Based on the simplification of cutting process,a series of numerical simulations were conducted using a 2-D discrete element method to explore the effects of embedded cracks with different dip angles on the rock fragm...Based on the simplification of cutting process,a series of numerical simulations were conducted using a 2-D discrete element method to explore the effects of embedded cracks with different dip angles on the rock fragmentation process,cutting characteristics and breaking efficiency.The results show that the simulated results are in a good agreement with previous theoretical study.The main crack propagates to the top tip of embedded crack,except when the dip angle is 90°.Side cracks which are more fully developed in the rocks containing embedded cracks tend to propagate towards the free surface.According to the history of vertical cutting force,it is shown that the peak force is decreased by embedded cracks.The study on cutting efficiency was conducted by combining the quantity of crack and cutting energy.And the results show that breaking efficiency can be treated as a decreasing or a increasing function when the dip angle is less or larger than 30°,respectively.Breaking efficiency is higher than that in intact rock when the dip angle is larger than 45°.展开更多
The expanding scale and increasing rate of marine biological invasions have been documented since the early 20th century. Besides their global ecological and economic impacts, non-indigenous species （NIS） also have ...The expanding scale and increasing rate of marine biological invasions have been documented since the early 20th century. Besides their global ecological and economic impacts, non-indigenous species （NIS） also have attracted much attention as opportunities to explore important eco-evolutionary processes such as rapid adaptation, long-distance dispersal and range expansion, and secondary contacts between divergent evolutionary lineages. In this context, genetic tools have been extensively used in the past 20 years. Three important issues appear to have emerged from such studies. First, the study of NIS has revealed unexpected cryptic diversity in what had previously been assumed homogeneous entities. Second, there has been surprisingly little evidence of strong founder events accompanying marine introductions, a pattern possibly driven by large propagule loads. Third, the evolutionary processes leading to successful invasion have been difficult to ascertain due to faint genetic signals. Here we explore the potential of novel tools associated with high-throughput sequencing （HTS） to address these still pressing issues. Dramatic increase in the number of loci accessible via HTS has the potential to radically increase the power of analyses aimed at species delineation, exploring the population genomic consequences of range expansions, and examining evolutionary processes such as admixture, introgression, and adaptation. Nevertheless, the value of this new wealth of genomic data will ultimately depend on the ability to couple it with expanded ＂traditional＂ efforts, including exhaustive sampling of marine populations over large geographic scales, integrated taxonomic analyses, and population level exploration of quantitative trait differentiation through common-garden and other laboratory experiments.展开更多
基金Project(2013CB035401)supported by the National Basic Research Program of ChinaProject(51174228)supported by the National Natural Science Foundation of ChinaProject(71380100003)supported by Hunan Provincial Innovation Foundation for Postgraduate,China
文摘Based on the simplification of cutting process,a series of numerical simulations were conducted using a 2-D discrete element method to explore the effects of embedded cracks with different dip angles on the rock fragmentation process,cutting characteristics and breaking efficiency.The results show that the simulated results are in a good agreement with previous theoretical study.The main crack propagates to the top tip of embedded crack,except when the dip angle is 90°.Side cracks which are more fully developed in the rocks containing embedded cracks tend to propagate towards the free surface.According to the history of vertical cutting force,it is shown that the peak force is decreased by embedded cracks.The study on cutting efficiency was conducted by combining the quantity of crack and cutting energy.And the results show that breaking efficiency can be treated as a decreasing or a increasing function when the dip angle is less or larger than 30°,respectively.Breaking efficiency is higher than that in intact rock when the dip angle is larger than 45°.
文摘The expanding scale and increasing rate of marine biological invasions have been documented since the early 20th century. Besides their global ecological and economic impacts, non-indigenous species （NIS） also have attracted much attention as opportunities to explore important eco-evolutionary processes such as rapid adaptation, long-distance dispersal and range expansion, and secondary contacts between divergent evolutionary lineages. In this context, genetic tools have been extensively used in the past 20 years. Three important issues appear to have emerged from such studies. First, the study of NIS has revealed unexpected cryptic diversity in what had previously been assumed homogeneous entities. Second, there has been surprisingly little evidence of strong founder events accompanying marine introductions, a pattern possibly driven by large propagule loads. Third, the evolutionary processes leading to successful invasion have been difficult to ascertain due to faint genetic signals. Here we explore the potential of novel tools associated with high-throughput sequencing （HTS） to address these still pressing issues. Dramatic increase in the number of loci accessible via HTS has the potential to radically increase the power of analyses aimed at species delineation, exploring the population genomic consequences of range expansions, and examining evolutionary processes such as admixture, introgression, and adaptation. Nevertheless, the value of this new wealth of genomic data will ultimately depend on the ability to couple it with expanded ＂traditional＂ efforts, including exhaustive sampling of marine populations over large geographic scales, integrated taxonomic analyses, and population level exploration of quantitative trait differentiation through common-garden and other laboratory experiments.
