Parallelization strategies for resolved simulations of fluid-structure-particle interactions

Fluid-structure-particle interactions in three spatial dimensions happen in many environmental and engineering flows.This paper presents the parallel algorithms for the hybrid diffuse and sharp interface immersed boundary(IB)method developed in our previous work.For the moving structure modeled using the sharp interface IB method,a recursive box method is developed for efficiently classifying the background grid nodes.For the particles modeled using the diffuse interface IB method,a‘master-slave’approach is adopted.For the particle-particle interaction(PPI)and particle-structure interaction(PSI),a fast algorithm for classifying the active and inactive Lagrangian points,which discretize the particle surface,is developed for the‘dry’contact approach.The results show that the proposed recursive box method can reduce the classifying time from 52seconds to 0.3 seconds.Acceptable parallel efficiency is obtained for cases with different particle concentrations.Furthermore,the lubrication model is utilized when a particle approaches a wall,enabling an accurate simulation of the rebounding phenomena in the benchmark particle-wall collision problem.At last,the capability of the proposed computational framework is demonstrated by simulating particle-laden turbulent channel flows with rough walls.

Achieving Total Enteroscopy by Consecutive Bidirectional Doubleballoon Enteroscopy Procedures

Objective:To investigate the feasibility and safety of achieving total enteroscopy by consecutive bidirectional double-balloon enteroscopy(DBE)procedures.Methods:The demographic data,indication,initial insertion route,examination time for each insertion and the entire procedure,total enteroscopy rate,diagnostic yield and adverse events of patients who attempted to achieve total enteroscopy by consecutive bidirectional DBE procedures from January 2014 to December 2019 were retrospectively analyzed.

On the capability of the curvilinear immersed boundary method in predicting near-wall turbulence of turbulent channel flows

The immersed boundary method has been widely used for simulating flows over complex geometries.However,its accuracy in predicting the statistics of near-wall turbulence has not been fully tested.In this work,we evaluate the capability of the curvilinear immersed boundary(CURVIB)method in predicting near-wall velocity and pressure fluctuations in turbulent channel flows.Simulation results show that quantities including the time-averaged streamwise velocity,the rms(root-mean-square)of velocity fluctuations,the rms of vorticity fluctuations,the shear stresses,and the correlation coefficients of u'and v"computed from the CURVIB simulations are in good agreement with those from the body-fitted simulations.More importantly,it is found that the time-averaged pressure,the rms and wavenumber-frequency spectra of pressure fluctuations computed using the CURVIB method agree well with the body-fitted results.

Kinetic analysis of γ-glutamyltransferase reaction process for measuring activity via an integration strategy at low concentrations of γ-glutamyl p-nitroaniline

At 0.12 mmol/L γ-glutamyl p-nitroaniline(GGPNA),an improved integrated method was developed for kinetic analysis of γ-glutamyltransferase(GGT) reaction process and the integration with the classical initial rate method to measure serum GGT.For the improved integrated method,an integrated rate equation,which used the predictor variable of reaction time and considered inhibitions by both GGPNA and products,was nonlinearly fit to GGT reaction processes.For the integration strategy,classical initial rates were estimated when GGPNA consumption percentages were below 50%;otherwise,maximal reaction rates of GGT were estimated by the improved integrated method and converted into initial rates according to the differential rate equation at 0.11 mmol/L GGPNA.The inte-gration strategy was validated using optimized GGT kinetic parameters and 10-s intervals to record reaction curves within 8.0 min.By the integration strategy,there was a linear response from 0.9 to 32.0 U/L GGT,coefficients of variation were below 3.5%for GGT from 8.0 to 32.0 U/L(n=5) ,and GGT activities in clinical sera responded linearly to their classical initial rates at 2.00 mmol/L GGPNA with an expected slope.Therefore,the integration strategy was successful in measuring GGT at 0.12 mmol/L GGPNA.

磁珠固定化结核分枝杆菌二氢叶酸还原酶及其表征

比较Ni^(2+)-NTA磁珠和羧基磁珠固定结核分枝杆菌二氢叶酸还原酶(Mycobacteriumtuberculosis dihydrofolate reductase,Mt DHFR),探索适合小分子配体混合物库筛选的Mt DHFR固定化方法。重组表达带6×His标签Mt DHFR,纯化后表征酶学性质,比较用Ni^(2+)-NTA磁珠和羧基磁珠固定化时相应固定化容量、保留活性、稳定性及对抑制剂响应。结果表明,Ni^(2+)-NTA磁珠对Mt DHFR固定化容量为(93±12)mg/g磁珠(n=3),但酶比活保留不超过32%,Ni^(2+)明显抑制酶活性,EDTA与Ni^(2+)呈协同抑制效应,Fe^(3+)无显著干扰。羧基磁珠活化固定Mt DHFR的容量(8.6±0.6) mg/g磁珠(n=3),固定化酶比活保留(87±4)%(n=3)。在含50 mmol/L KCl的100 mmol/L HEPES (pH 7.0)中,游离和固定化Mt DHFR在0℃保存16 h活性都无显著改变,但在25℃保存16 h,游离酶活性下降近60%而羧基磁珠固定化Mt DHFR活性下降仅35%。甲氨喋呤对游离Mt DHFR和固定化Mt DHFR的IC50无显著差异(P>0.05)。综上,Ni^(2+)-NTA磁珠不适合固定化Mt DHFR;羧基磁珠固定化Mt DHFR能保留活性、热稳定性及对抑制剂的响应,该固定化方法有望用于快速筛选其配体混合物库。

Characteristics of Spatiotemporal Distribution of Sea Surface Wind along the East Coast of Guangdong Province

We analyzed the frequency distribution characteristics of wind speeds occurring at different offshore sites within a range of 0-200 km based on the sea surface wind data captured via buoys and oil platforms located along the east coast of Guangdong Province. The results of the analysis showed that average wind speed measured for each station reached a maximum in winter while minima occurred in summer, corresponding to obvious seasonal variation, and average wind speed increased with offshore distance. The prevailing wind direction at the nearshore site is the east-erly wind, and the frequency of winds within 6-10 m s^-1 is considerable with that of winds at 〉 10 m s^-1. With the in-crease of the offshore distance, the winds were less affected by the land, and the prevailing wind direction gradually became northerly winds, predominately those at 〉 10 m s^-1. For areas of shorter offshore distance （〈 100 km）, sur-face wind speeds fundamentally conformed to a two-parameter Weibull distribution, but there was a significant dif-ference between wind speed probability distributions and the Weibull distribution in areas more than 100 km off-shore. The mean wind speeds and wind speed standard deviations increased with the offshore distance, indicating that with the increase of the wind speed, the pulsation of the winds increased obviously, resulting in an increase in the ra-tio of the mean wind speed to the standard deviation of wind speed. When the ratio was large, the skewness became negative. When a relatively great degree of dispersion was noted between the observed skewness and the skewness corresponding to the theoretical Weibull curve, the wind speed probability distribution could not be adequately de-scribed by a Weibull distribution. This study provides a basis for the verification of the adaptability of Weibull distri-bution in different sea areas.

基于扭曲价格的要素替代测度与工业节能分析——来自我国制造业行业数据的证据

立足于节能减排的宏观目标与微观主体的要素配置需求,本文通过构建包含技术效率损失与要素价格扭曲的确定性前沿成本函数及份额方程,度量了制造业行业相对效率水平及要素价格扭曲程度,并在此基础上估算了不同行业的规模报酬特征与要素替代弹性。结论表明:行业间相对技术效率水平与要素替代性差异明显,资本密集行业与劳动密集行业要素配置效率优化存在反向特征,借助于要素替代与规模提升的节能路径只在部分行业适用,最后,给出了相关节能政策建议。