An Analytical Approach for Assessing the Collapse Strength of an Unbonded Flexible Pipe

This paper presents an analytical scheme for predicting the collapse strength of a flexible pipe, which considers the structural interaction between relevant layers. The analytical results were compared with a FEA model and a number of test data, and showed reasonably good agreement. The theoretical analysis showed that the pressure armor layer enhanced the strength of the carcass against buckling, though the barrier weakened this effect. The collapse strength of pipe was influenced by many factors such as the inner radius of the pipe, the thickness of the layers and the mechanical properties of the materials. For example, an increase in the thickness of the barrier will increase contact pressure and in turn reduce the critical pressure.

Forecasting China's Labor Supply and Demand and the Unemployment Structure in the 13th Five-Year-Plan Period

The changes in labor supply and demand are important factors affecting economic growth.The purpose of this paper is to predict and analyze the trends in China's labor supply and demand during the 13 th Five-Year Plan period and the longer period in the future.The scale and structure of the annual new entrants of labor force are predicted by accounting the numbers who are leaving from various stages of education.while trends of labor demand are predicted according to employment elasticity from the experience of industrialization of developed countries. The results show that, during the 13 th FiveYear Plan period.the scale of the new added labor would decrease slightly, with an average annual increment of around 15.68 million. At the same time.labor demand would increase steadily, with annually 15.42 million employment opportunities. Labor supply and demand would be roughly balanced; however,there would be increasing structural contradictions of the labor market.Based on the analysis of labor supply and demand,we provide an estimation of the unemployment scale of the 40's and 50's generations,migrant workers and college graduates,and discuss policy suggestions on promoting employment of college graduates.

Elastic wave scattering from rough free surfaces of solids

Elastic wave scattering by a rough free surface of solids is analyzed. The analysis is based on the concept of scattering amplitude (SA) and perturbation approximation. The SA method is very convenient for rough surface scattering problems. By solving the boundary equations, the first and the second order solutions of approximate scattering amplitude are obtained. The general solutions are used for, as an example, the wave scattering by rough surfaces with Gaussian distribution. The mean field and variance are given. Finally, an experiment is designed to verify the theoretical predications.

Propagation of elastic waves in a plate with rough surfaces

The characteristics of Lamb wave propagating in a solid plate with rough surfaces are studied on the basis of small perturbation approximation. The Rayleigh-Lamb frequency equation expressed with SA matrix is presented. The Rayleigh-Lamb frequency equation for a rough surface plate is different from that for a smooth surface plate, resulting in a small perturbation △k on Lamb wave vector k. The imaginary part of △k gives the attenuation caused by wave scattering. An experiment is designed to test our theoretical predications. By using wedge-shape pipes, different Lamb wave modes are excited. The signals at different positions are received and analyzed to get the dispersion curves and attenuations of different modes. The experimental results are compared with the theoretical predications.