Influence and Correction of Wavefront Primary Aberrations for Radio Telescopes using Aberration Theory

Dual-reflector antennas are widely used in astronomical observations and satellite communication.Structural deformations of the reflectors for radio telescopes are inevitable in outside working conditions due to exterior environment loads,which will cause distortion in the surface of the primary reflector and displacement of the subreflector,then lead to gain degradation and misalignment.In this paper,the influence and correction of misalignment in a dual-reflector antenna have been studied.From the perspective of wavefront aberration,a method is proposed to correct the wavefront primary aberration by adjusting the subreflector position.The characteristics of wavefront errors caused by structural deformation of the reflector have been analyzed,and relationships between the position motions of the subreflector and the Seidel wavefront aberrations are derived.The adjustment quantities of the subreflector are also derived.The results show the appropriate positional change of the subreflector in the lateral and axial directions can effectively correct the effects of the tilt and defocus in the primary aberrations caused by antenna structural deformations.

Design of RFSoC-based Digital Phased Array Feed(PAF)and Hybrid Architecture Beamforming System

As the number of array elements and bandwidth increase,the design challenges of the Phased Array Feed(PAF)front-end and its signal processing system increase.Aiming at the ng-PAF of the 110 m radio telescope,this article introduces the concept of fully digital receivers and attempts to use Radio Frequency System-on-Chip(RFSo C)technology to digitize close to the feed array,reduce the complexity and analog components of the front-end,and improve the fidelity of the signals.The article discusses the digital beamforming topology and designs a PAF signal processing experimental system based on RFSo C+GPU hybrid architecture.The system adopts a ZCU111board to design RF-direct digitization and preprocessing front-end,which can sample eight signals up to 2.048GSPS,12 bit,channelize the signals into 1024 chunks,then reorder into four data streams and select one of the 256MHz frequency bands to output through four 10 Gb links.A GPU server is equipped with four RTX 3090 GPUs running four HRBF_HASHPIPE instances,each receiving a 64 MHz bandwidth signal for high-throughput realtime beamforming.The experimental system uses a signal generator to emulate Sa-like signals and propagates through rod antennas,which verifies the effectiveness of the beamforming algorithm.Performance tests show that after algorithm optimization,the average processing time for a given 4 ms data is less than 3 ms in the four-GPU parallel processing mode.The RFSo C integrated design shows significant advantages in power consumption and electromagnetic radiation compared with discrete circuits according to the measurement results.

Distribution of charged lunar dust in the south polar region of the moon

Lunar dust is one of the most threatening problems confronting the return of human beings to the moon.In this work we studied the spatial distribution behavior of charged lunar dust in the solar wind plasma environment in the south polar region of the moon and considered the influence of a mini-crater using Spacecraft Plasma Interactions Software.The distribution of dust and plasma at low solar altitude angles of 20°and 0°was studied,and the spatial density of lunar dust was~10^(10.4)m^(-3)and~10^(11.5)m^(-3),respectively.This is because a higher surface potential will result in transportation of small dust particles and photoelectrons can also neutralize positively charged lunar dust.The dust density in the plasma void region created by a mini-crater with a 5 m high wall was studied.We obtained a quasi-neutral electric environment in the plasma void region of the mini-crater,and the dust density was about a magnitude lower than that in other regions.The dust risk to a spacesuit is much lower on the nightside than on the dayside,but there is severe charged lunar dust transport in the region between light and shade,which is dominated by the difference in surface and plasma potential caused by photoelectrons.

Si对热轧铁素体-贝氏体双相钢显微组织变化和机械性能的影响

系统的研究了si对铁素体-贝氏体双相（FBDP）钢显微组织变化、拉伸性能、冲击韧性和拉伸凸缘性的影响，从0到0．95％加人si可促进细的铁素体等轴晶的形成，高Si（0．95％）时也可导致块状马氏体岛和残余奥氏体的形成。随si含量的增加屈服强度、抗拉强度和延伸率提高，因此，由于加入si提高了应变硬化速率，改善了抗拉强度和韧性之间的平衡。孔扩张后的裂纹形貌表明FBDP钢有极好的拉伸凸缘性，这与显微裂纹在铁素体相内扩展以及铁素体晶粒沿与裂纹垂直方向延伸有关。含0．95％Si钢与含0．55％Si钢相似都有高强度与高冲击韧性组合，特别是含0．95％Si钢表现出极好的抗拉强度与拉伸凸缘性组合。

Microstructure and Tensile Properties of a Nb–Mo Microalloyed 6.5Mn Alloy Processed by Intercritical Annealing and Quenching and Partitioning

The transformation behavior, microstructural evolution and mechanical properties were compared in a coldrolled Nb–Mo microalloyed 6.5Mn alloy after intercritical annealing（IA） and quenching and partitioning（Q ＆ P）,respectively. The thermodynamic calculation and theoretical analysis were used to determine the optimal heat treatment parameters. The Q ＆ P samples exhibited relatively higher strength with relatively low ductility, mainly due to the hard martensite matrix, which resulted in continuous yielding behavior upon loading, whereas the IA samples showed the significantly improved ductility, which benefited from the more sufficient transformation-induced plasticity（TRIP） effects and the softer ultrafine ferrite matrix. The dependence of yield point elongation（YPE） of IA samples on grain size demonstrated that the YPE value was in the reverse proportional relationship to the average grain size, which agreed well with theoretical analysis.