Advances in Astronomy

The nonlinear propagation of different types of DANW acoustic dust nonlinear waves has been investigated in a magnetized dusty plasma consisting of negatively charged dust particles, Maxwellian electrons, and ions. Application of the standard reductive perturbation theory is used to derive the corresponding three-dimensional nonlinear a complex Ginzburg–Landau (3D-CGLE) equation which governs the dynamics of the dust-acoustic wave packets. The stationary analytical solutions of the CGLE are numerically analysed where the effect of the physical parameters of the dusty plasma model on the wave’s propagation is taken into account. It has been found that there can be a relationship between the appearance of soliton waves and electromagnetic waves, as well as between shock-like waves and periodic travelling waves. Expression of the importance of these findings is the cornerstone of explaining the true relationship between the propagation of nonlinear waves in the physics of space, for example, the Earth’s magnetic field.

This study is about the effects of Yukawa-like corrections to Newtonian potential on the existence and stability of noncollinear equilibrium points in a circular restricted three-body problem when bigger primary is an oblate spheroid. It is observed that ∂x₀/∂λ = 0 = ∂y₀/∂λ at λ₀ = 1/2, so we have a critical point λ₀ = 1/2 at which the maximum and minimum values of x₀ and y₀ can be obtained, where λ ∈ (0, ∞) is the range of Yukawa force and (x₀, y₀) are the coordinates of noncollinear equilibrium points. It is found that x₀ and y₀ are increasing functions in λ in the interval 0 < λ < λ₀ and decreasing functions in λ in the interval λ₀ < λ < ∞ for all α ∈ α⁺. On the other hand, x₀ and y₀ are decreasing functions in λ in the interval 0 < λ < λ₀ and increasing functions in λ in the interval λ₀ < λ < ∞ for all α ∈ α⁻, where α ∈ (−1, 1) is the coupling constant of Yukawa force to gravitational force. The noncollinear equilibrium points are found linearly stable for the critical mass parameter β₀, and it is noticed that ∂β₀/∂λ = 0 at  = 1/3; thus, we got another critical point which gives the maximum and minimum values of β₀. Also, ∂β₀/∂λ > 0 if 0 < λ <  and ∂β₀/∂λ < 0 if  < λ < ∞ for all α ∈ α⁻, and ∂β₀/∂λ < 0 if 0 < λ <  and ∂β₀/∂λ > 0 if  < λ < ∞ for all α ∈ α⁺. Thus, the local minima for β₀ in the interval 0 < λ <  can also be obtained.

The aim of this work is to characterize, from a thermophysical perspective, the dark resistant unit (DRU) characterizing Germania Lacus in the Oxia Planum Region, providing new insights to constrain the nature of the materials which compose this unit. We investigated the temperature distribution of the DRU by adopting common values of the thermophysical parameters of the basalt and by exploring several values of porosity. As an additional case, we also explore a composition made of pebbles. The numerical model developed here represents a follow-up of the work recently published by Formisano et al. 2021, and it takes into account a large-scale topography of the site and assumes a diurnal temperature profile for the atmosphere rather than a constant value (unlike Formisano et al. 2021). Comparisons with Mars Pathfinder and Viking data as well as numerical models are also reported. The methodology described here could be useful to characterize as well other sites on Mars’ surface with available small-scale topographic data.

The higher the pointing accuracy of the radio telescope, the more obvious the influence of wind disturbance on antenna performance. Taking the site of the 110 m aperture QiTai radio Telescope (QTT) as an example, the terrain and air flow characteristics of the site are studied. It is found that the wind direction with high incoming wind frequency and relatively high speed is mostly located in the mountain gap on the periphery of the antenna. If the wind resistance facilities are precisely arranged in the upstream tuyere, the wind speed in the antenna area can be effectively reduced. This study proposes a method to control the wind flow at a telescope site based on the precise arrangement of the windbreak fence. The windbreak fence simulation model is constructed using the theory of porous jump. The mean error of the simulation results is less than 14% compared to the wind tunnel measured data, indicating that the constructed windbreak fence model has high reliability. The computational domain model of the working conditions for the site is constructed. The extreme condition of the windbreak fence arrangement is considered, and the simulation results show that the wind speed in the antenna area can be reduced by more than 30% through the control of the windbreak fence. It verifies the feasibility of the method of controlling the wind flow by the windbreak fence for the site which provides a reference for the subsequent research on the precise arrangement of the windbreak fence.

The restricted concave kite five-body problem is a problem in which four positive masses, called the primaries, rotate in the concave kite configuration with a mass at the center of the triangle formed by three of the primaries. The fifth body has negligible mass and does not influence the motion of the four primaries. It is assumed that the fifth mass is in the same plane of the primaries and that the masses of the primaries are , , , and , respectively. Three different types of concave kite configurations are considered based on the masses of the primaries. In case I, one pair of primaries has equal masses; in case II, two pairs of primaries have equal masses; in case III, three of the primaries have equal masses. For all three cases, the regions of central configuration are obtained using both analytical and numerical techniques. The existence and uniqueness of equilibrium positions of the infinitesimal mass are investigated in the gravitational field of the four primaries. It is numerically confirmed that none of the equilibrium points are linearly stable. The Jacobian constant is used to investigate the regions of possible motion of the infinitesimal mass.

There are many factors that cause pointing errors in radio telescopes. As one of the motion positioning mechanisms of the radio telescope, the error caused by the elevation mechanism cannot be ignored. The source of error in the elevation mechanism comes mainly from the key transmission components and the support structure. Accurate measurement of the errors caused by them is the key to analyzing their law of change. Aiming at the main error factors in the antenna elevation mechanism, this study builds a scaled-down experimental platform for the elevation mechanism and proposes an error measurement method based on multiencoder information sources. The method compares the error law of change of the antenna elevation mechanism under different driving modes, different centerline deviations of the bearings, and different backlashes and designs error measurement experiments for the abovementioned operating conditions. The results show that the error measurement method based on multiencoder information sources can accurately measure the error of the antenna elevation mechanism under different driving modes. The method can also accurately reflect the law of change in transmission error when the backlash of the elevation mechanism and the centerline deviation of the bearings increase. The final experimental measurement shows that the driving mode of the dual-motor can eliminate about 70% of the mechanism error caused by the backlash. The average value of the error increases by a factor of 1.9 when the backlash increases from 0.1 mm to 1.26 mm. The average value of the error increases by a factor of 5 when the centerline deviation of the bearings increases from 0 to 1.5 mm. This has a good reference value to correct for the pointing error of a radio telescope.