Advanced Materials Research Vols. 268-270

Abstract: In this paper, a density functional theory based on the first-principles was employed to evaluate the adsorption of CH₄ onto the surfaces of BaZrO₃ catalysts. The absorption mechanism was derived by population and electronic states analysis on the basis of the electronic and surface structure calculations for BaZrO₃. The (001) surface was calculated to be the adsorption surface for CH₄ owing to its high stability. Comparing to that for CH₄ absorbed on (001) surfaces, the frontier energy state was found to the key factor in controlling the adsorption behavior, which is mainly contributed by oxygen and Zr ions of the B-site. The most favorite adsorption site for CH₄ was located at B-sites of BaZrO₃, where the A-site ions would adjust the charge of B-site ions and moreover affect the CH₄ adsorption. The results reported in this work may provide the fundamental understanding about the absorption of CH₄ inflammation catalysts with high-activity and high-stability.

Abstract: A 3-D numerical study has been carried out to uncover the influence of cavity aspect ratio on natural convection heat loss of a solar receiver for high-temperature dish system, accounting for air property variation with temperature. Temperature and velocity contours as well as the variation of the natural convection heat loss with the cavity aspect ratio have been well presented and discussed. It is revealed that the expansion of convection zone together with the augmentation of velocity magnitude result in the increment of natural convection heat loss with decreasing aspect ratio, i.e., with shallower cavity, especially when the cavity aspect ratio larger than 1. Therefore, the solar receiver with much too shallow cavity should be avoided in design.

Abstract: An axial symmetric 2-D invariable temperature phase change interface model of capillary porous wick evaporator with bayonet tube for alkali metal thermal-to-electric converter (AMTEC) was established to simulate flow and heat transfer characteristics in capillary porous wick and liquid channel by solving the mass and heat transport controlling equations. The effects of length, radius and thermal resistance of the bayonet tube on the distributions of pressure, velocity and temperature in capillary porous wick and liquid channel were analyzed. The results show that the performance of evaporator can be improved by inserting a bayonet tube into the liquid channel, including better averaging function of temperature, reduction in the peak temperature on the inner surface of capillary porous wick, and better adaptability in working environment. However, bayonet tube parameters should be carefully chosen depending on specific working conditions.

Abstract: From the perspective of microscopic mechanism to study the origin and the macroscopic behavior of the magnetic viscosity characteristics need to discuss the magnetic viscosity effects of the magnetic fluid dynamics, and the magnetic viscous forces in the magnetic fluid dynamics equations is the root cause of the magnetic viscosity effects. In the paper, the common expressions of first-order viscous force and quatratic viscous force of the magnetic fluid are derived from combining the magnetic fluid viscosity expression forms under different concentrations together, while based on the molecular circulation theory and electromagnetic dynamics principle, the quatratic magnetic viscous force model of magnetic fluid is derived from the basic relationship between the magnetic relaxation process. Furthermore the coefficient correction model of the quatratic viscous force is given when the solid particles of magnetic fluid present the formation of chain. Finally it shows the magnetic fluid viscous force model and a clear description of the external magnetic field influence on the magnetic fluid viscosity changes.

Abstract: The theory and method of analyzing the no-load magnetic field of single phase synchronous generator(SPSG) is presented in this article, and the no-load voltage of SPSG is simulated based on ANSYS program. The no-load voltage simulation results of a SPSG resemble its test results, which prove the simulation method in this article is correct and effective. The simulation results can provide theoretical bases and method for engineers in optimizing the design parameters to improve the power supply quality of SPSG.

Abstract: Nano-structures on the wing of Morpho butterflies generate bright blue color, and this color is sensitive to ambient gas, or more specifically, the refractive index of ambient gas. It was found that even slight change of the refractive index can lead to obvious change of the color. Such phenomenon has caught much attention and was employed as a sensing principle for detecting gas. In the present study, a typical nano-structure on the wing of Morpho butterflies is mimicked and simplified for constructing a refractive index based gas sensor. Moreover, partial derivative of the optical reflection efficiency with respect to the refractive index of ambient gas, i.e., sensitivity of the sensor, is utilized based on the rigorous coupled-wave analysis (RCWA) method. Finally, the effects of the nano-structure’s shape on the partial derivative are analyzed. The results can be applied to the design of the bioinspired refractive index based gas sensor.

Abstract: The cold closed-die forging of spur gears brings the problems of great forming forces , low life of the dies and insufficent corner filling. The two-step forming technology is presented. First, the billet is pre-forged by closed-die forging for getting most of tooth profile. Second, the gear is finish-forging by local loading. The finite element method is used to simulate the cold forging process.The strain distributions, the stress distributions, velocity distributions and load-stroke curve are investigated.. The simulation results show that the technology can guarantee the full filling effect, and decrease the forming force remarkably. The results of simulation and analysis were verified by the physics experiment.

Abstract: The bonding of fiber reinforced polymer (FRP) strips and plates to the concrete structures has been found to be an effective technique for flexural strengthening. The FRP is then under both pulling and peeling forces, resulting in a combination of shear sliding and opening displacement along the FRP/concrete interface. A novel experimental set-up is studied that a peeling load is applied on the FRP sheet by a circular rod placed into the central notch of the beam. Based on the linear-elastic fracture mechanics approach, a theoretical analysis is conducted on specimens representing the peeling behavior. From the numerical analysis, the load–displacement curves, load–stiffness of FRP sheet curves, and load–fracture energy curves affected by different variables are discussed. The peel load is related to the FRP sheet stiffness and to the interfacial fracture energy. Therefore, only two material parameters, the interfacial fracture energy of FRP–concrete interface and stiffness of FRP sheets, are necessary to represent the interfacial fracture behavior. The theoretical load–deflection curves of specimens agree well with the corresponding experimental results in the literatures.

Abstract: The bonding of fiber reinforced polymer (FRP) plates or sheets to the concrete structures has been found to be an effective technique to improve the capacity. As a result, a large number of studies have addressed debonding failures in FRP-strengthened RC structures, with many of them being focussed on understanding the behaviour of simple FRP-to-concrete bonded joints in which an FRP plate/sheet is bonded to a concrete prism and is subject to a tensile force. With the help of features of FRP–concrete interface and experimental data in the literatures, a non-linear mode II interface law is presented. The proposed interface law includes non-linear contributions of adhesive and concrete cover at high shear stresses. The numerical results presented in this study show that FRP strains, shear stresses, slips and values of delamination force in the bonded region are in good agreement with experimental results. The agreement verifies the validity of the proposed interface law.

Abstract: In the paper the results of different numerical solutions of bioheat transfer problems are presented. The base of numerical algorithms constitute the models containing the bioheat transfer equation (or equations) and the adequate geometrical, physical, boundary and initial conditions. In the first part of the paper the solutions concerning the transient temperature field in the biological tissue subjected to the strong external heat sources (freezing, burns) are presented. Next, the examples of sensitivity analysis application in the range of bioheat transfer are discussed. In the final part of the paper the inverse problems are formulated and the example concerning the identification of thermal parameters is shown.