共查询到19条相似文献,搜索用时 78 毫秒
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运用跃变旋转矢量法,即通过旋转矢量的起点、长度和相位的变化规律对受到空气弱阻尼作用和滑动摩擦力作用的弹簧振子的振动进行了研究.讨论了在滑动摩擦力作用下空气阻尼为临界阻尼和欠阻尼情况下的弹簧振子的运动,根据阻尼和初值情况得出不同的振动曲线.并对弹簧振子4种相图和相图旋转矢量进行了比较. 相似文献
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针对人教版选修教材中简谐运动实验中的不足,对该实验装置进行了改进.改进后的实验装置在弹簧振子两端加2个滑环,并用铁丝穿过滑环,以防止弹簧振子在振动过程中旋转,且可以减小摩擦;同时又用磁性笔代替绘图笔,由慢速电机(旋转可调)牵引磁性黑板,以实现描述弹簧振子的运动轨迹的目的. 相似文献
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<正> 国内多数单位在照相复制度盘时,工件与母板用弹簧夹紧,然后放在旋转台上,在6千瓦氙灯下曝光。我们认为这一工艺有以下缺点: 1.弹簧夹紧会导致一定的机械变形。2.氙灯产生大量的热(强红外辐射)会使红矾分解而引起虫胶热固化(俗称“灰雾”)。这样减少了曝光和显影宽容度,又引起了工件与母板不均匀的热变形。为了达到均匀曝光,我们改用了一种可旋转紫外曝光装置,曝光过程中工件与母板不动,而光源旋转,工件依靠重力自然与母板接触。实践证明,新工艺复制精度可达1″。下面将该装置作一简单介绍: 相似文献
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针对带有电荷的弹簧摆施加在竖直方向的匀强磁场的背景下,通过牛顿力学的方法得到了其运动学方程,从而发现其摆动平面在不停的进行旋转.同时按照初始条件的不同,将其在水平方向上的运动学方程化简为不同的曲线方程,进而得到了其运动的轨迹特征. 相似文献
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《物理学报》2016,(20)
在许多精密科学实验和测试中,对地面垂直振动的有效隔离影响着实验结果和测试结果的精度.本文提出一种全新的两级摆杆结构的超低频垂直隔振系统,在原理分析的基础上,设计并实现了该系统的样机.两根水平摆杆放置在同一竖直平面,绕各自铰链旋转,上摆杆通过普通弹簧悬挂于基座,下摆杆通过零长弹簧悬挂于上摆杆.系统通过光电探测方法检测两根摆杆的夹角作为误差信号,经过闭环控制将反馈力作用于上摆杆,使两根摆杆的夹角为零.零长弹簧悬挂点的位置与系统刚度有着密切关系,通过精细地调节弹簧悬挂点的位置,合理地设置控制参数,可以实现一个本征频率低至0.01 Hz的系统.理论上,该系统相对于被动式垂直隔振系统具有更好的隔振效果和抗干扰能力,相对于传统的主动式垂直隔振系统体积更小,结构更简单,有望应用于精密物理实验和科学研究当中. 相似文献
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径向基函数插值方法在动网格技术中的应用 总被引:3,自引:0,他引:3
分析用于非结构网格的弹簧比拟和用于结构网格的无限插值动态网格方法在实际应用中的优缺点,提出无需网格连接关系的基于径向基函数(radial basis functions,RBF)插值的动网格技术并编制相应的网格运动计算程序.以二维菱形翼的旋转运动及三维菱形翼的柔性变形为例,分析不同基函数和紧支半径的选取对网格质量及计算效率的影响,并通过与弹簧比拟方法的对比验证了RBF方法的有效性.结果表明:RBF方法数据结构简单,计算效率高,适应大变形能力强,可以有效地实现计算流体力学中的网格运动问题. 相似文献
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At large NAs a micro-Fresnel zone plate produces a focal spot that is more elliptical than that produced by an objective lens with the same NA. Using this anisotropy we demonstrate a method for modulating the spring constant of an optical trap by rotating the linear input polarization. The focal spot ellipticity is enhanced by the apodization factor of the zone plate and its extremely high NA. By measuring the positions of trapped particles we obtain two-dimensional histograms of particle position. These indicate that the trap spring constant is 2.75 times larger perpendicular to the incident polarization than along it. The elliptical focal spot distribution can be rotated by rotating the incident polarization, allowing the spring constant along a given direction to be modulated. 相似文献
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The wave localization in randomly disordered periodic multi-span continuous beams is studied. The transfer matrix method is used to deduce transfer matrices of two kinds of multi-span beams. To calculate the Lyapunov exponents in discrete dynamical systems, the algorithm for determining all the Lyapunov exponents in continuous dynamical systems presented by Wolf et al is employed. The smallest positive Lyapunov exponent of the corresponding discrete dynamical system is called the localization factor, which characterizes the average exponential rates of growth or decay of wave amplitudes along the randomly mistuned multi-span beams. For two kinds of disordered periodic multi-span beams, numerical results of localization factors are given. The effects of the disorder of span-length, the non-dimensional torsional spring stiffness and the non-dimensional linear spring stiffness on the wave localization are analysed and discussed. It can be observed that the localization factors increase with the increase of the coefficient of variation of random span-length and the degree of localization for wave amplitudes increases as the torsional spring stiffness and the linear spring stiffness increase. 相似文献
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K. K. Jee J. H. Han Y. B. Kim D. H. Lee W. Y. Jang 《The European physical journal. Special topics》2008,158(1):261-266
This work is related to a SMA coil spring which shows perfect recovery and greater recovery force. When tension spring of
common metals is fabricated, `initial tension' can be provided by minus pitch winding. The initial tension is the force for
tension springs to contract further in closed state. If a SMA spring has the initial tension, perfect recovery is expected
with a greater recovery force. However, the initial tension cannot be given to SMA coils in the conventional way, since heat
treatment for shape setting eliminates the tension generated by the minus pitch winding. We have developed a new method of
supplying the initial tension to SMA springs by changing coil orientation after the shape setting treatment. In this paper,
some examples are introduced that a perfect recovery with a greater force, though permanent deformation is involved in the
deformation, can be attained by the initial tension. 相似文献
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《Waves in Random and Complex Media》2013,23(3):217-227
Abstract The wave localization in randomly disordered periodic multi-span continuous beams is studied. The transfer matrix method is used to deduce transfer matrices of two kinds of multi-span beams. To calculate the Lyapunov exponents in discrete dynamical systems, the algorithm for determining all the Lyapunov exponents in continuous dynamical systems presented by Wolf et al is employed. The smallest positive Lyapunov exponent of the corresponding discrete dynamical system is called the localization factor, which characterizes the average exponential rates of growth or decay of wave amplitudes along the randomly mistuned multi-span beams. For two kinds of disordered periodic multi-span beams, numerical results of localization factors are given. The effects of the disorder of span-length, the non-dimensional torsional spring stiffness and the non-dimensional linear spring stiffness on the wave localization are analysed and discussed. It can be observed that the localization factors increase with the increase of the coefficient of variation of random span-length and the degree of localization for wave amplitudes increases as the torsional spring stiffness and the linear spring stiffness increase. 相似文献
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A model for coupled rotation-displacement modes of certain molecular crystals. Illustration for KNO3
A. Askar 《Journal of Physics and Chemistry of Solids》1973,34(11):1901-1907
A model is presented for the dynamics of crystal lattices whose elements have finite inertia and distinct equilibrium orientations. The model is based upon representing the non-central interactions by the bending of a flexible spring in analogy with the extensible spring of Born-Von Karman for central interactions in simple lattices. The model is stable for all configurations and the rotational and translational modes are coupled. The parameter expressing the bending rigidity can be determined from infrared or Raman spectroscopy and this is illustrated for a special mode of the KNO3 crystal. Dispersion relations for the lattice modes are given for a linear chain of identical molecules and KNO3 crystal. 相似文献
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