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Large-eddy simulation (LES) of the Navier–Stokes equations is carried out to investigate the supersonic turbulent boundary layer (STBL) developing over a flat plate at free-stream Mach number M ∞ =2.0 and Reynolds number R e δ ≈ 13 500. The seventh-order weighted essentially non-oscillatory (WENO-7) scheme is adopted to ensure calculation accuracy. To demonstrate the credibility of the proposed improvements, a posteriori test is conducted. Other LES-like methods are also adopted for comparison. The validation results show that WENO-LES can provide credible predictions when grid resolution is sufficient. Thus, current LES results can be regarded as a reliable database for further analysis. The distributions of flow topologies and turbulent statistics are obtained after time average operation. A preliminary conclusion can be drawn that the position y + ≈ 14 in buffer layer may be the appropriate interface for Reynolds-averaged Navier–Stokes (RANS) and LES computations of LES-like methods in STBL. Diverse length scales in LES-like methods are calculated based on high-fidelity flow fields. On this basis, a blending function is added to the original von Karman length formula. A dissipation-adaptive length scale is proposed for the scale-adaptive simulation (SAS) method. A comparison of the original SAS and delayed-DES (DDES) methods reveals that the improved method exhibits grid-independent characteristics of RANS/LES interface. Furthermore, the coherent vortical structures and flow visualization of the a posteriori test indicate that the improved method has a satisfactory ability to promote the generation of small-scale structures and to capture turbulent fluctuations. [ABSTRACT FROM AUTHOR]

The aim of this study was to explore the correlation between psychological resilience and social support and anxiety in obstetric nurses and to provide theoretical basis for improving the mental health of obstetric nurses.

To study the complications of ultrasound-guided radiofrequency ablation (RFA) in chronic kidney disease (CKD) patients undergoing renal replacement therapy with secondary hyperparathyroidism (SHPT). This retrospective study reviewed the clinical data, including general information, examination results, treatment times, time interval, and postoperative complications, of 103 SHPT patients who received ultrasound-guided RFA treatment from July 2017 to January 2021. Of 103 patients, 52 required two sessions of RFA within a month. The incidence of recurrent laryngeal nerve injury at the second treatment was significantly higher than that at the first treatment (first session vs. second session, 5.77% vs. 21.15%; p =.021). Of all the enrolled 103 patients, 27 suffered complications after the first session of RFA. When we separated patients into complications group and non-complication group, we detected more ablated nodules in the complications group (Z = −2.222; p =.0026). Subgroup analysis further showed that the patients in the severe hypocalcemia group were younger (p =.005), had more ablated nodules (p =.003) and higher blood phosphorus (p =.012) and alkaline phosphatase (ALP) levels (p =.002). Univariate analysis showed that age, serum phosphorus, ALP, and number of ablated nodules were associated with a higher risk of severe hypocalcemia after the first session of RFA. An interval of more than 1 month between two treatments may help to avoid recurrent laryngeal nerve injury. Age, serum phosphorus, ALP, and number of ablated nodules were associated with a higher risk of severe hypocalcemia after the first session of RFA. [ABSTRACT FROM AUTHOR]

Sand moulds are used in the casting process. However, after heating, the binder in the sand loses the binding properties, and the most part of the foundry sand has to be discarded from the process. The waste foundry sand after the regeneration can be recycled, and reclamation can reduce the production cost and lower waste emissions. The objective of this work was to investigate the possibility of reusing the animal glue binder waste foundry sand from the study of three regeneration methods. Studies with the waste foundry sand and reclaimed sand were performed in order to compare the results obtained with raw sand. The characterization of the samples was performed by scanning electron microscopy and energy dispersive spectroscopy. Results show that the waste sand was regenerated by mechanical regeneration, thermal regeneration and wet reclamation, respectively. The reclaimed sands have a better performance than the waste foundry sand, and are similar to raw sand. Further, the wet regeneration method is the best one among the three methods.

In this paper, the interfacial energy of various inorganic salts was calculated using the first principle. Finally, NaCl and Na2SO4 were determined as the core materials. A high-strength composite salt core was prepared by optimizing the distribution ratio of the salt core components. The microstructure of the salt core fracture was observed and characterized by SEM and EDS, and the strengthening mechanism of the salt core after the composite was analyzed. The results demonstrated that the strength of the composite salt core was significantly improved compared with the single salt. The bending strength of the salt core reached 24 MPa when the pouring temperature was 800 °C and the molar ratio of NaCl to Na2SO4 was 7:3. Cracks were first generated in the dendrite zone and extended to the surface of the salt core when the salt core was subjected to an external force. After compounding, the structure of the salt core strengthening zone was more complex, the crystal grains were significantly refined, and herringbone patterns appeared. The composite salt blocks are distributed in the strengthening zone and play a leading role in improving the strength of the salt core. [ABSTRACT FROM AUTHOR]