Experimental Study on Tensile Behavior of Cement Paste, Mortar and Concrete under High Strain Rates

Effects of the strain rate on cement paste, mortar and concrete were studied. A modified SHPB testing technique with fl attened Brazilian disc（FBD） specimen was developed to measure the dynamic tensile stress-strain curve of materials. A pulse-shaped split Hopkinson pressure bar（SHPB） was employed to determine the dynamic tensile mechanical responses and failure behavior of materials under valid dynamic testing conditions. Quasi-static experiments were conducted to study material strain rate sensitivity. Strain rate sensitivity of the materials was measured in terms of the stress-strain curve, elastic modulus, tensile strength and critical strain at peak stress. Empirical relations between dynamic increase factor（DIF） and the material properties were derived and presented.

Joint slip investigation based on finite element modelling verified by experimental results on wind turbine lattice towers

Slippage corresponds to the relative displacement of a bolted joint subjected to shear loads since the construction clearance between the bolt shank and the bolthole at assembly can cause joint slip. Deflections of towers with joint slippage effects is up to 1.9 times greater than the displacements obtained by linear analytical methods. In this study, 8 different types of joints are modelled and studied in the finite element program, and the results are verified by the experimental results which have been done in the laboratory. Moreover, several types of joints have been modelled and studied and load-deformation curves have also been presented. Finally, joint slip data for different types of angles, bolt diameter and bolt arrangements are generated. Thereupon, damping ratios （ζ） for different types of connections are reported. The study can be useful to help in designing of wind turbine towers with a higher level of accuracy and safety.

Simulation Study on Emergency Evacuation Behavior of College Students in Considering the Influence of Dormitory Interpersonal Relationship

As one of the most common social relationships among college students,the dormitory interpersonal relationship has important effects on students'psychology and behavior.For quantitative analysis of the dormitory interpersonal influence on college students'emergency evacuation behavior,an evacuation simulation experiment of college students carried out and coupling questionnaire survey,measurement and social force model of society to visualize the normal dormitory interpersonal relationship and emergency evacuation following relationship of college students,then simulation experiment is used to explore the impact of different types of dormitory relationship structure on emergency evacuation.The results show that dormitory interpersonal relationship is an important component of college students'interpersonal network and has an important impact on emergency evacuation behavior.The close and united dormitory relationship has a good promotion effect on the emergency evacuation efficiency.When the emergency occurs,the dormitory interpersonal relationship of college students will partly transform into the leader-following behavior relationship,and the evacuation efficiency will decrease.The influence of dormitory interpersonal relationship on evacuation behavior is related to gender and grade which is higher for female students than male students,and is higher for junior students than senior students.

Anti-fatigue activity of Brassica rapa L.extract and correlation among biochemical changes in forced swimming mice

Brassica rapa L.is an edible and medical plant in China used for treating various diseases,especially in the Tibet region.In this study,the chemical constituents of Brassica rapa L.extract(BE)was clarified by UHPLC-MS and anti-fatigue ability of BE was assessed through the behavior test and weight-loaded forced swimming test in mice.Then we determined several biochemical parameters related to fatigue to explore possible reasons.Results indicate that BE could significantly enhance exercise performance in mice,and there was a significant improvement in both grip-strength and the time on rota-rods.Meanwhile,BE showed significant anti-fatigue effects by decreasing the blood lactic acid(BLA),blood urea nitrogen(BUN),and creatine kinase(CK)levels and increasing the lactate dehydrogenase(LDH)and malondialdehyde(MDA)levels.Increases in superoxide dismutase(SOD)and glutathione peroxidase(GSH-Px)were observed and reactive oxygen species(ROS)levels was regulated.Liver and muscle glycogen levels and adenosine triphosphate(ATP)levels were also significantly increased.Pearson correlation analysis indicates that fatigue-related indexes including metabolites and energy-related indexes were significantly correlated with antioxidant levels.In conclusion,BE possesses remarkable anti-fatigue activity,thereby shows great potential for improving exercise performance and alleviating physical fatigue and can be considered as a functional food supplement for further development.