Summary of studies of the η meson production with polarized proton beam at COSY‐11
We report on the COSY‐11 measurements of the analysing power for the pp→ppη reaction and interpret the results in the framework of the meson exchange models.
POLARIZATION PHENOMENA IN NUCLEAR REACTIONS.
The recent appearance of high-intensity polarized beams with a small energy spread has made feasible a number of experiments which could not have been considered just a few years ago. In many reactions, polarization parameters can often be measured almost as easily as cross sections. The volume of experimental data can thus be expected to increase rapidly; the results should be precise and reliable. The problem of explaining the measurements and drawing from them all the information about nuclear structure and nuclear reaction mechanisms that they contain is likely to severely challenge standard reaction theories.
Numerical analysis of surface crack propagation in flexible pavements using XFEM and cohesive zone model
Surface initiated (top-down) cracking in the longitudinal direction of pavements has become a predominant mode of failure in thick asphalt pavements. Most previous researchers studied crack propagation using the traditional Linear Elastic Fracture Mechanics (LEFM) method by calculating the stress intensity factor around the crack tip. In this paper, Extended Finite Element Method (XFEM) was used to study the key factors causing surface initiated crack propagation under surface tension and/or shear. A two-dimensional (2-D) finite element (FE) model for a two-lane flexible pavement was built to predict pavement responses and crack propagation potential under various scenarios. It was found that surface tension is the major driving force for crack propagation when the crack is at some distance away from tire loading. The results show that the distance from the location of crack to tire loading, the depth and direction of the crack, and the modulus ratio between the hot-mix asphalt (HMA) layer and the base layer have significant influences on crack propagation under surface tension. On the other hand, this study shows that shear stress can induce surface initiated crack propagation near the loading area as the shear resistance of material becomes low at the high temperature.