No abstract

Abstract. Non-uniform thickness section section is considered one of the most effective approaches to reduce automotive part weight. Reduction in term of mass and size result in less fuel consumption and greenhouse gases. Thickness is the most significant parameter to formability, therefore forming a section with non-uniform thickness becomes a great challenge. Improper process and incorrect decision may lead to severe defect and one of the main concerns is the springback. This study will focus on springback behaviour of non-uniform thickness AA6061 strip with complex profile using Taguchi Method. Profile projector (PC 3000) is used to measure the spring back and two-line technique is applied to measure angles (after loading) between two lines. Three parameters (i.e. annealing temperature, thickness ratio and bend angle) are studied, and results determine that the most significant parameter is bend angle, followed by thickness ratio, and then by the annealing temperature of the specimen during bending process.

Recently, Lim & Then (2022; Endang Species Res 48:43-50) used an environmental DNA (eDNA) PCR-based method for detecting the presence of an endangered species of freshwater stingray, Fluvitrygon kittipongi (Dasyatidae), in the Pahang River basin, east Peninsular Malaysia. For that, they designed a species-specific pair of primers to amplify a 196 base pair (bp) fragment of the cytochrome c oxidase I (COI) gene. Lim & Then (2022) reported positive detection of this species along an upstream stretch of the Pahang River during the inter-monsoon and the southwest monsoon seasons, with the PCR-amplified eDNA sequences identical to the reference COI sequences of F. kittipongi collected from the Perak River basin, west Peninsular Malaysia. Here, we argue that such positive results are likely the consequence of a DNA contamination because the 196 bp COI fragments of F. kittipongi from the Pahang River and the Perak River differ from each other by 4 nucleotide substitutions. The source of contamination in Lim & Then (2022) could have been the Perak samples the authors handled to develop the primers. We also briefly discuss the potential impact of the presumed co-occurrence of freshwater stingrays of the genus Fluvitrygon in the Pahang River on the specificity of the F. kittipongi-specific primers designed by Lim & Then (2022).