共查询到20条相似文献,搜索用时 93 毫秒
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桂祖华 《应用数学和力学(英文版)》1996,17(7):659-663
NEWTON'STHEOREMWITHRESPECTTOALOTOFCENTERSANDTHEIRAPPLICATIONS¥(桂祖华)GutZuhua(DepartmentofAppliedMathematicsofShanghaiJiaotongUn... 相似文献
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本文对曲棍球运动中一些物理性质进行了实验测定,并给出了结果.主要包括有棍的质量、重心、转动惯量和撞击中心(即击球区和握棍区的关系问题),球的质量和直径,以及棍和球碰撞时的恢复系数等.这对今后曲棍球运动的深入研究,提供了定量的基础.另外在处理实验数据方面提出了一些适合于实际情况的修正公式. 相似文献
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We reported some dynamic and viscometric data on an Australia strong flour-water dough. In oscillatory shear flow experiments, we found the linear viscoelastic strain limit is extremely low, of O(10–3), consistent with other published data on doughs. The relaxation spectrum derived from the dynamic data is broad, indicating the blend nature of dough. In the start-up of a simple shear flow, we found the shear stress increases nonlinearly with time to a peak value and then decreases rapidly, with no steady-state response. The concept of steady-state viscosity is not very meaningful here, unless the strain at which the measurements are taken is also specified. The stress peaks are strain-rate dependent; but they occur at a strain of O(10), for the strong flour/water dough used, over four decades of strain rates. The experimental data were used to construct a phenomenological model for dough, consisting of an hyperelastic term (representing the elastic gluten network of permanent cross-linked long chain polymers), and a viscoelastic contribution (representing the suspension of starch globules and other long-chain components in dough that are not parts of the permanent cross-linked gluten network). The model predictions compared favourably with experimental data in oscillatory and shear flows. 相似文献
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When a dissipative dynamical system has multiple attractors, it is a task to determine and recognize the global domain of attraction of each attractor. In this paper we study the global behavior of a forced hinged-clamped beam with two-mode interaction. The equation of motion of the beam is reduced to four first-order autonomous ordinary differential equations. The system has an internal resonance condition of 2 31, where 1 and 2 denote natural frequencies of the first and second modes, respectively. When the excitation frequency is near 1, the system can have three equilibrium solutions, among which two are asymptotically stable and one is unstable. We examine how the domains of attraction of two stable equilibrium solutions evolve as the forcing frequency is varied across jump points. By using a special plane which contains all equilibrium points, called the principal plane, the global domains of attraction can be discussed more effectively. Results show that knowledge of this evolution helps us better understand the jump phenomenon. 相似文献
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The underlying geometric structure of the standard OGY control scheme is analyzed. Some of the main mechanisms that under certain conditions lead to failure of the control algorithm are revealed. The limited controllability available in a system is investigated and it is shown that it may lead to serious problems that will significantly enlarge the state space region of failure of the standard OGY controller. A minimal distance algorithm is analyzed and shown to be, for some problems, more advantageous than the standard OGY technique. Nevertheless, for a broad category of problems, the minimal distance scheme is also shown to fail. As a solution for these problems, two new techniques are proposed: the penalized minimal distance and the multi-step OGY-type scheme. The standard OGY and minimal distance algorithms are particular cases of the new techniques proposed. Finally, we give a necessary condition that estimates the region of controllability under the multi-step OGY-type control. We demonstrate a significantly improved basin of convergence for the new multi-step OGY-type algorithm. 相似文献
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A pure stress formulation of linear nonhomogeneous anisotropic elastodynamics with continuously distributed defects (EcDD) is proposed, and well known solutions of ECDD corresponding to stationary and moving concentrated plastic fields in an infinite body are recovered by direct integration of the stress field equation. A new interpretation of the solutions is given. 相似文献
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A technique is developed for determining the thermoviscoelastoplastic geometrically nonlinear axisymmetric stress–strain state of laminar shells of revolution under loads that induce meridional stress and torsion. The technique is based on the hypotheses of rectilinear element for the whole stack of layers. The relations of the theory of deformations along paths of small curvature are used as equations of state. The solution is reduced to the numerical integration of a system of ordinary differential equations. The technique is tried out by a test example and illustrated by determining the geometrically nonlinear thermoviscoelastoplastic state of a corrugated shell 相似文献
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从小扰动波(马赫波)的物理概念出发,导出了不依赖流体状态方程表达形式的平面二维超声速定
常流的特征线方程;重新定义了以流体密度为单自变量的Prantl-Meyer函数,形成了求解平面二维超声速定
常流的封闭方程组。还利用这种通用物态方程的特征线差分解法,针对滑移爆轰驱动飞板运动问题构建了爆
轰产物流场内部和飞板边界特征线差分法格式。对TNT炸药和乳化炸药采用JWL状态方程和多方方程进
行了对比计算。结果表明,炸药爆轰对飞板的驱动能力与状态方程表示的炸药的做功能力是一致的。 相似文献
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In this paper we investigate the stability of some viscometric flows for a concentrated suspension model which allows for the effects of shear-induced migration, including plane and circular Couette and Poiseulle flows, and unbounded and bounded torsional flows. In the bounded torsional flow, where its radial outer boundary is assumed frictionless, an exact closeform solution is given. With the exception of torsional flows, we find that a limit point for all the steady-state solutions can exist for certain range in the parameter values. In all cases, disturbances can persist for a long time, O (H
2/a
2), where H is a dimension of the flow field, and a is the particles' radius. 相似文献
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D. F. Abzalilov 《Journal of Applied Mechanics and Technical Physics》2008,49(6):978-984
A numerical-analytical solution of an inverse boundary-value problem of aerohydrodynamics is obtained for a two-element airfoil
in the full formulation, based on the velocity distribution defined on the sought airfoil contours in a range of angles of
attack. It is demonstrated that flow separation does not occur in the entire range considered for a specified non-separated
velocity distribution on the upper surfaces at the maximum angle of attack and on the lower surface at the minimum angle of
attack. An example of constructing a sectional airfoil is given; verification of the results obtained is performed with the
use of the Fluent software package.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 49, No. 6, pp. 107–114, November–December, 2008. 相似文献
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The problem of the diffusion of two vortices with circulations of opposite sign is considered. An asymptotic solution of the problem is constructed for large Reynolds numbers. The vortex circulation dissipation mechanism is discussed. The results of the analytic investigation are compared with the results of numerical solution of the Navier-Stokes equations. 相似文献
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The loss of stability of laminar flow in open channel and the mechanism of sand ripple formation 总被引:2,自引:0,他引:2
IntroductionDuringthetimeofbedsurfacesedimenttransportation,sedimentparticlesofbedloadmakethecollectivemotionofvariousdifferentformsontheriverbedsurface,thustheformofbedsurfacechangesconstantly .Thiskindofcollectivemotionofsedimentparticlesonthebedsurf… 相似文献
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A. S. Vereshchagin S. N. Vereshchagin V. M. Fomin 《Journal of Applied Mechanics and Technical Physics》2007,48(3):375-384
A mathematical model is constructed and an analytical solution is obtained for the problem of a one-dimensional steady flow
of a mixture of different gases with hollow permeable particles. The case of a one-dimensional unsteady flow of such a mixture
is analyzed numerically. The numerical solutions are compared with experimental data on the motion of the peak concentration
of helium in a fixed bed filled with cenospheres (solid hollow permeable spherical particles). The permeability of cenosphere
walls and the drag coeficient of cenospheres in the gas flow are determined.
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Translated from Prikladnaya Mekhanika i Tekhnicheskaya Fizika, Vol. 48, No. 3, pp. 92–102, May–June, 2007. 相似文献
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应用辐射测温法进行爆炸火焰温度测试时,火焰发射率取经验定值的方法与火焰燃烧机理存在较大的偏差,同时测点距离与环境温湿度也会导致不同程度的热辐射衰减,从而影响爆炸火焰温度的测量精度。本文针对上述两个问题,基于大气辐射理论与光学传播规律,提出了辐射路径衰减补偿模型,结合由红外热像仪和比色测温仪测量的爆炸火焰动态发射率,对爆炸场火焰真温进行联合反演,并将测算结果与比色测温仪测得的火焰表面温度进行对比,得到了反演温度误差范围。试验结果表明,利用本文所提出的补偿模型测算得到的爆炸火焰温度,误差由补偿前的55.699%~89.847%降低到11.292%~59.077%,有效提高了外场爆炸瞬态火焰温度的测算精度。 相似文献