中国熟妇,亚洲国产AV一区二区,久久另类TS人妖一区二区,人妻去按摩店被黑人按中出

Coal mine gasexplosion underground,roof caving,flooding and otheraccidents have occurred from time to time.How toadvance goodprotection,after theloss to a minimum,how to achieve a betterrescue work,causes the ground totimely understand theundergroundscene of the accident,the implementation of theminerescue workcommand,emergency communicationsystem of coal minesecurity monitoringcan play a crucial role.The traditionalcoal minecommunication systemequipmenthas been using afixedexplosion-prooftelephone,its coverageis small,only callin the fixed-point,anddoes not have mobility,which makesan emergencydispatch commandcould not be completedin the first time,the mainresponsible person can not berushed to the scene to understandanddeal with the emergencyin the firsttime.However,the mine roadwayis a nonfree spaceradio wavesis fundamentalconstraintsin the transmissionof underground laneway,over the yearshas carried on the positive explorationand research of manydomestic and foreign experts and scholarsin this field.This paperuses thelong wave communicationprinciple inunderground mine mobile communicationsystem iswidely used.