CFD-DEM simulation of three-dimensional aeolian sand movement

A three-dimensional CFD-DEM model is proposed to investigate the aeolian sand movement. The results show that the mean particle horizontal velocity can be expressed by a power function of heights. The probability distribution of the impact and lift-off velocities of particles can be described by a log-normal function, and that of the impact and lift-off angles can be expressed by an exponential function. The probability distribution of particle horizontal velocity at different heights can be described as a lognormal function, while the probability distribution of longitudinal and vertical velocity can be described as a normal function. The comparison with previous two-dimensional calculations shows that the variations of mean particle horizontal velocity along the heights in two-dimensional and three-dimensional models are similar. However, the mean particle density of the two-dimensional model is larger than that in reality, which will result in the overestimation of sand transportation rate in the two-dimensional calculation. The study also shows that the predicted probability distributions of particle velocities are in good agreement with the experimental results.

Carbon isotopic composition of modern soil and paleosol as a response to vegetation change on the Chinese Loess Plateau

IEECAS SKLLQG

Experiments and modification on electron cyclotron resonance ion sources at the Institute of Modern Physics

Uranium ion beams were produced from electron cyclotron resonance (ECR) ion sources by sputtering method this year at the Institute of Modern Physics. At first, we chose the Lanzhou ECR No. 3 ion source to implement the production experiment of U ion beams. Finally, 11 e mu A of U28+, 5 e mu A of U32+, and 1.5 e mu A of U35+ were obtained. A U26+ ion beam produced by the LECR2 ion source was accelerated successfully by the cyclotron. This means that the Heavy Ion Research Facility in Lanzhou (HIRFL) has accomplished the acceleration of the ion beam of the heaviest element according to the designed parameters. The Lanzhou ECR ion source No. 2 (LECR2), which was built in 1997, has served the HIRFL for eight years and needed to be upgraded to provide more intense high charge state ion beams for HIRFL cooling storage ring. We started the upgrading project of LECR2 last year, and the modified design just has been finished. (c) 2006 American Institute of Physics.

"Dual-Parallel-Channel" Shape-Gradient Surfaces: Toward Oriented and Reversible Movement of Water Droplets

In this paper, we prepared "dual-parallel-channel" shape-gradient surfaces, on which water droplets can reversibly and orientedly move between two adjacent pools under the guidance of an external voltage. Furthermore, it is found that the motion speed is governed by several parameters, including bath condition, gradient angle, and the working voltage. In this self-transportation process of water droplets, the external voltage works like a traffic light, which can give "moving", "stopping", "turning" and "straight-going" signals to the Water droplets.