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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

Morphology, crystal structure and hydration of calcined and modified anhydrite

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International Journal of Minerals,Metallurgy and Materials 2014年第10期21卷 1028-1032页

作者： Xiao-qing Niu ji-chun Chen School of Urban Construction Huazhong University of Science and Technology Wuchang Branch

The effects of calcination and modification on the morphology （shapes and textures） and crystal structure of anhydrite powders were studied. The results show that, calcination at 100℃ causes anhydrite to disintegrate into smaller crystals, accompanied by a slight in- crease in d-spacing. Without calcination and modification, the solidification time and curing time of anhydrite are 15 and 77 h, respectively. After the treatment, however, the solidification time and curing time are shortened significantly to 9.5 and 14 rain, respectively. The com- pressive and flexural strengths of hydration products made from the treated anhydrite reach 10.2 and 2.0 MPa, respectively. The much shorter solidification and curing time make it possible to use anhydrite as a building and construction material.

关键词： anhydrite morphology crystal structure curing hydration calcination modification

Application of A Fully Nonlinear Higher-Order Element Method for Modelling Three-Dimensional Wave Entry of A Cone

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China Ocean Engineering 2021年第6期35卷 814-827页

作者： YUAN Dong-chuang CHENG Yong ji chun-yan School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China

Fully nonlinear water entry of a cone into waves with gravity effect has been analyzed based on a three-dimensional(3D)higher-order boundary method(HOBEM).The total velocity potential at the initial time is divided into the incident and scattering *** the subsequent time steps,the solution of the velocity potential is defined as a whole through instantaneous boundary *** on the image theory,a modified Green function is applied to establish the integral equations so that only half of the calculation domain is considered and the seabed can be *** free surface elevation is tracked along a given azimuth plane in the polar coordinate system,while the horizontal motion of the water particle is updated by using a segment-spring analogy method,which redistributes nodes and maintains mesh connectivity according to linear *** auxiliary function is applied to solve the pressure distribution,instead of directly calculating time derivative of the velocity *** high accuracy of the present numerical method is achieved through a detailed convergence study and comparison with results in the *** are emphatically performed to examine the effects of gravity,wave nonlinearity,entry location,and oblique entry.

关键词： wave entry HOBEM time-domain simulation Green function segment-spring analogy method

Time-Domain Nonlinear Wave-Current Interaction with A Steep Wave Riser Considering Internal Flow Effect

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China Ocean Engineering 2021年第3期35卷 410-421页

作者： TANG Lian-yang CHENG Yong ji chun-yan School of naval architecture and ocean engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Nippon Kaiji Kyokai(China)Co. LtdShanghai 200336China

The nonlinear dynamic response induced by the wave-current interaction on a deepwater steep wave riser(SWR)is numerically investigated based on a three-dimensional(3 D)time-domain finite element method(FEM).The governing equation considering internal flow is established in the global coordinate *** whole SWR consists of three segments:the decline segment,buoyancy segment and hang-off segment,in which the buoyancy segment is wrapped by several buoyancy modules in the middle section,leading to the arch bend and sag bend.A Newmark-β iterative scheme is adopted for the accurate analysis to solve the governing equation and update the dynamic response at each time *** proposed method is verified through the published results for the dynamic response of steel catenary riser(SCR)and static configuration of steel lazy wave riser(SLWR).Simulations are executed to study the influence of wave height,current velocity/direction,internal flow density/velocity and top-end pressure on the tension,configuration and bending moment of the *** results indicate that the influence of the current on the configuration and mechanical behavior of the SWR is greater than that of the wave,especially in the middle *** increasing current velocity,the suspending height of the middle section drops,meanwhile,its bending moment decreases accordingly,but the tension increases *** a fixed external load,the increasing internal flow density induces the amplification of the tension at the hang-off segment and the mitigation at the decline segment,while the opposite trend occurs at the bending moment.

关键词： steep wave riser(SWR) nonlinear dynamic response wave-current interaction time-domain finite element method(FEM)

Nonlinear Analysis of Bidirectional Vortex-Induced Vibration of A Deepwater Steep Wave Riser Subjected to Oblique Currents

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China Ocean Engineering 2021年第6期35卷 852-865页

作者： CHENG Yong TANG Lian-yang ji chun-yan School of Naval Architecture and Ocean Engineering Jiangsu University of Science and TechnologyZhenjiang 212003China Nippon Kaiji Kyokai(China)Co. LtdShanghai 200336China

An improved three-dimensional(3D)time-domain couple model is established in this paper to simulate the bidirectional vortex-induced vibration(VIV)of a deepwater steep wave riser(SWR)subjected to oblique *** this model,the nonlinear motion equations of the riser are established in the global coordinate system based on the slender rod theory with the finite element *** der Pol equations are used to describe the lift forces induced by the x-and y-direction current components,*** coupled equations at each time step are solved by a Newmark-βiterative scheme for the SWR *** present model is verified by comparison with the published experimental results for a top-tension ***,a series of simulations are executed to determine the influences of the oblique angle/velocity of the current,different top-end positions and the length of the buoyancy segment on the VIV displacement,oscillating frequency as well as hydrodynamic coefficients of the *** results demonstrate that there exists a coupled resonant VIV corresponding to x-direction and y-direction,***,the effective frequency is almost identical between the vibrations at the hang-off segment along x and y *** addition of the buoyancy modules in the middle of the SWR has a beneficial impact on the lift force of three segments and simultaneously limits the VIV response,especially at the decline segment and the hang-off ***,the incident current direction significantly affects the motion trajectory of the SWR which mainly includes the fusiform and rectangle shapes.

关键词： steep wave riser(SWR) bidirectional vortex-induced vibration wake oscillator model time-domain finite element method(TDFEM)

Application of ensemble H-infinity filter in aquifer characterization andcomparison to ensemble Kalman filter

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Water Science and Engineering 2017年第1期10卷 25-35页

作者： Tong-chao Nan ji-chun Wu State Key Laboratory of Pollution Control and Resources Reuse Nanjing UniversityNanjing 210093China Department of Hydrosciences School of Earth Sciences and EngineeringNanjing UniversityNanjing 210093China

Though the ensemble Kalman filter （EnKF） has been successfully applied in many areas, it requires explicit and accurate model and measurement error information, leading to difficulties in practice when only limited information on error mechanisms of observational in-struments for subsurface systems is accessible. To handle the uncertain errors, we applied a robust data assimilation algorithm, the ensemble H-infinity filter （EnHF）, to estimation of aquifer hydraulic heads and conductivities in a flow model with uncertain/correlated observational errors. The impacts of spatial and temporal correlations in measurements were analyzed, and the performance of EnHF was compared with that of the EnKF. The results show that both EnHF and EnKF are able to estimate hydraulic conductivities properly when observations are free of error; EnHF can provide robust estimates of hydraulic conductivities even when no observational error information is provided. In contrast, the estimates of EnKF seem noticeably undermined because of correlated errors and inaccurate error statistics, and filter divergence was observed. It is concluded that EnHF is an efficient assimilation algorithm when observational errors are unknown or error statistics are inaccurate.

关键词： Data assimilation Hydraulic parameter estimation Ensemble H-Infinity filter Ensemble Kalman filter Hydraulic conductivity Robustness

On-demand data broadcast scheduling based on AHP and GRA methods in wireless broadcast/UMTS integrated systems

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The Journal of China Universities of Posts and Telecommunications 2007年第4期14卷 1-6页

作者： WANG Hui LI chun ji Yang Key Laboratory of Universal Wireless Communications Beijing University of Posts and Telecommunications)Ministry of Education Wireless Technology Innovation LaboratoryBeijing100876China

The increasing demand for interactive mobile multimedia service is causing the integration of 3rd generation （3G） cellular systems and wireless broadcast systems. The key challenge is to support data dissemination with low response time, request drop rate, and the unfairness of request drop. This article proposes a novel scheduling algorithm called DAG （on-demand scheduling utilizing analytic hierarchy process （AHP） and grey relational analysis （GRA））, which takes multiple factors--waiting time, number of active requests, deadline--into consideration, and models the data scheduling process as a multiple factors＇ decision-making and best option-selecting process. The proposed approach comprises two parts. The first part applies AHP to decide the relative weights of multiple decision factors according to user requests, while the second adopts GRA to rank the data item alternatives through the similarity between each option and the ideal option. Simulation results are presented to demonstrate that DAG performs well in the multiple criterions mentioned above.

关键词： AHP DAG (on-demand scheduling utilizing AHPand GRA) GRA on-demand data broadcast scheduling

Direct Comparison of Crystal Nucleation Activity of PCL on Patterned Substrates

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Chinese Journal of Polymer Science 2019年第7期37卷 693-699页

作者： jian Hu Rui Xin chun-Yue Hou Shou-Ke Yan ji-chun Liu Key Laboratory of Rubber-Plastics Ministry of Education/Shandong Provincial Key Laboratory of Rubber-plastics Qingdao University of Science & Technology College of Chemical Engineering and Pharmaceutics Key Laboratory of Polymer Science and Nanotechonology Henan University of Science and Technology

A sample containing different regions with poly(ε-caprolactone)(PCL), oriented polyethylene (PE), and oriented isotactic polypropylene (iPP) films in contact with glass slide has been prepared to be observed in the same view field in an optical microscope and the crystallization of PCL in different regions during cooling from 80 °C down to room temperature at a rate of 1 °C·min^-1 was studied. The results showed that the crystallization of PCL started first at the PE surface and then at the iPP surface, while its bulk crystallization occured much later. This indicates that though both PE and iPP are active in nucleating PCL, the nucleation ability of PE is stronger than that of iPP. This was due to a better lattice matching between PCL and PE than that between PCL and iPP. Moreover, since lattice matching existed between every (hk0) lattice planes of both PCL and PE but only between the (100)PCL and (010)iPP lattice planes, the uniaxial orientation feature of the used PE and iPP films resulted in the existence of much more active nucleation sites of PCL on PE than on iPP. This led to the fact that the nucleation density of PCL at PE surface was so high that the crystallization of PCL at PE surface took place in a way like the film developing process with PCL microcrystallites happened everywhere with crystallization proceeding simultaneously. On the other hand, even though iPP also enhanced the nucleation density of PCL evidently, the crystallization of PCL at iPP surface included still a nucleation and crystal growth processes similar to that of its bulk crystallization.

关键词： Poly(ε-caprolactone) Polypropylene Polyethylene Epitaxy Heterogeneous nucleation

Superconducting Correlations in Small Metallic Grains

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Communications in Theoretical Physics 2001年第12期36卷 705-714页

作者： WANG jing ji An-chun TIAN Guang-Shan Department of Physics Peking University Beijing 100871 China Department of Physics Peking University Beijing 100871 China Department of Physics Peking University Beijing 100871 China

By applying the path-integral formulation and the Feynman theorem, we calculate the off-diagonal superconducting correlation in an ultrasmall metallic grain. Unlike its behavior in the bulk limit, we find that this correlation function is an intensive quantity in this case. Therefore, superconductivity is indeed completely suppressed by quantum fluctuations as the diameter of the grain shrinks to the nanometer scale. This conclusion confirms the previous results by numerical calculations. Furthermore, it also imposes a strong constraint on the delocalizing amplitude of the pair-mixing function, which was recently proposed to characterize superconductivity in the canonical *** numbers: ***, ***, 74.80.

关键词： ultrasmall superconducting grain, the off-diagonal correlation function, path integral formulation and resolvent expansion method