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BACKGROUND: Vietnam possesses a vast diversity of rice landraces due to its geographical situation, latitudinal range, and a variety of ecosystems. This genetic diversity constitutes a highly valuable resource at a time when the highest rice production areas in the low-lying Mekong and Red River Deltas are enduring increasing threats from climate changes, particularly in rainfall and temperature patterns. RESULTS: We analysed 672 Vietnamese rice genomes, 616 newly sequenced, that encompass the range of rice varieties grown in the diverse ecosystems found throughout Vietnam. We described four Japonica and five Indica subpopulations within Vietnam likely adapted to the region of origin. We compared the population structure and genetic diversity of these Vietnamese rice genomes to the 3,000 genomes of Asian cultivated rice. The named Indica-5 (I5) subpopulation was expanded in Vietnam and contained lowland Indica accessions, which had with very low shared ancestry with accessions from any other subpopulation and were previously overlooked as admixtures. We scored phenotypic measurements for nineteen traits and identified 453 unique genotype-phenotype significant associations comprising twenty-one QTLs (quantitative trait loci). The strongest associations were observed for grain size traits, while weaker associations were observed for a range of characteristics, including panicle length, heading date and leaf width. CONCLUSIONS: Our results highlight differences in genome composition and trait associations among traditional Vietnamese rice accessions, which are likely the product of adaption to multiple environmental conditions and regional preferences in a very diverse country. Our results highlighted traits and their associated genomic regions that are a potential source of novel loci and alleles to breed a new generation of sustainable and resilient rice.

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Variable displacement vane-type oil pumps represent one of the most innovative pump types for industrial applications, especially for engine lubrication systems. This article deals with a mathematical modeling method for theoretical performance investigation of a typical variable displacement vane-type oil pump. This theoretical model is based on the pump geometric design and dynamic analyses. It can be considered as a generation step for a deeper understanding of the pump operation as well as for effectively implementing the pump control mechanisms to satisfy the urgent demands of engine lubrication systems. The developed theoretical pump model is finally illustrated by numerical simulations.

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Variable-displacement vane-type oil pumps represent one of the most innovative pump types for industrial applications, especially for engine lubrication systems. The aim of this paper is to develop a complete and accurate mathematical model for a typical variable-displacement vane-type oil pump to investigate its working performance. First, the detailed theoretical model was built on the basis of pump geometric design and dynamic analyses. Next, numerical simulations with the constructed model and experiments on the actual pump system were carried out to analyse the main power loss factors in order to develop the complete model for high modelling accuracy. The estimated pump performance using the complete pump model was finally verified by numerical simulations in comparison with practical tests.

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