Characteristics of electromagnetic vector field generated from rock fracturing

Rock fracturing is often accompanied by electromagnetic phenomenon.As a vector field,in addition to the intensity that is widely concerned,the generated electromagnetic field also has obvious direction-ality.To this end,a set of electromagnetic antennas capable of simultaneous three-axis measurement is used to monitor the electromagnetic vector field generated from rock fracturing based on Brazilian tests.The signal amplitude on each axis can represent the magnitude of actual magnetic flux density component on the three axes.The intensity and directional characteristics of electromagnetic signals received at different positions are studied using vector synthesis.The directionality of electromagnetic radiation measured using a three-axis electromagnetic antenna shows that the direction of the magnetic flux intensity generated by rock fracturing tends to be parallel to the crack surface,and the measured signal intensity is greater in a direction closer to the crack surface.

Experimental study on the infrared precursor characteristics of gas-bearing coal failure under loading

The stress and gas pressure in deep coal seams are very high,and instability and failure rapidly and intensely occur.It is important to study the infrared precursor characteristics of gas-bearing coal instability and failure.In this paper,a self-developed stress-gas coupling failure infrared experimental system was used to analyse the infrared radiation temperature(IRT)and infrared thermal image precursor characteristics of gas-free coal and gas-bearing coal.The changes in the areas of the infrared temperature anomalous precursor regions and the effect of the gas on the infrared precursors were examined.The results show that high-temperature anomalous precursors arise mainly when the gas-free coal fails under loading,whereas the gas-bearing coal has high-temperature and low-temperature anomalous precursors.The area of the high-temperature anomalous precursor is approximately 30%–40%under gasbearing coal unstable failure,which is lower than the 60%–70%of the gas-free coal.The area of the low-temperature abnormal precursor is approximately 3%–6%,which is higher than the 1%–2%of the gas-free coal.With increasing gas pressure,the area of the high-temperature anomalous precursor gradually decreases,and the area of the low-temperature anomalous precursor gradually increases.The highand low-temperature anomalous precursors of gas-bearing coal are mainly caused by gas desorption,volume expansion,and thermal friction.The presence of gas inhibits the increase in IRT on the coal surface and increases the difficulty of infrared radiation(IR)monitoring and early warning for gas-bearing coal.

AFM characterization of surface mechanical and electrical properties of some common rocks

The characterization of micro-surface mechanical and electrical properties of the natural rock materials remains inadequate,and their macroscopic performance can be better comprehended by investigating the surface properties.With this purpose,the present research focuses on characterizing the microsurface morphology,Derjaguin-Muller-Toporov(DMT)modulus,adhesion,and potential of granite,shale,and limestone by employing the atomic force microscope(AFM)as a pioneer attempt.The results show that the micro-surface morphology of the rock fluctuates within hundreds of nanometers,among which the granite micro-surface is comparatively the smoothest,followed by limestone.The morphology of the shale is the roughest,indicating that the regional difference of shale micro-surface is dominant.The distribution of the adhesion on rock micro-surface is uneven;the average adhesion of eight measuring areas for shale is 23.93 n N,accounting for three times of granite and limestone,while the surface DMT modulus of shale is relatively lower than granite and limestone.It is inferred from the obtained results that higher surface adhesion is helpful to the gas adsorption of shale,and the lower surface DMT(elastic)modulus is useful to the formation of fractures and pores.Thus,these two are the micromechanical basis of shale gas adsorption.Additionally,introducing a method to reduce the surface adhesion will benefit the exploration of unconventional resources such as shale gas.The micro-surface of the three types of rocks all shows electricity,with average potential ranging from tens of millivolts to hundreds of millivolts.Besides,the micro-surface potential of the rocks are heterogeneous,and both positive and negative points can be found.The existence and uneven distribution of micro-surface potential provide a robust physical basis for the electromagnetic radiation generated by rock fracture under loading.This study offers a new method for revealing the adsorption characteristics of unconventional gas reservoir rocks and the electromagnetic radiation mechanism of the rock fracture.

Early warning of coal dynamic disaster by precursor of AE and EMR"quiet period"

Efcient and accurate monitoring and early warning of coal dynamic disaster and other disasters can provide guarantee for the efcient operation of mine transportation system.However,the traditional threshold early warning method often fails to warning some accidents.To address above issues,a new early warning method was proposed based on"quiet period"phenomenon of AE and EMR during fracture.It is found that,a"quiet period"of AE and EMR was present before the load reaches the peak stress,which could be used as one of the precursors to warn the imminent failure of coal and rock specimens.MS and AE signals increased abnormally followed by the phenomenon of"quiet period"before the occurrence of coal dynamic disaster on site,and the decrease of MS events in the"quiet period"is about 57%–88%compared with that in previous abnormal increase stage.During the damage evolution of coal and rock,"quiet period"phenomenon usually occurred at 85%–90%of the peak stress,where the slope of damage parameter curve is almost zero.The"quiet period"of the AE-EMR signals and the low change rate of damage parameter before failure provide a theoretical foundation for the coal dynamic disaster warning based on the"quiet period"precursor found in MS-AE-EMR monitoring system.These fndings will help reduce the number of under-reported events and improve early warning accuracy.

A venom protein of ectoparasitoid Pachycrepoideus vindemiae, PvG6PDH, contributes to parasitism by inhibiting host glucose-6-phosphate metabolism

To achieve successful development,female parasitoids,while laying eggs,introduce various virulence factors,mainly venoms,into host insects to manipulate their physiology.Although numerous studies have been conducted to characterize the components of venoms that regulate host immune responses,few systematic investigations have been conducted on the roles of venom proteins in host metabolic regulation.In this investigation,we characterized a novel venom protein in Pachycrepoideus vindemiae called glucose-6-phosphate dehydrogenase(PvG6PDH)and showed it has a vital role in regulating host carbohydrate metabolism.PvG6PDH encodes 510 amino acids and features a signal peptide and two conserved“G6PDH”domains.Multiple sequence alignment showed it has high amino acid identity with G6PDH from other pteromalids,and quantitative polymerase chain reaction analysis and immunofluorescent staining demonstrated a significantly higher expression of PvG6PDH in the venom apparatus compared with the carcass.We report that PvG6PDH contributes to parasitism by inhibiting the glucose-6-phosphate(G6P)metabolism of host Drosophila melanogaster,as demonstrated by PvG6PDH injection and RNA interference analysis.Further tests revealed that the accumulation of host G6P was caused by the transcriptional inhibition of G6P-metabolism-related genes.These findings greatly contribute to our understanding of venom-mediated host metabolic regulation,further laying the foundation for the development of venom proteins as biological agents for pest control.