The disc cutters of tunnel boring machine(TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established...The disc cutters of tunnel boring machine(TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established to study the rock fragmentation law between adjacent disc cutters with different polar angles based on particle flow code(PFC). The influence of polar angle of adjacent disc cutters on rock cracks and stresses under different cutter spacing and penetration was studied. Research shows that polar angle difference leads to the discontinuity of rock-fragmentation process by adjacent cutters. The effect of rock-fragmentation is influenced by the cutting depth difference between adjacent cutters. The effect of rock-fragmentation performed best, meanwhile large rock blocks were flaked when the difference of cutting depth is half of the penetration. Too large or small difference of the cutting depth will cause high specific energy consumption of rock fragmentation. The specific energy consumption is relatively small when the difference of cutting depth is half of the penetration.展开更多
The purpose of the present study was to examine the genetic variation in Salamandra infraimmaculata from different breeding site habitats using the Amplified Fragment Length Polymorphism (AFLP) method. The results of ...The purpose of the present study was to examine the genetic variation in Salamandra infraimmaculata from different breeding site habitats using the Amplified Fragment Length Polymorphism (AFLP) method. The results of the dendogram from a hierarchical cluster analysis show that the grouping of S. infraimmaculata as cluster 5 differs from all the other clusters, including the St1 (Tel-Dan stream) population, which was the most predictable. Five Haplogroups (Hg) were characterized. The mean number of alleles per locus in each population (Ne) ranged from 10.566 (Sp1) to 2.720 (Po6). An average estimated heterozygosity (He) by population ranged from 0.100 (Po6) to 0.186 (St1). Population St1, a permanent breeding site where water was available all year round, exhibited the highest level of polymorphism, while population Po6, from the ephemeral breeding site, exhibited the lowest level of polymorphism. Gene flow between clusters showed that clusters 3 and 4 are sources of migrants and also receive gene flow, while clusters 1 and 2 may be a source of migrants but may not receive much gene flow. A phylogenetic analysis, based on clustering using Nei’s genetic distance, demonstrated that the Tel-Dan population is located on a separate branch within its sub-population. The conclusion of the present study shows that the genetic divergence among isolated populations is not correlated to distance but is affected by the variation of habitats.展开更多
基金Project(2012AA041801)supported by the Hi-tech Research and Development Program of ChinaProject(2013CB035401)supported by the National Basic Research Program of ChinaProject(51475478)supported by the National Natural Science Foundation of China
文摘The disc cutters of tunnel boring machine(TBM) are installed with different polar angles. This causes the cutting depth difference between adjacent disc cutters on the tunnel face. A rock-cutting model was established to study the rock fragmentation law between adjacent disc cutters with different polar angles based on particle flow code(PFC). The influence of polar angle of adjacent disc cutters on rock cracks and stresses under different cutter spacing and penetration was studied. Research shows that polar angle difference leads to the discontinuity of rock-fragmentation process by adjacent cutters. The effect of rock-fragmentation is influenced by the cutting depth difference between adjacent cutters. The effect of rock-fragmentation performed best, meanwhile large rock blocks were flaked when the difference of cutting depth is half of the penetration. Too large or small difference of the cutting depth will cause high specific energy consumption of rock fragmentation. The specific energy consumption is relatively small when the difference of cutting depth is half of the penetration.
文摘The purpose of the present study was to examine the genetic variation in Salamandra infraimmaculata from different breeding site habitats using the Amplified Fragment Length Polymorphism (AFLP) method. The results of the dendogram from a hierarchical cluster analysis show that the grouping of S. infraimmaculata as cluster 5 differs from all the other clusters, including the St1 (Tel-Dan stream) population, which was the most predictable. Five Haplogroups (Hg) were characterized. The mean number of alleles per locus in each population (Ne) ranged from 10.566 (Sp1) to 2.720 (Po6). An average estimated heterozygosity (He) by population ranged from 0.100 (Po6) to 0.186 (St1). Population St1, a permanent breeding site where water was available all year round, exhibited the highest level of polymorphism, while population Po6, from the ephemeral breeding site, exhibited the lowest level of polymorphism. Gene flow between clusters showed that clusters 3 and 4 are sources of migrants and also receive gene flow, while clusters 1 and 2 may be a source of migrants but may not receive much gene flow. A phylogenetic analysis, based on clustering using Nei’s genetic distance, demonstrated that the Tel-Dan population is located on a separate branch within its sub-population. The conclusion of the present study shows that the genetic divergence among isolated populations is not correlated to distance but is affected by the variation of habitats.
