利用锥上的度数理论考察了非线性项含有未知函数的一、二阶导数的弹性梁方程{u^(4)(t)=f(t,u(t),u'(t),u''(t)),0≤t≤1,u(0)=u'(1)=u''(1)=0的正解.在材料力学中,该方程描述了一类左端简单支撑、右端被滑动夹子夹住的弹性梁的形变.结论表明这个方程可以具有n个正解,只要非线性项在某些有界集上的“高度”都是适当的,其中”是一个任意的自然数.
By using the degree theory on cone, the positive solutions are considered for the following elastic beam equation {u^(4)(t)=f(t,u(t),u'(t),u''(t)),0≤t≤1,u(0)=u'(1)=u''(1)=0 where nonlinear term contains first and second derivatives of unknown function. In the mechanics of material, the equation describes the deformation of an elastic beam simply supported at left and clamped at right by sliding clamps. The results show that the equation may have n positive solutions provided the "heights" of nonlinear term are appropriate on some bounded sets. Here n is an arbitrary natural number.