The investigation of a portable solar telescope with a high gain metamaterial antenna for F10.7 radio flux measurement.

A high gain and high aperture efficiency metamaterial (MTM) antenna is applied to a solar telescope in this paper. First, a portable solar telescope including the MTM antenna and a receiving system is presented. Next, the theory of the MTM antenna is proposed and analyzed based on the ray-tracing model. The designed MTM antenna is composed of a dual circularly polarized Fabry-Pérot resonant antenna (FPRA) and four phase correction metasurfaces (PCMs). The proposed PCMs act as the reflection surface and the phase correction surface at the same time. Every PCM consists of 2 × 18 optimized artificial magnetic conductor (AMC) units. To solve the parallel incidence and narrow bandwidth problems of AMC units, a nonuniform partially reflective surface is designed. Compared with traditional FPRA, the proposed MTM antenna has an increase in peak gain of 37.5% and an aperture efficiency of 11.4%. Then, a receiving system composed of the receiver, equatorial mount, data acquisition module, and display module is presented for solar radio signal processing. Finally, the designed MTM antenna and solar telescope are simulated and measured. A good agreement between the simulation and measurement is observed and can be used to verify this design.

Solid-gas carbonate formation during dust events on Mars.

Electrostatic discharge experiments under simulated martian atmospheric conditions indicate that atmospheric CO2 has been sequestered into carbonate by the Mars dust activities during the Amazonia era.

High precision and real-time acquisition system for interface stress measurement in bridge bearing.

Since the damage of the bridge structure may cause great disasters, it is necessary to monitor its health status, especially the bridge bearing, the important connecting component of the bridge's upper and lower structures. Nowadays, manual inspection is the main method to get the information of the bridge bearings' work status. However, occasional damage of bridge bearing may not be detected in time, and sometime the installation position of the bearing makes the manual inspection on bridge bearing difficult and even impossible. Therefore, in order to know the work status of the bridge bearings timely, an intelligent remote monitoring system for the bridge bearing is developed. A 32-channel real-time acquisition system is designed by using an AD7768-1 analog-to-digital converter and Xilinx Spartan-6 Field Programmable Gate Array for interface stress continuously acquired in the bridge bearing. To assure the good linearity and low noise performance of the monitoring system, the data acquisition card is meticulously designed to reduce noise from both hardware and software and realize high-precision acquisition. Through the establishment of the monitoring server, the compressive stress data can be displayed synchronously and the overpressure situation can be alarmed in real-time. The experimental results show that the accuracy of the calibrated sensor is within 1.6%, and the detection error of the acquisition board is less than 200 µV. The acquisition system is deemed to have considerable advantages in accuracy and applicability.

A deep learning method for the recognition of solar radio burst spectrum.

Solar radiation is the excitation source that affects the weather in the atmosphere of the earth, and some solar activities such as flares and coronal mass ejections are often accompanied by radio bursts. The spectrum of solar radio bursts is helpful for astronomers to explore the mechanism of radio bursts. With the development and progress of solar radio spectrum observation methods, the observation of the Sun can be done at almost all times of day. How to quickly and automatically identify the small proportion of burst data from the huge corpus of observation data has become an important research direction. The innovation of this study is to enhance the original radio spectrum dataset with unbalanced sample distribution, and a neural network model for solar radio spectrum image classification is proposed on this basis. This hybrid structure of joint convolution and a memory unit overcomes the shortcoming of the traditional convolution or memory model, which can only extract one-sided features of an image. By extracting the frequency structure features and time-series features at the same time, the sensitivity to the small features of the spectrum image can be enhanced. Based on the data of the Solar Broadband Radio Spectrometer (SBRS) in China, the proposed network model can improve the average classification accuracy of the spectrum image to 98.73%, which will be helpful for related astronomical research.

A Dual-Band High-Gain Subwavelength Cavity Antenna with Artificial Magnetic Conductor Metamaterial Microstructures.

This paper presents dual-band high-gain subwavelength cavity antennas with artificial magnetic conductor (AMC) metamaterial microstructures. We developed an AMC metamaterial plate that can be equivalent to mu-negative metamaterials (MNMs) at two frequencies using periodic microstructure unit cells. A cavity antenna was constructed using the dual-band AMC metamaterial plate as the covering layer and utilizing a feed patch antenna with slot loading as the radiation source. The antenna was fabricated with a printed circuit board (PCB) process and measured in an anechoic chamber. The |S11| of the antenna was -26.8 dB and -23.2 dB at 3.75 GHz and 5.66 GHz, respectively, and the realized gain was 15.2 dBi and 18.8 dBi at two resonant frequencies. The thickness of the cavity, a sub-wavelength thickness cavity, was 15 mm, less than one fifth of the long resonant wavelength and less than one third of the short resonant wavelength. This new antenna has the advantages of low profile, light weight, dual-frequency capability, high gain, and easy processing.

Effects of high temperature after pollination on physicochemical properties of waxy maize flour during grain development.

BACKGROUND: Waxy maize is grown in South China, where high temperatures frequently prevail. The effect of high-temperature stress on grain development of waxy maize is not known. RESULTS: High temperature decreased the grain fresh weight and volume, and lowered the grain dry weight and water content after 22 days after pollination (DAP). Plants exposed to high temperature had low starch content, and high protein and soluble sugar contents at maturity. Starch iodine binding capacity and granule size were increased by heat stress at all grain-filling stages. The former parameter decreased, while the latter parameter increased gradually with grain development. High temperature increased the peak and breakdown viscosity before 30 DAP, but the value decreased at maturity. Pasting and gelatinization temperatures at different stages were increased by heat stress and gradually decreased with grain development under both high-temperature and control conditions. Gelatinization enthalpy increased initially but decreased after peaking at 22 DAP under both control and heat stress conditions. High temperature decreased gelatinization enthalpy after 10 DAP. Retrogradation percentage value increased with high temperature throughout grain development. CONCLUSION: High temperature after pollination changes the dynamics of grain filling of waxy maize, which may underlie the observed changes in its pasting and thermal properties.

Effects of heat stress during grain filling on the structure and thermal properties of waxy maize starch.

Clarifying the waxy maize starch physicochemical characteristics response to heat stress could modify starch quality. The effects of heat stress during grain filling (1-40day after pollination) on starch structure and thermal properties of four waxy maize varieties were investigated. The mean day/night temperature during grain filling for heat stress and control treatments was 35.2/16.1°C and 27.4/15.6°C, respectively. Heat stress during grain filling increased the starch average granule size and the proportion of long chains in amylopectin. Starch granules under heat stress presented more pitting or uneven surfaces. X-ray peak intensities in response to heat stress were variety dependent. Heat stress during grain filling decreased the swelling power and increased the gelatinization temperature and retrogradation percentage, while the gelatinization enthalpy was not affected. In conclusion, heat stress during grain filling significantly affected structural characteristics of waxy maize starch and consequently, changed its swelling and thermal properties.

Effects of high temperature during grain filling under control conditions on the physicochemical properties of waxy maize flour.

The effects of high temperature during different grain filling stages (1-15 d and 16-30 d after pollination) on the physicochemical properties of four varieties of waxy maize grain were studied. Heat stress during grain filling decreased grain weight and starch deposition, while it increased protein content, starch granule size, abnormal granule numbers and iodine binding capacity. These effects were more severe when heat stress was introduced at early development stage than at late grain filling stage. The peak intensities and crystallinities were decreased when plants were exposed to high temperature at early development stage. By contrast, responses to high temperature at late development stage were variety-dependent. High temperature during grain filling decreased the peak and breakdown viscosities and increased the gelatinization temperature and enthalpy, and retrogradation percentage of flours, especially during early development stage. In conclusion, high temperature during grain filling changed the grain proximate and starch structure, resulting in the deterioration of pasting and thermal properties.