynamic diffusion theory. Secondly, the effects of various factors on gas dynamic diffusion from coal particle are experimentally studied. And sampling procedure of representative coal particle is improved. Thirdly, a new estimation method of residual gas content based on excess adsorption and competitive adsorption theory is proposed. The results showed that the maximum error of calculating the losing gas content by using the new simplified model is only 4%. Considering the influence of particle size on gas diffusion law, the particle size of the collected coal sample is below 0.25 mm, which improves the measurement speed and reflects the safety representativeness of the sample. The determination time of gas content reduced from 36 to 3 h/piece. Moreover, the absolute error is 0.15–0.50 m3/t, and the relative error is within 5%. A new engineering method for determining the coal seam gas content is developed according to the above research.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the corresponding author due to similarities identified with a previously published paper, 'Performance of a Low Energy Ion Source with Carbon Nanotube Electron Emitters under the Influence of Various Operating Gases', in Nanomaterials (Nanomaterials 2020, 10(2), 354; https://doi.org/10.3390/nano10020354). The author wishes to apologise for any confusion or inconvenience caused.

Cinnamic acid (CA) is a safe and effective antimicrobial agent. The objective of this study was to reveal the antibacterial mechanism of CA against a food-derived Pseudomonas fragi 38-8, from the aspects of bacterial growth kinetics, cell membrane homeostasis, cell microstructure, and transcription. The minimum inhibitory concentration (MIC) of CA against P. fragi 38-8 was 0.25 mg/ml. CA retarded bacterial growth and induced a series of cell membrane changes. After CA treatment, cell membrane homeostasis was destroyed, which was evidenced by cell membrane depolarization, intracellular pH reduction, and intracellular ATPase activity decrease. Field emission scanning electron microscope (FESEM), transmission electron microscope (TEM), and confocal laser scanning fluorescence microscope (CLSM) realized the visualization of cell microstructure changes, showing cell death and morphological changes, such as cell rupture, shrinkage, and hollowness. RNA sequencing analysis further confirmed the effects of CA to the cell membrane, because of the significant enrichment of differentially expressed genes (DEGs) related to membrane. The results of the phenotype tests and RNA-seq both focused on cell membrane damage, which showed that CA exerted antibacterial effect mainly by acting on cell membrane.

The difficulty in enhancing the low permeability of deep coal seams is the key problem restricting gas extraction. The technology of coal rock resonance and permeability enhancement excited by vibration wave is hailed as a new technology to enhance coal seam permeability. In particular, the effect of resonance and permeability enhancement is remarkable when the excitation frequency is exactly the same as the natural frequency of coal. In order to promote the application of the technology, the first step is to explore the variation characteristics of coal natural frequency and its influencing factors. In this study, two mathematical models of coal natural frequency were established, and the variations and influencing factors of coal natural frequency were discussed through an experiment on the natural frequency of coal. The results show that coal vibration has multiorder natural frequency which grows with the increase of the order. In addition, the natural frequency of coal is closely related to its elastic modulus, density, size, mass, stiffness, and other physical and mechanical parameters. The larger the coal size and mass are, the lower the natural frequency would be. The natural frequency parallel to the bedding plane is higher than that perpendicular to the bedding plane. For the saturated coal sample, moisture changes its density and reduces its elastic modulus. Consequently, its natural frequency is lower than that of the dried coal sample. The difference of organic matter and mineral content coal of different rank affects the physical and mechanical properties of coal, which leads to the difference in natural frequency of different-rank coals. The natural frequencies of different-rank coal show bituminous > anthracite > lignite. The natural frequencies of coal samples under different influencing factors are all tens of Hz. Thus, the vibration excitation of coal under the low-frequency condition is the focus of future research. The study can provide a theoretical basis for the technology of coal resonance and permeability enhancement excited by vibration wave.

Emergency management of coal mines requires enhanced synergy among departments, institutions, and enterprises, which means overall efficiency in management. In this study, a regional coal mine emergency (CME) management synergy system was established; the synergy theory was adopted to construct the order parameter index system of the regional CME management synergy subsystems. Moreover, the order degrees and synergistic degrees of the regional CME management synergy subsystems in Henan Province, China, in the period 2015-2019 were quantitatively measured and analyzed using the composite system synergy model. The results show that the order degrees of regional CME management synergy subsystems and the synergistic degree of the composite system increase overall during the inspection period. With the gradual formation of the regional CME management synergy mechanism, this period has witnessed a steady improvement in both the synergy value and the considerable synergistic effect.

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal).This article has been retracted at the request of the corresponding author due to similarities identified with a previously published paper, 'Performance of a Low Energy Ion Source with Carbon Nanotube Electron Emitters under the Influence of Various Operating Gases', in Nanomaterials (Nanomaterials 2020, 10(2), 354; https://doi.org/10.3390/nano10020354). The author wishes to apologise for any confusion or inconvenience caused.

Abstract Background The treatment strategy for brain metastasis (BM) in patients with epidermal growth factor receptor (EGFR) -mutant lung adenocarcinoma (LAC) remains controversial. In the present study, we compared the efficacy of brain radiotherapy (RT) in combination with tyrosine kinase inhibitors (TKIs) and TKIs alone for advanced LAC patients with EGFR mutations and BM. Methods We retrospectively studied 78 patients diagnosed with EGFR-mutant LAC who developed BM. These patients were divided into two groups: 49 patients in the combination treatment group who received brain RT in combination with EGFR-TKIs (including 23 patients with asymptomatic BM before RT); 29 patients in the TKI group who received EGFR-TKI targeted therapy alone (including 22 patients with asymptomatic BM before TKI treatment). Results The median intracranial progression-free survival (iPFS) of the combination treatment group was longer than that of the TKI alone group (21.5 vs. 15 months; P = 0.036). However, there were no significant differences in median progression-free survival (PFS, 12 vs. 13 months; P = 0.242) and median overall survival (mOS, 36 vs. 23 months; P = 0.363) between the two groups. Further analysis of asymptomatic BM showed that both the median iPFS and the mOS of the combination treatment group were significantly longer than for the TKI alone group (iPFS, 21.5 vs. 14.8 months, P = 0.026; mOS, 36 vs. 23 months, P = 0.041). Cox multivariate regression analysis found no independent adverse predictors of iPFS in all patients. Conclusions The synchronous combination of brain RT and TKIs was superior to EGFR-TKIs alone for EGFR-mutant LAC patients with BM. The combination treatment group exhibited longer iPFS, while the PFS and OS were not significantly different between the two groups. In addition, the combination treatment could result in better iPFS and OS in those with asymptomatic BM. Therefore, addition of brain RT was useful for intracranial metastatic lesions.

Abstract In order to supply benefits for safe production of coal underground and efficient exploitation of coalbed methane, a self‐developed gas seepage experimental device considering gas adsorption and desorption was proposed to study the seepage properties of gas‐saturated coal in this paper. A series of gas seepage experiments under different loading conditions were carried out to investigate the change rules of permeability of gas‐saturated coal. The experimental results covered the significant effects of confining pressure, gas pressure, temperature change, creep stress, and complete stress‐strain process on the seepage laws of gas‐saturated coal. The experimental results showed that the permeability of gas‐saturated coal is strongly sensitive to the effective stress and decreases with the increase of the effective stress. Under the fixed confining pressure, the permeability of gas‐saturated coal showed an obvious Klinkenberg effect, but the Klinkenberg effect would no longer be evident once the gas pressure was larger than 1.0 MPa. And the change law of permeability of gas‐saturated coal with temperature was mainly reflected in the comprehensive effect of thermal stress and effective stress on the control of pore deformation. Under the complete stress‐strain loading conditions, the change rules of permeability were mainly dependent on the failure mode of gas‐saturated coal. And the change rules of permeability, for the condition of triaxial creep stress, were relied on the stage of creep deformation. The deformation at decay creep stage was responsible for a steady permeability after the failure of gas‐saturated coal, while the deformation at nondecay creep stage was responsible for a rapid increase of permeability after the failure of gas‐saturated coal. The results in this work can offer some helpful suggestions for efficiently exploring coalbed methane in the future.

Extensive research efforts have been made to address the motion control of rigid-link electrically-driven (RLED) robots in literature. However, most existing results were designed in joint space and need to be converted to task space as more and more control tasks are defined in their operational space. In this work, the direct task-space regulation of RLED robots with uncertain kinematics is studied by using neural networks (NN) technique. Radial basis function (RBF) neural networks are used to estimate complicated and calibration heavy robot kinematics and dynamics. The NN weights are updated on-line through two adaptation laws without the necessity of off-line training. Compared with most existing NN-based robot control results, the novelty of the proposed method lies in that asymptotic stability of the overall system can be achieved instead of just uniformly ultimately bounded (UUB) stability. Moreover, the proposed control method can tolerate not only the actuator dynamics uncertainty but also the uncertainty in robot kinematics by adopting an adaptive Jacobian matrix. The asymptotic stability of the overall system is proven rigorously through Lyapunov analysis. Numerical studies have been carried out to verify efficiency of the proposed method.

Emergency management of coal mines requires enhanced synergy among departments, institutions, and enterprises, which means overall efficiency in management. Their synergy can effectively lower the cost of emergency management, improve the effectiveness of it, and build a strong joint force for the prevention and control of emergencies. Accordingly, this study established a synergy system for regional coal mine emergency management and analyzed the interest relationship among key stakeholders in the system. Then, it established differential game models of the management synergy, explored the selection process of the behavior strategy of each stakeholder under different situations, and provided important tools for quantitative analysis on emergency management synergy practice. Furthermore, numerical simulation was carried out to analyze the influencing factors of their decision behaviors. The research results are of great significance for the comprehension of the evolution mechanism for the emergency management synergy of coal mines, the assistance for the government in determining the optimal method in emergency management synergy, the mobilization of the stakeholders, and the improvement of the current situation of emergency management synergy of coal mines in China.

The osmotolerant Zygosaccharomyces rouxii is known for its trait to survive in extreme high sugar environments. This ability determines its role in the fermentation process and leads to yeast spoilage in the food industry. However, our knowledge of the gene expression in response to high sugar stress remains limited. Here, we conducted RNA-sequencing (RNA-seq) under different sugar concentrations of the spoilage yeast, Z. rouxii, which exhibit extremely high tolerance to sugar stress. The obtained differentially expressed genes (DEGs) are significantly different to that of the Saccharomyces cerevisiae, which is sensitive to extreme high sugar stress. Most of the DEGs participated in the “glucan synthesis,” “transmembrane transport,” “ribosome,” etc. In this work, we also demonstrated that the gene ZYRO0B03476g (ZrKAR2) encoding Kar2p can significantly affect the growth of Z. rouxii under high sugar stress. In addition, we combined with a previous study on the genome sequence of Z. rouxii, indicating that several gene families contain significantly more gene copies in the Z. rouxii lineage, which involved in tolerance to sugar stress. Our results provide a gene insight for understanding the high sugar tolerance trait, which may impact food and biotechnological industries and improve the osmotolerance in other organisms.

To understand the effects of thermal shock on microcrack propagation and permeability in coal, thermal shock tests were conducted on coal specimens by using a constant temperature drying oven (105 °C) and a SLX program controlled cryogenic tank. The growth and propagation of microcracks were measured with computer tomography (CT) scanning and scanning electron microscope (SEM) tests. Results showed that thermal shocks improved the permeability of coal significantly. Notably, the permeability of coal after thermal shocks increased from 211.31% to 368.99% and was positively correlated with temperature difference. CT scanning images revealed that thermal shocks increased the crack number, crack volume and crack width as well as smoothened and widened the gas flow paths, thereby enhancing coal permeability. Moreover, SEM images showed that heating-cooling shocks created more new microcracks, forming more complex crack propagation paths and better connectivity among microcracks in coal compared to cooling shocks. We proposed a crack propagation criterion for coal to explain the mechanism of crack failure and propagation during thermal shocks. Our experiment results and theoretical analysis indicate that the heating-cooling shock is more effective in damaging and breaking coal than the cooling shock. Thus, it can be used as an alternative approach to enhance coal permeability in the production of coalbed methane (CBM).

Coal and gas outburst during underground mining operations negatively affects the mining safety and decrease the mining productivity. Current outburst prediction has been largely relying on seismic monitoring which is passive and extremely difficult to quantify. As coal produces radon in the damage process, this unique feature potentially offer a new way to reliably predict the outburst incidents. Therefore, in this study, a series of experiments were carried out under different gas pressures adopting the new coal-rock triaxial-loading radon exhalation test system, which aim to investigate the effect of gas depletion pressures on the characteristics of radon exhalation. The data of stress-strain, radon concentration, and acoustic emission were monitored simultaneously in the dynamic loading processes, and were compared and discussed in detail. Experimental results show that in the loading process, radon concentration shows clear step changes and has good consistency with the results of the coal deformation stages according to the acoustic emission count, verifying the feasibility of coal deformation and fracturing prediction based on radon concentration. Meanwhile, at the early stage of loading, the peak value of radon concentration reduces gradually with the increase in gas pressure. Furthermore, relationship between the maximum value of radon concentration and gas pressure is obtained. This work presents a new method to link gas pressure, coal deformation and fracture prediction together based on radon concentration, which could provide significant guidance for the accurate prediction of coal and rock dynamic disasters. Keywords: Radon exhalation, Coal damage, Acoustic emission counts, Radon concentration, Gas pressure

A polyclonal antibody-based indirect ELISA for the sensitive and specific detection of osmotolerant Zygosaccharomyces rouxii was established. The reactivity of the polyclonal antibodies (pAbs) with Z. rouxii was confirmed by immunofluorescence. The ELISA detection limit was 5 × 104 CFU/mL. For an evaluation of the specificity of pAbs, reactivity to 10 fungi species and 2 bacteria species commonly found in food environments was analysed by indirect ELISA. ELISA reacts with all tested Z. rouxii, whereas no cross-reactions or weakly reactions with 9 fungi and 2 bacteria were observed. The immunoassay staining confirmed the ELISA. Further on, the assay applicability was tested with concentrated apple juice, wine, and honey. Food samples were inoculated with 100 CFU/mL of Z. rouxii. After enrichment for 24 h, the established ELISA can successfully detect contaminated wine and concentrated apple juice samples, while only 30 h was required for honey samples.

In this study, a cylindrical triode ultrahigh vacuum ionization gauge with a screen-printed carbon nanotube (CNT) electron source was developed, and its metrological performance in different gases was systematically investigated using an ultrahigh vacuum system. The resulting ionization gauge with a CNT cathode responded linearly to nitrogen, argon, and air pressures in the range from ~4.0 ± 1.0 × 10−7 to 6 × 10−4 Pa, which is the first reported CNT emitter-based ionization gauge whose lower limit of pressure measurement is lower than its hot cathode counterpart. In addition, the sensitivities of this novel gauge were ~0.05 Pa−1 for nitrogen, ~0.06 Pa−1 for argon, and ~0.04 Pa−1 for air, respectively. The trend of sensitivity with anode voltage, obtained by the experimental method, was roughly consistent with that gained through theoretical simulation. The advantages of the present sensor (including low power consumption for electron emissions, invisible to infrared light radiation and thermal radiation, high stability, etc.) mean that it has potential applications in space exploration.

As natural occurring antimicrobial substances, phenolic compounds have been used to inhibit various bacteria. Stenotrophomonas maltophilia 4–1, a strain isolated from food, exhibited spoilage potential in vitro with proteolysis and lipolysis at 25°C. The present study evaluated the antibacterial properties of 13 polyphenols on S. maltophilia 4–1, and selected 6 compounds (ferulic acid, p-coumaric acid, caffeic acid, chlorogenic acid, (−)-epigallocatechin, and phloretin) for binary combination treatments. The results revealed that antibacterial activities of polyphenols were structure-dependent, and cinnamic acid showed strong inhibitory effects, with a minimum inhibitory concentration (MIC) of 0.125 mg/mL. Importantly, we did not observe any obvious synergistic effects across all binary combinations. The antibacterial mechanism of cinnamic acid was related to membrane damage, caused by the loss of cell membrane integrity and alteration of cell morphology. These findings suggest that cinnamic acid is a promising candidate for the control of spoilage bacteria in food.

Coal and gas outburst is a common coal-rock dynamic disaster. Such accidents frequently occur, and the mechanism underlying the occurrence of these outbursts is complex. As a typical failure mode of a gas-filled and pressure-relieved coal body, the spallation mechanism should be investigated to reveal the mechanism of coal and gas outburst and guide outburst-prevention strategies. In this paper, a fluid-solid coupling model for coal seam gas flow is established. This model considers the adsorption characteristics of coal. Numerical calculations are used to simulate the stress field distribution and evolution of gas-filled coal bodies under different boundary conditions. The mechanical mechanism of the spallation occurrence after the pressure relief of coal is explained from the perspective of seepage breaking coal. The control of the flow and stress state of the gas to the spallation failure is analyzed. The mechanical-quantitative conditions for the initial failure of the coal body under seepage and the mechanical-qualitative conditions for the continuous advancement and termination of spallation are studied based on numerical solution results. The numerical calculation results show that the formation of a flow field after pressure relief will apply a drag force (tensile stress) on the porous media of coal. The presence of this force plays a crucial role in promoting the spallation and cracking of coal and, thus, the promotion of spallation. The tensile strength, initial adsorption pressure, and pressure relief rate of the coal body jointly control whether the initial failure can occur and the thickness of the fracture layer cracks. Spallation propulsion is mainly determined by the pressure relief conditions of the undestroyed coal body and pressure changes in the spallation space; the former can be quantitatively obtained by numerical calculations, whereas the latter is related to the thickness of the spalled layer and the degree of the layer-crack structure.

The existing erosion models of abrasive gas jet tend to neglect the effects of the rebounding abrasive. To address this shortcoming, abrasive wear tests were conducted on limestone by using an abrasive gas jet containing different types of particles and with different standoff distances. The results indicate that erosion pits have the shape of an inverted cone and a hemispherical bottom. An annular platform above the hemispherical bottom connects the bottom with the side of the pit. The primary cause of the peculiar pit shape is the flow field geometry of the gas jet with its entrained particles. There is an annular region between the axis and boundary of the abrasive gas jet, and it contains no abrasive. Particles swirling around the axis form a hemispherical bottom. After rebounding, the abrasive with the highest velocity enlarges the diameters of both the hemispherical bottom and erosion pit and induces the formation of an annular platform. The surface features of different areas of the erosion pit are characterized using a scanning electron microscope (SEM). It can be concluded that the failure modes for different locations are different. The failure is caused by an impact stress wave of the incident abrasive at the bottom. Plastic deformation is the primary failure mode induced by rebounding particles at the sides of the hemispherical bottom. The plastic deformation induced by the incident abrasive and fatigue failure induced by the rebounding abrasive are the primary failure modes on the annular platform. Fatigue failure induced by rebounding particles is the primary mode at the sides of the erosion pits. The rock failure mechanism that occurs for particles with different hardness is the same, but the rock damaged by the hard abrasive has a rougher surface.

Determining the width of the stress relief zone on roadway surrounding rocks is the premise to optimize drilling borehole effect and increase gas extraction efficiency. In this study, a new width measurement method of the stress relief zone on the roadway surrounding rocks was proposed, which determined the width according to gas pressure attenuation speeds in roadway boreholes at different depths. Then, the variation curve of the gas pressure in boreholes at different depths with the time was gained through a field test. On this basis, laws of the gas pressure attenuation and the gas transmission and loss in boreholes at different depths were explored through a numerical simulation based on COMSOL Multiphysics, thus concluding the stress on roadway surrounding rocks, the distribution of plastic zones, and the stress-permeability relation. The scientificity of the proposed method was illustrated theoretically. Finally, the proposed method was verified by the field test data and numerical simulation results of the gas extraction at different sealing depths. Research results demonstrate that the pressure in boreholes attenuates in the logarithmic function pattern. The attenuation speed decreases with the increase of the drilling depth. The width of the stress relief zone on roadway surrounding rocks in the studied area was determined to be about 11 m according to the proposed method. Both the numerical simulation and the field test of the gas extraction efficiency prove the feasibility and validity of the proposed method in determining the sealing depth of the borehole for the gas extraction. Research conclusions are of important significance to enrich width measurement methods of the stress relief zone on roadway surrounding rocks and to optimize sealing parameters of underground boreholes for gas extraction.

Alicyclobacillus acidoterrestris is a major putrefying bacterium that can cause pecuniary losses in the global juice industry. Current detection approaches are time-consuming and exhibit reduced specificity and sensitivity. In this study, an immunoproteomic approach was utilized to identify specific biomarkers from A. acidoterrestris for the development of new detection methods. Cell surface-associated proteins were extracted and separated by 2-D (two-dimensional) gel electrophoresis. Immunogenic proteins were detected by Western blot analysis using antisera against A. acidoterrestris. Twenty-two protein spots exhibiting immunogenicity were excised and eighteen of the associated spots were successfully identified by matrix-assisted laser desorption/ionization time-of-flight tandem mass spectrometry (MALDI-TOF/TOF MS). These proteins were observed to be involved in energy and carbohydrate metabolism, transmembrane transport, response to oxidative stress, polypeptide biosynthesis, and molecule binding activity. This is the first report detailing the identification of cell surface-associated antigens of A. acidoterrestris. The identified immunogenic proteins could serve as potential targets for the development of novel detection methods.

The antioxidant capacity (AC) and antioxidant activity (AA) of three flavonols (FLV), aglycones and their glycosylated derivatives were evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays in various solvents. Findings confirmed that the glycosylation at the 3-position (3-glycosylation) always decreased the AC under most conditions due to substitution of the 3-position hydroxyl group and glycoside disruption in the molecular planarity. The 7-glycosylated derivatives did not have the above effects, thus generally exhibited ACs similar to their aglycones. Glycosylation decreased the AA of kaempferol and isorhamnetin for both assays in methanol, 3-glycosylation inhibited quercetin AA in the ABTS assay. In the DPPH assay, the AA of 3-glycosylated quercetin was significantly higher than quercetin. Using LC–MS/MS analysis, we found that quercetin and quercetin-7-glucoside underwent dimerization during the antioxidant reaction, potentially leading to a decline in AAs. However, 3-glycoside substitution may have hindered dimer formation, thereby allowing the FLVs to retain strong free radical scavenging abilities.

Separation of CO2/CH4/N2 is significantly important from the view of environmental protection and energy utilization. In this work, we reported nitrogen (N)-doped porous carbon spheres prepared from sustainable biomass glucose via hydrothermal carbonization, CO2 activation, and urea treatment. The optimal carbon sample exhibited a high CO2 and CH4 capacity, as well as a low N2 uptake, under ambient conditions. The excellent selectivities toward CO2/N2, CO2/CH4, and CH4/N2 binary mixtures were predicted by ideal adsorbed solution theory (IAST) via correlating pure component adsorption isotherms with the Langmuir−Freundlich model. At 25 °C and 1 bar, the adsorption capacities for CO2 and CH4 were 3.03 and 1.3 mmol g−1, respectively, and the IAST predicated selectivities for CO2/N2 (15/85), CO2/CH4 (10/90), and CH4/N2 (30/70) reached 16.48, 7.49, and 3.76, respectively. These results should be attributed to the synergistic effect between suitable microporous structure and desirable N content. This report introduces a simple pathway to obtain N-doped porous carbon spheres to meet the flue gas and energy gas adsorptive separation requirements.

In this study, a new coal-dust polymer composite material (CP) was fabricated to improve the borehole gas drainage effect and address the limitations of traditional sealing materials. This material used coal dust generated during underground drilling construction as filler, amino resin as binder, and also some other additives. Based on the orthogonal test scheme, 16 groups of experiments were conducted to investigate the effects of coal-dust content, water-material ratio, and cross-linking agent content on viscosity, 3-day (3-d) compressive strength, and gel time of the CP. The influences of the various factors were studied using a range of analytical methods to obtain the optimal proportion of the CP. Moreover, the mechanical property and microstructure of the CP were also analyzed to evaluate the sealing performance of this material. Results showed that this material exhibited obvious plastic characteristic and could provide an effective support for the borehole; it can adapt to the deformation of the borehole to some extent and achieve a long-term sealing effect. The scanning electron microscopy (SEM) results show a good correlation between the resin molecules and coal dust inside the material, which were conducive to improve the sealing performance of the CP material.

A laboratory test was conducted to investigate the effect of the freeze-thaw action of liquid nitrogen on the pore structure and permeability of coal rock. First, coal rock samples with similar sound velocities and permeabilities were selected. These samples were prepared in different water saturation levels and subjected to nuclear magnetic resonance (NMR) test before and after the freeze-thaw action. Furthermore, the freeze-thaw cycle of liquid nitrogen, freezing time, and water saturation of coal rocks were controlled in permeability test. Results showed that the pore diameter, porosity, and permeability of the coal rocks increase after the freeze-thaw action of liquid nitrogen. These characteristics increase further with the increase of water saturation. The fracturing mechanisms of the freeze-thaw action of liquid nitrogen were summarized in two aspects, phase change of pore water and cold shock, and cold shock was mainly discussed. The results indicate that the effect of cold shock is still crucial at low water saturation, but it is limited by the degree of temperature drop. In general, freeze-thaw action of liquid nitrogen can cause damage to pore structure, promote the formation of fracture networks, and consequently improve the permeability of coal rock.

Although the impact of Karst Collapse Pillars (KCPs) on water inrush has been widely recognized and studied, few have investigated the fluid-solid interaction, the particles migration inside KCPs, and the evolution feature of water inrush channels. Moreover, an effective approach to reliably predict the water inrush time has yet to be developed. In this work, a suite of fully coupled governing equations considering the processes of water flow, fracture erosion, and the change of rock permeability due to erosion were presented. The inverse velocity theory was then introduced to predict the water inrush time under different geological and flow conditions. The impact of four different controlling factors on the fracture geometry change, water flow, and inrush time was discussed in detail. The results showed that the inverse velocity theory was capable of predicting the occurrences of water inrush under different conditions, and the time of water inrush had a power relationship with the rock heterogeneity, water pressure, and initial particle concentration and an exponential relationship with the initial fracture apertures. The general approach developed in this work can be extended to other engineering applications such as the tunneling and tailing dam erosion.

Separation of impurities (CO2 and N2) from CH4 is an important issue for natural gas alternatives (such as coalbed gas, biogas, and landfill gas) upgrading. It is notably challenging to synthesize high N-doped porous carbon with an appropriate porous structure. In this work, high N content (14.48 wt %) porous carbon with micropore size of 0.52 and 1.2 nm and specific surface area of 862 m2 g−1 has been synthesized from potassium hydroxide (KOH) activated waste wool upon the urea modification. Pure component adsorption isotherms of CO2, CH4, and N2 are systematically measured on this enhanced N-doped porous carbon at 0 and 25 °C, up to 1 bar, to evaluate the gases adsorption capability, and correlated with the Langmuir model. These data are used to estimate the separation selectivities for binary mixtures of CO2/CH4 and CH4/N2 at different mixing ratios according to the ideal adsorbed solution theory (IAST) model. At an ambient condition of 25 °C and 1 bar, the predicted selectivities for equimolar CO2/CH4 and CH4/N2 are 3.19 and 7.62, respectively, and the adsorption capacities for CO2, CH4, and N2 are 2.91, 1.01, and 0.13 mmol g−1, respectively. This report introduces a simple pathway to obtain enhanced N-doped porous carbon with large adsorption capacities for gas separation of CO2/CH4 and CH4/N2.