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Porcine circovirus type 2 (PCV2) causes infectious diseases in pigs leading to considerable economic losses in the pig industry. To prevent and control PCV2 infections, is important to understand the prevalence and geographical distribution of the virus. We performed the first systematic review and meta-analysis to estimate the prevalence of PCV2 in China. From PubMed, ScienceDirect, Chinese Web of Knowledge, Wanfang, and VIP Chinese Journal, we extracted 53 studies published in China between 2015 and 2019. There were 29,051 samples, 14,230 of which were positive for PCV2. The pooled prevalence of PCV2 was 46.0%, with the highest in Northeastern China (58.1%). The highest prevalence was 86.3% in Xinjiang province. Nursery pigs had the highest prevalence of PCV2 (50.9%), and the serological test detected the highest number of cases (58.5%). PCV2 prevalence was 50.1% in intensive farms and 37.5% in extensive farms. Our findings showed that PCV2 is common throughout China. Effective control measures are necessary to reduce PCV2 infections.

In the applications for high resolution observation spacecrafts, control moment gyroscope (CMG) has to be mounted on the flexible vibration isolation device. As a matter of fact, the flexibility of the vibration isolation device makes a serious impact on the control performance of CMG gimbal servo system which is one of the most determinant performance indexes.In this paper, the structure and the dynamics of flexible mounting CMG are analyzed first. Secondly, the dynamic model of CMG gimbal servo system including new disturbances caused by flexible mounting is established. Then, the influences of flexible mounting on control performance of CMG gimbal servo system are demonstrated. Finally, a model based feedforward compensator and a notch filter are introduced to compensate the disturbance and the dynamics introduced by the flexible mounting. Simulation results show that the proposed controller attenuates the disturbance caused by flexible mounting effectively, and can achieve high precision control performances.

Comparing with the indirect drive gimbal servo system of single gimbal control moment gyroscope (SGCMG), direct drive gimbal servo system based on permanent magnet synchronous motor (PMSM) can achieve higher precision and faster response. However, the difficulty of PMSM controller design increases, because PMSM has to endure larger multi-source and multi-band disturbances due to the lack of a decelerator. In this paper, PMSM direct drive system is described, importantly, based on SVPWM control strategy, a novel composite control strategy is proposed: an adaptive nonsingular terminal sliding mode controller (ANTSMC) with a disturbance sliding mode observer (SMO) is designed to achieve high precision speed closed-loop control and compensate uncertain large low frequency disturbances; a repetitive controller (RC) is designed to compensate high frequency disturbances. Simulation results show that the proposed controller has strong robustness and disturbance tolerance, and can achieve high precision and fast response control performances.