集料剪切性能的数值模拟分析

使用微观结构的离散单元模型对集料直剪试验进行数值模拟,以预测集料颗粒的抗剪强度和影响因素．模型用法向和切向刚度等来描述颗粒及接触的本构关系,可通过各参数的调整进行颗粒抗剪强度分析．计算结果表明,微观力学方法评价集料的抗剪强度有较大的分析潜力．     

The impact of ride-hailing on vehicle miles traveled

Transportation - Ride-haling such as Uber and Lyft are changing the ways people travel. Despite widespread claims that these services help reduce driving, there is little research on this topic....     

Do frequent satisfying trips by public transport impact its intended use in later life?

Transportation - Previous studies have indicated that factors such as the built environment, attitudes and past behaviour can influence travel behaviour. However, the possible effect of travel...     

Deformation and Stress of Old Cement Concrete Pavement under Stamping Load

为准确分析冲压荷载作用下旧水泥混凝土路面的变形和应力分布状况,通过建立合适的有限元模型来对其分析计算,并以第一强度理论来判断旧路面板的破裂情况,总结了路面板在冲击压实情况下的破坏机理.通过该模型得出旧水泥路面板竖直方向和水平方向的变形和受力特点,即:路面板在冲压荷载作用下发生纵、横双向弯曲变形,并以全断面的纵向弯曲变形为主,最大变形值位于路面板的两冲压轮之间的位置,路面板断面上竖向各点的沉降变形有微小变化,变形性态说明路面板将以弯曲形式发生破坏;路面板在轮压荷载作用下,上面层受压应力,下面层受拉应力,拉压应力的分界点在路面板中心偏下的位置,上面层绝大部分区域3个方向均处于受压状态,纵向压应力几乎为横向压应力的2倍.     

鼓式制动器结构模态分析

采用试验模态分析和有限元计算模态分析相结合的方法，对鼓式制动器进行模态参数识别，以有限元计算模态分析为主，通过试验模态分析对有限元计算结果进行检验，这种方法是工程上比较实用和行之有效的模态分析方法，针对鼓式制动器各子系统建立了有限元模型，采用动画显示来观察各阶段态的振型，很好地解决了有限元的后处理问题。     

Preview-Based Control of Suspension Systems for Commercial Vehicles

An active suspension with preview is developed for the rear axle of a commercial vehicle. The obtained improvements are promising and justify further investigation of the more feasible semi-active suspensions with preview. The inherent non-linearity of semi-active suspensions with switching shock absorbers and the need for controllers that can handle a broad class of control objectives has led to the development of several numerical control methods for both multi-level and continuously variable shock absorbers. The most promising control method and shock absorber type are selected and mounted in a test vehicle. Some first experimental results are discussed.     

丙型肝炎病毒非结构蛋白3全长基因的克隆和表达

目的克隆和表达丙型肝炎病毒(HCV)非结构基因NS3,为进一步研究其基因功能奠定基础。方法设计特异性引物,以HCV全长cDNA质粒为模板进行PCR扩增,获得全长NS3基因。将其插入克隆载体pMD18-Tvector中,经酶切、PCR及测序鉴定后,与表达载体pET32a重组,后转入BL21菌株并诱导表达。采用SDS-PAGE电泳及Western-blot检测NS3基因的蛋白表达水平。结果含有NS3的重组体构建成功并在大肠杆菌中表达。结论运用原核细胞基因工程技术成功构建和表达了HCV非结构基因NS3蛋白,为尽一步研究HCVNS3基因功能奠定了基础。     

THE CHANGES OF BONE VOLUME AND TURNOVER IN POSTMENOPAUSAL WOMEN WITH OSTEOPOROSIS：A REPORT OF 293 BONE BIOPSIES

ＴＨＥＣＨＡＮＧＥＳＯＦＢＯＮＥＶＯＬＵＭＥＡＮＤＴＵＲＮＯＶＥＲＩＮＰＯＳＴＭＥＮＯＰＡＵＳＡＬＷＯＭＥＮＷＩＴＨＯＳＴＥＯＰＯＲＯＳＩＳ：ＡＲＥＰＯＲＴＯＦ２９３ＢＯＮＥＢＩＯＰＳＩＥＳＺｈｕＪｉａｎｍｉｎ；ＷｉｌｌｉａｍＥ．Ｈｕｆｆｅｒ，Ｐａｔ...     

REGULATED PHOSPHORYLATION OF THE GATA－2 DNA BINDINGPROTEIN IN ENDOTHELIAL CELLS

ＲＥＧＵＬＡＴＥＤＰＨＯＳＰＨＯＲＹＬＡＴＩＯＮＯＦＴＨＥＧＡＴＡ－２ＤＮＡＢＩＮＤＩＮＧＰＲＯＴＥＩＮＩＮＥＮＤＯＴＨＥＬＩＡＬＣＥＬＬＳＢｕＸｉｎＥ．Ｅ．Ｑｕｅｒｔｅｒｍｏｕｓ，Ｔ．Ｑｕｅｒｔｅｒｍｏｕｓ（ＤｅｐａｒｔｍｅｎｔｏｆＭｅｄｉｃｉｎｅ...     

The effect of precession-induced changes in the Mediterranean freshwater budget on circulation at shallow and intermediate depth

The Neogene marine sedimentary record of the Mediterranean basin is characterised by the regular occurrence of organic-rich layers or sapropels. These sapropels are known to correlate with the precession cycle: their deposition coincides with precession minima. This correlation is thought to be caused to a large extent by a precession-induced increase in the amount of freshwater reaching the Mediterranean Sea. In the literature, various sources of this extra freshwater have been identified and different mechanisms as to how this freshwater flux leads to sapropels have been proposed. In this study we investigate the effects of precession-induced changes in the freshwater budget using a regional ocean general circulation model of the Mediterranean Sea. Emphasis is on the effects at the surface and at intermediate depth. The forcing of the ocean model is adjusted to precession minimum conditions on a parameter by parameter basis. Novel to our approach is that the value of the required adjustments is taken from a global coupled climate model with which experiments have been performed for the present day (close to precession maximum) and precession minimum. With the ocean model we focus on the extent to which extra runoff from either south (specifically: the river Nile) or north and changes in net precipitation over the sea itself lead to a more stable stratification; this we judge by the associated reduction of the sea surface salinity and mixed layer depth in the regions of intermediate and deep water formation. Our main finding is that the effects of (1) increased discharge of the rivers coming from the north, and (2) the increase in net precipitation over the sea itself, are of equal or greater importance than that of increase in Nile discharge.