A direct numerical simulation(DNS) method is used to calculate the partitioned convection system with Ra number ranging from 10^7 to 2×10^9.Using the boundary layer thickness to normalize the height of gaps d, we...A direct numerical simulation(DNS) method is used to calculate the partitioned convection system with Ra number ranging from 10^7 to 2×10^9.Using the boundary layer thickness to normalize the height of gaps d, we find a strong consistency between the variation of the TD number(the average value of the temperature in each heat transfer channel is averaged after taking the absolute values) with the change of the height of gaps and the variation of the TD number with the change of Ra number in partitioned convection.For a given thickness of partition, heights of gaps are approximately equal to 0.5 or 1 time of the thermal boundary layer thickness λθ at different Ra numbers.TD number representing temperature characteristics is almost the constant value, which means that TD number is a function of d/λθ only.Analysis of local temperature field of area in gaps shows that the temperature distribution in the gaps are basically the same when d/λθ is certain.The heat transfer Nu number of the system at d/λθ≈ 0.5 is larger than that of d/λθ≈ 1, both of them have the same scaling law with Ra number and Nu^Ra^0.25.展开更多
We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. W...We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height（SBH） occurs following the insertion of the graphene layer between Co_2MnSi and Ge. The electron SBH is modulated in the 0.34 eV–0.61 eV range. Furthermore,the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility.展开更多
为了提升采煤机运行安全性与稳定性,以MG300-700-AWD型采煤机为研究对象,通过有限元法对采煤机平滑靴与中部槽接触碰撞特性进行了研究。研究发现,中部槽安装间隙量与高度差是影响平滑靴接触碰撞特性的重要因素,随着安装间隙量与高度差...为了提升采煤机运行安全性与稳定性,以MG300-700-AWD型采煤机为研究对象,通过有限元法对采煤机平滑靴与中部槽接触碰撞特性进行了研究。研究发现,中部槽安装间隙量与高度差是影响平滑靴接触碰撞特性的重要因素,随着安装间隙量与高度差的提高,平滑靴碰撞特性应力升高,当安装间隙量超过30 mm,平滑靴产生的接触力会超过ZG25CrMn Ni Mo许用应力的222.67 MPa,增加平滑靴碰撞损伤的危险。采煤机运行过程中应注重安装间隙量与高度差的控制,通过实践应用验证了模拟分析结果的合理性,将安装间隙量与高度差控制在较低水平范围内,可保证整个采煤机稳定运行,有利于煤矿开采工作更好地开展。展开更多
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11772362 and 11452002)the Special Scientific Research Fund for Super Computing in the Joint Fund of the National Natural Science Foundation of China and the People’s Government of Guangdong Province,China(Phase Ⅱ,nsfc2015_570)
文摘A direct numerical simulation(DNS) method is used to calculate the partitioned convection system with Ra number ranging from 10^7 to 2×10^9.Using the boundary layer thickness to normalize the height of gaps d, we find a strong consistency between the variation of the TD number(the average value of the temperature in each heat transfer channel is averaged after taking the absolute values) with the change of the height of gaps and the variation of the TD number with the change of Ra number in partitioned convection.For a given thickness of partition, heights of gaps are approximately equal to 0.5 or 1 time of the thermal boundary layer thickness λθ at different Ra numbers.TD number representing temperature characteristics is almost the constant value, which means that TD number is a function of d/λθ only.Analysis of local temperature field of area in gaps shows that the temperature distribution in the gaps are basically the same when d/λθ is certain.The heat transfer Nu number of the system at d/λθ≈ 0.5 is larger than that of d/λθ≈ 1, both of them have the same scaling law with Ra number and Nu^Ra^0.25.
基金Project supported by the National Natural Science Foundation of China(Grant No.61504107)the Fundamental Research Funds for the Central Universities,China(Grant Nos.3102014JCQ01059 and 3102015ZY043)
文摘We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co_2MnSi and the germanium（Ge） channel modulates the Schottky barrier height and the resistance–area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height（SBH） occurs following the insertion of the graphene layer between Co_2MnSi and Ge. The electron SBH is modulated in the 0.34 eV–0.61 eV range. Furthermore,the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility.
文摘为了提升采煤机运行安全性与稳定性,以MG300-700-AWD型采煤机为研究对象,通过有限元法对采煤机平滑靴与中部槽接触碰撞特性进行了研究。研究发现,中部槽安装间隙量与高度差是影响平滑靴接触碰撞特性的重要因素,随着安装间隙量与高度差的提高,平滑靴碰撞特性应力升高,当安装间隙量超过30 mm,平滑靴产生的接触力会超过ZG25CrMn Ni Mo许用应力的222.67 MPa,增加平滑靴碰撞损伤的危险。采煤机运行过程中应注重安装间隙量与高度差的控制,通过实践应用验证了模拟分析结果的合理性,将安装间隙量与高度差控制在较低水平范围内,可保证整个采煤机稳定运行,有利于煤矿开采工作更好地开展。
