Effects of low nitrogen on seedling growth, photosynthetic characteristics and antioxidant system of rice varieties with different nitrogen efficiencies.

Nitrogen plays a significant role in influencing various physiological processes in plants, thereby impacting their ability to withstand abiotic stresses. This study used hydroponics to compare the effects of three nitrogen supply levels (1N, 1/2N and 1/4N) on the antioxidant capacity of rice varieties JJ88 (nitrogen efficient) and XN999 (nitrogen inefficient) with different nitrogen use efficiencies. The results show that compared with the XN999 variety, the JJ88 variety has stronger adaptability to low-nitrogen conditions, which is mainly reflected in the relatively small decrease in dry weight and net photosynthetic rate (Pn); In the early stage of low-nitrogen treatment (0-7 d), the [Formula: see text] production rate, hydrogen peroxide (H2O2) and malondialdehyde (MDA) content of JJ88 variety increased relatively slightly, but the superoxide dismutase (SOD), peroxide The activity of enzyme (POD) and catalase (CAT) increased significantly; After low-nitrogen treatment, the ASA-GSH cycle enzyme activity of JJ88 variety was relatively high, and the dehydroascorbate reductase (DHAR) activity after 14 days of low-nitrogen treatment was higher than that of 1N treatment; The content of reduced ascorbic acid (ASA) in non-enzymatic antioxidants was lower than that of 1N treatment after 14 days of low nitrogen treatment; The contents of oxidized dehydroascorbic acid (DHA) and carotenoids (Car) were higher than those of 1N treatment after 21d and 14d of low nitrogen treatment respectively; The contents of reduced glutathione (GSH), oxidized glutathione (GSSG) and proline (Pro) showed a larger upward trend during the entire low-nitrogen treatment period. In summary, the JJ88 rice variety has a strong ability to regulate oxidative stress and osmotic damage under low nitrogen conditions. It can slow down plant damage by regulating antioxidant enzyme activity and antioxidant content. This provides a basis for achieving nitrogen reduction and efficiency improvement in rice and the breeding of nitrogen-efficient varieties.

Biomimetic Venus Flytrap Structures Using Smart Composites: A Review.

Biomimetic structures are inspired by elegant and complex architectures of natural creatures, drawing inspiration from biological structures to achieve specific functions or improve specific strength and modulus to reduce weight. In particular, the rapid closure of a Venus flytrap leaf is one of the fastest motions in plants, its biomechanics does not rely on muscle tissues to produce rapid shape-changing, which is significant for engineering applications. Composites are ubiquitous in nature and are used for biomimetic design due to their superior overall performance and programmability. Here, we focus on reviewing the most recent progress on biomimetic Venus flytrap structures based on smart composite technology. An overview of the biomechanics of Venus flytrap is first introduced, in order to reveal the underlying mechanisms. The smart composite technology was then discussed by covering mainly the principles and driving mechanics of various types of bistable composite structures, followed by research progress on the smart composite-based biomimetic flytrap structures, with a focus on the bionic strategies in terms of sensing, responding and actuation, as well as the rapid snap-trapping, aiming to enrich the diversities and reveal the fundamentals in order to further advance the multidisciplinary science and technological development into composite bionics.

Simulation and Experimental Study on the Internal Leak Behavior in Carbon Fiber Reinforced Composite Components.

In this paper, the diffusion law of helium gas inside composite materials was obtained through numerical research and an experimental approach. The influence of fiber and the fiber-resin interface on permeability was discussed in the actual numerical model. It was found that the leak rate and the mass concentration at the fiber-resin interface were higher than those in the resin, and the leak rate symmetrically distributed along the horizontal central line. Meanwhile, a homogenized model for the leak rate simulation in carbon fiber composite components was established, and its accuracy was verified through the experiment and the actual numerical model. The simulated result and the test data demonstrated that the leak rate increased with the pressure and decreased with the thickness of the specimen.

Optimization of Vibration Pretreatment Microwave Curing in Composite Laminate Molding Process.

Vibration pretreatment microwave curing is a high-quality and efficient composite out-of-autoclave molding process. Focusing on interlaminar shear strength, the effects of pretreatment temperature, pretreatment time and vibration acceleration on the molding performance of composite components were analyzed sequentially using the orthogonal test design method; a scanning electron microscope (SEM) and optical digital microscope (ODM) were used to analyze the void content and fiber-resin bonding state of the specimens under different curing and molding processes. The results show that the influence order of the different vibration process parameters on the molding quality of the components was: vibration acceleration > pretreatment temperature > pretreatment time. Within the parameters analyzed in this study, the optimal vibration pretreatment process parameters were: pretreatment temperature of 90 °C, pretreatment time of 30 min, and vibration acceleration of 10 g. Using these parameters, the interlaminar shear strength of the component was 82.12 MPa and the void content was 0.37%. Compared with the microwave curing process, the void content decreased by 71.8%, and the interlaminar shear strength increased by 31.6%. The microscopic morphology and mechanical properties basically reached the same level as the standard autoclave process, which achieved a high-quality out-of-autoclave curing and molding manufacturing of aerospace composite components.

Analysis of Deformation and Properties of Composite Melon Petals via Vibration Pretreatment-Microwave Compound Curing.

The transition of large-scale cryogenic propellant tanks from metal to composite materials is the main trend in the global aerospace industry. Aiming to address the challenges of achieving the manufacturing of integrated and cost-effective manufacturing of aerospace cryogenic composite tanks that cannot be realized through the conventional autoclave process, and those of existing out-of-autoclave processes that are unable to effectively suppress defects under low-pressure conditions, a vibration pretreatment was innovatively introduced into the microwave curing process of composite materials in this study. Based on a systematic analysis of the inhibitory mechanisms of vibration pretreatment on void formation and the uniform heating mechanisms of microwaves in composite materials, the experimental results showed that the compound curing process enabled the production of components with complex structural features under low-pressure conditions while achieving equivalent surface precision and comprehensive properties, including porosity, interlaminar shear strength, and cryogenic permeation resistance, as those obtained through the standard 0.6 MPa autoclave process. This holds great promise for the application of out-of-autoclave processes in the manufacturing of large-scale aerospace cryogenic composite tanks.

Finite Element Simulation and Experimental Research on Uniformity Regulation of Microwave Heating of Composite Materials.

As an attractive alternative to the traditional autoclave curing process, microwave curing has been widely used for manufacturing high-performance composites. However, the nonuniform temperature distribution during composite curing is the main problem faced by the microwave curing process, which limits its application in the aerospace industry. This paper studied the regulating effects of cavity structure and mechanical optimization methods on the uniformity of the microwave field by numerical analysis and finite element simulation, and an octagonal microwave heating device with multi-microwave generators, mode stirrers and mobile platform was developed independently and the experimental verification were finally carried out. The results showed that compared with the traditional heating device, the T800/602 carbon fiber reinforced composite laminates cured in the regulating device of microwave heating uniformity established in this paper had more uniform temperature field distribution, a more synchronous curing process and lower residual stresses.