The deformation behaviour of Au nanowires subjected to uniaxial tension at high strain-rate under different temperatures is studied by molecular dynamics simulation along [001], [011], and [111] elongation directions, respectively. The stress distributions and the radial distribution functions of the structure of the nanowires are evaluated and discussed. It is seen that the stress-strain curves are quite different from those of the bulk material. Moreover, the microstructures of nanowires are transformed first from FCC to face-centred-orthorhombic-like crystalline, and then changed to the amorphous state. The first neighbouring distance in the radial distribution functions along the [001] direction is clearly split into two peaks. It appears that the ductility of the nanowires at high strain-rate is higher than the corresponding macroscopic cases. The magnitudes of Young's modulus and the maximum strength along different crystalline directions are evaluated and compared with each other. They tend to decrease as the temperature increases. It may be predicted from our simulations that the conductance at high strain-rate deformation may be a continuous function of elongation due to the smooth reduction of area.

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A two-dimensional, quasi-static, inverse heat conduction problem (IHCP) is implemented to investigate the absorption efficiency of surface coatings in laser surface hardening process. The analysis of IHCP includes the utilization of the method of direct sensitivity coefficient and the measurement of interior temperatures nearby the laser heating surface. The results shows that the estimation of surface absorptivity generally agrees with that observed by experimental works. It is realized that the different kinds of coating make influences on the surface absorptivity as well as surface temperature significantly. Furthermore, the power density and scanning speed of laser beam to control the quality of surface hardening may be determined based on the informations of heat flow in the workpiece.

The stability and electronic structure of single-walled carbon nanotubes with B/N co-doping are investigated in detail by using the first-principles theory. From eight possible B/N co-doping configurations, it is found that the one with substitutional B and N atoms located at neighboring sites has a smaller formation energy than that with separate B/N atoms. The electronic structure of armchair carbon nanotubes evolves from metallic to semiconducting as a result of B/N co-doping, whereas the energy gaps of the intrinsically semiconducting nanotubes are reduced significantly. In contrast, the small zigzag nanotubes always remain metallic properties due to their large curvature effects except (5, 0) after B/N co-doping. As the atomic concentration of B/N co-doping is increased, the energy gaps of carbon nanotubes oscillate around a constant level, which is much lower than the energy gap of BC(2)N nanotubes. Moreover, the B/N co-doped carbon nanotubes with B- or N-rich impurities exhibit the characteristics of an acceptor or donor, respectively, since their electronic structures are significantly influenced by the occupied states in the valence and conduction bands due to the shifting of the Fermi level.