Basal difficulty on the optimize question of reliability is that when the system optimize the parameter, variable, must evaluate and must calculate the reliability once more.
可靠性优化问题的基本难点在于系统每优化一次，参数、变量就要重新赋值，就要重新计算系统可靠度。
2
Carrieing on the science effective forecast to the reservoir parameter, thus instruction exploration development, always is the petroleum geology hot spot and the difficulty.
对储层参数进行科学有效的预测，从而指导勘探开发，一直是石油地质学的热点和难点。
3
The current velocity is an important parameter of debris flow, and it is more difficulty to be measured and calculated.