An experiment and simulation study of the rebound effect in electromagnetic forming process

Electromagnetic forming (EMF) has been proved to be a useful method to form the aluminium alloy sheet as it has so many advantages. As a high-speed forming process, it can suppress crack, reduce springback, and improve the formability of material at room temperature. But in the process of EMF, the rebound effect caused by high velocity impact has an important effect on the flatness of the formed part. Then a spring damper system has been added under the female stop block to eliminate this effect. The results of formed shape, thickness distribution and stress and strain state are investigated by comparing with free-forming process. On the other hand, the influence of spring stiffness and damping coefficient is analysed by using of ANSYS loose-coupled method. The results shows that it helps to improve the flatness of formed parts with a spring damper system used. Beside of the changing of formed shape, the difference of stress strain state results in difference of thickness distribution. And crack happened at the bottom is supressed, and this does favour for further processing. Furthermore, the results also shows that low spring stiffness and right damping coefficient are benefit for reducing the rebound effect

Engineered Chloroplast dsRNA Silences Cytochrome p450 Monooxygenase, V‐ATPase and Chitin Synthase Genes in the Insect Gut and Disrupts Helicoverpa Armigera Larval Development and Pupation

In the past two decades, chloroplast genetic engineering has been advanced to achieve high‐level protein accumulation but not for down‐regulation of targeted genes. Therefore, in this report, lepidopteran chitin synthase (Chi), cytochrome P450 monooxygenase (P450) and V‐ATPase dsRNAs were expressed via the chloroplast genome to study RNA interference (RNAi) of target genes in intended hosts. PCR and Southern blot analysis confirmed homoplasmy and site‐specific integration of transgene cassettes into the chloroplast genomes. Northern blots and real‐time qRT‐PCR confirmed abundant processed and unprocessed dsRNA transcripts (up to 3.45 million copies of P450 dsRNAs/μg total RNA); the abundance of cleaved dsRNA was greater than the endogenous psbA transcript. Feeding of leaves expressing P450,Chi and V‐ATPase dsRNA decreased transcription of the targeted gene to almost undetectable levels in the insect midgut, likely after further processing of dsRNA in their gut. Consequently, the net weight of larvae, growth and pupation rates were significantly reduced by chloroplast‐derived dsRNAs. Taken together, successful expression of dsRNAs via the chloroplast genome for the first time opens the door to study RNA interference/processing within plastids. Most importantly, dsRNA expressed in chloroplasts can be utilized for gene inactivation to confer desired agronomic traits or for various biomedical applications, including down‐regulation of dysfunctional genes in cancer or autoimmune disorders, after oral delivery of dsRNA bioencapsulated within plant cells