Tianjin Rubber Industry Institute (China)

This paper presents a novel framework that integrates STAR-RIS with NOMA to improve system performance. The primary goal is to achieve the maximum of the overall sum rate. To tackle this aim, the original optimization problem is decomposed into three distinct subproblems: the beamforming design for STAR-RIS, the optimization of trajectory, and the power allocation. A penalty-based method is employed in the STAR-RIS beamforming subproblem to enhance beamforming efficiency and overall system performance. These subproblems are iteratively solved to obtain suboptimal solutions. Simulations validate that the proposed framework significantly outperforms traditional methods in terms of sum rate, yielding substantial gains in spectral efficiency and system performance.

ABSTRACT The maturation process is an important means of industrially regulating NR. It is of great significance to understand the change rule of properties in the maturation process for the production and processing of NR. In this study, the effects of maturation time on the nonrubber components, microstructure, and macroscopic properties of NR were examined. The test results of nitrogen content showed that the protein content of NR decreased with the extension of maturation time. The results of the solid NMR and gel content test showed that the molecular chain entanglements of the rubber increased and that the natural network structure increased during the maturation process. The test results of the vulcanization curves showed that the scorching time of the rubber was significantly shortened with the prolongation of the maturation time; The test results of crosslinking density showed that the crosslinking density decreased with the extension of maturation time. The test results of compression heat build-up and Akron abrasion showed that the heat build-up of the rubber increased and that the wear resistance deteriorated during the maturation process. In addition, when the maturation time was 2 days, the rubber had the highest molecular weight, highest storage modulus, smallest loss factor, best dispersion of carbon black, and best mechanical properties and aging resistance.

Abstract The laser frequency spectrum, whose full width at half-maximum in the frequency domain is the laser bandwidth, plays a critical role in atomic multi-step photoionization processes and has a significant influence on isotopic selective photoionization results. In this study, two phase-independent frequency spectrum models, that is, the mode jitter model (MJ model) based on the mode jitter phenomenon and the multi-longitudinal mode model (MLM model) based on multi-longitudinal mode output, are proposed to describe the spectral characteristics in the frequency domain. In the MJ model, it is assumed that there is a time-varying longitudinal mode in each laser pulse, with different central frequencies between adjacent pulses in the pulse train; in the MLM model, it is assumed that multiple longitudinal modes are output simultaneously with fixed central frequencies. Selective photoionization properties of these two frequency spectrum models and the chaotic field model are simulated and compared with each other under the Lorentzian frequency spectrum condition. Influences of the excitation intensity, laser frequency spectral profile and cutoff frequency on selective photoionization processes are calculated and compared among the above-mentioned three frequency spectrum models. Finally, the measurement of the laser frequency spectrum and the introduction of individual longitudinal modes’ bandwidths are discussed.

Abstract The solidification technology of natural rubber exerts a significant impact on the properties of natural rubber. The solidification technology of alkaline protease has been highly valued by researchers at home and abroad because of its good solidification effect, excellent vulcanization performance, and low pollution. In this study, the effects of alkaline protease solidification technology and enzyme dosage on the structure and properties of natural rubber were investigated and compared with those of formic acid solidification technology. The solid‐state NMR results showed that increasing the enzyme dosage increased the molecular chain entanglements in the raw rubber. The gel content test results showed that the natural network structures (i.e. gels) increased after the addition of alkaline protease. The test results of the vulcanization characteristics showed that the addition of alkaline protease significantly shortened the positive vulcanization time. The Mw was the largest at an enzyme dosage of 0.07%. The test results for mechanical properties showed that the mechanical properties were best when the enzyme dosage was 0.07%. In addition, as the alkaline protease dosage increased, the Akron abrasion volume of natural rubber decreased, and the Akron abrasion volume was the lowest at an enzyme dosage of 0.07%.

Abstract Modification and improvement of aging resistance in nuclear power environment for the ethylene‐propylene‐diene (EPDM) rubber has been attracting the attention of scientists. In this article, graphite modified EPDM composites (ultrafine graphite [UG]/EPDM) were prepared, and effect of graphite with sizes of 13, 2.6, and 1.3 μm on the processability, vulcanization parameters, mechanical properties, stability of radiation aging of EPDM composites were investigated, respectively. The results showed that EPDM rubber was an irradiated crosslinked polymer. The Mooney viscosity and crosslinking density of EPDM gradually increased with increasing graphite content under the effect of physical and chemical cross‐linking of graphite. The lamellar structure of graphite particles in the rubber matrix is beneficial to improvement of the mechanical properties and aging resistance of the EPDM composites and play a reinforcing role, and the sp2 hybrid structure of graphite can trap and quench free radicals, delayed the irradiation aging of EPDM. UG/EPDM composites irradiation stability was improved with increasing graphite dispersion in EPDM matrix. Under the cumulative irradiation dose of 1000 kGy, the tensile strength of blank sample and UG‐2.6 μm−10 decreased by 51.1% and 17.7%, respectively, and the hardness increased by 8.7% and 4.9%, respectively. The energy storage modulus and the corresponding glass transition temperature (Tg) of UG/EPDM composites enhanced with graphite, while the thermal stability of the composites was improved.

Amomum villosum, which is an important perennial medicinal plant, easily suffers from continuous cropping obstacles in the plantation. The aim of this study is to find an effective method to solve the problem of A. villosum continuous cropping. In this study, we analyzed four fields in which A. villosum was continuously cropped and a fallow field to reveal the effects of continuous cropping on the rhizosphere soil physicochemical properties, enzyme activities, and bacterial and fungal communities. Most of the soil nutrient contents gradually increased as the number of years of continuous cropping increased, whereas the soil pH decreased slightly. The soil urease and acid phosphatase activities tended to increase as the length of the continuous cropping period increased, which may have accelerated the conversion of soil substances. Furthermore, the alpha diversity of the bacterial and fungal communities decreased as the duration of the continuous cropping period increased. Additionally, the redundancy analysis revealed that bacterial and fungal community structures at the phylum level were the most correlated with pH value and catalase activity, respectively. This study may be useful for promoting the continuous cropping and sustainable development of A. villosum.