A non-probabilistic reliability topology optimization method based on aggregation function and matrix multiplication considering buckling response constraints

A non-probabilistic reliability topology optimization method is proposed based on the aggregation function and matrix multiplication.The expression of the geometric stiffness matrix is derived,the finite element linear buckling analysis is conducted,and the sensitivity solution of the linear buckling factor is achieved.For a specific problem in linear buckling topology optimization,a Heaviside projection function based on the exponential smooth growth is developed to eliminate the gray cells.The aggregation function method is used to consider the high-order eigenvalues,so as to obtain continuous sensitivity information and refined structural design.With cyclic matrix programming,a fast topology optimization method that can be used to efficiently obtain the unit assembly and sensitivity solution is conducted.To maximize the buckling load,under the constraint of the given buckling load,two types of topological optimization columns are constructed.The variable density method is used to achieve the topology optimization solution along with the moving asymptote optimization algorithm.The vertex method and the matching point method are used to carry out an uncertainty propagation analysis,and the non-probability reliability topology optimization method considering buckling responses is developed based on the transformation of non-probability reliability indices based on the characteristic distance.Finally,the differences in the structural topology optimization under different reliability degrees are illustrated by examples.

The effect of anode axial position on the performance of a miniaturized cylindrical Hall thruster with a cusp-type magnetic field

A 200 W cylindrical Hall thruster with a cusp-type magnetic field was proposed, manifesting convergent plume and high specific impulse. In this paper, a series of ring-shaped anodes are designed and the influence of anode axial position on the performance of CHT with a cusp-type magnetic field is studied. The experimental results indicate that the thruster keeps stable operation at the condition of 140–270 W discharge power. When the anode moves axially towards the upstream cusp field, the thrust enhances from 6.5 mN to 7.6 mN and specific impulse enhances from 1658 s to 1939 s significantly. These improvements of thruster performance should be attributed to the enhancement of current utilization, propellant utilization and acceleration efficiency. According to the analyses on the discharge characteristics, it is revealed that as the anode moves upstream, the electron transport path could be extended, the magnetic field in this extended path could impede electron cross-field transport and facilitate the ionization intensity, yielding to the enhancement of current utilization and propellant utilization efficiency.Moreover, along with this enhancement of upstream ionization at the given anode flow rate, the main ionization region is thought to move upstream and then separate more apparently from the acceleration region, which has been demonstrated by the narrowing of ion energy distribution function shape. This change in acceleration region could decrease the ion energy loss and enhance acceleration efficiency. This work is beneficial for optimizing the electrode structure of thruster and recognize the ionization and acceleration process under the cusp magnetic field.

Stretchable magnesium-air battery based on dual ions conducting hydrogel for intelligent biomedical applications

Flexible and bio-integrated electronics have attracted great attention due to their enormous contributions to personalized medical devices.Power sources,serving as one of the most important components,have been suffering from many problems,including deficient biocompatibility,poor stretchability,and unstable electrical outputs under deformed conditions,which limits the practical applications in flexible and bio-integrated electronics.Here,we reported a fully stretchable magnesium(Mg)–air battery based on dual-ions-conducting hydrogels(SDICH).The high-performance battery enables long-term operation with lighting 120 lighting emitting diodes(LEDs)for over 5 h.Benefiting from the advanced materials and mechanical designs,the battery exhibits stability electrical outputs under stretching,which allows to operate ordinarily under various mechanical deformations without performance decay.Furthermore,the great biocompatibility of the battery offers great opportunity for biomedical applications,which is demonstrated by a self-adaption wound dressing system.The in vitro and in vivo results prove that the self-adaption wound dressing can effectively prevent wound inflammation and promote wound healing.By exploiting thermal feedback mechanics,the system can adjust antibiotic release rate and dosage spontaneously according to the real-time wound conditions.The proposed fully stretchable Mg-air battery and self-adaption wound dressing display great potential in skin-integrated electronics and personalized medicine.

Numerical Study of Pipeline Distribution Effect on the Performance of Pasty Propellant Rocket Motor

This paper reports the numerical research on PPRM(pasty propellant rocket motor)through computational fluid dynamics simulation along with pipeline design comparison based on simulation results.The structure of PPRM includes feed pipelines,and the propellant is distributed in a cone shape when burnt steadily in the combustion chamber.As a result,the internal flow field presents strong 3-dimensional characteristics,which may lead to the flow instability.To accurately understand the combustion flow field and flow instability in the PPRM,a numerical simulation of the combustion chamber considering propellant pyrolysis and chemical reaction,coupled with the feed system module,is employed in the research.The effect of pipeline distribution,including the pipeline location and the nonuniformity of pipeline diameter on the internal combustion flow characteristics as well as the motor thrust,was investigated.The results show that the vortex caused by the special conical shape of the burning surface leads to pressure oscillations.By adjusting the pipeline location and the nonuniformity of pipeline diameter,the distribution of vortex varies dramatically,which leads to different oscillation frequencies and amplitude.Under some pipeline distribution schemes,there is almost no large vortex in the rocket motor,which greatly eliminates the flow acoustic coupling oscillation of the motor.The oscillation amplitude decreases from about 5.7%to less than 0.1%.The results will help guide the design of the high-performance feed system and combustion chamber of PPRM.