Numerical analysis on the effect of process parameters on deposition geometry in wire arc additive manufacturing

Here we develop a two-dimensional numerical model of wire and arc additive manufacturing(WAAM)to determine the relationship between process parameters and deposition geometry,and to reveal the influence mechanism of process parameters on deposition geometry.From the predictive results,a higher wire feed rate matched with a higher current could generate a larger and hotter droplet,and thus transfer more thermal and kinetic energy into melt pool,which results in a wider and lower deposited layer with deeper penetration.Moreover,a higher preheat temperature could enlarge melt pool volume and thus enhance heat and mass convection along both axial and radial directions,which gives rise to a wider and higher deposited layer with deeper penetration.These findings offer theoretical guidelines for the acquirement of acceptable deposition shape and optimal deposition quality through adjusting process parameters in fabricating WAAM components.

Structural analysis of receptor-like kinase SOBIR1 reveals mechanisms that regulate its phosphorylation-dependent activation

Plant leucine-rich repeat(LRR)receptor-like kinases(RLKs)and LRR receptor-like proteins(RLPs)comprise a large family of cell surface receptors that play critical roles in signal perception and transduction.Both LRR-RLKs and LRR-RLPs rely on regulatory LRR-RLKs to initiate downstream signaling pathways.BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE 1/SOMATIC EMBRYOGENESIS RECEPTOR KINASE 3(BAK1/SERK3)and SUPPRESSOR OF BIR1-1(SOBIR1)are important and extensively studied regulatory LRR-RLKs with distinct functions.Although the regulatory mechanism of BAK1 activation has been studied in detail,the activation mechanism of SOBIR1 remains poorly understood.Here,the crystal structures of the catalytically inactive kinase domain of SOBIR1(SOBIR1-KD)from Arabidopsis thaliana were determined in complexes with AMP-PNP and Mg^(2+).The results show that SOBIR1-KD contains a uniquely long β3-αC loop and adopts an Src-like inactive conformation with an unusual architecture at the activation segment,which comprises three helices.Biochemical studies revealed that SOBIR1 is transphosphorylated by BAK1 following its autophosphorylation via an intermolecular mechanism,and the phosphorylation of Thr529 in the activation segment and the β3-αC loop are critical for SOBIR1 phosphorylation.Further functional analysis confirmed the importance of Thr529 and the β3-αC loop for the SOBIR1-induced cell death response in Nicotiana benthamiana.Taken together,these findings provide a structural basis for the regulatory mechanism of SOBIR1 and reveal the important elements and phosphorylation events in the special stepwise activation of SOBIR1-KD,the first such processes found in regulatory LRR-RLKs.