Galin's theorem holds for moving punch

This paper presents a formulation for solving three-dimensional moving punch problem. It proves that Galin's theorem holds for the punch. As an example, the study offers some results (including numerical data) of dynamic displacement over an ellipse contact region.     

An approximate maximum likelihood estimation for non-Gaussian non-minimum phase moving average processes

An approximate maximum likelihood procedure is proposed for the estimation of parameters in possibly nonminimum phase (noninvertible) moving average processes driven by independent and identically distributed non-Gaussian noise. Under appropriate conditions, parameter estimates that are solutions of likelihood-like equations are consistent and are asymptotically normal. A simulation study for MA(2) processes illustrates the estimation procedure.     

Computation of turbulent free‐surface flows around modern ships

This paper presents the calculated results for three classes of typical modern ships in modelling of ship‐generated waves. Simulations of turbulent free‐surface flows around ships are performed in a numerical water tank, based on the FINFLO‐RANS SHIP solver developed at Helsinki University of Technology. The Reynolds‐averaged Navier–Stokes (RANS) equations with the artificial compressibility and the non‐linear free‐surface boundary conditions are discretized by means of a cell‐centred finite‐volume scheme. The convergence performance is improved with the multigrid method. A free surface is tracked using a moving mesh technology, in which the non‐linear free‐surface boundary conditions are given on the actual location of the free surface. Test cases recommended are a container ship, a US Navy combatant and a tanker. The calculated results are compared with the experimental data available in the literature in terms of the wave profiles, wave pattern, and turbulent flow fields for two turbulence models, Chien's low Reynolds number k–εmodel and Baldwin–Lomax's model. Furthermore, the convergence performance, the grid refinement study and the effect of turbulence models on the waves have been investigated. Additionally, comparison of two types of the dynamic free‐surface boundary conditions is made. Copyright © 2003 John Wiley& Sons, Ltd.     

用涡方法数值模拟运动物体非定常流场

采用涡方法对静止圆柱绕流、简谐振动圆柱、静止NACA0012翼型绕流和运动扑翼的非定常流场进行了数值模拟和数值验证,对比验证结果较好.控制方程采用二维不可压缩N-S方程,根据算子分裂法,对流和扩散分别采用不同的时间步长.涡方法基于Lagrange坐标系的特点使其方便模拟运动物体的非定常流场.本文的工作为今后的翼型动态失...     

Parametric ergodicity to measure roughness from a single sample

We introduce a concrete random model system to study the concept of parametric ergodicity. It consists of a continuum mechanical cavity with an embedded random mass distribution, constrained by a parametrized boundary condition. The interest is twofold. On one hand, there is the practical interest of obtaining ensemble averages of physical quantities from a small number of experimentally available samples, in many cases only one. This is typically the case in studies on conductance fluctuations through disorder mesosocopic systems. On the other hand we want to develop more insight into the meaning of parametric ergodicity. For this, we focus on the statistical distribution of resonant frequency generated by the ensemble of random samples, and how to produce the same distribution from a single sample subject to changing a boundary condition — the external parameter. The paper shows how the changing of the boundary condition is equivalent to scanning the ensemble of equivalent samples.     

一种单目运动像机对点状运动物体的三维定位方法

针对单目运动像机无法确定点状运动物体三维位置的难题,提出了一种求解点状运动物体三维位置的方法,利用直线在其法平面上的投影为点这个特性,将各时刻像机光心与物体位置的连线(以下称观察视线)投影到以运动物体轨迹为法线的平面上,通过迭代使其投影线交于一点,交点对应的直线就是物体的运动轨迹,仅需要取大于等于5个时刻的数据就可以确...     

Moving averages of ordinary differential equations via convolution

We introduce an averaging framework, where the solution of a time-varying equation with a small amplitude is approximated by the solution of a slowly-varying auxiliary system, generated by convolving the original equation with a kernel function. The effect of the convolution is smoothing of the equation, thus, making it more amenable to numerical computations. We present tight results on the approximation error for general classes of vector fields and kernels.     

Dynamic response of clamped axially moving beams: Integral transform solution

The generalized integral transform technique (GITT) is employed to obtain a hybrid analytical-numerical solution for dynamic response of clamped axially moving beams. The use of the GITT approach in the analysis of the transverse vibration equation leads to a coupled system of second order differential equations in the dimensionless temporal variable. The resulting transformed ODE system is then solved numerically with automatic global accuracy control by using the subroutine DIVPAG from IMSL Library. Excellent convergence behavior is shown by comparing the vibration displacement of different points along the beam length. Numerical results are presented for different values of axial translation velocity and flexural stiffness. A set of reference results for the transverse vibration displacement of axially moving beam is provided for future co-validation purposes.