Initial conditions of impact dynamics

The effects of the initial conditions of impact dynamics equations are investigated numerically and experimentally. The inadequacies of previous studies on initial conditions are pointed out. Then a coefficient of velocity jump at the moment of impact is introduced, and the experiments for the mental rods are implemented to validate the appending constraints modeling methods for impact process. The comparisons between the experimental and simulated results at different coefficients are used to study the effects of the velocity jump conditions to the numerical simulation. The results indicate that the physical velocity response of bodies during impact is smooth; the different values of velocity jump only have small effects on numerical oscillation of velocity response, and they have no effects on the time history of impact force.     

Fe{O(CH_2CO_2)_2}(H_2O)_2(NO_3)电子结构和磁性的第一性原理研究

采用第一性原理计算研究了Fe{O(CH2CO2)2}(H2O)2(NO3)晶体的电子结构及磁性。该计算采用密度泛函理论(DFT)结合投影缀加波(PAW)方法。计算结果表明,化合物Fe{O(CH2CO2)2}(H2O)2(NO3)具有反铁磁基态,这种反铁磁相互作用来自于最近邻的铁离子;每个分子的自旋磁矩是4.99μB,这和实验结果也是相吻合的。     

Effects of erigeron breviscapus （Vant.） Hand-Mazz pretreatment on pathology and oxyradical level following spinal cord ischemia-reperfusion injury in rabbits

Objective To investigate the effects of erigeron breviscapus (Vant.) Hand-Mazz (erigeron breviscapus) pretreatment on pathology and oxyradical level in the spinal cord after ischemia-reperfusion (I/R) injury in rabbits. Methods A total of 40 New Zealand white rabbits were randomly divided into three groups: sham-operation group with 10 rabbits treated with only abdominal aorta exposure without occlusion, control group with 15 rabbits that underwent ischemia for 50 minutes and treated with matched saline, and experimental group with 15 rabbits that underwent ischemia for 50 minutes and treated with erigeron breviscapus (9mg/kg) injection before ischemia. Malondialdehyde (MDA) level and superoxide dismutase (SOD) activity in the spinal cord were examined at 6 and 24 hours after I/R, respectively. The morphological changes and the number of the spinal cord anterior horn motor neurons were observed and counted under the light microscope and electron microscope, respectively. Results The level of MDA was markedly decreased and SOD activity was increased in the experimental group compared with those in the control group (P<0.01). Compared with that in the control group, the number of motor neurons in the experimental group significantly increased at 24h after I/R (P<0.01) and the morphous of the motor neurons improved. Conclusion Erigeron breviscapus can reduce oxyradical production and the apoptosis of nerve cells, and protect nerve tissue structure and function after spinal cord I/R.     

ISAC防治半刚性基层反射裂缝的力学分析及试验

通过力学分析与室内试验研究了各种夹层用于半刚性基层反射裂缝的防裂情况,结果表明ISAC复合夹层有着较好的防裂效果。采取复合夹层下面的基层埋设位移计和测缝计,上面的沥青混合料面层埋设应变计的方法对试验路段复合夹层的防裂情况进行了测试。振弦式测缝计的试验测定结果的线性关系稳定.能较好地反映路面基层预切缝在温度变化情况下的实际缝隙变化规律。铺设聚酯玻纤布ISAC复合夹层的预切缝2和采用玻纤格栅作为上层应变吸收层的预切缝4的测试结果表明,两者具有基本一致的缝隙张开量变化规律。两者都有着较好的抗裂效果。在较高温度下。采用玻纤格栅ISAC复合夹层的防裂效果优于聚酯玻纤布ISAC复合夹层。但低温情况下的防裂效果还有待于后续的测试。     

侧碰试验中车门运动与假人伤害响应的相关性

根据侧碰撞试验中车门的运动特点,将车门运动的速度曲线简化为双速度平台曲线,使得车门运动对乘员伤害的影响可用接触时间、过渡段斜率及第2速度平台3个特征参数的变化完整地描述.利用MADYMO仿真软件建立了侧碰撞台车模型,研究了3个特征参数与侧碰撞假人伤害值响应的相关性.     

汽车滑行阻力系数的测定方法研究

根据软件 matlab 的符号微分方程解法求出汽车滑行运动方程,将一定范围内的由滚动阻力系数和风阻系数计算出的滑行曲线和采样滑行曲线进行比较,找出了最能拟合采样滑行曲线的参数,该方法不需给定阻力系数的初始值就能找到各阻力系数的大小,阻力系数的精度由步长确定.通过计算实例表明,根据阻力系数计算的滑行数据与采样数据曲线重合,验证了拟合结果的正确性.     

有利于行人头部保护的碰撞波形研究

对行人头部碰撞波形进行了合理简化,研究了3种典型简化波形对行人头部碰撞所需吸能空间的影响,推导出了满足头部伤害指标HIC=1000且所需吸能空间最小的最优简化波形,提出了有利于行人头部保护的碰撞波形改进措施.建立了某车型行人头部碰撞有限元模型并进行了试验验证,结果表明,所提改进措施可以有效地提高行人头部保护性能.     

YC6A220C柴油机排气余热裂解甲醇助燃的试验研究

在不改变YC6A220C柴油机结构和参数的基础上,从排气管道引出高温尾气裂解甲醇气进入柴油机进气管进行混合燃烧,研究了共轨燃烧甲醇裂解气时YC6A220C柴油机的燃烧排放特性.结果表明,与原机相比,燃用预混裂解气的发动机动力性基本无变化,经济性有所提高,在掺烧比为1.5%～6%时,各种负荷下节油可达4%～8%;在高负荷时,NOx排放可降低32.4%,碳烟排放可降低41.6%,HC排放也有明显降低.     

城市平面交叉口可靠性分析

随着城市道路网络可靠性研究的深入,交叉口已不能再作为完全可靠的道路单元,交叉口可靠性问题开始凸显。在对交叉口具体分析的基础上,充分考虑交叉口的容量限制,提出了容量限制下运行时间可靠度（TCR）,并对TCR模型的优点进行了分析,给出了可接受水平值的确定方法。运用概率论基础知识,对道路网络最基本单元交叉口进行了TCR分析,给出了交叉口TCR的具体求解过程。     

我国汽车逆向再制造物流发展浅析

汽车再制造工程的每一个环节都体现了逆向物流网络的特点,也体现了汽车逆向物流是一个复杂的系统工程,不同于一般的正向物流,也不同于传统废旧回收物流。要发展我国的汽车再制造工程,就必须将逆向物流工程和再制造工程有机地结合,将汽车逆向物流作为一个系统工程进行深入的研究。文中介绍了汽车再制造和逆向物流的概念及特点,分析了我国汽车逆向物流发展的现状和存在的问题,并给出了解决问题的建设性建议。