不可预知的

The inventory cost is a primary component of the supply chain cost, and the method for multi-echelon inventory optimization and control must be adopted for the sake of the entire supply chain optimization and control, t present, papers on multi-echelon inventory systems have solved some problems, but they still have limitations. Firstly, they assumed that leadtime are constants. In practice, as the unknowable incidents exist in production, transportation and distribution processes, leadtime usually are uncertain. Secondly, there exist the hypotheses of totally back orders or completely lost sales under the condition of stockout in most literatures. Thirdly, the existing two-echelon inventory approximate model optimum always fixes one variable in the inventory strategy, and then seeks the optimal in the remained parameters, which makes the result can not be the best outcome.

目前有关两级库存优化控制的研究文献大多是假设提前期为常数的基础上建立模型，然而现实中由于供应链上各节点的库存不确定性以及运输、生产、交货等环节的不可预知性，使得提前期在多数情况下是不确定的；而且大部分文献都是假设缺货情况下要么完全延迟交货，要么完全损失销售，很少有考虑部分损失销售情况下库存优化控制的；另外，现有的两级库存近似模型的优化大都是固定一个库存策略中的变量，对余下变量寻优，其优化结果不可能是最优结果。

The concept of equivalent rotationally rigidity is offered and the formula of rotationally rigidity is obtained.

主要做了如下几个方面的工作：对伸臂位于顶部的单层框架—筒体模型进行分析，提出了等效转动约束的概念和转动约束刚度的表达式。

Male cats normally do not need aftercare with the exception of the night after the anesthetic.

男猫通常不需要善后除了晚上的麻醉。