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Rare Metals 2021年第5期40卷 1232-1238页

作者： tian-chi ji Min-Xiang Pan Hong-Liang Ge Qiong Wu Peng-Yue Zhang Magnetism Key Laboratory of Zhejiang Province China Jiliang UniversityHangzhou 310018China

In the present work,the magnetization reversal behavior for the melt spinning(Nd_(0.8)Ce_(0.2))_(2)Fe_(12)Co_(2-x)Zr_(x)B(x=0,0.5)permanent alloys with high coercivity was investigated by analyzing the hysteresis curves and the recoil *** to the Zr-free alloy,the Zr-doped sample obtains higher magnetic properties:coercivity of H_(cj)=650.5 kA·m^(-1),squareness of H_(k)/H_(cj)=0.76 and maximum energy product of(BH)_(max)=131.0 kJ·m^(-3).The first-order reversal curves(FORCs)analysis was taken to identify optimal conditions of exchange coupling for the Zr-free and Zr-doped *** coercivity mechanism of theα-Fe/Nd_(2)Fe_(14)B nanocomposite alloys was analyzed by the angular dependence of the coercive field as measured for the Zr-doped *** results show that the magnetic reverse process of the Zr-doped sample can be explained by the pinning model.

关键词： Magnetization reversal Coercivity mechanism First-order reversal curve(FORC) Nanocomposite

Determination of the shedding frequency of cavitation cloud in a submerged cavitation jet based on high-speed photography images

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Journal of Hydrodynamics 2021年第1期33卷 127-139页

作者： chi Peng Shou-ceng tian Gen-sheng Li State Key Laboratory of Petroleum Resources and Prospecting China University of Petroleum(Beijing)Beijing 102249China

To accurately determine the shedding frequency of the cavitation cloud in a submerged cavitation jet,the spectral analysis and the proper orthogonal decomposition(POD)for high-speed photography images are *** spectrums of 6 different kinds of image signals(the area-averaged gray level,the line-averaged gray level,the point gray level,the cavitation length,width,and area)are calculated and *** line-averaged gray level is found to be optimal in determining the shedding frequency but an accurate frequency can only be obtained in the stable-frequency zone where the cavitation cloud *** repeated experiments,the plateau-shape distribution of the main frequency is established with a deviation of 10.8%.A revised Reynolds number Re'is defined and the shedding frequency can be correlated to Re'by a power law when the cavitation number is less than *** relationship is validated by the experimental data in *** first mode of the POD characterizes the ensemble-average of the cavitation cloud while the second mode is the major part of the cavitation cloud transient *** modes 2-5 are organized in pairs,which confirms the periodic feature of the cavitation cloud in the submerged cavitation *** the nozzle exit,the modes 2-5 are symmetrically distributed in the jet shear *** shedding frequency of the cloud cavitation can also be precisely determined by performing the spectral analysis of the weighting coefficients of the mode *** paper shows that the two parameters,namely,the line-averaged gray level and the weighting coefficients of the mode 2,can be confidently used to calculate the shedding frequency of the cavitation cloud in a submerged cavitation jet.

关键词： Cavitation jet shedding frequency high-speed photography spectral analysis proper orthogonal decomposition(POD)

Resonant Heating of Ions by Parallel Propagating Alfvén Waves in Solar Coronal Holes

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chinese Journal of Astronomy and Astrophysics 2005年第3期5卷 285-294页

作者： tian-XiZhang jing-XiuWang chi-jieXiao NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012／／CenterforSpacePlasmaandAeronomicResearchTheUniversityofAlabamainHuntsvilleHuntsvilleAL35899USA NationalAstronomicalObservatories ChineseAcademyofSciencesBeijing100012

Resonant heating of H, O+5, and Mg+9 by parallel propagating ion cyclotron Alfven waves in solar coronal holes at a heliocentric distance is studied using the heating rate derived from the quasilinear theory. It is shown that the particle-AlfVen-wave interaction is a significant microscopic process. The temperatures of the ions are rapidly increased up to the observed order in only microseconds, which implies that simply inserting the quasilinear heating rate into the fluid/MHD energy equation to calculate the radial dependence of ion temperatures may cause errors as the time scales do not match. Different species ions are heated by Alfven waves with a power law spectrum in approximately a mass order. To heat O+5 over Mg+9 as measured by the Ultraviolet Coronagraph Spectrometer (UVCS) in the solar coronal hole at a region ≥ 1.9.R, the energy density of Alfven waves with a frequency close to the O+5-cyclotron frequency must be at least double of that at the Mg+9-cyclotron frequency. With an appropriate wave-energy spectrum, the heating of H, O+5 and Mg+9 can be consistent with the UVCS measurements in solar coronal holes at a heliocentric distance.

关键词： acceleration of particles - plasmas - waves - solar wind - Sun: corona

siRNA-mediated DNA methylation and H3K9 dimethylation in plants

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Protein & Cell 2013年第9期4卷 656-663页

作者： chi Xu jing tian Beixin Mo College of Life Science Shenzhen Key Laboratory of Microbial Genetic EngineeringShenzhen UniversityShenzhen 518060China College of Life Science Shenzhen Key Laboratory of Marine Biological Resources and Ecological EnvironmentShenzhen UniversityShenzhen 518060China

Heterochromatic siRNAs regulate transcriptional gene silencing by inducing DNA methylation and histone H3K9 *** advances have revealed the distinct phases involved in siRNA mediated silencing pathway,although the precise functions of a number of factors remain undesignated,putative mechanisms for the con-nection between DNA and histone methylation have been investigated,and much effort has been invested to understand the biological functions of siRNA-mediated epigenetic modifi *** this review,we summarize the mechanism of siRNA-mediated epigenetic modification,which involves the production of siRNA and the recruit-ments of DNA and histone methytransferases to the target sequences assisted by complementary pairing between 24-nt siRNAs and nascent scaffold RNAs,the roles of siRNA-mediated epigenetic modifi cation in maintaining genome stability and regulating gene expression have been dis-cussed,newly identified players of the siRNA mediated silencing pathway have also been introduced.

关键词： epigenetic DNA methylation histone meth-ylation heterochromatic siRNA argonaute

A novel method for identifying influential nodes in complex networks based on gravity model

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chinese Physics B 2022年第5期31卷 791-801页

作者： Yuan jiang Song-Qing Yang Yu-Wei Yan tian-chi Tong ji-Yang Dai School of Information Engineering Nanchang Hangkong UniversityNanchang 330063China School of Automation Nanjing University of TechnologyNanjing 210094China

How to identify influential nodes in complex networks is an essential issue in the study of network characteristics.A number of methods have been proposed to address this problem,but most of them focus on only one *** on the gravity model,a novel method is proposed for identifying influential nodes in terms of the local topology and the global *** method comprehensively examines the structural hole characteristics and K-shell centrality of nodes,replaces the shortest distance with a probabilistically motivated effective distance,and fully considers the influence of nodes and their neighbors from the aspect of *** eight real-world networks from different fields,the monotonicity index,susceptible-infected-recovered(SIR)model,and Kendall’s tau coefficient are used as evaluation criteria to evaluate the performance of the proposed method compared with several existing *** experimental results show that the proposed method is more efficient and accurate in identifying the influence of nodes and can significantly discriminate the influence of different nodes.

关键词： influential nodes gravity model structural hole K-shell

Improved space-time processing for X channel using precoders

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The Journal of china Universities of Posts and Telecommunications 2014年第5期21卷 31-36页

作者： tian Xin-ji LI Ya School of Computer Science and Technology Henan Polytechnic University

The article investigates how to send perfect space-time codes with low feedback amount and symbol-by-symbol decoding for X channel using precoders. It is assumed that two users are introduced with two antennas and two receivers. Each user employs a rate-2 space-time block code and follows certain rule when sending codewords. The multi-user interference is eliminated by pre-coding at the transmitter and linear processing at the receiver. Compared with the existing scheme for the same scene, the proposed scheme greatly reduces feedback amount and improves the transmission efficiency, while keeping the same decoding complexity. Simulations demonstrate the validity of the proposed scheme.

关键词： X channel space-time code pre-coding multi-user interference feedback amount transmission efficiency

Effect of Swirl Cup's Secondary Swirler on Flow Field and Ignition Performance

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Journal of Thermal Science 2015年第5期24卷 488-495页

作者： WANG Xiaofeng LIN Yuzhen ZHANG chi tian Xingpeng School of Energy and Power Engineering Beihang University

In a gas turbine engine combustor, highly swiding combustion is usually adopted to stabilize flame and reduce pollutant emissions. Swirl cup, as an air blast atomizer, is widely used to provide a uniform presentation of fuel droplets to the combustor dome. This paper investigated the effect of secondary swirler on the flow field down- stream of the swirl cup using particle image velocimetry （PIV）. Three swirl cups＇ non-reacting flow field were studied： case A, B and C with secondary swirler vane angle 53°, 60° and 68° respectively. Detailed mean and transient velocities and vorticity in the center plane were obtained. From the PIV results, a sharp contrast flow field was obtained for case A to other two cases due to the lower secondary swirling intensity. The recirculation zone is collapsed in disorder for the case A. Ignition tests of the three cups were completed in a single cup com- bustor. In general, the ignition performance increases with the increasing of the secondary swirling intensity. For case A, the ignition performance is very unstable and has much randomness and there is no clear lean ignition boundary can be generated. This work can further understand the swirl behavior and ignition mechanism.

关键词： Swirl cup swirl number ignition PIV

Quantum Phase Transition in Quasi-two-dimensional Heisenberg Antiferromagnet with Single-Ion Anisotropy

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Communications in Theoretical Physics 2007年第1期47卷 171-180页

作者： ji An-Chun tian Guang-Shan School of Physics Peking University Beijing 100871 China

In the present paper, we investigate the quantum phase transition in a spatially anisotropic antiferrornagnetic Heisenberg model of S =1 with single-ion energy anisotropy. By using the Schwinger boson representation, we calculate the Gaussian correction to the critical value J⊥^c caused by quantum spin fluctuations. We find that, for the positive single-ion energy, a nonzero value of J⊥^c is always needed to stabilize the antiferromagnetic long-range order in this model. It resolves a difference among literature and shows clearly that the effect of quantum fluctuations may qualitatively change a result obtained by the mean-field theories on lower-dimensional systems.

关键词： spatially anisotropic Heisenberg model single-ion anisotropy functional integration Schwinger-Boson representation

Effect of Quantum Fluctuation on Two-Dimensional Spatially Anisotropic Heisenberg Antiferromagnet with Integer Spin

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Communications in Theoretical Physics 2006年第6期45卷 1137-1146页

作者： ji An-Chun tian Guang-Shan School of Physics Peking University Beijing 100871 China

In the present paper, we calculate the Gaussian correction to the critical value J^c⊥ caused by quantum spin fluctuation in a two-dimensional spatially anisotropic Heisenberg antiferromagnet with integer spin S. Previously, some authors computed this quantity by the mean-field theory based on the Sehwinger boson representation of spin operators. However, for S = 1, their result is much less than the one derived by numerical calculations. By taking the effect of quantum spin fluctuation into consideration, we are able to produce a greatly improved result.

关键词： spatially anisotropic Heisenberg model functional integration Schwinger boson representation

Damage Spreading in Neural Network with Local Connection and Cycle Stored Patterns

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chinese Physics Letters 1996年第9期13卷 644-647页

作者： ji Dao-yun CHEN tian-lun Department of Physics Nankai UniversityTianjin 300071

The simulation results of damage spreading show the happening of dynamical chaotic-frozen phase transition in a one-dimensional system,a neural network with cycle stored patterns and local *** chaotic phase,the averag... 详细信息

关键词： behavior chaotic dynamical