黄土沟谷地区格构式高墩偏位及受力性能分析

黄土沟谷地区格构式高墩在施工以及使用过程中,由于受到不同因素的影响,其墩身可能会产生一定的偏位。为研究其偏位对墩身受力以及损伤性能的影响,本文以河沟大桥4#高墩为研究对象,利用有限元软件Midas Civil和ABAQUS研究分析了高墩在最不利荷载状态下墩顶的最大偏位值以及偏位后的墩身的受力性能和损伤性能。研究结果表明：最不利荷载作用下墩顶最大偏位为35 cm;当墩顶偏位最大时,墩顶水平推力小于混凝土破坏时的水平推力临界值,此时,墩身受压侧混凝土压应力之比与墩体受拉侧钢筋拉应力之比均小于规范允许上限值,墩身混凝土未发生完全破坏;在墩顶最大偏位位移下,墩身受拉损伤因子相比墩身受压损伤因子较大,墩身受拉损伤比较严重。可见黄土沟谷地区格构式高墩施工应控制墩顶偏位,降低对墩体承载力的消弱。     

力在物理学中的含义和地位的演变

物理学中的一系列基本概念,如时间、空间、力、质量、能量等,它们在物理学的各分支学科中的含义和地位并不是完全相同的,甚至也有完全不同的情况．近现代物理学发展历史表明物理学名词概念的含义总是随着物理学的发展而深化．物理学中的这种“旧名新意”的现象成为了反映物理学发展的一种重要形式．在此集中探讨“力”这一概念在物理学的一些分支理论中的含义和地位的差别．对这一课题的探讨不仅可以使我们对物理学中的“力”会有更深刻的理解,这些差别也在相当大的程度上反映了物理学的发展历程．     

惯性,惯性力及其辨析

从惯性,惯性力的概念出发,分析讨论了牛顿惯性力,欧拉惯性力,达朗贝尔惯性力及变质量问题的惯性力的异同,论述了惯性力性质与实质。     

Some open problems in granular matter mechanics

Granular matter is a large assemblage of solid particles, which is fundamentally different from any other type of matters, such as solid and liquid. Most models presented for granular matter are phenomenological and are only suitable for solving engineering problems. Many fundamental mechanical problems remain open. By analyzing characteristics of internal state structure, we propose that granular matter is intrinsically multiscale, i.e. microscale of particle size, mesoscale of force chain, and macroscale of the bulk of granular matter. The correlations among difference scales would be crucial. The mesoscale force chain network is determined by both particle properties and macroscopic boundary conditions. The evolution of the force the chain network contributes to macroscopic mechanical properties of granular matter. In addition, we discuss the drawbacks in simplifying contact forces in the current models, and the difficulties in analyzing the interaction of interstitial fluid in wet granular matter. As an appropriate application of granular matter, debris flow can be studied with granular matter mechanics; meanwhile, debris flow brings more challenges which certainly motivate future studies on granular matter.     

两种典型覆冰导线气动力特性及稳定性分析

通过节段模型高频天平测力风洞试验,计算了准椭圆形和扇形两种代表性覆冰导线的气动力系数均值、均方根值.基于准定常假设对试验模型的单自由度驰振可能性进行了分析.所得结果为研究类似截面形状覆冰导线的气动特性提供了参考,为进一步计算覆冰导线响应提供了基础数据.     

植物动力2003对水稻秧苗素质影响的研究初报

本文探讨了植物动力2003对水稻秧苗苗高、绿叶数、叶挺长、总根数、白根数、分蘖数、秧苗最大叶片的长度和宽度等秧苗素质的影响。结果表明.喷施植物动力2003的水稻秧苗粗壮,分蘖多,根系发达,各项指标均明显优于对照。     

关于洛仑兹力中v的讨论

本文利用力的坐标变换关系和电磁场的坐标变换关系,对洛仑兹力公式中的v进行了专门讨论.说明速度是运动电荷相对观察者之速度,而不是运动电荷相对磁场之速度.     

倾斜隔仓板磨机筒体无纵向位移的条件

在装有倾斜隔仓板磨机的运转过程中,由研磨体产生的纵向力周期性地作用到磨机筒体上,使磨机筒体沿其纵向轴线移动,从而对磨机造成破坏,本文通过研究筒体所在轴承座中的摩擦力,得到了筒体无纵向位移的必要与充分条件。     

两种捡膜齿滚筒结构对工作性能影响的对比分析

比较了伸缩扒杆滚筒和弧型捡膜齿滚筒的结构特点以及在捡膜齿捡膜时的受力情况。伸缩扒杆滚筒由于结构本身的问题导致工作部件受力较大;弧型捡膜齿滚筒结构相对比较合理,工作部件受力较小。应用结果表明：伸缩扒杆滚筒工作时工作部件磨损严重,故障率高,捡拾性能差;而弧型捡膜滚筒工作时工作部件磨损不严重,故障率低,捡膜能力强。     

Hertz's Mechanics and a unitary notion of force

Heinrich Hertz dedicated the last four years of his life to a systematic reformulation of mechanics. One of the main issues that troubled Hertz in the customary formulation of mechanics was a ‘logical obscurity’ in the notion of force. However, it is unclear what this logical obscurity was, hence it is unclear how Hertz took himself to have avoided it.In this paper, I argue that a subtle ambiguity in Newton's original laws of motion lay at the basis of Hertz's concerns; an ambiguity which led to the development of two slightly different notions of force. I then show how Hertz avoided this ambiguity by deriving a unitary notion of force, thus dispelling the obscurity that lurked in the customary representation of mechanics.