研究非线性三阶两点边值问题u′′′(t)+λf(t,u(t))=0,00为正参数,非线性项f(t,u)为Caratheodory函数并且可以下方无界。利用Fatou引理和锥上的Krasnosel’skii不动点定理证明了一个正解存在定理。该定理不要求极限limu→+∞f(t,u)/u=+∞在闭区间[α,β]上几乎一致成立。因此改进了前人的结论。
The nonlinear third-order two-point boundary value problemuu′′′(t)+λf(t,u(t))=0,0t1,u(0)=u′(0)=u(1)=0is studied,where λ0 is a positive parameter,the nonlinear term f(t,u) may be Caratheodory function and may be unbounded below.By applying the Fatou lemma and the Krasnosel'skii fixed point theorem on cone,an existence theorem of positive solution is proved.The result does not require that the limit limu→+0 f(t,u)/u=+∞ almost uniformly holds on any closed interval .Therefore,a previous result is improved.