Enhanced predictor–corrector Mars entry guidance approach with atmospheric uncertainties

Due to the long-range data communication and complex Mars environment, the Mars lander needs to promote the ability to autonomously adapt uncertain situations ensuring high precision landing in future Mars missions. Based on the analysis of multiple disturbances, this study demonstrates an enhanced predictor–corrector guidance method to deal with the effect of atmospheric uncertainties during the entry phase of the Mars landing. In the proposed method, the predictor–corrector guidance algorithm is designed to autonomously drive the Mars lander to the parachute deployment. Meanwhile, the disturbance observer is designed to onboard estimate the effect of fiercely varying atmospheric uncertainties resulting from rapidly height decreasing. Then, with the estimation of atmospheric uncertainties compensated in the feed-forward channel, the composite guidance method is put forward such that both anti-disturbance and autonomous performance of the Mars lander guidance system are improved. Convergence of the proposed composite method is analysed. Simulations for a Mars lander entry guidance system demonstrates that the proposed method outperforms the baseline method in consideration of the atmospheric uncertainties

Physical Model Test on the Deformation Mechanism of Reservoir Bank Slopes With Sand Layers Under Coupled Hydro-Mechanical Conditions

A reservoir area is mostly located in the canyon area, and the geological structure is complex. There are a large number of unstable slopes on the bank of the reservoir. The stability of bank slope is greatly affected by water storage and reservoir water regulation. In addition, sudden rainstorm and other external factors can reduce slope stability. In this article, the physical model test is used to study the seepage field and deformation characteristics of typical reservoir bank slopes with sand layers under different rainfall intensities, different water level fluctuation rates, and their coupling effects. The model has a length of 4.0 m, a width of 1.0 m, and a height of 0.9 m, and the piezometers and white balls are used to monitor the pore water pressures and displacements inside the slope model individually. The results show that the responsiveness of pore water pressure inside the slope lags behind both water level fluctuation and rainfall. The lag time is inversely proportional to the water level fluctuation rates under the single water level fluctuation condition, while it is proportional to water level fluctuation rates in the water level decline stage under the coupling effect condition. The rapid impoundment of the reservoir area has a strengthening effect on the stability of the reservoir bank slope. However, accelerated deformation of the slope occurs in the stage of water level decline, and the deformation rate is proportional to the water level fluctuation rates

Development of mine-used flameproof three-phase asynchronous motor with high voltage and high efficiency

In view of problems of energy waste and environmental pollution caused by high power consumption and low efficiency of existing motors, a mine-used flameproof three-phase asynchronous motor with high voltage and high efficiency was developed. Development goals, selection of slot matching of stator and rotator, determination of punch size of stator and rotator, main parameters design in electromagnetic calculation, and structure design of the motor were introduced detailedly. Prototype test results show that test values of efficiency of the developed motor are more than the value of energy efficiency grade of 1evel 1 in GB 30254-2013 High Voltage Three-phase Cage Asynchronous Motor Energy Efficiency Limit and Energy Efficiency Level, and at the same time, it can meet design requirements of low noise and low vibration

Numerical Simulation on the Flow and Temperature Field in the High-Power Motor

The ventilation structure affects the internal wind road and air distribution of the motor directly, and then has a great influence on motor heat dissipation. Focusing on the 5000kW 10kV high-power motor, this paper establishes a numerical analysis model which has been validated by experiment. Based on the established numerical model, the flow field and temperature field inside the motor under the conditions of variable ambient temperature and variable inlet air velocity are analyzed. The finding demonstrates that the maximum temperature and average temperature of the stator and rotor of the motor increase with the increase of the ambient temperature, and the increase rate of change is basically unchanged, and that decrease with the increase of the inlet air velocity. When the inlet air velocity increase to a certain value, the maximum temperature and average temperature of the motor stator and rotor decrease relatively slowly. This thesis analyses the motor ventilation cooling system and temperature distribution, and provides a theoretical basis for the optimization of motor ventilation structure

Seismic Performance of Composite Shear Walls Constructed Using Recycled Aggregate Concrete and Different Expandable Polystyrene Configurations

The seismic performance of recycled aggregate concrete (RAC) composite shear walls with different expandable polystyrene (EPS) configurations was investigated. Six concrete shear walls were designed and tested under cyclic loading to evaluate the effect of fine RAC in designing earthquake-resistant structures. Three of the six specimens were used to construct mid-rise walls with a shear-span ratio of 1.5, and the other three specimens were used to construct low-rise walls with a shear-span ratio of 0.8. The mid-rise and low-rise shear walls consisted of an ordinary recycled concrete shear wall, a composite wall with fine aggregate concrete (FAC) protective layer (EPS modules as the external insulation layer), and a composite wall with sandwiched EPS modules as the insulation layer. Several parameters obtained from the experimental results were compared and analyzed, including the load-bearing capacity, stiffness, ductility, energy dissipation, and failure characteristics of the specimens. The calculation formula of load-bearing capacity was obtained by considering the effect of FAC on composite shear walls as the protective layer. The damage process of the specimen was simulated using the ABAQUS Software, and the results agreed quite well with those obtained from the experiments. The results show that the seismic resistance behavior of the EPS module composite for shear walls performed better than ordinary recycled concrete for shear walls. Shear walls with sandwiched EPS modules had a better seismic performance than those with EPS modules lying outside. Although the FAC protective layer slightly improved the seismic performance of the structure, it undoubtedly slowed down the speed of crack formation and the stiffness degradation of the walls

Nap1l1 Controls Embryonic Neural Progenitor Cell Proliferation and Differentiation in the Developing Brain

Summary: The precise function and role of nucleosome assembly protein 1-like 1 (Nap1l1) in brain development are unclear. Here, we find that Nap1l1 knockdown decreases neural progenitor cell (NPC) proliferation and induces premature neuronal differentiation during cortical development. A similar deficiency in embryonic neurogenesis was observed in Nap1l1 knockout (KO) mice, which were generated using the CRISPR-Cas9 system. RNA sequencing (RNA-seq) analysis indicates that Ras-associated domain family member 10 (RassF10) may be the downstream target of Nap1l1. Furthermore, we found that Nap1l1 regulates RassF10 expression by promoting SETD1A-mediated H3K4 trimethylation at the RassF10 promoter. Nap1l1 KO defects may be rescued by RassF10 overexpression, suggesting that Nap1l1 controls NPC differentiation through RassF10. Our findings reveal an essential role for the Nap1l1 histone chaperone in cortical neurogenesis during early embryonic brain development. : Nap1l1 plays essential roles in embryonic neurogenesis, including the proliferation and differentiation of neural progenitors. Qiao et al. find that Nap1l1 regulates RassF10 through SETD1A-mediated H3K4me3 of the RassF10 promoter. Keywords: neural progenitor cell, neural differentiation and proliferation, cortex development, gain of function, loss of function, histone chaperone, Nap1l1, RassF10, H3K4me

Friction and wear behaviors of biodegradable Mg-6Gd-0.5Zn-0.4Zr alloy under simulated body fluid condition

The friction and wear behaviors of biodegradable Mg-6Gd-0.5Zn-0.4Zr (wt%, GZ60K) alloy were evaluated under simulated body fluid (SBF) condition using ball-on-disk configuration and compared with those under dry sliding condition. The results show that under dry sliding and SBF conditions, the friction coefficient declines with increasing applied load and keeps stable with prolonging sliding time. The friction coefficient of the alloy effectively decreases in SBF as compared to dry sliding due to lubrication caused by SBF. The real wear rates under SBF condition are lower than those under dry sliding condition for each parameter. Nevertheless, the nominal wear rates are higher in SBF which are attributed to the more mass loss caused by corrosion but not wear. Both the nominal wear rate in SBF and the dry sliding wear rate increase with increasing applied load, and they decline firstly and then keep stable with prolonging sliding time. It is concluded that the wear of the alloy is restricted by the SBF, but the corrosion of the alloy is aggravated by the wear. Keywords: Biodegradable Mg alloy, SBF, Friction coefficient, Wear behavio