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In order to effectively suppress the influence of mutual coupling between array elements on antenna radiation performance, a novel dual-circle microstrip patch array antenna with low mutual coupling and low correlation is proposed. Two deformed E-shaped electromagnetic bang gap (EBG) structures are symmetrically inserted between two circular antenna elements, which could suppress the surface waves propagation to reduce the mutual coupling through theoretical analysis and experimental verification. In addition, several arc-shaped gap defected ground structures (DGS) are symmetrically etched on the ground plane to curb the ground coupling current, thus, the mutual coupling is further decreased. The shortest distance between the two circular antenna elements is only 0.19λ where λ is the wavelength at the working frequency of 5.8 GHz. Both the simulated and experimental results indicate that the mutual coupling of less than -40 dB and the envelope correlation coefficient (ECC) value of less than 0.001 can be achieved by the proposed decoupling antenna within its operating bandwidth, to make the good decoupling effect under the premise of small antenna size and stable radiation performance.

This paper investigates the impacts of element grouping on the covert communication performance of an active reconfigurable intelligent surface (ARIS)-aided uplink non-orthogonal multiple access (NOMA) system. Through element grouping, each element of the ARIS works in either the reflecting mode to reflect the information signal or the jamming mode to generate a jamming signal. Optimizing the NOMA transmit power, ARIS beamforming, and receive beamforming jointly is necessary to maximize the covert communication rate. To tackle the unsolvable covert communication rate maximization problem, we decouple the original problem into three sub-problems of optimizing the NOMA transmit power, ARIS beamforming, and receive beamforming, respectively. To tackle the mixed-integer non-linear programming for the element grouping, we introduce the arithmetic- and geometric-mean-based penalty term and apply the Dinkelbach transform to reformulate the optimization problem. Next, we propose an alternating optimization algorithm to optimize the system parameters. The numerical results demonstrate the effectiveness of the element grouping in improving the covert communication rate. However, the element grouping scheme achieves a lower covert communication rate performance compared to the scheme without element grouping, indicating that using element grouping for covert communications in the ARIS-aided uplink NOMA system is not the preferred option. [ABSTRACT FROM AUTHOR]

The development of urea oxidation reaction (UOR) and oxygen evolution reaction (OER) bifunctional electrocatalysts has dual significance in promoting hydrogen energy production and urea-rich wastewater treatment. Herein, a carboxylated multi-walled carbon nanotube (MWCNT–COOH)–ferrocene carboxylic acid (Fc–COOH) modulated NiMOF hybrid material (MWCNT–NiMOF(Fc)) has been synthesized for dual electrocatalysis of the UOR and OER. The material characterization results indicated that MWCNT–COOH and Fc–COOH were integrated into the framework structure of the NiMOF. The direct interaction between the NiMOF and MWCNT/Fc facilitated electron transfer in the hybrid material and led to lattice strain, which improved the charge transfer kinetics, promoted the exposure of more unsaturated Ni sites, and increased the electrochemically active surface area. These factors together enhanced the electrocatalytic activity of MWCNT–NiMOF(Fc) towards the UOR and OER. Using a glassy carbon electrode as the substrate, MWCNT–NiMOF(Fc) exhibited low potential requirements, low Tafel slopes, and high stability. In overall urea and water splitting electrolysis cells, the excellent UOR and OER dual functional catalytic ability and enormous practical application potential of the MWCNT–NiMOF(Fc) modified foam nickel electrode were further demonstrated. On the basis of the above research, the influence of a KOH environment on urea electrolysis was further studied, and the urea electrolysis products were analyzed, promoting a more comprehensive understanding of the catalytic performance of MWCNT–NiMOF(Fc) for urea oxidation. This study provides a new approach for developing high-performance NiMOF-based electrocatalysts for challenging bifunctional UOR/OER applications, and has potential application value in hydrogen production from urea-containing wastewater electrolysis. [ABSTRACT FROM AUTHOR]

In order to solve the problem of the clearance on the slider-crank mechanism and improve the position precision of the slider-crank mechanism. Starting from the simple mechanism of slider-crank mechanism,the simplified model is established. By using the sensor to measure the movement parameters of artifacts of the slider-crank mechanism,then system parameters of the slider-crank mechanism are identified by using the method of parameter identification. Finally,the model of the slider-crank mechanism with clearance is established and the simulation analysis is carried out. The comparison results show that the model of using the method of parameter identification has high accuracy and modeling process is simple,a new train of thought for complex nonlinear modeling of the electromechanical system is provided.

Objective. This study aimed to explore the genes regulating lymph node metastasis in colorectal cancer (CRC) and to clarify their relationship with tumor immune cell infiltration and patient prognoses. Methods. The data sets of CRC patients were collected through the Cancer Gene Atlas database; the differentially expressed genes (DEGs) associated with CRC lymph node metastasis were screened; a protein–protein interaction (PPI) network was constructed; the top 20 hub genes were selected; the Gene Ontology functions and the Kyoto Encyclopedia of Genes and Genomes pathways were enriched and analyzed. The Least Absolute Shrinkage and Selection Operator (LASSO) regression method was employed to further screen the characteristic genes associated with CRC lymph node metastasis in 20 hub genes, exploring the correlation between the characteristic genes and immune cell infiltration, conducting a univariate COX analysis on the characteristic genes, obtaining survival-related genes, constructing a risk score formula, conducting a Kaplan–Meier analysis based on the risk score formula, and performing a multivariate COX regression analysis on the clinical factors and risk scores. Results. A total of 62 DEGs associated with CRC lymph node metastasis were obtained. Among the 20 hub genes identified via PPI, only calcium-activated chloride channel regulator 1 (CLCA1) expression was down-regulated in lymph node metastasis, and the rest were up-regulated. A total of nine characteristic genes associated with CRC lymph node metastasis (KIF1A, TMEM59L, CLCA1, COL9A3, GDF5, TUBB2B, STMN2, FOXN1, and SCN5A) were screened using the LASSO regression method. The nine characteristic genes were significantly related to different kinds of immune cell infiltration, from which three survival-related genes (TMEM59L, CLCA1, and TUBB2B) were screened. A multi-factor COX regression showed that the risk scores obtained from TMEM59L, CLCA1, and TUBB2B were independent prognostic factors. Immunohistochemical validation was performed in tissue samples from patients with rectal and colon cancer. Conclusion. TMEM59L, CLCA1, and TUBB2B were independent prognostic factors associated with lymphatic metastasis of CRC. [ABSTRACT FROM AUTHOR]