Applied Mechanics and Materials Vols. 84-85

Abstract: Based on applications in different open-pit mine and analysis of economic benefits, the paper describes the mixed emulsion explosive productive technology and the mechanism of air-space blasting, which has great value in reducing the production costs and bringing huge blasting economic benefits.

Abstract: Montmorillonite (MMT) modified asphalts are prepared by melt blending with the help of high-speed shear mixer. The dispersion of MMT layers in the asphalt matrix are characterized by X-ray diffraction (XRD). The effect of different contents of MMT on physical properties of the base asphalt is studied. These properties include penetration, softening point and ductility. The results indicate that MMT/asphalt may form a nanocomposite structure with MMT layers intercalated by the asphalt molecules. MMT can improve the high temperature performance and temperature sensitivity of the base asphalt. And it can slightly reduce the low temperature performances of matrix asphalt. It is found that low temperature performances, high temperature performance and temperature sensitivity of the modified system achieved balance when the content of MMT is 4 wt%.

Abstract: In this paper, we report on the structure, magnetic properties and magnetocaloric effect in NaZn₁₃-type LaFe_11.1Co_0.8Si_1.1B_x alloys close to room temperature. The stable NaZn₁₃ cubic structure phase (space group is Fm-3c) can easily obtained by annealing at 1080 °C for 225 hours. The maximal values of magnetic entropy change for LaFe_11.1Co_0.8Si_1.1B_x (x=0.2, 0.25) were found to be 5.3 and 5.9 J/kg K at Curie temperature for a magnetic field change in 0-1.5 T, respectively. The calculated refrigerant capacity for a field change in 0–1.5 T is about 147 and 107 J/kg K, for LaFe_11.1Co_0.8Si_1.1B_0.2 and LaFe_11.1Co_0.8Si_1.1B_0.25 respectively, which is as larger as those of Gd(99.3%) alloy

Abstract: Polycrystalline Ca_3-xMg_xCo₄O₉(x=0-0.3)ceramics were prepared by the sol–gel method combined with the ordinary pressing sintering and the thermoelectric properties were measured from room temperature to 673 K. The substitution of Mg²⁺ for Ca²⁺ had a greater impact on the thermoelectric properties of Ca₃Co₄O₉. The electrical conductivity and the thermal conductivity reduced significantly with increasing Mg content, and the Seebeck coefficient increased simultaneously. The influence of Mg doping on the thermal conductivity is mainly embodied in the lattice thermal conductivity of Ca₃Co₄O₉. The lattice thermal conductivity showed a significant change with the increase of the dopant content, while the carrier thermal conductivity had no obvious change with the doping increasing. These results indicated that the thermoelectric properties of the material could be optimized remarkably with the substitution of Mg. The figure of merit Z reached 1.08×10^-4 K^-1 at 573 K for the sample of Ca_2.8Mg_0.2Co₄O₉.

Abstract: The irreversible demagnetization of Nd-Fe-B permanent magnet (PM) material appears during the use of Nd-Fe-B permanent magnet synchronous motor (PMSM) has been blocking this kind of motor towards the direction of large-scale. Demagnetization of PM is mainly affected by the working temperature and the reverse magnetic field of stator armature, and the accurate calculation for the demagnetization characteristics of PMSM is usually difficult by using the analytical method. In this paper, we derive the calculation formula of the knee point under a working temperature for permanent magnets in PMSM firstly, then calculate and analyze the demagnetization characteristics of PMSM under different working temperatures and loads by using the Finite Element Method (FEM), Thereby more accurately reflect the working characteristics of PM and the overload capability of motor. This paper provides theoretical basis for the selection of PM materials and the calculation of PM thickness in the PMSM design.

Abstract: In recent years, much research has been devoted to the Bitumen research; however, few have deployed the study of the research trend. In fact, grasping the research trend is imperative for enterprises and researchers. The study aims at analyzing the trend change of Bitumen research from 2000 to 2010. The contribution of the study includes the following two points. First, the study has found the shift of the Bitumen research from “distribution” and “sand” related issues to the focuses of “surface” and “polymer”. Second, the study finds a new way of literature survey by using the text mining method in order to explore the trend change.

Abstract: In the condition that conventional energy sources are depleted and greatly pollute environment, solar energy as a new energy type, has some advantages which conventional energy sources are not compared with, it has received more and more applications. In this paper, SCM is the control center of the system, the solar energy is convert into electricity stored in battery, and then battery powers to the water pump to ensure the normal operation of the water pump.

Abstract: Due to the energy crisis and greenhouse effect, wind energy is becoming one of the most attractive renewable energies during last three decades. Especially them offshore wind energy gets more attention because it could provide better wind condition with less turbulence and no visual impact and land limitation. Different foundation types could be used for offshore wind turbine. Jacket foundation is regarded as a suitable solution for the intermediate water depth ranging from 30 to 80 meters. On the submerged members of jacket, numerous type of marine fouling organism may be found. They may increase the diameter of the members, change the surface roughness and influence the hydrodynamic loads of structures. In this paper, the types and distribution of marine growth are presented. Effects of marine growth thickness, density and hydrodynamic coefficients on vibration characteristics of offshore wind turbine are discussed. The natural frequencies of the coupled system are compared.

Abstract: In recent years, vertical axis wind turbine is widely used. However, when it is installed in cold regions icing and snow on blade surface will occur in winter. To simulate the situation of icing, computer simulations were carried out on a NACA0015 airfoil which is often used for vertical axis wind turbine. The computations were based on the N-S equation in 2D incompressible steady flow with using the DPM (Discrete Phase Model) to calculate icing. Under the different wind speeds and cold water discharges in cold air, the icing distributions on airfoil at 8 kinds of typical attack angles were calculated. The icing area on the leading edge and trailing edge of blade airfoil were also obtained. Based on these results, the factors affecting the icing on blade surface including wind speed, attack angle and cold water flow discharge were discussed. With the increasing of the flow discharge, the icing area ratio increases and ice accretions become more and more dense.

Abstract: Recently, the straight-bladed vertical axis wind turbine (SB-VAWT) receives more and more attentions for its simple design, low cost, and good maintenance. The torque performance of the SB-VAWT is greatly affected by the blade airfoil. In order to research the static torque characteristics of SB-VAWT with symmetrical and non-symmetrical blade airfoil, numerical simulations by 2D CFD method were carried out on three kinds of blade airfoils including NACA0018, NACA2418 and NACA4418 at different azimuth angles. Furthermore, the static torque coefficient of the SB-VAWT with four blades with the three kinds of blade airfoils was calculated. The pressure and velocity fields were also obtained to analyze the static torque performance. Based on these results, the effects of blade airfoils on the starting torque performance of the SB-VAWT were compared and discussed.