Effect of Geometrical Structure on Transport Properties of Silicene Nanoconstrictions

We study electrical modulation of transport properties of silicene nanoconstrictions with different geometrical structures.We investigate the effects of the position and width of the central scattering region on the conductance with increasing Fermi energy.It is found that the conductance significantly depends on the position and the width of the nanoconstriction.Interestingly,the symmetrical structure of the central constriction region can induce a resonance effect and significantly increase the system’s conductance.We also propose a novel two-channel structure with an excellent performance on the conductance compared to the one-channel structure with the same total width.Such geometrically-induced conductance modulation of silicene nanostructures can be achieved in practice via current nanofabrication technology.

纯种及杂交中国黄牛的生产性能及胴体特征

在中国河北及山东省的屠宰场对 334头中国黄牛以及中国黄牛与西门塔尔或利木赞牛的杂交后代的胴体特征进行了调查。全部被调查牛群的平均屠宰年龄为 4 .8± 2 .2年 ,平均体重 5 2 7.2 8± 77.10 kg。黄牛和杂交牛的平均年龄分别为 :5 .2 9± 2 .0 3和 2 .85± 1.71年 ,平均活重分别为5 19.4 3± 78.7kg和 5 6 3.13± 5 6 .8kg。胴体重、皮下脂肪厚度及屠宰率的变异很大。全部 334头牛的平均胴体重、皮下脂肪厚度、屠宰率及眼肌面积分别为 2 83.9± 6 4 .1kg、14 .0± 8.0 m m、5 4 .0 %± 4 .0 %和 6 2 .7± 13.3cm2。与纯种黄牛相比 ,杂交牛的屠宰年龄提前、活体重、胴体重及屠宰率提高、眼肌面积增大。结果表明 :在中国 ,杂交育种能明显的改善黄牛的肉用生产性能 ,但需要对饲养体系加以改进并建立适当的牛肉分级体系 ,以促进牛肉生产 ,提高牛肉品质。