Investigation on the Changing Characteristics of Flow-Induced Noise in a Centrifugal Pump

Centrifugal pumps are widely used in engineering for a variety of applications.A known drawback of these devices is the high-level noise generated during operations,which can affect their stability and adversely influence the entire working environment.By combining the Powell vortex sound theory,numerical simulations and experimental measurements,this research explores the trends of variation and the corresponding underlying mechanisms for the flow-induced noise at various locations and under different operating conditions.It is shown that the total sound source intensity(TSSI)and total sound pressure level(TSPL)in the impeller,in the region between the inlet to the outlet and along the circumferential extension of the volute,are much higher than those at pump inlet and outlet.Additionally,under various rotational speeds with the design flow rate(Condition 1),the TSSI and TSPL at pump inlet and outlet are higher than those obtained with the opening of the valve kept unchanged(Condition 2);vice versa when these two parameters are evaluated at various locations in the impeller and the volute under the Condition 2,they exceed the equivalent values obtained for the other Condition 1.

Transformation Characteristics and Microstructure of Rail under Low Stress during Continuous Cooling

To obtain a better understanding the thermal stress of a rail,the thermal simulator was used to measure the expansion curves of different stresses loaded during the continuous cooling process of U75V rail.The transformation plasticity model was established.The experimental results show that stress can accelerate the transformation process of pearlite.While the same cooling rate is accelerated with the increase of stress,the transformation process of pearlite is accelerated,and the proportion of plastic strain transformation in total strain increases.At the same stress,the process of transformation of pearlite decreases with the increase in cooling rate,and the proportion of transformation plastic strain in total strain decreases.When considering the transformation plasticity,the axial residual stress is more consistent with the actual working condition,the accuracy of the transformation plasticity model is higher;during the continuous cooling process,and the loading stress has a significant influence on the structure.When the stress increases,the orientation of the pearlite lamellae becomes disordered,the pearlite lamellae are bent,the lamellae spacing is no longer uniform,and the hardness is improved.

The Next-Hop Node Selection Based GPSR in Vehicular Ad Hoc Networks

Vehicular Ad hoc Networks (VANETs) which is a special form of Mobile Ad hoc Networks (MANETs) has promising application prospects in the future. Due to the rapid changing of topology structure, how to find a route which can guarantee Quality of Service (QoS) is an important issue in VANETs. This paper presents an improved Greedy Perimeter Stateless Routing (GPSR) protocol based on our proposed next-hop node selection mechanism. Firstly, we define the link reliability in two cases which take the movement direction angle between two vehicles into consideration. Then we propose a next-hop node selection mechanism based on a weighted function which consists of link reliability between the sender node and next-hop candidate node, distance between next-hop candidate node and the destination, movement direction angle of next-hop candidate node. At last, an improved GPSR protocol is proposed based on the next-hop node selection mechanism. Simulation results are presented to evaluate the performance of the improved GPSR protocol, which shows that the performance including packet delivery ratio and average end-to-end delay of the proposed protocol is better in some situations.

联合检测肿瘤标志物与炎症指标对结直肠癌的诊断价值

目的探讨癌胚抗原(CEA)、糖类抗原19-9(CA19-9)、中性粒细胞/淋巴细胞比值(NLR)、血小板/淋巴细胞比值(PLR)等指标在结直肠癌诊断及预后中的价值。方法收集2016年1月-2018年11月广州中医药大学第一附属医院行结直肠癌手术治疗的158例患者的临床资料,以及从癌症基因组图谱数据库(TCGA)匹配出的316例结直肠癌患者的临床资料。分析不同临床病理特征与患者术前CEA、CA19-9的假阴性率及高低不同分组的NLR、PLR值的关系。根据分析结果确定联合检测指标并探讨联合检测对肿瘤远处脏器转移的预测作用。结果在结直肠癌的诊断中,单用肿瘤标志物时假阴性率较高,且CA19-9假阴性率(72.78%)高于CEA假阴性率(49.58%);随着肿瘤进展,肿瘤浸润较深、存在淋巴结转移、远处转移及分期较晚患者CEA假阳性率降低(P<0.05);CA19-9及PLR的升高提示结直肠癌患者存在远处脏器转移可能,且女性患者与高PLR值相关;CEA与NLR联合检测可能具有较好的预测结直肠癌远处脏器转移的作用(AUC=0.881,P=0.000)。结论联合检测肿瘤标志物及炎症指标在提高结直肠癌诊断率、预测结直肠癌根治术后患者TNM分期及指导术后患者复查频率上具有一定的价值。

Polymorphisms in HIF-1a gene are not associated with diabetic retinopathy in China

BACKGROUND It has been reported that vascular endothelial growth factor(VEGF)is a susceptibility gene for both type 2 diabetes mellitus(T2DM)and diabetic retinopathy(DR).In response to hypoxia,VEGF mRNA levels are increased,which is mainly mediated by the binding of hypoxia-inducible factor-1(HIF-1)and hypoxia response element upstream of the transcriptional start site of VEGF.Therefore,HIF-1a is supposed to be involved in pathology of DR.AIM To investigate whether the polymorphisms in HIF-1a gene are associated with DR.METHODS Two hundred and ninety-nine type 2 diabetic patients(128 males and 171 females)and 144 healthy volunteers were recruited.Mean age was 56.04±21.05 years.According to the results of fundus fluorescein angiography and examination of ophthalmoscopy,patients were divided into two groups,DNR group(diabetes without retinopathy)and DR group(diabetes with retinopathy).There are 150 cases in DNR group and 149 cases in DR group.Two single nucleotide polymorphisms(SNP)of the HIF-1a gene were tested using matrix-assisted laser desorption/Ionization time of flight mass spectrometry.The frequency of genotypes and alleles,and odds ratio were measured.RESULTS The mean age of the cases with diabetes was 55.84±3.66 years,the mean age of the cases with DR was 55.97±4.66 years and that of controls was 56.32±4.70 years.Two variations were found in 76 patients.Rs11549465 is the change of C-T base,rs11549467 is the change of G-A base.The rs11549467 G/A genotype was 5.33%in diabetes and 6.04%in DR patients,respectively.The rs11549465 C/T genotype was 10%and 12.75%in patients with diabetes and DR.The rs11549467 A allele frequencies and rs11549465 T frequencies was similar to that of controls.Paired SNP linkage disequilibrium analysis indicated that rs11549467 was in linkage disequilibrium with rs11549465.Haplotype association analysis denoted that the haplotype association exhibited similar distribution in the patients compared to the normal controls.CONCLUSION This study suggests that there is no relationship between the genetic variations of HIF1a and diabetes or DR.

构建“1421模式”提升课程育人实效——以物理化学课程群建设为例

安庆师范大学省级物理化学教学团队,立足地方化学化工支柱产业需求,把握学校办学定位,依托国家级一流专业建设点和省级工程中心平台,以一个教研室基层党支部为核心引领,四个课堂互融互通,优化迭代线上线下两方面课程资源,按照课程内容的逻辑顺序和时空维度,持续建设一个特色物理化学课程群。通过历年实践所构建的“1421”理工类专业课程建设模式,为课程思政的持续深入开展提供了坚实基础,课程育人效果显著,可为高校理工类专业课开展课程思政提供一定借鉴。

A real-time AI-assisted seismic monitoring system based on new nodal stations with 4G telemetry and its application in the Yangbi M_(S) 6.4 aftershock monitoring in southwest China

A rapidly deployable dense seismic monitoring system which is capable of transmitting acquired data in real time and analyzing data automatically is crucial in seismic hazard mitigation after a major earthquake.However,it is rather difficult for current seismic nodal stations to transmit data in real time for an extended period of time,and it usually takes a great amount of time to process the acquired data manually.To monitor earthquakes in real time flexibly,we develop a mobile integrated seismic monitoring system consisting of newly developed nodal units with 4G telemetry and a real-time AI-assisted automatic data processing workflow.The integrated system is convenient for deployment and has been successfully applied in monitoring the aftershocks of the Yangbi M_(S) 6.4 earthquake occurred on May 21,2021 in Yangbi County,Dali,Yunnan in southwest China.The acquired seismic data are transmitted almost in real time through the 4G cellular network,and then processed automat-ically for event detection,positioning,magnitude calculation and source mechanism inversion.From tens of seconds to a couple of minutes at most,the final seismic attributes can be presented remotely to the end users through the integrated system.From May 27 to June 17,the real-time system has detected and located 7905 aftershocks in the Yangbi area before the internal batteries exhausted,far more than the catalog provided by China Earthquake Networks Center using the regional permanent stations.The initial application of this inte-grated real-time monitoring system is promising,and we anticipate the advent of a new era for Real-time Intelligent Array Seismology(RIAS),for better monitoring and understanding the subsurface dynamic pro-cesses caused by Earth's internal forces as well as anthropogenic activities.

Research on cutting vibration characteristics of face-milling involute gear

Traditional machining methods, such as gear hobbing, gear shaping and gear milling, etc, are commonly used for cutting machining of gear tooth profile, which cannot meet huge machining demand of gears to a certain extent. This article proposes to utilize a face-milling machining method in involute gear machining, which can be used to reduce production cost effectively. Cutting vibration generated during cutting machining has a direct effect on the machining accuracy and machined surface quality of workpiece. Therefore, it is desiderated to perform in-depth research regarding this issue. ADAMS software was used to establish a rigid-flexible coupling virtual prototyping model of face-milling gear milling system and a cutting vibration system model. Cutting vibration analysis was performed for face-milling gear by adopting quick sine frequency sweep method, so that the frequency response characteristics of workpiece in three directions X, Y and Z and space were acquired. The research results will provide reference and theoretical foundation for actual application of face-milling gear machining technology.

Numerical Analysis of Flow-Induced Vibration and Noise Generation in a Variable Cross-Section Channel

Flow channels with a variable cross-section are important components of piping system and are widely used in variousfields of engineering.Using afinite element method and modal analysis theory,flow-induced noise,mode shapes,and structure-borne noise in such systems are investigated in this study.The results demonstrate that the maximum displacement and equivalent stress are located in the part with variable cross-sectional area.The aver-age excitation force on theflow channel wall increases with theflow velocity.The maximum excitation force occurs in the range of 0–20 Hz,and then it decreases gradually in the range of 20–1000 Hz.Additionally,as theflow velocity rises from 1 to 3 m/s,the overall sound pressure level associated with theflow-induced noise grows from 49.37 to 66.37 dB.Similarly,the overall sound pressure level associated with the structure-borne noise rises from 40.27 to 72.20 dB.When theflow velocity is increased,the increment of the structure-borne noise is higher than that of theflow-induced noise.

Numerical Simulation of 3D Flow Field and Flow-Induced Noise Characteristics in a T-Shaped Reducing Tee Junction

The so-called T-shaped reducing tees are typically used to divide,change and control(to a certain extent)the flow direction in pipe networks.In this study,the Ffowcs Williams–Hawkings(FW-H)equation and the Large Eddy Simulation(LES)methods are used to simulate the flow-induced noise related to T-shaped reducing tees under different inlet flow velocities and for different pipe diameter ratios.The results show that the maximum flow velocity,average flow velocity,and vorticity in the branch pipe increase gradually as the related diameter decreases.Strong vorticity and secondary flows are also observed in the branch pipe,and the associated violent pressure fluctuations are found to be the main sources of flow-induced noise.In particular,as the pipe diameter ratio decreases from 1 to 0.45,the Total Sound Pressure Level(TSPL)increases by 6.8,6.26,and 7.43 dB for values of the inlet flow velocity of 1,2,and 3 m/s,respectively.The distribution characteristics of the flow-induced noise in the frequency domain follow similar trends for different pipe diameter ratios.

Dynamic kinetic stereodivergent transformations of propargylic ammonium salts via dual nickel and copper catalysis

The dynamic kinetic asymmetric transformation of racemic propargylic ammonium salts with prochiral aldimine esters through a stereodivergent propargylation is catalyzed by dual nickel and copper catalysis.Thus,a diverse range of optically activeα-quaternary amino esters were produced via C-N bond cleavage with high reaction efficiency and stereoselectivity(up to>99%ee).By selection of the appropriate pair-wise combination of catalyst configurational isomers,all four possible stereoisomers of the corresponding propargylation products are obtained in high yields with excellent regio-,diastereo-,and enantioselectiv-ities.

Risk factors related to significant hepatic inflammation in patients with acute drug-induced liver injury

Background and aims:Currently,research on biopsy-proven acute drug-induced liver injury(DILI)remains limited.This study aimed to identify clinical characteristics and risk factors for significant hepatic inflammation in patients with acute DILI.Methods:An ambispective cohort study was conducted on biopsy-proven acute DILI patients admitted to our hospital from 2012 to 2018.Using the Scheuer scoring system,patients were categorized into G0-2 or G3-4 groups and followed up for 12 months after first admission.Clinical characteristics and outcomes were retrieved from medical records.Results:The median age of the 157 enrolled patients(65.6%female)was 40.4(interquartile range(IQR),31.9-49.1)years.The median latency and length of hospitalization were 30.0(IQR,5.0-60.0)and 18.0(IQR,12.0-26.0)days.The proportions of patients in the G0-2 and G3-4 groups were 54.8%and 45.2%,respectively.Logistic regression analysis revealed that females(odds ratio(OR):2.623,95%confidence interval(CI):1.169-5.887,p=0.019),higher body mass index(OR:1.168,95%CI:1.029-1.325,p=0.016),higher total bilirubin(OR:1.004,95%CI:1.000-1.007,p=0.047),and lower prothrombin activity(OR:0.976,95%CI:0,957-0.995,p=0.013)were associated with significant hepatic inflammation.The predominance of the hepatocellular injury pattern(60.5%)at admission transformed into a predominance of the cholestatic pattern(60.5%)at discharge.During follow-up,23 patients(14.6%)developed chronic DILI,with nine patients(5.7%)progressing to cirrhosis.Moreover,15 female patients(9.6%)developed autoimmunity(3cases in the G0-2 group vs 12 cases in the G3-4 group,p<0.05).Conclusion:Acute DILI patients with high-risk factors were more likely to develop significant hepatic inflammation,and females with significant inflammation were at a higher risk of developing autoimmunity during follow-up.

Metabolic syndrome is associated with significant hepatic fibrosis and steatosis in patients with nonalcoholic steatohepatitis

Background and aims:Nonalcoholic steatohepatitis(NASH),an inflammatory form of non-alcoholic fatty liver disease,can progress to advanced liver fibrosis,cirrhosis,and liver cancer.Metabolic syndrome(MetS)parallels the prevalence of non-alcoholic fatty liver disease/NASH and increases patients’risk of advanced liver disease.This study aimed to determine whether MetS was associated with the histological progression of NASH.Methods:Patients with liver biopsy-proven NASH were retrospectively screened and categorized into two groups for each histological feature:with(<2 points)or without(2 points)significant hepatic steatosis/inflammation/fibrosis.Multivariable logistic regression was used to explore the association between MetS and histological features.Results:In total,386 patients with a median age of 33.0 years were enrolled;among them,35.2%were female,and 41.2%had MetS.The proportion of significant hepatic fibrosis and steatosis in those with MetS was significantly higher than in those without MetS(p<0.05).Multivariable logistic regression analyses showed that MetS remained significantly associated with significant hepatic fibrosis(adjusted odds ratio:1.852,95%confidence interval:1.042-3.292,p=0.036),and severe hepatic steatosis(adjusted odds ratio:2.008,95%confidence interval:1.030-3.914,p=0.041).Conclusion:MetS was associated with significant hepatic fibrosis and steatosis in patients with NASH.Our results suggest that NASH patients with MetS should be closely monitored and given targeted intervention and treatment,which may help to prevent disease progression and mitigate the growing burden of NASH.

Confluence of asymmetric catalysis and electrosynthesis in sustainable chemical transformations

Electrosynthesis has gained widespread recognition for its extraordinary ability to precisely control the redox process.This outstanding capability enables the direct conversion of non-functionalized substrates into reactive intermediates by utilizing easily accessible starting materials, eliminating the need for preliminary functionalization procedures and allowing for unconventional bond activations.

Asymmetric Electrochemical Arylation in the Formal Synthesis of(+)-Amurensinine

Asymmetric electrochemical synthesis has emerged as an attractive and sustainable alternative for the distinctive activation of bond connections in the preparation of diverse enantiomerically enriched targets,including natural products and pharmaceutical agents.Herein,we describe the chiral Lewis acid-catalyzed enantioselective electrochemical anodic coupling reaction as a key step in the presented formal synthesis of isopavine alkaloids.

Surface active-site engineering in hierarchical PtNi nanocatalysts for efficient triiodide reduction reaction

Hierarchical Pt-alloys enriched with active sites are highly desirable for efficient catalysis,but their syntheses generally need time-consuming and elaborate annealing treatment at high temperature.We herein report a surface active-site engineering strategy for constructing the hierarchical PtNi nanocatalysts with an atomic Pt-skin layer(PtNi@Pt-SL)towards efficient triiodide reduction reaction(TRR)via an acid-dealloying approach.The facile acid-dealloying process promotes the formation of surface Pt active sites on the hierarchical Pt-alloys,and thus results in good catalytic performance towards TRR.Theoretical calculation reveals that the enhanced catalytic property stems from the moderate energy barriers for iodide atoms on the surface Pt active-sites.The surface active-site engineering strategy paves a new way for the design of active and durable electrocatalysts.

Organic Nanoprobes for Fluorescence and ^19F Magnetic Resonance DuaI-Modality Imaging

Multimodal imaging techniques have been demonstrated to be greatly advantageous in achieving accurate diagnosis and gained increasing attention in recent decades. Herein, we present a new strategy to integrate the complementary modalities of I9F magnetic resonance imaging （19F MRI） and fluorescence imaging （FI） into a polymer nanoprobe composed of hydrophobic fluorescent organic core and hydrophilic fluorinated polymer shell. The alkyne-terminated fluorinated copolymer （Pn） of 2,2,2-trifluoroethyl acrylate （TFEA） and poly（ethylene glycol） methyl ether acrylate （PEGA） was first prepared vie atom transfer radical polymerization （ATRP）. The PEGA plays an important role in both improving ^19F signal and modulating the hydrophilicity of Pn. The alkynyl tail in Pn is readily conjugated with azide modified tetra-phenylethylene （TPE） through click chemistry to form azo polymer （TPE-azo-Pn）. The core-shell nanoprobes （TPE-P3N） with an average particle size of 57.2±8.8 nm are obtained via self-assembly with ultrasonication in aqueous solution. These nanoprobes demonstrate high water stability, good biocompatibility, strong fluorescence and good ^19F MRI performance, which present great potentials for simultaneous fluorescence imaging and ^19F-MR imaging.

Construction of voxel-based Portunus haanii phantom and its absorbed fractions and specific absorbed fractions calculation based on Monte Carlo simulations

Objective:To build the database of the absorbed fractions(AFs)and specific absorbed fractions(SAFs),in order to accurately assess the internal radiation dose in non-human biota.Methods:A voxel-based Portunus haanii phantom was established based on the computed tomography(CT)images.A set of AFs and SAFs were calculated with Monte Carlo toolkit Geant4 for the emission of monoenergetic photons and electrons with energies ranging from 10 keV to 5 MeV.Results:The mass of the voxel-based Portunus haanii phantom(392.2 g)was in agreement with the actual mass(389.2 g),indicating the reliability of the phantom.The calculated AFs and SAFs,based on the voxel-based Portunus haanii phantom,provided precise and reliable data for conducting internal radiation dose calculations specifically tailored to the Chinese Red Swimming Crab(Portunus haanii).The results indicated that the self-AFs and self-SAFs were affected by both the radiation energy and the mass of the source/target organ.Moreover,the AFs and SAFs for cross irradiation,were not only dependent on the energy and the mass of the target organ,but also on the relative position of the source and target organs.Conclusion:These results serve as a valuable resource for accurately evaluating the internal radiation exposure of this species.