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Objective Omega vortex identification method

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Journal of Hydrodynamics 2019年第3期31卷 455-463页

作者： Jian-ming Liu yi-sheng Gao yi-qian Wang Chaoqun Liu School of Mathematics and Statistics Jiangsu Normal University Xuzhou 221116 China Department of Mathematics University of Texas at Arlington Arlington 76019 Texas USA School of Aerospace Engineering Tsinghua University Beijing 100084 China

A new vortex identification method (Liu et al. 2016) was proposed to represent the rotation relative strength and capture and visualize the vortices in our previous study. The basic idea of the Ω method is that a ratio of the vorticity squared over the summation of the vorticity squared and the deformation squared should be used to measure the relative rotation strength. However, the vorticity tensor norm is not objective. Thus, a moving observer will observe different vortex structures in a moving reference frame, which will make confusions about the real vortex structures. In the present study, by the definitions of the net spin tensor and the net vorticity vector, an objective Ω vortex identification method is presented with examples to verify that the vortex structures retain in a moving reference frame.

关键词： Vortex identification the Ω method objectivity turbulence visualization turbulence

Fishing Ground Distribution of Neon Flying Squid (Ommastrephes bartramii) in Relation to Oceanographic Conditions in the Northwest Pacific Ocean

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Journal of Ocean University of China 2017年第6期16卷 1157-1166页

作者： YU Wei CHEN Xinjun yi qian College of Marine Sciences Shanghai Ocean University Shanghai 201306 P. R. China National Engineering Research Center for Oceanic Fisheries Shanghai Ocean University Shanghai 201306 P. R. China Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources Ministry of Education Shanghai Ocean University Shanghai 201306 P. R. China Collaborative Innovation Center for Distant-water Fisheries Shanghai Ocean University Shanghai 201306 P. R. China

Neon flying squid, Ommastrephes bartramii, is a squid species of the North Pacific Ocean, which plays an important economical role in the international fishery. Logbook data for Chinese squid-jigging fishery over 2004–2011 were used to evaluate the relationship between the fishing grounds of the squid and the convergent frontal areas, which were defined by the contour lines of specific sea surface temperature(SST) and chlorophyll-a(Chl-a) concentration. Our results indicate that the SST in the range of 15 to 19℃ and the Chl-a concentration in the range of 0.1 to 0.4 mg m^(-3) are the favorable conditions for the aggregation of the squid. Additionally, we deduced that the SST at 17.5℃ and the Chl-a concentration at 0.25 mg m^(-3) are the optimal environmental conditions for the aggregation of O. bartramii. In August, the annual CPUE is positively correlated with the proportion of the fishing grounds with favorable SST and Chl-a concentration, as well as the combination of the two variables, implying that the abundance of the squid annually is largely depending on the presence of the favorable environmental conditions for fishery in August. Minor spatial difference between mean latitudinal location of the 17.5℃ SST and 0.25 mg m^(-3) Chl-a fronts can increase the CPUEs of O. bartramii. Furthermore, the monthly latitudinal gravity centers of the CPUE closely followed the mean latitudinal position of the contour lines of the 17.5℃ SST and the 0.25 mg m^(-3) Chl-a concentration. Our findings suggest the convergent oceanographic features(fronts) play significant roles in regulating the distribution and abundance of the western stock of the winter-spring cohort of O. bartramii, which can help people to improve their ability to discover the O. bartramii fishing grounds with higher productivity.

关键词： neon flying squid sea surface temperature chlorophyll-a oceanic fronts fishing ground the Northwest Pacific Ocean

Liutex-based vortex dynamics:A preliminary study

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Journal of Hydrodynamics 2020年第6期32卷 1217-1220页

作者： Hai-dong Yu yi-qian Wang School of Aerospace Engineering Tsinghua UniversityBeijing100084China School of Mathematical Science Soochow UniversitySuzhou215006China

Vortex dynamics,with the possibility of efficient flow control,is explored in this study based on the new introduced vortex definition and identification system of *** the six core elements of vortex identification,including(1)absolute strength,(2)relative strength,(3)local rotational axis,(4)global rotational axis,(5)vortex core size and(6)vortex boundary,provided by the Liutex system,it is possible to numerically devise strategies,primarily by introducing additional source terms in Navier-Stokes equations,which we call Liutex force field model here,to control the vortex *** methodologies of centripetal force model and counter-rotation force model are preliminarily investigated in a cavitating flow around two-dimensional Clark-Y *** is found that Liutex based models are capable of illustrating the vortex dynamics and possibly strengthening or weakening the vortices.

关键词： Vortex dynamics Liutex vector flow control

The Stability of the Elliptic Equilibrium of Planar Quasi-periodic Hamiltonian Systems

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Acta Mathematica Sinica,English Series 2012年第4期28卷 801-816页

作者： Yun Chao WU yi qian WANG Department of Mathematics Nanjing University

In this paper, we study the planar Hamiltonian systemwhere where f is real analytic in x and θ,A（θ） is a 2×2real analytic symmetric matrix,J=（1^-1） and w is a Diophantine vector. Under the assumption that the unperturbed systemreducible and stable, we obtain a series of criteria for the stability and instability of the equilibrium of the perturbed system.

关键词： Lyapunov stability elliptic equilibrium Hamiltonian system quasi-periodic system

Boundedness of Solutions for a Class of Oscillating Potentials without the Twist Condition

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Acta Mathematica Sinica,English Series 2010年第12期26卷 2387-2398页

作者： Zhi Guo WANG yi qian WANG School of Mathematical Sciences Soochow University Suzhou 215006 P. R. China Department of Mathematics Nanjing University Nanjing 210093 P. R. China

In this paper, we prove that the second order differential equation d^2x/dt^2＋x^2n_1f（x）＋p（t）=0with p（t ＋ 1） = p（t）, f（x ＋ T） = f（x） smooth and f（x）〉 0, possesses Lagrangian stability despite of th... 详细信息

关键词： Boundedness of solutions oscillating potential twist condition KAM theorem

Enhancing Quantum Discord in Cavity QED by Applying Classical Driving Field

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Chinese Physics Letters 2012年第4期29卷 11-14页

作者： qian yi XU Jing-Bo Zhejiang Institute of Modern Physics and Physics Department Zhejiang UniversityHangzhou 310027

We investigate the quantum discord dynamics in a cavity quantum electrodynamics system,which consists of two noninteracting two-level atoms driven by independent optical fields and classical fields,and find that the quantum discord vanishes only asymptotically although entanglement disappears suddenly during the time evolution in the absence of classical *** is shown that the amount of quantum discord can be increased by adjusting the classical driving fields because the increasing degree of the amount of quantum mutual information is greater than classical correlation by applying the classical driving ***,the influence of the classical driving field on the fidelity of the system is also examined.

关键词： quantum system mutual

Quantum Discord Dynamics of Two Atoms Interacting with Two Quantized Field Modes through a Raman Interaction with Phase Decoherence

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Chinese Physics Letters 2011年第7期28卷 35-38页

作者： qian yi XU Jing-Bo Zhejiang Institute of Modern Physics and Department of Physics Zhejiang UniversityHangzhou 310027

We investigate the quantum discord dynamics of two effective two-level atoms independently interacting with two quantized field modes through a Raman interaction in the presence of phase *** influence of the phase decoherence and detuning on the evolution of the quantum discord and entanglement between two atoms is *** is found that the quantum discord is more robust than the entanglement under the phase decoherence,and the amount of discord and entanglement between two atoms can be increased by adjusting the detuning.

关键词： quantum independently phase

Response of winter cohort abundance of Japanese common squid Todarodes pacificus to the ENSO events

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Acta Oceanologica Sinica 2018年第6期37卷 61-71页

作者： YU Wei ZHANG Yang CHEN Xinjun yi qian qian Weiguo College of Marine Sciences Shanghai Ocean University Shanghai 201306 China State Key Laboratory of Satellite Ocean Environment Dynamics Second Institute of Oceanography State Oceanic Administration Hangzhou 310012 China National Engineering Research Center for Oceanic Fisheries Shanghai Ocean University Shanghai 201306 China Key Laboratory of Sustainable Exploitation of Oceanic Fisheries Resources of Ministry of Education Shanghai Ocean University Shanghai 201306 China Collaborative Innovation Center for Distant-water Fisheries Shanghai 201306 China

The Japanese common squid Todarodes pacificus is an economically important species with one year lifespan,which is significantly influenced by climatic and environmental variability. According to the fishery data of the winter cohort of T. pacificus from 2003 to 2012, as well as environmental data and the Oceanic Ni？o index（ONI,which was defined by the sea surface temperature（SST） anomaly in the Ni？o 3.4 region）, variations in the SST,chlorophyll a（Chl a） concentration, suitable spawning area（SSA） and sea surface height anomaly（SSHA） on the spawning ground of T. pacificus were examined under the El Ni？o and La Nina conditions. Their influences on squid abundance（defined by catch per unit effort, CPUE） were further assessed. The results showed that seasonal changes were found in SST, Chl a and SSA on the spawning ground of T. pacificus. Correlation analysis suggested that annual CPUE was significantly positively correlated with Chl a and SSA（p〈0.05）, but had insignificant relationship with SST（p〉0.05）. Moreover, the El Ni？o and La Ni？a events tended to dominate the changes of SSA and Chl a concentration in the key area between 25°–29°N and 122.5°–130.5°E, driving the variability of squid abundance. However, this influence varied with the intensity of each anomalous climatic event： the weak El Ni？o event occurred, the spawning ground was occupied by waters with enlarged SSA but with extremely low Chl a concentration, leading to low squid recruitment, the CPUE then decreased; the moderate intensity of El Ni？o event resulted in shrunk SSA but with high Chl a concentration on the spawning ground, the squid recruitment and CPUE increased; the moderate intensity of La Ni？a events yielded elevated SSA and high Chl a concentration on the spawning ground, the squid recruitment and CPUE dramatically increased. Our findings suggested that the ENSO events played crucial effects on the incubating and feeding conditions of the winter cohort of T. pacificus during the spawning seas

关键词： Todarodes pacificus squid abundance spawning ground El Nino La Nina

Diffusion of municipal wastewater treatment technologies in China： a collaboration network perspective

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Frontiers of Environmental Science & Engineering 2017年第1期11卷 111-121页

作者： Yang Li Lei Shi yi qian Jie Tang State Key Joint Laboratory of Environment Simulation and Pollution Control School of Environment Tsinghua University Beijing 100084 China Department of Computer Science and Technology Tsinghua University Beijing 100084 China

The diffusion of municipal wastewater treatment technology is vital for urban environment in developing countries. China has built more than 3000 municipal wastewater treatment plants in the past three decades, which is a good chance to understand how technologies diffused in reality. We used a data-driven approach to explore the relationship between the diffusion of wastewater treatment technologies and collaborations between organizations. A database of 3136 municipal wastewater treatment plants and 4634 collaborating organizations was built and transformed into networks for analysis. We have found that： 1）.the diffusion. networks are assortative, arid the .pattems of diffusion vary across technologies; while the collaboration networks are fragmented, and have an assortativity around zero since the 2000s. 2） Important projects in technology diffusion usually involve central organizations in collaboration networks, but organizations become more central in collaboration by doing circumstantial projects in diffusion. 3）The importance of projects in diffusion can be predicted with a Random Forest-model at a good accuracy and precision level. Our findings provide a quantitative understanding of the technology diffusion processes, which could be used for waterrelevant policy-making and business decisions.

关键词： Innovation diffusion Collaboration network Wastewater treatment plant Complex network Data driven