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| 1 | A Liutex based definition and identification of vortex core center lines显示文摘Six core issues for vortex definition and identification concern with (1) the absolute strength,(2) the relative strength,(3) the rotational axis,(4) the vortex core center,(5) the vortex core size, and (6) the vortex boundary (Liu C. 2019). However, most of the currently popular vortex identification methods, including the Q criterion, the criterion and the Acj criterion etc., are Eulerian local region-type vortex identification criteria and can only approximately identify the vortex boundary by somewhat arbitrary threshold. On the other hand, the existing Eulerian local line-type methods, which seek to extract line-type features such as vortex core line, are not entirely satisfactory since most of these methods are based on vorticity or pressure minimum that will fail in many cases. The key issue is the lack of a reasonable mathematical definition for vortex core center. To address this issue, a Liutex (previously named Rortex) based definition of vortex core center is proposed in this paper. The vortex core center, also called vortex rotation axis line here, is defined as a line where the Liutex magnitude gradient vector is aligned with the Liutex vector, which mathematically implies that the cross product of the Liutex magnitude gradient vector and the Liutex vector on the line is equal to zero. Based on this definition, a novel three-step method for extracting vortex rotation axis lines is presented. Two test cases, namely the Burgers vortex and hairpin vortices, are examined to justify the proposed method. The results demonstrate that the proposed method can successfully identify vortex rotation axis lines without any user-specified threshold, so that the proposed method is very straightforward, robust and efficient. | Yi-sheng Gao Jian-ming Liu Yi-fei Yu Chaoqun Liu | 2019 | Journal of Hydrodynamics2019，31，3： | 19 |
| 2 | A novel method for singularity analysis of the 6-SPS parallel mechanisms显示文摘Singularity analysis is a basic problem of parallel mechanism, and this problem cannot be avoided in both workspace and motion planning. How to express the singularity locus in an analytical form is the research emphasis for many researchers for a long time. This paper presents a new method for the singularity analysis of the 6-SPS parallel mechanism. The rotation matrix is described by quaternion, and both the rotation matrix and the coordinate vectors have been expanded to four-dimensional forms. Through analyzing the coupling relationship between the position variables and the orientation variables, utilizing properties of the quaternion, eight equivalent equations can be obtained. A new kind of Jacobian matrix is derived from those equations, and the analytical expression of the singularity locus is obtained by calculating the determinant of the new Jacobian matrix. The singularity analysis of parallel mechanisms, whose moving platform actuated by 6 links and the vertices of both the base and the moving platforms has been placed on a circle respectively, can be solved by this analytical expression. | CHENG ShiLi WU HongTao WANG ChaoQun YAO Yu ZHU JianYing | 2011 | Science China(Technological Sciences)2011，54，5： | 15 |
| 3 | Mathematical foundation of Liutex theory显示文摘Liutex is a mathematical definition of vortex,which is called the third generation of vortex definition and identification.This paper introduces the mathematical foundation of the Liutex theoretical system including differences in definition and operations between tensor/vector and matrix.The right version of velocity gradient tensor matrix is given to correct the old version which has been widely distributed by many mathematics and fluid dynamics textbooks.A unique velocity gradient principal matrix is provided.The mathematical foundation for Liutex definition is given.The coordinate rotation(Q-and P-rotation)for principal coordinate system and principal matrix is derived,which is the key issue of the new fluid kinematics.The divergence of velocity gradient tensor is given in different forms which may be beneficial in developing new governing equations for fluid dynamics. | Chaoqun Liu Yifei Yu | 2022 | Journal of Hydrodynamics2022，34，6： | 4 |
| 4 | A single observer location method under the scatter signals position disturbance situation:the constraint total least square method显示文摘A target position can be estimated using position information from scattered signals in the nonline-of-sight propagation environment in a single observer location system.There is always an error in the final estimated result of the position obtained using scatter signals because measurement noise is inevitable.To reduce the total error of the system,we propose a method of converting the problem of optimizing location into a one of solving the extremes of the constraints.And the problem of how to solve the extremes of the constraints is converted into an unconstrained problem by using the constrained total least squares(CTLS) method.Finally,the Newton iteration method is used to obtain the optimized solution.Simulation results also verify the capability of this method. | YANG TianChi YU ChaoQun2~ WANG TianPeng1 ~ JIN Liang1 YU ChaoQun WANG TianPeng JIN Liang | 2011 | Science China(Information Sciences)2011，54，1： | 3 |
| 5 | Stretching and shearing contamination analysis for Liutex and other vortex identification methods显示文摘The newly developed vortex-identification method,Liutex,has provided a new systematic description of the local fluid rotation,which includes scalar,vector,and tensor forms.However,the advantages of Liutex over the other widely used vortexidentification methods such as Q,Δ,λ2,andλci have not been realized.These traditional methods count on shearing and stretching as a part of vortex strength.But,in the real flow,shearing and stretching do not contribute to fluid rotation.In this paper,the decomposition of the velocity gradient tensor is conducted in the Principal Coordinate for uniqueness.Then the contamination effects of stretching and shearing of the traditional methods are investigated and compared with the Liutex method in terms of mathematical analysis and numerical calculations.The results show that the Liutex method is the only method that is not affected by either stretching or shear,as it represents only the local fluid rigid rotation.These results provide supporting evidence that Liutex is the superior method over others. | Pushpa Shrestha Charles Nottage Yifei Yu Oscar Alvarez Chaoqun Liu | 2021 | Advances in Aerodynamics2021，3，1： | 3 |
| 6 | Liutex based new fluid kinematics显示文摘The traditional Cauchy-Stokes(C-S)decomposition states that the velocity gradient tensor can be decomposed into a symmetric tensor and an anti-symmetric tensor,namely the strain-rate tensor and the vorticity tensor.However,there are two problems with the C-S decomposition.One is that the anti-symmetric(vorticity)tensor cannot represent the fluid rotation or vortex.Another is that the symmetric(strain-rate)tensor cannot distinguish the stretching/compression and shear.Since vorticity cannot distinguish between the non-rotational shear and the rigid rotation,vorticity has been decomposed into a rigid rotation part called“Liutex”and an anti-symmetric shear in our previous work.A Liutex-based principal coordinate system has been proposed,and the corresponding velocity gradient tensor decomposition,called the principal decomposition,is presented in this principal coordinate system,which results in:(1)a Liutex tensor that represents rigid rotation,(2)a tensor that represents pure shear and(3)a tensor that represents stretching/compression.However,each point has its own principal coordinate system,which implies that the principal decomposition is performed in different principal coordinate systems,not the original(global)coordinate system.To address this issue,the principal decomposition in the original coordinate system is derived in this paper,and,therefore,provides a new kinematic approach to study the local rigid rotation,pure shear,and stretching/compression.The principal decomposition is unique,Galilean invariant and has clear physical meaning.The new velocity gradient tensor decomposition could become a foundation for new fluid kinematics. | Chaoqun Liu Yifei Yu Yi-sheng Gao | 2022 | Journal of Hydrodynamics2022，34，3： | 3 |
| 7 | Principal coordinates and principal velocity gradient tensor decomposition显示文摘Helmholtz velocity decomposition and Cauchy-Stokes tensor decomposition have been widely accepted as the foundation of fluid kinematics for a long time.However,there are some problems with these decompositions which cannot be ignored.Firstly,Cauchy-Stokes decomposition itself is not Galilean invariant which means under different coordinates,the stretching(compression)and deformation are quite different.Another problem is that the anti-symmetric part of the velocity gradient tensor is not the proper quantity to represent fluid rotation.To show these two drawbacks,two counterexamples are given in this paper.Then“principal coordinate”and“principal decomposition”are introduced to solve the problems of Helmholtz decomposition.An easy way is given to find the Principal decomposition which has the property of Galilean invariance. | Yifei Yu Pushpa Shrestha Charles Nottage Chaoqun Liu | 2020 | Journal of Hydrodynamics2020，32，3： | 3 |
| 8 | Correlation analysis among vorticity,Q method and Liutex显示文摘Influenced by the fact that vorticity represents rotation for rigid body,people believe this idea also works for fluid flow.However,the vortex predictions by vorticity do not match experimental results,which drove scientists to look for more appropriate methods to identify vortex.All vortex identification methods can be categorized into three generations.The vorticity-based method is classified as the first generation.Methods relying on eigenvalues of velocity gradient tensor are considered as the second generation.People still believe vorticity is vortex since vorticity theory looks correct in mathematics,but all other methods are only scalars and unable to indicate the swirl direction.Recently,a new vortex identification method called Liutex is innovated.It is regarded as the third-generation method,not only overcoming all previous methods’drawbacks but also having a clear physical meaning.The direction of Liutex represents the swirl axis of rotation,and its strength is equal to twice the angular speed.In this paper,we did a correlation analysis between vorticity,Q,λ_(ci),λ_(2)methods and Liutex based on a direct numerical simulation(DNS)case of boundary layer transition.The results show that the correlation between vorticity and Liutex is very small or even negative in strong shear regions,which demonstrates that using vorticity to detect vortex lacks scientific foundation and vorticity is not appropriate to represent vortex.The correlation analysis also shows that the second generation is contaminated too by shear and thus is not accurate to identify the vortex structure. | Yifei Yu Pushpa Shrestha Oscar Alvarez Charles Nottage Chaoqun Liu | 2020 | Journal of Hydrodynamics2020，32，6： | 2 |
| 9 | Preclinical Profile and Characterization of the Hepatitis C Virus NS3 Protease Inhibitor Asunaprevir (BMS-650032)显示文摘 | Fiona McPhee Amy K. Sheaffer Jacques Friborg Dennis Hernandez Paul Falk Guangzhi Zhai Steven Levine Susan Chaniewski Fei Yu Diana Barry Chaoqun Chen Min S. Lee Kathy Mosure Li-Qiang Sun Michael Sinz Nicholas A. Meanwell Richard J. Colonno Jay Knipe Paul S | 2012 | Antimicrobial Agents and Chemotherapy2012，，10： | 2 |
| 10 | The Karyotypes, C-banding Patterns and AgNORs of Epinephelus malabaricus显示文摘The chromosome specimens of Epinephelus malabaricus (Bloch & Schneider, 1801) are obtained from metaphase of kindney cell by vivi-injection of PHA and culture of colchicines, hypatoic-air drying technique, and then by studying their Giemsa stain, C-bands and AgNORs. The results are as follows: (1)E. malabaricus has a diploid chromosome number of 48 and its karyotype formula is 48t, NF=48, sex chromosome is not found. (2) There is a pair of chromosomes with secondary constriction near the centromere of chromosome t24. (3) 1~4 nucleoli appear in the nucleus of interphase, 55% nuclei has 1 nucleolus and only 2% for 4 nucleoli. (4) AgNORs appear in the chromosome t24 of 50% metaphase, sometimes in the chromosome t5, but not in other chromosomes. (5) The AgNORs polymorphisms are individually specific, 1~4 pairs of the number, and the frequency of 4 AgNORs are lowest. (6) The secondary constrictions and positive C-bands are coincident, close to the centromere of the chromosome, and mass constrictive heterochromatins appear in that region. (7) All the centromeres of chromosomes are darkly stained C-bands, and the whole arm of chromosome t24 and its centromere are same positive C-bands. (8) The evolutive regulation of the karyotype and the developing mechanism of AgNORs and C-bands are discussed. | 邹记兴 Hu Chaoqun Xiang Wenzhou YU Qixing Zhou Fei | 2004 | High Technology Letters2004，10，2： | 2 |
| 11 | Three-Dimensional Finite Element Numerical Simulation and Physical Experiment for Magnetism-Stress Detecting in Oil Casing显示文摘The casing damage has been a big problem in oilfield production. The current detection methods mostly are used after casing damage, which is not very effective. With the rapid development of China's offshore oil industry, the number of offshore oil wells is becoming larger and larger. Because the cost of offshore oil well is very high, the casing damage will cause huge economic losses. What's more, it can also bring serious pollution to marine environment. So the effective methods of detecting casing damage are required badly. The accumulation of stress is the main reason for the casing damage. Magnetic anisotropy technique based on counter magnetostriction effect can detect the stress of casing in real time and help us to find out the hidden dangers in time. It is essential for us to prevent the casing damage from occurring. However, such technique is still in the development stage. Previous studies mostly got the relationship between stress and magnetic signals by physical experiment, and the study of physical mechanism in relative magnetic permeability connecting the stress and magnetic signals is rarely reported. The present paper uses the ANSYS to do the three-dimensional finite element numerical simulation to study how the relative magnetic permeability works for the oil casing model. We find that the quantitative relationship between the stress' s variation and magnetic induction intensity's variation is: Δδ =K* ΔB, K = 8.04×109, which is proved correct by physical experiment. | MENG Fanshun ZHANG Jie YANG Chaoqun YU Weizhe CHEN Yuxi | 2015 | Journal of Ocean University of China2015，14，4： | 2 |
| 12 | A letter for objective Liutex显示文摘Vortex structures,detected by the existing popular vortex identification methods,of the same case are generally different if the results are measured by different observers,who are moving with different coordinate systems.These coordinate systems can be inertial or non-inertial.Galilean invariance can solve the moving observer problems in different inertial coordinate systems.A variable is invariant under Galilean transformation is called Galilean invariant.Galilean invariant vortex identification methods can provide invariant vortex structures based on different inertial observers.However,for some situations,the observers are non-inertial,e.g.,the observer is sitting on an aircraft which is accelerating or rotating.In such a situation,it requires to use an objective method.Objectivity represents a property that one variable is not observer-dependent(the observer’s motion can be either inertial or non-inertial).A strategy based on a zero-vorticity(measured in inertial frame)reference point is proposed in this letter to find the objective vortex structure.Liutex is chosen as the vortex indicator and two numerical examples are used to test the proposed strategy.The results show that the strategy is effective. | Yifei Yu Yi-qian Wang Chaoqun Liu | 2022 | Journal of Hydrodynamics2022，34，5： | 2 |
| 13 | Genomic and Phenotypic Diversity of Carbapenemase-Producing Enterobacteriaceae Isolates from Bacteremia in China: A Multicenter Epidemiological, Microbiological, and Genetic Study显示文摘Carbapenemase-producing Enterobacteriaceae(CPE) isolates are recognized as one of the most severe threats to public health. However, the population structure and genetic characteristics of CPE isolates among bloodstream infections(BSIs) are largely unknown. To address this knowledge gap, in this study,we included patients with clinically significant BSIs due to Enterobacterales isolates, recruited from 26 sentinel hospitals in China(2014–2015). CPE isolates were microbiologically and genomically characterized,including their susceptibility profiles, molecular typing, phylogenetic features, and genetic context analysis of carbapenemase-encoding genes. Of the 2569 BSI Enterobacterales isolates enrolled, 42(1.6%) were carbapenemase-positive. Moreover, among the 2242 investigated isolates, 1111(49.6%) extendedspectrum β-lactamase(ESBL)-producing isolates were identified in Escherichia coli(E. coli), Klebsiella pneumoniae(K. pneumoniae), Proteus mirabilis(P. mirabilis), and Klebsiella oxytoca. Whole genome sequencing analysis showed the clonal spread of K. pneumoniae carbapenemase(KPC)-2-producing K. pneumoniae sequence type(ST) 11 and New Delhi metallo-β-lactamase(NDM)-5-producing E. coli ST167 in our collection. Plasmid analysis revealed that carbapenemase-encoding genes were located on multiple plasmids. A high prevalence of biofilm-encoding type 3 fimbriae clusters and yesiniabactin-associated genes was observed in K. pneumoniae isolates. This work demonstrates the high prevalence of ESBLs and the wide dissemination of CPE among BSI isolates in China, which represent real clinical threats. Moreover, our findings first illustrate a more comprehensive genome scenario of CPE isolates among BSIs. The clonal spread of KPC-2-producing K. pneumoniae ST11 and NDM-5-producing E. coli ST167 needs to be closely monitored. | Beiwen Zheng Hao Xu Lihua Guo Xiao Yu Jinru Ji Chaoqun Ying Yunbo Chen Ping Shen Huiming Han Chen Huang Shuntian Zhang Tao Lv Yonghong Xiao | 2022 | Engineering2022，8，5： | 2 |
| 14 | Interleukin-8-251A/T polymorphism and Helicobacter pylori infection influence risk for the development of gastric cardiac adenocarcinoma in a high-incidence area of China显示文摘 | Liwei Zhang Chaoqun Du Xiaoqing Guo Li Yuan Weiwei Niu Weifang Yu Limian Er Shijie Wang | 2010 | Molecular Biology Reports2010，，8： | 1 |
| 15 | Chloro-free synthesis of LiPF_(6)using the fluorine-oxygen exchange technique显示文摘A hydrogen fluoride-free and chloro-free method for synthesizing LiPF_(6) was developed.Employing CaF_(2) as the direct fluorinating reagent instead of hydrogen fluoride made it much safer and more environmentfriendly than conventional methods and reduced the metal residues in product owing to the relatively low-acid reaction conditions less corrosive to equipments.The use of P_(2)O_(5) as phosphorus source instead of traditionally employed PCl_(5) significantly reduced the chloro residue in product.Ca(H_(2)PO_(4))_(2),the only by-product of the process,could be easily converted into Ca_(3)(PO_(4))_(2),a best-selling chemical.The above advantages not only reduce the production costs by ca.20%,but also significantly improve the product purity.The fluorine-oxygen exchange reaction is a completely new technique for LiPF_(6) production and may bring about technological revolution in the related industry. | Jian Liu Yuanli Cai Huan Pang Bin Cao Chengzhi Luo Zhenghao Hu Chaoqun Xiao Hu Zhang Fulu Lv Yitao Cao Lei Yu | 2022 | Chinese Chemical Letters2022，33，8： | 1 |
| 16 | Experimental Study on the Dynamic Characteristics of a Gas Turbine Combustor Burning Syn-gas显示文摘The present study focused on the development of a full-scale gas turbine combustor burning syn-gas from the coal-based multi-production. The dynamic features of a variety of parameters of the combustor, such as temperature and pressure during the procedures of startup and thermal load shifting, were measured and analyzed. The frequency and power spectrum of pressure fluctuation were analyzed by applying FFT and 1D continuous MORLET wavelet methods. The results show that the pressure fluctuation has distinct patterns during startup and load-transition procedures. The relationship between these dynamic features and the stability, safety and efficiency of gas turbine combustors burning syn-gas are preliminarily discussed. | Yu Lei Gang Xu Aibing Fang Chaoqun Nie Weiguang Huang | 2004 | Journal of Thermal Science2004，13，4： | 0 |
| 17 | Using Grey Target Theory for Power Quality Evaluation Based on Power Quality Monitoring Data显示文摘Smart grid puts forward higher requirements for power quality.Power quality evaluation can provide a decision-making basis for quality improvement.Based on power quality monitoring data,a grey target method is proposed for power quality evaluation.The grey target is composed of power quality evaluation standard and power quality monitoring data to be evaluated.Combining with the characteristics of each power quality evaluation index,the target center of the whole grey target system is found.Then,the power quality monitoring data to be evaluated and the power quality standard mode are compared and analyzed to construct the power quality grey correlation difference information space.Finally,the target center coefficient and target degree of power quality are calculated to realize the comprehensive evaluation of power quality,and the evaluation grade of power quality monitoring data to be evaluated is obtained.Compared with the evaluation results of the existing literature,the effectiveness of the proposed method is verified,which shows that grey target theory is reasonable in the comprehensive evaluation of power quality. | Qiang Yu Xiankai Chen Xiaoyue Li Chaoqun Zhou Zhichao Li | 2022 | Energy Engineering2022，119，1： | 0 |
| 18 | Correction to: Stretching and shearing contamination analysis for Liutex and other vortex identification methods显示文摘Correction to:Adv Aerodyn 3,8(2021)http://gffzzd3cc09b8251d45dfs505wcbxqvoup69pu.ffgz.tsg.suse.edu.cn/10.1186/s42774-020-00060-9 After publication of this article[1],it is noticed letter‘a’is missing from the below sentence in section 6.2‘Adding stretching components’:The subscript“”means“adding”the stretching components.The correct sentence should be。 | Pushpa Shrestha Charles Nottage Yifei Yu Oscar Alvarez Chaoqun Liu | 2021 | Advances in Aerodynamics2021，3，1： | 0 |
| 19 | Construction and application of the polyelectrolyte-based sequential artificial light-harvesting system显示文摘In this work,we have designed and synthesized a cyano-substituted p-phenylenevinylene derivative(PPTA),which can self-assemble into positively charged nanoparticles in an aqueous solution with a deep green fluorescence.An anionic polyelectrolyte material guar gum modified by carboxylic acid(GP5A)was chosen to build an artificial light-harvesting system(LHS)through self-assembly with PPTA,in which two acceptors Eosin Y(EY)and Nile red(NiR)were loaded into the PPTA-GP5A assemblies through electrostatic interaction and Van der Waals force.By adjusting the molar ratio of PPTA-GP5A/EY at 1:0.004,the one-step artificial LHS can exhibit high energy transfer efficiency(Φ_(ET))(38.9%)and antenna effect(AE)(4.6).Subsequently,with the addition of NiR,theΦET and AE of the two-step sequential artificial LHS were calculated to be 71.9%and 13.5,respectively.Moreover,the two-step artificial LHS constructed by the polyelectrolyte material GP5A can be used as a nanoreactor to photocatalyst alkylation of C-H bonds of phenyl vinyl sulfone(PVS)and tetrahydrofuran(THF)in water with a yield of 42%.Therefore,we have constructed an artificial LHS with two-step energy transfer based on polyelectrolytes through the electrostatic interaction to improve energy transfer efficiency,which can also be used as a nanoreactor for photocatalysis. | Chaoqun Ma Ning Han Ying Wang Hui Liu Rongzhou Wang Shengsheng Yu Yuebo Wang Lingbao Xing | 2023 | Chinese Chemical Letters2023，34，8： | 0 |
| 20 | Trust evaluation model of power terminal based on equipment portrait显示文摘As the number of power terminals continues to increase and their usage becomes more widespread,the security of power systems is under great threat.In response to the lack of effective trust evaluation methods for terminals,we propose a trust evaluation model based on equipment portraits for power terminals.First,we propose an exception evaluation method based on the network flow order and evaluate anomalous terminals by monitoring the external characteristics of network traffic.Second,we propose an exception evaluation method based on syntax and semantics.The key fields of each message are extracted,and the frequency of keywords in the message is statistically analyzed to obtain the keyword frequency and time-slot threshold for evaluating the status of the terminal.Thus,by combining the network flow order,syntax,and semantic analysis,an equipment portrait can be constructed to guarantee security of the power network terminals.We then propose a trust evaluation method based on an equipment portrait to calculate the trust values in real time.Finally,the experimental results of terminal anomaly detection show that the proposed model has a higher detection rate and lower false detection rate,as well as a higher real-time performance,which is more suitable for power terminals. | Erxia Li Zilong Han Chaoqun Kang Tao Yu Yupeng Huang | 2023 | Global Energy Interconnection2023，6，6： | 0 |
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