magnetic field

The position of the cathode concerning the magnetic field map inside the discharge channel affects the performance and lifetime of the Hall effect thruster. The neutralizer cathode has two important functions in the Hall effect thruster. Almost %18 cathode electrons enter the discharge channel of the Hall thruster and provide the necessary electrons for ionization. The rest of the electrons neutralize the ions coming out from the thruster and the spacecraft remains neutral regarding electric charge. In this article, the map of the magnetic field and separatrix lines inside the thruster are simulated with FEMM software. According to the position of the magnetic field separatrix lines, the neutralizer cathode is placed in three different positions, and the Hall effect thruster performance is simulated using the XOOPIC code and the PIC-MCC method. Shifting the position of the cathode relative to the magnetic field lines and the field separatrix line, significant changes were observed in the parameters of the cathode voltage, the thrust force, and the thruster's specific impact, which improves the thruster's performance. The results of this research show that the performance parameters of the thruster are optimized due to increasing the lifetime of the cathode when the cathode is placed between the first and second separatrix lines.

The use of intelligent or adaptable materials and structures for the optimal use of materials and space is one of the new technologies that has recently become very popular in the construction industry of concrete structures. In this research, one of these technologies in the concrete industry was investigated. Samples containing piezoelectric aggregate (quartz) cause internal reactions by receiving a magnetic field during load application, which were studied in this study. The magnetic field affects the cement mortar containing piezoelectric aggregate. The compressive strength of mortar containing quartz aggregate and zeolite powder under magnetic field was significantly increased compared to the control sample which did not contain quartz aggregate and zeolite and without magnetic field. Compressive strength under magnetic field increased by 100% in some samples. The researchers also found that the interaction effect of increasing the replacement percentage of quartz and zeolite and applying a magnetic field had an optimal point. In most samples in this research, increasing the percentage of Quartz and zeolite or magnetic field, resulted in increase in compressive strength up to a point, however, after that optimum point it started to decrease.

In the present study, the heat transfer of unsteady fluid flow between two oscillation plates under the influence of a magnetic field was investigated. The bottom plate was considered fixed and the upper plate could move closer or farther down to the bottom plate. The fluid flow was considered Newtonian, incompressible, two-dimensional, laminar, and unsteady. The governing equations including continuity, momentum and energy were in the form of partial differential equations (PDE); hence, they were transformed into ordinary differential equations (ODE) using similarity transformation. As an innovative method, the ODE governing equations were solved using a semi-analytical method named the Collocation Method (CM). For validity, a numerical 4th order Runge-Kutta method was used. The results revealed that by increasing the magnetic parameter, the horizontal velocity component decreased while the dimensionless temperature and heat transfer rate increased. An increase in the compression parameter led to a reduction of horizontal velocity component, dimensionless temperature, and heat transfer rate. Moreover, when Prandtl and Ecker numbers increased, the dimensionless temperature and heat transfer rate on the walls also increased.