在（LL）-条件下研究二阶非自治Hamilton系统u（t）＋F（t，u（t））=0，a．e．t∈R，获得了周期解和次调和解的存在性和多重性结果．......

Experiments are performed in choked circular hot and cold nitrogen jets issuing from a 2.44 cm diameter sharp-edged orif......