Using the linear programming method, they have set up a mathematic optimization model for adjusting age-grade of timber forest in Hushan Forestry Farm of Suichang, Zhejiang.
用线性规划的方法建立遂昌湖山林场用材林龄级调整最优化数学模型。
2
3rd grade (age 8).
三年级(8岁)。
3
Starting formal schooling too early — being in first grade before age 6 — is a risk factor for earlier mortality.