简介:Basedonthesphericalcavityexpansiontheoryintheelastichalfspace,thegroundsurfacemovementcharacteristicsofshallowlyburiedexplosionsareanalyzed.TheresultsshowthattheinducedseismicwaveisalongitudinalwaveinthenearzoneandaRayleighwaveinthefarzone.Themaximumdisplacement(velocity)ofthelongitudinalwaveandtheRayleighwaveareinverselyproportionaltothescaleddistance,andcanbedescribedbyexponentialfunctionwithexponentsequalto1.4and0.5,respectively.Thevibrationfrequenciesofthewaveshavealmostnochange.Thevibrationfrequencyofthelongitudinalwaveapproximatesthenaturalvibrationfrequencyofthecavityinthebrokenarea,andthevibrationfrequencyoftheRayleighwaveisabouthalfthatofthelongitudinalwave.Onthesamereducedburieddepthandreduceddistance,theparticledisplacementisdirectlyproportionaltotheproductoftheboundaryloadingandcavityradius,andisinverselyproportionaltothetransversalwavevelocity.Meanwhile,theparticlevelocityisdirectlyproportionaltotheboundaryloadingandinverselyproportionaltothewavevelocityratio.Inthefarzone,theburieddepthoftheexplosiveonlyhasaslighteffectonthelongitudinalwave,buthasalargereffectontheRayleighwave.
简介:“教学恐惧”人皆有之现实中,我们可以看到一种现象:不少教师,一听到别人要来听自己的课,就不免有所抵触,有时甚至害怕和不情愿。对于类似现象,不少人简单地以教师素质论之,甚至由此断定该教师平日上课有问题,或对领导、同事态度有问题。其实,此论有失偏颇。按照《教学勇气》一书作者帕尔默的说法,这应该是一种“教学恐惧”。帕尔默曾说:“我虽然教了30多年学,至今却仍感到恐惧无处不在。走进教室,恐惧在那里;我问个问题,而我的学生像石头一样保持沉默——恐惧在那里;每当我感到似乎失控,诸如让难题难住,出现非理性冲突,或上课时因为我自己不得要领而把学生弄糊涂,恐惧又在那里。当一节上得糟糕的课出现一个顺利结局时,在它结束很长时间内我还恐惧——恐惧我不仅是一个水平低的教师,还是一个糟糕的人。”这种感受,大多数教师都会有同感。