The horizontal convection in a square enclosure driven by a linear temperature profile along the bottom boundary is investigated numerically by using a finite difference method. The Prandtl number is fixed at 4.38, and the Rayleigh number Ra ranges from 107 to 1011. The convective flow is steady at a relatively low Rayleigh number, and no thermal plume is observed, whereas it transits to be unsteady when the Rayleigh number increases beyond the critical value. The scaling law for the Nusselt number Nu changes from Rossby’s scaling Nu ∼ Ra1/5 in a steady regime to Nu ∼ Ra1/4 in an unsteady regime, which agrees well with the theoretically predicted results. Accordingly, the Reynolds number Re scaling varies from Re ∼ Ra3/11 to Re ∼ Ra2/5. The investigation on the mean flows shows that the thermal and kinetic boundary layer thickness and the mean temperature in the bulk zone decrease with the increasing Ra. The intensity of fluctuating velocity increases with the increasing Ra.

An indentation simulation of the crystal Ni is carried out by a molecular dynamics technique (MD) to study the mechanical behavior at nanometer scales. Indenter tips with both sphere shape and conical shape with 60 ∘ cone angle are used, and simulation samples with different crystal orientations are adopted. Some defects such as dislocations and point defects are observed. It is found that nucleated defects (dislocations, amorphous atoms) are from the local region near the pin tip or the sample surface. The temperature distribution of the local region is analyzed and it can explain our MD simulation results.

The p-type N doped ZnO thin films are fabricated using radio-frequency magnetron sputtering technique in O-rich growth condition together with the direct N+ ion-implantation and annealing. The conductivities and Raman scattering properties of the samples are studied by Hall measurements and Raman spectra respectively. Hall measurements indicate that the optimal p-type ZnO film can be obtained when the sample is annealed at 600 ℃ for 120 min in N2 ambience, and its hole concentration is about 2.527×1017 cm-3. N+-implantation induces three additional vibrational modes in ZnO, which are located at 274.2, 506.7 and 640.4 cm-1 respectively. In the process of the annealing, by comparing the electrical properties and Raman speetra of the samples, we find that the competition between intrinsic donor defects and the activation of N acceptors plays a crucial role in the p-type formation of ZnO:N films during annealing.

The indentation simulation of the nanocrystalline Ni is carried out by molecular dynamics technique (MD) to study the mechanical behavior at nanometer scales. The sphere indenter is used, and simulation sample with three grains and two grain boundaries is adopted. The strength of nanocrystalline is studied as indenter is set at grain boundary and grain, respectively. Some defects such as dislocations or slipping deformation are observed. It is found that dislocations are emitted from the grain boundary or the sample surface. The temperature distribution of local region around indenter is analyzed and it can explain our MD simulation results.