Numerical simulation of free shear flows and far-field sound pressure directivity

An implicit spatial differencing technique with fourth-order accuracy has been developed based on the Pade compact scheme. A dispersion-relation-preserving concept has been incorporated into the numerical scheme. Two-dimensional Euler computation of a spatially developing free shear flow with and without external excitation has been performed to demonstrate the capability of the numerical scheme developed. Results are in good agreement with theory and experimental observation regarding the growth rate of the fluctuating velocity, the convective velocity and the vortex-pairing process. The far-field sound pressure generated by the computed shear flow solution using Lighthill's acoustic analogy shows a strong directivity with a zone of silence at the flow angle.     

非均匀磁场中的剪切阿尔芬波涡旋

本文研究了非均匀磁场中非线性剪世阿尔芬波，研究表明，在非均匀磁场情况下，阿尔芬波通过自相互作用也可以形成避域涡旋结构。磁场的非均匀性将导致传播区的展宽。     

Measurement of residual wedge angle with a reversal shear interferometer

A technique for determination of residual wedge angle of high optical quality transparent parallel plate using a reversal shear interferometer-based optical system has been discussed. In this technique the parallel plate to be tested is used to introduce angular tilt in the preset two-beam interference fringes of a reversal shear interferometer. The parallelism is calculated from the angular tilt of the fringes. The technique is more sensitive compared to techniques using Fizeau interferometer and is most suitable for highly parallel transparent plate with very low residual wedge angle.     

On Unsheared Tetrads

Assuming the existence of genuine unsheared triads, we examine the possibility of having unsheared tetrads, particularly unsheared genuine tetrads.     

定常流下动脉狭窄局部流场的有限元分析

本文利用有限元数值模拟对定常流下动脉狭窄的局部流场进行了系统研究。在数值模拟中求解非线性轴对称Navier-Stokes方程,并对不同狭窄率、不同雷诺数、不同狭窄形状下的流场速度分布、压力降分布和壁面剪应力分布进行了全面细致的分析和讨论。     

Ultrasonic inspection of stainless steel butt welds using horizontally polarized shear waves

Inspection of austenitic stainless steel weldments by conventional ultrasonic means is fundamentally limited by the textured, columnar grain structure of the weld metal. It is shown that, for selected angles of incidence, shear waves normally polarized with respect to the columnar grains can pass through the weld metal-base metal interface without partial reflection. As a consequence, the inspectability of stainless steel weldments can be improved. The operation of a low frequency, ultrasonic system for stainless steel butt weldments is demonstrated.     

Equation of State of Hot Neutrino Opaque Interior Matter of Neutron Star

The equation of state of hot neutrino opaque interior matter of the neutron star and some of its properties such as the free energy, effective mass, adiabatic index, and temperature are calculated along both isothermal and isentropic paths with the AV ₁₈ and AV ₁₄ potentials using the lowest order constrained variational method. We have shown that the calculated equation of state with the AV ₁₈ potential is harder than with the AV ₁₄ potential. It is found that there is no phase transition in the hot neutrino opaque interior matter of the neutron star. We have shown that for all values of density and entropy, the adiabatic index of neutron star matter is greater than . It is shown that our calculated equations of state obey the causality condition.     

Moment Mechanics of Composites

Based on the gradient (multimoment) theory of composites, the stress-strain state in structural elements is analyzed. Approximate formulas for the moduli and stresses of fibrous composites in longitudinal shear and other stress states are found. The effect of scale parameters on the state of supercomposites is revealed.     

Shear Flow of a Granular Material

The shear flow of a granular material between parallel plates is treated by means of the Boltzmann equation with pseudo-Maxwellian grains. The moments for reverse reflection boundary conditions are found explicitly. The shearing stress is found to depend quadratically on the shear rate.     

Spin-Flip and Elastic Processes in Slow Collisions of Mesic Atoms

The reduced adiabatic hyperspherical (RAHS) basis suggested previously is used for the calculation of elastic and spin-flip cross sections in the processes (aμ) _F + a → (aμ) _F′ + a, a = (p, d, t), for collision energies 10⁻³ ≤ ε ≤ 10² eV. The rapid convergence of the method is demonstrated. A comparison of the obtained results with previous ones is presented. This revised version was published online in August 2006 with corrections to the Cover Date.