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Multi-beam microwave antennas have attracted enormous attention owing to their wide range of applications in communication systems. Here, we propose a broadband metamaterial-based multi-beam Luneburg lens-antenna with low polarization sensitivity. The lens is constructed from additively manufactured spherical layers, where the effective permittivity of the constituting elements is obtained by adjusting the ratio of dielectric material to air. Flexible microstrip patch antennas operating at different frequencies are used as primary feeds illuminating the lens to validate the radiation features of the lens-antenna system. The proposed Luneburg lens-antenna achieves ±72° beam scanning angle over a broad frequency range spanning from 2 GHz to 8 GHz and presents a gain between 15.3 dBi and 22 dBi, suggesting potential applications in microwave- and millimeter-wave mobile communications, radar detection and remote sensing. [ABSTRACT FROM AUTHOR]

Food safety inspections are an essential aspect of food safety monitoring. Rapid, accurate, and low-cost food analysis can considerably increase the efficiency of food safety inspections. The lateral flow immunochromatographic assay (LFIA) technique has recently grown in popularity due to its ease of use and high efficiency. It is currently commonly utilized in food inspection. In this review, we briefly introduce the principle and classification of LFIA, critically discuss the recent application status of LFIA in food contaminantion detection, and finally propose that artificial intelligence and information technology will further advance the development of LFIA in the field of food safety monitoring. [ABSTRACT FROM AUTHOR]

AlCrFeNi multi-component alloys with excellent mechanical properties have been designed and extensively investigated in recent years. The massive fabrication of sheets will be an effective way for industrial application, where hot rolling is the inevitable process. After hot rolling, the mechanical properties could be further tailored. In this study, the effects of heat treatments on a dual-phase Al17Cr10Fe36Ni36Mo1 hot-rolled plate were systematically investigated, including: (i) annealing (700 °C, 850 °C, 1000 °C and 1150 °C for 1 h, respectively), (ii) solution and single aging (1150 °C for 1 h and 700 °C for 4 h), (iii) solution and double aging (1150 °C for 1 h, 700 °C for 4 h and 650 °C for 1 h). The B2 precipitates with varied morphologies were observed in the FCC matrix of the hot-rolled alloy after a heat treatment range from 700 °C to 1000 °C for 1 h, and the BCC particles in the B2 matrix were dissolved when the heat treatment temperature was higher than 1000 °C. The hot-rolled alloy heat treated at 700 °C for 1 h had the highest yield strength, and the hot-rolled alloy treated at 1150 °C for 1 h showed the lowest yield strength. After a solution at 1150 °C for 1 h, aging at 700 °C for 4 h and 650 °C for 1 h, the L12 phase and BCC particles were precipitated in the FCC and B2 matrices, and B2 nanoprecipitates were observed around the FCC grain boundaries. The solution and double aging alloy exhibit the tensile strength of 1365.7 ± 9.5 MPa, a fracture elongation of 14.2 ± 1.5% at 20 °C, a tensile strength of 641.4 ± 6.0 MPa, and a fracture elongation of 16.9 ± 1.0% at 700 °C, showing great potential for application. [ABSTRACT FROM AUTHOR]

To further clarify the impact of different rootstocks in grafted blueberry, fruit quality, mineral contents, and leaf gas exchange were investigated in 'O'Neal' blueberry (Vaccinium corymbosum) grafted onto 'Anna' (V. corymbosum) (AO), 'Sharpblue' (V. corymbosum) (SO), 'Baldwin' (V. virgatum) (BO), 'Plolific' (V. virgatum) (PO), and 'Tifblue' (V. virgatum) (TO) rootstocks and own-rooted 'O'Neal' (NO), and differences in anatomic structures and drought resistance were determined in AO, TO, and NO. The findings revealed that fruit quality in TO and PO was excellent, that of BO and SO was good, and that of AO and NO was medium. 'Tifblue' and 'Plolific' rootstocks significantly increased the levels of leaf phosphorus and net photosynthetic rate of 'O'Neal', accompanied by a synchronous increase in their transpiration rates, stomatal conductance, and intercellular CO2. Additionally, the comprehensive evaluation scores from a principal component analysis based on anatomic structure traits from high to low were in the order TO > AO > NO. The P50 (xylem water potential at 50% loss of hydraulic conductivity) values of these grafted plants descended in the order NO > AO > TO, and the branch hydraulic conductivity of TO and sapwood hydraulic conductivity of TO and AO were significantly lower than those of NO. Thus, TO plants exhibited the strongest drought resistance, followed by AO, and NO, and this trait was related to the effects of different rootstocks on the fruit quality of 'O'Neal' blueberry. These results provided a basis for a deeper understanding of the interaction between rootstocks and scions, as well mechanisms to improve blueberry fruit quality. [ABSTRACT FROM AUTHOR]

Concrete is a versatile material widely used in modern construction. However, concrete is also subject to freeze–thaw damage, which can significantly reduce its mechanical properties and lead to premature failure. Therefore, the objective of this study was to assess the laboratory performance and freeze–thaw damage characteristics of a common mix proportion of concrete based on compressive mechanical tests and acoustic technologies. Freeze–thaw damage characteristics of the concrete were evaluated via compressive mechanical testing, mass loss analysis, and ultrasonic pulse velocity testing. Acoustic emission (AE) technology was utilized to assess the damage development status of the concrete. The outcomes indicated that the relationships between cumulative mass loss, compressive strength, and ultrasonic wave velocity and freeze–thaw cycles during the freezing–thawing process follow a parabola fitting pattern. As the freeze–thaw damage degree increased, the surface presented a trend of "smooth intact surface" to "surface with dense pores" to "cement mortar peeling" to "coarse aggregates exposed on a large area". Therefore, there was a rapid decrease in the mass loss after a certain number of freeze–thaw cycles. According to the three stages divided by the stress–AE parameter curve, the linear growth stage shortens, the damage accumulation stage increases, and the failure stage appears earlier with the increase in freeze–thaw cycles. In conclusion, the application of a comprehensive understanding of freeze–thaw damage characteristics of concrete based on compressive properties and acoustic parameters would enhance the evaluation of the performance degradation and damage status for concrete structures. [ABSTRACT FROM AUTHOR]

Rice production in the Anhui province is threatened by fungal diseases. We obtained twenty-five fungal isolates from rice and wild rice leaves showing leaf spot disease collected along the Yangtze River. A phylogenetic analysis based on internal transcribed spacer (ITS), translation elongation factor 1 alpha (TEF1-α), and beta tubulin (TUB2) sequences revealed one isolate (SS-2-JB-1B) grouped with Nigrospora sphaerica, one (QY) with Nigrospora chinensis, twenty-two with Nigrospora oryzae, and one isolate (QY-2) grouped in its own clade, which are related to but clearly different from N. oryzae. Nineteen tested isolates, including sixteen strains from the N. oryzae clade and the three isolates of the other three clades, caused disease on detached rice leaves. The three isolates that did not belong to N. oryzae were also able to cause disease in rice seedlings, suggesting that they were rice pathogens. Isolate QY-2 differed from the other isolates in terms of colony morphology, cell size, and susceptibility to fungicides, indicating that this isolate represents a new species that we named Nigrospora anhuiensis. Our analysis showed that N. sphaerica, N. chinensis, and the new species, N. anhuiensis, can cause rice leaf spot disease in the field. This research provides new knowledge for understanding rice leaf spot disease. [ABSTRACT FROM AUTHOR]

With the increasing use of the strategy and group target attack method in the modern battlefield, multi-target inverse synthetic aperture radar (ISAR) imaging simultaneously with high efficiency draws more and more attention, which gives a promising prospect for aerospace target detection and recognition in the multi-target scenario. To overcome the shortcomings of traditional multi-target imaging with one beam at one pulse repetition time (PRT) based on phase array radar (PAR), this paper proposes a novel multi-target imaging waveform design method based on the newly full digital array radar (DAR). Firstly, we propose using radar waveform diversity with 2D orthogonality to realize multi-target ISAR imaging with high imaging quality and efficiency. Then, to meet the constant modulus requirement for maximizing the transmitting power, orthogonal frequency division multiplexing (OFDM) chirp theory is proposed to directly generate the transmit waveform instead of the traditional optimization method with the nonconvex problem for waveform design. Based on time-variant weighted and time diversity technology, a of group transmit waveforms is designed, which can form multiple beams simultaneously and make the signals arriving at different targets approximately orthogonal. Finally, simulations and experiments are carried out to demonstrate the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

The multiple-input multiple-output synthetic aperture radar (MIMO SAR) system has developed rapidly since its discovery. At the same time, the low-disturbance and high-gain requirements of the MIMO system are continuing to increase. Through the application of digital beamforming (DBF) techniques, the multidimensional waveform encoding (MWE) technique can play a key role in MIMO systems, which can greatly improve the system's performance, especially the multi-mission capability of radar. Intrapulse beamsteering in elevation is a typical form of multi-dimensional waveform encoding which can greatly improve the transmitting efficiency and multi-mission performance of radar. However, because of the high sensitivity of the DBF technique to height, there is significant deterioration in performance in the presence of terrain undulations. The OFDM (Orthogonal Frequency Division Multiplexing) technique is widely used in communication. Due to the similarity of radar and communication systems and the great waveform diversity of OFDM signals, the OFDM radar has recently begun to emerge as a new radar system, simultaneously, the orthogonality of OFDM signals is in the time and frequency domains, and is not affected by terrain undulation. So, this paper proposes a novel radar mode combining intrapulse beamsteering in elevation and OFDM-Chirp signals, that is, the combination of "beam orthogonality" and "waveform orthogonality", which can greatly improve the performance and fault tolerance to interference signals. In this manuscript, the system working mode and signal processing flow are introduced in detail, and simulations for both point targets and distributed targets are carried out to verify the feasibility of the proposed mode. Simultaneously, a comparison experiment is carried out, which shows the high level of fault tolerance to terrain undulation and the high potential of the proposed radar mode in Earth observation. [ABSTRACT FROM AUTHOR]