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To quantitatively study the coupled dynamic behavior of vehicles in collision with semirigid guardrails, a coupled numerical model is established based on the finite element method. This model comprehensively integrates the nonlinear dynamic behavior of both the vehicle body and the guardrail structure. We validate the numerical results by comparing them with experimental findings and theoretical empirical formulas, confirming the accuracy of the coupled numerical model. This quantitative study investigates the influence of vehicle speed, column wall thickness, and collision angle on this coupled dynamic behavior to help optimize practical guardrail engineering designs. The results indicate that the sensitivity values of the collision speed, column wall thickness, and collision angle according to the baseline model are 1.0, 1.0, and 0.741, respectively. The parameters with higher sensitivity values are the key factors to consider in designs. Thus, the coupled numerical model can be used to optimize the design of semirigid guardrails in practical engineering. [ABSTRACT FROM AUTHOR]

Two-dimensional (2D) materials have attracted increasing interest due to their excellent properties and various applications such as energy storage, sensors, composites and catalysis. Recently, 2D van der Waals (vdW) layered materials, MoSi2N4 and WSi2N4, have been synthesized successfully by CVD methods. Here, we have investigated the structure, optoelectronic properties and electron–hole excitation characteristics of two-dimensional MoSi2N4, MoSi2P4, and WSi2N4 using first-principles calculations to determine whether they can be applied for photocatalytic hydrolysis. The results showed that replacing N atoms in 2D MoSi2N4 with P atoms could not only reduce the bandgap, but also make the band position more negative, while replacing Mo atoms with W atoms could expand and move the bands towards more positive direction. H+ ions can obtain electrons to generate H2 from the conduction band of WSi2N4 where the conduction band minimum (CBM) and valence band maximum (VBM) is –0.43 and –2.49 eV, respectively. Time-dependent density functional theory is used to explain that the experimentally measured UV–Vis spectra in which visible light absorption is broader and more intense in WSi2N4 than in MoSi2N4 and WSi2N4 is a promising photocatalyst for H2 generation from water. [ABSTRACT FROM AUTHOR]

Aiming at the strain distribution around the atomic lattice defect with void and crack in crystal materials, a new elastic strain calculation method named as center atom model (CAM) is proposed in this work, and is applied for mapping the strain field of the defect with void in an atomic image lattice in real space under external forcing. As an example, the strain mapping of voids and cracks of an atomic lattice image from phase field crystal (PFC) model is quantitatively characterized by CAM. The results show that CAM can well be used to extract the strain information from various types of the defect surface of atomic lattice images. Wherever the strain distribution around the dislocation of the grain boundary or the strain around the void and crack is, CAM can accurately extract the strain distribution of the distortion area of the atomic lattice. CAM can also be easily extended and applied to the strain mapping of the defects in the heterogeneous interface. [ABSTRACT FROM AUTHOR]

BACKGROUND: Calcium is an essential macronutrient for plant growth. Although it has been shown that exogenous Ca application can increase plant resistance to abiotic stress, little is known about its potential to enhance plant tolerance to biotic stress. Here, we investigated whether pretreatment of wheat (Triticum aestivum L.) seeds with calcium chloride (CaCl2) improves plant resistance against wheat aphid (Schizaphis graminum Rondani). The developmental time, population size, feeding behavior of aphids on plants grown from CaCl2‐ and water‐pretreated seeds, and plant defense responses to aphid attack were investigated. RESULTS: Seed pretreatment with CaCl2 extended aphid development time and reduced aphid population size and feeding efficiency. In addition, the pretreatment significantly increased the concentration of Ca2+ in wheat leaves, and upregulated expression levels of TaCaM genes and callose synthase genes (TaGSL2, TaGSL8, TaGSL10, TaGSL12, TaGSL19, TaGSL22 and TaGSL23). Callose concentration in the leaves of plants grown from CaCl2‐pretreated seeds increased significantly upon aphid attack. Further, callose deposition was observed mainly in the phloem. CONCLUSION: These results suggest that seed pretreatment with CaCl2 primes the plant response against wheat aphid attack, leading to modulation of callose deposition in the phloem in response to aphid attack. © 2021 Society of Chemical Industry. [ABSTRACT FROM AUTHOR]

The growth of voids has an important influence on the crack and fracture of metal materials. A new atomistic method, i.e., the phase field crystal, is used to simulate the void evolution and dislocation emission of the lattice deformation process. During the deformation process, the void changes its shape as the applied strain increases. Influenced by the direction of the strain application and the orientation of the lattice atoms, the void is transformed from the original circular shape to a square shape. As the strain increases, a pair of dislocation is generated on left and right sides of the void, and pushes out on the two sides. Then, the dislocation pair is emitted from the void, and departs from it, and does the climbing movement. Finally, the dislocation pair is broken down into two independent dislocations. Using the model of the void launching dislocation, the interaction among dislocations and void in the deformation process is analyzed, and the influence of the void emitting dislocation in the void growth in the deformation process is revealed. [ABSTRACT FROM AUTHOR]

The phase-field-crystal (PFC) method is used to investigate migration of grain boundary dislocation and dynamic of strain-driven nucleation and growth of deformed grain in two dimensions. The simulated results show that the deformed grain nucleates through forming a gap with higher strain energy between the two sub-grain boundaries (SGB) which is split from grain boundary (GB) under applied biaxial strain, and results in the formation of high-density ensembles of cooperative dislocation movement (CDM) that is capable of plastic flow localization (deformed band), which is related to the change of the crystal lattice orientation due to instability of the orientation. The deformed grain stores the strain energy through collective climbing of the dislocation, as well as changing the orientation of the original grain. The deformed grain growth (DGG) is such that the higher strain energy region extends to the lower strain energy region, and its area increase is proportional to the time square. The rule of the time square of the DGG can also be deduced by establishing the dynamic equation of the dislocation of the strain-driven SGB. The copper metal is taken as an example of the calculation, and the obtained result is a good agreement with that of the experiment. [ABSTRACT FROM AUTHOR]