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Effect of Crystallization and Entropy Contribution Upon the Mechanical Response of Polymer Nano-fibers:A Steered Molecular Dynamics Study

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Chinese Journal of Polymer Science 2023年第3期41卷 465-474,I0011页

作者： Rui Ma Dan Xu Chuan-fu luo Xinjiang Laboratory of Phase Transitions and Microstructures in Condensed Matters College of Physical Science and TechnologyYili Normal UniversityYining 835000China State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China School of Applied Chemistry and EngineeringHefei 230026China

The mechanical response of polyethylene nano-fibers with the same chain length but different chain numbers are studied by using steered molecular dynamics *** shrinking or stretching forces acted on the chain ends are investigated according to the chain-end distance and temperature under isothermal or continuous warming-cooling conditions,*** inflection point is found in the ForceDistance response when temperature is below 500 *** inflection point is related to the balance between entropy force and inter-monomer interaction and it reflects the strong effect of crystallization on the mechanical response of the *** force at inflection point is also affected by the buckling effect due to increased stiffness when crystallization *** two stages found in the Force-Temperature response and the difference between the shrinking and stretching forces indicate the hysteresis of crystallization and *** forces at different shrinking and stretching rates reveal the entropy contribution upon the mechanical response,indicated by the Ramachandran plot of *** chain-conformation entropy is majorly contributed by dihedrals and is quantified by the information entropy of dihedrals,which has a highly similarity to the mechanical Force-Temperature *** enlarged forces in multiple chains over a single chain are attributed to the enhanced dihedral-conformation *** study provides a new insight to the dynamically mechanical response of polymer nano-fibers according to the effect of crystallization and entropy contribution.

关键词： Polymer fibers Crystallization Entropy contribution Mechanical response

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Mars orbit insertion via ballistic capture and aerobraking

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Astrodynamics 2021年第2期5卷 167-181页

作者： Zong-fu luo Francesco Topputo School of Astronomy and Space Science Nanjing UniversityNanjing210023China School of Systems Science and Engineering Sun Yat-sen UniversityGuangzhou510006China Department of Aerospace Science and Technology Politecnico di MilanoMilano20156Italy

A novel Mars orbit insertion strategy that combines ballistic capture and aerobraking is *** ballistic capture orbits that neglect the aerodynamics are first generated,and are distilled from properly computed stable and unstable sets by using a pre-established method.A small periapsis maneuver is implemented at the first close encounter to better submit a post-capture orbit to the aerobraking *** adhoc patching point marks the transition from ballistic capture to aerobraking,from which an exponential model simulating the Martian atmosphere and a box-wing satellite configuration are considered.A series of apoapsis trim maneuvers are then computed by targeting a prescribed pericenter dynamic *** aerobraking duration is then estimated using a simplified two-body *** angle tuning cancels the inclination deflections owing to out-of-plane perturbation from the Sun.A philosophy combining in-plane and out-of-plane dynamics is proposed to simultaneously achieve the required semi-major axis and *** simulations indicate that the developed method is more efficient in terms of the fuel consumption,insertion safety,and flexibility when compared with other state-of-the-art insertion strategies.

关键词： ballistic capture aerobraking Mars orbit insertion

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Shape Accuracy and Residual Stress Distribution of Nano-molded Semicrystalline Polymer:A Simulation Study

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Chinese Journal of Polymer Science 2022年第6期40卷 642-650页

作者： Dan Xu Yu-Yuan Lu Chuan-fu luo State Key Laboratory of Polymer Physics and Chemistry Changchun Institute of Applied ChemistryChinese Academy of SciencesChangchun 130022China University of Science and Technology of China School of Applied Chemistry and EngineeringHefei 230026China

The shape accuracy and residual stress distribution of a nano-molded semicrystalline polymer are studied by molecular dynamics *** polyethylene flakes are obtained by continuous cooling inside templates with four *** find that the curvature of contour curve near template corners decreases with corner angle.A simple 2D shape model of minimum surface energy is proposed to understand the shapes for repulsive and attractive *** confinement of template induces highly ordered chain packing in surface *** to the spacial distribution of local stress,we find the contracting stress caused by volume shrinkage during cooling concentrates on the chains perpendicular to the direction of relative stress *** distribution of von Mises stress indicates the outer layer of semicrystalline polymer flake has lower *** results provide a theoretical insight for better nano-molding techniques.

关键词： Polymer semi-crystallization Molecular dynamics simulation Template

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Convergence of the Cesaro Mean for Rational Orthonormal Bases

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Acta Mathematica Sinica,English Series 2009年第4期25卷 581-592页

作者： Ying Xiong fu luo Qing LI Key Laboratory of Applied Mathematics Hubei ProvinceFaculty of Mathematics and Computer Science Hubei UniversityWuhan 430062 P. R. China

This paper deals with the convergence of the Cesaro mean for the rational orthonormal bases. Provided the set of zeroes of rational orthonormal bases is formed by a periodic repetition of the same finite sequence, the explicit expression of so-called block-Fejer kernel is available, and some properties of the block-Fejer kernel are discussed. Based on the convergence of the block-Cesaro mean, the convergence of Cesaro mean is also provided.

关键词： Cesaro mean trigonometric series rational orthonormal basis

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Method of analyzing vibration characteristics of armature system of hermetically sealed electromagnetic relay

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Journal of Zhejiang University-Science A(Applied Physics & Engineering) 2007年第3期8卷 434-438页

作者： REN Wan-bin CUI Li luo fu-biao ZHAI Guo-fu School of Electrical Engineering and Automation Harbin Institute qf Technology Harbin 150001 China Guilin Aerospace Electronics Company Guilin 541002 China

Published research is minimal on vibration characteristics of hermetically sealed electromagnetic relay (EMR) ex- posed to mechanical environment. The vibration characteristics of armature system, link contact system with electromagnetic system will cause EMR malfunction. The nonlinear dynamics model of armature systems was studied by considering electro- magnetic attraction force and opposite mechanical force in this paper. Angular displacements of armature under different sinu- soidal vibration conditions are solved in order to obtain the failure mode result from armature system. Vibration tests showed the presented analyzing method is suitable for EMR. The conclusions are instructive for increasing vibration resistance of armature systems of EMR, and are significant for reliability design of switch apparatus.

关键词： Hermetically sealed electromagnetic relay (EMR) Armature system Vibration characteristics Analyzing method

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Blended skip entry guidance for low-lifting lunar return vehicles

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Acta Mechanica Sinica 2014年第6期30卷 973-982页

作者： Zong-fu luo Hong-Bo Zhang Guo-Jian Tang College of Aerospace Science and Engineering National University of Defense Technology

A skip entry guidance algorithm blending numerical predictor-corrector and nominal trajectory tracking is presented for lunar return *** guidance is decoupled into longitudinal and lateral channels.A piecewise bank-vs-energy magnitude profile and a sign profile are adopted in the skip phase.A magnitude parameter is used to adjust the predicted downrange,and a pseudo-crossrange at the beginning of the final phase is selected as the lateral control *** biases of both channels are nullified by a false position iteration *** on-line estimation and modeling method is introduced to compensate for aerodynamic and atmospheric uncertainties.A nominal trajectory for the final phase is generated based on actual reenter conditions,and the obtained nominal trajectory is tracked by a linear feedback law.A lateral corridor is used to manage the lateral *** proposed guidance algorithm is assessed using three-degree-of-freedom Monte Carlo analyses,and the results show a satisfactory and robust performance under highly stressful dispersions.

关键词： Skip entry guidance Numerical predictorcorrector Low-lifting vehicle Lunar return mission Bank profile

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A Posterior Error Analysis for the Nonconforming Discretization of Stokes Eigenvalue Problem

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Acta Mathematica Sinica,English Series 2014年第6期30卷 949-967页

作者： Shang Hui JIA fu Sheng luo He Hu XIE School of Statistic and Mathematics Central University of Finance and Economics The Third Institute of Oceanography SOA LSEC Academy of Mathematics and Systems Science Chinese Academy of Sciences

In this paper, we present a posteriori error estimator for the nonconforming finite element approximation, including using Crouzeix–Raviart element and extended Crouzeix–Raviart element, of the Stokes eigenvalue problem. With the technique of Helmholtz decomposition, we first give out a posteriori error estimator and prove it as the global upper bound and local lower bound of the approximation error. Then, by deleting a jump term in the indicator, another simpler but equivalent indicator is obtained. Some numerical experiments are provided to verify our analysis.

关键词： A posteriori error estimate adaptive finite element method nonconforming Stokes eigen-value problem

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Numerical Simulation of Tip Clearance Flow Passive Control in Axial Turbine

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Journal of Thermal Science 2008年第2期17卷 147-155页

作者： LI Wei QIAO Wei-yang XU Kai-fu luo Hua-ling College of Propulsion and EnergyNorthwestern Polytechnical University Xi＇an 710072 China

This paper focuses on the effects of five different passive turbine tip clearance flow control methods on the tip clearance flow physics, which consists of a partial suction side squealer tip, a double squealer tip, a pressure side tip shelf with inclined squealer tip on a double squealer tip, a tip platform extension edge in pressure side and in suction side respectively. A pressure-correction based, 3D Reynolds-averaged Navier-Stokes equations CFD code with Reynolds Stress Model was adopted. The variable specific heat was considered. The detailed tip clearance flow field with different squealer rims was described with the streamline and the velocity vector. Accordingly, the mechanisms of five passive controls were elucidated; the effects of the passive controls on turbine efficiency and tip clearance flow field were illuminated. The results showed that the secondary flow loss near the outer casing including the tip leakage losses and the passage vortex losses could be reduced in all the five passive control methods. The turbine efficiency could be increased via the rational passive turbine tip clearance flow control. The Improved PS Squealer had the best effect on turbine efficiency, and the efficiency increased by 0.215%.

关键词： contact face wave receiving tube absorber

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Impact of Local Climate Zones on the Urban Heat and Dry Islands in Beijing:Spatial Heterogeneity and Relative Contributions

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Journal of Meteorological Research 2024年第1期38卷 126-137页

作者： Zuofang ZHENG fu luo Nana LI Hua GAO Yuanjian YANG Institute of Urban Meteorology China Meteorological AdministrationBeijing 100089 School of Atmospheric Physics Nanjing University of Information Science&TechnologyNanjing 210044 Key Laboratory of Urban Meteorology China Meteorological AdministrationBeijing 100089

Based on the building height and density data on a 100-m resolution,hourly 2-m temperature and humidity data at83 automatic weather stations,and gridded local climate zone(LCZ)data on a 120-m resolution in urban Beijing in2020,this study first employs the semivariogram combined with building parameters to calculate spatial correlations and has identified an LCZ grid resolution of 500 m suitable for best usage of the available observation ***,how the spatially heterogeneous LCZs affect and contribute to the canopy urban heat island intensity(UHII)and urban dry island intensity(UDII)are quantitatively *** is found that UHII is high in winter and low in summer with a unimodal diurnal variation while UDI is low in winter but high in summer with a bimodal diurnal *** LCZ with compact mid-rise(open high-rise)buildings exhibits the highest UHII(UDII),followed by the compact high-rise(compact low-rise),while the LCZ of scattered trees presents both the lowest UHII and the lowest *** most significant difference in the UHII(UDII)among the nine LCZ types in the urban area of Beijing is2.62℃(1.1 g kg^(-1)).Area-weighted averaging analysis reveals that the open mid-rise LCZ is the most significant contributor to the UHII(UDII),immediately followed by compact mid-rise(open low-rise),with the least contribution from bare rock or paved(scattered trees).The results also indicate that beyond the intrinsic physical properties of the LCZs of a city,their area proportions cannot be overlooked in evaluating their impact on the UHI and *** quantitatively findings could help urban planners to create a livable urban climate and environment by adjusting the relevant land use.

关键词： local climate zone(LCZ) urban heat island(UHI) urban dry island(UDI) distribution pattern contribution rate Beijing

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Diffusion of a Ring Threaded on a Linear Chain

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Chinese Journal of Polymer Science 2020年第12期38卷 1409-1417页

作者： Zhen-Hua Wang Yu-Yuan Lu Hui Jin Chuan-fu luo Li-Jia An State KeyLaboratory of Polymer Physics and Chemistry Changchun Istitute ofpplied Chemistry Chinese Academy of SciencesChangchun 130022 China University ofScience and Technology of China Hefei 230026China Changchun Istitute of Optics Fine Mechanics and PhysisChinese Acadermy of SciencesChangchun 130033China

A mesoscopic simulation is applied to investigate the effects of hydrodynamic interactions and axial chains on the dynamics of threaded *** hydrodynamic interactions significantly speed up the diffusion and relaxation of both free and threaded *** decoupled diffusion and relaxation dynamics indicate the broken of the Einstein-Stokes *** diffusion of a ring threaded on a flexible chain exhibits a synergism effect compared to that on an axial rod,which originates from the self-diffusion of the ring and the reptation-like motion of the axial ***,hydrodynamic interactions significantly improve the synergism effect,leading to an enhanced sliding motion of the threaded *** faster sliding of threaded rings suggests that the entropic barrier is negligible,which agrees well with the basic assumption of barrier-less confining tube at equilibrium in tube *** results provide a new perspective on analysis of the effects of topology constraints on polymer dynamics.

关键词： Hydrodynamic interactions Threaded ring Sliding dynamics Diffusion and relaxation

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