【摘 要】
:
Nature and technology often adopt structures that can be described as tubular helical assemblies.However,the role and mechanisms of these structures remain elusive.In this paper,we study the mechanical response under compression and extension of a tubular
【机 构】
:
Department of Excellence in Robotics and AI,The BioRobotics Institute,Scuola Superiore Sant’Anna,561
论文部分内容阅读
Nature and technology often adopt structures that can be described as tubular helical assemblies.However,the role and mechanisms of these structures remain elusive.In this paper,we study the mechanical response under compression and extension of a tubular assembly composed of 8 helical Kirchhoff rods,arranged in pairs with opposite chirality and connected by pin joints,both analytically and numerically.We first focus on compression and find that,whereas a single helical rod would buckle,the rods of the assembly deform coherently as stable helical shapes wound around a common axis.Moreover,we investigate the response of the assembly under different boundary conditions,highlighting the emergence of a central region where rods remain circular helices.Secondly,we study the effects of different hypotheses on the elastic properties of rods,i.e.,stress-free rods when straight versus when circular helices,Kirchhoff\'s rod model versus Sadowsky\'s ribbon model.Summing up,our findings highlight the key role of mutual interactions in generating a stable ensemble response that preserves the helical shape of the individual rods,as well as some interesting features,and they shed some light on the reasons why helical shapes in tubular assemblies are so common and persistent in nature and technology.
其他文献
针对激光制导武器当前面临着激光有源干扰而难以发挥其应有作战效能的现实,提出了双波长多模智能协同激光制导方法和具有强抗干扰能力的激光制导技术.基于激光制导武器国内外发展现状及其发展趋势,提出1.06μm脉冲激光、0.808μm连续波调制激光与北斗卫星导航系统(BDS)的双波长多模智能协同制导的总体构想.该方案通过多模智能协同制导攻击、双波长多模激光同一化探测和多模激光制导抗干扰技术实现双波长多模激光制导,1.06μm脉冲制导阶段采用随机脉冲编码防破译抗激光欺骗干扰,0.808μm连续波调制激光制导采用窄带滤
作为构建宏观物质及维持其结构的重要驱动力,非共价相互作用虽个体较弱,但其协同作用不可忽视.经过多年来对其物理本质及原理的不断探索,非共价键的研究重心已经从传统氢键延伸到其他包含多种多样结构和能量的弱相互作用.在众多的实验手段中,气相分子的转动光谱数据可以提供其他手段无可比拟的高精度,而且避免了凝聚相实验数据中环境因素的干扰,能够揭示各种非共价键相互作用的本质.同时,转动光谱对研究对象的质量分布极其敏感,即使微小的质量分布变化(如同位素取代、异构化等)也会引起其转动光谱谱图的明显变化.因此可以说转动光谱是最
利用虚像相位阵列(VIPA)的强色散能力发展而来的VIPA光谱仪是一种新型的高性能光谱测量装置,兼具宽光谱覆盖范围、高时间分辨率及高光谱分辨率等优点.基于60 GHz自由光谱区(FSR)的石英VIPA,研制了一台可用于红光波段光谱测量的VIPA光谱仪,并测量了633 nm多模激光器的出射光谱.在100μs的时间分辨率下,获得了单次3.1 nm测量谱宽、2.0 pm(1.5 GHz)的高光谱分辨率,连续4 h运行显示光谱漂移小于0.50 pm.通过采用衍射光栅扫描装置、更短曝光速度的面阵CCD和更大FSR的
马赫-曾德尔干涉仪(MZI)具有光学能量利用率高、便于视场展宽等优点,在光学滤波、鉴频等方面具有广泛的应用.然而,在实际应用中MZI频谱会受到各种因素的影响而导致性能下降.从理论上导出了在考虑入射光发散角2θ0和谱宽?ν的影响下,MZI干涉频谱的理论表达式,并定量分析了其对MZI频谱的影响.结果表明:MZI的光程差l越大,其频谱受?ν的影响越显著,l与入射光波长λ比值越大,其频谱受θ0的影响越显著;当λ=355 nm,l=3 cm时(第1种情形),?ν=10 GHz和θ0=4.5 mrad将分别使条纹对比
在多用户光码分多址(OCDMA)传输系统中,多用户干扰(MAI)严重影响系统传输性能.针对系统中多用户干扰来源于各用户码字不完全正交的特点,采用码字的自、互相关函数表达接收信号与系统损伤,引入将多用户干扰看作可重构的“有效信息”的新思路,提出了一种基于数字信号处理技术的串行反馈干扰抑制算法.搭建了2用户同步接入频谱幅度编码光码分多址(SAC-OCDMA)传输系统仿真平台,验证了该算法抑制多用户干扰的有效性.仿真结果表明:相较于光阈值器件,采用串行反馈干扰抑制算法抑制多用户干扰的效果更好,系统传输性能的改善
A novel statistical second-order reduced multiscale(SSRM)approach is established for nonlinear composite materials with random distribution of grains.For these composites considered in this work,the complex microstructure of grains,including their shape,o
Optical dynamic measurements are widely used for non-contact vibration,continuous deformation,or moving objects.Various measurement techniques were developed for different deformation amplitudes.This paper reviews three types of technique for different me
Decoding genetic information is crucial for gene therapy and cancer diagnosis,which has attracted growing interest in the field of clinical medicine and life science.In this study,we conducted a comprehensive exploration to obtain the detection mechanism
Poroelasticity of cytoplasm is a rate-and size-dependent biphasic material behavior that reflects the normal activities and pathological states of cells,mainly caused by the migration of fluid molecules and the deformation of porous solid skeleton(protein
In this paper,we derive mathematical formulas for the skin friction coefficient in wall-bounded turbulence based on the Reynolds averaged streamwise momentum equation and the total stress.Specifically,with a theoretical or empirical relation of the total