科创中国

在CFD离散误差和不确定度估计问题中,为研究计算得到的观测精度对仿真计算结果的影响,消除GCI离散不确定度估计法中当观测精度大于格式精度时出现的不合理的小不确定度,提出了1种改进的CFD离散不确定度估计方法,即用加权平均的数值解代替细网格数值解来估计离散误差及不确定度.针对低雷诺数二维非轴对称圆柱绕流模型进行数值计算,划分5套网格,用二阶迎风格式计算圆柱绕流的阻力系数和升力系数,分别给出了GCI和改进方法的离散不确定度估计结果,并与文献参考值进行比较,结果表明改进的方法对离散不确定估计要优于GCI方法,且置信度更高.

We validated a radioimmunoassay-based method quantifying fecal glucocorticoid metabolites (FGMs) from captive male and female Richardson's ground squirrels Urocitellus richardsonii. Blood samples were drawn to explore the correlation between plasma cortisol and FGM concentrations. We also injected groups of squirrels with normal saline (CTL; control), adre- nocorticotropic hormone (ACTH; stimulating adrenal activity), or dexamethasone (DEX; suppressing adrenal activity). Potential correlations between stress and behaviour were explored through quantification of fecal pellet production and the intervention necessary to elicit defecation, as well as the behaviour of subjects in the context of handling. Changes in plasma cortisol concen- tration between capture (baseline), and following handling (stress-induced) were also quantified for free-living squirrels. While glucocorticoid concentrations recovered from feces during our captive-animal study were not well correlated with plasma eortisol concentrations, and uncorrelated with defecation or behaviour, FGM concentrations did reflect the activation of the hypothalamic- pituitary-adrenal (HPA) axis. FGM concentrations increased significantly during initial captivity, but declined to baseline level as individuals acclimated to the novel environment. Injection of subjects with ACTH increased FGMs above baseline, confirming activation of the HPA axis. Plasma cortisol concentrations increased significantly with induced stress, indicating that capture and handling activated the glucocorticoid stress response even among previously handled, free-living subjects. Our findings validate a non-invasive tool that will afford new insight into the physiological processes underlying social, reproductive and antipredator behaviour of Richardson's ground squirrels [Current Zoology 60 (5): 591-601, 2014 ].