Diurnal freeze/thaw cycles of the ground surface on the Tibetan Plateau

The exchange of energy and water between the lithosphere and atmosphere mainly takes place at the ground surface. Therefore, freeze/thaw condition at the ground surface is an important factor in ex- amining the interactions between the land surface and atmosphere. Based on the observation data obtained by CEOP/CAMP-Tibet, the diurnal freeze/thaw cycles of the ground surface near Naqu, central Tibetan Plateau was preliminarily analyzed. The results show that the surface layer was completely frozen for approximately one month. However, the time that the ground surface experienced diurnal freeze/thaw cycles was about 6 months. The high frequency of freeze/thaw cycles at the ground surface significantly influences water and energy exchanges between ground and atmosphere over half a year. The interaction processes between the ground and atmosphere under different soil conditions (such as complete thaw, complete freeze and diurnal freeze/thaw cycles) are issues worthy of further examina- tion.     

车辆起-停巡航控制系统的加速度跟踪控制

针对低速行驶工况下的车辆StopandGo(起停)巡航控制系统,在研究其加速度动态响应非线性特性的基础上,设计了一种基于滑模变结构控制(SMC)的模型匹配控制器,该控制器综合了SMC的鲁棒性及模型匹配控制(MMC)快速响应的优点。通过仿真计算,结果表明该控制器不但能有效提高车辆在低速工况下加速度的快速跟踪性,而且还改善了系统对外界干扰的鲁棒性能。