Papers by Author: Xin Xin Zhang

Abstract: Microalgae, in wet conditions, tend to grow on surfaces and form biofilms. The adhesion of microalgae to surfaces is very important for algal mass culture. The formation and development of microalgal biofims are in large denpend on the properties of cell surface, substratum surface and gowth medium. In this paper, the influence of substratum surface zeta potential on the microalgal biofilms was particularly investigated. We focused on a widely-used microalgal strain, the freshwater autotrophic Chlorella sp..The adhesion phenomena of Chlorella sp. to surfaces with different zeta potential were observed microscopically. It was found that Chlorella sp. adhered easily to the surface with a positive zeta potential and difficultly to the surface with a negative zeta potential. We concluded that the surface zeta potential had a greater influence on the adhesion of microalgal cells to substratum surfaces. Our findings have important implications for microalgae mass culture and harvesting.

Abstract: Thermodynamic analysis method for iron and steel manufacturing system is developed to describe the energy flow. The theoretical energy consumption for the manufacturing process is proposed to analyze the energy-saving potential. Energy balance based on enthalpy with a uniform reference state is established to analyze the amounts and forms of energy flow in the manufacturing system. The energy-saving potential of blast furnace system is discussed to choose the appropriate energy-saving methods and technologies.

Abstract: This paper studied the Magneto hydrodynamic (MHD) flow and heat transfer of an electrically conducting non-Newtonian fluid over a rotating disk in the presence of a uniform magnetic field. The steady, laminar and axial-symmetric flow is driven solely by the rotating disk, and the incompressible fluid obeys the inelastic Ostwald de-Waele power-law model. The governing differential equations were reduced to a set of ordinary differential equations by utilizing the generalized Karman similarity transformation. The nonlinear two-point boundary value problem is solved by multi-shooting method. Numerical results show that the magnetic parameter and the power-law index have significant effects on the swirling flow and heat transfer.

Abstract: With the aim of minimizing the energy consumption cost and taking the billet heating quality as the constraint condition, a mathematical model was established based on the billet heating model to solve the optimum heat institution of the reheating furnace. The tabu search algorithm was employed to solve the model. The results of the industrial production data optimization showed that the proposed mathematical model and the solving method could fully meet the practical production demand of the reheating furnace. In addition to satisfying the heating quality requirements, the energy consumption is reduced and the oxidation loss is decreased. Compared with the original one, the heating institution obtained from the mentioned model and algorithm had a better performance on energy efficiency.

Abstract: In this paper, a boundary layer analysis is presented for the slip flow of three types of incompressible viscous nanofluids past a permeable wedge in the presence of a magnetic field. Due to the appearance of a slip boundary condition at the surface, local similarity solution of the reduced nonlinear ordinary differential equation is obtained by the HAM coupled with minimizing the square residual error. The effects of pertinent parameters, such as the magnetic parameter, the solid volume fraction of nanoparticles, the slip parameter and the type of nanofluid on the flow, are analyzed and studied in details. It is found that Ag-water has the highest skin friction coefficient at the surface compared with the others.

Abstract: This paper presented an analysis for the couette flow of a generalized Oldroyd-B fluid within an infinite cylinder subject to a time-dependent shear stress with the influence of the internal constantly decelerated pressure gradient. The exact solutions are established by means of the combine of the sequential fractional derivatives Laplace transform and finite Hankel transform and presented by integral and series form in terms of the Mittag-Leffler function. Moreover, the effects of various parameters are analyzed in detail by graphical illustrations.

Abstract: The generalized differential transform method is implemented for solving time-fractional partial differential equations in fluid mechanics. This method is based on the two-dimensional differential transform method (DTM) and generalized Taylor’s formula. Results obtained by using the scheme presented here agree well with the numerical results presented elsewhere. The results reveal the method is feasible and convenient for handling approximate solutions of time-fractional partial differential equations.

Abstract: According to the technical demand of hot-rolling production in steel plant, a production scheduling mathematical model was proposed with the aim of reducing the production cost and optimizing the product quality. The scheduling of reheating furnaces which was summed up as the Boolean satisfiability problem was involved in rolling scheduling optimization which was summed up as the multiple traveling salesman problem with uncertain traveling salesman number, and a two-stage genetic-tabu algorithm was designed to solve the problem. It was shown that, the model could fully meet the demand of hot-rolling production. Compared to the human-computer method, the results had better performance on high production and energy efficiency.

Abstract: The derivation of effective thermal conductivity (ETC) for composite materials is a long-standing thermal transport problem. Based on the thermal resistance model and integration method, two analytical solutions of the ETC of composite materials, in which the dispersed phase consists of spheres in cubic arrangements, were derived either neglecting or considering the effect of radiation. As the effect of radiation in porous composite materials is considered, the theoretical result indicates that the effect of radiation cannot be neglected as the temperature or porosity of composite materials is high. The differences between the theoretical results and experimental data of the ETC of porous composite materials are acceptable.