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New omega vortex identification method

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Science China(Physics,Mechanics & Astronomy) 2016年第8期59卷 56-64页

作者： ChaoQun Liu yiqian wang Yong Yang ZhiWei Duan Department of Mathematics University of Texas at Arlington Department of Aerodynamics Nanjing University of Aeronautics and Astronautics School of Aerospace Engineering Tsinghua University

A new vortex identification criterion called W-method is proposed based on the ideas that vorticity overtakes deformation in *** comparison with other vortex identification methods like Q-criterion and λ_2-method is conducted and the advantages of the new method can be summarized as follows:(1) the method is able to capture vortex well and very easy to perform;(2) the physical meaning of W is clear while the interpretations of iso-surface values of Q and λ_2 chosen to visualize vortices are obscure;(3)being different from Q and λ_2 iso-surface visualization which requires wildly various thresholds to capture the vortex structure properly, W is pretty universal and does not need much adjustment in different cases and the iso-surfaces of W=0.52 can always capture the vortices properly in all the cases at different time steps, which we investigated;(4) both strong and weak vortices can be captured well simultaneously while improper Q and λ_2 threshold may lead to strong vortex capture while weak vortices are lost or weak vortices are captured but strong vortices are smeared;(5) W=0.52 is a quantity to approximately define the vortex boundary. Note that, to calculate W, the length and velocity must be used in the non-dimensional form. From our direct numerical simulation, it is found that the vorticity direction is very different from the vortex rotation direction in general 3-D vortical flow,the Helmholtz velocity decomposition is reviewed and vorticity is proposed to be further decomposed to vortical vorticity and non-vortical vorticity.

关键词： vorticity vortex vortex identification turbulence

DNS Study on Volume Vorticity Increase in Boundary Layer Transition

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Transactions of Nanjing University of Aeronautics and Astronautics 2016年第3期33卷 252-259页

作者： wang yiqian Tang Jie Liu Chaoqun Zhao Ning College of Aerospace Engineering Nanjing University of Aeronautics and Astronautics Department of Mathematics University of Texas at Arlington

The issue whether transition from laminar flow to turbulent flow on a flat plate should be characterized as a vorticity redistribution process or a vorticity increasing process is investigated by a high-order direct numerical simulation on a flat plate boundary *** local vorticity can either increase or decrease due to tilting and stretching of vortex filaments according to the vorticity transport equation while the total vorticity cannot be changed in a boundary layer flow in conforming to the Fppl theorem of total vorticity *** seemingly contradictory problem can be well resolved by the introduction of a new term:volume vorticity of a vorticity tube,defined as vorticity flux timed by the vorticity tube *** has been shown that,although vorticity flux must keep conserved,the total volume vorticity is significantly increased during boundary layer transition according to our direct numerical simulation(DNS)computation,which directly results from the lengthening(stretching and tilting)of vortex ***,the flow transition is a process with appreciable increase of volume vorticity,and cannot be only viewed as a vorticity redistribution process.

关键词： volume vorticity vorticity redistribution vorticity increase transition boundary layer

Effect of NOx and RH on the secondary organic aerosol formation from toluene photooxidation

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Journal of Environmental Sciences 2022年第4期34卷 1-9页

作者： Shijie Liu Xiaodi Liu yiqian wang Si Zhang Can Wu Wei Du Gehui wang Key Lab of Geographic Information Science of the Ministry of Education School of Geographic SciencesEast China Normal UniversityShanghai 210062China Institute of Eco-Chongming 3663 North Zhongshan RoadShanghai 200062China

The secondary organic aerosol(SOA)formation mechanism and physicochemical properties can highly be influenced by relative humidity(RH)and NOx *** this study,we performed a laboratory investigation of the SOA formation from toluene/OH photooxidation system in the presence or absence of NOx in dry and wet *** chemical composition of toluene-derived SOA was measured using Aerodyne high-resolution timeof-flight aerosol mass spectrometer(HR-ToF-AMS).It was found that the mass concentration of toluene decreased with increasing RH and NOx ***,the change of SOA chemistry composition(f_(44),O/C)with increased RH was not consistent in the condition with or without *** light absorption and mass absorption coefficient(MAC)of the toluene-derived SOA only increased with RH in the presence of *** contrast,MAC is invariant with RH in the absence of ***-ToF-AMS results showed that,in the presence of NOx,the increased nitro-aromatic compounds and N/C ratio concurrently caused the increase of SOA light absorption and O/C in wet conditions,*** relative intensity of CHON and CHOxN family to the total nitrogen-containing organic compounds(NOCs)increased with the increasing RH,and be the major components of NOCs in wet *** work revealed a synergy effect of NOx and RH on SOA formation from toluene photooxidation.

关键词： Toluene Photooxidation Relative humidity NOx Optical property

艾司氯胺酮联合右美托咪定麻醉前处理对腹腔镜胆囊切除术治疗胆囊结石患者术后睡眠质量和情绪状态的影响

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实用肝脏病杂志 2025年第2期28卷 310-313页

作者：张莹萱王艺倩解成兰姚程亮王军徐州医科大学附属淮安医院麻醉科江苏省淮安市223002

目的探讨应用艾司氯胺酮与右美托咪定联合预处理对腹腔镜胆囊切除术(LC)治疗的胆囊结石患者术后睡眠质量和情绪的影响。方法2022年11月~2024年4月我院收治的113例胆囊结石患者,均接受LC术治疗。在麻醉前,被随机分为D组(n=37)、ED组(n=38... 详细信息

目的探讨应用艾司氯胺酮与右美托咪定联合预处理对腹腔镜胆囊切除术(LC)治疗的胆囊结石患者术后睡眠质量和情绪的影响。方法2022年11月~2024年4月我院收治的113例胆囊结石患者,均接受LC术治疗。在麻醉前,被随机分为D组(n=37)、ED组(n=38)和C组(n=38),分别给予右美托咪定、右美托咪定联合艾司氯胺酮和生理盐水静脉泵注。常规行麻醉诱导和维持。采用Athens失眠量表(AIS)和匹兹堡睡眠指数量表(PSQI)评估睡眠质量,采用焦虑自评量表(SAS)和抑郁自评量表(SDS)评估情绪状态,采用疼痛数字评定量表(NRS)和Ramsay镇静量表评估镇痛和镇静效果。结果在术后第1天(POD1)和POD3时,ED组AIS评分分别为(8.4±1.3)分和(6.8±1.4)分,显著低于D组【分别为(8.7±1.1)分和(6.9±1.7)分,P<0.05】或C组【分别为(9.7±1.1)分和(8.5±1.1)分,P<0.05】,PSQI评分分别为(9.1±1.3)分和(7.7±1.5)分,显著低于D组【分别为(9.2±1.5)分和(7.9±1.4)分,P<0.05】或C组【分别为(10.9±2.3)分和(8.9±1.8)分,P<0.05】;在POD1时,ED组和D组SAS和SDS评分均显著低于C组,且ED组显著低于D组,差异具有统计学意义(P<0.05);在拔管时、术后24 h和术后72 h,ED组和D组NRS评分均显著低于C组,且ED组显著低于D组,差异具有统计学意义(P<0.05);ED组镇痛泵药物消耗量显著少于D组或C组(P<0.05)。结论麻醉前给予艾司氯胺酮联合右美托咪定预处理可以减轻LC术后患者疼痛,缓解抑郁焦虑情绪,提高术后睡眠质量。

关键词：胆囊结石腹腔镜胆囊切除术艾司氯胺酮右美托咪定麻醉睡眠质量情绪

MMP-9及炎症因子在急性缺血性脑卒中患者溶栓后出血转化中的意义

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中国实用神经疾病杂志 2025年第2期28卷 191-196页

作者：张少康王一茜刘银芳张晓曼新乡医学院附属郑州市第一人民医院河南郑州450000 新乡医学院河南新乡453003 平顶山市第一人民医院河南平顶山467000

目的探索MMP-9及IL-6、TNF-α在急性缺血性脑卒中(AIS)患者静脉溶栓治疗后出血转化(HT)中的意义。方法收集2021-01—2022-12在郑州市第一人民医院神经内科住院的AIS并给予静脉溶栓治疗的患者122例,依据患者静脉溶栓结局有无发生HT分为H... 详细信息

目的探索MMP-9及IL-6、TNF-α在急性缺血性脑卒中(AIS)患者静脉溶栓治疗后出血转化(HT)中的意义。方法收集2021-01—2022-12在郑州市第一人民医院神经内科住院的AIS并给予静脉溶栓治疗的患者122例,依据患者静脉溶栓结局有无发生HT分为HT组与非HT组,检测入院第1、3、7天时患者血清MMP-9水平,入院第1天IL-6、TNF-α水平,分析相关临床资料在AIS静脉溶栓治疗后HT中的意义。结果单因素分析中,2组间溶栓后非颅内出血、治疗前及溶栓后NIHSS评分、FBG、NEUT%、Hcy、LDL-C、MMP-9、IL-6、TNF-α差异均有统计学意义(P<0.05)。Logistic回归分析发现,溶栓后非颅内出血及血清MMP-9、IL-6、TNF-α、Hcy、LDL-C等与AIS静脉溶栓治疗后HT的发生独立相关(P<0.05),其中溶栓后非颅内出血与血清MMP-9、IL-6、TNF-α是危险因素,Hcy、LDL-C水平为阻碍因素。ROC曲线分析显示MMP-9、TNF-α、IL-6及其联合对HT的发生均有预测价值,以MMP-9最为可靠,预测AIS静脉溶栓治疗后HT发生的AUC为0.907,界值109.25μg/L,灵敏度93.8%,特异性76.4%。结论血清MMP-9及IL-6、TNF-α单独与联合检测均可预测AIS患者静脉溶栓后HT的发生。

关键词：缺血性脑卒中静脉溶栓出血转化基质金属蛋白酶-9 白细胞介素-6 肿瘤坏死因子-α

On the tip sharpness of riblets for turbulent drag reduction

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Acta Mechanica Sinica 2022年第4期38卷 39-55,I0001页

作者： yiqian wang Yi Huang Song Fu School of Mathematical Sciences Soochow UniversitySuzhou 215006China School of Aerospace Engineering Tsinghua UniversityBeijing 100084China

It is commonly known that riblets with sharper tip generally have better turbulent drag reduction capacity,which,however,poses great challenges for manufacturing and makes the riblets vulnerable to tip *** this study,we show that a scalloped riblet which is not as sharp in the tip as corresponding triangular riblet with same height-width ratio,nevertheless has a larger protrusion height,a quantity solely depending on the riblet shape and calculated through a boundary element algorithm in this study,and thus a higher projected drag reduction *** addition,it is found that,when subjected to tip rounding,this scalloped riblet performs better in terms of protrusion height than corresponding parabolic riblet,which indicates stronger resilience to riblet tip *** the class of scalloped riblets,designed by smoothly connecting two third-order polynomials and thus the tip sharpness and valley curvature can be well defined,it is revealed that two mechanisms,one for the valley curvature at the viscous limit and one for the tip sharpness at infinite deep limit,determine the protrusion height,and thus the projected drag reduction *** numerical simulations are then carried out to investigate controlled boundary layer transition with the scalloped riblet of width s+=20 and 5+=60.A 7.8%drag reduction in the turbulent region is found for the smaller riblet with a preferable transition delay,while for the larger riblet transition is promoted and drag is increased in the turbulent *** is also found that the area fraction of high drag region around the riblet tips is basically the same for the two ***,even higher drag is found around the tip region for the smaller drag-reducing *** the other hand,a much smaller drag coefficient is found in the valley of the smaller riblet,which results in the reduction of turbulent *** is thus inferred that the issue of sharp riblet tip,that hard to manufacture and deteriorate substantially

关键词： Riblet Turbulent drag reduction Tip sharpness Protrusion height Direct numerical simulation

Intermittent Behaviors in Coupled Piecewise Expanding Map Lattices

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Analysis in Theory and Applications 2021年第4期37卷 481-519页

作者： Tiexiang Li Wen-Wei Lin yiqian wang Shing-Tung Yau Department of Mathematics Southeast UniveristyNanjingJiangsu 211189China Nanjing Center for Applied Mathematics NanjingJiangsu 211135China Department of Mathematics National Chiao Tung UniversityHsinchu300Taiwan Department of Mathematics Nanjing UniversityNanjingJiangsu 210093China Department of Mathematics Harvard UniversityBostonUSA

In this paper,we propose a new method to study intermittent behaviors of coupled piecewise-expanding map *** show that the successive transition between ordered and disordered phases occurs for almost every orbit when the coupling is *** is,lim inf n→∞∑1≤i,j≤m|x_(i)(n)−x_(j)(n)|=0,lim sup n→∞∑1≤i,j≤m|x_(i)(n)−x_(j)(n)|≥c_(0)>0,where xi(n)correspond to the coordinates of m nodes at the iterative step ***,when the uncoupled system is generated by the tent map and the lattice consists of two nodes,we prove a phase transition occurs between synchronization and intermittent *** is,limn→∞|x_(1)(n)−x_(2)(n)|=0 for c−1/21/4,where 0≤c≤1 is the coupling.

关键词： Synchronization pseudo synchronization phase transition Coupled map Lattices piecewise expanding map

Consideration of Postgraduate Training under the Cross Field of Medical Information and Engineering

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计算机教育 2021年第12期 106-114页

作者： Yi Ding yiqian wang Zhen Qin Yang Zhao Mingsheng Cao Zhiguang Qin the School of Information and Software Engineering University of Electronic Science and Technology of ChinaChengdu610054China

The slogan of“Combination of medicine and engineering”proposed in“Made in China 2025”has aroused great attention to higher engineering ***,it is a difficult problem and challenge for schools and educators to effectively adapt to the economic and social development,train new medical and engineering talents,and explore and cultivate new subject growth *** order to deal with engineering change and a new round of scientific and technological revolution,facing the challenge of new engineering *** paper will combine the reality and characteristics of colleges and universities,analyze the problems existing in the current medical engineering cross-graduate training,and put forward countermeasures and suggestions to promote the progress and development of science and technology in colleges and universities.

关键词： medical and engineering cross field postgraduate training plans countermeasures and suggestions

基于SRM法的直剪作用下不同随机节理倾角岩体尺寸效应研究

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水利水电技术(中英文) 2025年第1期56卷 217-230页

作者：牙兰开刘远明陈庆芝王忠星张策王义乾田茂亮贵州大学土木工程学院贵州贵阳550025 中铁开发投资集团有限公司云南昆明650200

【目的】旨在揭示不同倾角区间的随机节理对岩体破坏特征、抗剪强度和剪切模量尺寸效应的影响规律。【方法】利用PFC 2D离散元软件的SRM技术,结合分形理论和Monte Carlo方法,对不同尺寸、内嵌随机节理的类岩体进行数值模拟直剪试验。【... 详细信息

【目的】旨在揭示不同倾角区间的随机节理对岩体破坏特征、抗剪强度和剪切模量尺寸效应的影响规律。【方法】利用PFC 2D离散元软件的SRM技术,结合分形理论和Monte Carlo方法,对不同尺寸、内嵌随机节理的类岩体进行数值模拟直剪试验。【结果】结果表明:(1)岩体抗剪强度随内嵌随机节理倾角区间的增大均呈现“S”型非线性特征,且最小值多出现在15°~30°区间,最大值均在60°~75°区间。(2)不同尺寸的内嵌随机节理倾角区间变化对岩体破坏影响效果相似。低倾角区间出现明显的优势破坏面和次优势破坏面,随着倾角区间增大,其应力集中发生向节理中部转移,两优势破坏面的优势发生转换。(3)随机节理倾角区间变化显著影响岩体抗剪强度和剪切模量的尺寸效应,且对岩体抗剪强度尺寸效应的影响大于对剪切模量尺寸效应的影响。【结论】研究了相同尺寸条件下内嵌随机节理倾角区间变化对节理岩体抗剪强度及破坏特征的影响和不同尺寸条件下内嵌随机节理倾角区间变化对节理岩体抗剪强度和剪切模量尺寸效应的影响,为岩体力学性质的预测和工程应用提供了重要的参考价值。

关键词： SRM法 PFC 随机节理直剪试验尺寸效应抗剪强度力学性能