| 1 | Osteoporosis affects both post-yield microdamage accumulation and plasticity degradation in vertebra of ovariectomized rats显示文摘Estrogen withdrawal in postmenopausal women increases bone loss and bone fragility in the vertebra. Bone loss with osteoporosis not only reduces bone mineral density(BMD), but actually alters bone quality, which can be comprehensively represented by bone post-yield behaviors. This study aimed to provide some information as to how osteoporosis induced by estrogen depletion could influence the evolution of post-yield microdamage accumulation and plastic deformation in vertebral bodies. This study also tried to reveal the part of the mechanisms of how estrogen deficiency-induced osteoporosis would increase the bone fracture risk. A rat bilateral ovariectomy(OVX)model was used to induce osteoporosis. Progressive cyclic compression loading was developed for vertebra testing to elucidate the post-yield behaviors. BMD, bone volume fraction, stiffness degradation, and plastic deformation evolution were compared among rats raised for 5 weeks(ovx5w and sham5 w groups) and 35 weeks(ovx35w and sham35 w groups) after sham surgery and OVX. The results showedthat a higher bone loss in vertebral bodies corresponded to lower stiffness and higher plastic deformation. Thus, osteoporosis could increase the vertebral fracture risk probably through microdamage accumulation and plastic deforming degradation. | Siwei Li Guodong Niu Neil X. Dong Xiaodu Wang Zhongjun Liu Chunli Song Huijie Leng | 2017 | Acta Mechanica Sinica2017，33，2： | 3 |
| 2 | GE公司Tier3机车柴油机的设计与开发显示文摘为了应对美国环保局(EPA)1998年发布的机车排放标准(2000年生效),GE公司开始着手GEVO发动机的开发。开发这种新的发动机平台是为了满足美国环保局和其他立法机构未来的排放法规要求,以及满足客户所需要的高可靠性、低运行成本的要求。创新系列机车自2005年开始投放市场以来,已有超过2000台Tier2达标机车交货,已经证明,该机车采用的GEVO发动机是非常可靠、高效的。为满足Tier2排放标准要求而设计的GEVO发动机是非常成功的,最近,为满足美国EPA Tier3机车排放标准要求,对其又进行了修改。通过改进喷油方法、减少机油消耗和改进进气系统,发动机PM(颗粒物)排放量减少了50%;同时,NOx的排放量保持不变,而且也没有对燃油经济性构成损害。PM减排目标是通过机油消耗的减少和喷油控制方法的改进而达到的。机油消耗量的减少是通过采用一套更得力的活塞环组和缸套表面的优化而实现的。为了判定各种动力组件结构设计特点带来的影响并选择最终的动力组结构,采用了一套瞬时的机油消耗测量系统。该系统使我们对不同运行条件下(即低负荷工况、过渡工况和高负荷工况)的机油迁移机理有了深刻的理解。通过采用新的高压共轨燃油喷射系统,可以更灵活地调节燃油的喷射和控制喷射压力,从而进一步降低了颗粒物排放量。燃油消耗率的损失是通过提高增压器效率和采用提前关闭进气门以及优化喷油方法来弥补的。最终的结构经过了大量的试验台试验和现场耐久性试验的验证。本文将对GE公司下一代机车柴油机的发展过程和设计特点加以介绍。 | Neil X. Blythe W. Doug Glenn 李臣 | 2011 | 国外内燃机车2011，，5： | 2 |
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