Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting...Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.展开更多
Introduction: Eating disorders are compulsive behaviours that can consume a person’s life to the point of becoming life threatening. Medical college can be a very stressful time and previous studies had found that st...Introduction: Eating disorders are compulsive behaviours that can consume a person’s life to the point of becoming life threatening. Medical college can be a very stressful time and previous studies had found that stress could be a main factor leading to higher risk of eating disorder. We aimed to determine the association between stress and eating disorders among undergraduate medical students. Methods: A cross-sectional study was conducted among 320 respondents comprises of Year 3, 4 and 5 medical students in private medical college in Malaysia, assessed using self-administered questionnaires which consist of social demographic data, EAT-26 and Cohen Perceived Stress Scale. The response rate of this study was 77.4%. Results: With regards to EAT-26, 11.0% of medical students were at risk of developing eating disorder and from this students who have obese BMI status (25%) had 3.9 times more likely to develop eating disorder (95% CI: 1.4 - 10.9). There was significant association between those with unsatisfactory social relationship with friends and peers (OR 2.5, 95% CI 1.0 - 5.9;p value 0.035) and risk of developing eating disorders (OR 3.9, 95% CI 1.4 - 10.9;p value 0.007). For Cohen Perceived Stress Scale (CPSS), 75.5% of the respondents were having high stress level. There was no significant association between stress and the risk of eating disorders with OR 1.0, 95% CI: 0.6 - 1.7;p value 0.887. Conclusion: Majority of medical undergraduates were under stressed and there was a risky trend toward eating disorders in medical. However, based on our results it did not portray any significant association between stress and risk of developing eating disorders. Nevertheless, it should not be completely neglected. It is important to increase the awareness of medical undergraduates regarding eating disorders and its complications.展开更多
The mechanical properties of rocks under cyclic and dynamic loading are important research topics for solving the structural stability of large engineering rocks. As underground mining in coal mines goes deeper, groun...The mechanical properties of rocks under cyclic and dynamic loading are important research topics for solving the structural stability of large engineering rocks. As underground mining in coal mines goes deeper, ground stresses are increasing and instability damage of coal rocks by shear loading is frequent. Therefore, in order to investigate the shear mechanical properties and section morphological characteristics of intact coal samples in the direct shear test, the RDS-200 rock direct shear instrument was used to carry out direct shear tests on intact coal samples under different normal stresses, and the shear section was scanned for three-dimensional morphology. The results show that: 1) from the strength characteristics, the peak shear strength of the coal samples increased linearly with increasing normal stress, and the residual shear strength increased logarithmically. 2) In terms of deformation characteristics, the peak shear displacement of the coal sample increases linearly with increasing normal stress, the pre-peak shear stiffness increases logarithmically, and the residual normal displacement decreases linearly. 3) From the morphological characteristics of the shear surface, with the increase of normal stress, the section transitions from high-order undulating to flattening type. The maximum height of the fracture surface profile and kurtosis coefficient of the shear section decreased linearly, and the profile area ratio and root mean square of slope decreased as a power function, i.e. the higher the normal stress, the smaller the undulation of the section, the sharpness of the roughness shape and the roughness coefficient JRC, and the flatter and smoother the section. The findings of this study can help to provide some reference for the evaluation of shear instability occurring in coal bodies under different normal stresses.展开更多
本文针对平面内弯矩作用下的T形圆管相贯节点焊缝处热点应力分布开展研究.利用径向拉伸法建立了T形圆管相贯节点的有限元网格模型,对热点应力分析结果的可靠性进行了网格密度分析和试验对比分析,提出了满足计算精度要求的基本密度网格....本文针对平面内弯矩作用下的T形圆管相贯节点焊缝处热点应力分布开展研究.利用径向拉伸法建立了T形圆管相贯节点的有限元网格模型,对热点应力分析结果的可靠性进行了网格密度分析和试验对比分析,提出了满足计算精度要求的基本密度网格.通过无量纲几何参数分析归纳了热点应力沿相贯线的环向分布规律及几何参数影响规律,发现了冠点波峰分裂现象及分裂过程中波峰曲线的三种变化形态,在此基础上提出了采用以π为周期的系数来修正冠点曲线形状的波形修正方法及分布曲线参数公式.与伦敦大学学院(University College London,UCL)两位学者的公式和试验数据进行对比分析,结果表明本文公式具有更简洁的表达形式和更高的精度.展开更多
文摘Differential equation of restrained torsion for rectangular-section box bar with honeycomb core was established and solved by using the method of undetermined function.Non-dimension normal stress, shear stress acting in the faceplate and shear stress acting in the honeycomb-core and warping displacement were deduced. Numerical analysis shows the normal stress attenuates quickly along x-axis. Normal stress acting on the cross section at a distance of 20 h from the fixed end is only one per cent of that acting on the fixed end.
文摘Introduction: Eating disorders are compulsive behaviours that can consume a person’s life to the point of becoming life threatening. Medical college can be a very stressful time and previous studies had found that stress could be a main factor leading to higher risk of eating disorder. We aimed to determine the association between stress and eating disorders among undergraduate medical students. Methods: A cross-sectional study was conducted among 320 respondents comprises of Year 3, 4 and 5 medical students in private medical college in Malaysia, assessed using self-administered questionnaires which consist of social demographic data, EAT-26 and Cohen Perceived Stress Scale. The response rate of this study was 77.4%. Results: With regards to EAT-26, 11.0% of medical students were at risk of developing eating disorder and from this students who have obese BMI status (25%) had 3.9 times more likely to develop eating disorder (95% CI: 1.4 - 10.9). There was significant association between those with unsatisfactory social relationship with friends and peers (OR 2.5, 95% CI 1.0 - 5.9;p value 0.035) and risk of developing eating disorders (OR 3.9, 95% CI 1.4 - 10.9;p value 0.007). For Cohen Perceived Stress Scale (CPSS), 75.5% of the respondents were having high stress level. There was no significant association between stress and the risk of eating disorders with OR 1.0, 95% CI: 0.6 - 1.7;p value 0.887. Conclusion: Majority of medical undergraduates were under stressed and there was a risky trend toward eating disorders in medical. However, based on our results it did not portray any significant association between stress and risk of developing eating disorders. Nevertheless, it should not be completely neglected. It is important to increase the awareness of medical undergraduates regarding eating disorders and its complications.
文摘The mechanical properties of rocks under cyclic and dynamic loading are important research topics for solving the structural stability of large engineering rocks. As underground mining in coal mines goes deeper, ground stresses are increasing and instability damage of coal rocks by shear loading is frequent. Therefore, in order to investigate the shear mechanical properties and section morphological characteristics of intact coal samples in the direct shear test, the RDS-200 rock direct shear instrument was used to carry out direct shear tests on intact coal samples under different normal stresses, and the shear section was scanned for three-dimensional morphology. The results show that: 1) from the strength characteristics, the peak shear strength of the coal samples increased linearly with increasing normal stress, and the residual shear strength increased logarithmically. 2) In terms of deformation characteristics, the peak shear displacement of the coal sample increases linearly with increasing normal stress, the pre-peak shear stiffness increases logarithmically, and the residual normal displacement decreases linearly. 3) From the morphological characteristics of the shear surface, with the increase of normal stress, the section transitions from high-order undulating to flattening type. The maximum height of the fracture surface profile and kurtosis coefficient of the shear section decreased linearly, and the profile area ratio and root mean square of slope decreased as a power function, i.e. the higher the normal stress, the smaller the undulation of the section, the sharpness of the roughness shape and the roughness coefficient JRC, and the flatter and smoother the section. The findings of this study can help to provide some reference for the evaluation of shear instability occurring in coal bodies under different normal stresses.
文摘本文针对平面内弯矩作用下的T形圆管相贯节点焊缝处热点应力分布开展研究.利用径向拉伸法建立了T形圆管相贯节点的有限元网格模型,对热点应力分析结果的可靠性进行了网格密度分析和试验对比分析,提出了满足计算精度要求的基本密度网格.通过无量纲几何参数分析归纳了热点应力沿相贯线的环向分布规律及几何参数影响规律,发现了冠点波峰分裂现象及分裂过程中波峰曲线的三种变化形态,在此基础上提出了采用以π为周期的系数来修正冠点曲线形状的波形修正方法及分布曲线参数公式.与伦敦大学学院(University College London,UCL)两位学者的公式和试验数据进行对比分析,结果表明本文公式具有更简洁的表达形式和更高的精度.
