DPTM simulation of aeolian sand ripple

Aeolian sand ripple and its time evolution are simulated by the discrete particle tracing method (DPTM) presented in this paper. The difference between this method and the current methods is that the former can consider the three main factors relevant to the formation of natural aeolian sand ripples, which are the wind-blown sand flux above the sand bed formed by lots of sand particles with different diameters, the particle-bed collision and after it the rebound and ejection of sand particles in the sand bed, the saltation of high-speed sand particles and the creep of low-speed sand particles, respectively. The simulated aeolian sand ripple is close to the natural sand ripple not only in basic shape and characteristic, particle size segregation and stratigraphy, but also in formation stages. In addition, three important speeds can be obtained by this method, which are the propagation speed of the saturated aeolian sand ripple and the critical frictional wind speeds of emergence and disappearance of sand ripple. Supported by the Key Project of the National Natural Science Foundation of China (Grant No. 10532040)     

Experimental investigation on trap stagnant effect and sand flux in aeolian sand transport

A new isokinetic vertical sand trap is designed in this work, and the new trap has an advantage that airflows in all sampling tubes at different height can simultaneously approach the isokinetic state. The stagnant effect and vertical sand mass flux are experimentally investigated in a wind tunnel. Compared with the traditional passive sand trap, the new design greatly reduces the stagnant effect, and has higher efficiency at different heights and wind speeds. The results obtained in this Letter also show the stagnant effect of the sand trap not only changes the total efficiency of the sand collection, but also the distribution of the vertical sand flux. The new isokinetic sand trap has good performance and can be applied to study the sand flux in aeolian sand transport.     

不同模态沙尘暴对太赫兹波的衰减分析

太赫兹波空间传输特性研究对于太赫兹波在空间中的应用具有重要意义.为研究太赫兹波在沙尘暴天气中的传输特性,本文根据沙尘粒子尺度的对数正态分布,应用Mie散射理论和Monte Carlo方法,分析了国内不同地域的六种干沙模态沙尘暴对1—10 THz频段太赫兹波的衰减特性,给出了消光参量和衰减率与频率的关系.结果表明,随着频率的增大,1—10 THz频段太赫兹波的衰减率呈先增加后减小的趋势,沙尘暴的模态不同,太赫兹波衰减较强的频段范围有所不同.为了分析沙粒含水量对太赫兹波传输衰减的影响,计算了不同尺寸的沙尘粒子3个效率因子与含水量的关系,发现粒子尺寸不同,含水量对消光的影响也不同;应用Monte Carlo方法计算了两种湿沙模态的沙尘暴对1—10 THz频段太赫兹波的衰减,给出了衰减率与含水量及频率的关系.结果表明,随沙粒含水量增大,沙尘暴对太赫兹波衰减较强的频段向低频方向移动,含水量小于5%时,太赫兹波衰减率随含水量增大显著增强,湿度较大的沙尘暴天气对太赫兹波的传输衰减影响更大.     

Lasso算法的油砂钠元素近红外建模

以油砂中钠元素为研究对象,首次应用近红外光谱,结合Lasso(least absolute shrinkage and selection operator)建模方法,建立了油砂金属钠含量的近红外光谱定量校正模型,并与传统的PLS建模方法进行比较。结果表明,两种方法建立的油砂金属钠含量校正模型都具有很高的精度,预测性能方面略有差异。在实验验证集与预测集中,PLS与Lasso算法的相关系数分别是：R_v=0.878 8,R_p=0.857 9和R_v=0.887 4,R_p=0.860 0。实验验证了使用近红外光谱快速测定油砂金属钠含量的有效性,并分析了PLS与Lasso算法的适用范围。     

扎赉特旗油砂在氮气气氛下的热解制油研究

油砂是一种含有沥青或其他重质石油的沉积岩,主要用于提取油砂沥青,以生产合成原油。中国拥有相当数量的油砂资源,目前还未开采,仅处于初步研究阶段。加拿大在20世纪初期就展开了油砂的开采及制油研究工作,并于20世纪70年代由加拿大合成油公司实现了工业化生产。油砂生产的沥青和合成油已占其石油总产量的1／4以上。     

Relationship between swelling and mechanical properties of cross-linked polymers mixed with sand

Cross-linked polymers consisting of acrylamide, sodium acrylate, starch fragments and a cross-linker were synthesized with the same content of carboxyl groups and three degrees of cross-linking Q of 0.04, 0.2 and 1 wt%. An increase in Q gradually reduces the swelling of polymer gels in water; when distributed in sand, polymer gels exhibit maximum swelling at Q = 0.2 wt%. It is shown that the behavior of polymer gels in sand is determined by the balance between the elasticity of swollen polymer gels and the resistance of sand particles