Modelling and analysis of bacterial tracks suggest an active reorientation mechanism in Rhodobacter sphaeroides

Most free-swimming bacteria move in approximately straight lines, interspersed with random reorientation phases. A key open question concerns varying mechanisms by which reorientation occurs. We combine mathematical modelling with analysis of a large tracking dataset to study the poorly understood reorientation mechanism in the monoflagellate species Rhodobacter sphaeroides. The flagellum on this species rotates counterclockwise to propel the bacterium, periodically ceasing rotation to enable reorientation. When rotation restarts the cell body usually points in a new direction. It has been assumed that the new direction is simply the result of Brownian rotation. We consider three variants of a self-propelled particle model of bacterial motility. The first considers rotational diffusion only, corresponding to a non-chemotactic mutant strain. Two further models incorporate stochastic reorientations, describing ‘run-and-tumble’ motility. We derive expressions for key summary statistics and simulate each model using a stochastic computational algorithm. We also discuss the effect of cell geometry on rotational diffusion. Working with a previously published tracking dataset, we compare predictions of the models with data on individual stopping events in R. sphaeroides. This provides strong evidence that this species undergoes some form of active reorientation rather than simple reorientation by Brownian rotation.     

Interaction rules underlying group decisions in homing pigeons

Travelling in groups gives animals opportunities to share route information by following cues from each other''s movement. The outcome of group navigation will depend on how individuals respond to each other within a flock, school, swarm or herd. Despite the abundance of modelling studies, only recently have researchers developed techniques to determine the interaction rules among real animals. Here, we use high-resolution GPS (global positioning system) tracking to study these interactions in pairs of pigeons flying home from a familiar site. Momentary changes in velocity indicate alignment with the neighbour''s direction, as well as attraction or avoidance depending on distance. Responses were stronger when the neighbour was in front. From the flocking behaviour, we develop a model to predict features of group navigation. Specifically, we show that the interactions between pigeons stabilize a side-by-side configuration, promoting bidirectional information transfer and reducing the risk of separation. However, if one bird gets in front it will lead directional choices. Our model further predicts, and observations confirm, that a faster bird (as measured from solo flights) will fly slightly in front and thus dominate the choice of homing route. Our results explain how group decisions emerge from individual differences in homing flight behaviour.     

基于SolidWorks Simulation液压支架平衡千斤顶铰接销轴有限元分析

通过对不同简化条件下运用传统材料力学方法与SolidWorks Simulation有限元方法对液压支架平衡千斤顶铰接销轴进行力学计算与有限元分析对比,在正确设置边界条件、载荷、约束并且合理划分网格的情况下,SolidWorks Simulation有限元分析方法简单易行,更能接近实际工况,对设计工作起到很好的指导、参考作用。     

基于ARAMIS M/E微震监测的大采高综放顶板活动规律

采用高精度微震监测技术,结合现场支架阻力观测,对大采高综放开采顶板活动规律进行了研究。研究表明：微震事件的频次和能量具有明显的周期性,微震事件在高度上的动态发展规律反映出大采高综放顶板来压存在大小周期现象,且这种现象与工作面宏观观测得到的周期来压具有一致性;根据微震监测和支架阻力观测结果得出大采高综放开采顶板为“悬臂梁-铰接岩梁”结构。     

基于SolidWorks的自行走装置的设计

介绍了基于SolidWorks软件进行机械系统虚拟设计和运动仿真的基本方法,综合利用SolidWorks的参数化、变量化建模技术,完成了集装箱双侧装卸车自行走装置的虚拟设计。利用SolidWorks的插件SolidWorksmotion对自行走装置的收放及转向进行了运动仿真。利用SolidWorks的插件simulation对驱动轮支臂进行有限元分析。实践证明,这种方法可有效提高效率,具有良好的应用前景。     

某自行加榴炮操作训练弹卡弹可靠性改进

针对某型自行加榴炮操作训练弹使用时出现的高角掉弹问题,提出改进后的一种新型操作训练弹设计方案。从可能导致卡弹力降低、产生输弹阻力等因素对比进行卡弹可靠性分析,找出问题原因,提出采用分体式弹体设计、增加滑块锁紧机构、改变导带材料等措施,并在原有基础上进一步优化。验证结果表明:新型操作训练弹操作更加方便简单,退弹效率和操作可靠性进一步提高。     

BGC-100抱罐车研制

针对国内现代化钢厂规模化生产对研制大吨位抱罐车提出的要求,研制了BGC-100式抱罐车.介绍了BGC-100式抱罐车的结构组成,技术特征及创新点.     

连杆机构可视化设计和模拟研究

介绍连杆机构构件的建模方法和用ＡｃｔｉｖｅＸ技术实现连杆机构可视化设计和模拟的原理和过程。     

协同优化方法及铰接式自卸车系统设计协同优化模型

对协同优化方法的基本思想、计算框架、研究现状及发展进行了分析论述,并将协同优化方法引入到铰接式自卸车(ADT)系统设计中,叙述了对铰接式自卸车进行协同优化的必要性,对ADT系统进行分解,建立协同优化模型,并提出协同优化方法的求解思路。     

故障树分析法在某型轮式自行火炮故障诊断中的应用

某型轮式自行火炮由于服役时间短,故障数据和信息缺乏,因此难以掌握其在部队使用中的故障规律。针对这一现状,本文首先介绍了故障树分析法的原理,然后分析了该自行火炮故障的定义及分类,最后结合该装备构筑了相应的故障树,从定性和定量两个角度进行分析;实践证明：故障树分析法能从故障现象着手快速判断、分析故障原因及其逻辑关系,对某型轮式自行火炮故障的分析和定位具有较好的适用性。