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China possesses abundant pumice resources and thereby makes the utilization of pumice in the preparation of pumice aggregate concrete (PAC) a significant strategy for environmental protection and resource conservation. To obtain the effect of pumice pore structure variation on the compressive strength of PAC, PACs with strength classes LC20, LC30, and LC40 were prepared. Moreover, the pore structure of PAC was characterized using nuclear magnetic resonance to investigate the effect of pore structure variation on the compressive strength of PAC. Results showed that the higher the coarse aggregate content of PAC, the higher the percentage of large capillary and non-capillary pore sizes of PAC, corresponding to higher porosity and lower compressive strength. The hydration products in PAC continuously fill in the pore structure, the proportion of large capillary pores and non-capillary pore size gradually decreases, the proportion of small capillary pores and medium capillary pore size gradually increases, the pumice concrete matrix gradually becomes dense, and the compressive strength increases. The prediction model of the pore structure and compressive strength is established based on gray theory, and the relative error between predicted and tested values is not significant, which can effectively predict its compressive strength. It provides effective guidance for the engineering practical application of PAC.

In order to maximize the grid-connected power of high-power offshore wind turbines, a maximum power tracking strategy suitable for medium voltage six-phase permanent magnet synchronous generator (MVSPMSG) was proposed in the paper based on the use of MVSPMSG and distributed neutral point clamped converters to form a 10 MW wind power generation system. The optimal reference value of torque was given according to the speed feedback value, and the dual dq current control loop of the permanent magnet synchronous generator (PMSG) stator winding was designed through the feedforward decoupling method. The maximum power output control of the MVSPMSG was completed by the closed-loop combination of torque and double dq current loop. At the same time, a midpoint potential balance method with modulation coefficient and vector group selection coordinated adjustment was proposed to suppress the neutral point potential fluctuations on the DC side of the neutral point clamped converter. The method of adjusting the magnitude of modulation coefficient to suppress the fluctuation of the neutral point potential was first adopted. Meanwhile, the coordination vector group selection was applied to control the neutral point potential balance when the modulation factor exceeds the limit. Finally, a 10 MW permanent magnet wind power generation system model was established in MATLAB to verify the effectiveness of the control strategy proposed in the paper.

Abstract： Objective To explore the differences in the repair process of skin and skeletal muscle after contusion caused by blunt force attack with different heights. Methods Three degrees of contusion were performed on SD rats’ right hind limbs by a designed free-dropping device falling from 15, 30 and 50 cm heights, which as a main consideration factor for degree of injury. The repair process of skin and skeletal muscle at 6 h, 24 h, 3 d, 7 d and 13 d after contusion were observed using routine histological methods. Results Hematoma within skin and/or muscle was found in the rats’ hind limbs after contusion with three different heights. The repair processes were similar at 24 h after contusion. However, with the increase of height, the display degree was more obvious. At 3 d after contusion, the RBC of the hemorrhagic region would be decomposed and elapsed in 15 cm contusion group, but for 30 cm contusion group, it delayed to 7 d. At 13 d after contusion, the similar result was found in 15 cm and 30 cm contusion groups, in contrast, the 50 cm contusion group was still in the proliferative phase. Conclusion With the increase of height, the occurring rate of hematoma within skin and muscle at the same time increases, and the more serious histological appearance after contusion, including inflammation and proliferation, the longer healing process are observed. According to the results of present study and considering forensic application, the contusion model with 50 cm height （2.58 J/cm2） is recommended as the experimental animal model for the future study of wound age estimation on contusion.

Objective To analyse the characteristics of road traffic accident deaths in Haikou city, and to provide reference for the identification of causes of death and the preventive measures. Methods Totally 498 road traffic accident deaths accepted by the Traffic Police Branch of Haikou City Public Security Bureau in 2014—2016 were collected, and the related parameters such as sex, age, time of the accidents, travel mode of the victims, the types of vehicle and the cause of death were analysed. Results Most victims aged 21-40 years old with the sex ratio of 3:1, and the accidents mainly happened in March, April, May and October and peaked at 6：01-8：00 and 20：01-22：00 per day. Riding motorbike and electric bicycle, as travel modes, had the highest accident incidence （30.9%）. The vast majority of involved vehicles were motorbike and electric bicycle （57.4%）. The most common cause of death was craniocerebral injury, followed by chest and abdominal injury. Conclusion The autopsy of road traffic accident deaths plays an important role in identification of death manner and responsibility confirmation.