Search

In order to study the optimal design parameters of the heat pipe system in the heat pipe snow-melting road structure, a finite element analytical model of the snow-melting road is established based on the heat transfer theory. And based on the analysis of internal heat transfer and surface convective heat transfer of the road, the author set suitable boundary conditions of temperature field according to the actual situation of the road pavement and made quantitative research on the influence of factors such as the evaporating section burial depth and arrangement distance of the heat pipe on the pavement temperature field. The results show that the optimal arrangement distance of the heat pipes is 300-500mm, and when the heat pipe distance is 500mm, the temperatures of the road surface increased slowly, the isotherm of 0°C will no longer continue, and the snow-melting time would become longer; heat pipe burial depth should be determined according to the road structure, the shallower the burial depth the better the snow-melting effect..

In order to study the influence of various factors on the construction safety of shallow buried tunnels, a multifactor evaluation model consisting of 9 indicators, such as tunnel size, the buried depth, surrounding rock condition and construction management, is established from the perspective of “4M1E” by combining the characteristics of shallow buried tunnel construction by borehole-blasting method. It combines the advantages of subjective weighting method AHP and objective weighting method CRITIC, and determines the comprehensive weight values through the combined weighting method, which is used to improve the weight assignment of multi-dimensional normal cloud model, and evaluates the stability of the surrounding rock at the entrance and exit of the shallow buried tunnel based on the concepts of expectation, entropy and super entropy of the cloud model. And then it accurately obtains the construction safety of the entrance and exit of the shallow buried tunnel, and the evaluation results have scientific guidance for the control of construction risks.

Highly c-axis-oriented ZnO films were deposited successfully on the nucleation sides of free-standing diamond (FD) films by the direct current (DC) magnetron sputtering method. The effect of the sputtering parameters, such as power, gas pressure and sputtering plasma composition of Ar-to-O2, on the properties of ZnO thin films was investigated in detail. X-ray diffraction (XRD) measurements showed that, at a sputtering power of 200 W, gas pressure of 0.5 Pa and an Ar-to-O2 composition of 1:1, a higher intensity of the (002) diffraction peak and a narrower full width at half maximum (FWHM) were detected which meant high c-axis orientation and high quality of the ZnO films. To improve the quality of the ZnO film, a thin ZnO layer was pre-grown as a homo-buffer layer. XRD measurements showed that this buffer layer had a beneficial effect on the structural and morphological properties of the post-grown ZnO film.

P-type undoped freestanding diamond (FSD) films were grown by the microwave plasma chemical vapor deposition (MPCVD) method. The effects of the hydrogen plasma treatment and annealing process on the p-type behavior of FSD films were investigated by the Hall effect method. The results revealed that the sheet carrier concentration increased and the sheet resistivity decreased with the treating time and a stable value was achieved after a period of time. Up to an annealing temperature of 250°C, the sheet resistivity and sheet carrier concentration remained in a relatively stable range but changed dramatically after annealing at 300°C. A heterojunction was also fabricated by the growth of an n-type ZnO film on the p-type FSD film. Current-voltage (I-V) characterization of the heterojunction at room temperature indicated that this structure was rectifying in nature with a turn-on voltage of about 0.6 V.

A numerical approach of the finite element method is extended to study the scattering properties of an arbitrary dielectric target above the dielectric rough surface. For scattering in an open region, the artificial boundaries should be introduced to truncate the infinite computational domain. A perfectly matched layer (PML), as the artificial boundary of the finite-element-method (FEM) region, is employed to absorb the outward wave scattered from the model. The strategies of hybrid FEM/PML are presented with their validity evaluated by finite element/boundary integral method (FE/BIM), and then the scattering properties of the dielectric composite problem with different material permittivity are discussed in detail. Compared with the published works about FEM/PML, we extend the FEM/PML into the simulations of a dielectric target above the dielectric rough surface.