一、问题的提出弯脖,又称“歪脖”、“拐脖”或“直拐脖”等,在工农业生产及人民生活中有着广泛的应用,比如:在我国长江以北的广大地区,人们的生活、冬季取暖烧煤炉等所安装的烟囱无一不见弯脖的身影,见图1(d). First, the issue of bending neck, also known as “neck neck”, “turning neck” or “straight neck ”, has a wide range of applications in industrial and agricultural production and people’s lives, such as: in our country In the vast area north of the Yangtze River, the chimneys installed in people’s lives and winter coal-fired furnaces are all seen in the neck, as shown in Figure 1(d).