MicroRNAs (miRNAs) are endogenous small RNAs of ~22 nucleotides (nt) that play a key role in down regulation of gene expression at the post-transcriptional level in plants and animals. Various studies have identified numerous miRNAs that were either up regulated or down regulated upon stress treatment. Here, we sought to understand the temporal regulation of miRNAs in different plant species under abscisic acid (ABA) and salt (NaCl) stress. Our results showed that the regulation of miR398 in response to ABA and salt stress was more dynamic in plants than previously reported. In poplars, miR398 was first induced upon 3-4 h of ABA or salt stress. However, this induction declined after 48 h and finally accumulated again over a prolonged stress (72 h). We referred to this kind of regulation as dynamic regulation. In contrast, such dynamic regulation of miR398 under salt stress was completely absent in Arabidopsis, in which miR398 was steadily and unidirectionally suppressed. Interestingly, ABA treatment caused a deviate dynamic regulation of miR398 in Arabidopsis, showing an opposite response as compared to that in poplars. We referred to the difference in regulation between Arabidopsis and poplars as differential regulation. Furthermore, the expression of the miR398 target, copper superoxide dismutase1 (CSD1), was in reverse correlation with the miR398 level, suggesting a control of this specific target expression predominantly by miR398 under abiotic stress. Together, these data consistently show a correlated regulation between miR398 and its representative target, CSD1, by ABA and salt stresses, and raise the possibility that regulation of miRNAs in plants is twofold: a dynamic regulation within a plant species and a differential regulation between different plant species.
Tailor rolled blanks (TRB) is made by flexible rolling system. And the thickness of TRB can be determined according to the load of this section. With its good bearing capacity and designed, it can be used to make automotive body for reducing the material and lower the weight. This paper describes the rolling process of TRB, and rolling simulation model of TRB was constructed using Deform-3D. The result curve of TRB rolling simulation was compared with a given target curve to determine the TRB rolling implementation, and had a simple analysis about the factors of each cross section during rolling. This research will give a guidance to realize the rolling of TRB.
As one of the best ways to lightweight car-white-body, tailor rolling blanks (TRB) are affected by various factors when produced, such as friction, rotational speed of working rolls, adjusting speed of rollers gap, rolling force, roller stiffness, etc. In this paper, a three-level three factors orthogonal table was set up and various tests were simulated by using orthogonal design method and Deform-3D software. Take the comparison of simulated curve with the target curve as experimental index, one set of optimal rolling parameters was found by variance analysis to the experiment results. This researching results can provide technical support for production of TRB, and promote the TRB application in the car lightweight.
The finite element software DYNAFORM was applied to simulate the whole tube hydroforming process. Two main failure types in the process of hydroforming are wrinkling and bursting. The strain distribution and thickness distribution at different process parameters were presented. Not only friction coefficient but also the effect of different matching of internal pressure and axial force was simulated and analyzed. In addition, the velocity of punch was considered too. The result has reference value for the variable cross-section tube hydroforming process research.
Thermosetting resin composite material has been widely used in strengthening the concrete members. However, there are only a few applications in strengthening steel structure. Based on the finite element analysis software ANSYS in this article, mechanical analysis are carried out for the lower chord before and after reinforcement of the long-span steel truss bridge and comparison are made. Interlaminar stresses in X, Y, Z three directions of the composite laminates are extracted. Compared with the results, the conclusion that application of composite materials for reinforcement of the lower chord can change the stress of the lower chord and improve the quality of the steel trussed bridge is drawn out.
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