SPHysics Simulation of Experimental Spillway Hydraulics

In this paper, we use the parallel open source code parallelSPHysics based on the weakly compressible Smoothed Particle Hydrodynamics (WCSPH) approach to study a spillway flow over stepped stairs. SPH is a robust mesh-free particle modelling technique and has great potential in treating the free surfaces in spillway hydraulics. A laboratory experiment is carried out for the different flow discharges and spillway step geometries. The physical model is constructed from a prototype reservoir dam in the practical field. During the experiment, flow discharge over the weir crest, free surface, velocity and pressure profiles along the spillway are measured. In the present SPH study, a straightforward push-paddle model is used to generate the steady inflow discharge in front of the weir. The parallelSPHysics model is first validated by a documented benchmark case of skimming flow over a stepped spillway. Subsequently, it is used to reproduce a laboratory experiment based on a prototype hydraulic dam project located in Qinghai Province, China. The detailed comparisons are made on the pressure profiles on the steps between the SPH results and experimental data. The energy dissipation features of the flows under different flow conditions are also discussed. It is shown that the pressure on the horizontal face of the steps demonstrates an S-shape, while on the vertical face it is negative on the upper part and positive on the lower part. The energy dissipation efficiency of the spillway could reach nearly 80%

The Milky Way's rotation curve out to 100 kpc and its constraint on the Galactic mass distribution

The rotation curve (RC) of the Milky Way out to $\sim$ 100 kpc has been constructed using $\sim$ 16,000 primary red clump giants (PRCGs) in the outer disk selected from the LSS-GAC and the SDSS-III/APOGEE survey, combined with $\sim$ 5700 halo K giants (HKGs) selected from the SDSS/SEGUE survey. To derive the RC, the PRCG sample of the warm disc population and the HKG sample of halo stellar population are respectively analyzed using a kinematical model allowing for the asymmetric drift corrections and re-analyzed using the spherical Jeans equation along with measurements of the anisotropic parameter $\beta$ currently available. The typical uncertainties of RC derived from the PRCG and HKG samples are respectively 5-7 km/s and several tens km/s. We determine a circular velocity at the solar position, $V_c (R_0)$ = 240 $\pm$ 6 km/s and an azimuthal peculiar speed of the Sun, $V_{\odot}$ = 12.1 $\pm$ 7.6 km/s, both in good agreement with the previous determinations. The newly constructed RC has a generally flat value of 240 km/s within a Galactocentric distance $r$ of 25 kpc and then decreases steadily to 150 km/s at $r$ $\sim$ 100 kpc. On top of this overall trend, the RC exhibits two prominent localized dips, one at $r$ $\sim$ 11 kpc and another at $r$ $\sim$ 19 kpc. From the newly constructed RC, combined with other constraints, we have built a parametrized mass model for the Galaxy, yielding a virial mass of the Milky Way's dark matter halo of $0.90^{+0.07}_{-0.08} \times 10^{12}$ ${\rm M}_{\odot}$ and a local dark matter density, $\rho_{\rm \odot, dm} = 0.32^{+0.02}_{-0.02}$ GeV cm$^{-3}$.Comment: MNRAS accepted, 18 pages, 15 figures, 4 table

LAMOST observations in the Kepler field. Analysis of the stellar parameters measured with the LASP based on the low-resolution spectra

All of the 14 subfields of the Kepler field have been observed at least once with the Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST, Xinglong Observatory, China) during the 2012-2014 observation seasons. There are 88,628 reduced spectra with SNR$_g$ (signal-to-noise ratio in g band) $\geq$ 6 after the first round (2012-2014) of observations for the LAMOST-Kepler project (LK-project). By adopting the upgraded version of the LAMOST Stellar Parameter pipeline (LASP), we have determined the atmospheric parameters ($T_{\rm eff}$ , $\log g$, and $\rm [Fe/H]$) and heliocentric radial velocity $v_{\rm rad}$ for 51,406 stars with 61,226 spectra. Compared with atmospheric parameters derived from both high-resolution spectroscopy and asteroseismology method for common stars in Huber et al. (2014), an external calibration of LASP atmospheric parameters was made, leading to the determination of external errors for the giants and dwarfs, respectively. Multiple spectroscopic observations for the same objects of the LK-project were used to estimate the internal uncertainties of the atmospheric parameters as a function of SNR$_g$ with the unbiased estimation method. The LASP atmospheric parameters were calibrated based on both the external and internal uncertainties for the giants and dwarfs, respectively. A general statistical analysis of the stellar parameters leads to discovery of 106 candidate metal-poor stars, 9 candidate very metal-poor stars, and 18 candidate high-velocity stars. Fitting formulae were obtained segmentally for both the calibrated atmospheric parameters of the LK-project and the KIC parameters with the common stars. The calibrated atmospheric parameters and radial velocities of the LK-project will be useful for studying stars in the Kepler field.Comment: 53 pages, 21 figures, 5 tables, Accepted for publication by ApJ

SWE-SPHysics Simulation of Dam Break Flows at South-Gate Gorges Reservoir

This paper applied a Smoothed Particle Hydrodynamics (SPH) approach to solve Shallow Water Equations (SWEs) to study practical dam-break flows. The computational program is based on the open source code SWE-SPHysics, where a Monotone Upstream-centered Scheme for Conservation Laws (MUSCL) reconstruction method is used to improve the Riemann solution with Lax-Friedrichs flux. A virtual boundary particle method is applied to treat the solid boundary. The model is first tested on two benchmark collapses of water columns with the existence of downstream obstacle. Subsequently the model is applied to forecast a prototype dam-break flood, which might occur in South-Gate Gorges Reservoir area of Qinghai Province, China. It shows that the SWE-SPH modeling approach could provide a promising simulation tool for practical dam-break flows in engineering scale

Efficacy and Safety of Ligation Combined With Sclerotherapy for Patients With Acute Esophageal Variceal Bleeding in Cirrhosis: A Meta-Analysis

Objective: To evaluate the efficacy and safety of endoscopic variceal ligation + endoscopic injection sclerotherapy (EVL+EIS) to control acute variceal bleeding (AVB).Methods: Online databases, including Web of Science, PubMed, the Cochrane Library, Chinese National Knowledge Infrastructure (CNKI), China Biology Medicine (CBM) disc, VIP, and Wanfang, were searched to identify the studies comparing the differences between EVB+EIS and EVB, EIS from the inception of the databases up to December 30, 2020. STATA 13.0 was used for the meta-analysis.Results: A total of eight studies involving 595 patients (317 patients in the EVL group and 278 patients in the EVL+EIS group) were included. The results of the meta-analysis did not reveal any statistically significant differences in the efficacy of acute bleeding control (P = 0.981), overall rebleeding (P = 0.415), variceal eradication (P = 0.960), and overall mortality (P = 0.314), but a significant difference was noted in the overall complications (P = 0.01).Conclusion: EVL is superior to the combination of EVL and EIS in safety, while no statistically significant differences were detected in efficacy. Further studies should be designed with a large sample size, multiple centers, and randomized controlled trials to assess both clinical interventions

CFD analysis and optimization of axial flow fans

The axial fan plays a vital role in the safe production of the mine, and in this paper, a mine axial flow ventilator is designed through numerical simulation to meet the demand of air exchange inside and outside of the mine, so as to maintain the oxygen supply of the mine and discharge the harmful gases. Finite element analysis of four structural factors of axial fan blade installation angle, number of blades, deflector plate, rotational speed, drawing fan wind pressure and rotational speed cloud diagram, calculation of axial power, by analyzing the distribution of the cloud diagram to design the shape of the fan blade, and derive the change rule of the wind pressure when changing the structure of the fan. By using gradient descent method to control the percentage of imported mass flow rate, the P-Q performance curve of the fan is obtained, which optimizes its aerodynamic performance, improves efficiency, and extends its service life

Robust estimation of bacterial cell count from optical density

Optical density (OD) is widely used to estimate the density of cells in liquid culture, but cannot be compared between instruments without a standardized calibration protocol and is challenging to relate to actual cell count. We address this with an interlaboratory study comparing three simple, low-cost, and highly accessible OD calibration protocols across 244 laboratories, applied to eight strains of constitutive GFP-expressing E. coli. Based on our results, we recommend calibrating OD to estimated cell count using serial dilution of silica microspheres, which produces highly precise calibration (95.5% of residuals <1.2-fold), is easily assessed for quality control, also assesses instrument effective linear range, and can be combined with fluorescence calibration to obtain units of Molecules of Equivalent Fluorescein (MEFL) per cell, allowing direct comparison and data fusion with flow cytometry measurements: in our study, fluorescence per cell measurements showed only a 1.07-fold mean difference between plate reader and flow cytometry data

Optimization of Structural and Processing Parameters for Selective Laser Melting of Porous 316L Bone Scaffolds

In the implantation of porous bone scaffolds, good mechanical properties of the scaffold are a prerequisite for the long-term functionality of the implanted scaffolds, which varies according to the structure and the forming process. In this study, the influence of the forming parameters and structure of the Selective Laser Melting (SLM) process on the mechanical properties of 316L stainless steel bone scaffolds was investigated using finite element simulation combined with experimental methods. The mechanism of the influence of the process parameters and structure on the mechanical properties of bone scaffolds was summarized using static compression finite element numerical simulations, compression experiments, hydrodynamic simulations, forming numerical simulations and SLM forming experiments. The results show that the magnitude of residual stress and the distribution of defects under different process parameters had a strong influence on the microstructure and properties of the scaffold, and the residual stress of the Body-Centered Cube (BCC) structure formed at an energy density of 41.7 J/mm3 was significantly reduced, with less surface spheroidization and fewer cracks on the melt pool surface. The smallest grain size of 321 nm was obtained at an energy density of 77.4 J/mm3, while in terms of mechanical properties, the optimization of the structure resulted in an 8.3% increase in yield strength and a reduction in stress concentration. The predictions of stress, deformation, and forming quality during construction with different process parameters, achieved using finite element analysis, are basically in agreement with the experimental results, indicating that the best process parameters for forming BCC structural supports were determined by using finite element simulation combined with experiments; moreover, the distribution and evolution of residual stresses and defects under different process parameters for constructing BCC structures were obtained

Soluble monomeric human programmed cell death-ligand 1 inhibits the functions of activated T cells

IntroductionThe presence of soluble human programmed cell death-ligand 1 (shPD-L1) in the blood of patients with cancer has been reported to be negatively correlated with disease prognosis. However, little information exists about the mechanisms underlying high levels of shPD-L1 for promoting disease progression.MethodsIn this study, we first analyzed the correlations between shPD-L1 and apoptosis of T cells in patients with cancer, then tested the effect of shPD-L1 on T-cell functions and the production of regulatory T cells.ResultsWe found that the apoptosis of human peripheral PD-1+CD4+ T cells was significantly elevated in patients with cancer compared with healthy donors and was positively correlated with circulating PD-L1 levels in patients with cancer. In vitro, monomeric shPD-L1 significantly inhibited the proliferation, cytokine secretion, and cancer cell-killing activity of peripheral blood mononuclear cells (PBMCs) activated by either agonist antibodies or HATac (high-affinity T cell activation core)-NYE (NY-ESO-1 antigen). It also promoted CD4+ T cells to express forkhead family transcription factor 3 (FoxP3) for the conversion of induced T regulatory cells, which was more significant than that mediated by soluble human PD-L1 fusion protein (shPD-L1-Fc).DiscussionThese results confirm that soluble PD-L1 could be a candidate for inhibiting the functions of activated T cells, promoting peripheral tolerance to tumor cells, and implicating in system tumor immune escape in addition to the tumor microenvironment. This is an important mechanism explaining the negative correlation between peripheral blood PD-L1 levels and cancer prognosis. Therefore, understanding the roles of hPD-L1 in peripheral blood will be helpful for the development of precision immunotherapy programs in treating various tumors

Crack Propagation Behavior of a Ni-Based Single-Crystal Superalloy during In Situ SEM Tensile Test at 1000 °C

An in situ scanning electron microscope (SEM) tensile test for Ni-based single-crystal superalloy was carried out at 1000 °C. The stress displacement was obtained, and the yield strength and tensile strength of the superalloy were 699 MPa and 826 MPa, respectively. The crack propagation process, consisting of Model I crack and crystallographic shearing crack, was determined. More interestingly, the crack propagation path and rate affected by eutectics was directly observed and counted. Results show that the coalescence of the primary crack and second microcrack at the interface of a γ/γ′ matrix and eutectics would make the crack propagation rate increase from 0.3 μm/s to 0.4 μm/s. On the other hand, crack deflection decreased the rate to 0.05 μm/s. Moreover, movement of dislocations in front of the crack was also analyzed to explain the different crack propagation behavior in the superalloy