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In order to clarify the nutrients and stoichiometric changes of soil aggregates in different forest types, reveal the soil nutrient retention and limitation characteristics of coal mining subsidence land, and then screen out the best reclaimed-forest types. In this study, three types of reclaimed forests, namely Amygdalus sylvestris, Prunus sylvestris, and Xanthomonas serrata, were set up on the Shenfu-Dongsheng mining area in the coal mining subsidence area. At the same time, the nearby unsettled and unplanted abandoned farmland was used as a control, based on the dry sieve method to explore the soil mechanical stability aggregate composition, soil SOC (organic carbon), TN (total nitrogen), TP (total phosphorus) content and its stoichiometric characteristics in response to long-term vegetation reclamation in 0-40 cm soil law. The results showed that the content of soil micro-aggregates of different reclaimed-forest types decreased while the content of large aggregates increased, and the total amount of large aggregates >0.25 mm in each forest type exceeded 70%. The content of SOC, TN and TP in soils of different forest types 0.25 mm large aggregates to soil SOC, TN and TP were 72%-83%,66%-74%, 65%-82% respectively. The C/N, C/P and N/P of soil aggregates of different forest types were all lower than the average of national and global. Soil TN was positively correlated with SOC and TP, and negatively correlated with C/N (P

In order to simplify the structure of the ocean drilling heave compensation system and reduce the energy consumption of active drawworks heave compensation system, a new type of semi-active drawworks heave compensation system was designed through structure design, system modeling and internal model PID robust displacement controller design. Then the feasibility of the system was verified by non-linear time domain simulation and experimental study. The structure design realizes decoupling control of heave compensation and automatic bit feed, reduces energy consumption of the system. The system is simplified to build simulation model by lumped mass method and energy conservation principle. The double control scheme of hook displacement closed loop in the outer loop and motor speed closed loop in the inner loop is put forward, the internal model PID robust displacement controller of outer loop is designed. The steady-state deviation of internal model control is zero when the model is matching or mismatching. The dynamic performance and resisting disturbance capacity of the internal model control is better when the filter time constant is smaller. The compensation rate is above 90% by simulation and experimental research results, the compensation effect is good and the system is feasible. Key words: drilling platform, drawworks, heave compensation, semi-active, system design