定义屏蔽体的最大层数、每层的厚度范围、可供选择的材料类型，在优化变量的定义域内初始随机生成屏蔽体的层数、各层的厚度和材料等参数，根据参数生成中子学物理模型

Define the maximum number of layers of the shielding body, the thickness range of each layer, and the types of materials available for selection. Within the definition domain of optimization variables, initially randomly generate parameters such as the number of layers of the shielding body, the thickness of each layer, and the material. Based on these parameters, generate a neutron physics model