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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.

The traditional settlement monitoring has the problems of small monitoring range and low adaptability of settlement prediction model; Based on SBAS-InSAR technology and PSO-BP neural network algorithm, this paper constructs a PSO-BP settlement prediction model based on Sentinel-1A data. Take Jinan(E116°8’, N36°8’)the regional monitoring data is a data sample set. The algorithm proposed in this paper is compared with typical algorithms such as SVM. The results show that the MAE of 30 points predicted by this algorithm is 0.17, which is better than six typical algorithms such as SVM. This algorithm can be used as an effective means to provide early warning of surface subsidence.

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 (RFSoC) 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 RFSoC+GPU hybrid architecture. The system adopts a ZCU111 board to design RF-direct digitization and preprocessing front-end, which can sample eight signals up to 2.048 GSPS, 12 bit, channelize the signals into 1024 chunks, then reorder into four data streams and select one of the 256 MHz 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 real-time 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 RFSoC integrated design shows significant advantages in power consumption and electromagnetic radiation compared with discrete circuits according to the measurement results.

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 ∼ 1010.4 m−3 and ∼ 1011.5 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.

Coupling error is an important factor that affects the measurement accuracy of the contact scanning probe of a three-dimensional thread-measuring machine. To address this issue, this paper proposes a coupling error model for contact scanning probes. First, the mechanical structure of the contact scanning probe was introduced, and the main source of its coupling error was analyzed. Second, material mechanics was used to conduct a geometry–force analysis on the guiding mechanism of the probe, thereby establishing a coupling error model. Finally, the experiments were carried out to verify the accuracy of the coupling error model. From the experimental verification, the movement of the measuring head by 10 μm increased the deviation of the probe displacement by 2 μm, indicating the probe deflection. Moreover, the calculated probe deflection angle was consistent with the theoretical value, validating the proposed coupling error model. This method provides an important theoretical basis for the decoupling of measuring probe, thereby improving the accuracy of the probe guiding mechanism.

In this paper, the historical observation data of the power grid are used to build a predictive model of power outages for distribution network by using machine learning methods. By judging whether the distribution transformer network is about to fail, the maintenance and troubleshooting of the distribution network can be achieved in advance, thereby fundamentally reducing the occurrence of power fault of the distribution transformer. The data covers several dimensions such as distribution network loads, equipment ledgers, historical faults, weather and so on. The experiments show that the proposed method based on XGBoost is valid and efficiency for feeder fault early warning.

With the rapid development of renewable energy worldwide, the electricity from large-scale renewable energy bases is transmitted to load-intensive area by DC transmission lines, forming an AC-DC hybrid system with AC and DC coupling obviously and tightly. Measuring the development level of the AC-DC hybrid system is of great significance for grid construction and power transmission. This paper first establishes a kind of comprehensive evaluation system that reflects both the interaction of AC-DC and the overall system capability. Then the evaluation method combining the three methods of AHP-Entropy-TOPSIS is carried out relatively. Finally the evaluation system and method is applied in the actual grid example. The comprehensive evaluation system and method of AC-DC hybrid system constructed in this paper is of reference significance to power grid planning and operation management.

The muonic component of the extensive air showers (EAS) is of great importance for the astroparticle physics. It carries the information about the properties of primary cosmic ray (CR) particles, such as their mass, and electromagnetic and hadronic nature. It provides a sensitive test for the hadronic interaction models, which are inevitable for describing the cascade shower development of cosmic rays in EAS experiments. The YangBaJing Hybrid Array (YBJ-HA) experiment has been in operation since the end of 2016. Surface detectors are used for the measurements of primary energy, angular direction and core position of a shower event, while underground muon detectors are used for measuring the density of muons at various locations. Using the data obtained by the YBJ-HA experiment, this work reports the first measurement of the lateral muon distribution for the primary cosmic ray energy in the 100 TeV region. The punch-through effect is evaluated via MC simulation.

Ternary layered III–III–VI2-type metal chalcogenides are a comparatively new group of semiconductors and have attracted strong interest due to their distinct optical and electrical properties in view of potential applications in nonlinear optical, acousto-optical and optoelectronic devices. Here, we report on the fabrication of two-terminal phototransistors based on ultrathin direct-bandgap TlGaSe2 sheets for the first time. Devices exhibit typical p-type conducting behaviors with current on/off ratio of ~102 and gate-tunable transport characteristics. The photocurrent presents stable and reproducible response for various wavelengths of light from ultraviolet (UV) to near-infrared region, confirming the broadband photodetection capability. Photoresponsive behavior of ultrathin TlGaSe2 phototransistors can be modulated by the incident optical power density or wavelength, as well as bias or back-gate voltages. Owing to the presence of direct bandgap, devices possess high photoresponsivity (270 mA W−1) under white light in vacuum, and it is higher than that of single-layer MoS2 phototransistor and graphene photodetectors, accompanying by a fast response time of ~0.2 s. Our studies introduce ternary alloy monochalcogenides phototransistors, and expand the library of ultrathin flexible semiconductors.

We have extended the average-bond-energy method to study the strained-heterojunction band offset. Through a detailed study of the effect of hydrostatic and uniaxial strains on the energy of the average valence band edge Ev.av relative to the average bond energy, we find that Ev.av remains basically unchanged under different strain conditions, and that the deformation potential av.av corresponding to Ev.av is much smaller than the av for other analogous methods. Thus, in the average-bond-energy method, the valence band offset ?Ev can be obtained neglecting av.av. It is only necessary to calculate the valence band maximum energy relative to the average bond energy before the strain and to use the experimental values of the deformation potential b and spin-orbit splitting ?0 to determine the splitting value for the valence band. It is not necessary to calculate the band structures under various strain conditions. This simplified calculation method involves only a small calculational burden; therefore, it can conveniently be used to predict the strained-heterojunction band offset.

Patterns such as periodic subharmonic waves and kink-pairs are observed experimentally in a two-dimensional vertically vibrated granular layer located in an annular channel which has a sawtooth-shaped base. Using the thickness of the granular layer and external excitation as control parameters, we find the transitions between different patterns in the layer. The dependence of the kink-pair's velocity on the external excitation is revealed. The local velocity fields of the granular layer indicate that, in addition to horizontal transport in the layer, there is convection in the node area of a kink.

The fact that trapezoid clusters exist in 2D vertically vibrated granular systems leads us to construct a cluster model, in which wave-like motions are explained as the result of cluster-plate and cluster-cluster collisions. By analyzing the collision of one cluster with the plate in detail, we deduce a basic equation from velocity relationship, which could be separated into two correlative equations: one relates wave-like motion with exciting acceleration, and we call it the excitation condition; the other relates wavelength with exciting frequency, viz., the dispersion relation. The theoretical results are in agreement with the experimental ones, which supports the idea of the cluster model. Moreover, from the cluster model, we also predict a possibility of abnormal dispersion relation of a 2D granular system.