The requirements of cooling and weight reduction for lithium-ion battery packages in electric vehicles are increasingly important. In this paper, a liquid cooling heat dissipation structure is designed and optimized. First of all, the effects of tube diameter, spacing, thickness and layout of the cooling plate on the heat dissipation of the battery package are investigated by using computational fluid dynamics. Afterwards, based on the optimal results of the single factor analysis, an orthogonal table with four factors and three levels are constructed to perform a single-objective optimization, where the minimization of the maximum temperature is the optimization object. Meanwhile, an experiment is carried out to verify the accuracy of the simulation model. In order to further reduce the mass of the cooling plate, a multi-objective optimization is performed, where the minimization of the maximum temperature and the mass are the optimization objects. The maximum temperature is increased by 10.9% in the multi-objective optimization when compared with that in the single objective optimization. However, the mass of the cooling plate in the multi-objective optimization can drop by 82.4%.
Biocides can effectively kill bacteria; however, whether the dead bacterial cells left on the surface influence the later growth of biofilm is unknown. In this study, we have cultured Pseudomonas aeruginosa (PAO1) biofilm on their dead siblings and have investigated their evolution by using magnetic force modulation atomic force microscopy (MF-AFM). The time dependence of the biofilm thickness indicates that the deposited dead siblings can slow down the growth of PAO1 biofilm. The biofilm growing on dead bacteria layers is softer in comparison with those upon alive siblings, as reflected by the static elastic modulus ( E) and dynamic stiffness ( k) scaled to the disturbing frequency ( f) as k = k f, where k is the scaling factor and γ is the power-law exponent. We reveal that the smaller population instead of the variation of extracellular polymeric substances (EPS) within the biofilm upon the dead siblings is responsible for the softer biofilm. The present study provides a better understanding of the biofilm formation, thus, making it significant for designing antimicrobial medical materials and antifouling coatings.
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