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Numerical Study on Stress Intensity Factors for Stud Connectors of Steel–Concrete Connection
Da Wang,Benkun Tan,Lei Wang,Fanghuai Chen,Shengtao Xiang 한국강구조학회 2021 International Journal of Steel Structures Vol.21 No.5
The fatigue fracture of the stud connector is the main failure mode of the steel–concrete composite structure. Fatigue assessment of cracked stud connectors with weld details is conducted in this study by using the linear elastic fracture mechanics approach. The mixed-mode stress intensity factor is calculated by the M -integral method, and the relative crack position h c is considered. First, a 3D fi nite element model of the push-out test with stud welding details is proposed in this study, and the load–slip curve and stress distribution of the stud connector were analyzed. Then, the mixed-mode stress intensity factor was calculated by defi ning the sub-model with cracks, and the infl uence coeffi cient of the mixed-mode stress intensity factor was investigated. The important infl uencing parameters, which include the crack aspect ratio, relative crack height, stud diameter, and stud height, are combined for calculation. The mixed-mode stress intensity factor of the stud is dominated by mode I (open). The infl uence of the stud height is not observed. However, the stress intensity factor of the crack tip gradually increases with the stud diameter. The study also found the infl uence of the crack shape under various conditions. The results of this study can be used by researchers to evaluate the fatigue fracture conditions of stud connectors.
Blood amino acids profile responding to heat stress in dairy cows
Jiang Guo,Shengtao Gao,Suyu Quan,Yangdong Zhang,Dengpan Bu,Jiaqi Wang 아세아·태평양축산학회 2018 Animal Bioscience Vol.31 No.1
Objective: The objective of this experiment was to investigate the effects of heat stress on milk protein and blood amino acid profile in dairy cows. Methods: Twelve dairy cows with the similar parity, days in milk and milk yield were randomly divided into two groups with six cows raised in summer and others in autumn, respectively. Constant managerial conditions and diets were maintained during the experiment. Measurements and samples for heat stress and no heat stress were obtained according to the physical alterations of the temperature-humidity index. Results: Results showed that heat stress significantly reduced the milk protein content (p<0.05). Heat stress tended to decrease milk yield (p = 0.09). Furthermore, heat stress decreased dry matter intake, the concentration of blood glucose and insulin, and glutathione peroxidase activity, while increased levels of non-esterified fatty acid and malondialdehyde (p<0.05). Additionally, the concentrations of blood Thr involved in immune response were increased under heat stress (p<0.05). The concentration of blood Ala, Glu, Asp, and Gly, associated with gluconeogenesis, were also increased under heat stress (p<0.05). However, the concentration of blood Lys that promotes milk protein synthesis was decreased under heat stress (p<0.05). Conclusion: In conclusion, this study revealed that more amino acids were required for maintenance but not for milk protein synthesis under heat stress, and the decreased availability of amino acids for milk protein synthesis may be attributed to competition of immune response and gluconeogenesis.
Lei Bin,Su Jianjiao,Wang Shengtao 아시아건강운동학회 2020 Journal of Asian Society for Health & Exercise Vol.2 No.2
Objective: To observe the rehabilitation effects of prescription and precise exercises of Health Qigong Dawu on common chronic diseases in the middle-aged and elderly people. Method: Test the complete exercise of Health Qigong Dawu and the exercise time, frequency and intensity of each style; 106 people were randomly divided into groups, 56 people in the experimental group and 50 people in the control group. At the same time, basic TCM syndromes for sub-healthy people Epidemiological investigation of the phenotype, grasp the basic situation of common chronic diseases, with cervical spondylosis, lumbar muscle strain, insomnia, constipation, and gastritis as the main observation contents; according to the chronic disease status of the experimental group, 6 exercise prescriptions were formulated, On the basis of exercises, precise exercises were carried out; the control group only exercised the whole set of exercises, conducted 6 months of experimental observation and statistical analysis. Results: There was no significant difference in the three indicators of age, height, and weight between the two groups. Through the test, 4 obvious peaks occurred within 14 minutes and 20 seconds, and the heart rate trend gradually changed from low to high. The lowest heart rate was 75 beats per minute, the highest heart rate was 106 beats per minute, and the average heart rate was 100 beats per minute. The energy consumption is 63 calories, which meets the requirements of aerobic exercise and fitness. It embodies the characteristics of Health Qigong Dancing with dance, opening and closing, stretching and stretching, internal organs and joints. Combined with the common chronic diseases of the subjects, the effect was observed for 6 months. The improvement rate of the experimental group was 67.20% for cervical spondylosis, 73.30% for lumbar muscle strain, 68.53% for insomnia, 57.50% for constipation, and 56.35% for gastritis; The improvement rate was 52.20% for cervical spondylosis, 55. 0% for lumbar muscle strain, 52.20% for insomnia, 46.20% for constipation, and 45. 20% for gastritis. Conclusion: The heart rate fluctuations of Health Qigong Dawu exercises are all within the range of aerobic exercise, which is in line with the physiological laws of fitness for middle-aged and elderly people. The test results show that the action structure, exercise intensity and exercise time of Health Qigong Dawu Gong, Exercise frequency is reasonable; formulating exercise prescriptions for middle-aged and elderly people is reasonable and effective; it has significant fitness effects on common chronic diseases such as cervical spondylosis, lumbar muscle strain, insomnia, constipation, and gastritis. The experimental group is better than the control group, with significant differences.