精品一区二区视频舒服啊流水了使劲_AV激情亚洲人AV天堂18禁_在线观看污雏妓短视频_国产高清无乱码在线播放_国产免费一级成人AV

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.