q. zhang

In this manuscript, the vortex generated by the main frequency excitation of the shedding vortex at various attack angles is investigated by employing the synthetic jet control technique. We also analyzed the impact of the vortex structure on the fled flow around the wing and the spectral characteristics corresponding to the vortex. The dominant frequency and harmonic frequency corresponding to the wave rule of the shedding vortex at various attack angles without the absence of a synthetic jet are selected as the synthetic jet excitation frequency. The results indicate that under the excitation of fixed frequency synthetic jet, the shape of the shedding vortex in the flow field turns correspondingly. Compared with the flow field without jet excitation, it is found that the field with the jet at most attack angles is stable in 2S (Single) mode, and the flow field at a small attack angle is stable in a chaotic state. The angle of attack with a chaotic state is delayed by adding a jet, which makes the curves and corresponding spectral characteristics more orderly. At a defined attack angle, the combined frequency synthetic jet will cause the lift coefficient to fluctuate regularly. At this time, the multiple small-scale vortex structures lead to lift reduction.

To investigate the computer tomography (CT) features of 2019 coronavirus disease (COVID-19)-related pneumonia and its value for identifying severity.

Seventy-three patients with COVID-19 were divided into severe and nonsevere groups. CT signs were divided into two states: presence and absence; involvement range was divided into four grades; and affected lobes were divided into two states: ≥3 lobes and < 3 lobes; laboratory indices were divided into two states: normal and abnormal; co-occurrence of signs was divided into three states: ground-glass opacity (GGO) plus consolidation, only GGO, or only consolidation. The numbers of patients were respectively recorded. Statistical analysis was performed through the χ2 test, followed by multivariate logistic regression analysis.

Some indicators differed, including pure GGO (p<0.001), GGO with focal consolidation (p=0.009), patchy consolidation (p=0.004), sheeted consolidation (p<0.001), fibrotic appearance (p=0.020), involvement grade (p<0.001), affected lobes (p=0.027), pleural effusion (p=0.001), subpleural line (p=0.015), crazy paving signs (p<0.001), halo signs (p=0.020), thickened bronchial walls (p<0.001), air bronchi signs (p=0.003), lesions in mid/inner zone (p<0.001), liver function (p=0.044), interleukin-6 (p<0.001), c-reactive protein (p<0.001), lymphocyte count (p<0.001), and age (p=0.036). Pure GGO (OR:30.711, HR:1.292~729.882, p=0.034) and involvement grade (OR:0.017, HR:0.001~0.342, p=0.008) were independent risk factors.

On admission, CT signs of COVID-19-related pneumonia were diverse but characteristic, and some CT findings may be potential warning factors for severity, while a lack of GGO and extensive pneumonia may be independent risk factors.