50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, ...50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion （CTE） of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/（m？K）, and it was slightly increased after annealing while decreased after aging treatment.展开更多
The magnetohydrodynamic （MHD） stagnation point flow of micropolar flu- ids towards a heated shrinking surface is analyzed. The effects of viscous dissipation and internal heat generation/absorption are taken into ac...The magnetohydrodynamic （MHD） stagnation point flow of micropolar flu- ids towards a heated shrinking surface is analyzed. The effects of viscous dissipation and internal heat generation/absorption are taken into account. Two explicit cases, i.e., the prescribed surface temperature （PST） and the prescribed heat flux （PHF）, are discussed. The boundary layer flow and energy equations are solved by employing the homotopy analysis method. The quantities of physical interest are examined through the presenta- tion of plots/tabulated values. It is noticed that the existence of the solutions for high shrinking parameters is associated closely with the applied magnetic field.展开更多
In this study,a mathematical model is formulated to examine the blood flow through a cylindrical stenosed blood vessel.The stenosis disease is caused because of the abnormal narrowing of flow in the body.This narrowin...In this study,a mathematical model is formulated to examine the blood flow through a cylindrical stenosed blood vessel.The stenosis disease is caused because of the abnormal narrowing of flow in the body.This narrowing causes serious health issues like heart attack and may decrease blood flow in the blood vessel.Mathematical modeling helps us analyze such issues.A mathematical model is considered in this study to explore the blood flow in a stenosis artery and is solved numerically with the finite difference method.The artery is an elastic cylindrical tube containing blood defined as a viscoelastic fluid.A complete parametric analysis has been done for the flow velocity to clarify the applicability of the defined problem.Moreover,the flow characteristics such as the impedance,the wall shear stress in the stenotic region,the shear stresses in the throat of the stenosis and at the critical stenosis height are discussed.The obtained results show that the intensity of the stenosis occurs mostly at the highest narrowing areas compared with all other areas of the vessel,which has a direct impact on the wall shear stress.It is also observed that the resistive impedance and wall shear pressure get the maximum values at the critical height of the stenosis.展开更多
Highly repeatable multilevel bipolar resistive switching in Ti/Ce Ox/Pt nonvolatile memory device has been demonstrated. X-ray diffraction studies of Ce O2 films reveal the formation of weak polycrystalline structure....Highly repeatable multilevel bipolar resistive switching in Ti/Ce Ox/Pt nonvolatile memory device has been demonstrated. X-ray diffraction studies of Ce O2 films reveal the formation of weak polycrystalline structure. The observed good memory performance, including stable cycling endurance and long data retention times（〉10^4s） with an acceptable resistance ratio（～10^2）, enables the device for its applications in future non-volatile resistive random access memories（RRAMs）. Based on the unique distribution characteristics of oxygen vacancies in Ce Ox films, the possible mechanism of multilevel resistive switching in Ce Ox RRAM devices has been discussed. The conduction mechanism in low resistance state is found to be Ohmic due to conductive filamentary paths, while that in the high resistance state was identified as Ohmic for low applied voltages and a space-charge-limited conduction dominated by Schottky emission at high applied voltages.展开更多
基金Project (AWJ-M13-15) supported by the Open Fund of State Key Laboratory of Advanced Welding and Joining,Harbin Institute of Technology,China
文摘50%diamond particle （5μm） reinforced 2024 aluminum matrix （diamond/2024 Al） composites were prepared by pressure infiltration method. Diamond particles were distributed uniformly without any particle clustering, and no apparent porosities or significant casting defects were observed in the composites. The diamond-Al interfaces of as-cast and annealed diamond/2024 Al composites were clean, smooth and free from interfacial reaction product. However, a large number of Al2Cu precipitates were found at diamond-Al interface after aging treatment. Moreover, needle-shaped Al2MgCu precipitates in Al matrix were observed after aging treatment. The coefficient of thermal expansion （CTE） of diamond/2024 Al composites was about 8.5×10-6 °C-1 between 20 and 100 °C, which was compatible with that with chip materials. Annealing treatment showed little effect on thermal expansion behavior, and aging treatment could further decrease the CTE of the composites. The thermal conductivity of obtained diamond/2024 Al composites was about 100 W/（m？K）, and it was slightly increased after annealing while decreased after aging treatment.
基金Project supported by the Higher Education Commission (HEC) of Pakistan (No. 106-1396-Ps6-004)
文摘The magnetohydrodynamic （MHD） stagnation point flow of micropolar flu- ids towards a heated shrinking surface is analyzed. The effects of viscous dissipation and internal heat generation/absorption are taken into account. Two explicit cases, i.e., the prescribed surface temperature （PST） and the prescribed heat flux （PHF）, are discussed. The boundary layer flow and energy equations are solved by employing the homotopy analysis method. The quantities of physical interest are examined through the presenta- tion of plots/tabulated values. It is noticed that the existence of the solutions for high shrinking parameters is associated closely with the applied magnetic field.
文摘In this study,a mathematical model is formulated to examine the blood flow through a cylindrical stenosed blood vessel.The stenosis disease is caused because of the abnormal narrowing of flow in the body.This narrowing causes serious health issues like heart attack and may decrease blood flow in the blood vessel.Mathematical modeling helps us analyze such issues.A mathematical model is considered in this study to explore the blood flow in a stenosis artery and is solved numerically with the finite difference method.The artery is an elastic cylindrical tube containing blood defined as a viscoelastic fluid.A complete parametric analysis has been done for the flow velocity to clarify the applicability of the defined problem.Moreover,the flow characteristics such as the impedance,the wall shear stress in the stenotic region,the shear stresses in the throat of the stenosis and at the critical stenosis height are discussed.The obtained results show that the intensity of the stenosis occurs mostly at the highest narrowing areas compared with all other areas of the vessel,which has a direct impact on the wall shear stress.It is also observed that the resistive impedance and wall shear pressure get the maximum values at the critical height of the stenosis.
基金the financial support by Higher Education Commission(HEC),Islamabad Pakistan
文摘Highly repeatable multilevel bipolar resistive switching in Ti/Ce Ox/Pt nonvolatile memory device has been demonstrated. X-ray diffraction studies of Ce O2 films reveal the formation of weak polycrystalline structure. The observed good memory performance, including stable cycling endurance and long data retention times（〉10^4s） with an acceptable resistance ratio（～10^2）, enables the device for its applications in future non-volatile resistive random access memories（RRAMs）. Based on the unique distribution characteristics of oxygen vacancies in Ce Ox films, the possible mechanism of multilevel resistive switching in Ce Ox RRAM devices has been discussed. The conduction mechanism in low resistance state is found to be Ohmic due to conductive filamentary paths, while that in the high resistance state was identified as Ohmic for low applied voltages and a space-charge-limited conduction dominated by Schottky emission at high applied voltages.
