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1.
姜泽辉  郭波  张峰  王福力 《物理学报》2010,59(12):8444-8450
分析了摩擦力对竖直振动台面上完全非弹性蹦球动力学行为的影响.当控制参数Γ由1逐渐增大时,作用在蹦球上的恒定摩擦力不会改变倍周期分岔的序列,但会使倍周期分岔点的数值变大.与无摩擦力时的情况相比,在飞行时间的分岔图中也存在倍周期分岔密集区,只是被横向拉伸纵向压缩,且具有不同的分形特性.与受振颗粒体系中的倍周期分岔过程做了比较,发现当摩擦力取值为颗粒总重量的20%—30%时两者符合很好.  相似文献   

2.
完全非弹性蹦球的动力学行为   总被引:1,自引:0,他引:1       下载免费PDF全文
姜泽辉  郑瑞华  赵海发  吴晶 《物理学报》2007,56(7):3727-3732
对振动台面上的完全非弹性球的蹦跳行为进行了初步分析.受约化振动加速度的控制,球的运动可以表现出一系列倍周期分岔过程.对几种典型的倍周期运动及分岔情况进行了讨论. 关键词: 蹦球 倍周期分岔 混沌 颗粒物质  相似文献   

3.
一个在振动台面上蹦跳的小球具有复杂的运动形式,如倍周期分岔和混沌.如果球与台面间的碰撞是完全非弹性的,则球的运动是倍周期的,不存在混沌.在分岔相图中,鞍一结不稳定性引入“平台”结构,同时存在倍周期轨道的密集区.这里将研究空气的黏滞阻力对完全非弹性蹦球动力学行为的影响.分析表明,空气阻力很弱时,分岔序列不受影响,但分岔点的数值变大,“平台”和密集区加宽.空气阻力较大时,“平台”与密集区重叠.重叠区内原有产生倍周期运动的机理被破坏,球的运动是混沌的.  相似文献   

4.
韩红  姜泽辉  李翛然  吕晶  张睿  任杰骥 《物理学报》2013,62(11):114501-114501
颗粒物质由离散的固体颗粒组成, 受到周期性振动时可以表现出复杂的动力学行为. 这些行为往往受众多因素的影响, 如空气阻力和器壁摩擦力等. 针对受振颗粒体系中冲击力的倍周期分岔现象, 通过抽真空或将容器底镂空消除空气阻力, 单独研究器壁滑动摩擦力的影响. 结果表明在仅有器壁摩擦力作用的情况下, 倍周期分岔过程仅受约化振动加速度的控制, 与颗粒的尺寸、颗粒层数及振动频率无关. 将器壁摩擦力处理成一个大小恒定、方向与颗粒和器壁相对速度反向的阻力, 并包含到完全非弹性蹦球模型中, 能够对所观察到的现象给出很好的解释. 通过对倍周期分岔点测量平均值的拟合, 得到器壁滑动摩擦力的大小约为颗粒总重量的10%. 关键词: 颗粒物质 器壁摩擦力 倍周期分岔 冲击力  相似文献   

5.
竖直振动颗粒床中的倍周期运动   总被引:2,自引:0,他引:2       下载免费PDF全文
姜泽辉  刘新影  彭雅晶  李建伟 《物理学报》2005,54(12):5692-5698
实验研究了竖直振动颗粒床中颗粒对容器底部的压力随振动强度的变化情况.发现压力随振动加速度的增加经历倍周期分岔,典型的分岔序列为:2P,4P,混沌,3P,6P,混沌,4P,8P,混沌.观察表明,伴随倍周期分岔现象,在颗粒床底部出现颗粒的聚集态.聚集态内颗粒密堆积在一起并作整体的上下运动.采用完全非弹性蹦球模型分析了颗粒对容器底的冲击力,并给出了倍周期分岔现象的一种解释. 关键词: 颗粒物质 混沌 倍周期分岔 非弹性碰撞  相似文献   

6.
姜泽辉  王运鹰  吴晶 《物理学报》2006,55(9):4748-4753
实验研究了竖直振动情况下,窄容器中颗粒的运动模式.发现运动模式与颗粒床厚度及振动加速度有很强的依赖关系.实验表明横向尺寸较小的容器可以抑制对流卷及拱起现象.对于足够厚的颗粒床,即使振动加速度很大,颗粒床下部仍然存在着颗粒聚集态.出现聚集态时,颗粒床对容器底的冲击力是倍周期分岔的.实验表明倍周期分岔点与颗粒床厚度无关.对于较薄的颗粒床,颗粒可以是聚集态或对流卷,视颗粒尺寸而定.如果使用尺寸分布非常窄的球形颗粒,可以观察到颗粒的有序排列.出现同心的圆筒形“壳”结构,每个“壳”上的颗粒是二维六角密排列的. 关键词: 颗粒物质 倍周期分岔 颗粒聚集态 球堆积  相似文献   

7.
实验研究了竖直振动颗粒床中,倍周期运动对尺寸分离的影响.实验中,当振动加速度足够大时,系统中出现稳定的对称对流,进一步增大振动加速度到某个临界值时,还会出现倍周期运动.观察表明,背景颗粒的对流运动对分离过程起主导作用,对流速度决定着分离过程的快慢,而在2倍周期和4倍周期分岔之后,分离时间有所减慢.对引起对流运动的起因进行了分析,以此为基础分析了倍周期运动产生影响的物理机理,并对分离时间进行了定量计算,结果与实验值符合很好. 关键词: 颗粒物质 “巴西果”效应 倍周期分岔 对流  相似文献   

8.
竖直振动颗粒物厚层中冲击力分岔现象   总被引:5,自引:0,他引:5       下载免费PDF全文
实验研究了竖直振动颗粒物厚层中颗粒对容器底部的压力. 发现这种压力是脉冲式的,并表现出受振动加速度控制的倍周期分岔现象. 在颗粒层底部观察到颗粒密堆积在一起的聚集态. 聚集态内颗粒的自由程较小,并像一个整体一样运动. 关键词: 颗粒物质 混沌 倍周期分岔 非弹性碰撞  相似文献   

9.
王亮  徐伟  李颖 《物理学报》2008,57(10):6169-6173
研究了一类二自由度碰撞振动系统在随机噪声激励下的响应问题.展示了这种非光滑系统在倍周期分岔通向混沌的道路中存在的擦边分岔行为.通过定义一种随机响应的度量,讨论了随机噪声对于系统响应的影响,并发现在某些参数条件下,随机噪声对于系统响应的影响是明显的,甚至改变了运动的性质.数值模拟表明此法是研究噪声激励下非光滑系统响应的一种有效方法. 关键词: 非光滑系统 二自由度碰撞振动系统 擦边分岔 倍周期分岔  相似文献   

10.
刘扬正  林长圣  李心朝 《物理学报》2011,60(6):60507-060507
拓展和改变Lorenz混沌系统的非线性函数,构建一个新的具有光滑二次函数的自治混沌系统,系统包含3个系统变量乘积的非线性函数项和5个平衡点,详细讨论了平衡点的性质并计算了分形维数.利用分岔图和Lyapunov指数谱对系统随参数变化的情况进行分析后得出,系统会发生倍周期分岔.用数字信号处理芯片对混沌系统进行硬件实现,实验结果表明理论分析的正确性以及系统具有较为复杂的动力学行为. 关键词: 混沌系统 分岔图 Lyapunov指数 数字信号处理  相似文献   

11.
Equations of fractal motion of electrons with variable weak memory and nonlocality are investigated. It is demonstrated that the fractal dimension of time changes by a harmonic law for stationary electron motion. The fractal nonlocality has been established for the free electron; it also changes by a harmonic law. The fractal nonlocality of the electron bound with the hydrogen atom nucleus differs radically. In this case, the fractal dimension of radial electron motion is everywhere less than unity. It can be greater than unity in regions well away from the nucleus. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 52–57, September, 2005.  相似文献   

12.
Based on the fractal distribution of nanoparticles, a fractal model for heat transfer of nanofluids is presented in the Letter. Considering heat convection between nanoparticles and liquids due to the Brownian motion of nanoparticles in fluids, the formula of calculating heat flux of nanofluids by convection is given. The proposed model is expressed as a function of the average size of nanoparticle, concentration of nanoparticle, fractal dimension of nanoparticle, temperature and properties of fluids. It is shown that the fractal model is effectual according to a good agreement between the model predictions and experimental data.  相似文献   

13.
分形结构对随机取向烟尘团簇粒子光散射特性的影响   总被引:1,自引:0,他引:1  
利用蒙特卡罗方法对不同分形维数和分形前向因子的随机取向烟尘团簇粒子的分形结构进行了仿真,采用离散偶极子近似(DDA)方法对随机取向烟尘团簇粒子的缪勒矩阵元进行了数值计算,并与球形粒子模型进行了比较,深入探讨了烟尘团簇粒子的分形维数和分形前因子对其散射特性的影响。研究表明,等效球形粒子的光散射特性与随机取向烟尘团簇粒子的光散射特性存在很大差别,并且此差别随着团簇粒子的分形维数以及分形前向因子的增大而减小;分形维数对表征团簇粒子散射特性的缪勒矩阵元的影响在一定散射角范围内均比较明显,分形前向因子对团簇粒子的缪勒矩阵元角分布的影响与分形维数的影响类似,不过其影响相对分形维数较弱。  相似文献   

14.
Regular and stochastic oscillations in a simple periodically forced vibroacoustic system with a piecewise-linear (bimodular) elasticity are considered from the viewpoint of their statistical properties: oscillation spectra, the largest Lyapunov exponents, and fractal dimension. It is shown that a strange attractor exists in a limited range of parameters together with a triple-period dynamic cycle being absorbed by the latter at some finite value of the parameter. The corresponding bifurcation process is followed in detail. (c) 1995 American Institute of Physics.  相似文献   

15.
It is shown that fractal dimensions along line transects of a stationary, stochastic surface are all identical to one another, save that in one special direction the dimension may be less than in all others. We discuss the implications of this result for practical measurement of surface roughness and for interpretation of fractal dimension. It is argued that the result provides significant new motivation for employing fractal dimension as a canonical measure of surface roughness. Nevertheless, in view of the virtual direction-invariance of fractal dimension, measurement of scale assumes new significance. This matter is addressed.  相似文献   

16.
周洁  杨双波 《物理学报》2014,63(22):220507-220507
研究了周期受击陀螺系统波函数的分形. 发现在打击强度系数较弱时 (即≤ 1时), 相空间是规则的, 分形维接近于1; 随着打击强度系数的增大, 相空间开始变得混沌, 分形维也随之增大; 当打击强度系数达到6时, 相空间完全混沌, 分形维将达到最大值, 此时若继续增大打击强度系数, 分形维保持基本不变. 关键词: 陀螺 波函数 分形维 相空间  相似文献   

17.
Self-similarity in multiple processes at high energies is considered. It is assumed that a parton cascade transforms into a hadron shower with a fractal structure. The box counting (BC) method used to calculate the fractal dimension is analyzed. The parton shower with permissible 1/3 parts of pseudorapidity space, which corresponds to a triadic Cantor set, was used as a test fractal. It was found that there is an optimal set of bins (a parameter of the BC method) that allows one to find the fractal dimension with maximal accuracy. The optimal set of bins is shown to depend on the fractal generation law. The P-adic coverage (PaC) method is proposed and used in the fractal analysis. This method makes it possible to determine the fractal dimension of a shower as accurately as possible, the number of fractal levels and partons at each branching point during the parton shower evolution, the type of cascade (either random or regular), and its structure. It is shown to be applicable to an analysis of the regular and random N-ary cascades with permissible 1/k parts of the space studied.  相似文献   

18.
Ion-stimulated growth of a fractal cluster on the substrate is simulated in regimes that are intermediate between diffusion- and reaction-limited aggregations. It is shown that the fractal dimension of a growing cluster and the type of formed epitaxial structure are due to the sequence of ion-stimulated processes with different fractal dimensions. The algorithm for revealing the ion stimulation mechanism of processes based on fractal laws is proposed.  相似文献   

19.
The effect of morphologic factors on magnetic flux trapping and critical currents in a superconducting structure, which presents a type II percolation superconductor with pinning centers, is considered. The role of pinning centers is played by fractal clusters of the normal phase. The properties of these clusters are analyzed in detail: their statistics is studied, the distribution of critical currents of depinning is found, and the depen-dences of the main statistical parameters on the fractal dimension are obtained. The effect of fractal clusters of the normal phase on the electric field caused by the motion of the magnetic flux after the vortices have been broken away from pinning centers is considered. The current-voltage characteristics of superconducting structures in a resistive state are obtained for an arbitrary fractal dimension. It is found that the fractality of the boundaries of normal-phase clusters forces magnetic flux trapping, thereby increasing the critical current.  相似文献   

20.
The fractal dimension of the boundaries of clusters formed by pores and granules in polycrystalline materials is shown to be determined by the sample density and crystallite sizes. The dependence of the fractal dimension on the density has a maximum. It is shown that the maximum diamagnetic response can be obtained in a porous high-temperature superconductor with a porosity of 50?C60% and small crystallite sizes.  相似文献   

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