The study of impacts of down-up hill road segment on the density threshold of traffic shock formation in ring road vehicular flow is helpful to the deep understanding of sags’bottleneck effect.Sags are freeway segmen...The study of impacts of down-up hill road segment on the density threshold of traffic shock formation in ring road vehicular flow is helpful to the deep understanding of sags’bottleneck effect.Sags are freeway segments along which the gradient increases gradually in the traffic direction.The main aim of this paper is to seek the density threshold of shock formation of vehicular flow in ring road with down-up hill segment,because down-up hill roadway segment is a source to cause capacity reduction that is an attractive topic in vehicular traffic science.To seek the density threshold numerically,a viscoelastic continuum model[1]is extended and used.To solve the model equations,a fifth-order weighted essentially non-oscillatory scheme for spatial discretization,and a 3rd order Runge-Kutta scheme for time partial derivative term are used.Validation by existing observation data and the Navier-Stokes like model[2]extended as EZM is done before conducting extensive numerical simulations.For ring road vehicular flow with three separated down-up hill segments,it is found that the density threshold of shock formation decreases monotonically with the relative difference of free flow speed,this variation can be simply fitted by a third order polynomial.展开更多
目的 探讨经颅直流电刺激(transcranial direct current stimulation,tDCS)结合抗阻训练对大学生完成引体向上成绩的影响作用,并从神经肌肉活动控制角度探讨训练干预产生作用的潜在机制。方法 25名男性大学生志愿者随机分为tDCS结合抗...目的 探讨经颅直流电刺激(transcranial direct current stimulation,tDCS)结合抗阻训练对大学生完成引体向上成绩的影响作用,并从神经肌肉活动控制角度探讨训练干预产生作用的潜在机制。方法 25名男性大学生志愿者随机分为tDCS结合抗阻训练组(试验组)和单纯抗阻训练组(对照组),12名对照组受试者接受持续8周、每周3次、每次4组、每组12次动作重复的高位下拉力量训练干预,13名试验组受试者在对照组所采用的训练基础上,在每次训练前进行20 min的tDCS干预。在训练干预前后分别对受试者进行高位下拉静态自主最大收缩力(maximal voluntary contraction,MVC)、80%一次最大重复(one repetition maximum,1RM)负荷高位下拉最大重复次数和常规引体向上动作测试。在引体向上动作测试过程中记录上肢主要用力肌肉的表面肌电信号。结果 训练干预后,试验组和对照组引体向上完成次数分别提高了1.74倍和1.42倍,两组受试者MVC和80%1RM负荷高位下拉最大重复次数也都显著提升,但两组受试者上述指标差异皆无统计学意义。训练后两组受试者主动肌肱桡肌、三角肌后束、胸大肌的激活水平皆显著下降。此外,试验组受试者在训练后拮抗肌肱三头肌的共激活水平由0.50±0.22显著下降到0.37±0.09,而对照组在干预前后无显著变化。结论 持续8周的tDCS结合抗阻训练和单纯抗阻训练显著提升大学生引体向上成绩,可能与两种训练皆可以显著提升主动的肌肉收缩能力有关。tDCS结合抗阻训练可以更有效地降低引体向上动作过程中肱三头肌的共激活水平,提高肘关节肌肉的收缩效率。展开更多
基金supported by National Natural Science Foundation of China(NSFC No.11972341)fundamental research project of Lomonosov Moscow State University’s Mathematical models for multi-phase media and wave processes in natural,technical and social systems.
文摘The study of impacts of down-up hill road segment on the density threshold of traffic shock formation in ring road vehicular flow is helpful to the deep understanding of sags’bottleneck effect.Sags are freeway segments along which the gradient increases gradually in the traffic direction.The main aim of this paper is to seek the density threshold of shock formation of vehicular flow in ring road with down-up hill segment,because down-up hill roadway segment is a source to cause capacity reduction that is an attractive topic in vehicular traffic science.To seek the density threshold numerically,a viscoelastic continuum model[1]is extended and used.To solve the model equations,a fifth-order weighted essentially non-oscillatory scheme for spatial discretization,and a 3rd order Runge-Kutta scheme for time partial derivative term are used.Validation by existing observation data and the Navier-Stokes like model[2]extended as EZM is done before conducting extensive numerical simulations.For ring road vehicular flow with three separated down-up hill segments,it is found that the density threshold of shock formation decreases monotonically with the relative difference of free flow speed,this variation can be simply fitted by a third order polynomial.
