简介:1(1)平面上已给1002个点,将连接每两点的线段中点染成红色.证明至少有2001个红点.(2)方程(2001x)2-2000×2002x-1=0的较大根为m,而方程x2+1999x-2000=0的最小根为n,求(m-n)的值.(江苏张家港职业高级中学周文国邮编:215600)
简介:Therehavebeenreportsformanyyearsthattheionosphereisverysensitivetoseismiceffects,andthedetectionofionosphericperturbationsassociatedwithearthquakes(EQs)attractsalotofattentionasaverypromisingcandidateforshort-termEQprediction.InthisreviewwepresentapossibleuseofVLF/LF(verylowfrequency(3-30kHz)/lowfrequency(30-300kHz))radiosoundingofseismo-ionosphericperturbations.Inordertoavoidtheoverlappingwithmyownpreviousreviews,wefirstshowsomepioneeringresultsfortheKobeEQandwetrytopresentthelatestresultsincludingthestatisticalevidenceonthecorrelationbetweentheVLF/LFpropagationanomalies(ionosphericperturbations)andEQs(especiallywithlargemagnitudeandwithshallowdepth),medium-distance(6-8Mm)propagationanomalies,thefluctuationspectraofsubionosphericVLF/LFdata(theeffectofatmosphericgravitywaves,theeffectofEarth’stides,etc.),andthemechanismoflithosphere-atmosphere-ionospherecoupling.Finally,weindicatethepresentsituationofthiskindofVLF/LFactivitiesgoingonindifferentpartsoftheglobeandwesuggesttheimportanceofinternationalcollaborationinthisseismo-electromagneticstudy.